18 - Urinary System and Fluid Balance Flashcards Preview

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Flashcards in 18 - Urinary System and Fluid Balance Deck (80):
1

The urinary system consists of ..

- Two kidneys
- Two ureters
- The urinary bladder
- The urethra

2

What are the major functions of the urinary system?

1. Excretion
2. Regulation of blood volume and pressure.
3. Regulation of the concentration of solutes in the blood.
4. Regulation of extracellular fluid pH
5. Regulation of red blood cell synthesis
6. Regulation of vitamin D synthesis.

3

Explain this urinary system function: Excretion.

The kidneys are the major excretory organs of the body. They remove waste products fromt he blood. Many waste products are toxic, but most are metabolic by-products of cells, and substances absorbed from the intestine. The skin, liver, lungs, and intestines eliminate some of these waste products, but they cannot compensate if the kidneys fail to function.

4

Explain this urinary system function: Regulation of blood volume and pressure.

The kidneys play a major role in controlling the extracellular fluid volume in the body. They can produce either a large volume of dilute urine or a small volume of concentrated urine. Thereby, the kidneys regulate blood volume and blood pressure.

5

Explain this urinary system function: Regulation of the concentration of solutes in the blood

The kidneys help regulate the concentration of the major molecules and ions, such as glucose, Na+, Cl-, K+, Ca2+, HCO3-, and HPO4(2-)

6

Explain this urinary system function: Regulation of extracellular fluid pH.

The kidneys excrete variable amounts of H+ to help regulate extracellular fluid pH.

7

Explain this urinary system function: Regulation of red blood synthesis.

The kidneys secrete a hormone, erythropoietin, which regulates the synthesis of red blood cells in bone marrow.

8

Explain this urinary system function: Regulation of vitamin D synthesis.

The kidneys play an important role in controlling blood levels of Ca2+ by regulating the synthesis of vitamin D.

9

Each kidney is surrounded by ..

A renal capsule.

10

What is the hilum?

On the medial side of each kidney is the hilum, where the renal artery and nerves enter and where the renal vein, ureter, and lymphatic vessels exit the kidney. The hilum opens into a cavity called the renal sinus, which contains blood vessels, part of the system for collecting urine, and adipose tissue.

11

The kidney is divided into...

An out cortex and an inner medulla.

12

What is the name of the functional unit of the kidney?

The nephron.

13

The functional unit of the kidney is the nephron. Each nephron consists of ...

1. A renal corpuscle
2. A proximal convoluted tubule
3. A loop of Hele
4. A distal convoluted tubule.

14

Fluid is forced into the .....

Fluid is forced into the renal corpuscle,

15

Fluid is forced into the renal corpuscle and then flows into

Fluid is forced into the renal corpuscle and then flows into the proximal convoluted tubule.

16

Fluid is forced into the renal corpuscle and then flows into the proximal convoluted tubule. From there, it flows into

Fluid is forced into the renal corpuscle and then flows into the proximal convoluted tubule. From there, it flows into the loop of Henle.

17

Fluid is forced into the renal corpuscle and then flows into the proximal convoluted tubule. From there, it flows into the loop of Henle. Each loop of Henle consists of ...

Each loop of Henle consists of a descending limb and an ascending limb.

18

Each loop of Henle consists of a descending limb and an ascending limb. The limbs are further categorised into segments:

Each loop of Henle consists of a descending limb and an ascending limb. The limbs are further categorised into segments: the thin segment of the descending limb, the thin segment of the ascending limb, and the thick segment of the ascending limb.

19

The descending limb extends toward ...

The descending limb extends toward the renal sinus.

20

The descending limb extends toward the renal sinus, where it makes a hairpin turn, and the ascending limb extends back toward ...

the cortex.

21

The fluid flows through the ascending limb of the loop of Henle to the ...

The fluid flows through the ascending limb of the loop of Henle to the distal convoluted tubule.

22

The fluid flows through the ascending limb of the loop of Henle to the distal convoluted tubule. Several distal convoluted tubules empty into ...

The fluid flows through the ascending limb of the loop of Henle to the distal convoluted tubule. Several distal convoluted tubules empty into a collecting duct, which carries the fluid from the cortex, through the medulla.

23

The fluid flows through the ascending limb of the loop of Henle to the distal convoluted tubule. Several distal convoluted tubules empty into a collecting duct, which carries the fluid from the cortex, through the medulla. Many collecting ducts empty into a single ..

Many collecting ducts empty into a single papillary duct, and the papillary ducts empty their contents into a calyx.

24

The renal corpuscle of the nephron consists of ...

1. the Bowman capsule
2. The glomerulus

25

What is the Bowman capsule?

The Bowman capsule consists of the enlarged end of the nephron, which is indented to form a double-walled chamber.

26

What is the glomerulus?

