bone structure and function

Question 1

name the 4 types of bones

Answer 1

long
short
flat
irregular

Question 2

describe long bones

Answer 2

longer than wide (easier to identify)

e.g. thigh, leg, arm, forearm, fingers & toes

Question 3

describe short bones

Answer 3

almost cube shaped
Most wrist & ankle bones (where long bones articulate)

Question 4

describe flat bones

Answer 4

thin & extensive surface (good place for storage)

e.g. Cranial bones, sternum, ribs & scapulae

Question 5

describe irregular bones

Answer 5

don’t fit above

e.g. vertebrae and some facial bones

Question 6

explain the macroscopic structure of long bones

Answer 6

Diaphysis- shaft of the bone

Epiphysis- terminal portion

Metaphysis-vascular region adjoining epiphyseal cartilage

Articular cartilage- situated at a joint where bones join

Periosteum-fibrous membrane

Medullary cavity - central hollow space

Endosteum- membrane lining inner cavity

Question 7

describe yellow bone marrow and red bone marrow

Answer 7

Yellow bone marrow is where we also store fat, within our bones

Red bone marrow is important in making blood cells, this is found in flat bones

Question 8

explain the microscopic structure of bones

Answer 8

Matrix:
25% water, 25% collagen fibres, 50% crystallized mineral salts - hydroxyapatite (hydrated calcium phosphate)

Osteogenic cells – found in periosteum develop into =>
Osteoblasts - secrete collagen fibres
- Build matrix and become trapped in lacunae (gaps in bone) to become =>
- Osteocytes - maintain bone

Osteoclasts – formed from monocytes (type of white blood cell)
- Digest bone matrix for normal bone turnover

Question 9

summarise the types of cells in bone tissue

Answer 9

osteogenic cell
(develops into an osteoblast)

to

osteoblast
(forms bone extracellular matrix)

to

osteocyte
(maintains bone tissue)

osteoclast
(functions in respiration, the breakdown of bone matrix)

Question 10

how much of the body mass is made up of compact bone structure

Answer 10

80%

Question 11

explain compact bone structure

Answer 11

gives good support to structure

few spaces, lies below periosteum

Individual Units = osteons (Haversian system)

Central canal- blood vessels, nerves, lymphatics

Concentric lamellae- layers of matrix

Lacunae- “lakes” contain osteocytes

Canaliculae- little canals
- nutrient flow from canals and between osteocytes

Question 12

explain the VOLKMANN’S (PERFORATING) CANALS

Answer 12

Complete the communication pathway from the outside of the bone to its interior.

• These run into the compact bone at right angles to the shaft. And move from the outside to the inside

Question 13

how much of the bodys mass is made up of spongy/cancellous bone

Answer 13

20%

Question 14

explain Spongy/cancellous Bone

Answer 14

Units containing trabeculae – little beams

Spaces between trabeculae often contain red marrow

No osteons but include lacunae & canaliculae

Its less compact

Its function is to provide storage space for red bone marrow

Question 15

what are the functions of bone

Answer 15

Support

Protection

Leverage - for motion (of arms, legs, etc)

Mineral Homeostasis e.g. calcium

Blood cell production
- Haemopoiesis in red bone marrow

Triglyceride (fat) Storage – yellow bone marrow

Question 16

how are blood levels of calcium controlled

Answer 16

by negative feedback loops

this is controlled by diff chemical messengers (hormones)

Question 17

name the hormones that control calcium homeostasis

Answer 17

parathyroid hormone

calcitriol

calcitonin

Question 18

describe how parathyroid hormone controls calcium homeostasis

Answer 18

produces increased osteoclast activity + decreased loss in urine, so we can access that calcium

Question 19

describe how calcitriol controls calcium homeostasis

Answer 19

calcitriol from kidneys increases absorption of calcium from the blood

Question 20

describe how calcitonin controls calcium homeostasis

Answer 20

Calcitonin from thyroid glands opposes parathyroid hormone => decreased osteoclast activity (stopping its production and promote loss of calcium in urine. Useful when less calcium is needed)