Chapter 25 - urinary system Flashcards by Sonam Sehdev

3 supportive tissues that surround each kidney (superficial to deep )

renal fascia- dense fibrous connective tissue that anchors kidneys and adrenal gland to surrounding structures
Perineal fat capsule- fatty mass to provide cushion
fibrous capsule- transparent. prevents infections from invading

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superficial region of the kidney

renal cortex

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the renal medulla has a pointy side called pyramid - why do they look stripped?

pyramid is formed of parallel bundles of tubules and capilliaries

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the inward tissue extensions inside kidneys separates medullary lobes

renal columns

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this part of the kidney is continuous with the ureter

also, forms branching extensions called?

Renal pevlis which forms 2-3 major calyces which divides to form minor calyces - this cup shaped area encloses papillae

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when renal arteries approach kidneys what does it divide into?

5 segmental arteries

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Segmental arteries branch off to form what? and where in the kidneys do they branch

interlobar arteries

they branch at the renal pelvis

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interlobar arteries branch at the cortex-medulla junxtion , into?

arcurate arteries that arch over the base of medullary pyramids

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after interloblar what is the remaining path way of arteries?

coritcal radiate arteries –> afferent arterioles –> into glomerulus capillaries –> efferent.a

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which blood vessels are associated with nephrons?

affterent.a glomerulus capillaries, efferent.a and peritunular capillaries or vasa recta

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2 main parts of nephrons and their location

renal corpuscles- in cortex

renal tubule - start at cortex pass into medulla, and move back up to cortex

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the glomerulus in renal corpuscles is a yarn of capillaries- explain its properties

fenstrated, so very porous allowing solute rich/ protein free fluid to pass from blood into the capsule

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filtrate is made in which part?

renal corpuscles

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2 layers of the glomerular capsule are parietal, visceral and. explain parietal

external- parietal layer - simple squamous epithelium does not play any part in forming filtrate

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explain visceral layer of the glomerular capsule

visceral layer- clings to capillaries, had has modified epi called podocytes which have foot processes that cling to the basement membrane of the glomerulus. in between are the filtration slits where filtrate enters the capsule space

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name the 3 major parts of the renal tubule

proximal convoluted tubule, nephron loop, distal “ “

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explain the walls proximal convoluted (PCT)?

cuboidal epithelial cells with lots of mitochondria
apical surface has dense microvilli which increase surface area and capacity for reabsorbing water and solutes FROM the filtrate and secreting substances into it

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Explain the DCT properities

thinner cuboidal cells and confined to cortex, lack microvilli

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explain the 2 types of cells in the collecting ducts

principal cells- more. short microvilli, responsible for maintaining water and sodium balance.
intercalated cells- are cubiodal with lots of microvilli
2 types of these cells A/ B for acid base balance

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explain the 2 types of nephrons

cortical- majority
juxtramedullary nephrones- play an important role in the kidneys’ ability to make urine that is concentrated (conserves water)

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this type of capillary bed reclaims most of the filtrate

peritubular capillaries and vasa recta

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this type of capillary bed makes filtrate

glomerulus

which part drains the glomerulus capillary?

efferent arterioles

how is high pressure maintained in the glomerulus capilliaries?

from the affterent.a feeding blood and the efferent.a draining it

where do the efferent. a feed into?

vasa recta or peritubular capillaries

this part of the nephron has low pressure, come from a type of arteriole, empty contents into near by venules and they are porous therefore they easily absorb solutes and water

Peritubular capillaries

bundles of long vessels in the juxtamedullary nephrons play a role in concentration of urine

vasa recta

Where in the nephrons is the juxtamedullary complex?

most distal portion of ascending limb lies against afferent arteriole - here both these are modified

what 3 cells are part of the juxtaglomerular complex?

macula densa, granular cells, extraglomerular mesangial cells

tall cells in ascending limb - these are chemoreceptors that monitor NaCl content of filtrate that enters the distal convoluted tubules

macula densa

in the arteriol walls, these cells are big smooth muscle cells with granules that have enzymes (which enzyme?) what cells are these and what is their function?

