ronaldweinland.infoIKOV. ATLAS. OF. HUMAN. ANATOMY. IN THREE VOLUMES. Volume III. The Science of the Nervous System,. Sense Organs, and Endocrine. Sinelnikov - Atlas of Human Anatomy - Volume 3. Document Cover . DESCRIPTION. atlas anatomie sinelnikov. Transcript. Created with. R sinelnikov atlasanatomii pdf F. Grants Atlas pthw pdf of Anatomy PDF. Atlas of human.R. R.D. Sinelnikov, Atlas anatomii.
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T h e third part is retroperitoneal; the peritoneum covers its anterior and inferior surfaces and only the junction of the duodenum with the jejunum flexure is intraperitoneal. At the junction of the third and fourth parts the duodenum is crossed almost vertically by the superior mesenteric vessels artery and vein , and on ihe left, by the root of the mesentery radix mesenterii.
Posteriorly, the fourth part is in relation with the abdominal aorta. The upper border of the third part of the duodenum is re lated to the head and body of the pancreas.
The duodenojejunal flexure flexura duodenojejunalis is fixed in position by ihe suspensory muscle of the duodenum musculus suspensorius duodeni and a ligament. T h e muscle consists of smooth muscle fibres; it arises from the left cms of the diaphragm and is inserted into the muscular coat of the duodenum. T h e age features of the duodenum: It com mences at the duodenojejuna! The mesenterial intestine reaches 5 m in length and its diameter mea sures 4.
It is intraperitoneal, i. T h e mesentery' arises on the posterior wall of the abdominal cavity and is a fold duplicature of the peritoneum. Its free border surrounds ihe small intestine as if suspending it, while on the pos terior wall it is continuous with the parietal peritoneum. T h e site of origin of the mesentery from the posterior abdominal wall is an oblique line stretching downwards from left to right, from the root of the transverse mesocolon to the iieocaecal junction.
This line is the root of the mesentery radix mesenterii running from the second lumbar vertebra on the left to the sacro-iliac joint on the right. The blood and lymph vessels and the nerves of the small intes tine enter the root of the mesentery to pass between its layers. T h e regional mesenteric lymph glands nodi lymphatici mesenterici are also lodged in the duplicature between the peritoneal layers.
The root of the mesentery is cm long, while the free bor der is about 5 m long as a result of which the small intestine forms very many up to 16 coils, or loops see Fig.
T h e width of the mesentery is least at the beginning and end of the mesenteric part of the small intestine and greatest in its central portions.
This determines the degree of mobility and displacement of the intesti nal loops. According to some signs see below , two portions are distin guished in the mesenterial intestine: There is no distinct borderline between them.
T h e extreme distal part of I he ileuin is in turn distinguished its he terminal ileuin deum termmale. The loops of the small intestine are marked by a more or less definite position and direction: T h e last loops of the ileum, proximal to the terminal part, lie in the true pelvis as the result of which the terminal part is directed upwards and to the right as cends into the iliac fossa.
Besides, the intestinal loops lie in two layers: Two borders are distinguished in the mesenterial intestine: Vessels and nerves approach the intestinal wall in the region of the mesenteric border. The walls of the mesenterial intestine are composed of three coats: The serous coat of the small intestine tunica serosa intestini tenuis invests the intestine on all sides except for a narrow strip on the mesenteric border where both layers of the peritoneum sepa rate on approaching the intestinal wall.
The serous coat is connected to the underlying tissue of the muscular coat by an areolar subserous coat tcla subserosa. The muscular coat of the small intestine tunka muscularis intes tini tennis consists of two layers of smooth muscle fibres; an outer longitudinal layer stratum longitudinale and an inner circular layer stratum circulare.
The mucous coat, or membrane, of the small intestine tunica mucosa intestini tenuis is formed of an epithelial covering with un derlying lamina muscularis mucosae and a submucous coat tela submucosa.
T h e mucous membrane forms circular folds plicae cir culars Fig. The mucous coat of the mes enterial intestine differs in structure from that of the duodenum in that it has less circular folds, which gradually reduce in number from the jejunum to the ileum and almost completely disappear in the terminal ileum.
T h e total number of folds in the small intes tine ranges from to Their height also gradually dimin ishes from the beginning to the end of the small intestine. T h e villi in the mesenterial intestine are thinner and a little shorter than those in the duodenum.
T h e number of villi also re duces from the beginning to the end of the small intestine: At the junction of the ileum and the caecum the ileocolic orifice ostium ileocaecale , by means of which they communicate, is surrounded by a valve of the mucous membrane of the ileum. T h e valve is funnel-shaped and projects into the caecum; it is called the ileocolic valve valva ileocaecalis.
T h e submucous coat tela submucosa of the mesenterial intes tine contains solitary lymphatic nodules folliculi lymphatici solitarii which reach the surface of the mucous coat; these follicles are the size of a millet and their number comes to Besides, in this part of the small intestine, on the antimesenteric border, are found aggregated lymphatic nodules folliculi lymphatici aggregati Fig. T h e aggregates arc cm long, cm wide, and their number in the small intestine ranges from 30 to Topography of the mesenterial intestine.
T h e mesenterial in testine occupies the central part of the lower storey of the abdomi nal cavity below the transverse mesocolon. T h e small intestine is bounded by the ascending on the right , transverse above , and descending on the left colon. Anteriorly the intestinal loops are covered by the greater omentum as if by an apron descending from the greater curvature of the stomach and the inferior border of the transverse colon and separating the loops from the anterior abdominal wall.
Posteriorly, the intestinal loops are in relation with the parietal peritoneum covering to the right of the root of the mesentery the third part of the duodenum, the head of the pancreas, the lower end of the right kidney, the right ureter, the right psoas major muscle; to the left of the root the parietal perito neum covers the lower end of the left kidney, the left ureter, the left psoas major muscle, the abdominal aorta, the inferior vena cava, and the common iliac vessels.
O n the left and inferiorly the intestinal loops are related t o the pelvic colon a n d its mesentery. In the cavity of the true pelvis the intestinal loops are in rela tion with the urinary bladder anteriorly, the rectum posteriorly with the uterus and its appendages in females.
The terminal ileum crosses the right psoas major muscle and the right common iliac vessels. T h e age features of the mesenterial intestine: The relative. Large intestine radiograph. Contrast medium completely fills the caecum and partly other parts of the large intestine. Icaecum 2ascending colon 3 right flexure of colon 4transverse colon 5left flexure of colon 6 descending colon 7 pelvic colon.
T h e omentum covers the intestinal loops only partly in child ren under 7 years and completely by the age of 7. It consists of three parts: The colon in turn is separated into four parts: T h e total length of the large intestine varies from to cm. Its calibre is cm in the initial part caecum and 4 - 5 cm in the terminal part the distal segment of the descending colon.
T h e large intestine differs from the small intestine in posi tion, shape, and structure. T h e principal distinguishing signs of the large intestine are its larger calibre cm and the special arrangement of the muscu lar layersthe presence of muscular bands taeniae coli , sacculations, and projections called appendices epiploicae.
The longitudi nal muscle fibres of the large intestine except for the vermiform. Segment of the transverse colon. They are called taeniae coli and are arranged at an equal distance from one another.
Taenia libera, laenia mesocolica, and taenia onicnialis are distinguished. Their position on the cae cum and the different parts of the colon is described below. On the caecum the three taeniae converge to meet at the base of the vermiform appendix and surround it as a continuous mus cular layer. In a like manner they become wider as they reach the rectum and form a longitudinal muscular layer.
In the space between the taeniae the wall of the large intestine forms a succession of sacculations of the colon haustrae coli which are separated from one another by transverse grooves projecting into the cavity of the intestine as the semilunar folds of the colon plicae semilunares coli.
