Blood vessels

Question 1

Distinguish between micro and macrovasculature

Answer 1

Micro: <0.1mm e.g. arterioles, capillaries, venules

Macro: >0.1mm e.g. arteries and veins

Question 2

What is meant by a portal system?

Answer 2

Blood carried from one capillary bed to another through

Question 3

What constitutes a portal venous system?

Answer 3

Both capillary beds and blood vessels connecting them

Question 4

2 examples of portal systems?

Answer 4

Hepatic portal system (GI tract to liver)

Hypothalamic pituitary system (hypothalamus to anterior pituitary)

Question 5

Features of arteries?

Answer 5

Thick muscular walls

Branch into arterioles

Round in histological section

Question 6

What is the role of the thick walls of the arteries?

Answer 6

Facilitate constriction and dilation to modulate blood pressure and flow

Question 7

What do capillaries do?

Answer 7

Distribute blood from arterioles throughout tissue (important exchange unit)

Question 8

What are features of capillaries?

Answer 8

Thin wall (one endothelial cell thick)

Don’t contract

Only have endothelium

Question 9

Describe course of veins from capillary bed

Answer 9

Drain capillary bed as venules, these converge to form veins carrying blood to heart

Question 10

What are features of veins?

Answer 10

Valves prevent retrograde flow/back flow

Some vascular smooth muscle (not as much as arteries)

Usually less circular/collapse in a section

Contraction of surrounding skeletal muscle aids venous return

Question 11

What aids venous return to heart?

Answer 11

Valves prevent back flow

Contraction of surrounding skeletal muscle aids venous return

Question 12

What are the 3 layers of walls of arteries and veins?

Answer 12

Tunica intima (endothelium)

Tunica media (muscular tissue/elastic)

Tunica adventita (connective tissue)

Question 13

Which layers are more developed in arteries than veins?

Answer 13

Tunica intima and media

Question 14

Endothelium is what sort of epithelial layer?

Answer 14

Squamous

Question 15

What is tunica intima composed of?

Answer 15

Single layer of squamous epithelial cells and basal lamina

Sub endothelial layer contains connective tissue and internal elastic lamina

Question 16

What separates tunica intima and media?

Answer 16

Internal elastic lamina of tunica intima

Question 17

What layer of blood vessel is thickest?

Answer 17

Tunica media

Question 18

What is tunica media composed of? (how is this different in large small arteries) (3)

Answer 18

Smooth muscle cells around lumen (in smaller arteries)

Replaced by elastic in elastic (larger) arteries

Type 3 collagen and proteoglycans dispersed within layers.

External elastic lamina

Question 19

What separates tunica media and tunica adventitia?

Answer 19

External elastic lamina of tunica media

Question 20

What is tunica adventitita composed of?

Answer 20

Fibroelastic connective tissue (fibroblast, type 1 collagen, elastic fibres, small blood vessels) arranged longitudinally with adipose tissue.

Blends with surrounding connective tissue

Question 21

How is the fibroelastic connective tissue arranged in the tunica adventitia?

Answer 21

Longitudinally

Question 22

True or false, external elastic lamina of tunica media is always distinguishable

Answer 22

False

Question 23

Where are internal elastic lamina and external elastic lamina found?

Answer 23

Tunica intima

Tunica media

Question 24

When is internal elastic lamina not visible?

Answer 24

Tunica media is muscular (smaller arteries)

Question 25

Where is tunica media not found?

Answer 25

Capillaries | Post capillary venules

Question 26

What is the blood supply to walls of large arteries and veins from?

Answer 26

Vasa vasorum

Question 27

What are vasa vasorum?

Answer 27

Small arteries entering and branching to supply walls of large arteries and veins

Question 28

What cells do vaso vasorum supply?

Answer 28

Tunica media and adventitia

Question 29

Why are vasa vorum prevalent in veins?

Answer 29

Blood contains less oxygen and nutrients, less received through diffusion

Question 30

Classify arteries by size (3 sizes)

Answer 30

Largest: Conducting arteries = elastic (elastic layers in tunica media + muscle) Middle: distributing arteries = muscular (smooth muscle in tunica media) Arterioles

Question 31

Give examples of elastic arteries

Answer 31

Pulmonary artery and aorta

Question 32

How do walls of aorta and pulmonary artery look, why?

Answer 32

Yellow, abundant elastin. Wall has thick layer of elastic (concentric layers) occupying most of tunica media

Question 33

What is benefit of elastic arterioles?

Answer 33

Stabilise blood flow and maintain arterial blood pressure

Question 34

How does composition of arteries change the further away from heart?

