U2L7: The excretory system Flashcards
What are the functions of the excretory system?
They excrete metabolic wastes, maintain salt-water balance, maintain acid-base balance, and secrete hormones.
What is osmoregulation?
It is the process of keeping water and solute concentration inside and outside of cells in balance.
Explain the function of the kidneys
Blood comes IN to kidney through renal artery and wastes are filtered by kidneys. Then, clean blood EXITS kidney through renal vein.
What is the renal artery?
It is a vessel that delivers oxygenated blood to the kidneys. The Renal Artery splits into capillaries (the glomerulus) within the Bowman’s capsule of the nephron.
What is the Renal Vein?
It’s a blood vessel that removes deoxygenated blood, water, and solutes back to the body.
Explain the three main parts of kidney anatomy
Outer layer = renal cortex
Inner layer (below cortex) = medulla
Renal pelvis = cavity connecting kidney to ureter through which urine passes to bladder
What is a Nephron?
Its the basic functional unit of the kidney - they are tiny microscopic structures with blood vessels. The nephrons filter out substances from the blood, transforming it into urine.
What does the Bowman’s Capsule do?
The Bowman’s Capsule (at the top of each nephron) acts as the filtration structure. Within each capsule, the renal artery splits into a network of capillaries called the glomerulus.
What does the glomerulus do?
The glomerulus acts as a filtration device – water, small molecules, ions, and urea pass further in the nephron.
Explain the Tubules & Ducts
The filtrate (fluid) continues through the tubules which reabsorb nutrients like glucose. The tubules empty into a collecting duct which reclaims as much water as possible. The filtrate left over in the duct is now called urine.
Explain urine formation (see saw motion)
As the brain monitors blood content, some materials are secreted into the tubules (becoming urine) and some materials are absorbed back into the blood. The secretion and absorption go back and forth until the solute content in the blood is the perfect level.
What is Filtration?
occurs as body fluids move from the blood into the Bowman’s Capsule.
What is Reabsorption?
pushing materials from the tubules of the nephron back into the blood to reabsorb nutrients.
What is secretion?
pushing materials from the blood into the tubules of the nephron to become urine.
What does hypoosmotic mean?
water moves from urine into body fluids —-> In mammals, urine is hypoosmotic to surrounding body fluids.
What happens during filtration in the Glomerulus & Bowman’s Capsule?
Blood pressure forces water and dissolved substances through the pores of the glomerular walls
What occurs in the Proximal Tubule?
it reabsorbs nutrients like glucose, amino acids, sodium, potassium, calcium, and vitamins. Reabsorb’s water through osmosis.
What happens moving down the Descending Loop of Henle?
water moves back to blood via osmosis
What happens moving up the ascending Loop of Henle?
salt passes back to blood (Na+ and Cl- ions)
What happens in the Distal Tubule?
It reabsorbs sodium, water (osmosis), and negative ions. Secretes hydrogen and potassium
What does the collecting tube do?
reabsorb water (osmosis).
What’s Left in Urine?
Water, Urea, Cl-, Na+, K+, H+; The balance of salt-water is determined by ADH (antidiuretic hormone) secreted by pituitary
What happens when theres a decrease in ADH?
It occurs when the body needs more solute. Less ADH means more urine will be produced and excreted from the body.
What happens when theres a increase in ADH?
It occurs when the body needs more water. ADH is released to bloodstream which allows for greater reuptake of water in the collecting tube.
What are diuretics?
promote dehydration - like alcohol & caffein. They block the release of ADH (which signals kidneys to hold on to water). This increases the volume of urine released by your body and can have a dehydrating effect.
Explain the steps involved in blood filtration & urine formation
1) Blood flows from the efferent and afferent arterioles into the glomerulus.
2) Blood pressure forces water and dissolved substances into the bowman’s capsule.
3) The glomerular filtration creates a plasma like blood filtrate that passively passes the h2o, amino acids, glucose, some urea and ions into the proximal convoluted tubule.
4) As the filtrate passes through the proximal convoluted tubule, ions (na, cl, k), hco3, glucose, amino acids are reabsorbed into the extracellular fluid (blood) via active transport. The filtrate is then hypotonic (low solute C), which causes water to passively flow out of the tubule into the blood as well.
5) the filtrate goes through the descending loop of henle (@ the medulla) which promotes water and ions (na, cl) to reabsorb back into the blood passively via osmosis, and increases the (C) of ions in the tubule.
6) As the filtrate goes through the ascending loop of henle, the [c] of na and cl are high in the tubule, so they move out via passive transport but as it approaches the top of the ascending loop (@cortex), they move out via active transport.
7) As the filtrate approaches the Distal convoluted Tubule, more ions (na, cl, hco3) move out (reabsorb into blood) via active transport. This causes water to passively move out. K and H ions enter the tubule via active transport and are regulated by hormones at this stage.
8) Once filtrate reaches the collecting tube, remaining water (and some urea) is reabsorbed into blood via passive transport.
9) remaining fluid in tubule goes to renal pelvis and into bladder.