Masses of fat enclosed in folds of the perito neum, which are called appendices epiploicae, project from the grooves on the wall of the colon. They form two rows on the as cending, descending, and pelvic colon, one row on the transverse colon, and are absent on the caecum. In some cases adjacent ap pendices of one row fuse to form a single fold.
T h e large intestine differs from the small intestine also in co lour: Each part of the large intestine has its own characteristic fea tures and is distinguished by its relation to the peritoneum.
T h e caecum is intraperitoneal, it is completely invested by the peritoneum and is devoid of the mesentery. Developmental var iants are often encountered, with the caecum together with the as cending colon and the terminal ileum attached to a common ileocaecal mesentery.
The ascending colon is covered by the peritoneum on its anterior and lateral surfaces but not on the pos terior surface, i. T h e transverse colon is completely covered by the peritoneum, i.
T h e descending colon, like the ascending colon, is mesoperi toneal. The pelvic colon is intraperitoneal and possesses a mesen tery called the pelvic mesocolon mesocolon sigmoideum. T h e rectum is at first intraperitoneal and has a mesentery called the mesoreclum, more distally it is mesoperitoneal, and its terminal perineal part is extraperitoneal.
It has the shape of a blind pouch and is situated be low the junction of the ileum with the large intestine by analogy with the fundus of the stomach which is to the left of and above the cardiac portion. Its length varies in different individuals from 3 to 8 cm, its width ranges between 4 and 7 cm and it is the widest part of the large intestine except for the ampulla of the rectum. T h e caecum is usually completely covered by the peritoneum and is thus intraperitoneal, but may be mesoperitoneal in some cases, i.
The vermiform appendix appendix vermiformis Figs , arises from the posteromedial wall of the caecum 0. It is a narrow tube mm in diameter and 2. Its lumen communicates with the lumen of the caecum. The appendix has its own mesentery called the mesoappendix which connects it with the wall of the caecum and the terminal part of the ileum. This position, however, varies in different individuals: THE COLON The position of the colon Figs , in the cavity of the abdomen is such that it borders the coils of the small intestine ly ing in the middle of the lower storey.
T h e ascending colon is on the right, the transverse colon is above, the descending colon is on the left, and the pelvic colon is on the left and partly below. The ascending colon colon ascendens Figs , begins where the ileum empties into the large intestine and is a continua tion of the caecum.
It is separated from the caecum by two grooves which correspond to the frenula of the ileocolic valve sec Structure of the walls of the caecum and colon. T h e posterior surface of the as cending colon, which is devoid of peritoneum, lies on the posterior abdominal wall occupying an extreme lateral area on the right. The ascending colon commences slightly below the level of lite iliac crest, stretches vertically upwards, first in front of the quadratus lumborum muscle and then in front of the right kidney, and reaches the inferior surface of the right lobe of the liver; here it bends to the left and vcntrally forwards lo be continuous with the transverse colon; the bend is called the righl flexure of the colon flexura coli dextra.
It usually slopes more than the left flexure see below and is directed both in the frontal and sagittal planes, as a result of which the first part of the transverse colon lies closer to the surface than the ascending colon and in front of it the same applies to the left flexure.
T h e ascending colon is up to 20 cm long, but its position and length arc quite variable: T h e laenia coli are arranged on the. Caecum and vermiform appendix; posterior aspect Vj. The caecum and a segment of the ascending colon. The transverse colon colon transversum Figs begins in the right hypochondric region on the level of the tenth costal.
It passes obliquely from right to left and upwards into the left hypochondric region, where on the level of the ninth costal cartilage or eighth intercostal space it terminates at the left flexure of the colon flcxura coli sinistra to be continuous-with the descending colon. Just like on the. Caecum, vermiform appendix, and ascending colon; anterior aspect Vj. Part of the wall is removed. The middle portion of the transverse colon sags across the epigastric region so that the ascending and descending.
T h e transverse colon is about 50 cm long and is the longest part of the large intestine. It has its own mesentery called the transverse inesocolon mesocolon transversum which arises on the posterior abdominal wall from the parietal peritoneum. The line of attachment. The mesentery is cm wide in the middle part but grad ually becomes narrower towards the sides and comes to naught at the flexures. The mesentery is attached on the intestine along the taenia mesocolica which is a continuation of the taenia mesocolica of the ascending colon.
T h e gastrocolic ligament ligamentum gastrocolicum is attached to the anterior surface of the transverse colon along the continuation of the taenia omentalis. This perito neal ligament arises from the greater curvature of the stomach and the upper part of the duodenum, and after attachment to the tae nia omentalis of the transverse colon it continues downwards as the greater omentum omentum majus covering all the small intes tine the structure of the ligament and omentum is described be.
Due to this position of the greater omentum, the transverse colon, which is covered by it in front, cannot be seen at all or only through it when the abdomen is cut open Fig. T h e left flexure of the colon flexura coli sinistra lies in the left hypochondrium at a much higher level than the right flexure and dorsal to it deeper , i.
T h e left end of the transverse colon meets the initial part of the descending colon at an acute angle whose apex is held fast by the phrenicocolic ligament ligamentum phrcntcocolicum.
T h e descending colon colon descendens see Fig. II begins superiorly from the left splenic flexure and descends along the posterior abdominal wall; its posterior surface, which is devoid of peritoneum, is in front of the lateral area of the left kid ney and the quadratus lumborum muscle. At the level of the left il iac crest it is continuous with the next part of the large intestine, the pelvic colon.
The descending colon is further from the median plane of the abdomen than the ascending colon. It is also longer and measures up to Its calibre is lesser than the calibres of the above described parts of the large intestine and is 4 cm at the junction with the pelvic colon.
T h e number and depth of the sacculations diminish; the arrangement of the taeniae and the ap pendices epiploicae is the same as on the ascending colon.
T h e pelvic sigmoid colon colon sigmoideum Figs , , is the mcsenteric part of the large intestine which comes next after the descending colon. It lies in the left iliac fossa and begins superiorly and laterally at the level of the posterior border of the il iac crest.
After forming two loops it extends medially and down wards, curves over the arcuate line of the pelvis, and enters the cavity of the true pelvis where it is continuous with the rectum on the level of the third sacral vertebra. T h e length of the pelvic colon is 54 cm on the average, but is marked by considerable individual variations from 15 to 67 cm ; its calibre is about 4 cm. T h e pelvic colon forms two loops; one of them, the proximal one, lies on the iliacus muscle with the convexity directed down wards; the other, distal loop lies on the psoas major muscle and its convexity is directed upwards.
Part of the pelvic colon is below the arcuate line in the true pelvis and is continuous with the rectum. T h e mesentery of the pelvic colon is called the pelvic mesocolon mesocolon sigmoideum. Its calibre measures 12 cm but is variable along the length of the intestine. T h e root of the mesentery crosses the floor of the iliac fossa along a line descending obliquely from left to right.
The line of the root forms two angles corresponding to the two loops: T h e root of the pelvic meso colon runs across the iliacus and psoas muscles and the left com mon iliac vessels and left ureter which run along the arcuate line.
After bending over the arcuate line the root of the mesentery passes across the region of the left sacro-iliac joint to the anterior surface of the upper sacral vertebrae. At the level of the third sac ral vertebra the pelvic mesocolon terminates at the origin of the very short mesentery of the rectum mesorectum. T h e length of the root of the mesentery is greatly variable and determines the steepness and size of the loop of the pelvic colon.
