The Skeletal System I

Question 1

What are nearly all bone and cartilage derived from?

Answer 1

From mesoderm

Question 2

Mesenchyme is

Answer 2

Loosely aggregated network of unspecialized cells and when influenced by inductor substance it differentiates into specialized cells

Question 3

The skeleton is composed of?

Answer 3

mineralized connective tissue and of ligaments and tendons

Question 4

What are the three categories of mesenchyme?

Answer 4

1. Fibroblast - Collagen
2. Myoblast - Muscles
3. Scleroblasts

Question 5

What is the break down of Scleroblast

Answer 5

1. Osteoblast (bone)
2. Chondroblasts (Cartliage)
3. Odontoblast (Dentine)
4. Enamel

Question 6

Define bone

Answer 6

Bone consists of matrix fibres impregnated with Hydroxyapetite crystals

Question 7

What are Osteoblast?

Answer 7

Osteoblast lay down material (Calcium Phosphate) around them

Question 8

What are Osteocytes

Answer 8

Become trapped in a fluid-filled chamber (Lacuna)

Question 9

What is the gross structure of long bone?

Answer 9

Spongy Bone
Marrow Cavity
Compact Bone
(Know where these structures are on the long bone)

Question 10

What are the two kinds of bone?

Answer 10

Compact

Spongy

Question 11

What is compact bone?

Answer 11

Series of lamellae that radiate out from a central Haversian Canal
- Look at the diagram provided and learn the three labels)

Question 12

What is spongy bone?

Answer 12

bone is lighter and less dense than compact bone.

• Trabeculae
• Irregular arrangement of lacunae

Question 13

What are the two different ways in which ossification occurs?

Answer 13

1. Membrane (intramembranous) bone

2. Endochondral (replacement) bone

Question 14

Membrane (intramembranous) bone

Answer 14

Bone arises directly from mesenchyme without cartilaginous precursor

• initially, mesenchyme compacted into sheets or membranes
• some mesenchyme cells
  differentiated into osteoblasts (secrete hydroxyapetite)
• Growth proceeds by application of successive layers

Question 15

Memebrane bone formationn

Answer 15

• Refer to diagrams on handout

Question 16

What are the three kinds of membrane bone

Answer 16

1. Dermal
2. Sesam
3. Periosteal

Question 17

What is dermal bone (membrane bone)

Answer 17

It arises from the dermis

- some bones of the skull, pectoral girdle and integument

Question 18

What is Sesam Bone (membrane bone)

Answer 18

Forms directly within tendons (e.g patella, kneecap)

Question 19

What is Periosteal Bone (membrane bone)

Answer 19

Outer layer of long bones

Question 20

What is Endochondral (replacement) bone

Answer 20

• more complex as it involves replacement of embryonic cartilage with adult bone

Question 21

What are the steps of Endochondral (replacement) bone

Answer 21

Step 1: loose collections of
mesenchymal cells condense to form hyaline cartilage model surrounded by perichondrium

Step 2: cells on inner surface of diaphyseal perichondrium
become osteoblasts - deposit bone collar (periosteum)

Step 3: chondrocytes in centre of model
hypertrophy (enlarge), release calcified cartilage, then die

Step 4: vascular system invades calcified cartilage and calcified cartilage resorbed

Step 5: osteoblasts delivered to the core of the bone and primary centres of established ossification
- Activation centre of cartilage growth, calcification, cartilage removal and bone deposition

Step 5: collar thickens, osteoclasts create central cavity

Question 22

What are the 5 zones of Endochondral (replacement) bone

Answer 22

• Resting Zone
• Proliferative Zone
• Maturation zone
• Hypertrophic zone
• Ossification zone
• Understand where this zones are in a diagram *

Question 23

Where do Dentine and Acellular Bone form

Answer 23

Forms only in the outermost regions of the dermis (just below the epidermis)

Question 24

What is the difference between Acellular bone and dentine?

Answer 24

• Dentine do leave behind canaliculi where as acellular do not

Question 25

Odontoblasts

Answer 25

``` - osteoblasts retreat after depositing hydroxyapetite - not trapped in lacunae - do leave behind canaliculi - dentinal tubules ``` Ganoid scales, Placoid Scales and teeth (Dentine) Teleost scales (ctenoid and cycloid) and cementum of teeth (Acellular)

Question 26

Cartilage

Answer 26

Can either be similar to bine or different from bone

Question 27

If the cartilage is similar to bone

Answer 27

Forms within a matrix of collagen fibers Cells chondrocytes lie within lacunae

Question 28

If cartilage is different from bone

Answer 28

chondromucin (a mucopolysaccharide) instead of hydroxyapetite no canaliculi no blood vessels within tissue (receive nutrients through diffusion)

Question 29

Overview of Cartilage

Answer 29

* refer to the diagram

Question 30

What are the three main kinds of cartilage?

Answer 30

1. Hyalin 2. Fibrocartilage 3. Elastic

Question 31

Define Hyalin (Cartilage)

Answer 31

- Precursor to endochondral bone - Some remains as cartilage throughout life (tips of long bones, ribs, trachea, parts of skull)

Question 32

Define Fibrocartilage

Answer 32

- Characterized by greater amount of collagen (in matrices between lacunae vertebral disks

Question 33

Define Elastic (Cartilage)

Answer 33

elastic fibers (in addition to collagen) make it very flexible Pinna of ear, Epiglottis

Question 34

What are tendons, ligaments and Fascia

Answer 34

- all consist of tightly packed, parallel bundles of collagen fibers

Question 35

What to tendons attach

Answer 35

Muscle to bone

Question 36

What do tendons function as?

Answer 36

More then simple transmit forces, they also act as springs An example of this is the Achilles tendon, stretched when the ankle joint dorsiflexes and stores energy, as the foot lifts off the ground, energy is released

Question 37

What do ligaments attach ?

Answer 37

Bone to bone

Question 38

What does fascia attach?

Answer 38

Muscle to muscle and can also surrounds muscle bones, nerves and blood vessels * refer to the diagram on the

Question 39

Why do damage to tendons, ligaments and fascia take a long time to heal?

Answer 39

inflammation - repair - remodelling There is minimal vascularization, typically cross-linking between collagen bundles and reduces the ability to stretch