Bone Tissue

Question 1

General functions of skeletal system

Answer 1

1. Support
   - bone (hard+rigid)
   - cartilage (flexible+strong)
   - ligaments
2. Protection
3. Movement
   - produced by muscles on bone
4. Storage
   - calcium and phosphorus
   - fat
5. Blood cell production - RED marrow: blood cell production
   - YELLOW marrow: as we age red-> yellow. Stores adipose tissue.

Question 2

What is cartilage?

Answer 2

Connective tissue
- smooth, resilient (bounces back to original shape), non-vasular
- cells and matrix 70-85% water, ground substance (proteoglycans), protein (collagen + elastic)

Question 3

3 types of cartilage

Answer 3

• hyaline
• elastic
• fibrocartilage

Question 4

Hyaline cartilage

Answer 4

• most common
• found on surface of moveable joints
• forms in embryological development (calcifies into bones)
• E.g. bridge of nose, covering trachea

Question 5

Elastic cartilage

Answer 5

• used in places that need flexibility
• protein fibres more elastic
• E.g. oracle of ear

Question 6

Fibrocatilage

Answer 6

• strongest cartilage
• found where more support is needed (intervertebral disks, meniscus)

Question 7

cartilage histology

Answer 7

• 1 main cell type: CHONDROCYTE
• located in a LACUNA
• immature chondrocyte = CHONDROBLAST (located along edge of cartilage)

Question 8

perichondrium

Answer 8

Double layer of connective tissue that covers most cartilage

Superficial layer: fibroblasts
- blood supply and nervous tissue

Deep layer: osteochondro progenitor cells

Question 9

What kind of cartilage doesn’t have a perichondrium and why?

Answer 9

Articular cartilage
- otherwise blood and nervous tissue would get easily damaged
- but this makes it hard to repair

Question 10

2 ways to grow cartilage

Answer 10

APPOSITIONAL GROWTH
- new growth just below perichrondrium via chondrocytes
- occurs in adulthood

INTERSTITIAL GROWTH
- mature chondrocytes divide
- occurs in youth

Question 11

how do chondroblast cells mature?

Answer 11

secrete matrix
surround themselves in that matrix
eventually turn into chondrocytes

Question 12

difference between bone and cartilage

Answer 12

bone: constantly broken down
cartilage: can build more or repair, isn’t broken down

Question 13

bone histology

Answer 13

65% inorganic
- crystallized mineral salts
- HYDROXYAPATITE: calcium phosphate crystals (calcifies bones)
35% organic
- collagen/proteoglycans, water
- minerals: compressive strength

Question 14

role of hydroxyapatite in bone

Answer 14

calcifies/solidifies bone

Question 15

describe bones without minerals and without collagen

Answer 15

without minerals: only flexible strength
without collagen: only compressive strength

Question 16

osteoblasts

Answer 16

BUILDERS! Make framework for matrix (ossification)

• produce collagen and proteglycans (in vesicles)
• form MATRIX VESICLES (Ca+ and phosphate) via pinching
• release these vesicles - bone matrix is formed
• physically connect to each other via CANALICUILI

Question 17

ossification

Answer 17

bone formation

Question 18

oteochondral progenitor cells

Answer 18

stem cells that can become osteoblasts or chondroblasts

Question 19

osteocyte cells

Answer 19

osteocyte = osteoblast surrounded by bone matrix

Maintain the matrix
- also located in a lacuna
- considered inactive but maintain ability to produce necessary components to maintain bone matrix

Question 20

osteoclast cells

Answer 20

Resorption of bone
- secrete acid and enzymes, dissolve calcium, phosphorus and collagen

• large multi-nuclear cells (formed by fusion of monocytes (white blood cell type))
• found on surface of bones

once activated
- attach to bone via PODOSOMES, creates sealed compartment
- RUFFLED BORDER formed, increases surface areas
- releases acids and enzymes
- bone fragments released into extracellular space

Question 21

Which substance is present in the largest quantity in a mature bone?

Answer 21

hydroxyapatite

Question 22

chondroblast

Answer 22

produce cartilage matrix

Question 23

stem cells that can become osteoblasts or chondroblasts

Answer 23

oteochondral progenitor cells

Question 24

term for breaking bone down (osteoclast’s job)

Answer 24

resorption