Cytology Week 11

Question 1

Describe compact(cortical bones) and its location

Answer 1

-Dense and located near the surface of the bones

Question 2

Explain where cancelous(trabecular ) bones are located

Answer 2

• Deeper within interconnecting cavities

Question 3

What is the bulbous end of Long bones called

Answer 3

Epiphyses

Question 4

What is the cylindrical part of Long bones called

Answer 4

Diaphysis

Question 5

Explain what Epipyses are composed of

Answer 5

— Cancellous bone covered by a thin layer of compact bone

Question 6

Explain the structure of Diaphysis

Answer 6

• Compact bone with thin layer of cancerous bone around the marrow cavity

Question 7

Name examples of were short bones are located

Answer 7

In the wrists and ankles

Question 8

Explain the structure of Short bones

Answer 8

• Contains a core of cancellous bone surrounded by compact bone

Question 9

Explain the structure of flat bones

Answer 9

Two layers of compact bones separated by a thicker layer of cancellous bone around

Question 10

At microscopic level: compact and cancellous bone show two what 2 types of Organization :

Answer 10

• Mature lamellar bone
  -Woven bone

Question 11

What is lamellar bone characterized by

Answer 11

• ## multiple layers of calcified matrix

Question 12

What type of collagen fibers does lamellar bone contain

Answer 12

• Type 1 collagen fibers

Question 13

What are Osteons
-What do central canals contain

Answer 13

-They are Cylindrical units with lamella surrounding a central canal
- Blood vessels,nerves

Question 14

What is the outer boundary of the osteon and what does it contain

Answer 14

• Cement line
  -Non collagen proteins, minerals and collagen

Question 15

Name the 2 bone regions

Answer 15

• Interstitial lamellae
  -Circumferential lamellae

Question 16

-What is Woven bone -What does it contain

Question 17

What are the characteristics/propeties of Woven bone

Answer 17

• Lower mineral content
• higher porportion of osteocytes than LAMELLAR bone

Question 18

What is the first bone to appear during embryonic development and fracture repair

Answer 18

-Woven bone

Question 19

Where are the areas thst Woven bone is retained

Answer 19

• Near the sutures of the calvaria
  -Insertions of some tendons

Question 20

Name the 2 main stages that occur in the bone development process

Answer 20

-Intramembranous Ossification
-Endochondral Ossification

Question 21

Explain bone formation process very breifly

Answer 21

• It initally produces woven bone but this is then later replaced by stronger lamellar bone.

Question 22

Explain briefly want happens in intramembranous ossification

Answer 22

Osteoblasts differentiate directly from mesenchyme and secrete osteoid.

Question 23

Explain briefly what happens in Endochondral Ossification

Answer 23

A hyaline cartilage matrix is eroded and invaded by osteoblasts, which begin producing osteoid.

Question 24

What type of bones does intramembraneous ossification form
+examples

Answer 24

• Flat bones such as :
  -Skull
  -Scapula
  -Clavicle

Question 25

Explain the key features in intramembranous ossification:include -Osteprogenitor cells -

Answer 25

- Osteoprogenitor cells proliferate(increase in number) and form osteoblasts -Osteoblasts secrete osteoid which calcifies into woven bone. - woven bone is later replaced by compact and cancellous bone.

Question 26

In intramembranous ossification what does Non-ossified mesenchymal regions become

Answer 26

-Periosteum and endosteum

Question 27

What bones does Endochondral Ossification produce

Answer 27

-Most bones icluding long bones

Question 28

Name the 4 main stages in Endochondral Ossification

Answer 28

- Bone collar formation -Cartilage Calcification -Primary Ossification center -Secondary Ossification center

Question 29

Explain the first and second step of enchondral ossification(Bone collar formation + Cartilage calcification)

Answer 29

- Osteoblasts form perichondrium and create the collar -Chondrocytes hypertrophy, secrete matrix proteins and initiate calcification

Question 30

Name the 2 cartilage regions that continue to remain in Endochondral Ossification

Answer 30

-Articular Cartilage -Epiphyseal Growth plate

Question 31

What happens in the 2nd+3rd step of Endochondral ossification(primary and secondary ossification)

Answer 31

- Osteoblasts invade the calcified cartilage, forming woven bone. - Develop later at epiphyses, creating cancellous bone.

Question 32

What does bone remodelling involve and function

Answer 32

-continuous bone resorption by osteoclasts and formation by osteoblasts. -Maintains bone shape

Question 33

Why does bone have an excellent repair capacity

Answer 33

-Due to osteoprogenitor cells

Question 34

Name the 3 phase bone repair

Answer 34

Phases of repair: -Formation of fibrocartilage. -Replacement of fibrocartilage with a temporary woven bone callus. -Remodeling into mature bone.

Question 35

Where does the skeleton sotre 99% of the bodys calcium

Answer 35

- In the hydroxyapatite crystals

Question 36

What is the function of the Parathyroid hormome in hormonal regulation of calcium

Answer 36

- Raises blood calcim levels -Stimulates osteoclasts activity by acting on osteoblast

Question 37

What is the funtion of the hormone Calcitonin in the regulation of calcium

Answer 37

- Lowers blood calcium levels -Inhibits osteoclasts activity

Question 38

Name the 2 hormones resposnible for the regulation of calcium

Answer 38

-Parathyroid hormone -Calcitonin

Question 39

What do joint types determine

Answer 39

The degree of movement between bones

Question 40

Name the 4 different types of joints

Answer 40

-Synarthroses -Synostoses -Syndesmoses -Symphyses

Question 41

What are intervetberal disc composed of

Answer 41

- Fibrocartilage

Question 42

What is the function of intevertebral discs

Answer 42

- Provide support and cushioning

Question 43

What are joints connected and stabilized by

Answer 43

Connective tisues

Question 44

What type of movement does synarthroses have

Answer 44

-Little or no movement

Question 45

What are the synarthroses joints subdivided into

Answer 45

-Synostoses -Syndesmoses -Symphyses

Question 46

Explain the strutcure and movement of synostoses joints

Answer 46

- Bones are fused allowing no movement

Question 47

What are syndesmoses joints joined by

Answer 47

Dense connective tissue

Question 48

What are symphyses joints joined by

Answer 48

- Fibrocartilage pad and thin articular cartilage