urinary system

functions

excretion and hormone /enzyme production

hormones of the kidney

Renin: Regulate blood pressure

EPO: To make red blood cells

parts of the kidney(2)

renal cortex and renal medulla

Renal medulla

inner portion is made of renal pyramids and renal columns

Renal papilla

Drain urine from the pyramid into the renal sinus

renal sinus

Collect urine

functional unit of the kidney

Nephrons

Number of nephrons in each kidney

1 million

Renal capsule- glomerulus function

Filtration of the blood to extract toxins

formed elements can't pass through here

entrance to glomerlus

afferent arteriole

Renal tubule parts

PCT- Proximal convoluted tubule

Loop of Henle

Distal convoluted tubule

collecting duct

merging of many collecting tubules that drain urine

collecting tubule

drain filtrate from several nephrons and enter the medulla

Vasa recta

surrounds the regions of the renal tubule in the medulla

JG apparatus

group of receptor cells that maintain the nephrons' rate of filtration

granular cells

Mechanoreceptors of the JG apparatus that constrict if too much pressure is felt

Macula densa cells

chemoreceptors that detect salt concentration

Filtration membrane

fine filter wall that plasma must pass through to get to the glomerular capsule

Urine formation steps

glomerular filtration, tubular reabsorption, tubular secretion

glomerular filtration

plasma and solutes (valuable and waste) leak from theglomerulus into the capsular space, forming filtrate

Net Filtration Pressure (NFP)

10 mmHg

Intrinsic regulation

maintain GFR through myogenic control and Tubuloglomerular control

myogenic control of Glomerular filtration

Any rise in pressure stretches the afferent arteriole

Granular cells trigger vasoconstriction

Tubuglomerular control

A decrease in GFR causes a decrease in filtrate NaCl levels.

Macula densa cells then trigger vasodilation.

Extrinsic regulation of glomerular filtration

Neural control and hormonal control

Neural control

Sympathetic nervous system constricts afferent arterioles to reduce GFR

ANP (atrial natriuretic peptide)

Stretching of atrial walls triggers release

Dilates afferent arteriole to elevate GFR

Tubular reabsorption

Valuable solutes are transported from the filtrate back to the plasma of the peritubular capillaries

Nitrogenous waste is not reabsorbed

Na+ ions

are pumped out of tubule cells, creating a gradient

gradient use

Ions use the gradient to leave the filtrate through symport carriers that pump amino acids, glucose and other nutrients

Transport maximum

Limited activity of set number of carriers

Additional solutes beyond end up in urine

PCT reabsorption

Reabsorbs all the glucose and amino acids

Reabsorbs 65% of ions and water

Loop of henle reabsorption

Continues ion and water reabsorption(25%)

DCT reabsorbtion

Allows limited water and ion reabsorption

Regulated by hormones

Aldosterone

increases Na+ and water reabsorption

ADH

increases water reabsorption

PTH

increases Ca2+ reabsorption

Tubular secretion

Additional wastes are added to the filtrate from the plasma of the tubular capillaries

The filtrate is now changed to urine

Regulation of urine concentration

More water reabsorbed = more concentrated urine

Osmolarity

Amount of solute dissolved in one kg of water

Counter current mecnaism

interaction between two adjacent tubules whose content flows in opposite directions direction

descending(thin) limb

is permeable to water but not salt

ascending(thick) limb

is permeable to salts but not water

positive feedback mechanism

establishes osmolarity

Absence of ADH

The collecting duct is less permeable to water

Urine stays more dilute

presence of ADH

Collecting ducts become more permeable to water which leaks out of the filtrate

Forms more concentrated urine

Diuretics

Increase urinary output

Inhibit ADH secretion or adoim reabsorption

color of urine

Clear to yellow

Because of presence of urochrome, a pigment from the breakdown of bilirubin

Ph of urine

slightly acidic

Urine

95% water

5% solute

solutes of urine

urea, uric acid, creatinine

urea

from the breakdown of amino acids

Uric acid

from the breakdown of nucleic acid

Creatinine

from the breakdown of creatine phosphate

Ureters

Paired tubes to transport urine from the kidneys to the urinary bladder

Urinary bladders

Stores urine

Trigone

Triangular region outlined by 2 ureters and 1 urethra

Area of UTI

Urethra

Tubes that drain urine

longer in males leads to less UTI

Micturition reflex steps

200 ml of urine stretches the bladder, causing the relaxation of the urethral sphincter

Relaxation can allow micturition

After an additional 200 ml of urine is collected, the reflex restarts