Skeletal system

Question 1

What constitutes Axial skeleton?

Answer 1

skull, ribs, vertebrae, sternum. hyoid bone

Question 2

Appendicular skeleton?

Answer 2

limb bones and bones of pectoral and pelvic girdle

Question 3

Functions of the skeleton

Answer 3

• Protection of soft tissue organs
• supports the body
• Locomotion
• Haematopoesis
• metabolic resevoir
• Ca2+ regulation

Question 4

Bone development and embryology

Answer 4

begins at week 8 and ends at 20 years old.

derived from mesoderm

Question 5

Explain Intramembranous ossification: examples

Answer 5

Direct mineralisation of connective tissue (mesenchyme)

starts from primary ossification centre, cells divide and condense around capillary network.

grows radially until fuses together and replaces the connective tissue.

connective tissue that remains vascular becomes marrow

e.g. skull, mandible, clavicle

Question 6

Explain endochondral ossification

Answer 6

uses a cartilaginous mesenchyme template which is replaced by osteogenesis

primary ossification centre emerges in the diaphysis (middle of bone) and secondary ones in the epiphysis

initiates with a bone collar which develops into a 1ary centre

epiphyseal plate is between diaphysis and epiphysis, this has growth potential

Question 7

Bone growth

Answer 7

Bone remodelling - bone is partially reabsorbed and laid down again

long bones gradually lengthen via ossification

developing bone is penetrated by blood vessels at week 9

epiphyseal plate is abolished when mature

Question 8

Which nutrient are essential for Bone maintenance?

Answer 8

• vitamin A - bone remodelling
• vitamin C - connective tissue
• Vitamin D - calcium absorption
• Calcium and phosphorous

Question 9

How is Bone development controlled?

Answer 9

Endocrine system
- parathyroid hormone and calcitonin regulate the Ca2+ in the blood which is derived from bone.

• osteoclasts break down bone to release Ca2+ in response to PTH
• calcitonin is produced by thyroid and counters PTH

Question 10

Growth Hormones - Pathologies

Answer 10

produced by the pituitary gland
Deficiency - dwarfism
Excess - acromegaly

Question 11

Features of cartilage

Answer 11

• Connective tissue
• Avascular
• Found where flexibility is required
• Proportions of bone:cartilage change with growth

Question 12

Features of bone

Answer 12

• Hard form of tissue
• rigid framework
• Vascular
• Compact and spongy

Question 13

coverings of the skeletal system

Answer 13

Connective tissue covers the skeletal system except for articulations.

tissue around bone = periosteum
tissue around cartilage = perichondrium

Question 14

4 bone cell types

Answer 14

• Osteoprogenitor cells
• Osteoblasts
• Osteoclasts
• Osteocytes

Question 15

describe compact bone

Answer 15

• covered by periosteum
• made up of concentric inorganic matric called LAMELLA
• Haversian Canal is in the centre of lammellae and contain the vascular and nerve supply
• osteoblasts form the lamella and eventually get trapped in LACUNAE where they become osteocytes
• Canaliculi radiate from the lacunae which carries nutrients

Question 16

Describe Spongy bone

Answer 16

• Spongy bone also known as cancellous bone
• Irregular lamellae
• Has red bone marrow surrounding it
• Highly vascular

Question 17

Different types of bone (shapes)

Answer 17

long bones - humerus
flat bones - skull
irregular bones - vertebrae
short bones - carpals
sesamoid bones - patella

Question 18

Three classes of articulations

Answer 18

Synovial: have a joint capsule and a synocial cavity which contains synovial fluid for lubrication. can be classified into hinge, ball socket, saddle etc.

Fibrous joint: connected by collagen and cannot movement e.g. skull

Cartilaginous joint: connected by cartilage to allow some movement e.g. growth plates, inter-vertebral discs