Structure of the walls of the caecum and colon. Only the intraperitoneal parts of the large intestine arc completely formed of. T h e ascending and descending colon and, in some cases, also the caecum are covered by the peritoneum on three sur faces: T h e mesoperitoneal parts of the large intestine, namely the as cending and descending colon, have on their posterior wall an area a few centimetres wide which is devoid of the serous coat; the mesenteric parts of the large intestine, i.
The serous coat of the colon continues into the grooves on it. T h e muscular coat tunica muscularis forms two layers along the whole length of the large intestine: As it is pointed out above, the longitudinal layer is not continuous but for a considerable distance occurs in bands, or taeniae Figs , and is thinner than the circular layer.
T h e vermiform appendix, on which the taeniae converge, has an uninterrupted double-layer muscular coal which, however, is less developed than that in the other parts.
T h e mucous coat, or membrane tunica mucosa is composed of epithelium with an underlying basement membrane, a connectivetissue layer, and lamina muscularis mucosae under which is the submucous coat tela submucosa. T h e epithelium of the mucous membrane consists of columnar cells with very many goblet cells. T h e mucous coat of the large in testine contains intestinal glands glandulae intestinales but has no villi.
Along its whole distance there are solitary lymphatic nodules folliculi lympkatici solitarii. In line with the transverse grooves, the mucous membrane forms the semilunar folds of the colon plicae semilunares coli. At the junction of the ileum and the large intestine, at the ileocolic orifice ostium ileocaceale , there are two constantly present folds of the intestinal wall mostly composed of the circular muscu lar layer.
They form the ileocolic valve valva ileocaecalis Figs , T h e edges of the orifice are fused and continue as the frenulum of the ileocolic valve frenulum valvae ileocaecalis at the junc tion of the caecum and ascending colon.
T h e circular muscular layer is developed best in the base of the valve where it forms a sort of sphincter.
Where the lumen of the vermiform appendix communicates with the caecum is the opening of the vermiform appendix ostium appendicis vermiformis Fig. T h e mucous membrane of the vermiform appendix is rich in lymphoid tissue forming an almost continuous layer of lymphatic nodules of the vermiform appendix folliculi lympkatici aggregati appendicis vermiformis. It is in the cavity of the true pelvis and lies on its posterior wall which is formed by the sacrum, coccyx, and the posterior part of the muscles of the pelvic floor.
It begins from the end of the pelvic part of the pelvic colon at the level of the third sacral vertebra and termi nates by the anus in the region of the perineum see Figs , Its length varies from 14 to 18 cm.
Its calibre varies along its. Rectum radiograph. The rectum is composed of two parts: The second part is under the pelvic diaphragm in the peri nea region and is known as the anal canal canalis analis.
The pelvic part of the rectum forms a curve in the sagittal plane with the convexity directed posteriorly, corresponding to the curve of the sacral flexure flexura sacralisj; the upper part of the curve passes from front to back and downwards, the lower part passes from back to front and downwards.
There are also incon stant curves in the frontal plane, the upper part descending from left to right and the lower part passing in the opposite direction.
The second curve of the rectum in the sagittal plane is convex an. Af ter passing through the pelvic diaphragm the rectum bends sharply almost at a right angle to the back to form the perineal flexure jlexura perineatis. T h e rectum as if skirls the apex of the coccyx here. T h e length of the pelvic part varies from 10 to 14 cm, the pcrineal part is 4 cm long. The relation of the rectum to the peritoneum of the true pelvis varies at different levels see Figs , The pelvic part is covered by the peritoneum to a certain extent.
The perineal part is devoid of the peritoneal covering. T h e uppermost part supra-am pullar , beginning at the level of the third sacral vertebra, is com pletely enclosed in a serous coat and has a short, narrow, and thick mesentery see Fig.
Whether this pan of the mesentery should be related to the rectum is an arguable question. Many anatomists relate the whole mesenteric part to the pelvic colon. Already at the level of the inferior border of the third sacral. T h u s , the upper, supra-ampullar portion of the pelvic part is iiitraperiloneal, the upper portion of ihe ampulla is mesoperitoneal, and ihe lowest part of the ampulla is retroperilo-.
The line along which the peritoneum leaves the wall of the in testine descends obliquely from back to front. With the gradual loss of the peritoneal covering by the wall of the pelvic part of the. The perineal part of the rectum has the appearance of a longi tudinal slit and opens in a depression, in the anal gluteal cleft crena ani , by the anus almost in the middle of the distance be tween the coccyx and root of the scrotum in males or the posterior commissure of the labium majus in females, at the level of the transverse line connecting both ischial tuberosities.
T h e perineal part is cm long. Structure of the wall of the rectum. T h e serous coat perito neum tunica serosa is a component of the wall of the rectum only for a small distance, as it is mentioned above. T h e extraperitoneal portion of the pelvic part of the rectum is enclosed in the visceral layer of the pelvic fascia; the fascia is not in direct contact with the muscular coat of the rectal wall; between them lies a layer of fatty tissue and pass nerves, blood vessels supplying the rectum, and lymph glands nodi lymphatici anales.
T h e anterior part of the rectal fascia is a sheet separating the rectum from the organs lying anteri orly of it the urinary bladder, prostate, and others; see below. This sheet is a dei ivative of the fused serous layers of the deepest portion of the peritoneal pouch of the true pelvis; it stretches from the floor of the recto-uterine, or rectovaginal, pouch in females, and rectovesical pouch in males to the perineal body and is called the rectovaginal septum in females and rectovesical septum in males.
Dorsally, the rectal fascia terminates on the midline of the posterior wall of the rectum. T h e muscles of the circular layer of the rectum form thicken ings at the site of the transverse folds of the mucous membrane see below. T h e thickenings are most marked at a distance of cm from the anus where the distinct horizontal folds of the rectum plicae transversales recti occur; the middle one is most pro nounced and contains many circular muscle fibres.
T h e mucous coat membrane of the rectum tunica mucosa recti is covered with columnar epithelium and contains crypts with rectal glands glandulae intestinales but no villi; solitary lymphatic nodules are embedded in the submucous coat tela submucosa.
For the whole distance of the pelvic part of the rectum the mucous membrane forms three, sometimes more, horizontal folds of the rectum plicae transversales recti Fig.
T h e upper fold is 10 cm from the anus. In addition to the horizontal folds very many inconstant, variously di rected folds are found. The mucous membrane of the lower por tion of the rectum the anal canal forms up to 10 longitudinal folds which are called the anal columns columnae anales Fig. Distal to them is a slightly swollen anular area with a smooth surface of the mucous membrane, this is the transitional zone. T h e prominent trans itional zone as if closes inferiorly the pits between the columns and transforms them into pouches which are called the anal sinuses si nus anales.
T h e circumanal anal glands are embedded in the floor of the sinuses Figs A, B. T h e folds of the intermedi ate zone, which close the sinuses inferiorly, are called the anal valves valvulae anales. Distal to the transitional zone is the skin of the anus which gathers in radial folds. T h e submucous coat in the region of the columns and transitional zone is fonned of areolar tissue containing the submucous rectal venous plexus.
In the trans itional zone this plexus forms a complete ring; the submucous layer in the region of the columns contains, besides the venous plexuses, bundles of longitudinal muscle fibres. The muscular coat of the rectum tunica muscularis recti con sists of two layers: T h e longitudinal layer is a continuation of the taeniae of the pelvic colon which become wider here and invest the rectum completely.
The longitudinal muscle fibres are stronger on the anterior and posterior walls. Fibres of the rectococcygeal muscle musculus rectocoecygcus stretching from the anterior sacrococcygeal ligament are T h e mucous membrane in the region of the columns is lined interlaced posteriorly into the longitudinal muscular layer of the with nonkeratinized squamous epithelium, the mucous membrane lower portion of the ampulla.
