12A Cervical Vertebrae: Atlas and Axis. 12B Cervical Vertebrae [C1-C4] Assembled: 50B Teeth - Upper and Lower Permanent. 51A Anatomy of a Tooth . Pocket Atlas of. Human Anatomy. Based on the International Nomenclature. Heinz Feneis. Professor. Formerly Institute of Anatomy. University of Tübingen. In this post, we have shared an overview and download link of Netter's Atlas of Human Anatomy 7th Edition PDF. Read the overview below and.
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Color Atlas of Anatomy. Johannes ronaldweinland.info Chihiro Yokochi. Elke Lütjen- Drecoll. A Photographic Study of the Human Body. Seventh Edition. This 6th edition of Anatomy: A Regional Atlas of the Human Body is Sobotta, J. Atlas. Color Atlas and Textbook of Human Anatomy Volume 3 Thieme. pdf. PDF | Content: Chapter 1. Embryology: 20 images, 20 clinical tips, 10 review questions; Chapter 2. Back: 39 images, 36 clinical tips, 10 review questions;.
In addition to the famous work of Dr. Carlos A. Together, these two uniquely talented physician-artists highlight the most clinically relevant views of the human body. In addition, more than 50 carefully selected radiologic images help bridge illustrated anatomy to living anatomy as seen in everyday practice. Region-by-region coverage, including Muscle Table appendices at the end of each section. Updates to the 7th Edition — based on requests from students and practitioners alike: New Systems Overview section featuring brand-new, full-body views of surface anatomy, vessels, nerves, and lymphatics.
The third section deals with treatment, drugs, injections and therapists, surgery, alternative medicine, self-help and living with arthritis. The book concludes with useful addresses and an index. Each chapter is clearly set out and very easy t o read, illustrations complementing the text. At intervals there are brief case histories and highlighted advice.
This book will be of use to all arthritis sufferers and particularly to self-help groups, also to relatives and friends. Concise, easily understood and readable; very good value. This is the second edition of a text first published in The overall organisation of the content of the book remains unchanged but the presentation of the contents is considerably improved.
The illustrations appear much clearer than in the previous edition and the use of boxes around the numerical indices t o the photographs enhances the ease with which the text may be used. Both the new photographslline diagrams in the revised text, the increased detail concerning the structures under review and their relative positions within the body, are good. This is a text which relates well to the living model despite being largely based on dissected parts.
It is not a primary text but is certainly a useful adjunct, particularly for students. The availability of a small paperback version of the large hardback book is excellent, both from a financial and a 'portable' point of view. In Great Britain million prescriptions are dispensed each year, and on average every individual obtains seven prescribed items. This book aims to explain what drugs are for, and what side effects or interaction with other drugs may occur, and adopts a holistic approach.
Its seven main sections correspond to body areas, with drug fact sheets for all the common drugs used t o treat each health problem within that section. The lateral portion inserts into the lat- eral portion of the superior orbicularis muscle, elevates and everts turns inside out the upper lip, and contributes to deepening the nasolabial sulcus.
The levator labii superioris alaeque nasi muscle is innervated by the zygomatic and buc- cal branches of the facial nerve cranial nerve VII. Levator Labii Superioris Muscle The levator labii superioris muscle originates lateral to the levator labii superioris alaeque nasi muscle from the inferior surface of the orbit to course inferiorly and medially to insert into the superior orbicularis oris muscle. It elevates and everts the upper lip and contrib- utes to deepening the nasolabial furrow.
The levator labii superioris superior muscle is innervated by the zygomatic and buccal branches of the facial nerve cranial nerve VII. Zygomaticus Minor Muscle Sometimes absent, the zygomaticus minor muscle originates from the zygomatic bone lateral to the levator labii superioris and tracks inferiorly and medially to insert into the superior portion of the orbicularis oris muscle.
