Chapter 6: bones

Question 1

Describe the 6 main functions of the skeletal system:

Answer 1

• Provides support
• Protects the internal organs (brain, (heart, etc.)
• Assists body movements (conjunction with muscles)
• Mineral homeostasis - stores and releases calcium and phosphorus
• Participates in blood cell production (hemopoiesis)
• Stores triglycerides in the adipose cells of yellow bone marrow

Question 2

Describe the structure and functions of each part of the long bone

Answer 2

• Diaphysis (bone shaft)
• 2 epiphyses (both ends of the bone at the joint)
• 2 metaphyses (region between diaphysis and epiphysis) - where growth happens
• Articular cartilage covering both epiphyses
• Periosteum - connective tissue surrounding diaphysis)
• Medullary cavity - hollow space
• Endosteum - thin membrane lining medullary cavity

Question 3

Compare the properties of compact and spongy bone tissue

Answer 3

• Spongy bone contains holes which content the red or yellow bone marrow
• Compact bone its yellow in colour and stronger overall

Question 4

Explain why bone is classified as a connective tissue

Answer 4

• Bone contains an abundant extracellular matrix that surrounds widely separated cells
• Only hard connective material
• Bones hardness depends on crystalized inorganic mineral salts
• Bone flexibility depends on collagen fibers

Question 5

Cells that make up bone tissue

Answer 5

• osteoprogenitor cells
• osteoblasts
• osteocytes
• osteoclasts

Question 6

Osteoprogenitor cells

Answer 6

bone stem cells, able to differentiate into different types of cells

Question 7

osteoblasts

Answer 7

bone building cells that secrete matrix; bone deposition (calcification)

Question 8

Osteocytes

Answer 8

mature bone cells

Question 9

Osteoclasts

Answer 9

remodels bone and causes them to release calcium: bone resorption.

come from macrophages

Question 10

Compare the structural and functional differences between compact and spongy bone

Answer 10

• compact bone is good at providing support and is the strongest of the 2
• spongy bone is light weight, provides tissue support and contains bone marrow

Question 11

Describe nerve supply of the bone

Answer 11

• periosteal arteries enter the diaphysis through perforating canals and are accompanied by periosteal veins
• A bone may have one or several nutrient arteries
• The metaphyses and epiphyses also have their own arteries and veins

Question 12

4 situations bone growth/formation occurs

Answer 12

• During embryonic and fetal development
• When bone grows before adulthood
• When bones remodel (thicker and thinner)
• When fractures heal

Question 13

Where does intramembranous ossification occur

Answer 13

• occurs in flat bones
• occurs when a connective tissue membrane is replaced by bone

Question 14

Intramembranous ossification steps

Answer 14

1. Development of ossification center: osteoblasts secrete extracellular matrix
2. Calcification: calcium and other minerals are deposited
3. Formation of spongy bone trabeculae: ECM develops into spongy bone
4. Development of the periosteum: mesenchyme at periphery line of bone develops into periosteum

Question 15

Steps in endochondral ossification

Answer 15

1. Development of cartilage model: mesenchymal cells develop cartilage
2. Growth of cartilage: growth occurs by cell division of chondrocytes
3. Development if primary ossification center: in the diaphysis, bone tissue begins to replace cartilage
4. Development of the medullary cavity: osteoclasts break down bone to create medullary cavity
5. Development of secondary ossification centers: these occur in the epiphyses of the bone. (bone starts to form at ends)
6. Formation of articular cartilage and epiphyseal plate: hyaline cartilage at end

Question 16

Explain how bone grows in length and thickness

Answer 16

1. Ridges in the periosteum create a groove for the periosteal blood vessel
2. Periosteal ridges fuse, forming endosteum lined tunnel
3. Osteoblasts in endosteum build new concentric bone lamellae inward toward center of tunnel, forming new osteon
4. Bone grows outward as osteoblasts in the periosteum build new circumferential bone lamellae. Osteon formation repeats.

Question 17

Factors affecting bone growth and remodeling

Answer 17

• Parathyroid hormone increases the number of activity of osteoclasts and stimulates formation of calcitriol
• Calcitonin from the parafollicular cells in the thyroid gland inhibits activity of osteoclasts and speeds blood Ca taken up by bone
• Sex hormones promote osteoblast activity, synthesis of bone extracellular matrix; estrogen slows bone resorption by promoting apoptosis of osteoclasts. Therefore estrogen increases bone deposition.

Question 18

Common types fractures

Answer 18

• open: pierces skin
• comminuted: splintered/crushed
• greenstick: soft bones don’t break all the way through
• impacted: one end drives into interior of other
• Pott: ankle
• Colles: wrist
• Vertebral

Question 19

Regulation of blood calcium

Answer 19

• when blood calcium levels drop the parathyroid gland secretes the parathyroid hormone which increases the number and activity of osteoclasts to step up the pace in bone resorption
• PTH acts on kidneys to retain calcium
  -PTH stimulates calcitriol which increases the absorption of calcium and phosphorus in the GI tract

Question 20

How does exercise affect bone tissue

Answer 20

weight bearing activities stimulate osteoblasts and consequently help build thicker and stronger bones

Question 21

Describe the effects of aging on bone tissue

Answer 21

bone resorption by osteoclasts outpaces osteoblasts which leads to decrease in bone mass