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Physiology 1B > Kidneys and Urinary System > Flashcards

Kidneys and Urinary System Flashcards

1
Q

List the functions of the urinary system

A

Excretion of metabolic products and toxic substances
Retain useful substances
Regulate body fluid osmolality and volume
Regulate electrolyte and acid base balance
Produce and secrete hormones
Modify and regulate plasma composition

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2
Q

Describe the basic structure of the kidneys

A

Cortex surrounds the medulla
Medulla is made up of renal pyramids
A the base of the pyramids is papilla which drain into the renal pelvis
Leaving the renal pelvis is renal artery, nerve and vain and the ureter

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3
Q

What is a nephron?

A

Building block and functional unit of the kidneys

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4
Q

What are the two different types of nephrons?

A

Cortical- majority, role in absorption and secretion

Juxtamedullary- create conditions to concentrate urine

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5
Q

What is the function of nephrons?

A

Generate ultrafiltrate from the blood

Control how much is reabsorbed and excess removed as urine

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6
Q

What is the glomerulus?

A

Capillary network within bowmans capsule of the nephron

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7
Q

Where is the site of filtration in the nephron?

A

Glomerulus

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8
Q

What happens in the proximal tubule?

A

Most fluid is reabsorbed

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9
Q

Where is urine concentration controlled in the nephron?

A

Juxtamedullary nephrons loop of henle

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10
Q

What is the role of the distal convoluted tubule?

A

Control electrolyte balance

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11
Q

What cell types form filtration barrier around the glomerulus?

A

Podocytes- wrap capillaries to allow fluid but not protein leakage, full coverage of capillary by primary and secondary processes
Pedicels- extra coverage of capillaries to only allow water and small molecules through

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12
Q

What is meant by the juxtaglomerular apparatus?

A

Point where distal tubule loops back and makes contact with the glomerulus
Specialised hormone secreting region

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13
Q

What is the arterial supply to the nephron?

A

Branch of renal artery forms afferent arteriole which enters glomerulus
Efferent arteriole leaves the glomerulus

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14
Q

What is the vasa recta

A

Formed from efferent arteriole, surrounds nephron to supply nutrients, gas exchange and collect water and solutes reabsorbed by nephron

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15
Q

Why is blood supply to the kidney autoregulated?

A

Keep glomerular filtration rate constant and keep it functioning despite arterial blood pressure changes

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16
Q

What is used to measure glomerular filtration rate and what is it?

A

Using creatinine which is waste product of natural breakdown of muscle, usually delivered into circulation at constant rate

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17
Q

Why can creatinine be used to measure GFR?

A

Is freely filtered from glomerulus and not reabsorbed from tubule or secreted into tubule so what appears in urine is directly from glomerular filtration

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18
Q

Describe the structure of the proximal tubule walls

A

Apical surface of epithelial cells have microvilli

Cells packed with mitochondria

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19
Q

What is the function of the proximal tubule?

A

Reabsorption of solutes and bulk of filtered fluid back into the blood
Helps regulate body fluid pH
Secretes some organic molecules, often end products of metabolism

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20
Q

What type of process is glucose transport in the proximal tubule?

A

Carrier mediated process

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21
Q

What are the normal levels of plasma and intracellular fluid pH?

A

Plasma- 7.35-7.45

Intracellular- 7-7.1

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22
Q

Why is plasma osmolality regulated?

A

Prevent cell swelling or shrinkage, one of the most tightly controlled homeostatic mechanisms

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23
Q

What hormone is responsible for controlling body water?

A

Antidiuretic hormone

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24
Q

How is antidiuretic hormone secreted?

A

Hypothalamus produces in paraventricular and supraoptic nuclei then is transported to axon terminals in posterior pituitary to be released into the blood

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25
Q

When is there increased release of ADH?

A

Increase in plasma osmolality

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26
Q

What are the physiological mechanisms to control water balance?

A

Drinking and urine output

27
Q

What is the action of ADH?

A

Increases water permeability of collecting duct
Increases NaCl reabsorption in thick ascending limb
Increases urea permeability in inner medullar region of collecting duct
All help water reabsorption

28
Q

What ion transporters are present in the ascending limb?

A

Na-K-Cl cotransporter in apical membrane and Na pump in basolateral membrane

29
Q

Explain how ADH takes action

A

ADH from blood binds to V2 receptor on basolateral membrane of tubule cell
Stimulates adenylate cyclase to generate cAMP and activate protein kinases
Increases insertion of aquaporins into apical surface of cell increasing permeability
More water flows out of tubule into medullary interstitium

30
Q

What happens when blood volume is decrease?

A

Na+ retention in blood increased in kidney
Water follows Na+ into blood
Blood volume restored

31
Q

What are the high pressure sensors of blood volume?