Some of the muscle fibres of the lon of the sinuses, with columnar epithelium. T h e crypts of the mu gitudinal layer are interlaced into the levator ani muscle musculus cous membrane of the rectum spread only to the zone of the co levalor ani , others reach the skin. T h e mucous membrane of the transitional zone is lined with nonkeratinized stratified squamous epithelium which bears The circular muscular layer of the rectum extends to the anus papillae.
In front of the anus the fibres of its muscles interlace with the sphincter of the mem branous part of the urethra in males and with the vaginal muscles in females. The sphincter ani externus muscle musculus sphincter ani externus Figs , is in the subcutaneous fat surrounding the anus. It belongs to the group of perineal striated muscles. Its external part, lying closer to the surface, embraces the medial part of the levator ani muscle; the portion lying deeper adjoins the cir cular layer of the rectum which forms here the sphincter ani inter nus muscle.
A band of the levator ani muscle penetrates the space between the sphincter internus and externus muscles. The anterior portion of the levator ani muscle, called the pubococcygcus muscle musculus pubococcygcus , loops the perineal flexure of the rectum posteriorly.
A line formed by the junction of the mucous membrane and skin of the anus is seen below the level of the sinuses. T h e skin of the anus is lined with pigmented stratified squamous keratinized epithelium with pronounced papillae.
T h e skin contains sebaceous and glomiiorm circumanal glands. Topography of the large intestine. T h e caecum lies in the right iliac fossa 4 - 5 cm above the middle of the inguinal ligament. Its position varies: T h e base of the vermiform appendix is projected on a point between the right and middle third of the transverse line connecting both anterosuperior iliac spines bi-iliac line.
Posteri orly the caecum lies on the parietal peritoneum in the region of the. Zones of anal canal: I c o l u m n a r distal p a n II intermediate entire III cutaneous proximal p a n I main complex anal sinus 2its auxiliary p o u c h 3 auxiliary anal sinus 4circumanal sebaceous gland XX branching simple and complex circumanal glands X nonbranching circumanal gland.
O n the left and inferiorly it is related to the loops of the ileum. The posterior surface of the ascending colon is separated from the fascia covering the iliacus and the quadratus lumborum mus cles and the fascia of the lower portion of the right kidney by areolar rctropcritoneal paracolic tissue attendant to the colon.
On the left and anteriorly the ascending colon is in relation with the loops of the small intestine and the greater omentum. T h e transverse colon lies in the right hypochondrium, the epi gastrium, and the left hypochondrium, i. The middle, sagging, part of the intestine may reach the umbilicus or even descend to a lower level. Anteriorly the transverse colon is separated from the anterior abdominal wall by the greater omentum. Its superior surface is in relation with the inferior surface of the right lobe of the liver, the gall bladder, the greater curvature of the stomach, and the spleen.
Inferiorly the transverse colon is related to the loops of the small intestine, posteriorly it adjoins the third part of the duodenum and the pancreas. The transverse colon and its mesentery divide the ab-. The anterior surface of the descending colon is covered by the loops of the small intestine. The pelvic colon lies in the left iliac fossa and in the upper part of the cavity of the true pelvis; depending on the width of the mes entery the pelvic colon may pass beyond the midplane of the ab dominal cavity into the right half and ascend to the level of the transverse mesocolon.
Posteriorly the pelvic colon is separated by the peritoneum from the iliacus and quadratus lurnborum muscles as well as the common iliac vessels and the ureter. As it is indicated above, the pelvic part of the rectum lies in a hollow formed by the sacrum and coccyx. T h e retrorectal areolar tissue separates the posterior surface of the rectum from the sac rum, and the lateral and inferior surfaces from the muscles of the floor of the pelvis.
T h e anterior and superior surfaces of the pelvic part of the rec tum, which is covered by the peritoneum, are related to the loops of the small intestine and the urinary bladder in males and the body of the uterus and, lower, the uppermost part of the posterior wall of the vagina the posterior fornix in females.
T h e peritoneal pararectal folds run on the sides of the pelvic part of the rectum. T h e rectovaginal rectovesical septum separates the anterior surface of the extraperitoneal part of the rectum from the posterior wall of the urinary bladder in the middle , the posterior surface of the prostate lower , and the right and left seminal vesicles and the ampullar portions of the right and left vas deferens on the sides.
In females the anterior surface of the extraperitoneal part of the rectum is related to the posterior wall of the vagina from which it is separated by the connective-tissue rectovaginal septum.
Age features of the large intestine. T h e caecum of the newborn is funnel-shaped. The ascending colon is short in the newborn and lies under the liver but gradually descends with age and is found in the iliac fossa by the age of years. T h e transverse colon of a newborn is in the epigastrium because its mesentery is short at this age; by the age of 18 months the transverse colon increases almost threefold in length, descends to the level of the umbilicus in an adult and sags. T h e pelvic colon in children has a long mesentery as a result of which it reaches the level of the transverse mesocolon superiorly or the level of the ascending colon on the right.
T h e large intestine of a newborn has many folds and intestinal glands but the taeniae and sacculations haustrae are less devel oped. At old age the taeniae are thin and the sacculations and folds reduce in number and size. The position of the rectum in children is almost vertical because the sacrum is straighter in rela tion to the vertebral column. Circumanal glands specimen prepared by A.
Isolated complex circumanal gland from completely stained specimen of rectum. T h e left splenic flexure of the colon is on a level with the ninth costal cartilage or the eighth intercostal space, 4 cm higher than the right hepatic flexure.
It is in contact with the lower part of the spleen and posteriorly with the left kidney. T h e descending colon is related to the anterior surface of the left kidney superiorly. Lower it is separated just like the ascending colon from the fascia covering the quadratus lurnborum, the transversus abdominis, and the iliacus muscles by the areolar retropcritoncal paracolic tissue. T h e upper part of the descending.
It occupies the upper part of the abdominal cavity under the diaphragm see Fig. The gland rather resembles the cap of a large mushroom in shape or is wedge-shaped. It has a convex upper and a slightly concave lower surface. T h e convexity, however, is not symmetric because not the central part of the liver but its right posterior part is most convex and bulky and narrows wedge-like to the front and to the left.
The right to left size of the liver varies from 26 to 30 cm; the antcroposlcrior size of the right lobe is cm and that of the left lobe is cm; the maximum thickness right lobe varies from 6 to 9 cm. The liver weighs g on the average. It is red dish-brown in colour and pliant in consistency. The liver has a convex upper surface fades diapkragmatica , a lower, or visceral surface fades visceralis which is concave in places, a sharp lower border margo inferior separating the upper and lower surfaces in front, and a slightly convex posterior part pars posterior of the upper surface, which is called the posterior surface of the liver.
T h e lower border of the liver bears a notch for the Hgamentum teres indsura ligamenti teretis to the right of which is a fossa for the gall bladder. T h e upper surface fades diapkragmatica is convex and corre sponds to the shape of the dome of the diaphragm.
The convexity is greatest on the right, nearer to the posterior border of the dia phragm, where the liver is the thickest.
From the highest point the surface slants to the sharp lower border and to the left border of the liver, and passes steeply to the back, to the posterior and right parts of the upper surface of the liver. From the upper surface of the liver to the diaphragm ascends a sagittal peritoneal falciform.
T h e falciform ligament separates the liver on the upper surface into two partsthe right lobe of the liver lobus hepatis dex ter which is the largest and the thickest, and the left lobe of the liver lobus hepatis sinister which is smaller. This PDF book include common anatomy and physiology final exam questions conduct.
