the urinary system Flashcards
function of the kidney
osmoregulation
filters the blood
removes waste such as urea, salt and water
function of the bladder
stores urine
function of the renal artery
carries the blood that needs to be filtered into the kidneys
originates from the aorta
function of the renal veins
carries clean filtered blood out of the kidneys
connects to the vena cava
function of the ureter
carries urine to the bladder for storage
function of the urethra
carries urine from the bladder out of the body
location of the kidneys
below the diaphragm
what is osmoregulation
-kidneys control the level of salt and water in the blood
-if we don’t drink enough water only a small volume of urine will be produced
-if we eat a lot of salty food a low volume of concentrated urine will be produced
renal artery
-aorta divides into two renal arteries when it reaches the kidneys
-one renal artery enters each kidney
-the blood blood is under very high pressure and needs to be filtered (it comes from the aorta)
-when the renal artery enters the kidney it splits up into smaller vessels called arterioles which then split into capillaries
renal vein
-emerges from both kidneys and connects to the vena cava
-the blood has been cleaned and filtered to remove excess salt, water and urea
-blood is under low pressure
the nephron
-each kidney contains millions of nephrons
-provide a huge surface area so that the blood can be filtered and urine removed efficiently
urine production
three parts to urine production in the nephron of the kidney
1. filtration
2. reabsorption
3. secretion
what is filtration
-blood enters the glomerulus (bunch of blood capillaries) which sit in the bowmans capsule
-blood is filled with waste and small substances pass out of the glomerulus and into the bowmans capsule
-it is based on size and any substance small enough will get passed out of the glomerulus
glomerular filtrate
vitamins and hormones that enter the bowmans capsule
how does filtration happen
-high blood pressure in the glomerulus
-the diameter of the efferent arteriole is much less than the diameter of the afferent arteriole
-glomerulus provides a large surface area
-the glomerulus capillaries are more porous than normal and only one cell thick
-the wall of the bowmans capsule is one cell thick
what are the large substances that do not get filtered into the bowmans capsule
red blood cells
platelets
antibodies
clotting proteins
what is reabsorption
-beyond the bowmans capsule water, most salts and useful substances are reabsorbed into the blood, about 99% of the glomerular filtrate is reabsorbed
-a combination of diffusion, osmosis and active transport
diffusion
movement of a substance from a high concentration to a low concentration
(passive process, no energy required)
osmosis
movement of water from a high concentrate of water to a low concentrate of water through a semi permeable membrane like a cell membrane or visking tube
(passive process, no energy required)
active transport
movement of a substance from a region of low concentration to a region of high concentration with the use of energy
reabsorption in the proximal convoluted tubule
-most of the water is reabsorbed by osmosis
-all of the useful molecules such as glucose, amino acids and vitamins are reabsorbed by diffusion and active transport
-most salts reabsorbed by active transport or diffusion
what helps the process of reabsorption in the proximal tubule
-is thin walled, only one cell thick
-is long (14mm)
-has numerous infoldings (microvilli) in its cells
-high concentration of mitochondria to provide energy for active transport
-surrounded by a blood capillary
reabsorption in the loop of henle (descending limp)
-permeable to water
-water is reabsorbed into the blood capillaries surrounding the nephron
-this happens by osmosis
reabsorption in the loop of henle (ascending limp)
-permeable to salts
-salts move out into the fluid of the medulla by diffusion
-at the top of the ascending limp salt is pumped out by active transport
-this increases the concentration of salt in the medulla causing osmosis to happen from the descending limp and collecting duct
what is the main function of the loop of henle
the reabsorption of water back into the blood
reabsorption in the distal convoluted tubule
-controls the water, salt and pH values of the blood
-some water and salt are reabsorbed into the blood in the dct
the collecting duct
-permeable to water
-small amount of water is reabsorbed from the filtrate
-occurs by osmosis due to high concentration of salt in the medulla
-the liquid that passes is called urine
-flows into the pelvis of the kidney and onto the bladder through the ureters
what is secretion
-when some substances pass from the blood into the nephron (opposite direction of reabsorption)
-secretion happens in the distal convoluted tubule
-potassium ions and hydrogen ions are passed from the blood into the dct
what is the main function of secretion and the distal convoluted tubule
keep the pH of the blood constant
how is urine volume controlled
-controlled by anti-diuretic hormone (vasopresin)
where is adh produced and stored
-produced by the hypothalamus
-stored in the pituitary gland
anti-diuretic hormone
-travels in blood from pituitary gland to the nephron
-makes the dct and collecting duct permeable to water
-controls osmoregulation
what happens if you drink a lot of water or have a low salt diet
-the hypothalamus in the brain detects the diluted blood and pituitary gland does not release adh
-dct and collecting duct become impermeable to water
-no water reabsorbed from dct or collecting duct
-large volume of urine is produced
-concentration of blood plasma does not change
