Physiology of Renal System

3 fxns kidneys

filtration
regulation of fluids
production hormones

aldosterone effects (full)

increased NaCl + H2O reabsorption, increased K+ + H+ secretion

metabolic waste products

urea, creatinine, uric acid, bi

regulation of water controls _________ of fluids

osmolality

changes in water excretion controlled by

ADH

ADH is produced in _______ and released by _________

hypothalamus
post pituitary

role of ADH

conserves water in body

effects of Na+ accumulation

raises extracell fluid volume -> triggers hormonal changes + other signals to increase Na+ excretion

kidneys play role in regulation of arterial pressure by which 2 ways?

long-term - excreting Na+ and H20
short-term - hormones + vasoactive factors -> renin + PGs

what do kidneys do when BP high

decrease blood v -> reduced H20 absorption -> dilute urine

what do kidneys do when BP low

renin constricts vessels -> increasing H20 reabsorption -> concentrated urine

3 ways kidneys regulate acid-base balance

excrete h+ + sulfuric + phosphoric acid
conserve bicarb
regulate fluid buffer stores

kidneys secrete ______ which stimulates RBCs by stem cells in BM, under stimulus of ____-

EPO
hypoxia

low blood v, anemia, low hb, poor bloodflow and pul disease decrease what

oxygenation

calcitriol

active form vit d, produced by kidneys by UV rays

calcitriol works w/ _______ to raise Ca+2 levels in bloodstream

PTH

what happens when Ca2+ levels drop?

parathyroid releases PTH -> calcitriol -> absorption Ca2+ from food + stimulates osteoclasts

low bp, blood loss and dehydration stimulates what

RAAS

renin -> angiotensinogen from _____ -> angiotensin I -> angiotensin II -> ______ from adrenal cortex -> reabsorption of _________ -> increased blood v -> increased BP

liver
aldosterone
H20 + Na+

what turns off RAAS

neg feedback from increased blood p

kidneys contributions to glucose homeostasis

gluconeogenesis
uptake glucose from circ
reabsorption glucose @ prox tubule

renin release of glucose into circ is the result of

glycogenolysis and gluconeogenesis

kidneys extend from which spinal levels

T12 -> L3

medial surfaces of kidneys contain

renal sinus, where hilum is located (a, v, ureter, lymph vessels, n)

each kidney is encased in

renal capsule (fibrous) and surrounded by adipose tissue layer

2 regions of kidney

outer red/brown granulated - cortex
inner striated - medulla

cortex consists of

glomeruli, convoluted ducts, cortical collecting ducts

medulla contains

loops of Henle, medullary collecting ducts, medullary blood vessels

each kidney is organized into 8-10

lobes (pyramidal medullary tissue surrounded by cortical tissue)

tip of medullary pyramid forms ___ which drains urine into _________ to form major calyx -> renal pelvis

renal papilla
minor calyx

nephron consists of

renal corpuscle (w glomerulus)
renal tubule

renal corpuscle of nephron has 3 components

glomerulus (vasc part), mesangium, Bowman's capsule + space

glomerular filtration barrier

leaky endothelial-capsular membrane of renal corpuscle that filters water + substances from blood to nephron

where does ultrafiltrate pass

from glomerular capillary blood into Bowman's space thru glomerular filtration barrier

layers of glomerular capillary membrane

glycocalyx - w/ neg charged glycosaminoglycans
capillary (endothelium)
BM
podocytes (epithelial cells)

what prevents leakage of big - charged macromolecules due to its - charged glycosaminoglycans

glycocalyx

capillary endothelium of glomerulus is perforated by

fenestrae

function of fenestrae

provide no restriction to water + solute movement out of capillary

hinder plasma proteins by - charges

BM of glomerular filtration barrier is made of

lamina rara interna, densa and externa

__________ is a meshwork of collagen + proteoglycan (- charged) fibrillae with large spaces thru which water + solutes filter

BM (of glomerular filtration barrier)

podocytes

epithelial cells with extensions that end in foot processes, resting on outer layer of BM

slit diaphragms of podocytes

thin diaphragmatic structures that connect interdigitations, w/ pores

in the glomerular filtration barrier, the extracell domains of _____ and ______ from podocytes zip together to form slit diaphragms

nephrin + NEPH1 (integral membrane proteins)

genetic defects in integral membrane proteins of glomerular filtration barrier leads to

nephrotic syndrome

proximal renal tubule is divided into

convoluted + straight

loop of Henle is made of

proximal straight tubule, thin limb (ascending + descending) and thick ascending limb

cells lining proximal convoluted tubule

deep infoldings w/ mitochondria, abundant microvilli

cells of proximal straight tubule, thin descending limb and thin ascending limb VS proximal convoluted tubule

cells are less complex + flatter progressively

cells of thin vs thick ascending limb

thick ascending limb are taller and more complex

connective tubule types of cells

connecting-tubule cells which secrete kalikrein, intercalated cells rich in mitochondriac

