Capillary Function

Question 1

What is a metarteriole

Answer 1

Connects terminal arterioles, precapillary sphincters directly to the capillary bed

Question 2

Describe the order of the vessels in the microcirculation

Answer 2

• Small arteries
• First-order arterioles
• Terminal arterioles (precapillary spinsters)
• Capillaries
• Venules

Question 3

What do capillary beds arise from

Answer 3

a single metarteriole

Question 4

What is a throughfare channel

Answer 4

Bypasses capillary bed

Question 5

Name some of the local mediators released by the capillary endothelium

Answer 5

Prostacyclin
Nitric Oxide
Endothelin

Question 6

What are the functions of the local mediators Prostacyclin, Nitric Oxide and Endothelin

Answer 6

Prostacyclin + Nitric Oxide = relaxation of vascular smooth muscle
Endothelin = contraction of vascular smooth muscle

Question 7

What is the active and passive functions of the capillaries

Answer 7

Active = release of the local mediators
Passive = exchange of all that poop

Question 8

Where can you find continuous capillaries

Answer 8

Skin
Lung
Fat
Muscle
Heart
Brain

Question 9

Describe the structure and function of continuous capillaries

Answer 9

The endothelial cell and basal lamina do not form openings, which would allow substances to pass the capillary wall without passing through both the endothelial cell and basal lamina e.g. BBB

Question 10

Where can you find fenestrated capillaries

Answer 10

Kidney and gut

Question 11

Describe the structure and function of fenestrated capillaries

Answer 11

The endothelial cell body forms small openings called fenestrations that allow components of the blood and interstitial fluid to bypass the endothelial cells on their way to or from the tissue surrounding the capillary

Question 12

Describe the structure and function of discontinuous (sinusoidal) capillaries

Answer 12

Formed by fenestrated endothelial cells, the basal lamina is also incomplete. These capillaries form large irregularly shaped vessels (sinusoidal vessels). Found where free excahnge of substances of even cells between the bloodstream and organ is advantageous

Question 13

Where are discontinuous capillaries found

Answer 13

Liver
Spleen
Red bone marrow

Question 14

How does movement between blood and interstitial fluid happen

Answer 14

Diffusion
Transcytosis
Bulk Flow

Question 15

What is the most important method of transport in capillaries

Answer 15

Diffusion

Question 16

What can substances cross the capillary wall through

Answer 16

Intracellular clefts
Fenestrations
Endothelial cells

Question 17

What limits diffusion in the BBB

Answer 17

Tight junctions

Question 18

Where can proteins and even blood cells leave the capillaries/organs/tissues

Answer 18

Sinusoids

Question 19

What is transcytosis

Answer 19

When a small quantity of material in the blood plasma becomes enclosed within pinocytotic vesicles and enters endothelial cells by endocytosis and leaves by exocytosis

Question 20

When is transcytosis important

Answer 20

Important mainly for large, lipid soluble molecules that cannot cross capillary walls any other way.

Question 21

What is bulk flow

Answer 21

It is a passive process in which large numbers of ions, molecules or particles in a fluid move together in the same direction and is based on pressure gradients.

Question 22

What is bulk flow most important for

Answer 22

For the regulation of relative volumes of blood and interstitial fluid

Question 23

What is an oedema and how does it happen

Answer 23

This is an excessive accumulation of ECF resulting from

• high blood pressure
• venous obstruction e.g. heart failure
• leakage of plasma proteins into ECF

Question 24

What is myxoedema

Answer 24

This is an excess production of glycoproteins in the extracellular matrix form hypothyroidism

Question 25

How can myxoedema occur

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Answer 25

• Hypothyroidism,
• Low plasma protein levels result from liver disease,
• Obstruction of lymphatic drainage
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