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RENAL > A. STRUCTURE AND FUNCTION OF KIDNEY > Flashcards

A. STRUCTURE AND FUNCTION OF KIDNEY Flashcards

1
Q

what are the 2 main functions of the kidney

A
  • excretion
  • regulation
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2
Q

regulations of the kidney

A
  • control of water and electrolyte (K+, Na+, Cl-) balance
  • control of arterial blood pressure (through blood volume as increased blood volume = increased blood pressure)
  • control of acid-base balance (H+, HCO3-) as kidney works with lungs to regulate fluid pH and kidney gets rid of excess ie - acid from metabolism
  • endocrine: EPO, renin, 1,25-dihydroxyvitamin D3 (calcitriol), PGs
  • glucose synthesis (gluconeogenesis) during prolonged fasting
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3
Q

what does the kidney excrete

A
  • metabolic waste
    urea (from amino acids)
    creatinine (from creatine)
    uric acid (from nucleic acid)
    end products of haemoglobin breakdown (yellow)
    hormone metabolites
  • foreign substances (drugs - metabolised or unmetabolised, pesticides, food additives)
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4
Q

what happens with kidney failure

A

disruption of homeostatic functions and we get severe abnormalities in body fluid volumes and composition

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5
Q

where do the kidneys sit

A
  • paired bean-shaped organs
  • lie in posterior wall of abdominal cavity and on either side of vertebral column
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6
Q

why is the right kidney lower than the left

A

due to liver positioning

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7
Q

size and weight of kidney

A

115-170g
11cm long by 6cm wide by 3cm thick
size of a clenched fist

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8
Q

what is the kidney surrounded by

A

tough protective fibrous renal capsule and visceral fat
(protects from mechanical trauma and shock)

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9
Q

what does the medial side of the kidney contain

A

a notch (helium) from which the renal artery, renal vein, nerves, pelvis and ureter pass through

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10
Q

what is the outer layer of kidney called

A

cortex

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11
Q

what is the inner layer of the kidney called

A

medulla
divided into multiple cone-shaped pyramids called nephrons (functional units of kidney)

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12
Q

what is the nephron

A
  • functional unit of kidney
  • 5 anatomical regions
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13
Q

how many nephrons is the kidney composed of

A
  • 1 million
  • we don’t make them
    (age >40, natural loss of 10% per 10 years so by 70 we have 30% fewer functioning nephrons)
  • to see significant changes need 50% lost
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14
Q

what components does the nephron consist of

A

vascular (blood vessels) and tubular (nephron tube) components

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15
Q

blood supply to kidneys

A

blood flow to both kidneys is about 20-25% of total cardiac output (1.2L/min)

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16
Q

what are the 2 blood capillary beds

A

glomerular and peritubular capillaries

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17
Q

where do the afferent arterioles deliver blood to

A

glomerular capillaries (filtration occurs and this is the start of urine formation) and the glomerular capillaries rejoin to form efferent arterioles

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18
Q

what do the efferent arterioles do

A
  • take unfiltered blood away from glomerulus
  • they subdivide into peritubular capillaries and supply blood all around there kidney
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19
Q

difference in afferent and efferent arterioles

A
  • efferent are smaller in diameter
  • hence they receive blood with a relatively high hydrostatic pressure
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20
Q

what is the renal corpuscle made up of

A

Bowman’s capsule and the glomerulus

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21
Q

what are the glomerular capsules encapsulated in

A

Bowman’s capsule
collects filtered fluid from the capillaries

22
Q

what is ultrafiltration

A

the start of urine formation as we are forcing a lot of fluid and solutes out of capillaries into Bowman’s space

