Difference between revisions of "Joints - Anatomy & Physiology"
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− | + | <big><center>[[Musculoskeletal System - Anatomy & Physiology|'''BACK TO MUSCULOSKELETAL ANATOMY AND PHYSIOLOGY''']]</center></big> | |
− | + | Joints comprise broadly two categories: | |
− | + | *'''Synarthroses''' form joints that are relatively rigid | |
− | Joints broadly | + | *'''Diarthroses''' form joints that are freely movable |
+ | Joint Function: | ||
+ | *Absorb force of impact, transfer force via cartilage to bone | ||
+ | *Allow a variable degree of movement | ||
− | + | =='''Fibrous Joints'''== | |
+ | *Most occur in the skull: known as '''sutures''' | ||
+ | **Key in development: allow extension of individual bones during growth | ||
+ | **Gradually eliminated as ossification progresses | ||
+ | *'''Syndesmoses''': facing areas of two bones joined by connective tissue ligaments, very limited movement allowed | ||
+ | **Eg. Joints of the metacarpus in the horse | ||
+ | *'''Gomphosis''': attachment of tooth to bone within its socket | ||
− | + | =='''Cartilaginous Joints'''== | |
+ | *'''Synchondroses''': eg. joints between epiphyses and diaphyses of juvenile long bones, disappear on maturity | ||
+ | **Permanent synchondroses: the joint between the skull and '''hyoid''' | ||
+ | *'''Symphysis''': articulating bones are divided by a succession of tissues, with cartilage covering the bones or the tissue between | ||
+ | **Eg. mandibular, pelvic, vertebral | ||
+ | **Fibrocartilagenous joints | ||
+ | ***Form major union between vertebrae, except first two cervical vertebrae | ||
+ | ***''Nucleus pulposus'' is position eccentrically within ''annulus fibrosis'' | ||
+ | ***Vertebrae in thoracic region have '''conjugal ligaments''' | ||
+ | ****Extend from rib to rib on opposite sides | ||
+ | ****Strenghten the area over the discs | ||
− | + | =='''Synovial Joints'''== | |
+ | *Articulating joints are separated by a fluid-filled joint cavity, which is bounded by a synovial membrane | ||
+ | **Synovial membrane: pink connective tissue sheet, vascular and sensitive | ||
+ | ***Can be unsupported (membrane may pouch, allowing remote access), resting on an outer fibrous capsule, or separated from capsule by pads of fat | ||
+ | ***No continuous covering of cells | ||
+ | ***Where cells exist, they produce lubricant (aminoglycans) of synovial fluid | ||
+ | **Synovial fluid: Nourishes and lubricates [[Joints - normal#Articular cartilage|articular cartilage]] | ||
+ | ***Derived from synovial membrane cells and blood plasma | ||
+ | ***Normal amount in canine joint - 0.01 - 1.0 ml; possible in equine/bovine: 20-40mL | ||
+ | ***Transparent to light yellow (horses) | ||
+ | ***Usually very thick due to high hyaluronic acid, forms strands | ||
+ | ***Windrowing of cells on smear | ||
+ | ***Normal protein < 25g/l (all species) | ||
+ | ***Normal cell count: Large mononuclear cells, <12% neutrophils, <11% lymphocytes | ||
+ | ****Small animals - < 3 x 10e9/L | ||
+ | ****Horses - < 0.5 x 10e9/L | ||
+ | ****Cows - < 1 x 10e9/L | ||
+ | *Often the synovial membrane is reinforced by a fibrous capsule and ligaments restricting joint movement and providing stability | ||
+ | **Outer fibrous layer | ||
+ | ***Encloses bone and muscle insertions within joint capsule | ||
+ | ***Supplied by blood vessels and nerve endings | ||
+ | **Inner synovial layer | ||
+ | ***Covers surfeces except for [[Joints - normal#Articular cartilage|articular cartilage]] | ||
+ | ***Very thin | ||
+ | ***Has surface projections - villi | ||
+ | *Articular cartilage covers the articular surfaces | ||
+ | **Usually, this is [[Bones and Cartilage - Anatomy & Physiology#Structure and Function of Cartilage|Hyaline]], although [[Bones and Cartilage - Anatomy & Physiology#Structure and Function of Cartilage|Fibrocartilage]] or fibrous tissue can substitute | ||
+ | [[Image:Normal joint cartilage.jpg|right|thumb|100px|<small><center>Normal joint cartilage (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]] | ||
+ | **Articular cartilage is avascular and insensitive | ||
+ | ***Nutrients via diffusion from synovial fluid and nearby vessels (adjoining tissue and marrow cavities) | ||
