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regulates solute concentrations and balances the gain/loss of water
gets rid of nitrogenous metabolites and other waste products
the solute concentration of a solution
Hyperosmotic vs. Hypoosmotic
- Hyper- higher solute concentration
- hypo- lower solute concentration
3 types of nitrogenous wastes
4 key functions of excretory systems
- filtration - filtering of body fluids
- reabsorption - reclaiming valuable solutes
- secretion - adding nonessential solutes and wastes from the body fluids to the filtrate
- excretion - processed filtrate containing nitrogenous wastes released from the body
Overview of excretory process
blood comes in, gets filtered (filtration), uptake what you need actively (reabsorption), dump things that were not filtered but you want to get rid of (secretion), then get rid of waste from body (excretion)
The two types of nephrons
- cortical- reach only a short distance into the medulla
- juxtamedullary- goes deep into the renal medulla
What is the advantage of the juxtamedullary nephron?
key feature in preserving water and not losing too much
Structure of the kidney
- renal cortex- top layer
- renal medulla- inner layer
____ produces urine, ______ brings urine to _______, which stores urine temporarily, ______ leads urine to the outside
- urinary bladder
What does the glomerulus (bowman’s capsule) do?
What does the filtrate contain?
salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules
What happens in the proximal tube?
- reabsorption of water and nutrients
- toxic materials are actively secreted into the filtrate
What happens in the descending limb of the loop of henle?
- as filtrate flows, solutes become more concentrated due to water leaving the tubules by osmosis
- water is flows out of the filtrate to be in equilibrium with the environment
What happens in the ascending limb of the loop of henle?
- salt, but not water is able to defuse from the tubule into the interstitial fluid
- so the filtrate becomes more dilute as it travels back up
- NaCl is first pumped out passively, then actively
What happens in the distal tube?
- regulates K+ and NaCl concentrations of body fluids
- controlled movement of ions contributes to pH regulation
What happens in the collecting duct?
- carries filtrate through the medulla to the renal pelis
- water is lost again because environment becomes more concentrated the further down you go
If body has a shorter collecting duct, urine would be
more diluted because it cannot go through the gradient all the way
How is osmolarity controlled?
- osmolarity increases
- hypothalamus senses that
- posterior pituitary secretes hormone ADH, which travels to collecting duct
- makes you drink more water and increases ability of collecting duct to reclaim water as it passes through gradient
What does Antidiuretic Hormone do?
- makes the collecting duct epithelium more permeable to water
- helps conserve water
Malfunctioning of the ADH-aquaporin system results in
What is diabetes insipidus
any abnormal condition characterized by the secretion and excretion of excessive amounts of urine
Mutation in ADH production causes
severe hydration and results in diabetes insipidus
When is the Renin-Angiotensin-Aldosteron System used?
when you don’t have a lot of blood or have a high concentration of solutes
Describe the Renin-Angiotensin-Aldosteron System (RAAS)
- Normal blood pressure/volume
- Blood pressure/volume drops (injury, blood loss, dehydration)
- A part in the nephron called juxtaglomerular apparatus (JGA), senses that you don’t have enough blood
- Triggers a response, produces renin (because of drop in pressure or blood volume)
- Renin meets angiotensinogen (produced by the liver, does nothing by itself)
- Renin + Angiotensinogen = Angiotensinogen 1
- Angiotensinogen 1 taken by enzyme ACE, produces Angiotensinogen 2
- Angiotensinogen 2 signals adrenal gland to produce aldosterone to increase blood volume
- More Na+ and H2O are reabsorbed in distal tubes, increasing blood volume
- Also tells arterioles to constrict, because low blood volume = lower pressure, so arterioles constrict to keep pressure up
What is the role of Angiotensinogen 2?
- signals adrenal gland to produce aldosterone to increase blood volume
- tells arterioles to constrict in order to keep the pressure up
Why are some patients treated with ACE inhibitors?
- because they have hypertension
- by killing Angiotensinogen 2, blood pressure is decreases because less arterioles will be constricting
What happens when kidneys don’t filter? (3)
- poor regulation of solutes in blood
- compromised fluid balance
- accumulation of toxic waste
What are aquaporins?
Channels in the membrane that allow water to pass through easily
how does ADH affect aquaporins?
ADH increases the number of aquaporin proteins in the membrane of collecting duct cells
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