Connective Tissue - Bone & Cartilage

Question 1

What are the main functions of cartilage?

Answer 1

1. provide resilient and pliable support

2. direct formation and growth of bone

Question 2

What do chondrocytes do?

Answer 2

make cartilage matrix and tissue

• primitive mesenchymal cells -> chondrocytes
• perichondrium -> chondrocytes
• secrete ECM components

Question 3

What are lacuna?

Answer 3

isolated compartments wehre cartilage resides

• interstitial growth is possible here
• continue to secrete cartilage matrix

Question 4

What are the 3 type of cartilage?

Answer 4

1. Hyaline Cartilage
2. Elastic Cartilage
3. fibrocartilage

Question 5

Describe hyaline cartilage

Answer 5

Thin fibrils
Ground substance = hyaluronic acid -> hydration & flexibility
- allows metabolites to diffuse through tissue
- resilient to compression
- allows growth of chondrocytes within matrix
- can calcify and initiate bone formation

Question 6

What distinguishes elastic cartilage from hyaline and fibrocartilage?

Answer 6

- abundant elastic fibers and 
interconnecting sheets (lamellae)
- external ear
- epiglottis_ larnyx
Should not calcify

Question 7

Describe fibrocartilage

Answer 7

large bundles of regularly arranged collagen

• continuation of dense connective tissue (very similar to one another )
• resists compression and shear forces
• found where tendons attach to bones
• intervertebral discs

Question 8

What are the two types of bone?

Answer 8

1. flat bone (skull, mandible)

2. long bone (femur, tibia, humerus)

Question 9

What are the parts of a long bone?

Answer 9

diaphysis - long shaft

epiphysis - expanded ends

Question 10

What are the two regions of bone?

Answer 10

compact bone
spongy bone (aka cancellous/ trabecular)

Question 11

What are trabeculae?

Answer 11

• thin anastomosing spicules in spongy bone

- important in signaling

Question 12

What is the function of compact bone?

Answer 12

provide support

Question 13

What is the function of spongy bone?

Answer 13

trabeculae provide surface area for metabolism

Question 14

Where is bone marrow and what does it consist of?

Answer 14

Bone marrow is the inner spongy tissue between trabeculae
consists of:
- hematopoietic tissue (red bone marrow)
- adipose cells (white bone marrow)

Question 15

What is the outer covering of bone called? and what does it contain?

Answer 15

periosteum

• dense connective tissue
• fibroblasts
• bone precursors
• bone cells

Question 16

What is the endosteum?

Answer 16

Inner contact between trabeculae and inner soft tissue

- location of most calcium mobilization

Question 17

What are the different types of bone cells?

Answer 17

osetoprogenitor
osteoblasts
Osteocytes
osteoclasts

Question 18

What are osteoprogenitor cells?

Answer 18

stem cells, periosteum and endosteum

Question 19

What are osteoblasts?

Answer 19

• secrete osteoid
• release matrix vesicles -> initiate bone calcification
• capable of division

Question 20

What are osteocytes?

Answer 20

from osteoblasts

• do not divide
• form in lacuna
• interconnected living lattice of cells
• signal one another through gap junctions

Question 21

What are osteoclasts?

Answer 21

NOT FROM OSTEOPROGENITOR

• from monocytes of blood
• related to macrophage -> phagocytose
• degrade bone or cartilage
• allow inward growth of blood vessels
• resorb/ remodel bone
• mobilize Ca2+

Question 22

What substance is specific to the gone matrix? What is it made of?

Answer 22

hydroxyapatite

• Ca2+
• PO4

Question 23

What are haversian canals?

Answer 23

channels traversing long axis of long bones - surrounded by lamellae
canal + lamellae = osteon

Question 24

What are Volkmann’s canals?

Answer 24

link haversian canals

Question 25

How do flat bones form?

Answer 25

intramembranous ossification

Question 26

How do long bones form?

Answer 26

Encochondral ossification

Question 27

What is appositional growth?

Answer 27

Growth in pericondrium at cartilage surface -> fibroblasts proliferate into more chondrocytes -> secrete hyaline matrix

Question 28

What is interstitial growth?

Answer 28

Chondrocytes within matrix continue to proliferate within their lacunae
- groups of chondrocytes within lacunae
=> isogenous groups

Question 29

What are some disorders of bone remodeling?

Answer 29

osteoperosis -> decrease in bone mass
(defect in resoption/formation coupling)

Osteopetrosis -> defective resorption & increased bone mass

Osteomalacia rickets -> abnormal increase in uncalcified osteoid -> interferes with mineralization

Question 30

How do osteoblasts initiate mineralization of osteiod?

Answer 30

secrete matrix vesicles

• have high levels of Ca2+ and PO4
• activate and form precipitates -> grow and rupture vesicle-> nucleation sites that trigger mineralization cascade

Question 31

What pathways control bone remodeling/ regulation?

Answer 31

Short range signals (BMPs)
Long range signals
Mechanical stress
Neuronal stimulation

Question 32

What are bone morphogenetic proteins (BMPs)?

Answer 32

secreted by cells
- bind surface receptors -> trigger intracellular phosphorylation -> alter gene expression=> promote specific differentiation patterns

Question 33

What is the effect of parathyroid hormone on Ca2+ levels in the blood?

Answer 33

increases blood calcium

Question 34

What is the effect of Calcitonin on Ca2+ levels in the blood

Answer 34

Decreases blood calcium

stiumlates resorption