Limbs and back week 1

Question 1

Describe the blood supply to bone

Answer 1

vessels enter through epiphyses and periosteum
main supply from the nutrient artery somewhere in the middle of the shaft
Nutrient artery enters through the nutrient foramen

Question 2

Describe Volkmann’s canals

Answer 2

carry arteries into the cortex from the inside of the bone
these branch into small vessels of the central canals of osteons

Question 3

How are the collagen fibres arranged in osteons?

Answer 3

In different directions from layer to layer - this gives strength

Question 4

How is calcium obtained in the body?

Answer 4

mainly from dairy products in the diet
it is absorbed by the duodenum of the small intestine

Question 5

What are the two major hormones that regulate calcium absorption?

Answer 5

vitamin D and parathyroid hormone (PTH)

Question 6

Describe PTH

Answer 6

parathyroid hormone
most important regulator of calcium metabolism
secreted by chief cells of the parathyroid gland
secretion of PTH is increased on response to hypocalaemia and hyperphoshphataemia

Question 7

Describe the role of PTH

Answer 7

mainly acts on the bones and the kidneys
stimulates osteoclasts and increases bone resorption - increases serum concentrations of calcium and phosphorus
Stimulates the 1-alpha hydroxylase activity in the kidney, resulting in increased 1,25dihydroxyvitamin D production
Increases calcium reabsorption in the distal renal tubules
Increases phosphorus excretion by the kidney

Question 8

What is the overall effect of PTH?

Answer 8

hypercalcaemia
hypophosphataemia
high urinary phosphorus

Question 9

How is the secretion of PTH regulated?

Answer 9

calcium has a negative feedback effect in the parathyroid gland through calcium-detecting sensors

Question 10

Describe vitamin D

Answer 10

essential in the homeostasis of calcium and phosphorus
mainly synthesised in the skin but also through diet
Active form is called 1,25dihydroxyvitamin or calcitriol

Question 11

Describe the actions of vitamin D

Answer 11

a required factor for the bone resorption process
reabsorption of calcium and phosphorus from the renal tubules
Suppresses PTH secretion

Question 12

Describe calcitonin

Answer 12

calcitonin lowers serum calcium but normally only when it is pathologically elevated
its exact physiological action is unknown but it has an inhibitory effect on osteoclasts

Question 13

Where is calcitonin secreted from?

Answer 13

specialised parafollicular cells of the thyroid in response to high calcium levels

Question 14

Describe fibroblast growth factor 23

Answer 14

mainly secreted by osteocytes in response to hyperphosphataemia
increases phosphorus clearance in the kidney
inhibits the 1 -alpha hydroxalase enzyme so prevents the production of calcitriol.

Question 15

Describe bone healing

Answer 15

immediately after the fracture there will be a haemorrhage within the bone due to ruptured vessels in the marrow cavity, and also around the bone related to the periosteum
A haematoma at the fracture site facilitates repair by providing a foundation for the growth of cells
Deviated bone fragments and soft tissue damage is removed in the initial phase of repair, along with organisation of the haemoatoma
The capillaries will be accompanied by fibroblasts and osteoblasts - bone is deposited in an irregularly woven patten
the mass of new bone is called callus bone
within the medullary cavity - internal callus
at the periosteum - external callus
Woven bone is subsequently replaced by more orderly lamellar bone
lamellar bone is gradually remodelled according to the direction of mechanical stress

Question 16

What slows fracture healing?

Answer 16

if bone ends are mobile
infection
badly misaligned
avascular

Question 17

describe osteoporosis fractures

Answer 17

most likely to occur in the thoracic region of the spine
due to thinning of bone they can collapse
compression fracture - vertebral wedging
pain, increased kyphosis, immobility

Question 18

What is the management of vertebral fractures?

Answer 18

conservative
analgesics for pain
physiotherapy - increase mobility, weight bearing exercise

Question 19

What is osteoporosis?

Answer 19

a disease in which there is a reduction in bone mass in the presence of normal mineralisation

Question 20

What causes the bone to thin in osteoporosis?

Answer 20

a loss of coupling where bone resorption is greater than bone reformation

Question 21

How might osteoporosis present?

Answer 21

fragility fracture
loss of height
stooping deformity

Question 22

What are risk factors for osteoporosis?

Answer 22

increasing age
female
steroid therapy
cushing’s syndrome
immobility
alcoholism
diabetes
liver disease
smoking

Question 23

How is osteoporosis prevented and treated?

