Histology: Structure of Joints Flashcards
What type of cartilage are joints composed of?
hyaline cartilage
What role does the specialized hyaline cartilage have?
1) shock absorber
2) provides a lubricated surface for movable joints
What part of what cartilage acts as a shock absorber and lubricant?
the extracellular matrix of hyaline cartilage
What is lubrication fluid made out of?
- hyalurnic acid
- immunoglobulins
- lysosomal enzymes
- collagenase
- glycoproteins
What structure produces lubrication fluid?
the synovial lining of the joint capsule
How can one diagnose joint disease?
through the analysis of synovial fluid
What is articular cartilage?
Hyaline cartilage that covers articular surfaces of movable joints.
What is the name of hyaline cartilage that covers articular surfaces of movable joints?
Articular cartilage
What is the structure like of articular cartilage?
similar to hyaline cartilage, but the free surface does NOT have PERICHONDRIUM.
What is the major difference between the structure of hyaline cartilage and articular cartilage?
free articular cartilage does NOT have perichondrium.
How is it possible to visualise articular cartilages on a bone?
An image must be taken of a young animal whose bones are still composed of hyeline cartilage.
What are the 4 articular cartilage layers?
1) superficial (tangential) zone
2) intermediate (transitional) zone
3) deep (radial) zone
4) calcified zone
5) bone
What are the key features of the first articular cartilage layer?
SUPERFICIAL (TANGENTIAL) ZONE:
- pressure resistant region
- closest to the articular surface
- contains elongated and flattened chondrocytes
- surrounded by a condensation of type II collagen fibrils
- arranged in fascicles PARALLEL to the free surface
What cells is the first articular cartilage layer made out of?
elongated and flattened chondrocytes
What are the primary cells of the first articular cartilage layer surrounded by?
- elongated and flattened chondrocytes are surrounded by a condensation of TYPE II COLLAGEN FIBRILS
How are the type II collagen fibrils arranged in the first articular cartilage layer?
in fascicles PARALLEL to the FREE SURFACE
What are the key features of the second articular cartilage layer?
THE INTERMEDIATE (TRANSITIONAL) ZONE:
- lies below the superficial zone
- contains round chondrocytes
- randomly distributed within the matrix
- collagen fibrils are less organised
- arranged in an OBLIQUE ORIENTATION to the surface
What cells is the second articular cartilage layer made out of?
intermediate (transitional) zone:
- ROUND CHONDROCYTES
how are the cells of the second articular cartilage layer arranged?
round chondrocytes are randomly distributed within the matrix
How are the collagen fibrils arranged in the second articular cartilage layer?
- intermediate transitional zone
- LESS ORGANISED
- arranged in a somewhat OBLIQUE ORIENTATION to the SURFACE
What is the third articular cartilage layer called?
deep (radial) zone
What are the key features of the third articular cartilage layer?
DEEP (RADIAL) ZONE:
- small, round chondrocytes
- arranged in short columns
- PERPENDICULAR to the free surface of the cartilage
- collagen fibrils are positioned between columns PARALLEL to the LONG AXIS of the bone
What type of cells is the third articular cartilage layer composed of?
- deep (radial) zone
small round chondrocytes
How are the cells arranged in the third articular cartilage layer?
- small round chondrocytes
- deep (radial) zone
arranged in SHORT COLUMNS PERPENDICULAR to the FREE SURFACE
How are collagen fibrils arranged in the third articular cartilage layer?
between columns PARALLEL to the LONG AXIS of the BONE.
What is the the fourth articular cartilage layer called?
THE CALCIFIED ZONE
What are the key features of the fourth articular cartilage layer?
CALCIFIED ZONE
- calcified matrix
- small chondrocytes
- seperated by a smooth, undulating, heavily calcified line (TIDEMARK)
What type of cells is the fourth articular cartilage layer made out of?
calcified zone
- small chondrocytes
How is the fourth articular cartilage layer seperated from the third articular cartilage layer?
3rd: deep (radial) zone
4th: calcified zone
seperated by a SMOOTH, UNDULIGATING, HEAVILY CALCIFIED line (TIDEMARK).
