lymphoedema

Question 1

when does lymphoedema arise?

Answer 1

damage / dysfunction of the lymphatic drainage of a particular area of body

Question 2

why may lymphoedema arise?

Answer 2

removal of lymph nodes e.g. in treating cancer

Question 3

what is contained within the tissue fluid that drains from the interstitium into the lymphatic capillaries?

Answer 3

proportion of small proteins - making lymph fluid proteinaceous

Question 4

why do interstitium drains into the lymphatic capillaries?

Answer 4

leak from the arteriole end of capillary bed (high pressure) can’t return at venule end of the capillary bed, so enter the lymphatic system

Question 5

what happens if the lymphatic system is blocked / isn’t draining properly?

Answer 5

small proteins will accumulate within the interstitial space along with water - giving rise to protein rich fluid

Question 6

when does peripheral oedema occur? why

Answer 6

secondary to heart failure (higher than normal pressure at venule end of capillary due to impedance of venous return secondary to failing heart)

Question 7

what is the composition of oedema in peripheral oedema secondary to heart failure? why?

Answer 7

difference between oncotic (venule) and hydrostatic pressure (arteriole) is less, so a greater volume of tissue fluid remains in tissues –> tissue oedema (more watery)
more proteins stay in the capillary bed as lower hydrostatic pressure pumping them out

Question 8

why is there no SMALL proteins in oedema secondary to heart failure?

Answer 8

lymphatic drainage is not compromised in heart failure

small proteins within the interstitial space are still able to leave this space and not accumulate

Question 9

what else is absent in oedema secondary to heart failure?

Answer 9

no red blood cells as they are too large to permeate the capillary wall

Question 10

where does mental nerve arise from?

Answer 10

mandibular –> inferior alveolar (body of mandible, innervate gums/teeth on lower jaw ipsilateral side) –> mental nerve (sensory innervation to chin, lower lip, anterior gums + teeth)

Question 11

describe the pathway of the pupillary light reflex

Answer 11

optic nerve (CN II) –> pre-tectal nucleus –> E-W nucleus –> parasympathetic fibres on oculomotor nerve (CN III - ciliary ganglion) –> sphincter pupillae muscle of iris (less light onto back of retina, neural layer with rod + cone cells)

(parasympathetic innervates ciliary muscle of ciliary body as well for lens accommodation)