Capillaries

Question 1

capillaries are made up of what type of cells?

Answer 1

single layer endothelial cells 0.5μm thick resting on basement membrane

– no smooth muscle but contractile elements in cells allow shape change

Question 2

what are the different kinds of capillary beds?

Answer 2

»Continuous: least permeable in skin, muscle, lungs,

cerebral circulation (allows for the blodo brain barrier)

» Fenestrated: commonest type & more permeable eg

in glomeruli, intestinal villi

» Discontinuous: most permeable - in bone marrow,

liver, spleen- facilitates the passing of large proteins)

Question 4

what is the function of the capillaries?

Answer 4

exchange of the gases (lipid soluble molecules like anaesthetic agents)

Lipid insouble molecules pass through pores (glucose, amino acids and drugs)

structure of capillaries restricts permeability to large lipid insoluble molecules particularly when protein is bound

Question 5

what do we call it when we have an increase of fluid in the interstitial space?

Answer 5

oedema

Question 6

how much water moves from capillaries into the interstitial space per day?

Answer 6

8L/day

Question 7

what structures are responsible for moving the interstitial fluid away from the interstial space and back into circulation?

Answer 7

filtration = reabsorption + lymph flow

Question 8

what controls the movement of fluid out of capillaries and into the interstitium?

Answer 8

water moves by osmosis (dilute to salty area)

• depends on the number of particles in the solution and obviously the colloid osmotic pressure

Question 9

what is the ‘colloid pressure’? (or oncotic pressure)

Answer 9

pressure exerted by big bulky proteins

Question 10

What is Starling’s Hypothesis?

Answer 10

capillary walls are leaky to water but impermeable to proteins -

Question 11

what did Startling’s Hypothesis determine?

Answer 11

it determined the forces determining capillary exchange

Question 12

what is the filtration coefficient?

Answer 12

it is the coefficient related to density and permeability of the capillaries

Question 13

if the pressure in your vessel increases, where does the fluid move?

Answer 13

into the interstitium

Question 14

if the pressure in your intersitial fluid increases - where does the fluid move?

Answer 14

into the vessel

Question 15

if you increase the colloid osmotic pressure in the vessel, where will the fluid move?

Answer 15

(colloid osmotic pressure = sucking force) - therefore the fluid will move into the vessel

Question 16

the natural gradiant of the vessels filters filtration?

Answer 16

yes - but it’s not uniform throughout

b/c the pressure at the arteriole end coming fromt he aorta is much higher

Question 17

how does the startling forces change in skeletal muscle, alveoli and glomeruli?

Answer 17

in skeletal muscle = gradient favoring filtration

the more the role of the organ is towards filtration, the higher the net gradient - so the alveoli we need to have stuff back in force all the time (gas exchange) so we really need filtration, and in the kidneys the same - so they have a higher net favoring filtration

Question 18

what is oedema?

Answer 18

• Increase in interstitial fluid volume due to alteration in one or

more of the Starling forces

• Pulmonary

• Leakage of fluid from pulmonary capillaries

– Breakthrough to alveoli

• Systemic

– Localised / generalised

– Sacral / ankle oedema

– Ascites or pleural effusion

Question 19

why do you get swollen ankles after a flight?

Answer 19

venous pooling in your ankles-leads to increased hydrostatic pressure in your vessels and a net transfusion of fluid across the wall and into the interstitial space

Question 20

what are the causes of oedema?

Answer 20

1. Lymphatic Blockage eg by fliaria nematodes

After radical mastectomy

2. Increased capillary hydrostatic pressure

Eg excessive kidney retention of salt & water

3.High venous pressure & venous constriction

Heart Failure

4. Decreased plasma proteins

Nephrotic Syndrome (plasma protein conc ( <2.5g/100ml)

Loss of proteins from denuded skin (burns)

Failure to produce proteins eg. Liver cirrhosis

5. Increased capillary permeablity

Immune reactions that cause relase of histamine & other immune products

Bacterial infections

Burns

Question 22

what happens in elephantiasis?

Answer 22

worms block the lymphatics after being transmitted by mosquito bite - and you can treat it with a metabolic inhibitor

Question 23

why does a radical mastectomy lead to a swollen arm?

Answer 23

b/c of damage to the axillary lymph nodes

Question 24

why do you see oedema in heart failure?

Answer 24

due to high venous pressure and venous constriction - attempt to profuse all organs

Question 25

why do burns lead to oedema?

Answer 25

because a burns cause a loss of proteins from denuded skin -therefore you get quick oedema blisters

Question 26

read this 2 pages in the guyton and hall medical physiology pg. 302- 304- she said it’s essentail clinically

Question 27

explain the mechanisms underlying the oedema which occurs in children suffering from protein calorie malnutrition

Explain the mechanisms underying the oedema which occurs in heart failure - differentiate between the oedema evident in left vs. right sided heart failure

*annette byrne like bullet points more than essay like questions*

Answer 27

last line is

“between the air and the blood. The consequences of this ar dyspnea (shortness of breath), orthopnea (shortness of breath when lying flat) and paroxysmal noctural dyspnea

Question 28

what is it called when there is fluid buildup in the abdominal cavity?

Answer 28

ascites

Question 29

in left sided heart failure, where will fluid buildup?

Answer 29

in the lungs

Question 30

in right sided heartfailure, where does blood pool?

Answer 30

in the venous sytem

Question 31

what is orthopnea?

Answer 31

shortness of breath that occurs when lying flat

Question 32

a patinet with the nephrotic syndrome develops generalized oedema. Which one of the following is likely to be present?

A. Decrease in interstitial fluid hydrostatic pressure

B. Increase in capillary hydrostatic pressure

C. Decrease in lymph flow

D. Decrease in plasma oncotic pressure

E. Increase in filtration coefficient in skin capillaries

Answer 32

D. due to decrease in plasma oncotic pressure