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Renal Physiology > Renal Anatomy and Physiology > Flashcards

Renal Anatomy and Physiology Flashcards

1
Q

What are the functions of the kidney?

A
  1. Regulates fluid concentration, inorganic-ion composition, and volume of internal environment
  2. Production and release into blood of glucose from amino acids and other precursors
  3. Excretion of chemical substances in urine (e.g. drugs, pesticides, food additives, etc)
  4. Excrete metabolic wastes in urine (e.g. urea, uric acid, creatinine)
  5. Regulates acid base balance
  6. Acts as an endocrine gland
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2
Q

What is homeostasis?

A

Maintenance of constant internal environment
- Examples of carefully controlled parameters include arterial pressure and blood volume, plasma levels of glucose, Na+, K+ and Ca2+ and H+ etc

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3
Q

What are the functions of the kidneys as a homeostatic organ?

A
  1. gluconeogenesis
  2. excretion of chemical substances in urine
  3. as an endocrine organ
  4. production of erythropoietin
  5. Activation of vitamin D
  6. excretion and retention of fluids and electrolytes
  7. acid base balance
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4
Q

What is gluconeogenesis?

A

Glucose synthesised from amino acids (glutamine, alanine) and other precursors (lactate, glycerol)

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5
Q

Where does gluconeogenesis occur?

A

renal cortex

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6
Q

Function of gluconeogenesis?

A
  1. Compensate for impaired hepatic glucose release

2. Ensures maintenance of nutritional balance

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7
Q

What chemical substances can be excreted in urine?

A

drugs, pesticides, food additives, metabolic wastes, hormone metabolites
e.g. urea, creatinine, uric acid, end products of haemoglobin breakdown

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8
Q

Why do chemical substances need to excreted?

A

to limit the body’s exposure to toxic compounds of exogenous and endogenous origin

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9
Q

How does the kidney function as an endocrine gland?

A

Production of renin, angiotensin I and II : maintains blood pressure
- Angiotensin II constricts renal efferent and afferent arteriole blood vessels

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10
Q

Where is erythropoietin synthesised?

A

the interstitial cells of cortex and outer medulla

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11
Q

Synthesis and release of erythropoietin is stimulated by?

A

low haematocrit / low blood oxygen carriage

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12
Q

Where does erythropoietin act?

A

erythroid progenitor cells in hematopoietic bone marrow

- increases red blood cell production

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13
Q

Function of RBCs?

A

transport of oxygen + carbon dioxide to and from tissue

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14
Q

How do the kidneys activate vitamin D?

A

Produces active form of vitamin D3 (calcitriol) by hydroxylating the vitamin at the number ‘1’ position

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15
Q

Vitamin D allows for the absorption of what in the GIT?

A

calcium

- plays an essential role in calcium and phosphate regulation

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16
Q

Vitamin D deficiency causes?

A
  1. rickets - children

2. osteomalacia - adults

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17
Q

How do the kidneys aid in excretion and retention of fluids and elctrolytes?

A

Allows regulation of

  • fluid concentration
  • inorganic-ion composition
  • volume of internal environment
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18
Q

Which hormone aids in excretion and retention of fluids and electrolytes?

A

aldosterone

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19
Q

What does aldosterone do?

A

promotes secretion of K+ and H+ and retains Na+ thereby preventing disturbance of sensitive electrolyte equilibrium

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20
Q

The acid/base balance is maintained between what pH?

A

7.35 and 7.45

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21
Q

What is the aim of acid/base regulatory mechanisms?

A

maintain pH of arterial plasma

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22
Q

How is acid base balance achieved?

A
  1. in coordination with the respiratory system

2. excreting acids and regulating body fluids buffer stores

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23
Q

The urinary system consists of?

A
  1. 2 kidneys - produce urine
  2. 2 ureters - transport urine to bladder
  3. urinary bladder - temporarily stores urine
  4. urethra - transports urine to the outside
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24
Q

Where are the kidneys located?

A

lie retroperitoneally in the posterior abdominal wall

25
Q

How much does an adult kidney weigh?

A

150g

26
Q

How much cardiac output do the kidneys receive?

A

receive 20 to 25% of cardiac output (~ 1.25 L/min)

27
Q

Describe the shape of the kidney?

A

lateral surface is convex and medial surface is concave

28
Q

How many renal pyramids are in the medulla?

A

8 - 18 pyramids

29
Q

What are the regions of the medulla?