The glomerulus is a tuft of capillaries that resembles a ball of yarn and lies within the indentation of the Bowman capsule.

27

The Bowman capsule opens into the x, which carries fluid away form the capsule.

Proximal convoluted tubule.

28

The inner layers of the Bowman capsule consist of specialised cells called ...

podocytes.

29

What is the filtration membrane?

The endothelium of the glomerular capillaries, the podocytes and the basement membrane together form a filtration membrane,

30

What is the first step of urine formation?

In the first step of urine formation, fluid consisting of water and solutes smaller than proteins, passes from the blood in the glomerular capillaries through the filtration membrane into the Bowman capsule.

31

In the first step of urine formation, fluid consisting of water and solutes smaller than proteins, passes from the blood in the glomerular capillaries through the filtration membrane into the Bowman capsule. What is the name of this fluid?

Filtrate.

32

The thin segment of the descending limb of the loop of Henle is permeable to ...

water and, to a lesser degree, solutes.

33

The thin segment of the ascending limb is permeable to ...

solutes, but not to water.

34

Scientists usually categorise urine formation into three major processes:

1. Filtration
2. Tubular reabsorption
3. Tubular secretion

35

When does filtration occur?

Filtration occurs when blood pressure unselectively forces water and other small molecules out of glomerular capillaries and into the Bowman capsule, forming a fluid called filtrate.

36

What is tubular reabsorption?

Tubular reabsorption is the movement of substances from the filtrate across the wall of the nephron back into the blood of the peritubular capillaries.

37

What is tubular secretion?

Tubular secretion is the active transport of solutes across the nephron walls into the filtrate.

38

How many liters of filtrate is produced each day?

About 180 L

39

How much of the 180L of filtrate becomes urine?

Just 1%. Most of the filtrate is absorbed.

40

Give two examples of materials that readily pass through the filtration membrane and into the Bowman capsule.

Water and solutes.

41

Give two examples of materials that can't pass through the filtration membrane and into the Bowman capsule.

Blood cells and most proteins.

42

If you were told there were some proteins in filtrate. Knowing nothing more than that, what could you induce?

They would probably be quite small in size.

43

What is filtration pressure?

Filtration pressure is the pressure gradient across the filtration membrane. It results from forces that move fluid out of the glomerular capillary into the Bowman capsule minus the forces that move fluid out of the Bowman capsule into the glomerular capillary.

44

What is the glomerular capillary pressure?

The glomerular capillary pressure is the blood pressure in the glomerular capillary. It is the major force causing fluid to move from the glomerular capillary across the filtration membrane into the Bowman capsule.

45

The glomerular capillary pressure is the blood pressure in the glomerular capillary. It is the major force causing fluid to move from the glomerular capillary across the filtration membrane into the Bowman capsule. There are two major forces causing fluid to move from the Bowman capsule across the filtration membrane into the glomerular capillary. Which?

1. Capsular pressure
2. Colloid osmotic pressure

46

What is capsular pressure?

Capsular pressure is caused by the pressure of filtrate already inside the Bowman capsule.

47

What is colloid osmotic pressure?

Colloid osmotic pressure is within the glomerular capillary. Because most plasma proteins do not pass through the filtration membrane, they produce an osmotic pressure that favours fluid movement into the glomerular capillary from the Bowman capsule.

48

An equation for the filtration pressure is...

Glomerular capillary pressure - Capsular pressure - Colloid osmotic pressure = Filtration pressure

49

What happens to urine volume if filtration pressure decreases?

It decreases.

50

What happens to urine volume if filtration pressure increases?

It increases.

51

An increase in blood protein concentration affects urine production how?

An increase in blood protein concentration encourages the movement of water by osmosis back into the glomerular capillaries (colloid osmotic pressure), and therefore reduces the overall filtration pressure.

52

What is the primary site for reabsorption of solutes and water?

The proximal convoluted tubule.

53

What happens in the proximal convoluted tubule?

The proximal convoluted tubule is adapted to transport molecules and ions across the nephron wall by active transport and cotransport. Water follows by osmosis.

54

What happens in the thin segment of the descending tubule (the part after the proximal convoluted tubule)?

The tubule is now inside the renal medulla which contains very concentrated interstitial fluid that has large amount of Na+, Cl-, and urea. This causes the water in the tubule to move out of the tubule by osmosis.

55

The ascending limb of the loop of Henle is permeable to what?

It's not permeable to water, but it is permeable to solutes.

56

What happens in the ascending limb of the loop of Henle?

Solutes diffuse out of the nephron.

57

The thick segment of the ascending limb is permeable to what?

It's not permeable to water. Ions are actively transported out.

58

What happens in the thick segment of the ascending limb?

The cuboidal epithelial cells of the thick segment of the ascending limb actively transport Na+ out of the nephron, and K+ and Cl- are cotransported with Na+. The thick segment of the ascending limb is not permeable to water.