Its action elevates the upper lip and con- tributes to deepening the nasolabial fold, as in smiling. The zygomaticus minor muscle is innervated by the zygomatic and buccal branches of the facial nerve cranial nerve VII. Zygomaticus Major Muscle The zygomaticus major muscle originates from the zygomatic bone, lateral to the zygo- maticus minor muscle. It courses inferiorly and medially to insert into the superior portion of the orbicularis oris muscle and the modiolus.
It is often composed of superficial and deep portions. Together with the levator anguli oris, its action pulls the lips superiorly and laterally such as when smiling or laughing. The zygomaticus major muscle is innervated by the buccal and zygomatic branches of the facial nerve cranial nerve VII.
Depressor Labii Inferioris Muscle The depressor labii inferioris muscle originates from the external oblique line of the mandible. It travels superiorly and medially to insert into the modiolus and the inferior orbicularis oris muscle. Its action pulls the lower lip down during mastication and may contribute to facial expressions such as sadness or sorrow. The depressor labii inferioris muscle is innervated by the mandibular branch of the facial nerve cranial nerve VII.
Its action elevates, protrudes, and everts the lower lip and may crease the chin. The mentalis muscle is innervated by the mandibular branch of the facial nerve cranial nerve VII. Levator Anguli Oris Muscle Caninus The levator anguli oris muscle originates from the canine fossa to insert into the modiolus and the superior portion of the orbicularis oris superior muscle.
As indicated by its name, its action elevates the angle of the mouth and, together with the zygomaticus major muscle, pulls the lips superiorly and laterally and deepens the nasolabial fold, as in smiling or laughing. The levator anguli oris muscle is innervated by zygomatic and buccal branches of the facial nerve cranial nerve VII.
Depressor Anguli Oris Muscle The depressor anguli oris muscle partially covers and is lateral to the depressor labii inferi- oris muscle and is superficial to the platysma muscle. It originates from the external oblique line of the mandible and courses superiorly to the modiolus and the inferior por- tion of the orbicularis oris. Superiorly it is continuous with the levator anguli oris muscle and inferiorly with the platysma muscle. Its action depresses the angle of the mouth, as indicated by its name, such as in an expression of sadness.
The depressor anguli oris is innervated by the mandibular and buccal branches of the facial nerve cranial nerve VII. It covers the majority of the anterior and lateral surfaces of the neck. Its extension is very variable. It is deep to the depressor anguli oris muscle. In most individuals, it extends to the cheeks and the muscles of the mouth and the modiolus. However, for some, it can spread even farther up to the muscles surrounding the eyes. When this muscle contracts, it expands the neck and pulls the skin of the neck upward, which may also facilitate the drainage of nearby blood vessels.
Also, this muscle may play a role in the downward movements of the lower lip and jaw. The platysma is innervated by the cervical branch of the facial nerve cranial nerve VII. The tongue is composed of and controlled by the following two groups of muscles: Intrinsic muscles have origins and insertions inside the tongue. Extrinsic muscles have an origin outside the tongue and an insertion in the tongue. Intrinsic Muscles of the Tongue Figure The intrinsic muscles form a complex array of interdigitating muscle fibers.
This complex arrangement allows for precise adjustments in tongue form and position. There are four intrinsic muscles, as follows: Superior longitudinal muscle 2.
Inferior longitudinal muscle 3. Transverse muscle 4. These muscles allow the tongue to move forward, backward, upward, downward, and laterally. Each name includes the word glossus, which means tongue, and another term indicating the external origin. There are four extrinsic muscles, as follows: Palatoglossus muscle 2.
Styloglossus muscle 3. Hyoglossus muscle 4. It requires the complex coordinated movements of the jaw, lips, cheeks, and tongue. The origin of jaw muscles, often called muscles of mastication, is typically on the skull and the insertion of jaw muscles is on the mandible, which is the movable portion of the jaw around the temporo- mandibular joint. Clearly, movements of the jaw are important for speech production, and as a result of biomechanical linkage, they influence the lips and the tongue.
The mus- cles of mastication can generally be divided into jaw-opening and jaw-closing muscles, or jaw elevators and jaw depressors, respectively.
