Lecture 8: skeletal system

Question 1

inorganic matrix makes up ____ of total bone mass and is made of ____ that deposit around collagen fibers; this is the principle source of ____ and _____

Answer 1

• inorganic matrix makes up 2/3 of total bone mass
• made up of hydroxyapetite crystals that deposit around collagen fibers
• principle source of rigidity and strength against compression

Question 2

organic matrix makes up ____ of total bone mass and is made of ____ (3); it provides _____ (2)

Answer 2

• organic matrix makes up 1/3 of total bone mass
• made of cells, collagen and intercellular matrix
• provides resistance to twisting and stretching and a degree of elasticity

Question 3

medullary cavity

Answer 3

• hollow space inside bones

Question 4

compact (cortical) bone (4)

Answer 4

• gives bone smooth and dense appearance
• primary component of long bone shafts
• outer surface of bones
• microscopic channels

Question 5

spongy (cancellous) bone

Answer 5

• contains wide spaces in bone that resemble “holes” in a sponge [holes are filled with red marrow]

Question 6

periosteum (2)

Answer 6

• outer CT covering

- entry point of nerves and vessels

Question 7

endosteum

Answer 7

• inner lining in medullary cavity within the bone

Question 8

osteocyte (3)

Answer 8

• mature bone cell
• lives in lacunae
• communicate via cytoplasmic projections outwards

Question 9

osteoblast (2)

Answer 9

• bone forming call

- produces osteiod

Question 10

osteoid

Answer 10

• organic component of bone matrix around which crystals form

Question 11

osteoclast (2)

Answer 11

• breaks down bone with enzymes

- resorption = freed minerals enter the bloodstream

Question 12

chondroblasts (2)

Answer 12

• cartilage forming cells

- lay down cartilage model that ossifies during development

Question 13

chondrocytes (2)

Answer 13

• mature cartilage cells

- both are active during phases of growth and repair

Question 14

osteon (3)

Answer 14

• basic functional and structural unit of mature bone
• long cylindrical structures parallel to long axis of bone
• arrangement allows them to withstand compression and torsion

Question 15

structural components of osteon (4)

Answer 15

• concentric lamellae
• haversian (central) canal
• canaliculi (small channels)
• perforating (Volkmanns) canals

Question 16

concentric lamellae

Answer 16

• concentric layers of bone surrounding Haversian canal

Question 17

haversian (central) canal

Answer 17

• contains nerves and blood vessels

Question 18

canaliculi (small channels)

Answer 18

• connect the cells in their lacunae to the central canal so nutrients can reach osteocytes and for communication of lacunae

Question 19

perforating (volkmanns) canals (2)

Answer 19

• connects haversain canals

- allows for entry/ exit of nerves and vessels

Question 20

bone has a very (poor/ rich) blood supply

Answer 20

• blood has a very rich blood supply

Question 21

ossification

Answer 21

• osteoblasts secrete osteoid

Question 22

calcification

Answer 22

• deposition of insoluble calcium salts and results in hardening of bone

Question 23

intramembraneous bone (4)

Answer 23

• osteoblast forms bone in CT membrane
• early in fetal development
• in bones required for protection
• flat bones of the skull

Question 24

endochondral bone formation (3)

Answer 24

• begins with hyline cartilage model which is gradually replaced with bone by osteoblast
• process can occur up till 25yo
• most of the skeleton formed this way

Question 25

nutritional requirements of bone growth (3)

Answer 25

- Ca and Ph salts - vitamins A and C = healthy osteoblasts - vitamin D = facilitates Ca absorption and transport

Question 26

parathyroid hormone

Answer 26

- stimulates osteoclasts and increases Ca absorption in GI system - body can withdraw from the mineral bank in bones

Question 27

calcitonin inhibits ____ which decreases ____, allowing Ca to be stored in skeleton; produced where?

Answer 27

- inhibits osteoclast = decreases bone resorption = allows Ca to be stored in skeleton - produces in thyroid

Question 28

sex hormones (2)

Answer 28

- stimulates osteoblasts | - estrogen and testosterone

Question 29

flat bone is composed of a layer of ____ surrounded by 2 plates of ____; ex (3)

Answer 29

- composed of a layer of spongy bone surrounded by 2 plates of compact bone - skull - sternum - ribs

Question 30

the shaft of the long bone is made of ____, and the ends are composed of ____; ex (3)

Answer 30

- the shaft of the long bone is made of compact bone [diaphysis] - ends are composed of spongy bone [epiphysis] - femur - humerus - phalanges

Question 31

short bone is composed of ____ surrounded by ____; ex (2)

Answer 31

- short bone is composed of spongy bone surrounded by compact bone - carpals (wrist) - tarsals (ankle)

Question 32

example of irregular bone

Answer 32

- vertebra

Question 33

sesmoid bones are ____; ex (1)

Answer 33

- sesmoid bones are filled with tendon | - patella

Question 34

components of a typical long bone (6)

Answer 34

- diaphysis - epiphysis - epiphyseal plate - medullary cavity - articular cavity - nutrient vessels

Question 35

diaphysis (2)

Answer 35

- shaft of long bone | - primarily compact bone = gives bone strength

Question 36

epiphysis (2)

Answer 36

- distal ends of long bone | - primarily spongy bone = sites of articulation

Question 37

epiphyseal plate (2)

Answer 37

- plate of cartilage in growing bone | - lengthwise bone growth

Question 38

medullary cavity (2)

Answer 38

- cavity with diaphysis | - yellow and red marrow

Question 39

articular cartilage (2)

Answer 39

- hyline cartilage on the ends of long bones | - protective covering

Question 40

nutrient vessels (2)

Answer 40

- blood vessels that penetrate the bone to supply it with nutrients - pass through nutrient foramen on surface of skeleton