WEEK 5 - SKELETAL SYSTEM 1

Question 1

What is the functions of the skeletal system?

Answer 1

• Support: Body
• Protection: Organs
• Movement: Skeletal muscles pull on bone
• Blood formation: Red bone marrow produces blood cells

Question 2

Storage in the skeletal system?

Answer 2

• Yellow (lipid) bone marrow (energy)
• Minerals
  ▪ electrolyte balance
  ▪ 99% of calcium (Ca2+) and phosphate in bones

Question 3

What are bones?

Answer 3

• Different tissues working together
  ▪ Bone (connective) – ‘osseous’. Cartilage (connective). Dense (connective)
  ▪ Adipose (connective). Epithelial. Nervous

Question 4

What are short bones?

Answer 4

• Equal in length and width.
• Glide across one another

Question 5

What are long bones?

Answer 5

• Longer than wide.
• Rigid levers acted upon by muscles

Question 6

What are flat bones?

Answer 6

• Protect soft organs.
• Curved but wide & thin

Question 7

What are irregular bones?

Answer 7

Do not fit into a category

Question 8

What are the two types of bone tissue?

Answer 8

1. Outer compact bone
2. Inner spongy bone

Question 9

What is outer compact bone?

Answer 9

• Smooth and solid
• Protective layer that stops marrow seeping out
• Attachment site

Question 10

What is inner spongy bone?

Answer 10

• Lattice of rods / plates (trabeculae)
• Strong but light, absorbs impact

Question 11

What is the structure of a compact bone?

Answer 11

Composed of cylindrical units called Osteons (strand of spaghetti)

Question 12

What is the strucure of osteons?

Answer 12

• Four to 20 hollow tubes (lamellae), one placed outside next, around a central canal
  (blood vessels)
• Collagen of lamellae are aligned
• But alignment is opposite in the adjacent lamellae
• Osteocytes occupy cavities between the lamellae
• Osteons orientated parallel to diaphysis of the long bone to give strength

Question 13

What are the structure of a spongy bone?

Answer 13

• Trabeculae (not osteons)
• Spaces filled with blood vessels and marrow
• Nutrients etc. diffuse from marrow to bone tissue

Question 14

What are the structure of a long bone?

Answer 14

1. Diaphysis (shaft)
2. Epiphysis (head)
3. Epiphyseal plate (growth plate)
4. Articular (hyaline) cartilage

Question 15

What is Diaphysis (shaft)?

Answer 15

Cylinder of compact bone

Question 16

What is Epiphysis (head)

Answer 16

• Enlarged ends to strengthen joint
• Attachment of ligaments and tendons

Question 17

What is Epiphyseal plate (growth plate) ?

Answer 17

• Hyaline cartilage separates epiphysis and diaphysis
  -Cartilage grows, then replaced with bone in youth
• Plate calcified in adult = Epiphyseal line

Question 18

What is Articular (hyaline) cartilage?

Answer 18

• Covers ends.
• Allows joint to move, friction free

Question 19

What cover and lines a bone?

Answer 19

1. Periosteum
2. Endosteum

Question 20

What is periosteum?

Answer 20

• Around outer compact bone
• Dense connective tissue, attaches to ligaments and tendons
• Vascular (500 mL/min), nerves (pain)

Question 21

What is endosteum?

Answer 21

Lines marrow cavity

Question 22

What is a red bone marrow (myeloid)?

Answer 22

• Haemopoietic. Reticular connective tissue
• Spongy bone of flat bones and epiphysis of long bones

Question 23

What is a yellow bone marrow?

Answer 23

• Lipid storage.
• Long bones

Question 24

How does bone form?

Answer 24

• Collagen framework laid down in extracellular matrix (ossification):
• 1/3 Next minerals (e.g., calcium phosphate) are deposited and crystallize (calcification): 2/3
  This crystal-protein interaction gives bone strength to resist compression and flexibility to resist
  tension or shattering

Question 25

What are the 4 types of bone cells?

Answer 25

1. Osteogenic cells 2. Osteoblasts 3. Osteocytes 4. Osteoclasts

Question 26

What are osteogenic cells?

Answer 26

- Derived from mesenchymal cells - These stem cells divide to produce daughter cells that differentiate into Osteoblasts - Bone side of periosteum and endosteum, central canals and epiphyseal plates

Question 27

What are osteoblasts?

Answer 27

- Secrete collagen and other components of extracellular matrix and initiate calcification - When surrounded by matrix becomes an Osteocyte

Question 28

What are osteocytes?

Answer 28

- Maintain bone tissue - Cells connected by channels (canaliculi) in matrix - Exchanges made between cells via gap junctions

Question 29

What are osteoclasts?

Answer 29

- Giant multinucleate cells - Bone side of periosteum or endosteum - Lysosome enzymes break collagen. - Hydrochloric acid dissolves minerals

Question 30

Bone is dynamic

Answer 30

- Collagen and minerals continually recycled and renewed through remodeling - Balance between osteoclasts and osteoblasts - Spongy bone replaced every 3 to 4 years, compact bone every 10 years

Question 31

Remodeling

Answer 31

- Gives each bone ability to adapt to stresses caused by body change - Shape of bones reflects forces applied to them ▪ Regular exercise important stimulus (tennis arm) ▪ Active and passive limb exercises