3.4.5- Blood vessels Flashcards
High absorption of salt from the diet can result in a higher than normal
concentration of salt in the blood plasma entering capillaries. This can lead to a
build-up of tissue fluid.
Explain how.
- (Higher salt) results in lower water potential of
tissue fluid; - (So) less water returns to capillary by osmosis
(at venule end);
OR - (Higher salt) results in higher blood
pressure/volume; - (So) more fluid pushed/forced out (at the arteriole
end) of capillary;
3 key features of arteries
1- Elastic fibers
- Folded endothelium
- Thick Muscle layer
What is the advantage of the thin endothelium of capillaries?
Short diffusion pathway
Relate the structure of the vessels to
their function.
● Arteries have thick walls to handle high pressure
without tearing, and are muscular and elastic to
control blood flow.
● Veins have thin walls due to lower pressure,
therefore requiring valves to ensure blood doesn’t
flow backwards. Have less muscular and elastic
tissue as they don’t have to control blood flow.
How is the structure of capillaries suited
to their function?
● Walls are only one cell thick; short diffusion pathway.
● Very narrow, so can permeate tissues and red blood
cells can lie flat against the wall, effectively delivering
oxygen to tissues.
● Numerous and highly branched, providing a large
surface area
What is tissue fluid?
A watery substance containing glucose,
amino acids, oxygen, and other
nutrients. It supplies these to the cells,
while also removing any waste materials.
How is tissue fluid formed?
As blood is pumped through increasingly
small vessels, this creates hydrostatic
pressure which forces fluid out of the
capillaries. It bathes the cells, and then
returns to the capillaries when the hydrostatic
pressure is low enough.
The volume of blood leaving the capillary network into the veins is less than the
volume of blood entering from the arteries.
Explain why. (1)
(Fluid) in tissue fluid / (fluid) in lymph.
What is the function of the coronary arteries?
- (Carry) oxygen / glucose;
Accept: oxygenated blood
Ignore references to removing waste products
Ignore references to arteries ‘pumping’ blood - (To) heart muscle / tissue / cells / myocytes.
Must be supply to heart or cardiac
The rise and fall in blood pressure in the aorta is greater than in the small
arteries. Suggest why.
(Aorta) 1. (is) close / directly linked to the heart / ventricle / pressure is higher / is very high; 2. (Aorta has) elastic tissue; Accept elasticity Ignore reference to muscle 3. (Aorta has) stretch / recoil. Q Reject: contracts / relaxes / pumps Accept: for mp 2 and mp 3, converse for small arteries if qualified by little / less
Although the speed of blood flow in an arteriole is greater than speed of blood flow
in a capillary, blood does not accumulate in the arterioles.
Explain why.
) 1. Many / more capillaries (than arterioles);
2. (Cross-sectional) area of capillaries (much) greater (than of arterioles).
Note: maximum of 1 mark for this question
The hydrostatic pressure falls from the arteriole end of the capillary to the venule
end of the capillary. Explain why.
(b) Loss of water / loss of fluid / friction (against capillary lining)
High blood pressure leads to an accumulation of tissue fluid. Explain how
- High blood pressure = high hydrostatic pressure;
- Increases outward pressure from (arterial) end of capillary / reduces
inward pressure at (venule) end of capillary; - (So) more tissue fluid formed / less tissue fluid is reabsorbed.
Allow lymph system not able to drain tissues fast enough
The water potential of the blood plasma is more negative at the venule end of the
capillary than at the arteriole end of the capillary. Explain wh
- Water has left the capillary;
- Proteins (in blood) too large to leave capillary;
- Increasing / giving higher concentration of blood proteins (and thus wp).
3
What are the four main components of blood? (4 marks)
a) i) Plasma Red blood cells/ erythrocytes White blood cells Platelets
