CVS 2.1 - Histology Of CVS

Question 1

What is the pathway of blood from the capillaries back to the heart?

Answer 1

• Capillaries
• Post Capillary Venules
• Venules
• Medium Veins
• Large Veins
• Heart

OR LYMPHATIC SYSTEM

Question 2

What effect does a low cross sectional area have on the rate of blood flow?

Answer 2

Causes a high rate of blood flow

Question 3

What is the significance of capillaries having a high total cross sectional area?

Answer 3

Causes a slow rate of blood flow therefore ensuring efficient gas exchange

Question 4

What happens during systole?

Answer 4

• Left ventricle contracts
• Blood pressure in aorta increases (to around 120mmHg)
• Walls of elastic aorta stretch

Question 5

What happens during diastole?

Answer 5

• Aortic semilunar valve closes
• Aorta walls recoil
• Pressure is maintained and blood is moved towards smaller vessels
• Pressure drops to around 70-80mmHg

Question 6

What are the three layers of blood vessels?

Answer 6

• Tunica intima (closest to lumen)
• Tunica media
• Tunica Adventitia

Question 7

Describe the tunica intima of elastic conducting arteries

Answer 7

• Simple squamous epithelium

- Narrow subendothelium of connective tissue

Question 8

Describe the tunica media of elastic conducting arteries

Answer 8

• Has 40-70 fenestrated elastic membranes

- Smooth muscle and collagen are between lamellae

Question 9

Describe the tunica adventita of elastic conducting arteries

Answer 9

• Thin fibroelastic connective tissue

- Contains vasa vasorum, lymph vessels and nerve fibres

Question 10

Describe the tunica intima of muscular arteries

Answer 10

Same as elastic arteries but with the addition of a thick internal elastic Lamina

Question 11

Describe the tunica media of muscular arteries

Answer 11

• 40 Layers of smooth muscle cells

- Connected by gap junctions

Question 12

What is the significance of gap junctions in the tunica media of muscular arteries?

Answer 12

There can be quick transmission of depolarisation therefore the cont ratio is coordinated

Question 13

Describe the tunica Adventitia of muscular arteries

Answer 13

• Same as elastic but vasa vasorum isn’t very prominent

- Has unmyelinated nerve endings that release noradrenaline

Question 14

What is the significance of the unmyelinated nerve endings in the tunica Adventitia?

Answer 14

• Release noradrenaline
• Noradrenaline diffuses through fenestrations of the external elastic Lamina into external tunica media
• Depolarises smooth muscle cells

Question 15

Describe the structure of an arteriole

Answer 15

• Same three layers
• Tunica media has one smooth muscle cell around all endothelial cells
• No elastic external Lamina
• Tunica adventita is scarce

Question 16

What is an end artery and what is their significance?

Answer 16

• Terminal artery
• Supply blood to parts without significant collateral circulation e.g. Coronary artery, central artery to retina (absolute end artery)

Question 17

How are end arteries formed?

Answer 17

Progressive branching without connections with other arteries

Question 18

What is the function of metarterioles?

Answer 18

To supply blood to and control the rate of flow into the capillary bed

Question 19

Describe the structure of metarterioles

Answer 19

• Smooth muscle layer is not continuous

- Muscle cells are spaced apart and cover endothelium of the capillary (precapillary sphincter)

Question 20

What is the function of capillaries?

Answer 20

Gas and nutrient exchange

Question 21

Describe the structure of the capillary wall

Answer 21

Single layer of endothelium + basement membrane

Question 22

What are the three types of capillary?

Answer 22

• Continuous
• Fenestrated
• Sinusoidal/discontinuous

Question 23

Describe a Sinusoidal/discontinuous capillary. Where can they be found?

Answer 23

• Larger diameter so slower blood flow
• Gaps in walls so whole cells can move between blood and tissue
• Liver, spleen and bone marrow

Question 24

Describe a post capillary venule

Answer 24

• Similar wall to capillaries
• More permeable than capillaries
• Fluid drains in due to the decrease in pressure, except for inflammatory responses

Question 25

Describe a venule

Answer 25

• Tunica media begins to appear

- Smooth muscle begins to associate

Question 26

Describe the structure of a vein

Answer 26

• Larger diameter, thinner wall
• More connective tissue
• Fewer elastic and muscle fibres

Question 27

Describe the layers of small/medium veins

Answer 27

• Thin tunica intima
• Thin tunica media
• Well developed tunica adventitia

Question 28

Describe the layers of large veins

Answer 28

• Thicker tunica intima
• Less prominent tunica media
• Well developed Adventitia

Question 29

What are venae comitantes?

Answer 29

Deep paired veins that accompany arteries

Question 30

Describe how venae comitantes function

Answer 30

• Artery pulses

- Causes venous return in adjacent veins

Question 31

What is the pathway of blood from the heart to the capillaries?

Answer 31

• Heart
• Large (elastic/conducting) arteries
• Medium (muscular/distributing) arteries
• Arterioles
• Metarterioles
• Capillaries

Question 32

Describe continuous capillaries. Where can they be found?

Answer 32

• Cells are joined by tight junctions

- Most common (nervous, muscle and connective tissues etc)

Question 33

Describe fenestrated capillaries. Where can they be found?

Answer 33

• Disruptions on thin parts of endothelium bridged by a thin diaphragm (except renal glomerulus)
• Gut, endocrine glands and renal glomerulus