Lecture 4 - Arts And Veins

Question 1

Go and memorise the major arts and veins

Answer 1

Yeah

Question 2

What are the three layers of the blood vessel walls?

Answer 2

1. Tunica intima (innermost)
2. Tunica media
3. Tunica adventitia (externa)

Question 3

Tunica Intima

1. What are the three layers? And describe each

Answer 3

1. Endothelium
   A simple squamous epithelium which lines the lumen of all vessels (cells within this form the non-stick surface)
2. Sub endothelium
   A sparse pad of loose FCT cushioning the endothelium
3. IEL
   A condensed sheet of elastic tissue. The Internal Elastic Lamina is well developed in artistes and less developed in veins. It forms the boundary between intima and media

Question 4

Tunica Media

1. What kind of tissue is it?
2. What about the content of the connective tissue? To provide what?
3. Thickness is prop to?

Answer 4

1. Smooth muscle (SO CONTRACTS)
2. Variable content of connective tissue - mainly collagen and elastin (to provide structural support)
3. Thickness of the media is proportional to both the diameter and blood pressure
   E.g. Low pressure = thinned media (like veins) and vice versa
   If they have the same diameter and one has thicker media - you know it’s the artery because it has high pressure

Question 5

Tunica Adventitia (externa)

1. What is the tissue?
2. What’s the vasa vasorum?
3. What’s also found in this region?

Answer 5

1. Loose FCT with high content of collagen and variable amount of elastin (tensile outer sheet of collagen bonds throughout structure)
2. In larger vessels - vasa vasorum; “vessels of vessel.” Has its own blood supply and run through externa
3. Lymphatics and autonomic nerves are also found in this region - innervate muscle of media and run through adventitia

Question 6

What in arteries dampens pulsativity?

Answer 6

Elastin (more developed IEL in elastic artery closed to heart)

Question 7

Arterioles:

1. Function?
2. Changing the tone in the _____ _____ in these define _____ _____ and this is how we control ____ ____. So if restricted arterioles, you _____ pressure.

Answer 7

1. The resistance vessels of the circulation - determine blood pressure. Still have same three layers as arteries
2. Changing the tone in the smooth muscle (media) in these define peripheral resistance and this is how we control blood pressure. So if restricted arterioles, you increase pressure.

Question 8

Capillaries:

1. Function?

Answer 8

1. Site of exchange between blood and tissues

Question 9

Venules:

1. What are they?
2. What kind of valves do they have?

Answer 9

1. Start of the collection (drainage) system

2. Monoscuspid - will stop backflow (contraction of surrounding tissues can cause back flow)

Question 10

Veins:

1. Fucntion
2. What’s their histological structure?
3. What layers?

Answer 10

1. Low pressure, large volume transport system.
   - once blood gets to cap beds, loses pressure because SA up and we can’t get the pressure back unless goes to heart

One way (unidirectional) flow.

Capacitance vessels.
-Blood will pool in veins if e.g. stand too long (cap and art don’t)

2. Irregular, flattened shape with large lumen and thin wall (live veins aren’t flat but they collapse when no blood). They have spare capacity (can take up extra blood volume) so are capacitance vessels
3. Intima, Media (much thinner than arts bc low pressure - few layers of SM often in two distinct layers) and Adventitia (thickest layer*)
   * = lots of collagen - vein is capacitance vessel - has this ability to hold blood but at some point, it can’t hold anymore and the thing that defines when it can’t is the collagen in the adventitia (can’t stretch anymore)

Question 11

Vascular bundle

1. Three things it does and contains three things

Answer 11

1. Supply (arts), exchange (cap) and drain (veins)

Question 12

Varicose veins

Answer 12

Veins stretch (esp superficial because only adipose tissue around), then valves become leaky and so blood just falls back down so get blood pooling