Bone And Cartilage Flashcards
What are the two types of bone development?
What type of bone do they produce?
Endochondral ossification (long bones) Intramembranous ossification (flat bones)
What are the sections of the bones called?
What is the point of growth called?
End- epiphysis
Middle- diaphysis
Intermediate between both- metaphysis
Growth point= epiphyseal growth plate
Describe the process of endochondral ossification (5 steps)
1) Hyaline cartilage replaced by periosteal bone on edges of bone
2) calcification of diaphysis occurs and the primary ossifictaion centre appears
3) calcified area becomes spongy (cancellous) bone, growth plates appear as do secondary ossification centres
4) calcification occurs in the epiphysis, growth plates move apart
5) growth plates replaced by spongy (cancellous bone), hyaline cartilage remains at articulating surfaces
What is the starting point of endochondral ossification?
Hyaline cartilage
What is the starting point for intramembranous ossification?
Mesenchymal stem cells
Describe the process of intramembranous ossification (5 steps)
1) stem cells form nidus
2) stem cells become osteoprogenitor cells
3) osteoprogenitor cells become osteoblasts and lay down osteoid
4) osteoid mineralises forming (rudimentary bone tissue) spicules
5) spicules fuse to form trabeculae which form woven bone which from mature compact bone
What do you call the initial group of mesenchymal stem cells in intramembranous ossification?
A nidus
What do osteoblasts do?
Lay down osteoid
What type of collagen is in osteoid?
Type 1
What are the two types of bone?
Compact (Cortical) and cancellous (spongy)
Describe features of cancellous bone
Found in the middle of bones Spaces filled with bone marrow Combines strength and lightness Has trabeculae Highly vascular
Describe the features of compact bone
External
Has haversian and volkmanns canal
Has lamellae
Has no trabeculae
What is the difference between mature and immature bone?
Mature bone has osteocytes arranged in concentric lamellae of osteons and the reabsorption canals run parallel with the osteons’ long axons.
Immature bone has osteocytes arranged randomly and has no haversian or volkmanns canals
What are the layers of compact bone? (List outside in)
Peristeal Outer circumferential lamellae Osteons Interstitial lamellae Inner circumferential lamellae Endosteum
(Remember the mnemonic: POO Is Incredible Entertaining)
What cells break down bone?
Osteoclasts
What do osteoclasts use to breakdown bone?
H+ and lysosomal enzymes
What cells relays bone? What do they lay down and how does it become bone?
Osteoblasts
Relay osteoid which becomes spicules which becomes trabeculae which becomes a new osteon (with concentric lamellae)
What are the four stages of bone repair?
1) haematoma formation
2) fibrocartilaginous callus formation
3) boney callus formation
4) bone remodelling
(Remember the mnemonic: He Found, Fat Cats Fighting, Beneath Chicago’s Foot, Bridge Recently)
What happens during haematoma formation? Which stage of bone repair is this?
Haematoma forms Cells die (lack of blood) Swelling due to inflammatory response Dead/damages tissue is removed by phagocytosis (phagocytic cells and osteoclasts) Macrophages remove clot
1st stage
What happens during fibrocartilaginous callus formation? What stage of bone repair is this?
Angiogenesis
Soft callus formation (rich in capillaries and fibroblasts)
Fibroblasts produce collagen
Some fibroblasts become chondrocytes and produce hyaline cartilage
Bulging of new matrix
Osteoblasts form immature cancellous bone
2nd stage
What happens during boney callus formation? What stage of bone repair is this?
Trabeculae from bony callus (hard) of cancellous bone
Both types of bone development occur
3rd stage
What happens during bone remodelling? What stage of bone repair is this?
Hard callus of cancellous bone becomes compact bone
Osteoclasts remove bulging
4th stage
Why is mechanical stress a good thing after a bone break?
It promotes bone reformation and strengthening
What is osteoporosis?
A condition in which bone mass decreases
Bone reabsorption>bone formation
What is type 1 osteoporosis?
Occurs in post menopausal women, due to high osteoclasts number after oestrogen is withdrawn.
What is type 2 osteoporosis?
Occurs in older people (senile +70)
Due to reduced osteoblasts function
List the risk factors for osteoporosis (5)
Genetics (some ethnicities at more risk)
Insufficient Ca2+ intake (diet)
Insufficient vitamin D (lack of sun/ diet)
Exercise (bone strengthening)
Cigarettes (has particular impact on women)
What are the 3 types of cartilage?
Hyaline, elastic and fibrocartilage
What type of collagen is in hyaline, elastic and fibrocartilage?
Hyaline and elastin = type 2
Fibrocartilage= type 1 (which is thicker)
Does cartilage have a blood supply?
No, it is avascular
What is cartilage made of?
Ground substance, cells and fibres
What is ground substance made of?
Proteoglycans which is many GAG (glycosaminoglycans) attached to a core protein which are in turn attached to hyaluronic acid
What cells are found in hyaline cartilage?
Chondrocytes only
As singles or isogenous groups (small clusters that separate as EXC matrix is laid)
Where is hyaline cartilage found?
Articulatin surfaces, foetal skeleton, trachea, bronchi etc
How can. Hyaline cartilage resists varying pressure loads?
It is highly hydrated
What is the structure of hyaline cartilage?
Outer layer of perichondrium (dense connective tissue)
Elongated fibroblast-like cells that will develop into chondroblasts (and eventually chondrocytes)
Interterritorial (middle- where chondrocytes lie)
Structure repeats
What do chondrocytes lie within in hyaline cartilage?
Lacuna
What is the dense connective tissue which covers hyaline cartilage?
Perichondrium
What cells do you find in elastic cartilage?
Chondrocytes only
What makes elastic cartilage different from hyaline cartilage?
There are many elastin fibres in elastin cartilage
What properties do the elastin fibres convey to the elastic cartilage?
Elasticity and resilience
Where can elastic cartilage be found?
Pinna of ear, epiglottis, eustachian tube etc
What is the dense connective tissue that surrounds elastic cartilage called?
Perichondrium
What are the main functions of fibrocartilage?
Shock absorption and resisting shearing forces
What cells do you find in fibrocartilage?
Chondrocytes and fibroblasts (cells in rows or isogneous groups)
What is fibrocartilage?
A combination of dense regular connective tissue and hyaline cartilage
Where is fibrocartilage found?
Intervertebrae discs, pubic symphysis, menisci of knee joint etc
