12 - Cartilage and Bone Flashcards
What is cartilage?
Avascular connective tissue that consists of chrondocytes and a semisolid extracellular matrix
What are the three types of cartilage and what are their extracellular matrixes made of?
All matrix have proteoglycan and hyaluronic acid
- Hyaline: Type II Collagen aggregates to 100 hyaluronate proteoglycan
- Elastic: Elastic fibres and elastic lamellar
- Fibrocartilage (Fibrous): Mainly Type I collagen
Where is hyaline cartilage found?
- Trachea
- Layrnx
- Articular at joints
- Nose
- Costal cartilage
- Epiphyseal growth plates
- Foetus
What is the structure and function of hyaline cartilage?
Structure:
- Avascular
- Perichondrium on edges.
- Perichondrocytes differentiate into chondroblasts then chondrocytes, which sit in lacuna.
- Isogenous groups.
- Chondrocytes separate as they release extracellular matrix.
Function:
- Xcell matrix is full of water. Water non-compressible so resilient to increased loads.
What is the function of cartilage?
- Resilient
- Firm
- Flexible
- Strength
Fibres, Water and Ground substance make up xcellular matrix that give cartilage it’s properties. Allows Articular joints to slide over each other
How does cartilage get nutrients?
Cartilage avascular. Nutrients have to diffuse from vessels in the perichondrium to the extracellular matrix.
What is a proteoglycan?
Make up ground substance. Core protein with GAG covalently bound.
What is GAG?
Glycosaminoglycans. Long chained poly-saccharides. They attract water to form hydrated gel that permits rapid diffusion but resists compression
What GAG is predominantly found in cartilage?
Hyaluronate. Binds to core protein to form proteoglycan that is massively hydrophilic, attracts water to form gel.
Why is the extracellular matrix of cartilage more gel-like than other connective tissues?
Contains more proteoglycan so in ground substance
What cartilage is present in the trachea and why?
Hyaline (below submucosa). Reinforces trachea to protect and maintain airway
When does cartilage repair itself?
It doesn’t, chondrocytes cannot divide. Fibroblasts replace cartilage with fibrous scar tissue
Where is elastic cartilage found?
- Pinna of ear
- Eustachian tube (inner ear to oral)
- Epiglottis
What is the function of the elastic cartilage?
Areas that need extra flexibility and support
What is the structure of elastic cartilage?
Perichondrium containing fibroblasts. Lots of chondrocytes surrounded by dense elastin fibres. ‘Gaps’ where chondrocytes have laid down their elastic and died.
Where is fibrocartilage found?
- Pubic symphysis
- Intervertebral disc
- Knee menisci (padlike cartilage)
- Articular joint of sterniclavicular and temporomandibular
What is the function of fibrocartilage?
Found in areas of directional stress, so shock absorbs and resists shearing forces.
What is the structure of fibrocartilage?
- Few chondrocytes and few fibroblasts arranged in rows, in collagen. No surrounding perichondrium.
- Mix of hyaline cartilage and dense regular connective tissue
What two tissues can fibrocartilage be called a mixture of?
Hyaline cartilage and dense regular
How do bones develop in the fetus in simple terms?
Hyaline cartilage model mineralises to form bone and then grows by endochondral ossification
What cartilage is at bone ends?
Hyaline Articular with no perichondrium. Nutrients come from synovial fluid.
Is bone inert?
No it is dynamic, constantly being broken down and remodelled
What is compact bone made of?
Concentrically arranged lamella. Osteons.
What is cancellous bones made up of?
Trabeculae. Lamellae woven together
