Cartilage Flashcards
What are the main functions of cartilage?
Semi-rigid support to many specific cells
Shock absorber
Protects ends of bones
Ligaments provide:
stability of joints and connect bone to bone
Tendons provide:
Strong, flexible connects between muscle and bones
Where does the skeletal system originate from ?
undifferentiated mesenchymal cells that can differentiate into various cell types: bone, fibrous tissue
Where is differentiation and maturation most advanced?
at the center of mass of growing cartilage; immature at periphery (perichondrium)
Completion of growth of cartilage mass consists of…
chondrocytes embedded in a large amount of extracellular matrix
What happens at the periphery of the mature cartilage?
There is a zone of condensed CT (perichondrium), containing elongated fusiform cells that resemble fibroblasts. These cells give rise to chondroblasts
When is cartilage avascular?
In adult, though young animals have blood vessels in growing cartilage
What type of tissue does cartilage support?
Soft tissue
Composed of cells (chondrocytes) that are embedded in an amorphous gel-like substance and connective tissue fibers, making this tissue resilient
Why is important for cartilage to support soft tissue?
For longitudinal bone growth – endochondral ossification
What are the stages of chondrogensis?
a = embryonic mesenchyme
b= proliferation and early differentiation
c = chondroblasts separate from each other due to production of matrix
d = multiplication of cartilage cells in aggregates
Isogenous group
cluster of chondrocytes formed through the division of a progenitor cell; found in hyaline cartilage, elastic cartilage, and fibrocartilage
What is endocondral ossification?
cartilage in physes matures, dies, mineralized and forms scaffold to form bone – longitudinal growth of bones
Primary ossification centers form first at epiphyses
Growth plate (physis)
- Zone of reserve/resting cells
- Zone of proliferation
- Zone of hypertrophic cells
B. Primary spongiosa - bone forms on dead mineralized cartilage “scaffold”
What are the type of cartilage based on?
the amount of collagen or elastic fibers present in the extracellular matrix as well as the presents of GAGs
What are the types of cartilages
- Hyaline
- Elastic
- Fibrocartilage
Describe Hyaline cartilage
Most abundant cartilage
Location: growth plates = physes
Articular cartilage covers joint surfaces at costochondral junctions of the ribs, the nasal septum, larynx, tracheal rings and bronchi
Fetal axial and appendicular skeletal
Perichondrium: presented
Describe Elastic Cartilage
Perichondrium, chondroblasts and chondrocytes in large lacuna
Elastic fibers stain dark
Flexible due to the presence of numerous bundles of branches in elastic fibers in cartilage matrix
Location: Ear pinna (external auditory), epiglottis, the corniculate and cuneiform processes of the arytenoid cartilage
Describe Fibrocartilage
Lacks a perichondrium - therefore does not have the capacity to regenerate
Contains chondrocytes and lacunae and type 1 collagen fibers
Features are intermediate between cartilage and dense fibrous connective tissue
Location: where support and tensile strength are required: Intervertebral discs (annulus fibrosus) menisci, insertions of tendons and ligaments, mandibular symphysis, pubic symphysis
What is the matrix of cartilage
composed of collagen, elastic fibers, proteoglycans (GAGs)
Outer layer of perichondrium
the outer layer is composed of dense fibrous CT; resembles mature fibroblasts.
the inner layer of perichondrium
The inner layers is cellular and it is presented in all hyaline cartilage EXCEPT on articular surfaces → inner layer: is chondrogenic, contains cell with the capacity to become chondroblasts (can regenerate) BUT not present in articular cartilage
What is the reason for the cartilage matrix to be so basophillic
due to the high concentrations of GAGs `
What are the importance of GAGs
Bound to a protein core form macromolecules called proteoglycans that are responsible for strong and flexible property of cartilage → shock absorption (increase ground substance)
Give rise to different types of cartilage
What is territorial
the matrix near the clusters of chondrocytes more basophilic due to the greater amount of GAG than the matrix further away from the chondrocytes (interterritorial)
The tissue surrounding chondrocytes (cells which produce cartilage)
What is (interterritorial)
The matrix further away from the chondrocytes
the matrix that occupies the majority of space between chondrocytes
Chondroclasts
breakdown/absorption of cartilage
Chondrocytes
mature cells embedded in cartilage matrix within lacunae
Chondroblasts
Deposit cartilage matrix
What is tendon primary composed of?
primarily composed of type 1 collagen (elastic and strong)
Parallel bundles of type 1 collagen fibers in tendon
Mature tendon?
Mature tendon cells have a limit ability to regenerate:
Following injury, a tendon lays down type III collagen → stronger than type I but stiffer and less elastic → makes it less flexible and prone to re-injure when the animal begins to stretch the tendon during strenuous work
What are the types of joint?
Fibrous joints (Synarthroses)
Cartilaginous (Amphiarthrosis)
Synovial (Diarthrosis/true joints)
What is Fibrous joints (Synarthroses)
Bones or cartilage united by fibrous tissue suture (cranial), Syndesmosis (tibia-fibia)
Gomphosis (tooth socket)
What is Cartilaginous (Amphiarthrosis)
unites cartilage and bone by hyaline cartilage or fibrocartilage
What is Synovial (Diarthrosis/true joints)
units two bone ends and are covered by articular cartilage and surrounded by a thick articular capsule
Bone surface is covered by
hyaline cartilage (articular cartilage)
What is the articular surface?
should be smooth; formed by type II collagen and proteoglycans; avascular → limited capacity for repair + nourish from synovial fluid
What is the articular capsule?
thick sac of connective tissue that covers the entire joint and provide additional joint stability
What is the synovial membrane
thin membrane with lots of vili superficial lined by a continuous layer of specialized cells
What are the type of cells found in the synovial membrane
Type A and Type B cells
What are type A cells of the synovial membrane
Phagocytic function - remove debris
What are the type B cells of the synovial membrane
secrete hyaluronic acid & protein complex (mucin) into synovial fluid = lubricant, protectant + nutrition to joints
What is synovial fluid?
clear, viscous, colorless or slightly yellow fluid produced by synoviocytes (low cellularity and low protein content); function is to reduce friction; increases in many joint diseases (effusion)
What is lacunae
Lacunae are spaces in which bone cells are present. The main purpose of a lacuna in bone or cartilage is to provide a home for the cells it contains while also keeping them alive and functional. In bones, lacunae encase osteocytes; in cartilage, lacunae enclose chondrocytes.