59

What happens in the distal convoluted tubule and collecting duct?

Sodium ions are actively transported, and chloride ions are cotransported. Water follows by osmosis.

60

When the blood pressure increases above normal, the kidneys do what?

When the blood pressure increases above normal, the kidneys produce a large amount of urine. The loss of water in the urine lowers blood volume.

61

Three major hormonal mechanisms are involved in regulating urine concentration and volume. Which?

1. The renin-angiotensin-aldosterone mechanism
2. The antidiuretic hormone (ADH) mechanism
3. The atrial natriuretic hormone (ANH) mechanism.

62

Which of the three major hormonal mechanisms involved in regulating urine concentration and volume are sensitive to changes in blood pressure?

Renin-angiotensin-aldosterone mechanism and the ANH mechanism.

63

Which of the three major hormonal mechanisms involved in regulating urine concentration and volume are sensitive to changes in blood concentration?

the ADH mechanism.

64

The renin-angiotensin-aldosterone mechanism ends with the secretion of aldosterone by the adrenal cortex. What effect does this have on the kidneys?

Aldosterone increases the rate of active transport of Na+ in the distal convoluted tubules and collecting ducts. When the blood pressure suddenly decreases, or when the concentration of Na+ in the filtrate becomes too low, the kidney releases renin. The resultant increase in aldosterone causes an increase in Na+ and Cl- reabsorption from the nephrons. Water follows the Na´and Cl-. Thus the volume of water lost in the form of urine declines. This method of conserving water helps prevent a further decline in blood pressure.

65

Antidiuretic hormone (ADH) is secreted by...

The pituitary gland.

66

What causes ADH to be secreted by the pituitary gland?

Certain cells of the hypothalamus are sensitive to changes in solute concentration. When the solute concentration in the blood increases, action potentials are sent along the axons of the ADH-secreting neurons of the hypothalamus to the posterior pituitary, and ADH is released form the ends of the axons.

67

What effect does the release of ADH have on the kidneys?

ADH regulates the amount of water reabsorbed by the distal convoluted tubules and collecting ducts. When levels of ADH increase, the permeability of the distal convoluted tubules and collecting ducts to water increases, and more water is reabsorbed from the filtrate.

68

Atrial natriuretic hormone is secreted by ...

Atrial natriuretic hormone (ANH) is secreted from cardiac muscle cells in the right atrium of the heart.

69

Atrial natriuretic hormone (ANH) is secreted from cardiac muscle cells in the right atrium of the heart. When?

When blood pressure in the right atrium increases above normal.

70

What effect does ANH have on the kidneys?

ANH acts on the kidneys to decrease Na+ reabsorption. Therefore, Na+ and water remain in the nephron to become urine. The increased loss of Na+ and water as urine reduces the blood volume and the blood pressure.

71

What causes acidosis/alkalosis?

Failure of the buffer systems, the respiratory system, or the urinary system to maintain normal pH levels can result in acidosis or alkalosis.

72

What is acidosis?

Acidosis occurs when the blood pH falls below 7.35.

73

What is alkalosis?

Alkalosis occurs when the blood pH increase above 7.45

74

What is respiratory acidosis?

Results when the respiratory system is unable to eliminate adequate amount of CO2. This causes the pH in the body fluid to decline.

75

What is metabolic acidosis?

Results from excess production of acidic substances, such as lactic acid and ketone bodies. This can be caused by increased metabolism or deceased ability of the kidneys to eliminate H+ in the urine.

76

What is respiratory alkalosis?

Results from hyperventilation.

77

What is metalbolic alkalosis?

Results from the rapid elimination of H+ from the body, as occurs during severe vomiting or when excess aldosterone is secreted by the adrenal cortex.

78

How can the body control the concentration of Na+ in bodily fluids?

Stimuli that control aldosterone secretion influence the reabsorption of Na+ from nephrons of the kidneys and the total amount of Na+ in the body fluids. Aldosterone increases reabsorption.

79

How can the body control the concentration of K+ in bodily fluids?

Aldosterone plays a major role in regulating the concentration of K+ in the extracellular fluid. Aldosterone secretion from the adrenal cortex causes K+ secretion to increase. Remember that K+ is actively secreted into the tubules.

80

How can the body control the concentration of Ca+ in bodily fluids?

Parathyroid hormone increases extracellular Ca2+ concentrations by causing osteoclasts to degrade bone and release Ca2+. PTH release is regulated by Ca2+ concentrations.

Vitamin D increases Ca2+ concentration in the body by increasing the rate of Ca2+ absorption by the intestine. PTH also increase the rate of vitamin D production in the body.

Calcitonin reduces the blood Ca2+ concentration by reducing the rate at which bone is broken down.