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1Principles of Biomedicine - MD1 > 141 - Kidney Function I > Flashcards

141 - Kidney Function I Flashcards

1
Q

Kidney functions 1 2 3 4 5 6

A

1) Water, sodium homeostasis 2) Control of ECF ion concentration (K, Ca, Mg, Cl, HPO4) 3) Acid-base balance 4) Excretion of waste products and xenobiotics 5) Endocrine functions 6) Formation of concentrated/dilute urine

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2
Q

Most important function of the kidneys

A

Water and sodium balance

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3
Q

Why do the kidneys regulate ECF ion concentration?

A

All can kill if not maintained within a tight band; High[K+] sudden death; high P or low Ca++ cause fractures, Mg++ critical in nerve, muscle and brain

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4
Q

Which organ, in tandem with the kidneys, regulate acid-base balance?

A

Lungs

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5
Q

Breakdown of what leads to urea formation?

A

Protein

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6
Q

Role of vitamin D3

A

Calcium absorption

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7
Q

Examples of renal endocrine functions 1 2 3 4

A

EPO, renin, Vitamin D3, PGI2 (prostacyclin)

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8
Q

*Structure of a nephron

A
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9
Q

Where is the initial filtrate formed in the kidneys?

A

Bowman’s capsule

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10
Q

Size of fenustrations in Bowman’s capsule capillaries?

A

2nM

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11
Q

Why mightn’t all molecules under 2nM be filterable in the kidneys?

A

Bowman’s capsule capillary fenestrations are negatively-charged, so negatively-charged molecules are less-likely to fit through (EG: serum albumin), positively-charged molecules over 2nM can fit through.

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12
Q

Average GFR in humans

A

180L/day (60mL/minute/single kidney)

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13
Q

Average length of loop of Henle

A

Only very shallowly enters medulla of kidney (85% of nephrons). 15% go very deep (long loops of Henle)

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14
Q

Significance of junction between thick ascending limb and distal tubule

A

Where the nephron makes contact with the home glomerulus and the afferent arteriole. Contact point is the macula densa.

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15
Q

Arrangement of collecting ducts

A

Often several distal tubules (from different nephrons) feed into collecting duct. Collecting ducts fuse, until they form the renal pelvis that feeds into the bladder

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16
Q

Sequential segments of the nephron 1 2 3 4 5 6 7

A
  1. Bowman’s capsule 2. Proximal Tubule – pars recta and PCT ( convoluted tubule) 3. Thin descending limb of Henle’s Loop – tDLH 4. Thin ascending limb of Henle’s Loop – tALH this is very short in superficial cortical nephrons It is long in JM nephrons 5. Thick Ascending limb – TAL 6. Distal Tubule –DT 7. Collecting Duct – CD
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17
Q

Role of proximal tubule

A

Reabsorbs ~65% of water, NaCl, most solutes. Absorbs 100% of very important molecules (EG: glucose, amino acids, lactic acid) using active transport.

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18
Q

Role of the loop of Henle (thin descending limb)

A

Concentrating (1200 miliosmolar/L at tip of loop of Henle)

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19
Q

Role of thick ascending loop of Henle

A

Dilutes filtrate

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20
Q

Macula densa

A

Part of the juxta-glomerular apparatus At junction between ascending limb and distal tubule

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21
Q

Distal tubule role

A

Fine-tunes water/ion balance of filtrate. Alters concentration of urine according to the body’s needs.

22
Q

Collecting duct role

A

Aldosterone-dependent equillibrator. Surrounded by fluid of a high osmolarity. How much water escapes collecting duct is contingent on permeability of collecting duct to water (aquaporins).

23
Q

Role of aldosterone in the collecting duct

A

Induces aquaporin expression, which increases water loss from collecting duct (increases urine concentration)

24
Q

Superficial cortical glomeruli

A

~90% of glomeruli. Loop of Henle penetrates a short distance into the medulla Efferent arterioles give rise to cortical capillaries surrounding the proximal and distal convuluted tubules

25
Q

Juxtamedullary glomeruli

A

Loop of Henle penetrates deep into the medulla Efferent arterioles become the vasa recta that also penetrate deep into the medulla, parallel to the loops of Henle

26
Q

Role of juxtamedullary glomeruli

A

They account for the medullary concentration gradient; osmolarity increases from 300 at the C-M junction to 1200 in the deepest part (papilla) of the medulla

27
Q

Blood vessels that surround nephron path

A

Peritubular capillaries

28
Q

Name for capillaries accompanying loops of Henle

A

Vasa recta

29
Q

*Arrangement of vasculature of nephron

A
30
Q

Parts of nephron where reabsorption occurs

A

All parts

31
Q

Things that can occur in the nephron SERF

A

F= Filtration R = Reabsorption S = Secretion E = Excretion

32
Q

Part of nephron where filtration occurs

A

Bowman’s capsule

33
Q

Where does secretion occur?

A

Proximal, distal tubules, collecting duct

34
Q

Is secretion active or passive?

A

Active

35
Q

Role of secretion

A

Takes substances that couldn’t be passively filtered out of the nephron by active transport

36
Q

*Areas in nephron where filtration, reabsorption, secretion and excretion occur

A
37
Q

Does reabsorption or filtration account for the reuptake of more products?

A

Reabsorption

38
Q

Example of a situation where excretion = filtration - reabsorption + secretion doesn’t apply

A

Proteins (a few grams are excreted each day) are filtered and not reabsorbed, but aren’t excreted, as they are broken down in the proximal tubule (in health)

39
Q

*Glomerulus diagram

A
40
Q

Things that aren’t filtered in health 1 2 3 4 5 6 7 8

A

1) RBC 2) WBC 3) Platelets 4) Albumin (a very small amount is filtered) 5) IgG 6) Small peptides (partially filtered) 7) Organic solutes bound to proteins 8) Protein-bound drugs

41
Q

Things that are filtered in health 1 2 3 4

A

1) Albumin (very small amount) 2) Small ions 3) Organic solutes (free) 4) Drugs (free)

42
Q

Why can albumin filtration rate increase in disease?

A

Bowman’s capsule fenestrations can lose their negative charge

43
Q

What forms the filtration mechanism in Bowman’s capsule?

A

Fenestrations in capillary endothelium and podocyte foot processes.

44
Q

*Bowman’s capsule filtration apparatus

A
45
Q

Part of Bowman’s capsule that responds to angiotensin II

A

Mesangial cells

46
Q

Name for space between podocyte foot processes

A

Filtration slits

47
Q

Common filtration rate

A

125mL/minute

48
Q

Normal filtration fraction

A

20% of renal plasma flow

49
Q

Forces that affect GFR 1 2 3 4

A

1) Hydrostatic pressure in the glomerular capillary (50mmHg) 2) Hydrostatic pressure in Bowman’s capsule (10mmHg) 3) Oncotic pressure in the glomerular capillary (25->40mmHg) 4) Oncotic pressure in Bowman’s capsule (0mmHg)

50
Q

What determine oncotic pressure?

A

Plasma proteins that can’t be filtered

51
Q

Driving force of hydrostatic pressure between glomerular capillary and Bowman’s capsule

A

40mmHg (50mmHg in glomerular capillary, 10mmHg in Bowman’s capsule)

52
Q

Driving force of oncotic pressure between glomerular capillary and Bowman’s capsule

A

25-40mmHg (25-40mmHg in glomerular capillary, 0mmHg in Bowman’s capsule)

1Principles of Biomedicine - MD1 (157 decks)

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