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A&P Fall 24' > A^0P 8 Nov '24 Lecture 28 > Flashcards

A^0P 8 Nov '24 Lecture 28 Flashcards

1
Q

What processes describe fluid movement in capillaries?

A

Filtration for fluid leaving the capillary and reabsorption for fluid being absorbed by the capillary.

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2
Q

What governs the filtration rate in the kidneys?

A

The filtration rate is governed by pressures and vascular resistance.

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3
Q

What happens to blood pressure as it moves through areas of high vascular resistance?

A

Blood pressure is reduced as blood flows through areas of high vascular resistance.

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4
Q

What is the primary site for nutrient exchange in circulation?

A

Capillaries are the primary site for nutrient exchange and waste product collection.

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5
Q

What role do arterioles play in blood flow?

A

Arterioles control blood flow to downstream tissues through contraction and relaxation of smooth muscle.

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6
Q

How much surface area do capillaries provide in the body?

A

500 to 700 square meters of surface area for nutrient exchange.

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7
Q

What is the internal diameter of arterioles? Total cross-sectional area?

A

The internal diameter of arterioles is approximately 30 micrometers. Total cross-sectional is 400cm-squared

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8
Q

What is the internal diameter of the aorta? Total cross-sectional area?

A

The internal diameter of the aorta is 2.5cm. Total cross-sectional area is 4.5cm-squared

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9
Q

What is the internal diameter of capillaries? Total cross-sectional area?

A

The internal diameter of the capillaries is 5 micrometers. Total cross-sectional area is 4500cm-squared

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10
Q

What is the internal diameter of the vena cavae? Total cross-sectional area?

A

The internal diameter of the vena cavae is 3 cm. Total cross-sectional area is 18cm-squared. Specifically remember that there are 2 vena cava, each with 3cm internal diameter and each with a wall thickness of 1.5mm. Putting these together give a TOTAL of 18cm-squared cross-sectional area, so 1 would only be 9cm-squared.

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11
Q

What is unique about capillary walls?

A

Capillary walls are only one cell layer thick, composed of endothelial cells.

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12
Q

What is the relationship between blood flow and resistance according to Ohm’s law?

A

As resistance goes up, blood flow goes down; as pressure difference (delta p) goes up, blood flow goes up.

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13
Q

How do the vena cava compare to the aorta in terms of diameter?

A

The internal diameter of the vena cava is about 3 cm, which is larger than that of the aorta (2.5cm). We must also account for the fact that there are 2 vena cava vs. 1 aorta.

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14
Q

What is the velocity of blood flow through the aorta compared to capillaries?

A

The velocity of blood flow through the aorta is the fastest, while it is slower through capillaries due to their larger total cross-sectional area.

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15
Q

What is the primary function of smooth muscle in arterioles?

A

Smooth muscle in arterioles allows for regulation of systemic vascular resistance and blood flow.

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16
Q

What happens to blood flow when arterioles constrict?

A

Constriction of arterioles typically drives up blood pressure (upstream).

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17
Q

What is the significance of the thin walls of capillaries?

A

Thin walls of capillaries facilitate efficient nutrient and waste exchange.

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18
Q

What is the blood pressure at the arterial end of a generic capillary? (PCAP)

A

About 30 mmHg.

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19
Q

What is the blood pressure at the end of a capillary?

A

10 mmHg.

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20
Q

What is Delta P in the context of capillary dynamics?

A

The pressure difference that allows blood to move from the beginning to the end of the capillary, which is about 20 mmHg. (Actual measurement is 17.3 mmHg)

  • In many capillaries, the venous end becomes larger and larger.
  • If there is a larger vessel, vascular resistance is decreased so the delta P is lower so our average is lower
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21
Q

What is the normal mean arterial pressure (MAP) for the class?

A

100 mmHg.

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22
Q

What is the typical Delta P at a capillary?

A

About 20 mmHg. (17.3 mmHG to be exact)

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23
Q

What forces favor fluid movement at the venous end of the capillary?

A

Forces that favor reabsorption.

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24
Q

What is filtration in the context of capillaries?

A

Fluid moving out of the capillary.

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25
Q

What is reabsorption in the context of capillaries?

A

Fluid moving back into the capillary.

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26
Q

What is the plasma colloid osmotic pressure in healthy individuals? (πcap or πP)

A

28 mmHg.

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27
Q

What is the interstitial fluid colloid osmotic pressure? (πISF or πIF)

A

8 mmHg.

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28
Q

What happens to fluid movement if interstitial fluid pressure is positive?

A

It may reduce filtration or promote reabsorption.

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29
Q

What is the normal interstitial fluid pressure? (PISF or PIF)

A

-3 mmHg.

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30
Q

What is the role of lymphatics in interstitial fluid pressure?

A

They help pull excess fluid out of the interstitium, contributing to negative pressure. Damaging these long term can cause unmanageable limb edema.

