Histology

Question 1

Name the 3 layers of an artery

Answer 1

Tunica intima, media, adventitia

Question 2

What is the term used to describe the recoil effect of arteries during diastole - what is the benefit?

Answer 2

Elasticity: act as auxiliary pump -> propel blood into arterioles

Question 3

List the 3 types of arteries, which has the narrowest shape?

Answer 3

Elastic, muscular, arterioles - narrowest

Question 4

What is the role of elastic arteries

Answer 4

Conducting, widest, pressure reservoires that stretch and recoil to push blood

Question 5

What to muscular arteries do?

Answer 5

Distribute blood to arterioles

Question 6

What are vaso vasorum and where can they be found?

Answer 6

Vessels supplying other arteries, tunica adventitia

Question 7

Name features of an elastic artery’s intima, media, adventitia

Answer 7

Intima: endothelial cells with long axes parallel to artery, narrow subendothelial CT and discontinuous internal elastic lamina

media: many fenestrated elastic membranes, btwn is sm muscle and collagen, thin external elastic lamina may be present
adventitia: thin layers of fibroelastic CT, vaso vasorum

Question 8

Describe aortic dissection, why is it a medical emergency?

Answer 8

Blood created false lumen by diverting down media -> narrows blood flow in actual lumen

Question 9

Name characteristics of muscular artery’s intima, media, adventitia

Answer 9

Intima: thick internal elastic membrane

Media: layers of sm muscle connected by gap junctions -> coordinated contraction, prominent external elastic lamina

Adventitia: Same as elastic + lymphatic vessels and nerve fibres

Question 10

How/What stimulates vasoconstriction for muscular arteries?

Answer 10

NA -> sm muscle cells depolarised -> gap junctions in media

Question 11

Name 3 examples of end arteries

Answer 11

Renal, splenic, coronary

Question 12

Explain the flow pattern as you move a doppler ultrasound closer to arterioles

Answer 12

Triphasic flow:

1. systole: high velocity of blood flow
2. early diastole: -ve flow when blood hits arterioles/high peripheral resistance
3. Late diastole: low velocity; elastic recoil pushes blood into muscular arteries

Question 13

What is ABI, and what could make it higher?

Answer 13

Ankle-brachial index, stenosis in a leg artery

Question 14

Why do arterioles have such a high resistance?

Answer 14

Thin vessels, when sm muscle cells contract lumen sig narrows

Question 15

Name characteristics for an arteriole’s intima, media, adventitia

Answer 15

Intima: layer of endothelial cells, thin layer subendothelial CT and internal elastic lamina

Media: small arterioles media is single sm muscle cell

Adventitia: Scant, layers of fibroblasts

Question 16

What is a precapillary sphincter, what does it do and what does it feed into?

Answer 16

Single smooth muscle cell that contracts/dilates to control bloodflow into capillaries

-> metarterioles -> capillaries

Question 17

What happens if vasomotor tone increases/decreases

Answer 17

Increases: more contraction = higher flow resistance and vasoconstriction

Decreases: less contraction = lower flow resistance vasodilation

*deg of tension of sm muscle surrounding vessels

Question 18

If sympathetic controls vasoconstriction, what controls vasodilation? Name 3

Answer 18

Vasodilator metabolites: K+, H+ adenosine

Question 19

What is reactive hyeraemia and why does it occur

Answer 19

Transient increase in bloodflow following ischemia

Vasodilatory metabolites accumulate until washed away

Question 20

Name 2 characteristics of capillaries that aid their function

Answer 20

Minimal diffusion distance (single layer endothelia and BM, one RBC fills lumen)

Lowest blood velocity

Question 21

Name the 3 types of capillaries, what differentiates them? List some organs that have each

Answer 21

Differentiated by nature of their endothelial layer:

1. Continuous with pores: nervous, muscle, CTs, exocrine glands and lungs
2. Fenestrated: pts of gut, endocrine glands, renal glomerulus
3. Sinusoidal/discontinuous: cell movement: Liver, spleen, Bone Marrow

Question 22

Describe the histological appearance of small-medium vs large sized veins:

+ one exception

Answer 22

Thin-thick (large) tunica intima, thin media, well developed adventitia

Superficial veins: thicker media to resist distension from gravity

Question 23

What are venue comitantes?

Answer 23

Paired veins parallel to artery, use pulsations to propel blood

Question 24

What’s the formula for arterial pressure?

Answer 24

Arterial pressure = CO X TPR

Question 25

What characterizes a biphasic and monophasic waveform and what could cause each?

Answer 25

Biphasic: Mild stenosis, decreased systole, small -ve

Monophasic: Tight stenosis: systole decreased, no -ve flow as no regurg or recoil (walls much stiffer)