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biomed > renal system > Flashcards

renal system Flashcards

1
Q

key functions of the kidney

A

-removal of waste products
-regulation of fluid and electrolyte levels
-regulation of pH
-maintaining blood pressure and blood osmolarity
-production of hormones and renin
-gluconeogenesis

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2
Q

kidney structure

A

-10-12cm long, 5-7cm wide, 3cm thick
-dent of medial side known as hilum
-renal cortex [outer region of kidney, contains nephrons]
-renal medulla [inner region containing renal pyramids separated by renal columns]

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3
Q

nephrons

A

-functional units of kidney
-each kidney contains 1-1.25 million nephrons
-each nephron divided into renal corpuscle [filtration] and renal tubule [reabsorption and secretion]

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4
Q

basic nephron structure

A

-blood flows into renal corpuscle from afferent arteriole
-plasma is filtered [filtered fluid known as filtrate]
-filtrate flows into proximal [convoluted] tubule [now known as tubular fluid]
-then nephron loop/loop of Henle
-finally into distal tubule and collecting duct [now known as urine]

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5
Q

cortical nephrons

A

-make up 80-85% of all nephrons
-renal corpuscle located in outer region of cortex
-short nephron loop lie within cortex or outer medulla
-surrounded by peritubular capillaries [flow from efferent arterioles, reabsorbed and secreted material enters these caps.]

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6
Q

juxtamedullary nephrons

A

-renal corpuscle located near medulla
-long nephron loop surrounded by vasa recta [straight vessels] [flow from efferent arterioles]
-thin and thick limbs of ascending nephron loop [enable very dilute or very concentrated urine]

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7
Q

renal corpuscle -glomerulus

A

-capillary network
-fenestrated capillaries
-receive blood from afferent arteriole

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8
Q

renal corpuscle -glomerular capsule

A

-Bowmans capsule
-inner visceral layer consists of specialised cells called podocytes [cover fenestrated cap.]
-pedicels extend from podocytes and form
much smaller filtration slits around cap
-outer parietal layer constructed from squamous epithelial cells

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9
Q

nephron loop construction

A

-descending limb constructed from simple squamous epithelium
-thin ascending limb in juxtamedullary also simple squamous epithelium
-thick ascending limb constructed from cuboidal or low columnar epithelium
-reabsorption in nephron loop [20% water via descending limb, 25% Na+ and Cl- via thick ascending limb]

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10
Q

proximal tubule construction

A

-reabsorption occurs across and between tubule cells
-greatest reabsorption capacity due to cell type [simple cuboidal epithelium, possess microvilli, both facilitate diffusion rate]

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11
Q

distal tubule construction

A

-main role is in regulating fluid composition
-mostly constructed from simple cuboidal cells
-most remaining water and ions reabsorbed in DT
-final section of DT and start of collecting duct have cells with receptors of ADH and aldosterone [modulates Na+ and water resorption]

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12
Q

urine pathway and storage

A

-flows along collecting ducts and minor calyces
-join into major calyces and into renal pelvis
-renal pelvis feeds urine into ureter
-urine stored in bladder
-exits body via urethra

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13
Q

ureter inner mucosa

A

-constructed from transitional epithelium [able to stretch and distend without damage]
-mucous secreted to prevent damage from varying urine pH

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14
Q

ureter muscularis

A

-middle layer
-circular and longitudinal smooth muscle [inner longitudinal, outer circular]
-additional longitudinal layer in distal third section

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15
Q

ureter adventitia

A

-outer layer
-loose connective tissue
-blood, lymph and nervous supply
-anchors ureters in place

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16
Q

urinary bladder inner mucosa

A

-consisting of transitional epithelium
-allows for distension without damage
-facilitated by rugae [mucosal fold]

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17
Q

urinary bladder middle muscularis layer

A

-known as detrusor muscle
-three layers - inner longitudinal, central circular and outer longitudinal

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18
Q

urethra

A

-inner mucosa
-epithelium differs between males and females [male urethra runs through prostate and muscle in perineum]
-mixture of transitional, pseudostratified columnar, stratified columnar and non-keratinised stratified squamous epithelia

19
Q

factors driving net filtration

A

-glomerular blood hydrostatic pressure
-capsular hydrostatic pressure
-blood colloid osmotic pressure

20
Q

glomerular blood hydrostatic pressure

A

-GBHP
-efferent arteriole has smaller diameter than afferent
-forces fluid out of glomerular capillaries

21
Q

capsular hydrostatic pressure

A

-CHP
-hydrostatic pressure within glomerular capsule
-resists fluid exiting glomerular cap

22
Q

blood colloid osmotic pressure

A

-BCOP
-osmotic pressure of blood solutes
-opposes fluid loss into capsular space

23
Q

glomerular filtration rate

A

-amount of filtrate produced in both kidneys per minutes
-maintained around 125ml/min in males and 105ml/min in females
-if its to high to many solutes make be lost as they cannot be reabsorbed quickly enough,
-if to low waste metabolites may not be fully removed and would build up in blood