Temporomandibular Joint Figure The temporomandibular joint is a synovial joint between the condylar process of the man- dible and the mandibular articular, glenoid fossa of the temporal bone. The articular surfaces of both structures are covered with fibrocartilage and separated by and connected to a cartilaginous articular disc.
A fibrous articular capsule joint capsule surrounds these structures and thickens laterally to form the temporomandibular lateral ligament.
This ligament courses from the mandible to the articular tubercle and zygomatic process of the temporal bone. Two other ligaments, the stylomandibular ligament and the sphenoman- dibular ligament, both located medially, may provide some additional support. Two movements are associated with the temporomandibular joint, as follows: Translation is a gliding type of movement that can be either bilateral backward- forward movements of the jaw or unilateral the mandible moves from one side to the other.
Imagine the jaw rotating around an imaginary horizontal axis through the condylar processes of the two sides of the mandible. Mastication and speech involve a combination of these two types of jaw movements, with specific movement trajectories influenced by the nature of the food bolus and the position within the masticatory sequence from food ingestion to swallowing for mastica- tion and the specific speech sound produced and phonetic environment for speech.
There is also individual variability in both masticatory and speech movements. The masseter muscle originates from the zygomatic process of the maxilla and the zygomatic arch.
Fibers travel inferiorly to insert on the external surface of the angle and ramus of the mandible. Some fibers also insert on the coronoid process of the mandible. The masseter elevates the mandible. Superficial fibers may contribute to jaw protrusion and deep fibers to jaw retraction. The masseter muscle is innervated by the masseter nerve of the mandibular division of the trigeminal nerve cranial nerve V. Temporalis Muscle The temporalis muscle is composed of anterior, middle, and posterior portions.
It origi- nates from the temporal fossa on the frontal, parietal, temporal, and sphenoid bones. Its fibers converge under the zygomatic arch to form a tendon that inserts on the coronoid process and the anterior surface of the ramus of the mandible. Contraction of the anterior and middle portions, composed principally of vertical fibers, elevates the mandible.
Contraction of the posterior portion, which is made of more horizontal fibers, may elevate and retract the mandible. Unilateral contraction of these muscle fibers may contribute to lateral movements of the jaw. The temporalis muscle is innervated by the deep temporal nerve of the mandibular division of the trigeminal nerve cranial nerve V. Medial Internal Pterygoid Muscle The medial internal pterygoid muscle originates primarily from the medial surface of the lateral pterygoid plate of the sphenoid bone.
A small group of fibers originates from the maxillary tuberosity and from the pyramidal process of the palatine bone. The fibers travel inferiorly, posteriorly, and laterally to insert on the internal surface of the angle and ramus of the mandible. This muscle forms, with the masseter muscle, a sling that surrounds the angle of the mandible and works with the masseter muscle and temporalis muscle to elevate the jaw. It acts in synergy with the lateral pterygoid muscle and the masseter muscle for jaw protrusion.
Unilateral contraction of the medial pterygoid muscle moves the mandible laterally toward the opposite side. This action permits grinding movements during mastication.
The medial pterygoid muscle is innervated by the medial pterygoid nerve of the man- dibular division of the trigeminal nerve cranial nerve V. The superior portion originates from the fossa of the greater wing of the sphenoid bone and the inferior portion from the external surface of the lateral pterygoid plate of the sphenoid bone.
Fibers course horizon- tally to insert on the articular disc of the temporomandibular joint and on the condylar process of the mandible. The superior portion of this muscle is co-activated with jaw- closing muscles during mastication.
The bilateral contraction of the inferior portion protrudes the mandible. The alternating unilateral contraction of the inferior portion produces a lateral movement of the mandible toward the opposite side. The lateral pterygoid muscle is innervated by the anterior trunk of the mandibular division of the trigeminal nerve cranial nerve V. Digastric Muscle The digastric muscle is frequently classified as a suprahyoid muscle.