renin these are granular cells of the JGC and they act as mechanoreceptors that sense blood pressure in the afferent arterioles

name the 3 processes that make urine, and adjust the composition of blood

1. glomerular filtration 2. tubular reabsorption 3. tubular secretion

where does filtration take place?

glomerular filtration

a passive process where hydrostatic pressures force fluids and solutes through a membrane

Glomerular filtration

the filtration membrane of the glomerulus capillaries separates it from the filtrate in the capsule, it has a porous membrane to move in water, solutes and smaller proteins passively. Explain the 3 layers of this membrane

1. fenestrated endothelium of the G.capillaries - allowing components of blood EXCEPT for blood cells to pass 2. Basement membrane- is in the middle, and forms a physical barrier to block all BUT small proteins 3. foot processes of podocytes of the G.capsule

how is colloid osmotic pressure maintained?

by the plasma proteins staying in the capillaries

What type of pressure promotes formation of filtrate?

OUTWARD ! ( hydrostatic pressure IN glomerular capillaries )

Explain Hydrostatic pressure in the glomerular capillaries

- this is the main force that pushes water and solutes from blood and across filtration memb. because the BP in glomerulus is high (55mmHg) because of the high resistance efferent.a having a small diameter than the afferent.a

What type of pressure inhibits the formation of filtrate?

INWARDS - 2types : Hydrostatic pressure in the capsular space, and colloid osmotic pressure in glomerular capillaries

What is hydrostatic pressure in the capsular space?

this is the pressure exterted BY filtrate IN the g.capsule. this pressure is generally higher compared to other capillaries because filitrate is confined in a small space with narrow outlet (15mmHg)

What is Colloid osmotic pressure in the glomerular capillaries?

this is the pressure exerted BY the proteins in the blood that SUCK water into the capillary (30mmHg)

What is the formula for NFP?

net filtration pressure = (HP gc) - (HPcs + OPgc)

What is GFR?

Glomerular filtration rate- is the volume of filtrate formed every minute

3 things GFR is DIRECTLY proportional to

- NFP - Total surface area available for filtration - Filtration membrane permeability

If their is an increase in GFR what follows?

increased urine out put -> which reduces blood volume and pressure

When do extrinsic controls take over intrinstic controls in the regulation of glomerular filtration?

When mean arterial pressure is less than 80 mmHg or greater than 180mmHg

What happens if glomerular hydrostatic pressure rises?

NFP rises and so does GFR

What are the 2 types of autoregulation mechanisms?

myogenic and tubuloglomerular feedback

how to kidneys maintain a constant GFR despite changes in systemic arterials?

Intrisic controls

Explain myogenic mechanism

intrinsic control that regulates glomerular filtration - vascular smooth muscle contracts when stretched and relaxes when not being stretched. increase in systemic BP -> causes afferent.a to constrict -> this then restrict blood flow into the glomerulus and keeps the GFR and keeps it at a functional level

Explain tubuloglomerular feedback mechanism

dependent on flow and is directed by the macula densa cells in the JGC . When GFR increases there isn't enough time for reabsorption therefore the concentration of salts remains high in the filtrate - the macula respond to the high salt concentrations in the filtrate by releasing vasoconstrictor chemicals (atp) that cause constriction of afferent.a --> reduces BF into glomerulus which then decreases NFP and GFR- this slow down of filtrate allows more time for filtrate processing (reabsorption of salts)

Extrinsic controls - maintain systemic BP | explain how the sympathetic nervous system comes into play

if BP falls =, norepinephrine released by sympatheric nerve fibers and epinephrine from adrenal medulla --> cause vasucular smooth muscles to constrict which increases perihpheral resistance and brings BP back up to normal so the afferent.a also constrict which then decreases GFR to help restore the Blood volume and pressure syetmically

Renin-angiotensis-aldosterone is used to increase BP. Low BP causes which cells of the juxtagloerumarl complex to relase renin?

Granular cells

Explain the 3 pathways of renin-angiotensin-aldostrone

1. SNS- barorecepto reflex, renal nerve fibers activate and cause release of granular cells which release renin 2. Activated macula densa cells- low BP or vasoconstriction of afferent.a by SNS reduce