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Year 2 Sem 1 life Sciences > Physiology of kidney and urinary tract > Flashcards

Physiology of kidney and urinary tract Flashcards

1
Q

List the 4 parts of the urinary system, and describe the purpose of the ureter

A
  • Consists of two kidneys
  • Two ureters: These narrow tubescarry urine from the kidneys to the bladder. They continually tighten and relax, forcing urine downward from the kidneys to the bladder in small amounts
  • Bladder
  • A single urethra
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2
Q

What are the functions of the kidneys?

A
  • Primary function is to excrete waste products and toxins
  • Regulate blood pressure
  • Balances water levels
  • Vitamin D activators
  • Red blood cell production
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3
Q

What are clinical manifestations of kidney issues in relation to its location?

A

Location of kidneys
• Located in the retroperitoneal space: lower back area

Related clinical manifestations
• Lower back pain
• Changes in amount, quality and presentation of urine
• High blood pressure, puffiness in legs, ankles and around eyes
• Tiredness

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4
Q

List the basic parts of the nephron

A
  • Glomerulus: Bowmans capsule, Bowmans’ space
  • Proximal tubule
  • Loop of Henle
  • Distal tube
  • Collecting duct
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5
Q

Describe the function of the glomerulus

A
  • It is the ‘filtration’ apparatus
  • Since blood flow from the artery is at a high pressure, therefore, solutes are diffused out into the glomerulus
  • Only fluid and solutes are filtered out of the blood
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6
Q

Describe the function of the bowman’s capsule

A
  • It is composed of visceral ( inner) and parietal ( outer) layers
  • The inner layer only allows fluid and small molecules like glucose andions like sodium to pass through into the nephron
  • Red blood cells and large proteins, such as serum albumins, cannot pass through the glomerulus under normal circumstances
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7
Q

Describe the function of the proximal tubule

A
  • Site where the majority of water and salt reabsorption takes place
  • Active transport via the Na/K pump is essential for sodium reabsorption
  • Water is reabsorbed by osmosis as well as through the pump
  • Water and glucose follow sodium via an osmotic gradient in a process called co-transport
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8
Q

Describe the function of the Loop of Henle

A
  • Descending limb: highly permeable to water but completely impermeable to ions. Thus, a lot of water is reabsorbed
  • Ascending limb: impermeable to water but highly permeable to ions. Thin segment, there is passive transport NaCl whereas in the thick segment there is active transport
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9
Q

Describe the function of the distal tubule

A
  • Its permeability to water is variable depending on a hormone stimulus
  • Normally, it is impermeable to water and permeable to ions
  • The release of the anti- diuretic hormone acts on the distal tubule to increase the tubule’s permeability to water
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10
Q

Describe the function of the collecting tubule

A

• The collecting duct is similar in function to the distal convoluted tubule and generally responds the same way to the ADH hormone stimuli

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11
Q

List the three stages of urine formation

A

Filtration

Reabsorption

Secretion

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12
Q

Explain the three stages of urine formation

A

Filtration
• Occurs at the glomerulus
• Thefiltration membrane allows water and small solutes to pass but blocks blood cells and large proteins.

Reabsorption
• The glomerulus filters water and small solutes out of the bloodstream. While this contains waste, there are some essential ions within such as glucose, amino acids, and smaller proteins
• As the filtrate moves through the proximal tubule, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries
• Proximal tubule: reabsorbs H20 and NaCl
• Active transport via the Na/K pump is essential for sodium reabsorption

Secretion
• As nutrients and water are reabsorbed, simultaneously waste ions and hydrogen ions are secreted from the capillaries into the renal tubule
• The secreted ions combine with the remaining filtrate and become urine
• The urine flows out of the nephron tubule into a collecting duct

