Unit 3 Microscopic Bone Anatomy And The Role Of Salts And The Organic matrix

Question 1

What is spongy bone composed of?

Answer 1

1. Small needlelike pieces of bone called trabeculae
2. “Open” spaces filled with marrow, blood vessels and nerves

Question 2

What are the components of compact bone?

Answer 2

1. Osteocytes - mature bone cells found in the bone matrix (lacunae)
2. Canaliculi run outward from the central canals to lacunae
3. Perforating canals (Volkmann’s canals)

Question 3

A compact bone complex containing osteocytes, canaliculi, and perforating canals is called what?

Answer 3

Osteon (Haversian) system

Question 4

Where are osteocytes found in bone?

Answer 4

In the bone matrix arranged in concentric circles called lamellae around central canals (Haversian canals)

Question 5

Where are central canals found in bone?

Answer 5

They run lengthwise through the bony matrix.

Question 6

What do the central canals in bone contain?

Answer 6

They carry blood vessels and nerves to all areas of the bone

Question 7

What is the function of the canaliculi?

Answer 7

1. Connect all bone cells to nutrient supply and waste removal
2. Bone cells are well nourished which allows bone to heal quickly

Question 8

Where are perforating (Volkmann’s) canals found in the bone?

Answer 8

They run in the compact bone at right angles to the shaft and central canals

Question 9

In embryos, what is the skeleton primarily made up of?

Answer 9

Hyaline cartilage

Question 10

In young children, what is the skeleton primarily made of?

Answer 10

Most of the cartilage has been replaced by bone

Question 11

Where does cartilage remain in adults?

Answer 11

Bridge of the nose, joints and parts of the ribs

Question 12

What are the strongest two types of tissues in the body?

Answer 12

Bone and cartilage

Question 13

All bones except flat bones develop by using what as their “model”?

Answer 13

Hyaline cartilage

Question 14

What do flat bones use as their “model”?

Answer 14

Fibrous membranes

Question 15

What is the process of bone formation called?

Answer 15

Ossification

Question 16

What are the two main steps in bone ossification?

Answer 16

1. Hyaline cartilage model is covered with bone matrix by bone-building cells called osteoblasts
2. The enclosed hyaline cartilage model is replaced by bone and the center is digested away forming the medullary cavity

Question 17

By birth, what two parts of the hyaline cartilage have not been converted to bone?

Answer 17

1. Articular cartilage
2. Epiphiseal plates

Question 18

In order for bones to grow, cartilage is formed continuously in what two places?

Answer 18

1. On the External face (joint side) of the articular cartilage
2. On the epiphileal plate surface

Question 19

What is the process where bones grow wider called?

Answer 19

Appositional growth

Question 20

What are the steps in appositional bone growth?

Answer 20

1. Osteoblasts in the periosteum add bone matrix to the diaphysis
2. Cells called osteoclasts in the endosteum remove bone from the inner face of the diaphysis wall enlarging the medullary cavity

Question 21

What two factors cause bones to be remodeled?

Answer 21

1. Calcium ion level in the blood
2. The pull of gravity and muscles on the skeleton

Question 22

What happens when blood calcium levels drop below a set point?

Answer 22

1. The parathyroid glands are stimulated to release parathyroid hormone (PTH) into the blood
2. This activates osteoclasts to break down bone matrix and telease calcium ions into the blood

Question 23

What are osteoclasts?

Answer 23

Giant bone-destroying cells in bones

Question 24

Wjat happens when blood calcium levels are too high?

Answer 24

Calcium is deposited in bone matrix as hard calcium salts by osteoblasts

Question 25

Why is bone remodeling essential?

Answer 25

It keeps bone proportions and strength

Question 26

What do osteoblasts become after laying down new matrix and becoming trapped?

Answer 26

Osteocytes

Question 27

Why do the bones of bedridden or inactive npeople lose mass?

Answer 27

Because they are no longer subjected to stress