Skeletal System

Question 0

Before 8 weeks, the skeleton of embryo is made of?

Answer 0

fibrous membranes and hyaline cartilage

Question 1

What does the Skeletal System do?

Answer 1

1) support
2) protects vital organs
3) attaches muscle and allows movement
4) red bone marrow produces red blood cells and white blood cells
5) stores Ca2+

Question 2

When does formation of bones begin and when does it end?

Answer 2

8th week of embryo –> 20 years of age

Question 3

What are the types of bone ossification?

Answer 3

1) intramembranous ossification

2) endochondral ossification

Question 4

What is a intramembranous ossification?

Answer 4

• a type of bone ossification that uses CT membrane to form bones

Question 5

Explain the process of intramembranous ossification.

Answer 5

• osteoblasts creates the spongy bone along the CT fibres

- then the periosteum forms and the osteoblasts beneath it lay down the compact bone

Question 6

Give some examples of bones formed through intramembranous ossification.

Answer 6

• flat bones such as skull bones, mandible, clavicle

Question 7

What are fontanels?

Answer 7

• they are formed via intramembranous ossification but they actually unossified membranes in the skull that remains at birth

Question 8

What is endochondral ossification?

Answer 8

• a type of bone ossification that uses hyaline cartilage as a model for bone construction

Question 9

Explain the process of endochondral ossification.

Answer 9

• hyaline cartilage is ossified to make spongy bone

- periosteum is formed and the osteoblasts underneath it lays down the compact bone

Question 10

Most bones are formed via intramembranous ossification or endochondral ossification?

Answer 10

endochondral ossification

Question 11

articular cartilage and epiphyseal plates are an example of what?

Answer 11

• cartilage that has not been ossified in endochondral ossification

Question 12

growth in length is a type of _________

Answer 12

endochondral growth at the epiphyseal plate

Question 13

How does bone grow in length?

Answer 13

• cartilage grows and the matrix near the diaphysis becomes bone
• the growth in length only stops when the epiphyseal plate ossifies to become an epiphyseal line (closure)

Question 14

bone growth in width or diameter is a type of what?

Answer 14

appositional growth

Question 15

how does bone grow in diameter?

Answer 15

• osteoblasts beneath the periosteum secretes bone matrix on the external bone surface
• the osteoblasts then resorb bone on the endosteal surface therefore size of cavity keeps up with the growing bone

Question 16

What are some factors that affect bone growth?

Answer 16

• mechanical stress
• nutrition
• hormone

Question 17

Mechanical stress is usually due to?

Answer 17

muscle action

Question 18

how does mechanical stress affect bone growth?

Answer 18

• when there’s an injury that restricts movement, the osteoblast activity goes down and theres no change in osteoclast activity = decreased bone mass
• however, weights and electric currents may speed healing by increasing the osteoblast activity

Question 19

On behalf of nutrition, how does Ca2+ and PO4- affect bone growth

Answer 19

• they are required for bone matrix production

Question 20

On behalf of nutrition, what does Vitamin C do to bone growth?

Answer 20

• required for collagen production

Question 21

On behalf of nutrition, how does Vitamin D affect bone growth?

Answer 21

• it increases Ca2+ absorption from the intestine

- low levels of Vitamin D can cause soft bones called Rickets

Question 22

What types of hormones stimulate bone growth?

Answer 22

• Growth Hormone
• Estrogen
• Testosterone
• Thyroid Hormone

Question 23

How does estrogen and testosterone affect bone growth?

Answer 23

• increase osteoblast activity

- estrogen ossifies epiphyseal plate to epiphyseal line

Question 24

How does calcitonin affect bone growth?

Answer 24

• it inhibits osteoclast activity

- responsible for releasing Ca2+ to the blood which stimulates bone growth

Question 25

How does the parathyroid hormone affect bone growth?

Answer 25

• decreases osteoblast activity and increases osteoclast activity which increases Ca2+ levels (important for bone matrix reproduction)

Question 26

What is osteoporosis?

Answer 26

a decrease in bone mass

Question 27

What are some risk factors of osteoporosis?

Answer 27

1) increasing age which decreases sex hormones
2) inadequate diet (lack of vitamin D, low Ca2+)
3) Smoking decreases estrogen
4) Drugs like cortisone and alcohol decrease osteoblast activity
5) too little or too much exercise causes stress and increase of cortisol
6) Too much parathyroid hormone
7) menopause decreases estrogen

Question 28

Explain the process of bone repair.

Answer 28

1) begins with formation of blood clot
2) replaced by a callus consisting of fibrous network and fibrocartilage islets
3) callus ossifies via intramembranous & endochondral ossifications
4) takes 4-6 weeks to heal but requires a cast because movement can cause re-fracture of new matrix.

Question 29

What is Rickets? And what causes it?

Answer 29

Soft bones dues to the lack of vitamin D