8.2 Blood Vessels, Blood, Tissue Fluid & Lymph

Question 1

What are 3 examples of some of the components used in our blood vessels

Answer 1

1. collagen - for structure and support of vessels
2. smooth muscle - contracts or relaxes to change lumen shape
3. elastic fibres - stretch or recoil for vessel flexibility

Question 2

What is the structure of the artery

Answer 2

from outer to inner:
1. tough collagen
2. stretchy smooth muscle
3. flexible elastin fibres
4. endothelium lining of artery
5. lumen 
All to withstand the high pressure of blood passing through arteries/arterioles

Question 3

What are arterioles and what is their structure

Answer 3

Vessels that link the arteries and capillaries; they have more smooth muscle and less elastin than arteries as they have a little pulse surge, but can still constrict or dilate.

Question 4

What are capillaries

Answer 4

Tiny vessels that link arterioles to venules; so tiny RBC have to travel single file.

Question 5

Why is exchange of substances between tissue cells and blood

Answer 5

Because the gaps between the endothelial cells (that make up the capillary wall) are relatively large

Question 6

Is blood oxygenated when it leaves the venule end

Answer 6

It’s oxygenated going into the capillary from the arteriole but becomes deoxygenated, and full of carbon dioxide as it reaches the venule end.

Question 7

How are capillaries adapted for their role

Answer 7

1. provide large SA for diffusion
2. rate of blood falls as the total cross-sectional area of capillaries is always greater than arterioles = more diffusion time
3. walls are one endothelial cell thick

Question 8

Where does deoxygenated blood come from, to enter the veins and venules

Answer 8

From capillaries; capillaries –> venules –> larger veins

Question 9

What are the 2 vessels that carry dexoy. blood to the heart

Answer 9

Inferior and superior vena cava

Question 10

Do veins have a pulse

Answer 10

No, the pulse is lost when the blood goes into narrow capillaries

Question 11

Why do veins have valves but arteries don’t

Answer 11

to prevent backflow of blood as the pressure is lower in veins than arteries

Question 12

What is the structure of a vein

Answer 12

From outer to inner layers: compared to arteries

1. thinner layer of collagen
2. thinner layer of muscle
3. thinner layer of elastin
4. endothelium lining
5. wider lumen

Question 13

What are the 3 main adaption for veins to get blood back to the heart under low pressure

Answer 13

1. majority of veins have one way valves at intervals
2. many of the bigger veins run through big muscles so when they contract they help to squeeze the blood to the heart
3. breathing movements of the chest acts as a pump - the pressure changes moves blood to heart from chest and abdomen

Question 14

What is the main component of blood

Answer 14

yellow blood plasma

Question 15

What are the smaller components of blood

Answer 15

dissolved glucose and amino acids, 
mineral ions, 
large plasma proteins (albumin - important for maintaining osmotic potential of blood), 
fibrinogen
globulins (important for transport and immune system). 
platelets 
RBC 
WBC

Question 16

What is the function of the blood

Answer 16

1. oxygen to and CO2 from respiring cells
2. digested food from small intestine
3. waste from cells to excretory cells
4. hormone transport
5. platelets to wounds
6. cells and antibodies involved in the immune system

Also acts as a buffer to minimise pH changes and temp changes

Question 17

What is oncotic pressure

Answer 17

the tendency for water to move into the blood; it’s about -3.3kPa

Question 18

Why does water have a tendency to move into the blood

Answer 18

Plasma proteins have an oncotic effect, in which they cause the blood to have a high solute potential, resulting in a low water potential.

Question 19

What is hydrostatic pressure

Answer 19

As blood flows through the arterioles into the capillaries, it is still under pressure from the surge of blood pumped from the heart. It’s about 4.6kPa

Question 20

How is tissue fluid formed

Answer 20

the hydrostatic pressure is higher than the oncotic pressure so water is attracted in by osmosis, forcing fluid out of the capillaries. This fluid fills the extracellular space between the cells, called tissue fluid.

Diffusion happens between the blood and the cells through the tissue fluid.

Question 21

What causes hydrostatic and oncotic pressure to change

Answer 21

the movement of blood from the arteriole end to the venule end.
Hydrostatic decreases to around 2.3kPa but oncotic stays at -3.3kPa so it’s now stronger.
Water now rushes in the capillary towards the venous end. By the time the blood returns to the vein, 90% of the tissue fluid is back in the vessel.
oncotic pressure=-3.3kPa

Arteriole end: Venule end:
4.6kPa HP (high) 2.3kPa HP (low)
4.6-3.3=1.3kPa 2.3-3.3=-1.0kPa
fluid forced out = tissue fluid fluid rushes back in

Question 22

What happens to the remaining 10% of tissue fluid that doesn’t go back into the capillary

Answer 22

It is drained into the lymphatic system and becomes known as LYMPH

Question 23

What is different about lymph from tissue fluid and plasma

Answer 23

Has same composition but less oxygen and nutrients; contains fatty acids which have been absorbed from the small intestine.

Question 24

Where does the lymph fluid join the blood plasma again

Answer 24

After being transported around the body, through larger vessels that have valves to prevent backflow, they enter the left and right SUBCLAVIAN veins (under the clavicle)

Question 25

What builds up in the lymph nodes around the body

Answer 25

lymphocytes which produce antibodies which go into the blood to be transported around

Question 26

Why is the lymphatic system important

Answer 26

It intercepts debris and bacteria in the lymph to be ingested by phagocytes found in the nodes so plays a major role in the immune system/defence mechanisms of the body.

Question 27

What do enlarged lymph nodes indicate

Answer 27

The body is fighting off a pathogen