A

corticomedullary border > papilla > minor calyx > major calyx > pelvis > ureter

30
Q

What is the nephron?

A

The functional unit of the kidney

- 1.2 million nephrons in each kidney

31
Q

What are the types of nephrons?

A
  1. Cortical nephrons - 80%

2. Juxtamedullary nephrons - 20%

32
Q

Describe the structure of cortical nephrons?

A
  • Glomerulus near the outer regions of the cortex
  • Have short loops extending into boundary between outer and inner medulla
  • Surrounded by peritubular capillaries
33
Q

Describe juxtamedullary nephrons?

A
  • Glomerulus near the inner cortical regions
  • Have long loops extending as far as tip of medulla
  • Play a special role in urine production
34
Q

The nephron consists of?

A 
renal corpuscle (glomerulus + bowman’s capsule)
proximal tubule
loop of Henle
distal tubule
collecting duct system
35
Q

What is the glomerulus?

A

A cluster of blood capillaries from which filtrate forms

- within the renal corpuscle

36
Q

The glomerular cell layer consists of?

A

endothelial cells, basement membrane and layer of podocytes

37
Q

What is Bowmans capsule?

A
  • Surrounds the glomerulus and contains bowman’s space
  • Filtrate passes from glomerulus into tubular system through the Bowman’s space
  • Where glomerulus and tubule meet
38
Q

What is the tubular portion of the nephron?

A

Is an epithelial structure consisting of many divisions designed to convert blood filtrate into urine

39
Q

What is the histological structure of the tubular portion of the nephron?

A
  • Consists of single epithelial cell layer
  • Tight junctions on the luminal side
  • Lateral surface continuous with interstitial fluid
40
Q

What is the juxtaglomerular apparatus?

A

Specialised region where ascending thick limb contacts the afferent arteriole

41
Q

What are the components of the juxtaglomerular apparatus?

A
  1. macula densa

2. granular cells (juxtaglomerular cells)

42
Q

What is the Macula densa?

A

region of specialised epithelial cells on the thick ascending limb that senses fluid flow and composition

43
Q

What are granular cells?

A

endocrine cells on the afferent arteriole that produce, store and release renin
- Part of feedback mechanism that regulates renal blood flow and filtration rate

44
Q

What is glomerular filtration?

A

Production of ultrafiltrate at the glomerulus and the transport of electrolytes/solutes with the water in which they are dissolved through the cells of the tubular system

45
Q

Glomerular filtration is derived by?

A
  1. starling forces

2. high hydrostatic pressure - 60 mmHg

46
Q

What is reabsorption?

A

Process of moving substances in the filtrate from tubule lumen into blood of peritubular capillaries
- 70% of filtered volume is reabsorbed in the proximal tubules

47
Q

Reabsorption is facilitated by?

A

Na+/K+ -ATPase on the basolateral membrane

48
Q

What substances are reabsorbed?

A
  1. Vitamins, amino acids, glucose, electrolytes, water, etc

2. All glucose

49
Q

What is secretion?

A

The deposition into urine of organic anions and cations, largely by proximal tubules
- also by distal tubules and collecting ducts

50
Q

What kind of substances are poorly filtered?

A

protein bound hydrophobic drugs and endogenous molecules

- get secreted later on

51
Q

Describe the substances that are poorly filtered?

A
  1. xenobiotic agents, including a wide range of alkaloids and other positively charged, heterocyclic compounds of dietary origin
  2. Cationic drugs of therapeutic or recreational use; or other cationic toxins of environmental origin (e.g. nicotine)
52
Q

What is the amount of blood supply to the kidney?

A

20-25% of cardiac output

53
Q

What is the weight of the kidney?

A

0.5% of total body weight

54
Q

Describe the amount of blood supply within each part of the kidney?

A
  1. cortex - 90%

2. medulla - 10%

55
Q

Blood flow to the medulla is through?

A

vasa recta of the peritubular capillaries

56
Q

Why is the blood flow to the medulla so low?

A

high resistance of the long vasa recta

57
Q

Why is low blood flow important in the medulla?

A

minimises washout of the hypertonic medullary interstitium

58
Q

Describe the innervation of the kidney?

A

renal nerves

59
Q

The sympathetic innervation targets?

A
  1. juxtaglomerular apparatus
  2. smooth muscles of the arterioles
  3. mesangial cells

Renal Physiology (8 decks)

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