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To download free anatomy of the human body. T h e edge of the squamous part is separated into two parts: T h e external occipital protuberance protuberantia occipitalis externa Fig. T h e protuberance is easily pal pated through the skin. Laterally from it diverge paired raised su-. The external occipital crest crista occipitalis externa descends from the external occipital protuberance to the foramen magnum.
In the middle of the distance between the foramen magnum and the external occipital protuberance, the crest gives rise to the inferior nuchal lines linca nuckae inferiores , which diverge laterally and pass to the edges of the squamous part parallel to the superior lines.
All these lines mark the insertion of muscles. T h e surface of the squamous part below the superior nuchal lines is the site of at tachment of muscles terminating on the occipital bone. The cerebral surface fades cerebralis of the squamous part. It corresponds to the external occipital protuber ance on the external surface. T h e cruciate eminence gives rise to a groove for the transverse sinus sulcus sinus transversi passing laterally on either side, an as cending superior groove for the sagittal sinus sulcus sinus sagittalis superioris , and an internal occipital crest crista occipitalis intcrna descending to the posterior semicircumference of the foramen magnum.
Processes of the dura mater with the venous sinuses embedded in them are attached to the borders of the transverse and sagittal grooves and the internal occipital crest. It is a quadrangular plate convex on the outer surface. Two surfaces, external and internal, and four borders, superior, inferior, anterior, and posterior, are distinguished in it. The external surface fades externa is even and convex.
T h e most convex part is called the parietal eminence, or tuber tuber parietale. Below the tuber is a rough horizontal arched superior temporal Hue linca temporalis superior which arises from the ante rior border of the bone and, being a continuation of the superior temporal line of the frontal bone, stretches along the entire surface of the parietal bone to its posteroinferior angle.
Below this line and parallel to the inferior border of the parietal bone stretches an other, more defined line, the inferior temporal line linca temporalis inferior. T h e superior line gives attachment to the temporal fascia, the inferior line is the site of insertion of the temporal muscle. The internal surface fades intcrna is concave and bears poorly defined depressions corresponding to the gyri of the brain which are called impressions for the cerebral gyri impressiones digitatae , cerebral ridges and dendriform branching arterial sulci sulri arteriosi which are marks of the branches of the middle meningeal ar tery.
On the superior border of the cerebral surface of the bone passes an incomplete sagittal groove sulcus sinus sagittalis superioris and, together with the groove on the coutralateral parietal bone, forms a complete groove the sickle-shaped process of the dura maicr, falx ccrebri, is attached to the margins of the groove.
In the posterior part of the superior border of the bone is a small parietal foramen foramen parietale which is an emissary emissarium transmitting a branch of the occipital artery to the dura mater and the parietal emissary vein. Deep in the sagittal groove and next to it particularly on the parietal bones at an el derly age can be seen most of the small granular pits foveolae granulares granulations of the arachnoid mater of the brain pro ject here.
A small deep siginoid groove sulcus sinus sigmoidei , an impres-. It is continuous with the sigmoid groove on the temporal bone anteriorly and with the groove for the transverse sinus on the occipital bone posteriorly. T h e superior, sagittal border margo sagittalis runs straight and is strongly serrated. It is longer than the other borders and articu lates with the sagittal border of the coutralateral parietal bone by means of the sagittal suture sutura sagittalis.
T h e inferior, squamous border margo squamosa is tapered and arched and its anterior area is covered by the posterior part of the upper border of the greater wing of the sphenoid bone. Further to the back, the parietal border of the squamous part of the temporal bone is superimposed on it; the extreme posterior area articulates by means of notches with the mastoid process of the temporal bone. According to these three areas, the following three sutures form: T h e anterior, frontal border margo frontalis is serrated.
It ar ticulates with the parietal border of the squama of the frontal bone to form the coronal suture sutura coronalis. T h e posterior, occipital border margo oedpitalis is serrated and articulates with the lambdoid border of the occipital bone to form the lambdoid suture sutura lambdoidea. In accordance with the four borders, the parietal bone has four angles. T h e anterosuperior, frontal angle angulus frontalis is almost straight it is bounded by the coronal and sagittal sutures.
T h e anteroinferior, sphenoidal angle angulus spkenoidalis is acute it is bounded by the coronal and sphenoparietal sutures. T h e posterosupcrior, occipital angle angulus oedpitalis is ob tuse it is bounded by the lambdoid and sagittal sutures. T h e posteroinferior, mastoid angle angulus mastoideus is more obtuse than the posterosupcrior angle it is bounded by the lamb doid and parietomastoid SUtures. Its anterior par! It consists of four parts: The frontal squama squama jrontalis is convex to the front and has the following surfaces: The frontal surface fades externa is smooth, convex anteriorly and has an eminence on the median line.
This eminence is not de tectable in some cases. This is the line of the frontal suture sutura mctopica marking the union of the halves of the frontal bone in early childhood.
In the anterior parts, the frontal surface of the squama is continuous with the orbital surface fades orbitalis and forms the supraorbital margin margo supraorbitalis on both sides.
Above and parallel to this margin is a more or less defined arched eminence, the superciliary arch arms superdliaris. Above each arch is a rounded frontal eminence tuber frontale. Between and slightly above the superciliary arches the surface of the squama has a depressed area, the glabella.
T h e supraorbital margin has a small supraorbital notch indsura supraorbitalis in its medial third. This notch varies greatly and may be present as a supraorbital foramen foramen supraorbitale. Nearer to the median line, i. T h e su praorbital notch transmits the lateral branch of the supraorbital nerve and vessels, the frontal notch transmits the medial branch of this nerve and vessels.
A frontal foramen foramen frontale may be found in place of the notch. T h e supraorbital margin is continuous laterally with a blunt triangular zygomatic process processus zygomaticus , whose serrated edge unites with the frontal process of the zygomatic bone by means of the frontozygomatic suture sutura frontozygomatica.
An arched temporal line tinea temporalis ascends posteriorly from the zygomatic process. It separates the frontal surface of the squama from its temporal surface fades temporalis which is the anterosupcrior area of the temporal fossa where part of the temporal muscle arises. The cerebral surface fades interna of the frontal squama Fig.
It has poorly defined impressions for the gyri. The sagittal groove sulcus sinus sagittalis superioris runs in the middle of the superior parts of the internal surface. Both its edges pass upwards and to the back to unite with the sagittal groove of the parietal bone, while downwards they join to form a single sharp frontal crest crista frontalis to which the process of the dura mater, falx cerebri, is attached. At its lowest part the crest to gether with the ala of the crista gatli ala cristae galli ossis etkmoidalis form the foramen caecum foramen cecum y a blind opening occupied by a process of the dura mater.
The superior, or posterior, thickened border of the frontal squama is called the parietal margin margo parietalis. Its serrated border unites with the frontal border of the parietal bone to form the coronal suture sutura coronalis. T h e inferior triangular areas of the squama unite with the frontal border of the greater wings of the sphenoid bone. Each orbital plate pars orbitalis Fig.
Inferior orbital and superior cerebral surfaces are distinguished in it. T h e orbital surface fades orbitalis faces the cavity of the orbit and is smooth and concave. In its lateral part at the base of the zygomatic process it has a small shallow fossa for the lacrimal gland fossa glandulae laenmalis. I In medial p a n ol the orbital surface bears ;i poorly defined trochlear fossa fovta trochUaris , near to which a cartilaginous trochlcar spine spina trochlearis is often found it serves for attach ment of a cartilaginous ring which is a pulley, the trochlea, for the tendon of the superior oblique muscle of the eyeball.
T h e cerebral surface fades interna of the orbital part has clearly defined markings for the frontal lobes of the brain in the form of impressions for the gyri impressiones girorum and cerebral ridges of the cranium juga cerebralia.
