A&P 1 Chapter 6 (Lecture) [The Bones, Part 1]

Question 1

Features of a Long Bone

Answer 1

• Diaphysis
• Epiphysis (Epiphyses)

Question 2

Diaphysis

Answer 2

• The shaft of a long bone
• Contains medullary or marrow cavity
  
  • Infants have considerable red (hematopoietic) bone marrow
  • Red marrow is gradually replaced by yellow (fat) bone marrow throughout life.

Question 3

Epiphysis (Epiphyses)

Answer 3

• Ends of a long bone
• Epiphysea plate- growth plate made of cartilage
• ***Nutrient foramen- site of blood vessel entry into bone
• Articular cartilage- hyaline cartilage covering epiphysis

Question 4

Why do we need both proteins and calcium phosphate salts in bones. (2 Major Chemical Components of Bone)

Answer 4

Proteins (collagen fibers) give bone the flexibilty they need to bend a little bit with out breaking. Calcium phosphate salts give bone the hardness to provide support. If there were no proteins in bones the bones would be very strong but brittle. If there were no calcium phosphate salts in bones the bones would be too flexible and the body would have no shape.

Question 5

Bone Coverings

Answer 5

• Periosteum
  
  • Covers outside of bone
  • Two layers
• Endosteum
  
  • Lines marrow cavity
  • One layer

Question 6

Periosteum

Answer 6

• Two layers of connective tissue around bone
  
  • Fibrous Layer (Outer)
  • Osteogenic Layer (Inner)
• Perforating (Sharpey’s) fibers (collagen) anchor periosteum to the bone.
• Site of ligament, tendon attachment
• Large supply of nerves & blood vessels

Question 7

Fibrous Layer

Answer 7

• Outer
• Dense irregular connective tissue

Question 8

Osteogenic Layer

Answer 8

• Inner
• Osteoblasts- Bone-forming cells
• Osteoclasts- Bone-remodeling cells

Question 9

Endosteum

Answer 9

• Lines the medullary cavity
• Has osteogenic layer only
• Contains osteoblasts & osteoclasts

Question 10

4 Types of Bone Cells

Answer 10

• Osteoprogenitor
• Osteoblasts
• Osteocytes
• Osteoclasts

Question 11

Osteoprogenitor Cells

Answer 11

• Mesenchymal (stem) cells
• Divide to produce osteoblasts

Question 12

Osteoprogenitor Cells Found in:

Answer 12

• Periosteum (inner layer)
• Endosteum
• Lining of blood vessel passageways through bone

Question 13

Osteoblasts

Answer 13

• Immature bone cells
• Produce the osteoid
  
  • Uncalcified bone matrix
  • Process is called osteogenesis or ossification
• Promote calcium salt deposition in osteoid

Question 14

Osteocytes

Answer 14

• Mature bone cells
  
  • Formed from osteoblasts “trapped” by matrix
• Maintain bone matrix
• Participate in bone repair
  
  • Can devolve into an osteoblast or osteoprogenitor cell as needed

Question 15

Osteoclasts

Answer 15

• Specialized macrophages (type of white blood cell)
• Remove and recycle bone matrix (osteolysis/resorption)
  
  • Release acids and proteolytic enzymes
  • Important in regulation body fluid calcium and phosphate concentrations.

Question 16

What is the bone matrix made up of?

Answer 16

Protein fibers and ground substance (fluid)

Question 17

Articular Cartilage

Answer 17

• Hyaline cartilage covering portions of epiphysis that ‘articulate” (form joints) with other bone
• Lubricates joints and provides ease of movement/protection

Question 18

Compact Bone includes:

Answer 18

• Lamellae
• Lacunae
• Osteocytes
• Canaliculi
• Arranged into osteons

Question 19

Spongy Bone includes:

Answer 19

• Lamellae
• Lacunae
• Osteocytes
• Canaliculi
• Arranged into trabeculae

Question 20

General Functions of Bone

Answer 20

• Support
  
  • Framework for the body
• Storage of Minerals
  
  • Ca2+, PO-4 storage
  • Plays role in mineral homeostasis
• Blood Cell Production
  
