U2 Lecture 1

Question 1

Functions of the skeletal system

Answer 1

1. Support
2. Protection from abrasions
3. Mineral storage
4. Triglyceride storage
5. Red and white blood cell formation (hemopoiesis)
6. Leverage (assistance in movement)

Question 2

Composition of the skeletal system

Answer 2

• The skeleton is all bones and connective tissues which attach them to each other (cartilage, ligaments, joints etc)

Question 3

What is unique of each bone?

Answer 3

Each bone is an organ containing osseous (connective) tissue, blood vessels, nerves, lymphatic vessels, cartilage, and connective tissue coverings

Question 4

What is found within bones?

Answer 4

• articular cartilage
• spongy bone (containing red bone marrow)
• red bone marrow
• epiphyseal line
• compact bone
• endosteum (lines medullary cavity)
• nutrient artery
• medullary cavity (contains yellow bone marrow in adults)
• periosteum

Question 5

Divisions of the skeletal system

Answer 5

Axial and Appendicular skeleton

Question 6

Types of bones

Answer 6

long (humerus), short (trapezoid, wrist bone), flat (sternum), irregular (vertebra), sesamoid (patella), sutural (skill bones), and pneumatized (ethmoid)

Question 7

Anatomy of flat bones

Answer 7

compact bone and spongy bone (diploe)

Question 8

Anatomy of sutural bones

Answer 8

• found between suture in the skull, not everyone has them

Question 9

Anatomy of long bones

Answer 9

• Sections: epiphysis, metaphysis and diaphysis

- Components: spongy bone, compact bone, endosteum, periosteum, medullary cavity and nutrient artery

Question 10

Importance of the endosteum and the periosteum

Answer 10

Important for bone growth and remodeling

Question 11

Define Periosteum

Answer 11

• Connective tissue membrane covering external surface of bone
• continuous with tendons, connective tissue of joints
• attached to bone matrix via perforating fibers

Question 12

Periosteum layers

Answer 12

1. Outer fibrous layer

2. Inner osteogenic layer

Question 13

Define endosteum

Answer 13

• Lining inner surfaces of bone including marrow cavity, trabecullae of spongy bone, canals of compact bone
• Contains osteogenic cells (important for bone growth and remodeling)

Question 14

Define osteology

Answer 14

The study of bone tissue

Question 15

Main composition of bone

Answer 15

Connective tissue

Question 16

What makes up connective tissue?

Answer 16

Extracellular matrix and cells

Question 17

What makes up the extracellular matrix?

Answer 17

Ground substance and fibers

Question 18

Define ground substance

Answer 18

Organic and inorganic compoents

Question 19

What type of fibers are found in the extracellular matrix?

Answer 19

Collagen fibers

Question 20

What are the 4 types of cells found within bones?

Answer 20

Osteogenic cells, osteoblasts, osteocytes and osteoclasts

Question 21

Define osteogenic (osteoprogenitor) cells

Answer 21

Stem cells that are formed from mesenchyme (embryonic connective tissue)

Question 22

What type of cells do osteogenic cells form?

Answer 22

Osteoblasts

• osteogenic cells go through mitosis to form daughter osteogenic cells and then differentiate into osteoblasts

Question 23

Define osteoblasts

Answer 23

Cells that form bone matrix and eventually builds bone

• They synthesize organic components of matrix and initiate calcification (takes calcium from blood and deposit it within matrix by exocytosis)
• They are immature cells

Question 24

What type of cells do osteoblasts form?

Answer 24

Osteocytes

Question 25

Define osteocytes

Answer 25

Mature cell involved in maintaining bone tissue

Question 26

Define osteoclasts

Answer 26

Break down bone for bone resorption - They release proteolytic enzymes and acids to degrade collagen and release minerals to blood - Formed from myeloid stem cells (not osteogenic cells)

Question 27

Define bone modeling

Answer 27

Bone is formed by osteoblasts without prior bone resorption - happens during growth - produces change in bone size and shape

Question 28

Define bone remodeling

Answer 28

Occurs when bone is first resorbed by osteoclasts and then formed in the same location by osteoblasts - happens throughout life

Question 29

Goal of modeling and remodeling

Answer 29

Achieve strength for loading and lightness for mobility - deposit bone where it is needed to achieve peak strength (during growth) - remove damaged bone where it's not needed to avoid bulk and maintain strength (during adulthood)

Question 30

Define fatigue damage

Answer 30

damage to bone after repeated loading and wear

Question 31

How do cells react to fatigue damage?

Answer 31

1. Osteocytes detect location and magnitude of damage 2. Osteoclasts remove damage 3. Osteoblasts replace it with new bone 4. Restores bone's material composition, micro- and macro-architecture

Question 32

Steps of bone remodeling

Answer 32

1. Activation: pre-osteoclasts are stimulated and differentiate under the influence of cytokines and growth factors into mature active osteoclasts 2. Resorption: osteoclasts digest mineral matrix (old bone) 3. Reversal: end of resorption, recruitment of osteoblasts 4. Formation: osteoblasts synthesize new bone matrix 5. Quiescence: osteoblasts become resting bone lining cells on the newly formed bone surface

Question 33

Osteoclast characteristics

Answer 33

1. Sealing zone 2. Ruffled Border 3. Functional Secretory Domain