Osmoregulation
regulation of water and solute balance of tissues and organs
excretion
removal of metabolic rates
- include CO2
- nitrogenous wastes produced as a result of deamiations of amino acids and nucleotide breakdown
water distributed between?
intracellular compartment
-extracellular compartment-tissue fluids
Important ions in osmolarity
sodium is the major cation in extracellular fluids
-chloride is major anion
Osmotic pressure
force of water moving into cell by osmosis
-measure of a solutions tendency to take in water by osmosis
tonicity
solute concentration of a solution
-solutions may be hypertonic, hypotonic, or isotonic
osmoconformers
- organisms that are in osmotic equilibrium with their environment (adjust tonicity to match their environment)
- only hagfish, sharks and relatives are isotonic
Osmoregulators
majority of organisms
-maintain a relatively constant blood osmolarity despite different concentrations in their environment
Freshwater vertebrates with osmolarity
hypertonic to environment
-adapted to prevent water from entering their bodies and to actively transport ions back into their bodies
Marine vertebrates and osmolarity
hypotonic to their environment
-adapted to retain water by drinking seawater and eliminating the exess ions through kidneys and gills
terrestrial vertebrates and osmolarity
- higher concentration of water than surrounding air
- tend to lose water by evaporation from skin and lungs
osmoregulatory organs in flatworms
use protonephridia which branch into bulblike flame cells
Earthworms
- use nephridia
- open both to the inside and outside of the body
Insects
-use mapighian tubules
Vertebrate kidneys
create a tubular fluid by filtering the blood under pressure through the glomerulus
- most of the water and molecules are reabsorbed into the blood
- waste products are eliminated from the body in the form of urine
nitrogenous wastes
made up of amino acids and nucleic acids
- first step is deamination
- combined with H+ to form ammonia
Urea
ammonia and other solutes that are released through urine
uric acid
only in mammals, from degradation of purines, not amino acids
Which organisms directly eliminate ammonia
fish through their gills
mammalian excretory system consists of
- 2 kidneys-filters blood; forms urine
- 2 ureters-connects kidneys to bladder
- 1 bladder-urine storage system
- 1 urethra-exit from body
where does the kidney get blood from
- each kidney receives blood from a renal artery
- blood flows to kidneys over and over again and is filtered many times per day
- kidney produces during from this blood
where does urine go from kidneys
drains from each kidney through a ureter into a urinary bladder for temporary storage
-urine is passed out of body through urethra by urination
where are the nephrons located
inner renal memdulla
nephrons consist of what?
glomerulus and tubular system
kidney is made up of what?
1 million function nephrons
steps of blood filtration
carried by an afferent artiole to the glomerulus
- filtered as it is forced through porous capillary walls of the glomerulus into the bowmans capsule to for the renal filtrate
- goes into proximal convoluted tubule
- moves down medulla and back up into cortex of loop of henle
- leaves henle, fluid is delivered to distal convoluted tubule in cortex
- drains into collecting duct
- merges w/other collecting ducts, emptys urine into pelvis
3 basic kidney functions
- filtration-between glomerulus and bowmans capsul (non selective)
- reabsorption-mostly proximal tubule
- selective movement of certain solutes out of the filtrate back into the blood via peritubular capillaries - secretion-mostly distal tubule
- selective movement of substances from the blood into the extracellular fluid, then into the filtrate in the tubular system
where is water reabsorbed in the kidneys
proximal convoluted tubule, descending loop of Henle, and collecting duct
what else do the kidneys reabsorb besides water
glucose and amino acids through active transport
proximal convoluted tubule
actively, selectively, reabsorbs virtually all nutrient molecules in the filtrate, and two thrids of the NaCl and water
loop of henle
- creates a gradient of increasing osmolarity from the ocortex of the medulla
- allows reabsorption of water from descending loop and collecting duct
ADH
antidiuretic hormone
- produced by the hypothalamus and secreted by the posterior pituitary gland
- stiumulated by an increase in the osmolarity of blood (dehydration)
- more ADH increases reabsorption of water
aldosterone
secreted by adrenal cortex
- stimulated by low levels of Na+ in blood
- causes reabsorption of of na+
- low levels of Na+ in blood are accompanied by a decrease in blood volume
ANH
atrial natriuretic hormone
- opposes the action of aldosterone in promoting salt and water retention
- promotes the excretion of salt and water in the urine and lowering blood volume