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31
Q

What is the average net filtration pressure? (NFP)

A

0.3 in the capillaries. This seems low at first but remember, we have so many capillaries that the math checks out.

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32
Q

What is the equation for net filtration pressure? (NFP)

A

NFP=Pcap-Pisf-πcap+πisf

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33
Q

What does Kf represent? (Regarding filtration)

A

Kf is the filtration coefficient. This is a constant of proportionality that represents the net fluid flux across a capillary wall.

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34
Q

What is the equation for filtration?

A

Filtration=Kf*NFP

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35
Q

What happens to plasma colloid osmotic pressure (oncotic pressure) during hemorrhage?

A

It becomes difficult to keep fluid within the cardiovascular system. Proteins leak out because the vascular cell walls has become “Swiss cheese”. Even after the wall is repaired, plasma proteins become stuck on the wrong side and continue to pull additional fluid into interstitial spaces, causing edema.

36
Q

Can the lymphatic system handle extra proteins that have leaked into interstitial spaces?

A

Kind of, but not very well. The lymphatic system can increase its efficiency 20-40X when needed, but this is mainly for water and smaller particles, like ions. It can move proteins but it is VERY slow and even slower if the patient is not ambulatory.

37
Q

What is the significance of capillary permeability to water and small particles?

A

Capillaries are very thin-walled and allow easy movement of water and small particles.

38
Q

What is the effect of capillary wall permeability to proteins?

A

It reduces osmotic pressure associated with those proteins.

39
Q

What are the four main factors of Capillary Starling Forces?

A

Blood pressure in the capillary (Pcap), interstitial fluid pressure (Pisf), plasma colloid osmotic pressure (πcap), and interstitial fluid colloid osmotic pressure (πisf).

40
Q

What happens when cells are damaged in a disorganized way?

A

When cells implode and die, their contents scatter into the interstitial fluid. While we mainly focus on the ions like potassium, remember that the cells contain TONS of proteins too and when these leak out, fluid shifts become more common (not good).

41
Q

What causes swelling in damaged tissue?

A

Swelling occurs because proteins that were inside the cells create osmotic pressure in the environment.

42
Q

What are some causes of tissue swelling (edema)?

A

Crush injuries, bacterial infections, and viral infections can lead to cell death and swelling.

43
Q

Why is it difficult to reduce swelling after tissue damage?

A

Swelling is difficult to resolve because proteins leak into the interstitial fluid and remain there after the capillary walls heal.

44
Q

How do lymphatics help with excess proteins in the interstitial fluid?

A

Lymphatics can pick up some excess proteins, but this process is slow, especially in immobile patients.

45
Q

What happens to lymphatic function when a person is bed-bound?

A

Lymphatic function is reduced, leading to prolonged swelling and edema.

46
Q

What factors influence lymphatic flow?

A

Lymphatic flow increases with physical activity and muscle contractions, but is limited in immobile individuals.

47
Q

What is the capillary filtration coefficient (Kf)?

A

It is a measure of how permeable the capillaries are, primarily for fluid rather than proteins.

48
Q

What are the three main proteins that contribute to plasma oncotic pressure?

A

Albumin (Primary), globulins (Secondary), and fibrinogen (Tertiary) are the primary components of plasma oncotic pressure.

49
Q

What are the πp values of the proteins that contribute to oncotic pressure? (Donnan Effects)

A

Albumin (21.8mmHg), Globulins (6.0mmHg), Fibrinogen (0.2mmHg) Totaling 28mmHg of oncotic pressure in a standard, healthy patient.

50
Q

What is the net filtration pressure at the arteriolar end of the capillary?

A

The net filtration pressure at the arteriolar end is approximately 13 mmHg. This favors filtration. Pressures that favor filtration (removal of fluid from the capillary): Arterial end of capillary Pcap=30mmHg, Pisf=3mmHg, Proteins within the interstitium (normally)=8mmHg so total 41mmHg. Normal oncotic pressure opposes filtration with 28mmHg so the net total filtration is 13mmHg.

51
Q

What is the net filtration pressure at the venous end of the capillary?

A

The net filtration pressure at the venous end is approximately -7 mmHg. This favors reabsorption. Pressures that favor reabsorption (deposition of fluid into the capillary): Venous end of capillary Pcap=10mmHg, Pisf=3mmHg, Proteins within the interstitium (normally)=8mmHg so total 21mmHg. Normal oncotic pressure opposes filtration normally which also means that it FAVORs reabsorption with 28mmHg. This gives a NFP of -7mmHg which is the same as saying NRP of 7mmHg.

52
Q

What is plasma oncotic pressure?

A

Plasma oncotic pressure is a force that does not change significantly in this context.

53
Q

What is the net filtration pressure when pressures favoring filtration (πisf, Pcap, and interstitial protein pressures)= 21 mmHg and oncotic pressure is 28 mmHg?

A

The net filtration pressure is negative seven mmHg (21 - 28 mmHg). This favors reabsorption into the capillary.

