Osmoregulation and Excretion Flashcards
What is a nephron?
the functional unit of a kidney that consists of the Bowman’s capsule, and tubule.
From where does blood enter the glomerulus?
the afferent arteriole
From where does blood exit the glomerulus?
the efferent arteriole
What is the function of the glomerulus?
to bring blood containing water and solutes to the Bowman’s capsule to be filtered
What is the Bowman’s capsule?
the glomerular surrounding the glomerulus that removes filtrate from the blood
Why does the Glomerular Filtration Rate matter?
restricting it preserves blood volume when neccessary
How is the Glomerular Filtration Rate regulated?
constriction of the afferent artery reduces the net filtration pressure, decreasing the GFR
Which solutes are filtered into nephrons?
essential ions, glucose, amino acids, smaller proteins and waste
What is the proximal tubule and its function?
the primary site of water and solute reabsorption where Na+ is removed via active transport and water follows because of the osmotic gradient
What is the loop of Henle?
A loop consisting of an ascending and descending limb that facilitates reabsorption
What is the function of the descending limb?
to release H2O from the filtrate via an osmotic gradient creating a concentrated filtrate
What is the function of the ascending limb?
it is impermeable to H2O and facilitates active an passive transport of NaCl in the interstitial fluid
What is the purpose of a hyper osmotic interstitial fluid surrounding the medulla?
to facilitate osmosis in the descending limb
What is the purpose of the final segment of the nephrons tubule, the distal tube and collecting duct?
hormonal control of electrolytes and urine volume
What is aldosterone?
a hormone secreted by adrenal glands which activate Na+/K+ pumps
What is the function of Na+/K+ pumps?
reabsorb Na+ and secrete K+ to regulate the osmotic gradient
What is the function Anti-Diuretic Hormone (ADH)?
to activate aquaporin vesicles in the collecting duct to perform water reabsorption
What is ADH secretion controlled by?
the hypothalamus
Where does aldosterone come from?
the adrenal glands activated by ADH
What are excretory adaptations?
adaptation of nephrons for osmoregulation in extreme environments
Why is a long loop of Henle adaptive?
it produces more concentrated urine limiting the need for water
What is the purpose of osmoregulation?
to maintain a water and solute homeostasis because too much of either one would cause cells to expand or dehydrate
What is anhydrobiosis and what is an example?
A state of dormancy preventing desiccation/dehydration
tardigrades
How are solutes prepared for excretion?
the body metabolizes nucleic acids and proteins into ammonia groups to convert into nitrogenous waste
In what form do fish excrete nitrogenous waste and why?
as ammonia because no conversion is required due to the water surrounding them that dilutes it
In what form do mammals excrete nitrogenous waste and why?
Urea; it is less toxic and they have occasional access to water; however, it requires conversion in the liver
In what form do birds, reptiles, insects, and land snails excrete nitrogenous waste and why?
Uric acidit is nontoxic and they have minimal access to water; however requires a lot of energy to produce
What is the first step of the excretory system?
filtration; when water and solutes enter the system from the bloodstream
What is the second step of the excretory system?
reabsorption; valuable substances are reabsorbed into the blood stream
What is the third step of the excretory system?
secretion, excess or toxic substances are secretion from the bloodstream into the filtrate
What is the fourth step of the excretory system?
excretion; the filtration (urine) is excreted from the body
How does the digestive tract of an annelid work?
cilia draw water into collecting tubules of the metanephridra and then, waste it is excreted from external pores
How does the digestive tract of an arthropod work?
components connected to the digestive tracts known as malpighian tubules reabsorb most solutes and water so no filtration is required
