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55 Cards in this Set
- Front
- Back
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invertebrate excretion
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- protonephridia
- metanephridia - malphigian tubules |
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protonephridium
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- network of dead-end tubules lacking internal openings
- lumen has low hydrostatic pressure compared to outside - in animals with one fluid space - consist of a flame bulb |
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flame bulb
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- cilia draws fluid in
- really low pressure - interstitial fluid filters through membrane where cap cell and tubule cell interdigitate |
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metanephridia
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- each segment of an earthwork has pair of open-ended metanephridia
- in animals with 2 major fluid spaces = coelom and circulatory fluid - have filtering capsule followed by tubules that perform selective secretion and reabsorption - tubules collect coelomic fluid and produce dilute urine for excretion - capillaries surrond tubules - have openings to the outside - unable to concentrate urine |
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malphigian tubules
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- in insects and other terrestrial arthropods
- remove nitrogenous wastes from hemolymph - function in osmoregulation - hindgut is as important as malphigian tubules in urine formation - insects, mammals, and birds can produce urine that is hyperosmotic to their blood plasma - no blood vessels around it - fluid bathes it - junction between midgut and hindgut |
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malphigian tubules functionality
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- blind ended structures that arise at the junction of midgut and hindgut
- project into hemocoeal and bathed in hemolymph - active transport of H+ by a H+ ATPase pump creates electrochemical gradient that drives transport of K+ by secondary active transport - secretion of K+ causes the transport of Cl- - transport of KCl drives osmotic entry of water into tubule - tubule secretions remain isosmotic to blood - additional solutes enter tubules passively - organic compounds may be actively transported |
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tubular epithelium
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- may reabsorb salts and water
- cuticle - continuous with integumentary cuticle |
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hindgut
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- lined with cuticle
- reabsorbs most of the KCl, Na+, and water - modulates urine volume and composition - may secrete H+ from the hemolymph into hindgut |
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ion concentration in urine
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- animals lowered [ion] in urine in water fed locusts
- animals raised [ion] in urine in saline fed locusts |
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crayfish
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- has 2 renal organs called antennal or green glands
- gets rid of waste through a system |
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antennal gland
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- begins with capsule/end sac that filters hemolymph
- then a labyrinth of epithelia and fluid spaces - followed by coiled nephridial canal were selective absorption and secretion takes place - finally empty into a bladder - water content decreases throughout - osmotic pressures stays constant until it reaches the bladder where it begins to drop |
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3 common features of the kidney
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- tubular elements that discharge directly or indirectly to the outside
- all produce and eliminate aqueous solutions derived from blood plasma or other extracellular body fluids - function is to regulate the composition and volume of blood plasma and other extracellular body fluids by controlled excretion of solutes and water |
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amphibians and freshwater teleost
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- have large number of nephrons with well developed golmeruli
- high rate of filtration - form primary urine by ultrafiltration - no loop of Henle - use intermediate segment in place of loop of Henle - Bowman's capsule move stuff out of capillary into space = filtration - urine really dilute |
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amphibian and freshwater teleost reabsorption
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- obligatory reabsorption
- proximal convoluted tubule actively reabsorbs NaCl returning it to the blood plasma - glucose and amino acids are also actively absorbed - in distal convoluted tubule water and solutes are differentially returned to blood - accomplished by altering permeability of epithelium by varying levels of ADH |
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obligatory reabsorption
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- not controlled by hormones
- presence of specific carrier in membrane that bind to ions and bring them in |
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marine teleost
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- no loop of Henle or distal convoluted tubule
- lost water and gail salt - produce small amounts of dilute urine - hyperosmotic to their seawater environment - face continuous dessication - few nephrons and small glomeruli - low filtration rate - form primary urine by secretion = active transport into PCT - secrete Na+, Cl-, Mg++, SO4 -- |
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birds
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- make urine hyposmotic to blood plasma
