L9 Principles of Skeletal System

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

Skeleton function

Answer 3

Protection, support, movement, RBC production and metabolic reservoir

Question 4

How long does the bone development period last for?

Answer 4

week 8 and finishes at 20yo

Question 5

What is bone derived from?

Answer 5

mesoderm -> paraxial and lateral plate mesoderm

Question 6

Intramembranous ossification - what is it?

Answer 6

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 7

Endochondral ossification - what is it?

Answer 7

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 8

Ossification centres and plates in endochrondral ossification are…

Answer 8

primary in diaphysis and secondary in epiphysis

Epiphyseal plate (growth plate) exists between diaphysis and epiphysis

Question 9

Bone growth - what is it?

Answer 9

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 10

Bone penetrated by…

Answer 10

blood vessels at week 9

Question 11

Important vitamins and their roles include…

Answer 11

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

Question 12

Important hormones and their roles include…

Answer 12

Parathyroid hormone - hyperparathyroidism (calcitonin - thyroid)
Growth hormone - dwarfism and acromegaly

Question 13

What is cartilage? [4]

Answer 13

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

Question 14

What is bone? [4]

Answer 14

Hard form of CT
Provide ridged framework
Vascular
Compact (outside) and spongy

Question 15

What are the coverings of cartilage/bone called?

Answer 15

CT surrounding bone is called periosteum

CT surrounding cartilage is perichondrium

No CT where articulation needed

Question 16

Bone cell types include… [4]

Answer 16

Osteoprogenitor, Osteoblast, Osteocyte and Osteoclasts

Question 17

Compact bone - what is it?

Answer 17

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 18

Spongy bone - what is it?

Answer 18

Also known as cancellous bone

Irregular lamellae

Has red bone marrow surrounding it

Highly vascular

Question 19

What are the bone classifications?

Answer 19

Long (femur), Flat (skull), Irregular (vertebra), Short (carpals) and sesamoid (patella)

Question 20

What is the number of bones in the body?

Answer 20

270 Bones at birth, 206 by adulthood.

Question 21

Bones: skulls, spine, thorax, arm, pelvis and leg

Answer 21

Skull (29 including hyoid and inner ear)
Spine (26) –
Thorax- (25) Ribs- (24 in 12 pairs), sternum
Arm- (64) Scapula, Humerus, radius, carpals, metacarpals, phalanges
Pelvis- (2) made up of Ilium, ischium and pubis
Leg- (60) Femur, tibia, fibula, tarsals, metatarsals and phalanges

Question 22

What is a synovial joint?

Answer 22

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.

Question 23

What is a fibrous joint?

Answer 23

connected by collagen, they do

not permit movement e.g. sutures of skull.

Question 24

What is a cartilaginous joint?

Answer 24

connected by cartilage to

allow some movement e.g. growth plates,