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13
Q

List the three types of diuretics

A

Osmotic diuretics

Loop diuretics

Thiazide diuretics

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14
Q

Explain osmotic diuretics

A
  • Promote water loss directly through osmosis
  • When these drugs are taken, they stay within the kidney’s filtrate in the tubules
  • This creates a high osmolality in the tubule
  • As a result, water is drawn into the tubule from the blood vessels via osmosis
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15
Q

Explain loop diuretics

A
  • Work by inhibiting the sodium-potassium-chloride co-transporter in the thick ascending loop of Henle
  • This reduces the amount of sodium, chloride and potassium reabsorbed
  • Therefore, this decreases the amount of water reabsorbed as well
  • Loop diuretics also reduce the reabsorption of calcium and magnesium
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16
Q

Explain thiazide diuretics

A
  • Inhibits the sodium/ chloride cotransporter in the distal tubule
  • Not as powerful as loop diuretics
  • Reduces calcium loss
17
Q

List the 5 systems involved in urine regulation

A
  • ADH
  • Baroreceptors
  • Macula Densa
  • Juxtaglomerular apparatus
  • Renin- angiotensin aldosterone system
18
Q

Explain the role of ADH in urine regulation, including what activates its release

A

• Antidiuretic hormone (ADH) is produced by the pituitary gland
• ADH is secreted when there is increased plasma osmolarity. This increased plasma osmolarity is sensed by osmoreceptors in the hypothalamus
• ADH increases the permeability of water in the distal tubules and collecting ducts so that more water is reabsorbed
ADH is a form of negative feedback. Once blood volume levels are regulated, the hypothalamus is inactivated and ADH secretion ends

19
Q

Explain the role of baroreceptors in urine regulation

A

• High blood pressure causes baroreceptors to fire more frequent action potentials. This leads to widespread vasodilation - the afferent arterioles supplying the glomerulus are also affected.
• Vasodilation = more blood volume = more urine lost
• Conversely, when blood pressure is low, there is decreased firing in the baroreceptors. This results in vaso-constriction
Vasoconstriction = less urine produced

20
Q

Explain the role of macula densa in urine regulation

A
  • Are a collection of specialized epithelial cells in the distal convoluted tubule that detect sodium concentration of the fluid in the tubule
  • When there are high sodium levels, the macula densa cells cause the afferent arteriole to contract
  • This reduces the flow of blood to the glomerulus and the glomerular filtration rate = less urine produced
21
Q

Explain the role of juxtaglomerular apparatus in urine regulation

A

• Consists of three types of cells; macula densa, juxtaglomerular cells and extraglomerular mesangial cells
• Juxtaglomerular cells synthesize, store, and secrete renin
They are specialized smooth musclecellsmainly in the walls of the afferent arterioles, and some in the efferent arterioles, that deliver blood to the glomerulus

22
Q

Explain the role of renin- angiotensin aldosterone system in urine regulation

A
  • When renal blood flow is reduced, juxtaglomerular cells in the kidneys convert prorenin into renin and secrets this into the blood
  • Renin converts angiotensin released by the liver into angiotensin I
  • The ACE enzyme, found in the lungs, converts angiotensin I into angiotensin II
  • Angiotensin II causes vasoconstriction and therefore increased blood pressure
  • Angiotensin II stimulates the release of the hormone aldosterone which causes the renal tubules to reabsorb sodium and water into the blood which increases blood pressure
23
Q

Explain the role of the kidney in red blood cell formation

A
  • Erythropoietin (EPO) is a hormone produced by the kidney
  • The kidneys cells that produce Erythropoietin are stimulated to do so when oxygen levels in the blood that travels through the kidney
  • Erythropoietin then stimulates the bone marrow to produce more red blood cells and initiate the synthesis of haemoglobin
24
Q

List three instances where renin is secreted

A
  • Chemoreceptors detect low sodium levels in the distal duct = renin secretion
  • When baroreceptors detect low pressure in the afferent arteriole = renin secretion
  • Sympathetic activation of the kidney = renin secretion

Year 2 Sem 1 life Sciences (33 decks)

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