osmoregulation 3 Flashcards
nitrogen excretion problem
-N excretion forms
Amino acids are essential for functions like protein building and regulating metabolism
- but ammonia produced during aa and protein breakdown is toxic and must be excreted
- nitrogen can be excreted as ammonia, uric acid, or urea
ammonia excretors are found..
- in water
- mostly invertebrates and aquatic molluscs, as well as fishes
uric acid found in..
terrestrial molluscs/arthropods, reptiles and birds
urea excretors
some larval bony fish, mammals
NOTE all species can produce any of these nitrogenous compounds due to common genetics, some just have preffered methods
ammonia excretion adv/dis
adv: directly released by breakdown of aa and proteins
dis: highly toxic, requires large volumes of water to store and excrete
- requires large amount of water to dilute its toxic affects, thus not suitable for terretrial animals
ammonia solutions
- repackaged as glutamate for storage and turned back to ammonia during excretion
- excreted across epithelium, at skin or gills
uric acid excretion
adv: few toxic effects
-can be excreted in small volume of water as anhydrous white crystals
dis: expensive to produce, requiring many (18) enzymes
(can be further broken down into urea
urea excretion
urea produced via ornithine-urea cycle, starting with glutamine and requires 5 enzymes
- urea is made in liver and transported to blood, then excreted via kidneys or gills
adv: slightly toxic, inexpensive, but moreso than uric acid, though less protein is lost (more effecient for protein recovery)
dis: urea is a perturbing solute
urea as anaosmolyte
- stored in fish to increase osmolarity, excreted when moving to less saline water to maintain osmolarity
- perturbing effects countered by methylamines
kidney functions
multiple cell types form tubelike structures to aid
- ion balance
- osmotic balance
- blood pressure
- pH balance
- excretion of metabolic wastes and toxins
- hormone production
kidney ion balance
Na+-extracellular fluid osmolarity
K+=muscle contractions Ca+, iron, trace metals
kidney osmotic balance
kidneys determine volume f urine produced and urine excreted
-dehydration (low BP) vs fluid buildup (high BP, edema)
kidney and blood pressure
- hyper/hypoe tension
- longterm changes in blood volume regulate bp
- volume of extracellular fluid under control of kidney
kidney and pH balance
- maintains pH of extracell fluids by retaining or excreting H and HCO3
- important for proper enzymatic function and transport of solutes
- also pH balance tied to nitrogenous waste disposal as many pathways involve acid or base production
kidney excretion of metabolic wastes and toxins
nitrogenous wastest and byproducts
-removal of water soluble toxins
kidney hormone production
renin=controls BP (b vessel restriction, thirst via hypothalamus
erythropoeitin-regulates RBC synthesis
nephron
- functional unit of kidney
- composed of renal tubule and vasculature
renal tubule
-lined with transport epithelium, a single layer of cells of which various segments have specific transport functions
vasculature
=glomerulus: ball of capillaries that are surrounded by the bownmans capsule of the renal tubules, where fluids are delivered to become primary urine
-capillary beds surrounding renal tubule are important for solute gradients, transport of fluid and solutes
vasculature path along nephron
renal artery, afferent arteriole, glomerulus, efferent arteriole, cap network, venous system
urine production processes
flitration: filtrate of blood formed at glomerulus
reabsorption: specific molecules in filtrate removed
secretion: specific molecules added to filtrate
excretion: urine excreted from the body
filtration
liquid part of blood fills lumen of bowmans capsule
-water and small solutes gross
-blood cells and large solutes do not
glomerular cap are very porous
mesangial cells control bp and filtration within glomerulus
-filtrate flows from bowmans capsule into proximal tubule
reabsorption
primary urine: initial filtrate filtered in bowmans capsule that is isosmotic to blood
-most water and salt in primary urine reabsorbed using transport proteins and energy
-rate of reabsorption limited by number of transporters=RENAL THRESHOLD
-conc of solute will overwhelm reabsorptive cap, and stay in tubule
each zone of nephron has transporters for specific solutes
reabsorption of glucose
- reabsorbed by secondary active transport
- brought back to blood
secretion
similar to reab, but in reverse
- molecules removed from blood transported filtrate
- includes K+, NH4+, H+, pharmaceuticals, and water-soluble vitamins
- requires transport proteins and energy
