Function of the Urinary System, Formation and Flow of Urine

renal threshold

the kidney hasabsorbed as much as it can so excess substances secrete into the urine

micturition

act of urination

oliguria

decreased urination (< 400 mLs/day)

anuria

no urination (usually due to an obstruction)

dysuria

painful/difficult urination

nocturia

increased urination at night

polyuria

increased urination due to something other than the kidneys (> 3000 mLs/day)

diuresis

increased urination due to something being wrong with the kidneys (> 3000 mLs/day)

isosthenuria

when the kidney loses the ability to concentrate the urine (stays at a specific gravity of 1.010)

normla specific gravity of urine

1.001-1.035

isohydruria

when the kidneys lose the ability to adjust the pH of the urine (causes crystals)

osmolality

the number of particles in a fluid and how the water moves to where more particles are to balance it out

hypertonicity

increased particle concentration

hypotonicity

decreased particle concentration (diluted)

functions of the urinary system

1. regulate BV, BP, and stabilize ion conc

2. recycles materials/nutrients

3. maintains acid/base balance (aka homeostasis)

4. removes waste

5. secretes or is affected by hormones (erythropoietin, renin, ADH)

6. regulates absorption of Ca ions

what are the two hormones the kidney is responsible for releasing

erythropoietin and renin

when the kidney releases erythropoietin what happens

more RBCs are made (conttrols RBC formation rate)

what makes the kdiney release erythropoietin

the kidneys sense when O₂ is low causing cells in the kidney to release it

when the kidney releases renin what happens

renin activates the RAAS system which creates aldosterone, aldosterone tells the kidneys to retain sodium (and water follows)

what makes the kidneys release renin

when blood pressure in low (body will retain sodium and water and excrete out potassium)

RAAS system

kidney (renin) → liver (angiotensinogen) → liver angiotensinogen I) → liver angiotensingogen II) → adrenal cortex (aldosterone)

what hormone has a direct effect on the kidney’s function

ADH (antidiuretic hormone or vasopressin)

when ADH is released what happens

it regulates the amount of water in the body (tells the kidneys to absorb more water)

ADH is made by the

posterior pituitary gland

when is ADH released by the posterior pitutary gland

when blood pressure in low (body will retain sodium and water and excrete out potassium)

when blood pressure is high, what happens to sodium, water, and potassium

sodium and water get excreted

potassium is retained

main three structures of the kidney

renal cortext (outer)

renal medulla (inner)

renal pelvis (hollow funnel shapes)

funtion of a nephron

functional unit of the kidney (1 million in each kidney)

what parts make of a nephron

renal corpuscle, renal tubules, collecting ducts, and renal pelvis

how does the renal corpuscle in a nephron work

the glomerulus is a ball of tangled capillaries with a pore that has potocytes around, they layer of cells that surround the diaphragm

the glomerular flows through the diaphragm via hydrostatic pressure where it reaches the glomerular capsule (Bowman’s capsule) wheich then leads to the renal tubules where reabsorption occurs (your GF)

what is the role of mesangial cells in the nephron

phagocytes, they keep stuff from going into the glomerular filtrate (GF)

the glomerular capsule is also known as

bowman’s capsule

afferent and efferent arterioles function in the kidneys

deliver oxygenated blood to the glomerulaus

after entering the glomerular capsule, where the GF go

the renal tubules

what happens to GF when it reaches the renal tubules

GR enters the proximal convoluted tubule where most absorption takes place

substances we don’t need continue on to the loop of henley where water is absorbed in the descending and electrolytes are absorbed in the ascending

after exiting, GF enter the distal convoluted tubules and at this point the liquid is very concentrated and will enter the collecting ducts

what hapens to the GF after it enter the collecting ducts

the fluids collects here along with the unabsorbed particles and is transferred to the renal pelvis

what happens to the GF in the renal pelvis

the liquid from the collecting duct drains here

regulates the speed/timing of when the fluid can go to the ureter then bladder

aldosterone comes from the

adrenal cortex

what happens to GF when it reaches the ureters

the GF is now urine and is carried from the kidney to the bladder

what happens to urine once it leaves the ureters

it enters the bladder where it’s held until the urine is ready to be expelled

once the urine is in the bladder and ready to be expelled what happens next

the urine is carried to the urethra through a muscular tube

once the urine is carried through the urethra what happens next

it is expelled through the urinary meatus (an external opening)

what are the three stages of urinary formation

filtration, reabsorption, and secretion

what happens in the filtration stage in the formation of urine

fluids and dissolved substances are forced through the glomerulus via hydrostatic pressure creating the GF

what happens in the reabsorption stage in the formation of urine

substances that the body needs are absorbed in the renal tubule system while unwanted/excess substances remain in the urine

what happens in the excretion stage in the formation of urine

substances are transferred from the peritubular capillaries into the renal tubules and are eliminated from the body as urine

what does urine contain

95% water

urea, uric acid, and ammonia

creatinine and other waste products (electrolytes, ions)

how much blood is passing through the kidneys per minute in a healthy adult and what percent of blood is it

1,200 mL/min

25%

what is the normal rate of glomerular filtration

120-125 mL/min

normal output of urine per day for a healthy adult

avg: 1,200-1,500 mL/day

wide range: 800-2,000 mL/day