Capillaries and Lymphatics

Question 1

Describe the function and traits of capillaries

Answer 1

Function: site of gas exchange between blood and tissues

• Very thin walls
• Large total CSA of capillary bed
• Slow and smooth blood flow
• Endothelial cells form junctions with themselves, forming a closed tube

Large total area of the capillary bed (compared to arterioles) means much slower blood flow (river to lake analogy)

Question 2

Describe the flow of blood from a terminal arteriole to a postcapillary venule

Answer 2

• Terminal arteriole
• Precapillary sphyncters (composed of smooth muscle cells that contracts to control which capillaries blood can go into)
• Vascular shunt
  - metarteriole
  - thoroughfare channel
• Postcapillary venule

Question 3

The structure f capillaries varies according to the rate of exchange needed, and how controlled the exchange must be. List the three types of capillaries

Answer 3

• Continuous (the most common/widespread)
• Fenestrated (leaky)
• Sinusoidal (very leaky)

Question 4

Describe the structure of a continuous capillary

Answer 4

• 8-10 micrometers in diameter
• Continuous basement membrane (also called basal lamina)
• Continuous endothelial layer with intercellular clefts

Example: skeletal and cardiac muscle

Question 5

Describe the structure of a fenestrated capillary

Answer 5

• 8-10 micrometers in diameter
• fenestrations in the endothelial layer (small holes so some solutes can pass through)
• continuous basement membrane (basal lamina)

Example: in the small intestine

Question 6

Describe the structure of a sinusoidal capillary

Answer 6

• 30-40 micrometers in diameter
• incomplete basement membrane (basal lamina)
• large gaps in the endothelium

Example: liver sinusoids

Question 7

What ways can continuous capillaries transport materials?

Answer 7

1. Diffusion through membrane (lipid soluble substances)
2. Movement through intercellular clefts (water-soluble substances)
3. Tranport via vesicles or caveolae (large substances)

Question 8

what ways can fenestrated capillaries transport materials?

Answer 8

1. Diffusion though membrane (lipid soluble substances)
2. Movement though intercellular clefts (water-soluble substances)
3. Movement through fenestrations and then basement membrane (water-soluble substances)
4. Transport via vesicles or caveolae (large substances)

Question 9

What ways can sinusoidal capillaries transport materials?

Answer 9

1. Diffusion though membrane (lipid soluble substances)
2. Movement though intercellular clefts (water-soluble substances)
3. Movement through fenestrations (water-soluble substances) no basement membrane
4. Transport via vesicles or caveolae (large substances)

Question 10

Describe the functions of the lymph vascular system

Answer 10

An open-entry (drainage) system

Functions:
- Drains excess tissue fluid and plasma proteins from tissues and returns them to blood
- Filters foreign material from lymph
- ‘screens’ lymph for foreign antigens and responds by releasing antibodies and activated immune cells
- absorbs fat from intestine and transports to blood

Question 11

Describe the structure of the lymphatic system

Answer 11

Lymphatic vessels:
- Commence as large, blind ending capillaries
- From small intestine, a special group of lymphatic vessels called lacteals drain fat-laden lymph into a collecting vessel called the cisterna chyli
- Larger (thin wall) collecting vessels have numerous valves to prevent backflow
- Fluid can get into the lymphatic vessels easily as the endothelial cells are spaced a bit apart

To identify:
- Thin walled
- No red blood cells
- Valves present

Question 12

Name the major components of the lymph vascular system

Answer 12

Regional lymph nodes:
- Cervical nodes (neck)
- Axillary nodes (armpit)
- Inguinal nodes (groin)

Entry of lymph back into veins:
- Entrance of right lymphatic duct into right subclavian vein - then vena cava
- Entrance of thoracic duct into left subclavian vein - then vena cava
- Thoracic duct (collects all the lymph on the left side of body)
- Cysterna chyli (fat laden lymph collects here)
- Lymphatic collecting vessels

Question 13

Describe lymph node structure

Answer 13

Afferent lymph nodes
- this is where lymph comes into the lymph node
Lymph is then checked by immune cells for antigens
Efferent lymph nodes
- this is where the lymph leaves the lymph node

Question 14

Describe the path of lymphatic drainage of the breast

Answer 14

• Lymphatic vessels of the breast
• Axillary lymph nodes
• Right subclavian vein
• Right lymphatic duct

Breast tissue lymphatic drainage can carry cancer cells into the blood vascular system… Results in metastatic cancer