24
Q

GFR and renal failure stages

A

-impaired GFR 60-100ml/min
-mild renal failure 30-60ml/min
-moderate to severe renal failure 15-30ml/min
-end-stage renal failure <15ml/min

25
Q

GFR filtered each day

A

-fluid filtered in capsular space
-males -180litres/day
-females-150litres/day
-99% reabsorbed into bloodstream [via peritubular cap and vasa recta]
-1-2 litres of urine/day [depends on hydration status and AHD secretion]

26
Q

mechanisms to regulate GFR

A

-renal autoregulation
-neural regulation
-hormonal regulation
[these use either adjustments in blood flow into glomerular cap or available surface area of glomerular cap]

27
Q

renal autoregulation

A

-kidneys can regulate volume of blood entering glomerulus
-to much blood increase GFR
-to little blood reduce GFR

28
Q

myogenic mechanism

A

-used in renal autoregulation
-uses changes to vascular tone of either afferent/efferent arteriole to maintain desired blood flow

29
Q

tubuloglomerular feedback mechanism

A

-used in renal autoregulation
-uses alteration to vasodilator nitric oxide
-macular densa cells detect increase in tubular fluid ion and water flow in kidney tubules
-act to inhibit release of nitric oxide from juxtaglomerular apparatus
-resultant lack of nitric oxide reduces vasodilation of afferent arteriole
-blood flow into glomerulus is reduced

30
Q

neural regulation of GFR

A

-sympathetic division of ANS acts of a-1 receptors in smooth muscle of afferent and efferent arterioles
-norepinephrine acts to increase vasoconstriction of these vessels
-afferent arterioles have more receptors and so higher activation means afferent constrict more
-this reduces GFR, reduces urine production but helps maintain blood volume and pressure

31
Q

hormonal regulation of GFR

A

-atrial natriuretic peptide [ANP]
-angiotensin 2

32
Q

atrial natriuretic peptide

A

-hormonal regulation of GFR
-ANP is secreted by cells in atria of heart when increased stretching is detected [indicative of high blood volume and pressure]
-ANP increased glomerular capillary surface area by relaxing glomerular mesangial cells
-this increased GFR

33
Q

angiotensin 2

A

-hormonal regulation of GFR
-produced in response to low blood volume and pressure
-increase concentration of Ang 2 will constrict both afferent and efferent arterioles
-this will decrease GFR [help maintain blood volume and pressure]

34
Q

glomerular disease

A

-usually caused by infection, autoimmune disorder or reaction to a drug
-many associated with inflammation of glomerulus
-very small slits are only just able to prevent blood albumin from passing through [major plasma protein and driver of normal blood osmotic pressure]
-if albumin is lost through damaged glomerular cap, blood will lose water and reduce in volume
-water collects in interstitial fluid causes oedema

35
Q

glomerulonephritis in children

A

-common after untreated streptococcal infection
-infection results in inflammation of glomeruli
-this increases size of filtration slits, allowing proteins such as albumin out of blood
-protein is lost in urine

36
Q

tubular reabsorption

A

-99% of filtrated will be reabsorbed through renal tubules and into peritubular cap and vasa recta
-once reabsorbed into peritubular cap, blood flows into interlobular veins and finally through renal vein

37
Q

proximal tubule reabsorption

A

-65% water [driven by osmosis, follow reabsorbed solutes across cell membranes, facilitated by water channels [aquaporins]]
-100% glucose and AA
-65% Na+ and K+ ions
-50% of Cl- ions
-80-90% of HCO3-
-50% of urea
-varying amounts of Ca2+, Mg2+ and HPO4^2-

38
Q

nephron loop reabsorption

A

osmolarity similar to proximal tubule, and osmolarity of tubular fluid increases through descending limb
-15% water
-20-30% Na+ and K+
-35% of Cl-
-10-20% of HCO3-
-variable amount of Ca2+, Mg2+

39
Q

distal tubule reabsorption

A

-divided into early and late sections
-early sections
-10-15% water
-5% Na+ ions
-5% Cl- ions
-Ca2+ reabsorption dependant of PTH [increases blood Ca2+ when required]

40
Q

cells in late section of distal tubule and collecting duct

A

-principle cells [reabsorb Na+ and K+]
-intercalated cells [secreted H+, secretes or reabsorbs HCO3-]

41
Q

collecting duct

A

-mainly active transport of Na+
-water reabsorption via aquaporins [inserted in response to ADH conc.]

42
Q

tubular secretion

A

-solutes can be actively secreted into tubular fluid to be excreted in urine [from blood and tubule cells]
-secretion achieved via passive diffusion driven by conc. gradients or active transport

43
Q

tubular secretion major solutes

A

-hydrogen ions H+
-potassium ions K+
-ammonium ions NH4+
-creatinine
-urea
-drug metabolites [often protein bound and too large to be filtered in glomerulus]

44
Q

location of tubular secretion

A

-PT is where majority of secretion takes place [urea, uric acid, creatinine, H+, NH4+
-little secretion occurs in nephron loop [urea in descending limb]
-secretion in DT/collecting duct fine tunes blood solute conc. [H+, NH4, K+]

biomed (9 decks)

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