excretory system Flashcards
kidneys
- excretes waste
- maintains homeostasis or body fluid volume and solute composition
- regulates blood pressure
macula densa
monitors filtrate pressure in kidney tubules
if low blood pressure –>
- adrenal cortex is signaled to synthesize aldosterone
- more water is reabsorbed from the kidney back into blood
- blood pressure increases/normalizes
nephron
functional unit of the kidney
glomerulus
a capillary network that interacts with the Bowman’s capsule
afferent arteriole
brings blood into glomerulus
filtered blood
efferent arteriole
out of glomerulus
unfiltered blood
Bowman’s capsule
a structure that surrounds the glomerulus
- materials are forced out of blood and into the tubule
podocytes
cells in Bowman’s capsule that filters blood
proximal convoluted tubule
- a portion between Bowman’s capsule and the loop of Henle
- substances are reabsorbed from the filtrate back into the blood
- most reabsorption occurs
- lots of mitochondria present
Loop of Henle
consists of descending and ascending loops
descending loop
- permeable to only water
- water leaves the kidney tubules, which increases the solute concentration in the tube
ascending loop
- impermeable to water
- NaCl gets removed, which decreases the solute concentration in the tube
distal convoluted tubule
more reabsorption of glucose, ions, and water
collecting duct
- collects remaining filtrate
- hormones can act on it to affect secretion and reabsorption
aldosterone
increases Na+ reabsorption from the kidney tubules into the bloodstream –> water follows Na+ out of the kidney and back into the blood –> water retention in blood is increased
ADH
- increases collecting duct permeability to water –> water is reabsorbed out of kidney tubule and back into the bloodstream –> urine becomes more concentrated while blood pressure increases
- alcohol and coffee block synthesis of ADH, leading to more dilute urine flow
marine fish
- body cells are hypotonic to environment
- this means water loss occurs
- they constantly drink water and rarely urinate to offset water loss
freshwater fish
- body cells are hypertonic to environment
- this means water enters
- rarely drink water
- constantly urinate to stop body fluid from being diluted
filtration
large particles (blood cells and albumin) remain in circulatory system; only small particles go through and form the filtrate, which is pushed into Bowman’s capsule
reabsorption
glucose is completely reabsorbed; after passing through the components of the nephron, molecules and ions are pulled back into blood from kidney
secretion
substances are removed and secreted from the blood through peritubular capillaries into the nephron
excretion
urine physically leaves the body