- mammalian type nephrons - loops of Henle organized into parallel arrays or medullary cones |
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non-avian reptiles
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- nephrons structurally similar to amphibian nephrons
- no loop of Henle - contain intermediate segment |
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functions of the kidney
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- maintain water balance in body
- regulate the quantity and concentration of most of the extracellular fluid ions including Na, Cl, HCO, Ca, Mg, SO4, PO4, H - maintain proper acid base balance by adjusting Cl and HCO3 - produce and secrete hormones erythropoaten and renin - excrete foreign compounds and end products of metabolism such as urea, uric acid, creatine - convert vitamin D to its active form |
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nitrogenous waste
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- requires lots of processing and enzymatic breakdown
- nitrogen contained in protein and nucleic acids - proteins are 16% nitrogen and consumed at high levels by carnivores - require most processing than other macromolecules - aquatic animals excrete in form of ammonia - reptiles, birds, insects, and land snails excrete in form of uric acid - mammals, most amphibians, sharks, some bony fish excrete in form of urea |
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ammonia
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- highly toxic
- need access to lots of water - least soluble - release it across the whole body surface or through the gills - result from simple damination of proteins - cheapest because no ATP required - NH3 (ammonia) is converted to NH4+ (ammonium) in tissues |
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urea
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- produced by cartilaginous fish
- accumulate it as major osmolyte - liver of mammals and most adult amphibians converts ammonia to less toxic urea - produced by two ammonium ions and a bicarbonate ion using ATP - carried to kidneys, concentrated and excreted with minimal loss of water - toxic because it binds to proteins and destabilizes their structure therefore changing function |
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urea in ruminants
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- enter the rumen via saliva
- microbes convert it back to ammonia - use the ammonia as their nitrogen source |
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ornithine urea cycle
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- used to synthesize urea from protein degradation
- set of enzyme catalyzed reactions - early vertebrates had ability to synthesis all enzymes - groups that don't use pathway are thought to have experienced a deletion of one or more genes in pathway or are not expressed - mitochondria, cytoplasm event - converts two amino groups |
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synthesis of urea by urea cycle
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- five reactions = two mitochondria and three cytosolic
- converts NH3+ - converts Asp - converts a carbon atom from HCO3- - cost of 4 "high energy" phosphate bonds = 3 ATP hydrolyzed to 2 ADP and one AMP - ornithine is carrier to carbon and nitrogen atoms |
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3 functions of urea production
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- reduces water requirement of nitrogen excretion
- adjusts blood osmotic pressure = sharks and rays - detoxification of nitrogen waste during periods of water stress |
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bullfrogs
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- shift from ammonotelism to ureotelism as they undergo metamorphosis
- enzymes required for urea synthesis increase in activity as metamorphosis occurs - urea excretion consequently increases as well |
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uric acid
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- largely insoluble in water
- can be secreted as paste with little water loss - can accumulate in body indefinitely - end product of amino acid and purine metabolism - requires more ATP than urea to produce - removes 4 nitrogens per molecule - produced by vertebrates in small amounts as by-product of catabolism of nucleic acids - in peroxisomes - secreted and reabsorbed by kidneys |
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uric acid in cells
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- 100x higher in cells than out
- when cells are damaged it is released - enhances ability of dendritic cells to present antigens |
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URAT1
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- is localized to apical membrane of renal proximal tubular cells
- mediates reabsorption of uric acid - in salivary gland - in vascular smooth muscle cells |
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creatine
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- produced by cataolism of creatine phosphate in skeletal muscle
- less toxic than ammonia - less abundant than urea - chiefly filtered out of blood by kidneys = glomerular filtration and proximal tubular secretion - little or no tubular reabsorption - all that's produced is released |
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mammalian urinary system
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- kidney form urine
- remainder of the system is a set of ducts that carries urine to outside of body |
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distinct regions of mammalian kidney
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- outer renal cortex = gives color
- inner renal medulla - renal pyramide = collecting tubules - renal pelvis - ureter - major and minor calyx - medullary ray - papilla - hilum |
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hilum
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- nerves, blood vessels, and lymphatics enter
- ureter exits |
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nephron
