Blood Vessels

Question 1

Function of Arteries

Answer 1

Transport blood away from thr heart at high pressure to tissues all aroudn the body - oxygenated blood

Question 2

Which arteries are somehwat anomalous?

Answer 2

Pulmonary artery and umbikical artery carry deoxygnated bloow (from foetus to palcenta)

Question 3

Adaptations of arteries

Answer 3

Thick Tunica Media - layer of muscle - strengthens arteries to witshtand high pressure and also contract and narrow the lumen for reduced blood flow
Elastic tissue helps maintain blood pressure by recoiling and stretching to even out fluctuations in pressure
Tunica adventita covers exterior (collagen) and is a strong protein that protects the arteries from damage by over stretching

Question 4

Arteries lumen

Answer 4

Narrow go maintain high blood pressure

Question 5

What is the endothelium in arteris?

Answer 5

Tunica intima - 1 cell layer thick ; lining of artery which is smooth to allow easy blood flow

Question 6

Aorta width

Answer 6

0.4 - 2.5 cm

Question 7

Arterioles function

Answer 7

Link thr arteries and capillaries together and can control the blood flow to individual organs - improtant role in thermal homeostasis through vasoconstruction and vasodilation + cutting off blood flow to specific organs

Question 8

Adaptations of arterioles?

Answer 8

Lower proportion of elastic fibres due to the weaker blood pulse/surge
Larger muscle tissue allowing contraction and dilation to control blood flow
When smooth muscle contracts it constructs the bessel and prveents blood flow into a capillary bed - VASOCONSTRICTION
When smooth muscle relaxes blood flows into capillary bed and this is vasodilation

Question 9

Function of capillaries?

Answer 9

Form networks that are very important exchange surfaces - provide a hgih cincentrstion gradient (lots of blood) and a short diffusion distance. They link atrteioles with venules - mainly nlood entering capillaries is oxygenated and by the time it leaves for venules it is deoxygenated ; lungs and placenta are exceptions to deoxugenated blood entering snf oxygenate blood leaving to venules

Question 10

Adaptations of capillaries

Answer 10

Thin walls (endothelial cells) which wre leaky - allowing substances to leave the blood and reach the body tissue
Very small lumen which force blood to travel slowly (more diffusion time) - WIDER THAN ARTERIOLES
Many capillaries branch between cells allwoing substances to be diffused between blood and cells quickly due to short diffusion distance
Wall of capillary is solely made from endothelial cells - reducing diffusion distance for gaseous exchange

Question 11

Adaptations in structure

Answer 11

WBCs can combat infection in affected tissues by squeezing through the intercellular junctions in capillary walls and they have gaps allowing blood plasma to leak out and form tissue fluid (piles)
TOTAL SURFACE AREA GREATER THAN ARTERIOLAR SO RATE OF BLOOD FLOW FALLS

Question 12

Function of venules

Answer 12

Connect capillaries to veins - no elsstic finre or lumen due to weak blood pressure ; deoxygenated blood flows through capillaries into venules and finally reaching the inferior/superior vena cava

Question 13

Adaptation of venules

Answer 13

Very thin walls with no smooth muscle + no elastin - diameter of 0.1mm for efficient blood flow

Question 14

Veins function

Answer 14

Carry blood towards the heart (mostly deoxygenated - pulmonary vein and umbilical vein are 2 exception) - veins have no pulse as the surges from the hesrt pumpjng are lost as the blood passes through the narrow capillaries but they do hold a large reservoir of blood (60% at any time) and blood in veins low pressure must move against gravity

Question 15

Adaptations of veins?

Answer 15

Valves - backflow and mixing of blood prevention
Wide lumen and thin endothelial lining = low pressure and smooth blood flow
One way valves - means that when blood flows into hesrt the vslves open so blood can pass through
Bigger veins run between active muscles - when they contract they force the blood towards the heart snd when muscles relax vice versa
Breathing movements and pressure differentials - move blood in the veins of the chest and abdomen towards the heart
Large lumen = reduced friction between blood and endothelial layer
Rate of blood flow is slower but folume of blood followed is the sams

Question 16

Properties of veins

Answer 16

Blood pressure in veins is very low compared with the arteries
Valves to prevent backflow
Lots of collagen and little elastic fibre - vessels have a wide lumen and a smooth lining (endothelium) so blood flows smoothly

Question 17

Properties of venules

Answer 17

No elastin and no smooth muscle

Question 18

Adaptations that allow deoxygenated blood to be returned to the heart under low pressure and against gravity

Answer 18

1) Majority if veins have one-way valves at intervals ; flaps in the inner lining when blood flows in the direction of the heart, the valves open so blood can pass through and if blood starts to flow backwards rhey close
2) many big veins run betweeb muscles which contract and squeeze fhe veins to force blood towards rhe heart (valves prevent backflow when muscles relax)
3) breathing movements in chest act as a pump ; pressure changes and the squeezing actuons move blood in the veins of the abdomen towards the heart

Question 19

What is special about arterioles and capillaries

Answer 19

Capillaries Cross Section is greater than arteriole supplying them so rate of blood flow falls - this slow movement allows more time for exchange of magerials by diffusion between blood and the cells