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Anatomy and Physiology 1 > 14. Urinary System > Flashcards

14. Urinary System Flashcards

1
Q

The urinary system consists of (4)

A
  1. 2 kidneys
  2. 2 ureters
  3. bladder
  4. urethra
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2
Q

What are the functions of the kidney (4)

A
  1. Excrete metabolic wastes
  2. Regulate body fluid volume, ionic concentration and pH
  3. Endocrine function
  4. Metabolic functions
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3
Q

Explain the endocrine function of the kidney (2)

A
  1. Renin and prostaglandins: regulate blood pressure and sodium balance
  2. Erythropoietin: regulate red blood cell production
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4
Q

Explain the metabolic function of the kidney (2)

A
  1. Site of activation of Vitamin D: Calcium and phosphorus metabolism
  2. Catabolism of low molecular weight proteins: including insulin, parathyroid hormone and calcitonin
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5
Q

Describe the glomerulus - a capillary network (3)

A
  1. Afferent arteriole branches to form this
    capillary network – leaves as the efferent arteriole
  2. Therefore a relatively high pressure capillary bed
  3. Major site of filtration
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6
Q

Describe a peritubular capillaries - a capillary network (2)

A
  1. Efferent arterioles form this capillary bed that
    perfuse the nephron tubules
  2. contains the vasa recta
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7
Q

Describe the vasa recta (5)

A
  1. A capillary network that is a part of the peritubular capillaries
  2. Descend around the lower portions of the loops of Henle
  3. Plays a special role in the concentrating of urine
  4. Blood flow through the vasa recta is sluggish
  5. Only about 1-2% of the total renal blood flow
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8
Q

What is a nephron in the kidney (4)

A
  1. Functional unit of the kidney
  2. Has two types that are based on
    a. location of the glomeruli
    b.Depth of penetration of the loops of Henle into the medulla
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9
Q

Compare cortical and juxtamedullary nephrons (4)

A

Cortical nephrons
2. Glomeruli in the outer and middle cortices
3. Loops extend to the junction of the cortex and medulla or into the outer zone of the medulla

Juxtamedullary nephrons
4. Loops extend more deeply into the medulla

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10
Q

What are the parts of then nephron (5)

A
  1. Glomerular capsule
  2. Proximal convoluted tubule
  3. Loop of Henle
  4. Distal convoluted tubule
  5. Collecting ducts
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11
Q

Explain the glomerular capsule (2)

A
  1. Blind ended expansion of the tubule
  2. Almost entirely surrounds the glomerulus
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12
Q

Explain the proximal convoluted tubule (2)

A
  1. Longest most winding portion of the nephron
  2. Form much of the tissue of the renal cortex
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13
Q

Explain the loop of Henle (2)

A
  1. Descending limb: Thin, Extends variable distance, Turns back on itself
  2. Ascending loop
    - Thin – terminates at the junction of the inner and outer medulla
    - Cortical nephrons therefore do not have thin ascending loops
    - Thick – returns to the glomerulus of origin in the cortex
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14
Q

Explain the distal convoluted tubule (4)

A
  1. Shorter and less twisted than the proximal convoluted tubules
  2. From termination of the ascending limb of the
    loop of Henle to the collecting tubule
    - Passes between the afferent and efferent arterioles
    - Area is called the juxtaglomerular apparatus
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15
Q

Explain the collecting ducts (1)

A

Number of arched tubules empty into a straight collecting tubule

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16
Q

Explain urine formation (3)

A
  1. Filter a large portion of the plasma (~20%), through the glomerular membrane into the tubules of the nephron
  2. Wanted substances (water, electrolytes) are reabsorbed into the plasma of the peritubular capillaries
  3. Small amount of substance is secreted
    into the tubules
17
Q

Explain the glomerular membrane permeability (4)

A
  1. Highly permeable (~ 100 times more permeable than other capillaries) due to fact that:
  2. Endothelial cells are fenestrated
  3. Slit-pores between the podocytes of the epithelial cells that form the visceral layer of the glomerular capsule
  4. Large surface area of the glomerulus
18
Q
A
19
Q

Compare the glomerular filtrate to blood (4)

A
  1. Same composition and osmolality as the blood plasma except:
  2. No erythrocytes
  3. Little protein (~0.03%; 1/200 of the protein
    found in plasma)
  4. Donnan equilibrium means that filtrate will have a higher concentration of chloride and bicarbonate ions and a lower concentration of positively charged ions (~5% difference from plasma)
20
Q

What is the glomerular filtration rate (GFR) (2)

A
  1. The rate at which fluid leaves the glomerulus and enters the glomerular capsule
  2. Directly proportional to the filtration
    pressure (net pressure forcing fluid through the glomerular membrane)
21
Q

How is hydrostatic pressure involved in GFR (4)

A
  1. Glomerulus ~ 60 mm Hg
    - Forces fluid from the glomerulus into the glomerular capsule
  2. Glomerular capsule ~ 18 mm Hg
    - Resists the flow of fluid from the glomerulus into the glomerular capsule
22
Q

How is colloidal osmotic pressure involved in GFR (3)

A
  1. Glomerulus ~ 32 mm Hg
    - Resists the flow of fluid from the glomerulus into the glomerular capsule
  2. Glomerular capsule ~ 0
23
Q

How is net filtration pressure involved in GFR (2)

A
  1. Glomerular hydrostatic pressure - (glomerular
    colloidal osmotic pressure + capsule hydrostatic pressure)
  2. 60 – (32 + 18) = 10 mm Hg
24
Q

Discuss the factors that influence the glomerular filtration rate (GFR)

A
  1. Rate of renal blood flow
  2. If blood flow rate is slow, colloidal osmotic
    pressure quickly rises in the glomerulus (due
    to filtration into the capsule) and this high
    glomerular colloidal osmotic pressure opposes further filtration into the glomerulus
  3. Glomerular pressure
  4. Plasma colloidal pressure
  5. Glomerular capsule pressure
25
Q

When does afferent arteriole constriction occur? What is the effect? (4)

A
  1. Occurs during sympathetic nerve stimulation
  2. Decreases the GFR by:
    - Decreasing rate of blood flow
    - Decreasing hydrostatic pressure in the glomerulus
26
Q

What is the effect of afferent arteriole dilation? (3)

A
  1. Increases the GFR by:
    - Increasing rate of blood flow
    - Increasing hydrostatic pressure in the glomerulus
27
Q

Effect of efferent arteriole constriction (2)

A
  1. Increases the GFR by:
    - Increasing hydrostatic pressure in the glomerulus
  2. Low blood pressure triggers renin release, leading to angiotensin II, which tightens the efferent arteriole. This helps maintain GFR, but too much constriction raises osmotic pressure, eventually lowering GFR.
28
Q

What is the effect of increased blood pressure?

A
29
Q

What is the effect of increased blood pressure? (2)

A
  1. Expect an increase in GFR but blunted by autoregulation: with autoregulation afferent arterioles automatically contract when blood pressure increases
  2. Result is a smaller increase in GFR than would otherwise occur – however even a small increase in GFR will still greatly increase urinary output

Anatomy and Physiology 1 (17 decks)

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