Answer 23

vertebral osteoporosis is reduced in women treated with hormone replacement therapy
biphosphonate drugs inhibit bone resorption and are more effective at preventing hip fractures
regular weight bearing exercise
dietary calcium intake

Question 24

Describe typical vertebrae

Answer 24

increase in size distally
pedicle and laminae connect to create vertebral arch
successive vertebrae stack on top of each other to form the vertebral canal
vertebral body anterior to spinous proces

Question 25

At what level does the spinal cord end at?

Answer 25

L1 to L2

Question 26

What is kyphosis?

Answer 26

inward curve (naturally in lumbar and cervical spine)

Question 27

What is lordosis?

Answer 27

outward curve (thoracic spine)

Question 28

What is the facet orientation at the atlanto-occipital joint?

Answer 28

convex(occipital) , concave (atlas)

Question 29

What movement is allowed at the atlanto-occiptial joint?

Answer 29

flexion / extension

Question 30

what is the facet orientation at the atlanto-axial joint?

Answer 30

almost transverse

Question 31

What movement is allowed at the atlanto-axial joint?

Answer 31

rotation

Question 32

What is the facet orientation in the cervical spine (C2-C7)?

Answer 32

oblique

Question 33

What movement is allowed in the cervical spine?

Answer 33

flexion / extension

Question 34

What is the facet orientation in the thoracic spine?

Answer 34

almost coronal

Question 35

What movement is allowed in the thoracic spine?

Answer 35

limited rotation

Question 36

What is the facet orientation in the lumbar spine?

Answer 36

almost saggital

Question 37

What movement is allowed in the lumbar spine?

Answer 37

flexion / extension

Question 38

Describe the ligaments in the vertebrae

Answer 38

C1 and C2 alar ligament and transverse ligament of dens. Holds dense of C2 against anterior arch of C1
around most vertebral bodies - anterior longitudinal ligament (broad), posterior longitudinal ligament (thin)
Around most laminae and posterior processes - supraspinous ligament, interspinous ligament, ligaments flavour (between laminae)

Question 39

describe IV disks

Answer 39

intervertebral disks
separate bodies
increase in size distally
important in absorption and dissipation of force
joint movement
disk is weakest posteriolaterally - annulation fibrosis
blood pumped through mechanical movement

Question 40

what do IV disks contain?

Answer 40

phospholipase
prostaglandins
nitric oxide
metalloproteinases
inflammatory agents

Question 41

Describe concentric movement

Answer 41

muscle tension sufficient to overcome the load - muscle shortens as in contracts

Question 42

Describe eccentric movement

Answer 42

insufficient muscle tension to overcome the force - fibres lengthen as they contract

Question 43

Give examples of conditions that cause a loss of mineralisation

Answer 43

osteomalacia, rickets

Question 44

Give examples of conditions that cause a loss of bone mass

Answer 44

osteoporosis, osteogenesis imperfecta

Question 45

Give examples of conditions that cause a high bone turnover

Answer 45

pagets
hyperparathyroidism
thyrotoxicosis

Question 46

Give examples of conditions that cause low bone turnover

Answer 46

hypophostatasia

Question 47

Describe osteomalacia / rickets

Answer 47

poorly mineralised osteoid
severe / long standing vitamin D deficiency
reduced availability of calcium and phosphate

Question 48

Describe paget’s disease

Answer 48

rapid bone turnover
both resorption and formation increased
disorganised structure
reduced bone strength
risk of fracture
linked to osteosarcoma tumour suppressor gene

Question 49

describe corticosteroid induced osteoporosis

Answer 49

increased osteoclastic activity
decreased osteoblastic activity
impaired collagen formation
increased bone turnover and poor bone formation and healing

Question 50

Describe osteopetrosis

Answer 50

failure of remodelling - decreased turnover
unregulated osteoblastic activity though not necessarily increased
impaired osteoclastic activity
dense but weak bones

Question 51

Describe fluorosis

Answer 51

defective mineralisation
fluoride replaces calcium in the matrix

Question 52

Describe primary hyperparathyroidism

Answer 52

unregulated PTH secretion
hypercalcaemia
loss phosphate
markedly increased bone turnover
may retain bone mass but often osteoporosis

Question 53

Describe osteogenesis imperfecta

Answer 53

genetic bone disorder
defect / deficiency in collagen I
various types
recurrent childhood fractures
deformities
low muscle tone
bluish sclerae

Question 54

Describe the causes of Rickets

Answer 54

nutritional
congenital
rickets of prematurity
neoplastic rickets
hypophosphataemia rickets
drug - induced rickets
renal causes - renal osteodystrphy, falcon syndrome
tumour induced osteomalacia