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Thursday, October 09, 2008

What is the type of joints between the ossicles of ear

Question 12
What is the type of joints between the ossicles of ear
a)      Fibrous Joints
b)      Primary cartilaginous
c)      Secondary Cartilaginous Joints
d)      Synovial Joints
D) Synovial Joints
Gray 38th Edition Page 1375
The articulations between ear ossicles are typical synovial joints.
Self Explanatory
The incudomalleolar joint is saddle-shaped, the incudostapedial is a ball and socket articulation. Their articular surfaces are covered with articular cartilage and each joint is enveloped by a capsule containing much elastic tissue and lined by synovial membrane.
Joints are classified as follows
I SYNARTHROSES bone—solid connective tissue—bone
1. FIBROUS JOINTS (Articulationes fibrosae)
a. Sutures: bone—collagenous sutural ligament—bone
b. Syndesmoses: bone—collagenous interosseous ligament, membrane or cord—bone(elastic fibrous tissue is occasionally prominent)
c. Gomphoses: bone—complex collagenous periodontium—dental cement
2. CARTILAGINOUS JOINTS (Articulationes cartilagineae)
a. Synchondroses: bone—hyaline cartilage—bone (Primary cartilaginous joints)
b. Symphyses: bone—hyaline cartilage—fibrocartilaginous disc—hyaline cartilage—bone (Secondary cartilaginous joints)
SYNOSTOSES: Rigid bony union; after growth has ceased this is the normal fate of synchondroses, ultimately most sutures, and some symphyses
II DIARTHROSES bone—cavitated connective tissue—bone
SYNOVIAL JOINTS bone—articular cartilage—synovial fluid in cavity—articular cartilage—bone (Articulationes synoviales) Bond: surrounding sleeve of collagenous fibrous capsule lined by synovial membrane; extrinsic and intrinsic ligaments and presence of occasional intracapsular ligaments, tendons, fat pads, fibrocartilaginous discs or menisci.
-X at0h4ily:"Courier New";mso-bidi-font-family:"Courier New"; color:black'>o       to the internal jugular via the inferior petrosal sinus and a plexus of veins on the internal carotid,
o       to the pterygoid plexus by veins traversing the emissary sphenoidal foramen, foramen ovale and foramen lacerum and
o       to the facial vein via the superior ophthalmic.
Ä     The two sinuses are connected by anterior and posterior intercavernous sinuses and the basilar plexus. All connections are valveless; the direction of flow in them is reversible.
Ä     If the question had been “Which is a tributary” then the answer is superficial middle cerebral vein
Ä     If the question had been “Which is not a connection” the answer is Deep Middle Cerebral Vein
Inferior Petrosal Sinuses drain the cavernous sinuses to the internal jugular veins. Each begins postero-inferiorly at its cavernous sinus and runs back in a groove between the petrous temporal and basilar occipital bones. Traversing the anterior part of the jugular foramen it ends in the superior jugular bulb. It receives labyrinthine veins via the cochlear canaliculus and the vestibular aqueduct and tributaries from the medulla oblongata, pons and inferior cerebellar surface. According to Browder and Kaplan the sinus is more often a plexus and sometimes drains by a vein in the hypoglossal canal to the suboccipital vertebral plexus.
Propulsion of blood in the sinus is partly due to pulsation of the internal carotid artery. It is also influenced by gravity and hence by the position of the head.

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