This central tendon is fixed to the hyoid bone by a loop-shaped intermediate tendon. With the jaw fixed by other muscles, muscular contraction may contribute to the elevation of the hyoid bone.
With the hyoid bone fixed by other muscles, the digastric muscle acts as a jaw opener. The posterior belly of the digastric muscle is innervated by the digastric branch of the facial nerve cranial nerve VII , and the anterior belly of the digastric muscle is innervated by the mylohyoid branch of the inferior alveolar nerve of the mandibular division of the trigeminal nerve cranial nerve V.
The anterior and middle fibers insert into the median mylohyoid raphe joined by muscular fibers of the opposite side.
The posterior fibers insert on the hyoid bone. The mylohyoid is fan-shaped and contributes to the muscular floor of the mouth. Contraction elevates the hyoid and the floor of the mouth or stabilizes the floor. It can also contribute to jaw opening if the hyoid bone is fixed. The mylohyoid muscle is innervated by the mylohyoid branch of the inferior alveolar nerve of the mandibular division of the trigeminal nerve cranial nerve V. Geniohyoid Muscle The geniohyoid muscle extends from the internal surface of the mandible inferior mental spine to the hyoid bone.
Two bellies are located on each side of the median line and almost parallel to the anterior bellies of the digastric muscle, which are inferior. Contraction of the mylohyoid and the geniohyoid muscles may retract the jaw. Their contraction also contrib- utes to jaw opening if the hyoid bone is stabilized. The geniohyoid muscle is innervated by the first cervical spinal nerve C1 traveling with the fibers of the hypoglossal nerve cranial nerve XII. Note the digastric and the mylohyoid muscles, both jaw openers.
It is formed principally by five muscles: The only intrinsic muscle of the soft palate is the uvular muscle. All other muscles have an exterior attachment. Fibers originate from the petrous por- tion of the temporal bone and the inferior aspect of the cartilaginous pharyngotympanic auditory tube.
Fibers travel inferiorly and toward the midline to insert into the palatine raphe aponeurosis of the soft palate. Contraction of this muscle pulls the soft palate to- ward the posterior pharyngeal wall. The role of this muscle in contributing to the opening of the pharyngotympanic auditory tube for the ventilation of the middle ear is contro- versial see Figure [p.
The levator veli palatini muscle is innervated by the pharyngeal branch of the vagus nerve cranial nerve X via the pharyngeal plexus. The fibers travel forward and downward to converge on a tendon that wraps around the hamulus and inserts into the palatine raphe aponeurosis and the hori- zontal plates of the palatine bone. This muscle dilates the pharyngotympanic tube and may also tense the palate.
The tensor veli palatini muscle is innervated by the medial pterygoid nerve of the man- dibular division of the trigeminal nerve cranial nerve V. Fibers course inferiorly to insert underneath the sides of the posterior portion of the tongue, principally on superficial muscles located under the pos- terior portions of the sides of the tongue and transverse muscles.
The muscular fibers of the palatoglossus muscle form the bulk of the palatoglossal arch or anterior faucial pillar visible in the oral cavity. Contraction of this muscle may depress the soft palate or elevate the tongue with the soft palate fixed. This muscle approximates the palatoglossal arches.
The palatoglossus muscle is innervated by the pharyngeal branch of the vagus nerve cranial nerve X via the pharyngeal plexus. Palatopharyngeus Muscle see Figure [p. Its fibers form the bulk of the palatopharyngeal arch posterior faucial pillar. Fibers travel inferiorly with the muscular fibers of the stylopharyngeus muscle. The palatopharyngeus muscle inserts on the posterior border of the thyroid cartilage and on the inferior pharynx. Con- traction of this muscle may depress the soft palate, elevate and constrict the pharynx, and elevate the larynx.
This muscle approximates the palatopharyngeal arches.
