Anatomy of the external and middle ear
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The document provides information on the anatomy of the external and middle ear. It discusses the development of the external ear, auricle, external auditory canal, tympanic membrane, and ossicles from pharyngeal arches. It then describes the structures and walls that make up the middle ear cleft, including the tympanic cavity, eustachian tube, and mastoid air cells. Key structures like the ossicles, nerves, muscles, and mucosal folds within the middle ear are also outlined.
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Anatomy of the external and middle ear
- 1. ANATOMY OF THE EXTERNALANATOMY OF THE EXTERNAL AND MIDDLE EARAND MIDDLE EAR DR. SHWETA SHARMA Moderator : DR. KANWAR SEN
- 3. DEVELOPMENT
- 4. EXTERNAL EAR - Auricle 6 Hillocks of His
- 5. EAC & MIDDLE EAR1st pharyngeal pouch endoderm forms: Lining of middle ear (tympanic cavity) Connection to pharynx elongates and forms eustachian tube
- 6. • Tympanic Membrane – Inner layer endoderm – Middle layer mesoderm – Outer layer ectoderm
- 7. 1st and 2nd pharyngeal arch cartilage (mesoderm) --> ossicles • 1st (Meckel’s): epitypanum Part of ossicles – Head of malleus, body and short process of incus • 2nd (Reichert’s): mesotympanum part of ossicles – Long process malleus, long process incus, stapes superstructure • Stapes footplate: otic capsule Ossicles full sized by 15 weeks Ossify by 25 weeks
- 13. EXTERNAL AUDITORY CANAL •“S” shaped , 2.4cm LATERAL 1/3 CARTILAGE •Inwards, slightly downwards & forwards ₦ •8mm MEDIAL 2/3 BONE •1.6mm •Narrower •Tympanic sulcus •Roof •Suture line •Constrictions •maturation
- 14. GLANDS • Ceruminous glands = modified apocrine glands • Sebaceous gland = oily material (sebum) of their fat containing cells • EAR WAX ??? • INHERITANCE ??? • Is it normal if found on upper portion of tympanic membrane?
- 15. Blood supply: •Outer part by superficial temporal and posterior auricular arteries. •Inner part by deep auricular branch of maxillary artery. Lymphatic drainage: • Preauricular, postauricular and superficial cervical lymph nodes. Nerve supply: • Anterior by auriculotemporal nerve & greater auricular (c2, c3) and posterior half by auricular branch of vagus & twig from facial nerve. 2’, 5’, 8’, 11’o clock
- 17. MIDDLE EAR CLEFTMIDDLE EAR CLEFT • TYMPANIC CAVITYTYMPANIC CAVITY • EUSTACHIAN TUBEEUSTACHIAN TUBE • MASTOID AIR CELLSMASTOID AIR CELLS
- 18. TYMPANICTYMPANIC CAVITYCAVITY •Roughly cuboidal •Roof is wider than floor •Anterior wall narrower than posterior •Medial and lateral wall bear their convexities
- 19. LATERAL WALL • Scutum ₦ • Anterior canaliculus • Chorda tympani
- 20. TYMPANIC MEMBRANE 9-10 mm 8-9 mm • Notch of rivinus, Malleolar folds, Pars flaccida, Pars tensa
- 21. • Layers • Lamina propria of pars tensa • Maturation/cell division About 55 degrees
- 22. Three recess • Anterior • Posterior • Prussak’s pouch (above lateral processs of malleus and b/w neck of malleus and pars flaccida)
- 23. ROOFROOF • TEGMEN TYMPANI Petrous & squamous temporal bone ₦
- 24. FLOORFLOOR • Variations • Tympanic branch of gloossopharyng eal nerve pierces between the jugular fossa and lower opening of the carotid canal
- 25. Anterior wall • Upper part • Lower part
- 26. Coronal section at level of long process of incus POSTERIOR WALL (MASTOID)POSTERIOR WALL (MASTOID) • Aditus • Fossa incudis • Vertical bony canal
- 27. MEDIAL WALL (LABYRINTHINE)MEDIAL WALL (LABYRINTHINE)
- 29. Fallopian canal and processus cochleariformis promontory
- 30. FACIAL RECESS
- 31. At level of pyramid where facial recess is deep
- 32. • 3.25 mm long and 1.75 wide. • Kidney shaped Fenestra vestibuli/ovalis
- 33. Fenestra cochleae / rotunda • 2.3 X 1.9 mm • A plane at right angle to stapes footplate • Closed by secondary tympanic membrane