T h e orbital plates are separated from one another by the ethmoidal notch indsura ethmoidalis into which fits the cribriform plate lamina cribrosaj of the ethmoid bone. T h e notch is bounded on the sides by a border lateral of which are a series of small pits.
They roof in the open ethmoidal cells of the superior part of the ethmoid bone to form their superior wall. Two eth moidal grooves, anterior and posterior, stretch transversely be tween the ethmoidal cells and together with the ethmoidal grooves of the labyrinth of the ethmoid bone form small canals which have small openings on the medial wall of the orbit: T h e margin of the ethmoidal notch articulates with the superior margin of the orbital plate lamina orbitalis of the ethmoid bone to form the frontoelhmoid suture sutura Jrontoethmoidalis.
Anteriorly the notch unites with the lacrimal bone by means of the frontolacrimal su ture sutura frontolacrimalis. T h e posterior border of the orbital plate is thin and serrated, and articulates with the lesser wing of the sphenoid bone to form the internal part of the sphenofrontal suture sutura spkenofrontalis.
The lateral border of the orbital plate is rough, triangular, and articulates with the frontal border of the greater wing of the sphe noid bone to form the external part of the sphenofrontal suture. Still laterally the border terminates at the zygomatic process. T h e nasal part pars nasalis of the frontal bone closes the eth moidal notch anteriorly in an arch-like fashion.
In the middle of its anterior part, the nasal spine spina nasalis sometimes a double one projects obliquely downwards and forwards. It has a tapering. T h e anterior parts of the margin unite with the superior border of the nasal bone to form the frontonasal suture sutura Jrontonasalis , the posterior parts join the frontal process of the maxilla processus Jrontalis by means of the frontomaxillary suture sutura Jrontomaxillaris.
Posteriorly, the inferior surface of the nasal part bears shallow ethmoidal pits which, as pointed out above, roof in the cells of the ethmoidal lab yrinths. O n either side of the nasal spine is the aperture of the frontal sinus apertura sinus Jrontalis. It stretches upwards and forwards and leads into the cavity of the respective frontal sinus.
T h e frontal sinus sinus Jrontalis see Figs 94 and is a paired cavity lodged between both plates of the frontal bone in its anteroinferior parts. It is an air paranasal sinus sinus paranasalis. T h e right and left sinuses are separated by a vertical septum of the frontal sinuses septum sinuum Jrontalium. T h e septum deviates to one or the other side as a result of which the sinuses differ in size. T h e borders of the sinuses vary considerably. Sometimes they reach upwards to the frontal eminence, downwards to the supraorbital margin, backwards to the lesser wings of the sphenoid bone, and laterally to the zygomatic processes.
By means of its ap erture the frontal sinus communicates with the middle meatus of the nose meatus nasi medius. T h e cavity of the sinus is lined with a mucous membrane. T h e body corpus ossis spkenoidalis is the middle part of the sphenoid bone, it is cuboid in shape and has six surfaces. In its middle part the superior surface facing the cranial cavity has a depression, the sella turcica, in the centre of which is the hypophyseal fossa fossa hypopkysialis Fig. T h e size of the fossa is determined by the size of the hypophysis.
The sella turcica is bounded by the tuberculum sellae anteriorly. To the back of it, on the lateral surface of the sella is an inconstantly present middle clinoid process processus clinoideus medius.
A shallow transverse optic groove sulcus chiasmatis passes to the front of the sella and lodges the optic chiasma chiasma opticum. O n both sides the groove is continuous with the optic fo ramen canalis opticus. In front of the groove is a smooth surface, jugum sphenoidale, that connects the lesser wings of the sphenoid bone.
T h e anterosuperior border of the body is serrated, projects forwards slightly, and unites with the posterior border of the crib riform plate lamina cribrosa of the ethmoid bone to form the sphenoethmoidal suture sutura spkenoethmoidalU.
T h e sella turcica is bounded posteriorly by the dorsum sellae terminating on both sides by a small posterior clinoid process processus clinoideus poste rior. T h e carotid groove sulcus caroticus stretches laterally from front to back of the sella it is an impression of the internal carotid artery and the attendant nerve plexus which are lodged here. A sharp process called the lingula of the sphenoid bone lingula spke noidalis projects at the posterior edge of the groove on its lateral side.
T h e posterior surface of the dorsum sellae is continuous with the superior surface of the basilar part of the occipital bone to form the clivus on which the pons, the medulla oblougata, the basilar artery and its branches are lodged.
T h e posterior surface of the body is rough. It is joined to the anterior surface of the basi lar part of the occipital bone by means of a cartilaginous layer to form the spheno-occipital joint synckondrosis spkenooccipitalis.
T h e cartilage is replaced by bony tissue with age and both bones fuse. Canalis opticus Squama occipitulis Tuberculum sctlac Sulcus chiasmatis Juiium sphenoidale Processus clinoideus posterior Processus clinoideus anterior. Fissuraorbiialis superior Foramen rotundum Processus clinoideus medius Foramen ovale Foramen spinosum.
Fissura orbitatis superior Margo squamosus Canalis pterygoideus Spina ossis sphenoidalis. Fossa scaphoidea Processus pterygospinqsus Fossa pterygoidea Processus pterygoideus Lamina medialis Incisura pterygoidea Sulcus tiamuli pterygoidei.
Facies temporal is Foramen rotundum Spina ossis sphenoidalis Canalis pterygoideus Processus vaginalis Crista sphenoidalis Rostrum sphenoidalc. The anterior and part of the inferior surface of the body face the nasal cavity. A vertical crest of the sphenoid crista sphenoidatis projects into the middle of the anterior surface. Its anterior edge adjoins the perpendicular plate lamina perpendicularis of the eth moid bone.
T h e lower segment of the crest is tapered and stretches downwards to form the rostrum of the sphenoid rostrum spkenoidale which is wedged in-between the alae of the vomer alae vomeris. T o both sides of the crest is a thin curved plate called the sphenoidal concha concha sphenoidatis Fig. Lateral to the aperture are small pits which roof in the cells of the posterior part of the ethmoid bone laby rinth. The external margins of these pits unite partially with the orbital plate of the ethmoid bone to form the sphenocthmoidal su ture sutura spkenoethmoidatis , while the inferior margins unite with the orbital process processus orhitalis of the palatine bone.
The sphenoidal sinus sinus sphenoidatis see Fig. Both the right and left cavities are sepa rated by the septum of the sphenoidal sinuses septum sinuum sphenoidalium which is anteriorly continuous with the crest of the sphenoid. Just like in the case of the frontal sinuses, the septum sometimes deviates to one side as a result of which the sinuses may differ in size.
Each sinus communicates with the nasal cavity by means of its aperture described above. The cavity of the sinus is lined with a mucous membrane. The lesser wings alae minores of the sphenoid bone arise from the anterosuperior angles of the body and project laterally as two horizontal plates at the base of which is a small round opening leading into a bony mm long optic foramen canalis opticus.
It transmits the optic nerve and the ophthalmic artery. T h e lesser wings have a superior surface facing the cranial cavity and an infe rior surface which faces the orbital cavity and forms the superior border of the superior orbital fissure fissura orbitalis superior. The anterior border of the lesser wing is thick and serrated and unites with the orbital plate of the frontal bone. T h e posterior con cave and smooth border projects into the cranial cavity freely and is the border between the anterior and middle cranial fossae fossae cranii anterior et media see Figs and T h e posterior bor der terminates medially by a projecting well-defined anterior clinoid process processus clinoideus anterior to which part of the dura mater is attached, forming the diaphragma sellae.