The palatopharyngeus muscle is innervated by the pharyngeal branch of the vagus nerve cranial nerve X via the pharyngeal plexus. Uvular Muscle Musculus Uvulae see Figure [p. The function of this muscle is not well under- stood. However, it may play a role in the elevation of the soft palate. The uvula is an im- portant landmark during an oral examination because its orientation and form may reflect anomalies of the hard and soft palate. The uvular muscle is innervated by the pharyngeal branch of the vagus nerve cranial nerve X via the pharyngeal plexus.
Its fibers circle around posteriorly to insert into the median pharyn- geal raphe. This muscle forms the sides and the back of the nasopharynx and a part of the posterior wall of the oropharynx. Contraction of this muscle pulls the pharyngeal wall forward and reduces the pharyngeal diameter during swallowing, thus contributing to the contraction or propulsive pressure applied to the swallowed bolus.
It also contributes to pharyngeal tone and plays a role in velopharyngeal closure, which is discussed on p. The superior constrictor muscle is innervated by the pharyngeal branch of the vagus nerve cranial nerve X via the pharyngeal plexus. Middle Pharyngeal Constrictor Muscle see Figure [p.
Its contraction reduces the diameter of the pharynx and contributes to the contrac- tion or propulsive pressure applied to the swallowed bolus. It also contributes to pharyn- geal tone. The middle constrictor muscle is innervated by the pharyngeal branch of the vagus nerve cranial nerve X via the pharyngeal plexus. Inferior Pharyngeal Constrictor Muscle see Figure [p.
Some fibers originate from the sides of the cricoid cartilage to form the cricopha- ryngeus muscle, which forms the sphincter-like opening to the cervical esophagus during swallowing. A myotomized and residual form of this muscle and the pharynx are used to generate the esophageal sound source used by patients with laryngectomies.
Swallowed air is expelled against a closed esophageal sphincter, causing it to vibrate. Part of this muscle originates from the thyroid lamina and inserts on the median pha- ryngeal raphe thyropharyngeus.
Contraction of this muscle reduces the diameter of the inferior part of the pharynx. The inferior constrictor muscle is innervated by the pharyngeal branch of the vagus nerve cranial nerve X via the pharyngeal plexus, as well as by the recurrent laryngeal nerve and external branch of the superior laryngeal nerve of the vagus nerve. Its fibers mix with those of the palatopharyngeus muscle.
Its contraction contributes to the elevation of the pharynx during swallowing and may contribute to the distortion of the tubal cartilage of the pharyngotympanic tube to permit aeration of the middle ear. The salpingopharyngeus muscle is innervated by the pharyngeal branch of the vagus nerve cranial nerve X via the pharyngeal plexus. Stylopharyngeus Muscle Figure [p. Its origin is on the base of the styloid process of the temporal bone. It travels inferiorly and medially between the superior and middle pharyngeal constrictor muscles.
This muscle inserts in the mucous membrane of the pharynx and on the thyroid cartilage. Its contraction elevates the larynx and elevates and expands the pharynx during swallowing. The stylopharyngeus muscle is innervated by the glossopharyngeal nerve cranial nerve IX. Velopharyngeal Mechanism The velopharyngeal mechanism velopharyngeal closure is an essential process for speech and swallowing.
It involves the movement of many articulatory structures that act to modify the coupling between the nasal and oral cavities. Some speech sounds are produced with the laryngeal voice source passing only through the vocal tract, excluding the nasal cavity oral sounds , and some are produced with both the oral and nasal cavities nasal sounds.
The velopharyngeal mechanism acts as a regulator for coupling or decoupling of the nasal cavity from the rest of the vocal tract. Elevating and retracting the soft palate and constricting the walls of the nasopharynx and anterior movements of the posterior wall of the pharynx block the nasal cavity for the production of oral sounds. Opposite movements of the velopharynx allow the laryngeal sound source to pass through and thus be modified by the nasal cavity.
This creates the nasal sounds. Velopharyngeal closure is an important airway protective mechanism for swallowing. Closure prevents food from entering the nasal cavity during the passage of the bolus through the pharynx. Note especially the salpingopharyngeus muscle. Note especially the stylopharyngeus muscle. This complex structure is briefly summarized here. Upper Esophageal, or Cricopharyngeal, Sphincter Figures , [p. It is formed by the cricopharyngeus muscle.
