The Peripheral Circulation 1

Question 1

the structure of capillaries.

Answer 1

Capillaries are thin-walled vessels with a single layer of endothelial cells, providing a small barrier to diffusion.

Question 2

What is the function of capillaries in the body?

Answer 2

Capillaries serve as exchange vessels, facilitating the diffusion of oxygen, carbon dioxide, and other substances between blood and tissues.

Question 3

How do capillaries contribute to efficient exchange processes?

Answer 3

Capillaries have a large number, small diameter, and high surface area to volume ratio, allowing for close proximity to tissues and effective diffusion.

Question 4

Define tight junctions in capillaries.

Answer 4

Tight junctions are areas where endothelial cells are closely pressed together, preventing the passage of substances.

Question 5

What is transcytosis in capillaries?

Answer 5

Transcytosis is the process by which macromolecules, including proteins, are transported across individual endothelial cells via vesicles and pores.

Question 6

Describe the different classes of capillaries.

Answer 6

Capillaries can be continuous, fenestrated, or discontinuous, each with varying levels of permeability and presence of clefts and pores.

Question 7

Describe the structure of continuous capillaries.

Answer 7

Continuous capillaries have cs but no pores, them the most common type found in muscle.

Question 8

Define fenestrated capillaries and where they are found in the body.

Answer 8

Fenestr capillaries have both clefts and pores, specialized for fluid exchange, and are found in the intestine and.

Question 9

How are discontinuous capillaries different from other types, and where are they typically found?

Answer 9

Discontinuous capillaries have clefts and massive pores, allowing large proteins to move across. They are found in the liver.

Question 10

Do capillaries primarily function in exchange, and how does this process occur?

Answer 10

Yes, capillaries primarily function in exchange, with most of it happening via diffusion. Oxygen moves from capillaries into extracellular fluid and then into cells.

Question 11

Describe why diffusion is well-suited for exchange in capillaries.

Answer 11

Diffusion is self-regulating, responding to changes in oxygen demand, and non-saturable, allowing continuous movement of substances without reaching a transport protein limit.

Question 12

Explain the role of non-polar and polar substances in capillary exchange.

Answer 12

Non-polar substances like oxygen and carbon dioxide can freely diffuse across the membrane, while polar substances like water pass through clefts and pores.

Question 13

Describe the role of the glucose transporter in the brain.

Answer 13

The glucose transporter in the brain helps transport glucose across the blood-brain barrier to provide the brain with necessary energy.

Question 14

Define bulk flow in the context of exchange processes.

Answer 14

Bulk flow is a mechanism of exchange determined by Starling’s forces, involving the movement of water and small solutes through clefts and pores in endothelial cells.

Question 15

How is net filtration pressure calculated in capillary beds?

Answer 15

Net filtration pressure is calculated as the difference between hydrostatic pressure and osmotic (oncotic) pressure in the capillary bed.

Question 16

Describe the balance between hydrostatic and osmotic pressure in capillaries.

Answer 16

Hydrostatic pressure pushes fluid out of the capillary, while osmotic (oncotic) pressure pulls fluid back in, maintaining a balance in the exchange of fluids.

Question 17

Do hydrostatic pressure and osmotic pressure vary in different capillary beds?

Answer 17

Yes, the balance between hydrostatic and osmotic pressure can vary in different capillary beds, affecting the exchange of fluids.

Question 18

Define net filtration pressure in the context of fluid exchange.

Answer 18

Net filtration pressure is the overall pressure gradient that drives the movement of fluid across capillary walls, calculated as the difference between hydrostatic and osmotic pressures.

Question 19

Describe the structure of lymphatic capillaries compared to blood capillaries.

Answer 19

Lymphatic capillaries are blind-ended and very similar in structure to blood capillaries.

Question 20

How does fluid move through the lymphatic system back towards the heart?

Answer 20

Fluid drains from lymphatic capillaries into lymph nodes, then into larger lymphatic vessels. Smooth muscle contractions in vessel walls and external compression from skeletal muscles help push the fluid back towards the heart.

Question 21

Define oedema and mention two possible causes of it.

Answer 21

Oedema is the accumulation of fluid in tissues. Possible causes include raised central venous pressure (e.g., left ventricular failure) and lymphatic obstruction (e.g., due to parasitic infection).

Question 22

Describe the role of lymph nodes in the immune system.

Answer 22

Lymph nodes are part of the immune system and help filter lymph fluid, removing pathogens and other harmful substances before the fluid is returned to the cardiovascular system.

Question 23

How is oedema visible in a chest x-ray, and what does it indicate?

Answer 23

In a chest x-ray, oedema appears as increased whiteness and fluffiness in the lungs, indicating an accumulation of fluid in the lung tissues, known as pulmonary oedema.

Question 24

What are the mechanisms that help propel lymph fluid back towards the heart in the lymphatic system?

Answer 24

Smooth muscle contractions in lymphatic vessel walls, external compression from skeletal muscles, and absence of a central pump help propel lymph fluid back towards the heart.

Question 25

Describe a scenario where oedema can be caused by lymph obstruction.

Answer 25

surgery damages some lymph nodes, it can lead to lymphatic obstruction and unilateral oedema in a specific body part like the leg.

Question 26

Define hypoproteinaemia and its relation to oedema.

Answer 26

Hypoproteinaemia is a condition characterized by low protein levels in the blood. It can cause oedema, such as ascites in the abdomen, due to insufficient oncotic pressure to retain fluid in the capillaries.

Question 27

How does severe malnutrition contribute to oedema in children?

Answer 27

Severe malnutrition can lead to oedema in children by causing a lack of protein intake, resulting in decreased osmotic pressure in the capillaries and increased fluid loss into the lymphatic system.

Question 28

Describe the causes of hyperproteinaemia in the context of oedema.

Answer 28

Hyperproteinaemia can result from conditions like nephrotic syndrome (kidney damage causing protein leakage in urine) or liver failure (impairing protein synthesis), leading to oedema.

Question 29

Explain how increased capillary permeability can lead to oedema in rheumatoid arthritis.

Answer 29

In rheumatoid arthritis, autoimmune attacks on joints can increase capillary permeability, causing fluid and protein loss. This reduces osmotic pressure, leading to oedema, notably in small joints like hands and feet.

Question 30

Describe the process of fluid exchange in capillaries and its relation to oedema.

Answer 30

Fluid exchange in capillaries involves diffusion and bulk flow, with excess fluid usually draining into the lymphatic system for return to the cardiovascular system. If the lymphatic system is overwhelmed, oedema can occur due to fluid accumulation.