Lecture 7: Capillaries and lymphatics

Question 1

What is the function of capillaries?

Answer 1

Site of exchange between blood and tissues.

Question 2

What does the function of capillaries demand?

Answer 2

• Very thin walls.
• Large total cross sectional area of capillary bed.
• Slow & smooth blood flow. (river to a lake)

Question 3

Role of precapillary sphincters?

Answer 3

• To manage blood flow throughout a capillary bed.
• Can impact temperature regulation of blood.
• Composed of smooth muscle

Question 4

What are the three types of capillary?

Answer 4

1. Continuous capillaries (the most widespread).
2. Fenestrated capillaries (leaky).
3. Sinusoidal capillaries (very leaky)

Question 5

What is the structure of a continuous capillary and where can they be found?

Answer 5

• Endothelial layer is continuous
• Has a complete basement membrane
• 1 blood cell wide
• found in skeletal and cardiac muscle

Question 6

What is the structure of a Fenestrated capillary and where can they be found?

Answer 6

• endothelial layer is continuous but has little holes called fenestrations to allow better diffusion and passive exchange
• has a complete basement membrane
• 1 blood cell wide
• can be found in the kidneys

Question 7

What is the structure of a sinusoidal capillary and where can they be found?

Answer 7

• endothelial layer is very discontinuous with large gaps
• incomplete basement membrane
• direct interaction with cells outside the capillary
• 3-4 Blood cells wide
• can be found within the liver

Question 8

How do capillaries complete exchange with cells (4 ways)?

Answer 8

MCFV
1. diffusion through the membrane (lipid soluble substances)
2. movement through intercellular clefts (water soluble substances)
3. movement through fenestrations (water soluble substances)
4. transport via vesicles or caveolae (large substances)

• Continuous does 1,2 and 4
• Fenestrated and Sinusoidal do all four, with sinusoidal being more effective

Question 9

What is the Lymph Vascular System?

Answer 9

An open-entry (drainage) system.

Question 10

What is the function of the Lymph Vascular System?

Answer 10

1. Drains excess tissue fluid & plasma proteins from
   tissues and returns them to the blood.
2. Filters foreign material from the lymph.
3. ‘Screens’ lymph for foreign antigens & responds by
   releasing antibodies & activated immune cells.
4. Absorbs fat from intestine and transports to blood.

Question 11

Describe the Lymphatic systems structure:

Answer 11

1. Commence as large, blind ending capillaries.
2. From small intestine, a special group of lymphatic vessels called lacteals drain fat-laden lymph into a collecting vessel called the cisterna chyli.
3. Larger (thin wall) collecting vessels have numerous
   valves to prevent backflow.

Question 12

What structure deals with fat-laden lymph?

Answer 12

Lymphatic vessels called lacteals

Question 13

What structure drains a majority of lymph from the left side of the body?

Answer 13

A large collecting vessel called the cisterna chyli. (Kylie Jenner)

Question 14

What structure drains the upper right half of the body’s lymph?

Answer 14

The right lymphatic duct that enters the right subclavian vein.

Question 15

What are the nodes of the neck, armpits and groin called?

Answer 15

Neck = Cervical nodes
Armpits = Axillary nodes
Groin = Inguinal nodes