The greater wings alae majores arise from the lateral surfaces of the body of the sphenoid bone and stretch laterally. The greater wing has five surfaces and three borders. The superior, cerebral surface fades cerebralis is concave and faces the cranial cavity. It forms the anterior part of the middle cranial fossa and bears impressions for the gyri impressiones digitatae , cerebral juga, or ridges juga cerebralia , and arterial sulci suld arteriosi which are markings for the brain surface and middle meningeal arteries lodged here.
There are three openings at the base of the wing: The anterosuperior, orbital surface fades orbitalis is smooth, rhomboid, and faces the orbital cavity. It forms the greater part of the lateral wall of the orbit. A gap is left between the inferior bor der of this surface and the posterior border of the orbital surface of the maxillary body to form the inferior orbital fissure fissura orbitalis inferior Figs 48 and T h e anterior, maxillary surface fades maxillaris is a small tri angular surface bounded by the orbital surface superiorly and by the root of the pterygoid process of the sphenoid bone laterally and inferiorly.
It contributes to the formation of the posterior wall of the pterygopalatinc fossa fossa pterygopalatina see Figs and in which the foramen rotundum is located. T h e superolateral, temporal surface fades temporalis is slightly concave and participates in the formation of the wall of the tem poral fossa fossa temporalis from which the temporal muscle arises.
This surface is bounded inferiorly by the infratemporal crest crista infiatemporalis below which is an area with the foramen ovale and the foramen spinosuin. This area forms the superior wall of the in fratemporal fossa fossa infralemporalis in which part of the lateral pterygoid muscle originates.
T h e superior, frontal border margo frontalis is widely serrated and articulates with the orbital plate of the frontal bone by means of the sphenofrontal suture sutura sphenofrontalis.
T h e lateral parts of the frontal border terminate as a sharp parietal border margo parietalis which unites with the sphenoid angle of the parietal bone to form the sphenoparietal su ture sutura sphenoparietalis.
T h e medial parts of the frontal border are continuous with a thin free border which binds the superior orbital fissure fissura orbitalis superior inferiorly because of a gap left between this border and the inferior surface of the lesser wing. T h e anterior, zygomatic border margo Qigomaticus is serrated and articulates with the frontal process of the zygomatic bone to form the sphenozygomatic suture sutura sphenojygomatica. T h e posterior, squamous border margo squamosus unites with the sphenoidal border margo sphenoidalis of the temporal bone by means of the sphenosquamous suture sutura sphenosquamosa.
Pos teriorly and laterally the squamous border terminates as the spine of the sphenoid spina ossis sphenoidalis to which are attached the sphenomandibular ligaments and a bunch of muscles tensing the soft palate, the tensor palati muscle. Medially of the spine of the sphenoid, the posterior border of the greater wing stretches anteriorly of the petrous part pars petrosa of the temporal bone and binds the sphenopetrosal fissure fissura sphenopetrosa which is medially continuous with the for amen lacerum see Figs 96 and In a nonmaccrated skull this fissure is filled with cartilaginous tissue to form the sphenopetrous joint synchondrosis sphenopetrosa.
T h e pterygoid processes processus pterygoidei Figs 63 and 64 spring downwards from the junction of the greater wings and the body of the sphenoid bone. They arc formed of two plates, lateral. The lateral pterygoid plate lamina laleralis proussus pterygoidei is wider but thinner and shorter than the medial plate the lateral pterygoid muscle originates from its lateral surface. The medial pterygoid plate lamina medialis processus pterygoidei is narrower, thicker and slightly longer than the lateral plate.
Both plates fuse by means of their anterior borders and diverge to the back to form the pterygoid fossa fossa pterygoidea in which the medial pterygoid muscle arises. In the inferior parts, the plates do not fuse but bind the pterygoid notch incisura pterygoidea into which ihe pyramid process, or tubercle processus pyramidaHs of the palatine bone fits.
T h e free end of the medial plate terminates as the pterygoid hamulus hamulus pterygoideus which projects downwards and laterally and has on its lateral surface the sulcus of the pterygoid hamulus sulcus kamuli pterygoidei this sulcus lodges the tendon of the tensor veli palatini muscle. T h e posterosuperior border of the medial plate becomes wider at the base to form an elongated scaphoid fossa fossa scapkoidca in which the tensor veli palatini muscle originates. Laterally of the scaphoid fossa is a shallow groove for the pharyngotympanic tube sulcus tubae auditivae Fig.
This groove lodges the cartilaginous part of the auditory tube. Above and medially of the scaphoid fossa is an opening leading into the pterygoid canal canalis pterygoideus. T h e canal stretches sagittally in the depth of the pterygoid process and opens on the maxillary surface of the greater wing on the posterior wall of the ptcrygopalatine fossa.
Under the opening along the anterior edge of the fossa is the pterygopalatine groove. From the base of the medial plate a flat horizontal vaginal pro cess processus vaginalis projects medially, it is situated below the body of the sphenoid bone and covers the ala of the vomer ala vomeris from the lateral side.
As a result the groove of the vaginal process, the vomerovaginal sulcus sulcus vomerovaginalis y which faces the wing is transformed into the vomerovaginal canal canalis vomerooaginalis. A small palatinovaginal sulcus sulcus palatinovaginalis some times stretches sagittally lateral of the process, in which case the sphenoid process of the palatine bone lying directly below the sul cus closes it to form the palatinovaginal canal canalis palatinovagi nalis both canals transmit nerves arising from the pterygopalatine ganglion, while the palatinovaginal canal transmits in addition branches of the sphenopalatine artery.
T h e pterygospinous process processus pterygospinosus extends sometimes from the posterior border of the lateral plate towards the spine of the sphenoid which it may reach to form an opening. T h e organ of hearing and equilib rium is lodged in it. The temporal bone articulates with the mandi ble and is a support for the masticatory apparatus.
O n the external surface of the bone is the lateral orifice of the external auditory meatus porus acusticus externus around which the three parts of the temporal bone are arranged: The squamous part pars squamosa has the shape of a plate sit uated almost sagittally. Its outer temporal surface fades temporalis is rather rough and slightly convex. In its posterior part it bears a vertical groove for the middle temporal artery sulcus arteriae tem poralis mediae , which is a mark of the artery of the same name.
In the posteroinferior portion of the squamous part is an arched line which is continuous with the inferior temporal line of the parietal bone. Above and slightly in front of the external acoustic meatus, the squamous part gives rise to a horizontally projecting zygomatic process processus zygomaticus which has a wide root but becomes gradually narrower. T h e process has a medial and a lateral surfaces. T h e anterior end of the zygomatic process is serrated and joins the temporal process of the zygomatic bone processus temporalis to form the zygomatic arch arcus zygomaticus see Figs 50 and O n the inferior surface of the root is a transversely-oval articu lar fossa fossa mandibularis for articulation with the head of the mandible.
T h e fossa is bounded anteriorly by the eminentia articularis tuberculum articulare Fig. T h e outer surface of the squamous part contributes to the for mation of the temporal fossa fossa temporalis in which bundles of the temporal muscle originate. T h e inner, cerebral surface of the squamous part fades cerebralis is slightly concave and carries impressions for the gyri impressiones digitatae , cerebral juga juga cerebralia , and an arterial sulcus sulcus arteriosus lodging the middle meningeal artery.
T h e squamous part of the temporal bone has two free borders, sphcnoidal and parietal. T h e anteroinferior, sphenoidal border margo sphenoidalis is wide, serrated and articulates with the squamous border of the greater wing of the sphenoid bone to form the sphenosquamous suture sutura sphenosquamosa. T h e superoposterior, parietal border margo parietalis is sharp and is longer than the sphenoidal border; it articulates with the squamous border of the parietal bone.
