Lecture 5: Capillaries and Lymphatics

Question 1

What are the three types of blood capillaries?

Answer 1

1. Continous
2. Fenestrated - leaky
3. Sinusoidal - very leaky

Question 2

What are the main features of sinusoidal capillaries?

Answer 2

• have large openings which penetrate both the endothelial layer & basement membrane
• found in liver & venous system
• 20-30um diameter
• VERY LEAKY

Question 3

What are the main features of fenestrated capillaries?

Answer 3

• have pores making them LEAKY, fenestration penetrate the endothelial layer but not the basal membrane
• 5-10um diameter
• found in Glomerulus, kidney

Question 4

What ar the main features of continuos capillaries?

Answer 4

• most common, widespread
• no interruption in the barrier
• found in skeletal & cardiac muscle
• 5-10um diameter

Question 5

What are precapillary sphincters?

Answer 5

• are composed of smooth muscle

- can control the flow of blood in the capillary bed

Question 6

What is the basement membrane?

Answer 6

A membrane that sits over the basal surface

• not penetrated by fenestrations in fenestrated capillaries
• is penetrated in sinusoidal capillaries

Question 7

What is the function of capillaries ?

What does this function demand?

Answer 7

• site of exchange btw blood and tissues

- very thin walls, large total CSA and slow &smooth blood flow

Question 8

What are the main features of lymphatic vessels?

Answer 8

• very thin walled in terms of vascular diameter
• no red blood cells
• has many valves

Question 9

What is the structure of lymphatic vessels?

Answer 9

• vessels commence as large, blind ending capillaries
• large, thin walled collecting vessel which have numerous valves which prevent back flow
• flap like mini valves allow fluid to drain

Question 10

What are laterals?

Answer 10

Are a special group of lymphatic vessels with blind endings found in the small intestine which drain fat-laden lymph not a collecting vessel called cisternae chill ‘milk jug’

Question 11

What are the functions of lymphatic vessels?

Answer 11

1. Drain excess tissue fluid & plasma proteins form tissues & return them to the blood
2. Filters foreign material from the lymph
3. Screen foreign material from lymph for foreign antigens and response by releasing antibodies
4. Absorbs fat from the intestine and transports it to the blood

Question 12

What is the lymph vascular system?

Answer 12

An open-entry (drainage), low pressure system