Bio 150- Skeletal System

Question 1

Components of theskeletal system

Answer 1

• Bones
• Cartilage: Mainly hyaline cartilage
• Tendons: Connect muscles to bones
• Ligaments: Connect bone to bone

Question 2

Functions of the skeletal system

Answer 2

• Support: framework to support body
• Protection: think – skull, vertebrae, ribcage…
• Movement: (with skeletal muscles) act as levers to move body (walk, breathe, etc)
• Storage: minerals (calcium, phosphate)- Related to electrolyte and acid-base balance
• Blood cell production: in the marrow cavity of certain bones

Question 3

Bone anatomy: shapes (6)

Answer 3

• Long: Longer than they are wide
• Short: Cube-shaped
• Flat: Thin, flattened, parallel surfaces, often curved
• Sutural bones: Found in the sutures
• Sesamoid bones: Found deep inside tendons
• Irregular: Don’t fit in the other categories

Question 4

Parts of a long bone (4)

Answer 4

-Diaphysis : Collar of compact bone, medullary cavity (marrow cavity) in middle
-Epiphysis: The “ends” of long bones- Compact bone, with spongy bone inside
-Epiphyseal line: Between epiphysis and diaphysis
Remnant of epiphyseal plate
-Epiphyseal plate: Disc of hyaline cartilage- During childhood, it grows to lengthen the bone

Question 5

Layers of a long bone (2)

Answer 5

Periosteum

Endosteum

Question 6

Periosteum

Answer 6

• Covers external surface of bone
• 2 layers (outer = dense irregular CT, inner = various cells…)
• Anchored to bone tissue by perforating (Sharpey’s) fibers
• Lots of blood vessels, nerve fibers, lymphatic vessels

Question 7

Endosteum

Answer 7

• Lines the inner surfaces of bone (even the canals, etc)
• Much thinner than periosteum
• An incomplete, cellular layer

Question 8

Parts of a long bone (2 types of bone)

Answer 8

-Compact (Haversian) bone
Outer layer, dense, strong

-Spongy (cancellous) bone
In epiphyses, and near marrow cavity
Honeycomb-like

Question 9

Articular cartilages

Answer 9

• Covers joint surface of the epiphyses
• Hyaline cartilage
• Cushions, absorbs stress between adjoining bone ends

Question 10

Marrow cavity (aka “medullary cavity”)

Answer 10

• In the diaphysis of long bone

- Most bone marrow is here

Question 11

2 types of Bone marrow

Answer 11

-Red marrow:
Hemopoeitic tissue (blood forming)
Present in basically all marrow cavities of infants
In adults, only present in spongy bone in head of femur + humerus, plus some flat bones (e.g., sternum), and irregular bones (e.g., hip bones)

-Yellow marrow:
Fat (think… why?)
Normally fills marrow cavities in diaphysis of adult long bone

Question 12

Spongy bone

Answer 12

• Honeycomb like
• Trabeculae are aligned along lines of stress
• Each trabecula is only a few cells thick, so easy for nutrients to diffuse to the osteocytes

Question 13

Microstructure of compact bone

Answer 13

-Haversian system/ Osteon

-3 types of layers (lamellae):
Concentric lamellae make up each osteon (to help resist twisting)
Interstitial lamellae
Circumferential lamellae

-2 Canals
Haversian (central) canal
Volkmann’s (perforating) canals

-Osteocytes in lacunae: Lacunae connected by canaliculi

Question 14

compact bone 3 types of layers (lamellae)

Answer 14

• Concentric lamellae make up each osteon (to help resist twisting)
• Interstitial lamellae
• Circumferential lamellae

Question 15

compact bone 2 canals:

Answer 15

• Haversian (central) canal

- Volkmann’s (perforating) canals

Question 16

compact bone Osteocytes in

Answer 16

lacunae

Question 17

Lacunae connected by

Answer 17

canaliculi

Question 18

Mineral salts

Answer 18

• Mainly calcium phosphates (mostly hydroxyapatite crystals)
• Tight packed crystals in the ECM
• Makes bone hard, able to resist compression

Question 19

Collagen fibers

Answer 19

Allows bone to be flexible, and able to resist tension

Question 20

Osteoblasts:

Answer 20

• Bone-forming cells
• Develop from osteogenic cells
• Make up endosteum and part of periosteum

Question 21

Osteocytes:

Answer 21

• Mature bone cells. Found in lacunae. Maintain bone matrix. Also monitor need for bone remodeling.
• Develop from osteoblasts (that get trapped in matrix)

Question 22

Osteoclasts:

Answer 22

• Bone-dissolving cells. Large. Different origin.

- Make up endosteum and part of periosteum

Question 23

bone cells make up bone tissue. Bone tissue plus other tissues (e.g., blood, nerves…) make up a bone, therefore a bone is a(n)

Answer 23

organ

Question 24

Bone formation and growth

Answer 24

• Intramembranous ossification

- Endochondral ossification

Question 25

Ossification:

Answer 25

- the formation of bone | - Involves calcification

Question 26

Calcification:

Answer 26

-the deposition of calcium salts within a tissue -Calcification occurs DURING ossification! (Other tissues could become calcified too…)

Question 27

Two different ways that bones can be formed: -Intramembranous ossification -Endochondral ossification Basic differences between these?

Answer 27

- In intramembranous ossification, the mesenchyme (embryonic tissue) differentiates into bone tissue directly - Endochondral ossification involves the formation of cartilage first. The cartilage is then transformed into bone tissue.

Question 28

Both intramembranous and endochondral ossification: | What do they have in common?

Answer 28

- Start out as mesenchyme - Osteoblasts are the first “bone cells”, and begin to form the matrix (which will become ossified) - Little spicules of bone form first. They are thickened and form trabeculae of spongy bone. This spongy bone can then be remodelled to form compact bone.

Question 29

Intramembranous ossification

Answer 29

- Trabeculae are formed (as already described) - Cancellous bone is formed, and red marrow develops in the spaces. - Surrounding cells form periosteum. - Can then be remodelled to form compact bone with cancellous bone center - Bones formed: most skull bones, part of the mandible, part of the clavicles

Question 30

Endochondral ossification

Answer 30

- Cartilage model is formed (hyaline cartilage) - Chondrocytes die out, osteoblasts develop… form a bone collar on the surface - Chondrocytes enlarge, matrix gets calcified, chondrocytes die - Blood vessels move in… - Osteoblasts form bone on the calcified cartilage… - Bones formed: base of skull, part of mandible, part of clavicles, and most other bones!

Question 31

Elongation of long bone

Answer 31

- Bones must grow by appositional growth (not interstitial growth) - Long bones: growth in length occurs at epiphyseal plate - Interstitial growth of cartilage, then appositional growth on surface of the cartilage

Question 32

Elongation of long bone: 5 regions/zones:

Answer 32

1: Zone of reserve cartilage 2: Zone of cell proliferation 3: Zone of cell hypertrophy 4: Zone of calcification (5: Zone of bone deposition)

Question 33

New bone is formed on the

Answer 33

diaphyseal side of the plate: more cartilage grows on the epiphyseal side (increase in length!)

Question 34

Bone remodeling and repair

Answer 34

- Bone is not a “dead”, fixed tissue! - 5-7% of your bone mass is recycled every week - Building up of new tissue (osteoblasts), and breaking down (osteoclasts)

Question 35

Gross Skeleton- 2 divisions:

Answer 35

Axial skeleton | Appendicular skeleton