chapter 19: the urinary system physiology

6 main urinary system functions

excretion/elimination of wastes, maintenance of ion balance, regulation of blood volume and pressure, regulation of osmolarity, regulation of pH, production of hormones

what ions to the urinary system balance

Na+, K+, Ca2+

how does the urinary system regulate blood volume

by conserving or eliminating water

the secreting of enzyme renin begins what

cascade of hormonal regulation of blood pressure

basic how does the urinary system regulate pH

selectively excreting H+

the urinary system releases?

erythropoietin (EPO) that stimulates RBC production

the urinary excretion of a substance depends on?

its filtration, reabsorption, and secretion

4 main processes of the urinary system

glomerular filtration, tubular reabsorption, tubular secretion, excretion

glomerular filtration

a portion of the blood plasma is filtered into the kidney

tubular reabsorption

selective transport from tubule to peritubular capillaries, water and useful substances are reabsorbed into the blood

tubular secretion

selective transport from peritubular capillaries to tubule, wastes are removed from the blood and secreted into urinee

excretion

micturition of urine

excretion =

filtration rate + secretion - reabsorption rate

the filtration fraction

the percentage of total plasma volume that filters in the glomerulus

only __% of the plasma that passes through the glomerulus is filtered?

20%

less than __% of filtered fluid is eventually excreted?

1

glomerulus is

the primary filtering device of the nephron

step 1 of the glomerulus

blood is transported into the bowman’s capsule from the afferent arteriole

step 2 of the glomerulus

within the capsule, the blood is filtered through the glomerulus and then passess out via the efferent arterioles

step 3 of the glomerulus

filtrate is passed out of the bowman’s capsule into the proximal convoluted tubule

filtration definition

the force of the blood pressure pushes the water and dissolved material from the blood out into bowman’s capsule

pressure is generated by these 3 things

differences in arteriole diameters, pressure exerted by filtrate, presence of proteins

filtrate definition

the fluid pushed out consists of everything except blood cells and large proteins

in the renal corpuscle, where is the filtrate contained?

the capsular space

podocytes have processes called __?

pedicels

materials pasing out of the blood at the glomerulus must be small enough to pass between ___?

filtration slits between the pedicels

filtration barriers have how many layers?

3

what are the 3 filtration barriers

fenestrated epithelium, basement membrane, podocytes

filtration barrier: fenestrated epithelium

fenestrations block blood cells, negatively charged glycocalyx blocks most proteins

filtration barrier: basement membrane

negatively charged

filtration barrier: podocytes

create alterable filtration slits, respond to glomerular mesangial cells

reabsorption definition

the process of moving substances from the filtrate back into the blood

reabsorbed substances pass through what to reach the blood?

tubule cells and the capillary endothelium

secretion definition

moving substances from the blood and putting them into the filtrate

secreted substances pass through what in order to reach the filtrate?

capillary endothelium and tubule cells

how much of Na+ is excreted

around 1%

how much of Cl- is excreted

around 1%

how much of K+ is excreted

depends on intake, if high up to 150% of filtered load excreted

how much of Ca2+ is excreted

around 1%

how much of glucose is excreted

0% (unless saturation)

how much of urea is excreted

30-50%

PAH is used to measure what

measure renal flow

high filtration rate helps what and requires us to what?

helps eliminate unwanted molecules, requires us to regulate reabsorption of desirable molecules

reabsorption involves both __?

transepithelial transport and paracellular pathway

transepithelial transport

moves solutes across the plasma membrane

paracellular pathway

paracellular transport moves solutes between cells

how does Na+ transport drive reabsorption

some of Na+ movement is passive so across cell membrane down concentration gradient, which doesn’t require energy

Na+ symporters help reabsorb materials from the tubular filtrate, those are

glucose, amino acids, ions, water soluble vitamins

most nutrients such as __ and __ are completely reabsorbed in the first half of the proximal convoluted tubule

glucose and amino acids

small peptides are reabsorbed by __?

endocytosis

most plasma proteins stay in the blood but some smaller peptides can pass through the filtration barrier: t/f

true

enter PCT cells by __ and are digested by __

endocytosis, lysosomes

amino acids are transported back in to the blood during?

reabsorption

only __ amounts of proteins appear in the urine

trace amounts

water is only reabsorbed by what

osmosis

obligatory water reabsorption occurs when __?

water is obliged to follow the solutes being reabsorbed

water reabsorption also occurs in collecting duct under the control of what hormone?

antidiuretic hormone (ADH)

in the absence of __ water, is not absorbed in the CD

ADH

renal transport can not reach saturation: t/f

false, it can

reabsorption may be limited by __

carrier proteins

any solute >/< renal threshold remains in filtrate

>

what % of volume is filtered and less than what % of fluid is reabsorbed

20% and 19%

in the glomerulus, the diameter of the efferent arteriole is smaller/bigger than the afferent arteriole

smaller

the efferent arteriole offers considerable resistance so high/low pressure is needed to force blood into it?

high pressures

symporter

membrane protein

passive movement of substances across a cell membrane down their concentration gradient does/does not require energy

does not

glycosuria is type 1 or type 2 diabetes

2

secretion enhances excretion of what molecules

H+, K+, and organic molecules (metabolic waste products and xenobiotics)

xenobiotics

substances brought into the body

secretion requires membrane transport proteins that requires __?

requires ATP

are membrane transport proteins an active or passive process?

active because it requires moving substances against their concentration gradients

nitrogenous wastes removed by the kidneys are

urea, uric acid, creatinine,

course of urea being produced

proteins → amino acids → NH2 removed → forms ammonia → liver converts to urea

uric acid

nucleic acid catabolism

creatinine is formed from what

parts of amino acids, creatine phosphate catabolism

renal failure is when

nitrogenous wastes are in the blood

uremia

toxic effects as wastes accululate

kidney function is evaluated based on

glomerular filtration rate, renal handling

renal handling is

rate of filtration; is the solute reabsorbed, secreted, both, or neither?

clearance rate definition

the rate at which solute disappears from the body by excretion

glomerular filtration rate

amount of filtrate formed in all renal corpuscles of both kidneys per minute

average glomerular filtration rate for male and female

male: 125 mL/min

female: 105 mL/min

homeostasis requires what that is constant?

glomerular filtration rate

what happens to the glomerular filtration rate when homeostasis is too high?

useful substances are lots due to the speed of fluid passage through the nephron

what happens to the glomerular filtration rate when homeostasis is too low?

sufficient waste products may not be removed from the body

the distal convoluted tubule folds around and is next to the afferent/efferent arteriole?

afferent arteriole

granular cells secrete ___?

renin

renin is an enzyme involved in ___?

salt and water balance

juxtaglomerular complex helps?

regulate blood pressure and filtrate formation

parts of the juxtaglomerular apparatus

macula densa, juxtaglomerular cells (granular cells), mesangial cells

macula densa functions as

chemoreceptors

macula densa send what signals

paracrine signals to afferent arteriole causing constriction

macula densa is made of

epithelial cells of DCT, near renal corpuscle

juxtaglomerular cells (granular cells) are made of

smooth muscle cells in walls of afferent arteriole

juxtaglomerular cells (granular cells) function as

baroreceptors and secrete renin

when blood pressure is high/low, juxtaglomerular cells release their __?

low, renin

mesangial cells are located where

between afferent and efferent arterioles

mesangial cells alter __?

surface area of filtration slits

renin is an enzyme that

cleaves the plasma protein angiotensinogen into angiotensin I

angiotensinogen is made where

the liver