− | + | **Limited response to injury, Little repair capacity | |
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− | + | *In large animals - normal bilaterally symmetrical depressions on the surface | |
− | + | *Obtains nutrition from [[Joints - normal#Synovial fluid|synovial fluid]] and less so from subchondral vessels | |
− | + | Microscopically, surface has depressions - for synovial fluid? | |
− | + | *In young animals overlies [[Bones - normal#Bone development|epiphyseal cartilage]] | |
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==Links== | ==Links== | ||
− | + | *[[Joints|Joint Pathology]] | |
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Revision as of 11:38, 18 July 2008
Joints comprise broadly two categories:
- Synarthroses form joints that are relatively rigid
- Diarthroses form joints that are freely movable
Joint Function:
- Absorb force of impact, transfer force via cartilage to bone
- Allow a variable degree of movement
Fibrous Joints
- Most occur in the skull: known as sutures
- Key in development: allow extension of individual bones during growth
- Gradually eliminated as ossification progresses
- Syndesmoses: facing areas of two bones joined by connective tissue ligaments, very limited movement allowed
- Eg. Joints of the metacarpus in the horse
- Gomphosis: attachment of tooth to bone within its socket
Cartilaginous Joints
- Synchondroses: eg. joints between epiphyses and diaphyses of juvenile long bones, disappear on maturity
- Permanent synchondroses: the joint between the skull and hyoid
- Symphysis: articulating bones are divided by a succession of tissues, with cartilage covering the bones or the tissue between
- Eg. mandibular, pelvic, vertebral
- Fibrocartilagenous joints
- Form major union between vertebrae, except first two cervical vertebrae
- Nucleus pulposus is position eccentrically within annulus fibrosis
- Vertebrae in thoracic region have conjugal ligaments
- Extend from rib to rib on opposite sides
- Strenghten the area over the discs
Synovial Joints
- Articulating joints are separated by a fluid-filled joint cavity, which is bounded by a synovial membrane
- Synovial membrane: pink connective tissue sheet, vascular and sensitive
- Can be unsupported (membrane may pouch, allowing remote access), resting on an outer fibrous capsule, or separated from capsule by pads of fat
- No continuous covering of cells
- Where cells exist, they produce lubricant (aminoglycans) of synovial fluid
- Synovial fluid: Nourishes and lubricates articular cartilage
- Derived from synovial membrane cells and blood plasma
- Normal amount in canine joint - 0.01 - 1.0 ml; possible in equine/bovine: 20-40mL
- Transparent to light yellow (horses)
- Usually very thick due to high hyaluronic acid, forms strands
- Windrowing of cells on smear
- Normal protein < 25g/l (all species)
- Normal cell count: Large mononuclear cells, <12% neutrophils, <11% lymphocytes
- Small animals - < 3 x 10e9/L
- Horses - < 0.5 x 10e9/L
- Cows - < 1 x 10e9/L
- Synovial membrane: pink connective tissue sheet, vascular and sensitive
- Often the synovial membrane is reinforced by a fibrous capsule and ligaments restricting joint movement and providing stability
- Outer fibrous layer
- Encloses bone and muscle insertions within joint capsule
- Supplied by blood vessels and nerve endings
- Inner synovial layer
- Covers surfeces except for articular cartilage
- Very thin
- Has surface projections - villi
- Outer fibrous layer
- Articular cartilage covers the articular surfaces
- Usually, this is Hyaline, although Fibrocartilage or fibrous tissue can substitute
- Articular cartilage is avascular and insensitive
- Nutrients via diffusion from synovial fluid and nearby vessels (adjoining tissue and marrow cavities)
- Articular cartilage is avascular and insensitive
- Limited response to injury, Little repair capacity
- In large animals - normal bilaterally symmetrical depressions on the surface
- Obtains nutrition from synovial fluid and less so from subchondral vessels
Microscopically, surface has depressions - for synovial fluid?
- In young animals overlies epiphyseal cartilage