The sphincter is normally closed as a result of passive relaxation forces and tension provided by the cricopharyngeus and the apposition of the cricoid cartilage anteriorly. Primary Esophageal Peristalsis see Figure [p. It occurs subsequent to pharyngeal contraction and the opening of the upper esophageal sphincter. Contractions in striated cervical esophageal muscle inner circular and outer longitudinal fibers are followed by smooth thoracic muscular contractions.
Secondary peristalsis may clear bolus residue. Lower Esophageal Sphincter see Figure The lower esophageal sphincter is the muscular junction between the esophagus and the stomach.
It is closed to prevent gastroesophageal reflux by smooth esophageal muscle and crural portions of the diaphragm. The sphincter opens to accommodate the passage of the swallowed bolus into and out of the esophagus. Elevates the floor of the mouth and the Mylohyoid branch of the inferior alveolar internal oblique midline raphe, where fibers hyoid bone nerve of the mandibular division of the line on the internal are linked with those of the Contributes to jaw opening if hyoid bone trigeminal nerve cranial nerve V surface of the man- opposite side is fixed dible Posterior fibers: Hearing impairment can drastically affect speech and language development in the infant and child.
In the adult, hearing is an extremely important feedback source for appropriate speech sound production. It is also extremely important for many other aspects of day-to-day living, including the perception of music and other environmental sounds.
Hearing is thus a crucial function that affects many aspects of quality of life in addition to its role in speech and language.
The study of the anatomy and function of the peripheral hearing system is typically divided into three functional components: Each of these components serves a different but complementary role in the trans- duction of environmental acoustic vibrations into neural impulses sound.
The role of the external or outer ear is to capture sounds and direct them to a membrane that converts acoustic vibrations to mechanical energy. The membrane and three attached small bones and supporting muscles and ligaments in the middle ear transmit these sounds to the sensory end organ of hearing in the inner ear. They also provide an impor- tant impedance matching function between airborne sounds in the environment and fluid vibrations in the inner ear.
In the inner ear, differences in stiffness along the basilar mem- brane cause it to vibrate with the greatest amplitude at different places along its length for different frequencies of sound. This stimulates complex and delicate sensory receptors, which transduce the motion into neural activity in the auditory nerve and higher levels of the central auditory system. This chapter covers these three functional components of the peripheral hearing system—the outer ear, middle ear, and inner ear—and the central auditory pathway.
The outer ear is composed of the auricle and external acoustic auditory meatus. The middle ear is composed of the tympanic cavity, the middle ear ossicles, and the middle ear muscles. The inner ear is composed of the cochlea and the vestibular system. Arrows indicate course of sound waves. Some animals can move their pinna extensively for additional directional selectivity.
It is composed of fibrocartilage cov- ered by skin and attached to the temporal bone by several extrinsic muscles and ligaments. Internal ligaments and muscles join auricular structures. The following are prominent surface landmarks: The lateral third is cartilage and continuous with the cartilage of the auricle. The medial two-thirds are osseous. It contains cilia and glands that produce wax ceruminous glands and oils sebaceous glands , and these keep the external acoustic meatus clean and supple.
These substances also help, in combination with the shape of the tube, to prevent foreign bodies, such as insects, from entering the canal. The resonating frequencies of the tube are such that sensitivity is increased to sounds between approximately and Hz. Tympanic Membrane, Tympanum, or Eardrum Figure The eardrum is a very thin but resilient membrane that vibrates in response to acoustic energy.
It sits obliquely at the end of the external acoustic meatus. It is approximately 10 mm in diameter and its shape is almost circular; its thickened outer ring annulus attaches to a groove in the tympanic cavity tympanic sulcus.
