Bone And Skeletal Growth

Question 1

Characteristics of the human skeleton and bone

Answer 1

• The human skeleton contains 10 – 12 kg of bone:
~ 1 – 2 kg of calcium (99% of the body total)
~ 0.5 – 0.75 kg of phosphorus (88% of the body total)
~ we require about 1 gram of each per day in the diet
~ 70% of bone is hydroxyapatite (calcium phosphate)

Question 2

Hydroxyapatite

Answer 2

Ca10(PO4)6(OH)2

Question 3

What % of the body is osetoid

Answer 3

-30% which is a matrix of collagen, hyaluronate, chondroitin sulphate, osteocalcin

Question 4

How much and why in the first place does bone receive cardiac output

Answer 4

-the bone is a connective tissue that is highly metabolically active
-receives 12% of the cardiac output at rest (600ml/min)

Question 5

List the types of bones

Answer 5

-long bones
-short bones
-flat bones
-irregular bones
-sesamoid bones

Question 6

Long bones

Answer 6

~ metacarpals, metatarsals phalanges, humerus, ulna, radius, tibia fibula

Question 7

Short bones

Answer 7

~ carpals and tarsals

Question 8

Flat bones

Answer 8

~ rib, scapula, skull, sternum

Question 9

Irregular bones

Answer 9

~ vertebrae and some facial bones

Question 10

Sesamoid bones

Answer 10

Patella

Question 11

Functions of the skeleton

Answer 11

• Mineral storage:
~ calcium and phosphate
• Support:
~ framework that supports the body and cradles soft organs
• Protection:
~ for delicate organs - brain, spinal cord, heart & lungs
• Movement:
~ bones act as attachment points and levers for muscles
• Blood cell formation:
~ bone marrow haematopoiesis

Question 12

Parts of the bone

Answer 12

• Cartilage protects the ends of long bones
• An epiphysis / metaphysis is found at each end
• The epiphyseal line is a layer of growing cartilage
• Trabecular bone is on each side of an Epiphyseal line
• The shaft is cortical bone
• The shaft contains bone marrow where red and white blood cells form

Question 13

Type of bone cells

Answer 13

Osteogenic
Osteoblasts
Osteocytes
Osteoclasts

Question 14

Osteogenic cells

Answer 14

Form osteoblasts

Question 15

Osteoblasts

Answer 15

Form new bone

Question 16

Osteocytes

Answer 16

Entrapped ‘osteoblasts’
Mature bone cells

Question 17

Osteoclasts

Answer 17

multinucleated cells that reabsorb bone using acids and enzymes

Question 18

What do bone slips into

Answer 18

Epiphysis
Diaphysis

Question 19

Epiphysis

Answer 19

-porous,high blood flow and high turnover

Question 20

Diaphysis

Answer 20

Shaft of bone.lower turnover,less porous

Question 21

Bone Growth in the Epiphyseal Plate (Bone Ends)

Answer 21

• Growing epiphyseal cartilage contain chondrocytes
➢epiphyseal bone growth is promoted by growth hormone (mainly during sleep)
➢sex steroid fuse the epiphysis towards the end of puberty preventing further growth
-Osteoblasts replace the chondrocytes and calcify the new bone matrix (osteoid)
-Osteoblasts become trapped in new calcified bone (osteoid) and become osteocytes with cellular inter-connexions

Question 22

Chondrocytes

Answer 22

-cells found in healthy cartilage
-maintain healthy matrix Which consists mainly of collagen and proteoglycans

Question 23

Endochondral ossification in long bones(creation of bone tissue)

Answer 23

1) Mesenchymal cells aggregate
2) Formation of cartilage model
3) Bone collar and primary ossification centre develop
4) Formation of marrow cavity
5) Epiphyseal cartilage begins ossification
6) Ossification of lower epiphyseal cartilage begins
7) Disappearance of epiphyseal cartilage & cessation of bone growth

Question 24

What does aggregate mean

Answer 24

Combine/colllect

Question 25

Bone remodelling

Answer 25

Watch lecture

Question 26

Trabecular bone and Osteoporosis

Answer 26

• Trabecular / cancellous bone contains thin struts of bone:
~ in osteoporosis trabeculae bone is reabsorbed faster by osteoclasts than it is reformed by osteoblasts causing bone thinning and greater fracture risks (eg neck of femur)

Question 27

Bone Marrow

Answer 27

Contains stem cells
• Produces osteoprogenitors
• Red bone marrow produces red and white blood cells
~ hematopoiesis forms
2.5 x 106 RBC per second
(2.5m)
~ stimulated by erythropoietin (hormone secreted by kidney)
~ survive 100 – 120 days
• Yellow bone marrow contains fat cells (more with age)
11
• Leukaemia is over production of white cells (several types)

Question 28

What is osteoporosis

Answer 28

-Caused by increased re absorption of bone without reformation
-osteoclastys reabsorbed ans nor reformed into osteoblasts

Question 29

Where are osteocytes found in

Answer 29

Canaliculi

Question 30

Which hormone inhibits bone reabsorption

Answer 30

Calcitonin