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- made of glomerulus in Bowman's capsule
- functional unit of kidney - counter current exchange |
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2 types of nephrons
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- nephron with outer cortical capsule
- nephron with juxtamedullary capsule |
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cortical nephrons
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- short loop
- peritubular capillaries - no vesa recta - doesn't reach inner zone of medulla - glomeruli in outer layer of cortex - most abundant |
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juxtamedullary nephrons
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- long loop
- peritubular capillaries - vesa recta - glomeruli lie in inner layer of cortex |
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counter current exchange
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- ascending and descending loop of Henle
- vasa recta and loop of Henle - peritubular capillaries and tubules |
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arterioles
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- afferent and efferent
- contain smooth muscle - vasoconstriction and vasodilation - change pressure going into glomerulus |
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afferent arteriole
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- branch of renal artery that subdivides into capillaries of glomerulus
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efferent arteriole
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- formed by capillaries converge as they leave glomerulus
- break into second set of capillaries that surround convoluted tubules and loop of Henle - peritubular capillaries = fenestrated - vasa recta |
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vasa recta
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- straight run parallel to loop of Henle in medulla
- fenestrated capillary |
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renal corpuscle
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- filtration
- fenestrated capillary - glomerulus and Bowman's capsule - visceral layer of Bowman's capsule sit on capillaries to provide structural support - podocytes in visceral layer have slits - simple squamous epithelium |
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regions of nephron
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- filtrate passes through
- proximal convoluted tubule - loop of Henle - distal convoluted tubule - fluid from several nephrons flow into a collecting duct |
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proximal convoluted tubule
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- large surface area
- helps to reabsorb ions - isn't hormone controlled = obligatory reabsorption - lots of mitochondria - lots of transport that requires energy |
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structure of proximal convoluted tubule
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- cubodial cells
- lots of mitochondria - apical surface have abundant microvilli constituting brush border = stereo cilia - mitochondria and basal - associated basilar infoldings of cell membrane penetrate deeply among neighboring cells |
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4 segments of loop of Henle
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- descending limb
- thin ascending limb - medullary thick ascending limb - cortical thick ascending |
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descending limb
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- thick section in outer zone of medulla
- thin section in inner zone of medulla - low permeability to ions and urea - highly permeable to water - sharp bend in renal medulla going from descending to ascending limb |
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ascending limb
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- thin section not permeable to water but is permeable to ions
- thick medullary limb within outer zone of medulla - cortical thick limb within outer and inner zone of medulla - ends at macula densa adjacent to parent glomerulus |
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collecting ducts
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- fewer mitochondria
- cubodial cells - ends process for humans - rest on basement membrane - hypertonic region of kidney |
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distal convoluted tubules
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- hormone regulated reabsorption
- reabsorption and secretion - lacks huge surface area - cubodial cells - lots of mitochondria - partly responsible for regulation of K+, Na+. Ca++, and pH - primary site for kidney's hormone based regulation of calcium |
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mammals and other vertebrates that inhabit freshwater
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- lack long loops of Henle
- only have short loops - no inner medulla - very limited ability to concentrate urine |
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papilla
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- where all collecting ducts come together
- where the medullary pyramids empty urine into minor calyx - composed largely of long loops of Henle - evolutionary differences in animal species - poorly developed in freshwater species - more evident in species that live in moist environments - best developed in species that live in arid environments |
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relative medullary thickness (RMT)
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- provides measure of length of longest loops of Henle
- relative medullary thickness accounts for differences in body size - high RMT = long loops of Henle relative to other kidney functions - high RMT allows more ability to concentrate waste - relationship between RMT and body size depends on environment of mammal |