The normal appearance of the tympanic membrane e. The process of the malleus can be seen extending toward the superior border. The tympanic membrane has the following three layers: The outer cutaneous layer is a thin layer continuous with the lining of the external acoustic meatus. The middle fibrous layer is more substantial and composed of circular and radial fibers.
It is deficient at the superior border, which creates the pars flaccida. The rest of the membrane is the pars tensa. The internal mucous layer is continuous with the lining of the middle ear cavity. It is formed by two cavities: Epitympanic Recess The epitympanic recess is superior to the tympanic membrane. It contains the head of the malleus and most of the incus. The tegmental superior wall, or roof, is a thin plate of bone separating the tympanic cavity from the cranium and is called the tegmen tympani.
The jugular inferior wall, or floor, is a thin bone that sepa- rates the tympanic cavity from the internal jugular vein. The tympanic nerve, a branch of the glossopharyngeal nerve cranial nerve IX , passes through the floor of the tympanic cavity. The membranous lateral wall is the tympanic membrane.
The labyrinthine medial walls are the oval window fenestra vestibule and, below, the round window fenestra rotunda. Superior to the oval window passes the chorda tympani nerve a branch of the facial [VII] cranial nerve.
The carotid anterior wall separates the tympanic cavity from the carotid artery. Superiorly, a canal houses the tensor tympani muscle and, more inferi- orly, the opening of the pharyngotympanic tube connects the tympanic cavity to the naso- pharynx see later. The mastoid posterior wall on the posterosuperior border is the mastoid antrum, a sinus with several openings to the mastoid air cells.
It provides a path of direct commu- nication between air cells and the tympanic cavity, as well as a potential path for the life- threatening infection mastoiditis. Inferior to this is the pyramidal eminence, the point of emergence of the tendon of the stapedial muscle.
Lateral to this is the chordal eminence, the point of emergence of the chorda tympani nerve into the tympanic cavity. This system transmits acoustic vibrations from the tympanic membrane to the inner ear.
Cartilaginous synovial joints connect the three ossicles. It is suspended in the tympanic cavity by three ligaments; the most significant is the anterior ligament of the malleus. The manubrium handle is attached to the tympanic membrane. The tendon of the tensor tympani muscle see later attaches to the upper portion of the manubrium. It is suspended from the tympanic cavity by the posterior ligament of the incus.
Its footplate attaches to the oval window of the cochlea by the annular ligament. The tendon of the stapedial muscle is attached to the neck of the stapes. Middle Ear Muscles see Figure ; see also Figure [p. Its tendon enters the tympanic cavity and attaches to the manubrium of the malleus near the tympanic membrane. The tensor tympani is innervated by a branch of the mandibular division of the trigeminal nerve cranial nerve V.
Its tendon emerges from the pyramidal eminence to insert on the posterior surface of the neck of the stapes. The stapedial muscle is innervated by the nerve to stapedius of the facial nerve cranial nerve VII. Reflex activation may provide some sound protection benefits against intense, low-frequency sounds below 1 to 2 kHz.
Protection against rapid-onset sounds is minimal because of reflex delays ap- proximately 60 to ms. Activation may reduce sensitivity to self-generated vocalizations transmitted to the cochlea via bone conduction. The acoustic reflex AR activation of the middle ear muscles is a diagnostic tool used in the practice of audiology to assess the function of middle ear and higher-order neural processes involved in hearing. The lateral portion is osseous, and the medial portion is composed of cartilage and other connective tissue.
The pharyngotympanic tube is normally closed by elastic recoil forces and potentially by tension provided by muscles such as the salpingopharyngeus to protect the middle ear from pathogens. The tube opens during swallowing and yawning, principally by action of the tensor veli palatini with potential contributions from the levator veli palatini and tensor tympani muscles.
It equalizes pressure between the middle ear and external atmospheric pressure and allows the tympanic membrane to operate efficiently in a variety of atmospheric pres- sures.
