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36 terms

Excretion

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Excretory systems
eliminate nitrogenous wastes; osmoregulation; include filtration, reabsorption, secretion, and elimination
Osmoregulation
regulation of solute concentration and water balance by a cell or organism
Forms of nitrogenous waste
ammonia, urea, uric acid
Ammonia
a small, very toxic molecule (NH3) produced by nitrogen fixation or as a metabolic waste product of protein and nucleic acid metabolism
Urea
a soluble nitrogenous waste produced in the liver by a metabolic cycle that combines ammonia with carbon dioxide
Uric acid
a product of protein and purine metabolism and the major nitrogenous waste product of insects, land snails, and many reptiles; this is relatively nontoxic and largely insoluble
Filtration
in excretory systems, the extraction of water and small solutes, including metabolic wastes, from teh body fluid; nonselective; blood pressure in afferent arterioles forces material into Bowman's capsule
Reabsorption
in excretory system, teh recovery of solutes and water from filtrate
Secretion
teh discharge of wastes from teh body fluid into the filtrate
Protonephridia
(simple tubes) an excretory system, such as the flame bulb system of flatworms, consisting of a network of closed tubules and lacking internal openings
Metanephridia
(tubes + capillaries) an excretory organ found in many invertebrates taht typically consists of tubules connecting ciliated internal openings to external openings
Filtrate
cell-free fluid extracted from teh body fulid by the excretory system
Bowman's capsule
a cup-shaped receptacle in teh vertebrate kidney that is the initial, expanded segment of the nephron where filtrate enters from the blood
Glomerulus
a ball of capillaries surrounded by Bowmans capsule in teh nephron and serving as the site of filtration in vertebrate kidney
Renal cortex
the outer portion of the vertebrate kidney
Renal medulla
the inner portion of the vertebrate kidney, beneath the renal cortex
Nephron
the tubular excretory unit of the vertebrate kidney
Proximal convoluted tubule
in the vertebrate kidney, the portion of a nephron immediately downstream from Bowman's capsule that conveys and helps refine filtrate; reabsorption of materials (from tubules into intertitial fluid and capillaries, water follows by osmosis); secretion of materials (especially for adjusting pH)
Loop of Henle
the hairpin turn, with a descending and ascending limb, between the proximal and distal tubules of the vertebrate kidney; functions in water and salt reabsorption
Distal convoluted tubule
in the vertebrate kidney, the portion of a nephron that helps refine filtrate and empties its into a collecting duct; regulate Na+, K+, Cl-; regulate pH (H+, bicarbonate); urine relatively dilute
Collecting duct
the location in the kidney where processed filtrate, called urine, is collected from teh renal tubules; NaCl reabsorbed; water reabsorbed by osmosis (hyperosmotic interstitial fluid); urea becomes more concentrated (most is excreted, some is reabsorbed from lower permeable tubule)
Renal pelvis
funnel-shaped chamber that receives processed filtrate from teh vertebrate kidney's collecting ducts and is drained by the ureter
Loop of Henle: descending limb
impermeable to NaCl; permeable to water >>> water is reabsorbed by osmosis
Loop of Henle: ascending limb
permeable to NaCl (thin segment - Nacl diffuses out; thick segment - NaCl actively pumped out); impermeable to water >>> reabsorption of NaCl
Interstitial fluid osmotic gradient
increasingly concentrated from cortex deeper into medulla; important for water reabsorption (water moves by osmosis from tubuel into interstitial fluid and capillaries)
Cortical nephron
in mammals and birds, a nephron with a loop of Henle located almost entirely in the renal cortex
Juxtamedullary nephron
in mammals and birds, a nephron with a loop of Henle that extends far into the renal medulla
Afferent arteriole
in the kidney, the blood vessel supplying a nephron
Regulation of kidney function affects
blood pressure, blood volume, blood osmolarity
Renin
release of renin stimulated by low blood pressure, low blood volume; angiotensinogen -----(renin)---> angiotensinogen II
Renin-angiotensin II-aldosterone system (RAAS)
a hormone cascade pathway that helps regulate blood pressure and blood volume
Juxtaglomerular apparatus
a specialized tissue in nephrons that releases teh enzyme renin in response to a drop in blood pressure or volume
Angiotensin II
a peptide hormone that stimulates constriction of precapillary arterioles and increases reabsorption of NaCl and water by the proximal tubules of the kidney, increasing blood pressure and volume; stimulates the release of aldosterone from the adrenal gland
Aldosterone
a steroid hormone that acts on tubules of the kidney to regulate teh transport of sodium ions and potassium ions; increases NaCl reabsorption and water reabsorption
Antidiuretic hormone
a peptide hormone, also knowns as vaspressing, that promotes water retention by the kidneys; prodcued in teh hypothaliamus and released from teh posterior pituitary, ADH also has activities in teh brain; released if blood osmolarity > 300mosm; increases water permeabllity of distal convoluted tubules and collecting ducts; alcohol inhibits release of ADH
Atrial natriuretic peptide
a peptide hormone secreted by cells of the atria of the heart in response to high blood pressure; ANP's effects on the kindey alter ion and water movement and thereby reduce blood pressure; stifles aldosterone, renin release and NaCl reabsorption