Cartiliage & Bone

Question 1

In the epiphyseal plate, the zone closest to the epiphysis?

Answer 1

Resting zone

Question 2

Layer closest to diaphysis?

Answer 2

Zone of ossification

Question 3

Perichondrium characteristics?

Answer 3

Outer fibrous layer (fibroblasts, type I collagen, blood vessels)
** cartilage is avascular **
Inner cellular layer (chondrogenic layer) – site of appositional growth

Question 4

Hyaline cartilage characteristics?

Answer 4

Precursor to bone
Type II collagen
Most common type of cartilage
Chondrocytes arranged in isogenous groups
Perichondrium everywhere, except articular surfaces of long bones and epiphyseal

Question 5

Elastic cartilage characteristics?

Answer 5

Type II collagen + elastic fibers

Locations: pinna of ear, auditory tubes, epiglottis

Question 6

Fibrocartilage characteristics?

Answer 6

Fibrocartilage
Type I collagen, and some type II
Chondroytes arranged in parallel rows
Perichondrium is ABSENT
Locations: pubic symphysis, intervertebral discs (annulus fibrosis*),

Question 7

Entheses what is it?

Answer 7

ligaments/tendons/muscle into bone

Question 8

Annulus fibrosis, What is the made of?

Answer 8

Fibrocartilage - Type I collagen

Question 9

Nucleus pulposus, what is made of?

Answer 9

Type II collagen (replaced by type I with age)

Question 10

Type 3 collagen fibers?

Answer 10

Reticular fibers

Question 11

Periosteum chracteristics?

Answer 11

Outer fibrous layer

Inner cellular layer (osteogenic layer containing osteoprogenitor cells)

Question 12

Endosteum characteristics?

Answer 12

Inner layer of osteoblasts in bone marrow

Question 13

What do osteoblasts do and what receptor do they have?

Answer 13

Receptors for PTH -> signals and activates osteoclasts -> bone resorption

Question 14

What do osteoclasts do and what receptor do they have?

Answer 14

Derived from monocytes
Multinucleated
Form Howship’s lacunae
Receptors for Calcitonin – inhibit bone resportion

Question 15

Primary bone characteristics?

Answer 15

Immature; osteoid
Abundant osteocytes
LOW mineral content
Irregular collagen bundles

Question 16

Secondary bone characteristics?

Answer 16

Mature 
Osteocytes in lacunae with canaliculi
HIGH mineral content
Parallel arrangement of collagen
Has Haversian system/osteons

Question 17

Difference b/w interstitial lamellae and circumferential lammelae?

Answer 17

interstitial lamellae will not be a fully formed circle

Question 18

Intramembranous bone characteristics?

Answer 18

Flat bones of the skull

Development within layer of condensed mesenchyme

Question 19

Endochondral characteristics?

Answer 19

LONG bones; Bone widening (appositional growth)
Cartilage model replaced by bone
a. growth occurs at epiphyseal side of plate
b. resorption occurs at diaphyseal side of plate
c. five cellular zones of epiphyseal plate growth
1. zone of reserve cartilage
2. zone of proliferation
3. zone of maturation / hypertrophy
4. zone of calcification
5. zone of ossification

Question 20

Intramembranous growth steps?

Answer 20

Mesenchymal cells -> primary ossification centre -> osteoblasts start to build osteoids -> trapped in lacunae (osteocytes) -> ossification centre

Question 21

Endochondral growth steps?

Answer 21

Hyaline cartilage laid down as template -> proliferation & hypertrophy of chondrocytes at midpoint -> primary ossification centre -> invasion of blood vessels & mesenchye -> secondary ossification centre; Bone lengthening occurs at epiphyseal plate

Question 22

Interstitial growth of cartilage?

Answer 22

Lengthening; outward from established chondrocytes

Question 23

Appositional growth of cartilage?

Answer 23

Width; inward from chondrogenic layer of perichondrium