- 34. RELATIONS
- 36. OssiclesOssicles • Malleus • Incus • stapes
- 37. Malleus •Largest of three •9 mm •Amputation of head by cutting through the neck leaves CT & TT intact
- 39. Incus • Short limb connected to posterior wall
- 40. Stapes •Smallest bone in body •S. tn attaches to posterior part of neck & post. Crus. •Footplate 3mm long X 1.4mm wide •Axis almost horizontal
- 41. Joints
- 42. Chorda tympani, stapedius, tensor tympani, tympanic plexus
- 44. MUCOSAL FOLDS • Constitution ?? • Origin ?? • pathways
- 52. Mucosal folds most commonly seen 1. Tensor tympani fold 2. Lateral incudal fold 3. Medial incudal fold 4. Lateral malleolar fold 5. Stapedial fold 6. Obturator fold
- 53. EUSTACHIAN TUBE • about 36 mm • its direction is downward, forward, and medialward • forming an angle of about 45 degrees with the sagittal plane and one of from 30 to 40 degrees with the horizontal plane • It is formed partly of bone (12mm), partly of cartilage and fibrous tissue (24mm)
- 54. Base lies directly under the mucous membrane of the nasal part of the pharynx, where it forms an elevation, the torus tubarius or cushion,behind the pharyngeal orifice of the tube.
- 55. The mastoid air cell systemThe mastoid air cell system • Petrous part of temporal bone • Development • Volume • Well pneumatised>>diploetic>>sclerotic • epithelium
- 58. RELATIONS
- 59. Thank you
Editor's Notes
- The otic placode is the first hint of a future ear and is present during the third week of intrauterine growth. The auricle emanatesfrom the mesoderm of the first and second branchial arches; its growth occurs through the development of the six hillocks of His at week 6.22 The following six structures evolve from these hillocks: (1) the tragus, (2) the helical crus, (3) the helix, (4) the antihelix, (5) the antitragus, and (6) the lobule. By week 12, the hillocks have fused. When these fuse inappropriately, a preauricular sinus tract can result. From the fifth week of gestation, three hillocks arise on the first branchial (mandibular) arch (hillocks 1, 2, and 3), and three arise on the second branchial (hyoid) arch (hillocks 4, 5, and 6) on either side of the first branchial cleft (Fig. 128.1). Hillocks 1 and 6 are the first to be identifiable separately, but by the sixth week, all are distinct. The lobule also can be identified on the second arch. By the eighth week, the auricle has an identifiable structure, and the contributions of the hillocks to the adult form can be recognized: hillock 1, tragus; hillock 2, crus helicis; hillock 3, ascending helix; hillock 4, horizontal helix, upper portion of scapha, and antihelix; hillock 5, descending helix, middle portion of the scapha, and antihelix; and hillock 6, antitragus and inferior aspect of the helix Cartilage formation begins at week 7. The concha derivesfrom the ectoderm of the first branchial groove. The upper portion forms the cymba concha, the middle portion forms the cavum concha, and the lowest portion forms the intertragal incisura. Malformation ofthe conchal bowl contributes to excessive protrusion of the pinna from the head. Additionally, the helical margin may develop separately from a skinfold caudal to hillocks 4 and 5,23 which then develops rapidly during weeks 8 through 12. Finally, the helix furls during the sixth month. The antihelix furls during weeks 12 through 16; it is the failure of it to do so that results in a protruding scapha. There is a transient obstruction of the medial canal by proliferating epithelial cells to form a meatal plug that eventually dissolves, leaving a patent canal
- surface ectoderm that covers the dorsal end of the first pharyngeal grove. A solid epithelial plate meatal plug develops at the bottom of the funnel-shaped pharyngeal groove.