This tube also drains the middle ear cavity and aerates tissues. The pharyngotym- panic tube is shorter and more horizontally placed in children and thus provides a more direct path for middle ear infections such as otitis media. Cochlea and Vestibular System The inner ear is composed of the organs of hearing and equilibrium. Osseous or Bony Labyrinth Figures , [p. It contains the vestibule, the semicircular canals, and the coiled cochlea and is composed of tissue denser than the surrounding temporal bone.
Semicircular Canals The semicircular canals are the lateral-most portion of the bony labyrinth. Superior, posterior, and lateral canals are oriented approximately orthogonally. They are involved in balance and body orientation. Vestibule The vestibule is interposed between the cochlea and the semicircular canals.
The oval win- dow is the entrance to the cochlea and point of attachment of the footplate of the stapes. Cochlea The cochlea is the medial-most portion of the bony labyrinth. This cavity is approximately 35 mm long and coiled around a central core of bone called the modiolus. Small perforations in the modiolus and projecting shelf osseous spiral lamina allow passage of auditory nerve fibers that innervate the sensory end organs of hearing.
The round window has a membranous covering that provides a point of expansion for fluid movements within the cochlea. Details are provided for the membranous cochlea. Membranous Cochlear Labyrinth The membranous cochlear labyrinth is a spirally arranged tube approximately 33 mm long and suspended in the osseous cochlea. The cochlear labyrinth includes three canals. The scala vestibuli is the only canal in direct contact with the vestibule thus its name.
The scala media, or cochlear duct, is enclosed between the scala vestibuli and scala tympani and contains the sensory end organ of hearing, the organ of Corti. The scala media contains endolymph, and the scala vestibuli and scala tympani contain perilymph.
It joins the basilar membrane at the helicotrema at the apex of the cochlea. This membrane divides the scala vestibuli from the scala media.
Basilar Membrane Figures [p. It divides the scala media from scala tympani. Although the cross-sectional area of the bony labyrinth, or canal, becomes smaller as the apex is reached, the basilar membrane becomes wider. Thus the basilar mem- brane is wider and more flaccid at the apical end and narrower and stiffer at the base, and this influences its resonant properties and frequency-response characteristics.
Sitting on the basilar membrane is the organ of Corti, which contains hair cells sensory cells and supporting cells. Inner Hair Cells. Approximately 40 stereocilia ciliated tops of the hair cells on each cell are arranged in parallel rows of decreasing height toward the modiolus. Outer Hair Cells. Approximately stereocilia per hair cell are arranged in the form of a V or W, with the base of the letter pointing toward the spiral ligament and with decreasing height toward the modiolus side.
Tectorial Membrane. Tips of the tallest row of outer hair cell stereocilia are in contact with the tectorial mem- brane, which extends over hair cells from the spiral limbus. Supporting Cells. A delicate reticular lamina holds the tops of the hair cells in place and allows for shearing forces on the stereocilia by the tectorial membrane.
Note the scala media and cochlear nerve fibers. These eighth cranial nerve afferents convey information from the cochlea to the central nervous system. Bipolar cells have their cell bodies in the spiral ganglion in the modiolus and send one process to synapse on the hair cells and a longer process axon to the cochlear nuclei.
The process innervating the hair cells passes underneath the cells through openings in the spiral lamina called habenula perforata. There are two types of cochlear afferents, as follows: Inner radial, or type I, fibers 2. Each inner radial cell goes to 1 inner hair cell, but each inner hair cell receives approximately 20 inner radial fibers; this is referred to as many to one innervation. For years, this book has remained the top choice for students and as well as teachers for studying anatomy.
Carlos Machado. High-definition and visual region-by-region coverage of challenging and intricate anatomical structures make studying anatomy not only fun but highly productive as well. This exciting and innovative new feature offers additional support to students who are curious and crave for a more in-depth understanding.
With Student Consult, the students are able to access self-assessment exercises, dissection videos, regional MCQs, illustrated axial cross-sections and additional plates from previous editions thus making the overall reader experience more rewarding and enlightening.
Frank H. Netter, born in New York in — was a gifted genius.