EAR-II.pptx Introduction_to_the_CVS. Introduction_to_the_CVS.

Introduction_to_the_CVS.Introduction_to_the_CVS.Introduction_to_the_CVS.Introduction_to_the_CVS.

1. EAR - II P r e s e n t e d b y : - D r . Kishan Singh A ss t. P r o f e ss o r De pa r t m en t o f A na t o m y 30 - 7-2020

2. COMPETENCIES AN40.2: Describe & demonstrate the boundaries, contents, relations and functional anatomy of middle ear and auditory tube AN40.4: Explain anatomical basis of otitis externa and otitis media

3. L e ss o n Plan Middle Ear: Introduction C o m m u ni ca t i o n s Contents Subdivisions Boundaries: Roof Floor Anterior Wall Posterior Wall Medial Wall Lateral Wall

4. Middle Ear

5. Introduction Middle ear is slit-like air filled cavity within the petrous part of temporal bone . Shape- Cuboid which is compressed from side to side. In coronal section- biconcave disc like.

6. Communications Anteriorly- With Nasopharynx through Pharyngotympanic tube. Posteriorly- With Mastoid antrum through aditus to mastoid antrum.

7. C o n t e n ts Outside the mucosa: Ear Ossicles- Malleus. Incus. Stapes. Muscles- Tensor tympani & Stapedius. Nerves- Chorda tympani & Tympanic branch of Glossopharyngeal. Arteries & Veins L i g a m e n t s of e a r o s s i c l e s . Chorda Tympani Nerve

8. S ub div i s i o n s Epitympanum (Attic) Mesotympanum Hypotympanum Epitympanum- A part above the tympanic membrane. It contains: Head of Malleus. Body and short process of Incus. Mesotympanum- A part opposite to the tympanic membrane. It is the narowest part of middle ear. It contains: Handle of Malleus. Long process of Incus. Stapes. Hypotympanum- A part below the tympanic membrane.

9. Boundaries Roof Floor Anterior wall Posterior wall Medial wall Lateral wall

10. Boundaries of Middle Ear contd… R o o f It is formed by tegmen tympani . It separates the tympanic cavity from middle cranial fossa. Floor- It is formed by a thin plate of bone. It separates the tympanic cavity from jugular bulb. Tympanic branch of Glossopharyngeal nerve ( Jacobson’s Nerve ) pierces the floor between the jugular fossa and lower opening of carotid canal. Tympanic branch of Glossopharyngeal nerve Tympanic Plexus F L O O R Internal Carotid Artery Internal Jugular Vein

11. T e g men T y m p a n i

12. A nt e r i o r W all It is formed by a thin plate of bone. Its lower part separates the tympanic cavity from Internal Carotid Artery. Its upper part has two canals : Upper one for the Tensor tympani muscle . Lo we r o n e f o r t h e A ud i t o r y t ub e. Bony partition between the two canals extends backwards along the medial wall of tympanic cavity and called Processus Cochleariformis. ANTERIOR WALL P- Processus Cochleariformis

13. P o s t e r i o r W a l l This wall separates the tympanic cavity from mastoid antrum and mastoid air cells. It p r ese n t s f o l l o wi n g f e a t u r es: Aditus-ad-antrum Fossa Incudis Pyramid Vertical part of facial canal P o s t e r i o r c a n a l i c u l u s f o r c h o r d a t y m p a n i n e r v e. Aditus-ad-antrum- It is present in the upper part. T h r o ug h t h is t y m p a n ic c a v i t y c o mm un i c at es wi t h t h e mastoid antrum. Fossa Incudis- It is a small depression close to the aditus-ad-antrum. It lodges the short process of Incus . POSTERIOR WALL

14. P o s t e r i o r W a l l c o n t d … Pyramid- It is a hollow, conical bony projection below the aditus-ad-antrum. It contains the Stapedius muscle. Vertical part of Facial canal- It is present behind the pyramid. Posterior canaliculus for chorda tympani nerve- It is a small aperture for emergence of chorda tympani nerve. POSTERIOR WALL T e ndo n of Stapedius Vertical part of Facial Canal

15. Me d ia l W all It separates the middle ear from internal ear. It presents the following features: Promontory Oval Window (Fenestra vestibuli) Round Window (Fenestra cochleae) Sinus Tympani. Prominence of oblique part of Facial canal Prominence of Lateral semicircular canal of internal ear MEDIAL WALL

16. Promontory It is a rounded prominence in the centre of medial wall. It is produced by basal turn of cochlea. Tympanic branch of Glossopharyngeal nerve ( Jacobson’s nerve ) ramify on it to form tympanic plexus.

17. Medial Wall contd… Oval Window (Fenestra Vestibuli)- It is an oval aperture located above and behind the promontory. It is closed by base (footplate) of stapes and annular ligament. Round Window (Fenestra Cochleae)- It is a small, round opening below and behind the promontory. It is closed by secondary tympanic membrane. Secondary tympanic membrane separates the middle ear from scala tympani.

18. Me di a l W all c o n t d … Sinus Tympani- It is a depression behind the promontory between oval and round window. It indicates the position of ampulla of posterior semicircular canal. Prominence of oblique part of Facial canal- It is present above the oval window. Prominence of Lateral semicircular canal of internal ear- It is a small ridge high up in the angle between medial and posterior walls. S- Sinus Tympani O-Oval Window

19. L a t e r a l W all Most of the lateral wall is formed by tympanic membrane . Chorda tympani nerve passes across the tympanic membrane, lateral to the long process of Incus and medial to the handle of Malleus. Chorda tympani nerve enters the tympanic cavity through the posterior canaliculus. Chorda tympani nerve leaves the tympanic cavity through the anterior canaliculus. LATERAL WALL