23
Q

where is the proximal convoluted tubule (PCT) and what is its main role

A
  • continues from Bowman’s capsule
  • lies entirely in cortex
  • reabsorption back into blood
24
Q

what cells are the PCT composed of

A
  • single layer of cuboidal cells which interlock extensively, connected by tight junctions at their luminal surfaces
  • microvilli present which increase the membrane SA
25
Q

loop of henle

A
  • forms a U-shape that dips into medulla
26
Q

what is the Loop of Henle composed of

A
  • thin descending limb which ends in the turn and plunges from cortex into the medulla
  • thin ascending limb (only in nephrons with long Loops of Henle)
  • thick ascending limb
27
Q

what is the key role of the Loop of Henle

A

urine concentration

28
Q

what is the macula densa

A

short segment of cells present at the end of the thick ascending limb of the loop of Henle

29
Q

what is the juxtaglomerular apparatus composed of

A
  • juxtaglomerular granular cells which secrete renin
  • afferent and efferent arteriole
  • macula densa (tubular cells)
30
Q

what role does the juxtaglomerular apparatus

A

controlling nephron function

31
Q

what is the appearance of the DCT

A

shorter and less convoluted than PCT

32
Q

what is the role of the collecting duct

A
  • DCT empties into the collecting duct
  • each collecting duct may drain fluid from up to 8 separate nephrons
  • ducts pass through the cortex and medulla to empty urine into the renal pelvis (ureter to bladder)
33
Q

what 2 types of tubular cells are the late DCT and collecting duct made up of

A
  • principal cells (P cells)
  • intercalated cells (I cells) - smaller proportion
34
Q

what role does I cells have

A

acid-base balance

35
Q

what innervation of the kidney

A
  • sympathetic nervous system (SNS)
  • no PNS innervation
36
Q

what effect does the SNS have on vascular smooth muscle: alpha-1 ARs

A
  • noradrenaline is the NT released
  • preferably afferent but also on efferent arterioles
  • vasoconstriction which decreases blood flow and decreases GFR
37
Q

what effect does the SNS have on juxtaglomerular (granular cells) of the juxtaglomerular apparatus: beta ARs

A
  • stimulate renin secretion (angiotensin II formation - first part of RAAs)
38
Q

what hormones act on the kidney

A
  • vasopressin/ADH
  • aldosterone
  • parathyroid hormone
  • natriuretic peptides
39
Q

what hormones are produced by the kidney

A
  • erythropoietin: only true hormone
  • renin
  • vitamin D3 (calciferol)
  • prostaglandins
40
Q

how does vasopressin/ADH work

A
  • increases permeability of nephron to water
  • leads to increased water reabsorption from filtrate into body so decreased water volume

*diuresis = production of urine
*anti-diuresis = less urine produced

41
Q

how does aldosterone work

A
  • part of RAAs
  • increases sodium and hence water reabsorption
42
Q

how does parathyroid hormone work

A
  • plasma calcium homestasis
  • increases calcium reabsorption from filtrate to plasma
43
Q

how do natriuretic peptides work

A
  • natriuresis is an increase in sodium excretion in urine followed by diuresis
  • via inhibition of sodium reabsorption, suppression of RAAs
  • vascular effects as well: vasodilation of afferent arteriole and vasoconstriction of efferent arteriole
44
Q

how does EPO work

A
  • stimulates RBC production
  • proliferation and then differentiation of haematopoietic stem cells in bone marrow to mature RBCs
45
Q

how does renin work

A
  • part of RAAs
46
Q

how does activated vitamin D3 work

A
  • plasma calcium homeostasis
  • increases plasma calcium
47
Q

how does prostaglandins work

A
  • paracrine effects
  • vasodilation within renal corpuscle in particular and the pelvis causing increased blood flow and increased GFR
48
Q

paracrine

A
  • secretion within interstitial fluid that bathes cells
  • travels short distance in IF (not blood) to affect neighbouring/adjacent cells
49
Q

endocrine

A
  • hormone produced by endocrine gland into blood
  • travels to reach target cell tissue
50
Q

what is the urinary system also known as

A

urinary tract or renal system

51
Q

what does the urinary system consist of

A

kidneys
ureters
bladders
urethra

RENAL (13 decks)

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