- CONCHA DIDVIDED TO CYMBA AND CAVUM
- The auricle receives its blood supply from three arteries: the superficial temporal, the posterior auricular, and the occipital. The venous system involves the posterior auricular, external jugular, superficial temporal, and retromandibular veins. The lymphatics of the ear drain anteriorly to the parotid lymph nodes and posteriorly to the cervical lymph nodes. The innervation of the auricle is via cranial nerve VII, with the temporal branch supplying the anterior and supe-rior auricularis muscles, and the posterior auricular branch supplying the posterior auricularis muscles. The sensory innervation is primarily from the lesser occipital nerve, the mastoid branch of the lesser occipital nerve, the greater auricular nerve (C2, C3), and the auricular temporal nerve. The Arnold nerve, a branch of cranial nerve X, supplies the concha.
- Upper two third of lateral surface auriculotemporal nerve and lower one thirds by greater auricular nerve. • Medial surface upper two third by lesser occipital nerve and lower one third by greater auricle nerve. • Root of auricle by is supplied by branches of facial nerve.
- Although tympanic bone makes greater part of the canal and also carries the sulcus, the squamous bone forms the roof. Therefore there r two suture lines tympanosquamous anteriorly and tympanomastoid posteriorly…. Closely adherent skin can be a challenge here in raising tympanomeatal flap tympanomastoid is a complex suture line between anterior wall of mastoid process, a portion of squamous boneand tympanice bone.
- Ceruminous glands = modified apocrine glands produces watery, white secretion that slowly darkens turning semi solid and sticky as it dries Sweat glands so stimulated by adrenergic drugs and fever and emotion Sebaceous gland produce oily material sebum of their fat containing cells Inheritance has wet and dry types (ABCC11) Dry (AA) lacking cerumen yellowish grey and brittle Wet (GG and GA) is brownish and sticky Dominant = wet
- The tympanic membrane viewed from middle ear left Chorda tympani crosses the medial side of handle of malleusat the junction of pars flaccida and pars tensa
- Oval shape Angle 55 degrees, newborns its horizontal so child can tolerate noisy sound better Random division within cells but central boundary made by handle of malleus extending half way through creates outwards migration good forr graft bad forcholesteatoma formation if the membrane enters the middle ear
- From superior limits of the sulcus, the annulus becomes a fibrous band which runs centrally forming anterior and posterior malleolar folds to the lateral process of malleus
- Persistent petrosquamous suture line
- Cranial margin of juglar bulb extends over inferior surface of bony annulus
- Upper part two parallel canals… upper canal for tensor tymapni muscle and lower for auditory tube
- Sinus tympani is a posterior extension of the mesotympanum and lies deep to promontory and facial nerve Position of ampulla of posterior semicircular canal Apex of cochlea Ask about the white thing
- Processus chocleaformis marks anterior portion of the intratympanic portion of facial nerve. PC, a curved projection of bone, concave anteriorly, which houses the tendon of tensor tympani as it runs laterally to handle of malleus
- LPM, PLP
- Mandibular nerve by supply to medial pterygoid TTT
- Mucus secreting, repiratory type, cilia bearing, three distinct pathways, epitympanic, promontarial, hypotympanic ( largest)…. Three caolesce at eustachian tube..tympanic orifice Mucosa covers tendons and ossicles
- Development of mucosal folds Saccus anticus Ant pouch von troltsch Supra tubal recess Saccus medius Ant saccule
- Nonciliated epithelium without goblet cells/ mucus glands
- Medial wall : posterior semicircular canal and more deeply dura of post cranial fossa and endolymphatic sac