3. How is urine formed?
Answers
Answer:
The kidneys filter unwanted substances from the blood and produce urine to excrete them. There are three main steps of urine formation: glomerular filtration, reabsorption, and secretion. These processes ensure that only waste and excess water are removed from the body.
Answer:
urine formation occours in kidney
Explanation:
Urine Formation
Urine Formation – by filtering the blood the nephrons perform the following functions
(1) regulate concentration of solutes in blood plasma; this also regulates pH
(2) regulate water concentrations; this helps regulate blood pressure
(3) removes metabolic wastes and excess substances
Urine Formation:
Glomerular Filtration – water and solutes are forced through the capillary walls of the glomerulus into the Bowman’s capsule (glomerular capsule)
Filtrate – the fluid that is filtered out into bowman’s capsule
Glomerular Filtration Rate is regulated by mechanisms:
Autoregulation – the smooth muscle in the afferent arteriole responds to blood pressure changes by constricting and dilating to regulate filtration rate.
Sympathetic control – causes afferent arterioles to constrict or dilate when activated by a nerve impulse (fight or flight response to keep blood pressure up)
Renin-angiotensin mechanism – triggered by the juxtaglomerular apparatus; when filtration rate decreases, the enzyme renin is released. Renin converts a plasma protein called angiotensinogen into angiotensin I. Angiotensin I is quickly converted into angiotensin II by another enzyme. Angiotensin II causes 3 changes:
(1) Constriction of the arterioles – decreases urine formation and water loss
(2) Stimulates the adrenal cortex to release aldosterone – promotes water reabsorption by causing the absorption of salt
(3) Stimulates the posterior pituitary to release ADH – antidiuretic hormone – promotes water reabsorption
(4) Stimulates the thirst and water intake (hypothalamus says we’re thirsty so we get a drink)