Lecture 6 - Circulatory system anatomy - arteries and veins

Question 1

Major arteries pathway - leg

Answer 1

Common iliac artery - external iliac artery - femoral artery - popliteal artery - posterior tibial artery - plantar arch (all deep)

Question 2

Aortic bifurcation

Answer 2

Where the aorta forces into the left and right iliac arteries

Question 3

Major veins pathway - leg

Answer 3

Plantar venous arch - posterior tibial veins - popliteal vein - femoral vein - external iliac vein - common iliac vein (joins up to the inferior vena cava)

Question 4

Great sephaneous vein

Answer 4

Superficial vein (medial), longest vein

Question 5

Histological structure of the blood vessels

Answer 5

Blood vessels have a 3 layered wall - 
Tunica intima (inner)
Tunica media (middle) 
Tunica adventitia (externa) (external layer)

Question 6

Tunica intima

Answer 6

Endothelium: thin, flat sqaumous endothelium cells which line the lumen
Sud-endothelium: loose FCT which cushions the endothelium
Internal Elastic Lamina(IEL): elastic tissue which forms the boundary between the intima and media
IEL = more developed in arteries
= less developed in veins - rich in elastin protein

Question 7

Internal Elastic Lamina

Answer 7

nternal Elastic Lamina(IEL): elastic tissue which forms the boundary between the intima and media
IEL = more developed in arteries
= less developed in veins - rich in elastin protein

Question 8

Tunica media

Answer 8

Smooth muscle is layered throughout the media, SM is unstriated and surrounded by CT
- elastin provides recoil, return to original diameter
collagen provides strength and stops over expansion
Thickness of the media is proportional to both vessel diameter and blood pressure
Thick = carrying blood at high pressure and thin = carrying blood at low pressure

Question 9

Tunica adventitia (externa)

Answer 9

• Loose FCT (forms a sheath around the blood vessel and stops over expansion) with a high content of collagen and variable amounts of elastin (depends on the blood vessel)
• In larger vessels the adventitia contains the vasa vasorum - the thickness of the media is such that you have to get blood vessels into the wall of the blood vessel, it is an organ system and therefore needs a blood supply, need to bring blood vessels in to supply the capillaries around the smooth muscle in the tunica media and we do this by coming in through the adventitia e.g. the aorta is very thick so has has this series of little vessels that run through the adventitia, dive down into the tunica media to supply the smooth muscle in the media and then there will be little veins that drain back along the same path and we call these vessels vasa vasorum
  Lymphatics and autonomic nerves are also found in this region - smooth muscle is involuntary but under autonomic control

Question 10

Vasa vasorum

Answer 10

The vasa vasorum is a network of small blood vessels that supply the walls of large blood vessels, such as elastic arteries (e.g., the aorta) and large veins (e.g., the venae cavae).

Question 11

Smooth muscle cells in blood vessels

Answer 11

Arranged in such a way that their long axis is running along the circumference of the vessel which is important because if that smooth muscle shortens, diameter of the lumen constricts

Question 12

Elastic artery vs muscular artery

Answer 12

elastic arteries: more elastic fibers and less smooth muscle in their tunica media;muscular arteries:more smooth muscle and fewer elastic fibers.

Elastic artery wall is much thicker

Question 13

Arteriole

Answer 13

Resistance vessels of the circulation - determine blood pressure

Question 14

Capillaries

Answer 14

Site of exchange between blood and tissues

Question 15

Order of blood vessels from smallest to largest

Answer 15

Capillaries, venules, arterioles, veins and arteries

Question 16

Venules

Answer 16

Converge to form veins, ultimately guiding the blood on its way back to the heart. As the capillaries converge, small venules are formed whose function it is to collect blood from the capillary beds (i.e., the networks of capillaries).

Question 17

Veins

Answer 17

Low pressure, large volume transport system - once we pass through the capillaries, the arterial pressure drops as we fo into the capillary beds and we can’t repressurise the blood so the venous drainage system, by necessity, has to be a low pressure system, has to drain the same volume out of the capillary bed as the arteries are pumping in, low pressure but has to deal with a large volume that is being supplied
One-way (unidirectional) flow - we do not want the used blood in the capillary beds being pushed back in
Capacitance vessels

Question 18

Histological structure of veins

Answer 18

Irregular, flattened shape with large lumen and thin wall - almost crinkled appearance to it because the vein is starting to collapse under its own weight because of the external diameter of the vessel and the walls are quite thin and the big empty space once the blood has been pushed out of it, it just starts to collapse under its own weight (post mortem)
Have spare capacity (can take up extra blood volume) = capacitance vessels
Three layers - intima, media and adventitia

Question 19

Layers of veins

Answer 19

1- intima
2- Media - much thinner than arteries - a few layers of smooth muscle (often 2 distinct layers)
3- Adventitia - often the thickest layer of a vein - limiting factor to pooling by having this thick adventitia layer (which also in turn stops damage to the venous valves)

Question 20

Vascular bundle

Answer 20

1 artery to 2 veins in order to get the same amount of blood transported out of the capillary bed as the amount of blood that goes into the capillary bed
Also a nerve present

Question 21

Valves in veins

Answer 21

• Prevents back flow of blood, compensating for low blood pressure
• mostly bicuspid valves

Question 22

What happens when there is a leaky valve in veins?

Answer 22

Varicose veins - creates a fluid column from the trunk all the way to the ankle, blood gets pressurised by the fluid column