collecting tubule cells

principal cells
intercalated cells (# progressively decreases)

several nephrons drain into cortical collecting duct which pass into _____

outer medullary collecting duct

in inner medulla, inner medullary collecting ducts unite to form

large papillary ducts

renal cortex has 2 types of nephrons

superficial nephrons - short loops extending to medulla
juxtamedullary nephrons - produce concentrated urine w/ long loops extending to tip of medulla

how do juxtamedullary nephrons differ

longer loops of Henle, different tubular permeability, diff types of post-glomerular blood supply, produce concentrated urine

why is the high blood flow of kidneys needed

for high glomerular filtration rate (NOT high metabolic needs)

why is renal venous blood rich in O2 (bright red)

they only extract small amount O2 from blood, receive much more than they require

each kidney is supplied by which artery

a single renal artery (from aorta)

how do the renal arteries divide

ant + post branches -> 5 segmental arteries -> interlobar arteries (passing bw lobes) -> arcuate arteries (@ medulla - cortex jxn) -> radial arteries -> afferent arteriole -> glomerulus -> efferent arteriole -> peritubular capillaries

medullar blood supply originates from?

efferent arterioles of juxtamedullary glomeruli

efferent arterioles of juxtamedullary glomeruli generate 2 types of capillaries:

peritubular capillaries
vasa recta

vasa recta

straight long capillaries, forming ascending and descending vasa recta grouped into vasc bundles -> facilitates exchange substances bw blood flowing in/out of medulla

the 2 capillary beds of renal circulation

glomerular cap
peritubular cap

hydrostatic pressure of kidneys

by glomerular + peritubular capillaries, changes rate of glomerular filtration + tubular reabsorption in response to homeostatic demands

hydrostatic pressures of glomerular vs peritubular capillaries

glomerular - high (filtration)
peritubular - low (reabsorption)

where do peritubular capillaries empty

vessels of venous system

kidneys have rich _______ innervation

sympathetic

stimulation of sympathetic fibers of kidney induce which effects?

constriction of renal blood vessels -> increases vascular resistance -> reduces flow

increase Na+ tubular reabsorption + renin secretion

kidney function is regulated by

hormones + sympathetic innervation

urinary excretion rate is due to

(glomerular) filtration rate - (tubular) reabsorption rate + (tubular) secretion rate

_________ involves ultrafiltration of plasma in glomerulus -> ______ urine

glomerular filtration
primary

GFR glomerular filtration rate is ______/day

180L

ultrafiltrate collects in _________ and then flows downstream thru ________

Bowman's capsule
tubular lumen

tubular secretion

transport of substances into tubular urine

types of tubular transport

active or passive

movement of creatinine thru nephron

freely filtered but not reabsorbed

movement of Na+ and Cl- ions thru nephron

freely filtered but partly reabsorbed

movement of glucose thru nephron

freely filtered but not excreted (fully reabsorbed)

movement of organic acids and bases thru nephron

freely filtered and not reabsorbed, secreted from peritubular capillary blood -> renal tubules

movement of urine through ureters through which acts?

peristaltic contractions of smooth m fibers in ureter walls + gravity

peristaltic contractions are enhanced by which stimulation?

parasympathetic

what prevents urine backflow

ureterovesical valves

parts of urinary bladder

body
neck (-> urethra)

fused smooth m of bladder

detrusor muscle

trigone of post wall of bladder

lower is opening of post urethra
upper is 2 ureters

urogenital diaphragm consists of

1 layer external sphincter m

bladder filling requires which situations

low intravesical p (compliance), closed bladder outlet, absence of contractionsb

bladder emptying requires

coordinated contractions of bladder
lowering of resistance of sphincters
absence of obstruction

micturition reflex

sensory signals from bladder stretch receptors -> sacral pelvic n -> back to bladder thru parasymp fibers

pudendal nerves inhibit external sphincter

centers of brain for micturition reflex

facilitative and inhibitory centers in pons
inhibitory (some excitatory) in cortex

glomerular filtration barrier allows and restricts which substances

allows - small molecules
restricts - plasma proteins + cell elements

what is special about Ca+ and fatty acid filtration thru glomerular barrier?

not freely filtered even tho they're small molecules - bound to plasma proteins

filtration of molecules through glomerular barrier depends on

size, shape, deformability and electrical charge

molecular size of ______ kDa are freely filterable thru glomerulus

10

filterability defines grade of ultrafiltration comparing it to

water (= 1.)

which shape of molecule will pass more easily through glomerulus

long + slender (high deformability)

glomerular BM contains negatively charged ___-

sialic acids, sialoproteins, heparin

why does albuminuria occur

loss of neg charges of glomerular filtration barrier

hallmark of glomerular disease

proteinuria

glomerular filtration rate (GFR)

flow rate of filtered fluid through kidney glomerular barrier, depending on balance bw hydrostatic + colloid osmotic pressures across glomerular filtration barrier