  • Hematopoiesis
• Protection
  
  • Bones protect many internal organs
• Leverage
  
  • Muscles attach to bones
  • Several bones act as levers for greater movement

Question 21

Bone Tissue Composition

Answer 21

• Mostly intercellular matrix (osteoid)
• Matrix mineralized
  
  • 25% water
  • 25% protein fibers
  • 50% hyrdoxyapatites (calcium phosphate) salts
• Hardness v. Felxibility
• Collagen fibers (for flexibility)
• Minerals (calcium)
  
  • Provide rigidity
• Need both for strong bones

Question 22

Compact Bone

Answer 22

• Appears very dense
• Most of the bone mass in the body

Question 23

Spongy Bone

Answer 23

• Small struts of bone (Trabeculae)
• May appear randomly organized, but the trabeculae, like girders in a building, are generally oriented in the directions of stresses.

Question 24

Two Types of Ossification

Answer 24

• Endochondral
• Intramembranous

Question 25

Endochondral Ossification

Answer 25

• Bone replaces existing cartilage
• Most bones form this way
• Begins at week 4 of development

Question 26

Intramembranous Ossification

Answer 26

• Bone develops within sheets or membranes of connective tissue
• Begins at week 4 of development

Question 27

Endochondral Ossification Steps

Answer 27

1. Formation of Bone Collar
2. Cavitation of the Hyaline Cartilage
3. Invasion of Internal Cavities by the Periosteal Bud, and Spongy Bone Formation
4. Formation of the Medullary Cavity: Appearance of Secondary Ossification Centers in the Epiphyses
5. Ossification of the Epiphyses, with Hyaline cartilage remaining only in the epiphyseal plates and articular areas

Question 28

Intramembranous Ossification Steps

Answer 28

1. An ossification center appears in the fibrous connective tissue membrane.
2. Bone Matrix (osteoid) is secreted within the fibrous membrane.
3. Woven bone and periosteum form
4. Bone collar of compact bone forms and red marrow appears.

Question 29

Endochondral Growth

Answer 29

Makes Bones Longer

1. New Cartilage produced on epiphyseal side, pushes epiphysis from diaphysis
2. Chondrocytes enlarge
3. Cartilage ossified: chondrocytes die
4. Cartilage on the diaphyseal side replaced by bone

Question 30

Appositions Bone Growth

Answer 30

Growth in Width

• From the inside out
• Compact bone lining the medullary cavity is destroyed
• Osteoblasts from periosteum continue to add more bone to the outer surface.

Question 31

What is the primary hormone responsible for raising blood calcium levels? What does this hormone affect to make blood calcium levels increase?

Answer 31

Parathyroid Hormone

• Direct Effects
  
  • Stimulates production of osteoclast “growth factor”
  • Inhibits osteoblasts
  • Stimulates calcitriol production of kidneys (Calcitriol is hormonally active form of vitamin D)
    
    • Absorbs more dietary calcium, excretes less calcium

Question 32

What is the primary hormone responsible for lowering blood calcium levels? What does this hormone affect to make blood calcium levels decrease?

Answer 32

Calcitonin

• Direct Effects
  
  • Inhibits osteoclasts
  • No effect on osteoblasts
  • Inhibits kidneys
    
    • Absorbs less dietary calcium, excretes more calcium.

Question 33

Is the control of blood calcium levels positive or negative?

Answer 33

Negative

Question 34

Why is it dangerous for blood calcium levels to go too low?

Answer 34

<9 mg/dl: cells respond too much

• Heart arrhythmia (faster)
• Muscle paralysis

Question 35

Why is it dangerous for blood calcium levels to go too high?

Answer 35

>11 mg/dl: cells cannot respond

• Heart arrhythmia (slower)
• Muscle paralysis

Question 36

Calcium Ion Homeostasis

Answer 36

Required for nerve cell and muscle cell function

Question 37

Why have both Spongy Bone and Compact Bone?

Answer 37

• Distribution of Weight (spongy)
• Sturdiness (compact)