Cartilage and Endochondrial Ossification Flashcards
What is cartilage?
An avascular tissue that consists of an extensive extracellular matrix in which chondrocytes lie
What do chondrocytes do?
Produce and maintain the extracellular matrix
What are the three types of cartilage?
Hyaline
Elastic
Fibrocartilage
What makes up hyaline cartilage?
Proteoglycans, hyaluronic acid and type II collagen.
Hyaluronate proteoglycan aggregates are bound to the fine collagen matrix fibres.
What makes up elastic cartilage?
Hyaluronic acid, type II collagen, elastic fibres and elastic lamellae
What makes up fibrocartilage?
Abundant type I collagen fibres in addition to proteoglycans, hyaluronic acid, and type II collagen.
What cell types are present in hyaline cartilage?
Chondrocytes
How are chondrocytes found?
Singly, or if recently divided, in small clusters called isogenous groups.
How do fetal bones develop?
Hyaline cartilage is the precursor of bones which develop by endochondrial ossification.
Some remains at the articulating surface and epiphyseal plate
What covers the margin of hyaline cartilage?
Perichondrium
Contains many fibroblast like cells that develop into chondroblasts and later chondrocytes
What is the perichondrium?
A dense connective tissue
What is appositional growth?
Fibroblast like cells of the perichondrium develop into chondroblasts. These secrete matrix components and develop into chondrocytes.
What is interstitial growth?
Chondrocytes deeper in the cartilage in isogenous groups deposit further matrix and the cells separate.
What do you see histologically looking at chondrocytes?
They lie in lacunae
Does elastic cartilage calcify?
No
Where would elastic cartilage be found?
External ear (pinna), external acoustic meatus, epiglottis, Eustachian tube
What cells are present in fibrocartilage?
Chondrocytes and fibroblasts
How does fibrocartilage appear histologically?
Cells often seen in rows. No surrounding perichondrium.
Where is fibrocartilage often found?
Intervertebral discs
Articular discs of the sternoclavicular and temporomandibular joints
Menisci of the knee
Pubic symphysis
What is the synovial joint?
A movable joint in which the juxtaposed bone ends:
Are covered by hyaline cartilage or fibrocartilage
Lie within lubricating synovial fluid, bound by joint cavity lined by synovial membrane and reinforced
(Fibrous tissue and ligaments)
What secretes the synovial fluid?
Fibroblast-like cells
What removes debris from the joint space of the synovial joint?
Macrophages