Answer 34

Less elastin and more muscular tunica media

Question 35

Give examples of muscular arteries?

Answer 35

Most vessels arising from aorta e.g. femoral

Question 36

Are elastic or muscular arterioles thicker?

Answer 36

Elastic

Question 37

What does muscular artery allow?

Answer 37

Selective distribution of blood to different organs and muscle tone to maintain blood pressure

Question 38

What type of cells support microvasculature?

Answer 38

Smooth muscle cells around arterioles, venules and small veins (discontinuous) Pericytes

Question 39

What is the function of pericytes?

Answer 39

Support and stabilise arteries and veins Regulate vascular tone Its processes wrapped around capillary endothelium

Question 40

What is unique about pericytes?

Answer 40

Are plastic and can differentiate to fibroblast, SMC and macrophages

Question 41

Describe diameter of arterioles

Answer 41

<0.1mm

Question 42

How many layers of SM do arterioles have?

Answer 42

1-2

Question 43

What does arteriole control, how?

Answer 43

Distribution of blood to whole capillary beds, through sympathetic autonomic nerves

Question 44

What are pericytes sensitive to?

Answer 44

Low oxygen

Question 45

What are pre-capillary sphincters?

Answer 45

Band of SM that adjust blood flow into capillary bed

Question 46

What are precapillary sphincters controlled by?

Answer 46

Local metabolic products

Question 47

3 types of capillary

Answer 47

Continuous, fenestrated, discontinuous (sinusoidal)

Question 48

Describe dimensions of capillary?

Answer 48

50 micrometer length, 8-10 micrometer diameter

Question 49

Describe structure of capillaries

Answer 49

Squamous epithelium (endothelium) walls only one cell thick Pericytes outside regulate blood flow Posses no smooth muscle

Question 50

Where are continuous capillaries found?

Answer 50

Skin, muscle, lungs, nerve tissue (i.e. where no need for protein passage)

Question 51

Describe feature of continuous capillaries in terms of pores, how come?

Answer 51

No pores in their walls - have junctional complexes so tight control of trans endothelial transport

Question 52

Describe permeability of continuous capillary

Answer 52

Moderate

Question 53

How can substances move across continuous capillary?

Answer 53

Active transport, diffusion

Question 54

Do capillaries exhibit vasomotor activities?

Answer 54

No

Question 55

Describe structure of fenestrated capillaries, including size of pores.

Answer 55

60-80nm pores, bridged by diaphragm

Question 56

What is a diaphragm (fenestrated capillary)?

Answer 56

Diaphragm consists of radially oriented fibrils that allows small molecules and limited amounts of protein to diffuse.

Question 57

What is fenestrated capillary permeable to?

Answer 57

Small ions and proteins

Question 58

Where are fenestrated capillaries found?

Answer 58

High water turnover tissue and where protein passage needed E.g. kidney, synovial joint, intestine, pancreas, , endocrine glands, anterior eye

Question 59

Describe sinusoidal capillaries structure

Answer 59

Discontinuous epithelial cells Large fenestrae without diaphragm (30-40 micrometer)

Question 60

Describe permeability of sinusoids

Answer 60

Permeable to proteins and cells (e.g. RBCs)

Question 61

Where are sinusoids found?

Answer 61

Bone marrow, liver, spleen , lymphoid organs

Question 62

What is the glycocalyx?

Answer 62

Structure made of GAGs that exists inside of the endothelium on the lumenal side

Question 63

What forms around the gylcocalyx and why?

Answer 63

GAGs have many negative charges (heavily sulfated) collect Na+ ions which lowers the water potential around the calyx, leading water to gather around to form a gel like substance.

Question 64

How much of the capillary lumen does the glycocalyx cover?

Answer 64

~1/10th

Question 65

Compare the connective tissue components of arteries and veins

Answer 65

More pronounced in veins

Question 66

Describe the boundary between tunica intima and media in veins

Answer 66

Not clear

Question 67

Describe structure of venule walls

Answer 67

Similar to capillaries, thin endothelium surrounded by reticular fibres and pericytes

Question 68

What forms the valve in veins?

Answer 68

Folds of the tunica intima

Question 69

Describe structure of medium veins

Answer 69

<1cm SMC of tunica media loosely organised with collagen fibres and fibroblasts Tunica adventita is thickest layer (contains collagen and elastic)

Question 70

Describe diameter of arterioles and medium vein lumen

Answer 70

Medium vein lumen wider

Question 71

Describe structure of large veins in terms of layers

Answer 71

Tunica media thin Tunica adventitia well developed