T1L9 - Human Skeleton

Question 1

Axial

Answer 1

Skull, vertebrae, ribs, sternum and hyoid bone

Question 2

Appendicular

Answer 2

Limb bones and bones of pectoral and pelvic girdle

Question 3

Bone development period [3]

Answer 3

week 8 -> 20yo

Bone derived from mesoderm -> paraxial and lateral plate mesoderm

Question 4

Intramembranous ossification [6]

Answer 4

Direct mineralisation of CT (mesenchyme)

Cells divide and condense around capillary network

Starting point is called primary ossification centre

Grows radially -> fuse and replace CT

CT that remains is penetrated by blood cells and undifferentiated mesenchyme gives rise to bone marrow

Skull mandible and clavicle

Question 5

Endochondral ossification [5]

Answer 5

Cartilaginous template from mesenchyme
Template replaced by bone - osteogenesis
Different ossification centres emerge (primary in diaphysis and secondary in epiphysis)
Initially a bone collar is produced and this is where primary centre develops
Epiphyseal plate (growth plate) exists between diaphysis and epiphysis

Question 6

Bone growth

Answer 6

Associated with partial reabsorption of previously laid down bone and new bone
Long bone gradually lengthen as ossification continues
Developing bone is penetrated by blood vessels at week 9
Maturity = epiphyseal plate abolished

Question 7

Vitamins [3]

Answer 7

Vit A - bone remodelling
Vit C - CT
Vit D - Calcium absorption

Question 8

Bone development controlled by

Answer 8

endocrine activity

Question 9

Cartilage [4]

Answer 9

CT
Forms skeleton where flexibility is needed
Avascular
Proportion of bone to cartilage changes as individual develops

Question 10

Bone [4]

Answer 10

Hard form of CT
Provide ridged framework
Vascular
Compact and spongy

Question 11

Coverings [3]

Answer 11

CT element covers skeletal system
Except where articulation occurs

CT surrounding bone is called periosteum
CT surrounding cartilage is perichondrium

Question 12

Compact bone

Answer 12

Covered by periosteum
Lamella (concentric layers of inorganic matrix) laid by osteoblasts
Lamella forms harversian canal in centre
Haversian canal contains vascular and nerve supply
Osteoblasts become trapped and turn into osteocytes
Each osteocyte occupies its own lacunae
Radiating from each lacunae are minute canals (canaliculi)
Nutrients travel in the canaliculi to the osteocyte

Question 13

Spongy bone

Answer 13

Also known as cancellous bone
Irregular lamellae
Has red bone marrow surrounding it
Highly vascular

Question 14

Bone classification

Answer 14

Long, Flat, Irregular, Short and sesamoid

Question 15

Major bones

Answer 15

• 270 Bones at birth, 206 by adulthood. You will know them and the important features of them but over the next two years.
• Skull (29 including hyoid and inner ear)–Module 202
• Spine (26) – Modules 102, 203 and 204
• Thorax- (25) Ribs- (24 in 12 pairs), sternum –Module 102
• Arm- (64) Scapula- Module 102, Humerus, radius, carpals, metacarpals, phalanges-Module 204
• Pelvis- (2) made up of Ilium, ischium and pubis –Module 203
Leg- (60) Femur, tibia, fibula, tarsals, metatarsals and phalanges- Module 204

Question 16

Joints and articulations

Answer 16

• Bones need to join with other bones to facilitate movement or to provide protection.
  
  • Three classes of joints: Synovial, fibrous, cartilaginous
  • Synovial joints have a joint capsule and a synovial cavity, they permit movement. Further classified into six types: Plane e.g. Intercarpal, Hinge e.g. knee, Saddle e.g. carpometacarpal, Condyloid e.g. metacarpophalangeal, Ball and Socket e.g. hip, Pivot e.g. radioulnar.
  • Fibrous joints are connected by collagen, they do not permit movement e.g. sutures of skull.
  • Cartilaginous joints are connected by cartilage to allow some movement e.g. growth plates, intervertebral disc.