nephrons and osmoregulation

general steps of nephron filtration

1. filtration: small solutes and water exit glomerular capillaries into bowman’s capsule

2. reabsorption: water is reabsorbed into blood

3. secretion: ions (Na and Cl) actively transported out

4. excretion: water is transported out via aquaporins, tubule fluid goes to ureters

Micturition pathway

Go: parasympathetic branch, bladder walls contract, internal urethral sphincter relaxes

Hold: somatic branch, external urethral sphincter contracts

Dont go: sympathetic branch, bladder walls relax, internal urethral sphincter contracts

counter-current multiplier

opposing directions of flow of tubular fluid and blood to power filtration

sodium-potassium pump/ATPases

use ATP for active transport for Na+ out and K+ in, mostly in thick ascending limb and collecting duct

aquaporins

facilitate the osmosis of water, coupled with transport of other ions, in thick limb, DCT, and collecting duct

nitrogenous wastes

ammonia (common in aquatic animals), urea (abundant in mammals), uric acid (common in birds, reptiles, insects)

Amino acids as nitrogenous waste

broken down proteins → AA → release amine group reacts

nitrogenous bases as waste

broken down nucliec acids → nitrogenous bases → amine groups react

diuretics

chemicals lessen water retention, clear fluid from the body, common in alcohol (ethanol) and coffee (caffine)

antidiuretic hormone (ADH)

produced in hypothalamus and stored in posterior pituitary gland, ADH moderates urine volume and how much water is retained in the body

high concentration of ADH

permeability of collecting duct for water increases (more aquaporin engagement), more reabsorption, low urine volume

low concentration of ADH

permeability of collecting duct decreases, less reabsorption, high urine volume

anatomy of renal system

kidneys → ureters → bladder → urethra

functions of renal system

1. osmoregulation: balance of water and ion/metabolites

2. maintain blood and plasma volumes

3. remove toxins

4. producing peripheral hormones/enzymes

   1. Erythropoietin

   2. Renin

Erythropoietin

aids in production of new erythrocytes

renin

aids with renin-angiotensin-aldosterone system/blood pressure

blood to kidneys by

renal artery and outgoing blood leaves through renal vein

kidney stones

calcifications inside the kidneys, made up of calcium, cystine, struvite, uric acid

calcium

high levels of oxalate or calcium in blood

cystine

rare, forms due to genetic condition limiting the bodies ability to break down cystine

struvite

associated with UTI’s

uric acid

high protein diet and other medical conditions