Excretory systems Flashcards
what are the four major functions of excretory systems and what are the four organ systems that can serve this role
1) maintenance of proper internal levels of inorganic solutes e.g. Na+, K+, Cl-,H+ ect
2) Maintenance of proper plasma water volume
3) removal of non-nutritive and harmful substances
4) Maintenance of osmotic balance
systems
1) Respiratory= regulate co2, gills can also remove ammonia
2) Digestive = remove undigested food , intestinal tract epithelia regulate ions
3) Integument and glands = sweat, inorganic ions
4) renal organs/kidney = filter body fluid and regulate water, ions and organic substances
Discuss the usefulness and evolutionary patterns of ammonia, urea and uric acid as nitrogenous wastes
A result of breakdown of proteins to amino acids, excess amino acids –> ATP+Co2+H2O + ammonia which is toxic and can alter PH by binding to H+, interfers with Na+/K+ transporters = neurotransmitters disrupted
1) Ammonia = most toxix, excreted by aquatic organisms as their is enough water to dilute to non-toxic, least energy required to form
2) Urea = mammals and some amphibians, less toxic than ammonia but requires less water to decrease toxicity at a cots of more ATP/metabolic energy to convert ammonia to urea
3) Uric acid= insects and bords, the end product of aminoacidic and purine, requires the least amount of water (50-100 times less) to produce but needs to most metabolic energy to produce
Describe a vertebrate nephron and the major roles of the capsule + glomerulus, proximal, distal tubules, loop of Henle and collecting duct
a nephron is the functional unit of the kidney and is found in the millions in humans. their arrangement gives two distinct regions; the cortex and medulla
capsule/glomerulus = double walled cup-shaped invagination called bowmans capusle which collects fluid filtered from capillaries (filtrate) resulting in protein free filtrate
Proximate tubule= found in the cortex, substances of value in filtrate e.g. glucose, amino acids, water is reabsorbed into the peritubular capillaries
Loop of Henle= u-shaped loop that dips into medulla, the descending limb is permeable to water and impermeable to ions so water reabsorbed, ascending limb impermeable to water and permeable to ions so NaCl reabsorbed = counter current exchange
distal tubule/collecting duct= found in cortex, selective reabsorption
collecting duct = DT empties into collecting duct which drains fluids contents into ureters
compare the excretory process of marine elasmobranchs, marine bony fish, fresh water bony fish
Elasmobranchs = slightly hyperosmotic to sea water and retain urea and TMAO as major osmolytes, therefore face the problem of excess NaCl entering gills. Their nephrons only have glomeruli, PT and DT and external organs do do most of the excretion roles
Mainre fish = highly hypoosmotic to seawater so have constant influx of excess salt and loss of water through the gills, the gills are responsible for what they kidneys usually do. nephrons only have glomeruli and PT
fresh water fish = hyperosmotic, nephrons with large glomeruli, PT, DT and collecting duct
how do cortical and juxtamedullary nephrons differ
Two types of nephron based on their structure and location in the kidney
1) cortical = found in the outer region of the coretx with the hair pin bend of the loop of henle reaching the outer part of the medulla
2) Juxtamedullary= found in the inner region of the cortex with the hairpin bend of the loop of henle plunging into the inner part of the medulla
Describe the three layers of glomerular membrane and their roles in the filtration process and the roles of mesangial cells and podocytes
1) Glomerular capillary wall - flattened endothelial cells perforated by fenestrations making it more permeable to water and solutes than other capillaries but too small for plasma proteins to fit
2) basement membrane - noncellular gelatinous layer composed of collagen (provides structure_ and glycoproteins sandwiches between glomerulus and Bowmans capsule. Glycoprotein negative charge respells any albumin and plasma proteins which may have got through first layer
3) inner layer of Bowmans capsule- consists of podocytes which encircle the glomerular tuft. Each podocyte has elongated foot process of adjacent podocytes which interdigiate, the narrow filtration slits provide a pathway for fluid leaving glomerular
Describe the pressure forces in glomerular filtration and how both autoregulation and extinctic sympathetic regulation come to play
compare the reabsorption processes in the proximal tubule for Na+, H2O and glucose
Na+ = absorbed in the ascending limb of the loop of Henle as apical Na+ channels permit the movement from the cells to the lumen passively
H2O= passively reabsorbed in descending limb of loop of Henle through aquaporins aided by increased plasma-colloid osmotic pressure in peritubular capillaries
glucose= actively moved against conc gradient from tubular lumen into the blood. No ATP directly used to operate glucose carriers. nutrients transferred by secondary active transport using symporters which transfer NA+ down gradient and glucose against it from lumen into the cell
What is ADH
antidiuretic hormone = increases distal tubule and collecting duct permeability to water by increasing apical aquaporins as well as reducing blood flow to the bodies extremities
what is the renin-angiotensin system
a critical regulator of blood volume, electrolyte balance and systemic vascular resistance.
stimulates Na+ reabsorption in DT and CD, elevates blood pressure and stimulates thirst and salt hunger
- angiotensin and aldosterone increase Na+ and water reabsorption
1) Juxtaglomerular apparatus responds to low blood volume or blood pressure due to dehydration
2) causes renin production, angiotensinogen and angiotensin II production
3) this causes either the adrenal gland to produce aldosterone which increases Na+ and H20 reabsorption in DT or causes arteriole constriction altering blood pressure and volume
what are the mechanism’s which regulate PH in the kidney
1) cellular buffering
2) respiration (co2)
3) renal excretion (H+ and HCO3-)
How does the fine tuning of acid base balance in the DCT and collecting duct occur
Two types of cells
1) acid secreting = co2 and water and carbonic anhydrase produce protons and bicarbonate ions. The active transport of protons into filtrate on apical membranes causes reabsorption of bicarbonate ions lowering acidity
2) base secreting = the reverse process, excretion of bicarbonate ions causes increased uptake of H+
how do animals adapt to a lack of water
they produce more concentrated urine due to physiological differences in the kidney e.g. longer loop of henle
what solutions do kangaroo rats use to overcome lack of water availability
- depends on metabolic water
- excrete uric acid as solid crystals
- produces hyper-concentrated urine
- counter current cooling in nasal passages
- behavioural adaptations
outline the kidney physiology in kangaroo rats who have adapted to a lack of water
- thick medulla and thin cortex
- loop of Henle is very long, mitochondrial rich and increased number of aquaporins
