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Human Physiology > Renal System > Flashcards

Renal System Flashcards

1
Q

Describe the kidneys

A

The inner surface of the lower back.

Account for ~ one percent of total bodyweight

They receive about 25% of total cardiac output

Their function is filtering the blood

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2
Q
A
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3
Q

What are the functional units of the kidney

A

Nephron - also known as the renal tubules or kidney tubules.

Each nephron is an intricate epithelial tube

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4
Q

How many nephron are there per kidney?

A

Approximately 1.25 million nephron

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5
Q

How thick is the nephron wall?

A

It is one cell thick (simple cuboidal epithelium)

These cells are specialised for absorption and secretion of material

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6
Q

Describe the flow of fluid through a cortical nephron

A
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7
Q

What are found on the inner surface?

A

Microvilli - this increases surface area for ion and water transport

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8
Q

What are adjacent cells joined by?

A

Tight junctions - this restricts diffusion between the lumen (inside of nephron) and the extra cellular space

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9
Q

What is happening at stage one and stage two?

A
  1. Glomerulus - a network of capillaries with relatively high blood pressure forcing fluid out of the vessels.
  2. Bowman capsule - fluid from the blood is filtered into the cavity of the capsule
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10
Q

What is happening at stage 3,4 and 5?

A
  1. Filtration of blood.
  2. Proximal convoluted tubule - site of re absorption of glucose, vitamin C, and some salts (75% Na) and some water
  3. Loop of Henle - site of water reabsorption to adjust osmotic pressure of the blood and concentrate the urine in the collecting duct
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11
Q

What is happening in stages Six and seven?

A
  1. Distal convoluted tubule - site of further absorption of material and also secretion of material. Thereby affecting the acidity of the urine and the blood.
  2. Collecting duct - final site of water absorption affecting the overall concentration of the urine. Collecting duct serves several nephron and empties into the renal calyx and from there to the renal pelvis and then the ureter.
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12
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13
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14
Q

What does the filtration membrane in the glomerulus act like?

A

A sieve

Large particles such as blood cells and proteins can’t leave.

Water and small molecules can flow through the slits.

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15
Q

What is the journey through a Nephron?

A
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16
Q

How does filtration occur?

A
  1. Filtration from blood plasma into nephron.
  2. Tubular reabsorption from fluid into blood.
  3. Tubular secretion from blood into fluid.

Urine contains excreted substances
Blood contains reabsorbed substances

17
Q

What is the glomerular filtration rate?

A

125ml/min

180l/day

99% of the filtered water water is reabsorbed

18
Q

What does filtrate consist of?

A

Water and non-protein solutes (Na, K, Cl, glucose and urea)

19
Q

What is filtration driven by?

A
  1. The sievelike properties of the capillary walls and the walls of the Bowman capsule.
  2. The pressure gradient from capillaries to Bowman capsule.
20
Q

What is the overall filtration pressure and how is it worked out?

A
  1. Capillary blood pressure (60mmHg) - OUT
  2. Bowman’s capsule pressure (20mmHg) - IN
  3. Capillary osmotic pressure (plasma proteins) (30mmHg) - IN

Overall filtration pressure = 10mmHg OUT

21
Q

Where does reabsorption begin?

A

Proximal convoluted tubule

~65-75% of filtered Na is reabsorbed here.

ACTIVE process involving membrane pumps and ATP

22
Q

What is the transport maximum?

A

Maximum amount of material which can be transported

23
Q

How does diabetes mellitus work?

A

Lack of insulin > glucose not absorbed into the cells > plasma glucose increases > filtered glucose increases > glucose infiltrate exceeds the transport Max for glucose > glucose appears in the urine

24
Q

What is hyperglycaemia?

A

Increased urine volume and glycosuria (glucose in urine)

25
Q

What is reabsorbed and secreted in the distal convoluted tubule?

A

Reabsorbed - Na, Cl and HCO3

Secreted (K, H, NH3)

26
Q

What is the reabsorption of bicarbonate and the secretion of hydrogen ions important in regulating?

A

Plasma pH (7.4)

This is known as the acid base balance

27
Q

What happens in the collecting duct?

A

This is the final absorption of water -influenced by ADH hormone

This influences the volume and concentration of urine

Important in regulating normal plasma and therefore blood pressure

28
Q

What happens to the urinary output and concentration in dehydration?

A

In dehydration, there is a reduced urinary output and urine is concentrated

29
Q

What is the negative feedback system when there is a decreased blood volume?

A
  1. Decreased blood volume.
  2. Increase production of ADH in hypothalamus.
  3. ADH act on renal collecting duct.
  4. Increases permeability of renal collecting duct.
  5. Increases water absorption in collecting duct.
  6. Decreased urine output. Increased fluid retention in plasma.
  7. Increased blood volume.
30
Q

What are some other roles of the kidneys?

A
  1. Control of red blood cell synthesis.
  2. Maintenance of fluid balance and blood pH.
  3. Elimination of drugs from the body.
  4. Production of hormones regulating blood pressure.
  5. Calcium and phosphorus balance and bone health - kidneys produce the active form of vitamin D

Human Physiology (8 decks)

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