Limbs and back week 1 Flashcards

1
Q

Describe the blood supply to bone

A

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

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2
Q

Describe Volkmann’s canals

A

carry arteries into the cortex from the inside of the bone

these branch into small vessels of the central canals of osteons

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3
Q

How are the collagen fibres arranged in osteons?

A

In different directions from layer to layer - this gives strength

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4
Q

How is calcium obtained in the body?

A

mainly from dairy products in the diet

it is absorbed by the duodenum of the small intestine

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5
Q

What are the two major hormones that regulate calcium absorption?

A

vitamin D and parathyroid hormone (PTH)

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6
Q

Describe PTH

A

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

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7
Q

Describe the role of PTH

A

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

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8
Q

What is the overall effect of PTH?

A

hypercalcaemia
hypophosphataemia
high urinary phosphorus

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9
Q

How is the secretion of PTH regulated?

A

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

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10
Q

Describe vitamin D

A

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

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11
Q

Describe the actions of vitamin D

A

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

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12
Q

Describe calcitonin

A

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

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13
Q

Where is calcitonin secreted from?

A

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

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14
Q

Describe fibroblast growth factor 23

A

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.

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15
Q

Describe bone healing

A

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

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16
Q

What slows fracture healing?

A

if bone ends are mobile
infection
badly misaligned
avascular

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17
Q

describe osteoporosis fractures

A

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

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18
Q

What is the management of vertebral fractures?

A

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

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19
Q

What is osteoporosis?

A

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

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20
Q

What causes the bone to thin in osteoporosis?

A

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

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21
Q

How might osteoporosis present?

A

fragility fracture
loss of height
stooping deformity

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22
Q

What are risk factors for osteoporosis?

A
increasing age
female
steroid therapy
cushing's syndrome
immobility
alcoholism
diabetes
liver disease
smoking
23
Q

How is osteoporosis prevented and treated?

A

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

24
Q

Describe typical vertebrae

A

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

25
Q

At what level does the spinal cord end at?

A

L1 to L2

26
Q

What is kyphosis?

A

inward curve (naturally in lumbar and cervical spine)

27
Q

What is lordosis?

A

outward curve (thoracic spine)

28
Q

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

A

convex(occipital) , concave (atlas)

29
Q

What movement is allowed at the atlanto-occiptial joint?

A

flexion / extension

30
Q

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

A

almost transverse

31
Q

What movement is allowed at the atlanto-axial joint?

A

rotation

32
Q

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

A

oblique

33
Q

What movement is allowed in the cervical spine?

A

flexion / extension

34
Q

What is the facet orientation in the thoracic spine?

A

almost coronal

35
Q

What movement is allowed in the thoracic spine?

A

limited rotation

36
Q

What is the facet orientation in the lumbar spine?

A

almost saggital

37
Q

What movement is allowed in the lumbar spine?

A

flexion / extension

38
Q

Describe the ligaments in the vertebrae

A

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)

39
Q

describe IV disks

A

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

40
Q

what do IV disks contain?

A
phospholipase
prostaglandins
nitric oxide
metalloproteinases
inflammatory agents
41
Q

Describe concentric movement

A

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

42
Q

Describe eccentric movement

A

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

43
Q

Give examples of conditions that cause a loss of mineralisation

A

osteomalacia, rickets

44
Q

Give examples of conditions that cause a loss of bone mass

A

osteoporosis, osteogenesis imperfecta

45
Q

Give examples of conditions that cause a high bone turnover

A

pagets
hyperparathyroidism
thyrotoxicosis

46
Q

Give examples of conditions that cause low bone turnover

A

hypophostatasia

47
Q

Describe osteomalacia / rickets

A

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

48
Q

Describe paget’s disease

A
rapid bone turnover 
both resorption and formation increased
disorganised structure 
reduced bone strength 
risk of fracture
linked to osteosarcoma tumour suppressor gene
49
Q

describe corticosteroid induced osteoporosis

A

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

50
Q

Describe osteopetrosis

A

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

51
Q

Describe fluorosis

A

defective mineralisation

fluoride replaces calcium in the matrix

52
Q

Describe primary hyperparathyroidism

A
unregulated PTH secretion
hypercalcaemia
loss phosphate 
markedly increased bone turnover
may retain bone mass but often osteoporosis
53
Q

Describe osteogenesis imperfecta

A
genetic bone disorder
defect / deficiency in collagen I
various types
recurrent childhood fractures
deformities
low muscle tone
bluish sclerae
54
Q

Describe the causes of Rickets

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