1) Skeletal System

Question 0

Described the functions of the skeleton (3)

Answer 0

• STRUCTURE (body shape, support and protection)
• MECHANICAL (act as levers so muscles can bring about movement)
• PHYSIOLOGICAL (haemopoiesis, mineral and lipid store)

Question 1

Describe the 2 divisions of the skeletal system

Answer 1

-AXIAL
skull, vertebrae, sternum and ribs
-APPENDICULAR
Upper and lower limbs, pectoral and pelvic girdles

Question 2

Bone formation, endochondral?

E.g long bones - femur

Answer 2

Endochondral -
1) cartilage enlarges interstially + appositionally, nutrient artery penetrates
2) osteogenic cells -> osteoblasts secrete bone matrix = Primary oss. centre to form trabecular diaphysis
Born - epiphyses form with 2nd oss. centre and have epiphyseal growth plates (visible in x ray) articulating surfaces remain when an adult (no perichondrium not at these surfaces)

Question 3

Bone disorders

Answer 3

1) Osteogenesis Imperfecta - AD abnormal collagen type 1, fragile bones - long bones fracture, deformed bones - if severe die in utero and medical legal relevance
2) Rickets - calcium deficiency, poorly calcified bone matrix, epiphyseal growth plates distorted, bowing legs, muscle pain and weakness
3) Osteomalacia - Calcium and Vit D deficiency (diet/sunlight), inadequate mineralisation of bone - muscle pain, weakness
4) Achondroplasia - AD Homozygous is fatal, FGFR3 mutation in collagen, low proliferation of Chondrocytes, impaired longitudinal growth of long bones leads to dwarfism
5) Osteoporosis - low bone density, ^Osteoclast:Osteoblast, fragile bones and fractures. Risk factors, post menopause, ethnicity, diet, smoking

Question 4

Ca2+ control

Answer 4

PTH - short term to increase calcium
Calcitriol - long term to increase calcium, formed from Vit D
Vit D -> Calciferol (store due to higher half life) -> Calcitriol
Skin/diet -> Liver -> Kidney
(Calcitonin)
Effectors: Bone, Kidney, GI (secrete and reabsorb calcium)

Hyper: Moans (depressed), stones, groans (constipation)
Hypo: Hyperexcitability of nervous system (parasthesia, tetany)

Question 5

Define a joint and the types of joints with examples

Answer 5

-articulation between 2 or more bones
-FIBROUS (little movement) e.g gomphosis, sutures, syndesmosis
-CARTILAGINOUS (hyaline, elastic or fibrous)
-SYNOVIAL
Hyaline cartilage form articulating surfaces, absent on X-Ray
Joint capsule (outer fibrous lining and inner synovial membrane secretes synovial fluid)
E.g HINGE (elbow, humeroulnar)
SADDLE (carpometacarpal)
PLANE GLIDING (acromioclavicular)
CONDYLOID (metacarpophalageal or wrist)
BALL AND SOCKET (hip and shoulder)

Question 6

Bone formation, intramembranous?

E.g flat bones - clavicle, skull

Answer 6

1) 1st oss. centre - mesenchymal cells -> osteoblasts secrete osteoid later calcified to form hydroxyapatite
2) Primitive osteons form around blood vessels to form trabecular bone
3) osteoblasts trapped in lacunae -> osteocytes
4) peripheral bone becomes compact bone
5) periosteum (CT) surrounds the bone