Incisura parietalis Margo sphcnoidalis Bminentia arcuala Sulcus sinus sigmoidci Foramen mastoideum. The petrous part pars pctrosa , or pyramid, of the temporal bone consists of the posterolateral and anteromedial parts. The posterolateral part is the mastoid process processus mastoideus situated to the back of the external acoustic meatus. Outer and inner surfaces are distinguished in it. T h e outer surface is con vex, rough, and provides for muscle attachment.
The mastoid pro cess is continuous downwards with a conical projection which is easily palpated through the skin. O n the inner surface, the process is bounded by a deep mas toid notch indsura mastoidea from which the posterior belly of the digastric muscle venter posterior musculi digastrici arises. T h e occipi tal groove sulcus arteriae oedpitalis for the occipital artery is paral lel to and slightly behind the notch.
A mastoid foramen foramen masioideum is often found at the base of the mastoid process on its lateral surface. Sometimes it is in the suture joining the mastoid process and the occipital bone and is a venous emissarium. On the inner, cerebral surface of the mastoid process is a wide S-shaped sigmoid groove sulcus sinus sigmoidei which is continuous upwards with the sigmoid groove of the parietal bone and then. Downwards the sigmoid sinus is continuous with the similar sinus of the occipi tal bone.
T h e mastoid process is bounded posteriorly by a serrated oc cipital border margo oedpitalis which articulates with the mastoid border of the occipital bone to form the occipttomastoid suture sutura oedpitomastoidea. In this suture, in its middle part or occipital edge is the mastoid foramen foramen masioideum sometimes more than one which, as it is pointed out above, lodges the mastoid emissary veins venae emissariae mastoideae connecting the subcu taneous veins of the head with the sigmoid venous sinus and mas toid branch of the occipital artery.
Superiorly the mastoid process is bounded by the parietal bor der margo parictalis which at the junction with the parietal border of the squamous part of the temporal bone forms the parietal notch indsura parictalis ; the mastoid angle of the parietal bone is wedged into it to form the parietomastoid suture sutura parietomas-. Fossula pctrosa Aperturaexterna canaliculi cochleae Canaliculus mastoideus Fossa jugularis. At the junction of the outer surface of the mastoid process and the outer surface of the squamous part the remnants of the squamomastoid suture sutura squamosomastoidea can be detected; it is well defined on a child's skull.
Bony air sinuses called the mastoid air cells cellulae mastoideae Fig. T h e tympanic antrum antrum mastoideum is a cavity al ways found in the central part of the process; the mastoid cells open into it and it communicates with the tympanic cavity.
T h e mastoid cells and the tympanic antrum arc lined with a mucous membrane. T h e anteromedial part of the pars petrosa is medial of the squamous part and the mastoid process.
It has the shape of a trihe dral pyramid whose long axis runs medially and from back to front. T h e base of the petrous part faces laterally and to the back; the apex of t h e petrous part apex partis petrosae is directed medi ally and forwards. Three surfaces anterior, posterior, and inferior and three bor. T h e anterior surface fades anterior partis petrosae Fig. It is smooth and wide and stretches obliquely downwards and forwards and is continuous with the cerebral sur face of the squamous part from which it is sometimes separated by the petrosquamous fissure fissura petrosquamosa.
Almost in the middle of the anterior surface is an arcuate eminence eminentia arcuata formed by the underlying anterior semicircular canal of the labyrinth. A small area called the roof of tympanum, or tegmen tympani is situated between the eminence and the petrosquamous fissure; under it is the tympanic cavity cavum tympani. Close to the apex of the petrous part the anterior surface bears a small trigeminal impression impressio trigemini which is a mark for the trigeminal nerve ganglion.
Lateral of the impression is the hiatus for the greater super ficial petrosal nerve hiatus canalis nervi petrosi majoris from which a narrow groove for the greater superficial petrosal nerve sulcus nervi petrosi majoris branches off medially.
A small hiatus for the lesser. Vertical section made parallel to the axis of the petrous part. T h e posterior surface of the petrous part fades posterior partis petrosae Fig. Almost in the middle of this surface is a round poms acusticus internus which leads into the internal audi tory meatus meatus acusticus internus - T h e porus transmits the fa cial, intermediate, and vestibulocochlcar nerves and the artery and vein of the labyrinth. A shallow subarcuate fossa fossa subarcuata is present a little above and lateral to the porus acusticus internus.
It is well defined in the newborn; it lodges a process of the dura mater. Still laterally to porus acusticus internus is a slit-like external opening of the aqueduct of the vestibule apertura externa aquedudus vestibuli transmitting the cndolymphatic duct from the cavity of the internal ear. T h e inferior surface of the petrous part fades inferior partis pet rosae Fig. It carries a round or oval jugular fossa fossa jugularis lodging the upper bulb of the internal jugular vein.
T h e floor of this fossa has a small groove for the auricular branch of the vagus nerve. T h e groove leads into the orifice of the mastoid canaliculus canaliculus mastoideus which opens into the tympanomastoid fissure fissura tympanomastoidea. T h e posterior margin of the jugular fossa is bounded by the jugular notch incisura jugularis which is divided into two parts, an anteromedial part and a posterolateral part, by a small intrajugular process processus intrajugularis.
T o the front of the jugular fossa is a round orifice leading into the carotid canal canalis caroticus which has another orifice on the apex of the petrous part. A small petrosal fossa fossula petrosa lies between the anterior circumference of the jugular fossa and the external orifice of the carotid canal; the inferior ganglion of the glosso-pharyngeal nerve is lodged in it.
Deep in the fossa is an opening into the canaliculus for the tympanic nerve canaliculus tympanicus in which the inferior. Antrum mastuidcum Canalis semicircular is lalcralis Canalis scmicircularis anterior Canalis facialis Tegmen tympan.
Vertical section made through external auditory mcatus. Porus acusiicus internus Mealus acusiicus internus Feneslra cochleae Veslibulum Canalis facialis Canalis scmicircularis anterior Canalis semicircularis latcralis. T h e canaliculus opens into the middle ear auris media or the tympanic cavity cavum tympani.
T h e styloid process processus styloideus projects downwards and slightly forwards lateral of the jugular fossa. It varies in length and is the site of origin of muscles and ligaments.
A bony projection of the tympanic part, called the sheath of the styloid process vagina processus styloidei descends in front of and lateral to the root of the process. T o the back of the root of the process is the stylomastoid fo ramen foramen stylomastoideus which is the external opening of the canal for the facial nerve canalis farialis. The superior border of the petrous part margo superior partis petrosae separates the anterior surface from the posterior surface.
It carries the groove for the superior petrosal sinus sulcus sinus petrosi superioris a mark of the superior petrosal venous sinus ; the tentorium cerebelli which is a part of the dura mater is also at tached to the groove. T h e groove is continuous posteriorly with the.
T h e posterior border of the petrous part margo posterior partis petrosae is the junction of its posterior and inferior surfaces.
It car ries on its cerebral surface the groove for the inferior petrosal si nus sulcus sinus petrosi inferioris a mark of the inferior petrosal ve nous sinus. A triangular funnel-like depression bearing the external opening of the cochlear canaliculus apertura externi canali culi cochleae is almost in the middle of the posterior border near the jugular notch.
T h e anterior border of the petrous part margo anterior partis petrosae is on the lateral side of its anterior surface and is shorter than either the superior or posterior border.
It is separated from the squamous part of the temporal bone by the petrosquamous fissure fissura petrosquamosa. Lateral of the internal opening of the carotid canal the anterior border carries the orifice of the musculotubal canal canalis musculotubarius which opens into the tym panic cavity see The Musculotubal Canal.