Ultrastructure of Blood Vessels

Question 1

What are the three main sections of blood vessel walls, from innermost to outermost?

Answer 1

Tunica intima
Tunica media
Tunica adventia

Question 2

What are the four main types of arteries, in order of decreasing size?

Answer 2

Large elastic (conducting) arteries
Medium muscular (distributing) arteries
Arterioles
Metarterioles

Question 3

What is the structure of the tunica intima of large arteries?

Answer 3

Endothelial cells
Thin subendothelium of connective tissue
Discontinuous elastic laminae

Question 4

What is the structure of the tunica media of large arteries?

Answer 4

40-70 fenestrated elastic membranes
Smooth muscle cells and collagen between lamellae
Thickest section

Question 5

What is the structure of the tunica adventia of large arteries?

Answer 5

Thin layer of connective tissue containing

• Lymphatics
• Nerves
• Vasa vasorum

Question 6

What are the vasa vasorum?

Answer 6

Blood vessels that supply blood to artery

Question 7

What is the structure of the tunica intima of medium arteries?

Answer 7

Endothelium
Subendothelial layer
Thick elastic lamina

Question 8

What is the structure of the tunica media of medium arteries?

Answer 8

40 layers of smooth muscle connected by gap junctions - allow coordinated contraction

Question 9

What is the structure of the tunica adventia of medium arteries?

Answer 9

Thin layer of connective tissue containing

• Minor vasa vasorum
• Lymphatics
• Nerve fibres

Question 10

What is the structure of arterioles?

Answer 10

Diameter <0.1mm
3 layers of smooth muscle cells
Absent internal elastic lamina

Question 11

What do metarterioles supply?

Answer 11

Capillary bed

Question 12

What is the structure of metarterioles?

Answer 12

No continuous layer of smooth muscle
Intermediate rings of smooth muscle located at certain points = precapillary sphincters > contract to control blood flow to capillary bed

Question 13

What is the structure of capillaries?

Answer 13

One layer of endothelium + basement membrane

Question 14

What are the three types of capillaries?

Answer 14

Continuous
Fenestrated
Sinusoidal

Question 15

What are the types of veins, in order of ascending size?

Answer 15

Postcapillary venules
Venules
Veins

Question 16

Into which type of vessel does tissue fluid drain?

Answer 16

Postcapillary venules

Question 17

What is the structure of postcapillary venules?

Answer 17

Endothelial lining
Associated pericytes
Diameter of 10-30 micrometres

Question 18

From which vessel type do white blood cells migrate?

Answer 18

Postcapillary venules

Question 19

What is the structure of venules?

Answer 19

Endothelium
Associated pericytes/thin smooth muscle cells > form very thin wall
Diameter of up to 1mm
Contain valves

Question 20

How does a vein differ from its accompany artery in structure?

Answer 20

Larger diameter
Thinner wall
More connective tissue
Fewer elastic and muscle fibres

Question 21

What is the structure of small and medium veins?

Answer 21

Well developed tunica adventia

Thin tunica intima and media

Question 22

What is the structure of large veins?

Answer 22

Diameter >10mm
Thicker tunica intima
Well developed longitudinal smooth muscle in tunica adventia
Circular smooth muscle in tunica media

Question 23

What is the function of valves within veins?

Answer 23

Prevent retrograde blood flow

Act together with muscle contraction to propel blood towards heart

Question 24

What are venae comitantes?

Answer 24

Deep paired veins wrapped together with an artery in one sheath