54
Q

What does a net filtration pressure of negative seven indicate?

A

It indicates that reabsorption is likely occurring at the venular end of the capillary.

55
Q

What happens at the arterial end of the capillary?

A

At the arterial end, the net filtration pressure is 13 mmHg, favoring fluid movement out of the capillary.

56
Q

What occurs at the venular end of the capillary?

A

Fluid is expected to move back into the capillary at the venular end because NFP is -7mmHg.

57
Q

What is the general expectation regarding filtration and reabsorption in capillaries?

A

There should be lots of filtration at the beginning and lots of reabsorption at the end of the capillary.

58
Q

What happens if filtration exceeds reabsorption?

A

Excess fluid that is not reabsorbed will need to be scavenged by the lymphatics.

59
Q

What role do lymphatics play in fluid balance?

A

Lymphatics help to scavenge excess fluid filtered out of capillaries, preventing edema.

60
Q

What is the average capillary blood pressure in systemic circulation?

A

The average capillary blood pressure is 17.3 mmHg.

61
Q

How is the average capillary blood pressure determined?

A

It is determined by the larger diameter of capillaries towards the venous end, leading to a lower average pressure.

62
Q

What is the net filtration pressure throughout the entire capillary?

A

The net filtration pressure on average is 0.3 mmHg.

63
Q

What are capillaries generally permeable to?

A

Capillaries are generally permeable to water, sodium, and chloride.

64
Q

List the permeability percentages of substances in capillaries.

A
65
Q

What is the exception to sodium and chloride permeability?

A

The blood-brain barrier is less permeable to sodium and chloride due to tightly packed endothelial cells.

66
Q

How does the size of a molecule affect its permeability through capillaries?

A

Larger molecules, like albumin, have lower permeability compared to smaller molecules like sodium.

67
Q

What is the permeability of glucose in capillaries?

A

Glucose is less permeable than sodium and chloride and often requires transporters in the blood-brain barrier. Permeability=0.6

68
Q

What is the general summary of capillary permeability?

A

Capillaries are more permeable to smaller molecules, while larger molecules have reduced permeability.

69
Q

What is the blood pressure in the renal artery?

A

The average blood pressure in the renal artery is about 100 mmHg.

70
Q

What happens to blood pressure as it moves through the kidney?

A

Blood pressure decreases due to resistance encountered in the renal blood vessels.

71
Q

What is the blood pressure in the glomerular capillaries?

A

The blood pressure at the start of the glomerular capillaries is about 60 mmHg.

72
Q

What is the significance of the high blood pressure in the glomerular capillaries?

A

The high blood pressure allows for significant filtration of fluid into the processing compartment.

73
Q

What is the glomerular filtration rate (GFR)?

A

The glomerular filtration rate is the rate of fluid moving from the glomerular capillaries into a compartment for processing.

74
Q

What happens to glucose that gets filtered in the kidneys?

A

Filtered glucose is typically reabsorbed to prevent loss from the body. In a healthy adult, with a normal glucose, ALL of the glucose is reabsorbed.

75
Q

What is the role of the afferent arteriole in the kidney?

A

The afferent arteriole has high resistance, affecting blood pressure in the glomerular capillaries. The afferent arteriole can either constrict to decrease glomerular flow or relax to increase flow.

76
Q

What is the average blood pressure in the glomerular capillaries compared to typical systemic capillaries?

A

The average blood pressure in the glomerular capillaries is 60 mmHg, which is twice that of typical systemic capillaries.

77
Q

What is the significance of high blood pressure in glomerular capillaries?

A

High blood pressure allows for significant filtration at the first capillary bed. The kidney is just a big ball of blood vessels and needs high blood pressure to be an efficient filter (like with plumbing)

78
Q

What is the total filtration rate of all glomerular capillaries combined?

A

The total filtration rate is about 125 mls per minute.

79
Q

What types of substances are easily filtered through glomerular capillaries?

A

Small substances are easily filtered (ions, sometime glucose, medications, water, etc).

80
Q

What substances are not normally filtered by glomerular capillaries?

A

Larger substances, such as red blood cells and large proteins, are not normally filtered.

81
Q

Under what conditions might large proteins or red blood cells be filtered?

A

They may be filtered if there is something wrong, such as damage to the capillaries.

82
Q

What should be the condition of glomerular capillaries for proper filtration?

A

Glomerular capillaries should be intact and healthy, without exposure to diabetes or hypertension.

83
Q

What drives the filtration process in glomerular capillaries?

A

The high blood pressure drives the filtration process.

84
Q

What are the openings in the glomerular endothelial cells (GEnCs) of the kidney CALLED that allow blood to be filtered?

A

Fenestrations

85
Q

What is the standard filtration coefficient of a glomerular capillary? (Kf)

A

12.5, if we multiply this by our NFP (standard is 10), we get 125 ml/min which is the standard for GFR

A&P Fall 24' (12 decks)

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