A

Arterial baroreceptors- carotid sinus, aortic arch. Increases sympathetic activity to kidneys in response to hypovolaemia
Juxtaglomerular apparatus- renal blood flow decreases, hormonal response reduces Na+ and water loss in the kidneys

32
Q

What are low pressure sensors of blood volume?

A

Cardiac atria

Pulmonary vasculature

33
Q

Explain the importance of regulating blood volume

A

Plasma and cellular components are in fixed proportions so all compartments are regulated by regulating blood volume
Blood pressure is determined by blood volume so also controls arterial blood pressure

34
Q

What response do juxtaglomerular apparatus have in response to low blood pressure?

A

Renin is secreted

35
Q

How is Angiotensin I formed?

A

Renin binding with angiotensinogen

36
Q

How is angiotensin I converted to angiotensin II?

A

In lung by angiotensin converting enzyme

37
Q

What is angiotensin II and what is its role?

A

Active form of renin

Causes vasoconstrictor response, stimulates ADH release and stimulates aldosterone release

38
Q

What is aldosterone and how does it work?

A

Na converting hormone

Increases Na+ reabsorption by nephron drawing in water

39
Q

How does aldosterone work?

A

Acts on distal convoluted tubule
Binds to receptor which stimulates transcription of apical Na+ channels
Increased NaCl reabsorption in distal tubule and collecting duct and Na+ enters blood by ATPase
Water follows paracellularly

40
Q

What is the response to increased blood volume?

A

Atria stretch causing release of ANP which causes excretion of Na+ and so water

41
Q

What is ANP and where is it made and stored?

A

Atrial natriuretic peptise

Synthesised and stored in atrial myocytes

42
Q

What happens in hypokalaemia and hyperkalaemia?

A

Hypo- cell less excitable

Hyper- cell more easily excitable

43
Q

Explain how extracellular potassium is regulated

A

Increased plasma K+ enhances secretion and depolarises zona glomerulosa cells causing Ca2+ influx into cell to stimulate aldosterone release
Aldosterone helps enhance secretion of K+

44
Q

Where is body calcium stored?

A

Most in bones and teeth

Only 1% accessible in ECF

45
Q

What states is calcium found in the body?

A

Ionised- 50%, biologically active
Bound to plasma proteins- 40%
Rest is complexed to plasma anions

46
Q

What affect does alkalaemia have on calcium binding?

A

Ca2+ is competitive with H+ to bind, the less H+ more Ca2+ binds so less is found in ionised state

47
Q

What limits calcium intake?

A

Absorption in the gut

48
Q

How is active vitamin D3 synthesised?

A

Cholecalciferol taken in by diet or sun is hydroxylated in liver and kidneys to the active form of vitamin D

49
Q

What is the main role of vitamin D on calcium?

A

Regulates intestinal calcium absorption

50
Q

Describe the pathway of urine from the collecting duct

A

Renal pelvis
Ureters
Bladder
Urethra

51
Q

How does urine pass down the ureters?

A

Peristalsis originating form pacemaker in renal pelvis

52
Q

What are the different regions of the bladder walls made of?

A

Dome- detrusor smooth muscle

Trigone- non-contractile

53
Q

What is innervation of bladders detrusors smooth muscle?

A

Parasympathetic nerves that release acetyl choline to cause muscle contraction

54
Q

Describe the lining of the bladder walls and its purpose

A

Mucosa, urothelium, suburothelium

Tight barrier to prevent urine leakage

55
Q

What is the external urethral sphincter muscle type?

A

Skeletal

56
Q

What is meant by the bladder being compliant?

A

Volume in the bladder can increase with a very small pressure rise

57
Q

What are the nervous pathways of storing urine?

A

Sensory afferent nerves synapse from bladder to midbrain and signals are relayed, one to prefrontal cortex and makes choice to not void

58
Q

What nerve is supressed in order to keep the bladder relaxed?

A

Pelvic nerve

59
Q

What nerve contracts the internal urethral sphincter?

A

Hypogastric nerve

60
Q

What nerve contracts the external urethral sphincter?

A

Pudendal nerve

61
Q

What nerve causes the bladder to contract?

A

Active pelvic nerve

62
Q

Why doe the urethra relax?

A

Inactivated hypogastric nerve

63
Q

What is the response to increased blood volume?

A

ANP is released by atrial myocytes in response to atria overstretching
Causes inhibition of aldosterone and renin secretion, inhibition of ADH release causing increased water secretion in urine, vasodilates afferent arteriole increasing GFR and causes reduced sodium reabsorption in CT so reduced water reabsorption

Physiology 1B (4 decks)

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