What is the name of the line that seperated the radial zone from the calcified zone? What is it composed of?
the TIDEMARK
- heavily calcified cells
What occurs above the ‘tidemark’?
proliferation of chondrocytes within cartilage lacunae,
- which provides new cells for cartilage growth.
What happens during cartilage renewal?
cells (chondrocytes) migrate from above the TIDEMARK region, towards the joint surface.
What is articular cartilage?
- hyaline cartilage
- lacking perichondrium
- not lined by the synovial membrane
What is the joint capsule composed of?
dense connective tissue with blood vessels
What is the joint capsule lined by?
(the dense connective tissue with blood vessels is lined by) a synovial membrane
What does the joint capsule feature in?
- continuous with the periosteum
- attached to the edges of the articular cartilage
What is the joint capsule attached to?
the edges of the articular cartilage
What is the synovial membrane?
a layer of vascular connective tissue covered by 1-3 layers of synovial cells.
What connective tissue is the synovial membrane made out of?
vascular connective tissue
What is vascular connective tissue in the synovial membrane covered by?
1-3 layers of synovial cells
What does the synovial membrane not have?
a basal lamina
What kind of capillaries are there in the synovial membrane?
fenestrated capillaries
What is the professional word which describes the role of synovial fluid?
capillary ultrafiltrate
What does the synovial fluid ‘capillary ultrafiltrate’ contain?
the glycoprotein LUBRICIN (produced by synovial cells)
What do synovial cells produce?
LUBRICIN
What produces lubricin?
synovial cells (fibroblasts)
What is the function of lubricin?
reduce wear to bone cartilage
What is the synovial membrane formed by?
a layer of collagenous fibers interspersed with flattened fibroblasts (synovial cells)
What is the different name for fibroblasts?
synovial cells
Where is the synovial membrane located?
- lie directly on the fibrous capsule
OR - seperated from it by connective tissue/fat
What commonly happens to the synovial membrane?What is it changed into?
it is thrown into folds (synovial villi) that project into the synovial cavity
What projects into the synovial cavity?
synovial villi
Where do synovial villi project?
into the synovial cavity
What is the synovial membrane? membrane? connective tissue? epithelium?
- a SEPECIALIZED, SECRETORY, CONNECTIVE TISSUE
neither a membrane or an epithelium
What are the two types of synovial-lining cells?
- Type-A (macrophage-like synovial cells)
- Type-B (fibroblast-like synovial cells)
What is a different name for type A synovial cells?
macrophage-like synovial cells
What is a different name for type B synovial cells?
fibroblast-like synovial cells
What are the type A synovial cells responsible for?
- macrophage-like synovial cells
- removal of undesirable substances from the synovial fluid
How many type A synovial cells are there?
take up 25% of the cells lining the synovium
What are the type B synovial cells responsible for?
- fibroblast-like synovial cells
- produce a sugar polymer called HYALURONAN and molecule LUBRICIN, which lubricates the joint surfaces.
What do the type-B synovial cells produce?
- hyaluronan
- lubricin
What is the role of hyaluronan and lubricin?
lubricate joint surfaces
What does hyaluronan trap?
water of the synovial fluid
Where is water produced in the synovial fluid?
it is not produced, it is trapped by the HYALURONAN.
What tissues are fibrous joints usually composed of?
dense regular connective tissue
What does fibrous connective tissue connect? Where?
in a fibrous joint
- fibrous connective tissue connects adjacent bones
What do bones not have between them in a fibrous joint? Why?
do not have a JOINT CAVITY
- because they are directly conected to each other by fibrous connective tissue.
Where are the intervertebral discs located?
between the adjacent vertebrae bones in the vertebral column
What do intervertebral discs allow for?
- slight movement of the vertebrae
What is the function of intervertebral disks?
1) act as a ligament (hold the vertebrae together)
2) function as a shock absorber for the spine
What is the intervertebral disc composed of?
center: NUCLEUS PULPOSUS
outside: ANNULUS FIBROSUS
What is the annulus fibrosus made out of?
- lamellar layers with fibrocyte-like cells (type B) and chondrocyte-like cells.
What cartilage is the annulus fibrosus made out of?
FIBROCARTILAGE
What does the nucleus pulposus contain?
clustered notochondral cells.