11.3 - Kidney and Osmoregulation Flashcards
Osmoregulators and osmocomformers
osmoregulators are organisms that maintain an internal solute concentration independent of their environment
osmocomformers are organisms that have the same solute concentration as their environment
Malpighian tubule system
osmoregulation and nitrogenous waste removal of blood in insects and the kidney
In insects/anthropods:
- hemolymph circulates containing blood and tissue characteristics
- malpighian tubule absorbs uric acid and ions from hemolymph (water follows by osmosis)
- ions and water are reabsorbed at the hindgut
- uric acid is excreted with feces
in animals:
- blood circulates in a closed system
- urea is filtered out of blood by the kidneys
Kidney (function, contents of artery vs vein + diagram)
organ with the function of osmoregulation and excretion removing nitrogenous waste and other unwanted substances from filtrate
- filtrate is blood plasma containing all contents of blood besides large proteins that is filtered by the kidneys where unwanted substances are removed as urine and wanted are reabsorbed into the blood
renal artery: blood enters the kidney (smaller in diameter)
- higher oxygen (than renal vein)
- higher glucose
- higher nitrogenous waste
- higher toxins
- excess water
- excess ion
- same protein
renal vein: blood leaves to heart (larger in diameter)
- higher CO2 than artery
- cortex: outer layer containing most of nephron, 1/5 of width
- medulla: inner layer where loop of henle extends, pyramids
- renal pelvis: protrusion on concave side
- ureter: extension draining renal pelvis
Nephron (diagram)
Nephron: functional unit of the kidney
- Glomerulus: bed of high pressure capillaries for ultrafiltration
- Bowman’s capsule: cup-shaped structure with porous wall collecting glomerular filtrate
- Proximal convoluted tubule: tube with many microvilli and mitochondria that reabsorbs useful substances from glomerular filtrate
- Loop of Henlé: tube carrying filtrate into the medulla in a descending limb and back into the cortex in the ascending limb to maintain hypertonic conditions in the medulla
- Distal convoluted tubule: tubes with microvill and mitochondria (less than proximal tube) to reabsorb water
- Collecting duct: wide tube carrying filtrate to renal pelvis (continued absorption of water)
Glomerulus and Bowman’s capsule
glomerulus is a network of high pressure capillaries with fenestrations, basement membrane and podocytes for the ultrafiltration of blood to glomerular filtrate
- fenestrations: pores in capillary wall allowing plasma but not blood cells to be filtered
- basement membrane: mesh surrounding capillaries preventing proteins from being filtered (charge and size)
- podocytes: epithelial cells of Bowman’s capsule with foot processes and projections surrounding capilaries to filter out waste products
Bowman’s capsule: surrounds glomerulus to collect filtrate
Proximal convoluted tubule
tube in nephron that reabsorbs useful substances from filtrate
- Na+ active transport out of the tubule
- all amino acids and glucose are co-transported by energy from Na+ flowing back into tube
- Cl- transported by attraction to charge gradient from high concentration of Na+ outside tube
- 80% water transported by osmosis, high solute concentration outside
Loop of Henle
selectively permeable descending and ascending arm for countercurrent multiplier system to create a concentration gradient in the medulla
ascending arm:
- permeable to Na+ by active transport but not water
- Na+ concentration increases in medulla interstitial fluid
descending arm:
- permeable to water but not Na+
- water is drawn out by osmosis due to high Na+ concentration in medulla interstitial fluid from ascending arm
countercurrent multiplier system: as filtrate passes through, concentration gradient continues to rise
longer loop of Henlé is correlated with more water reabsorbed from filtrate (amplification of solute gradient)
Control of water absorption from collecting duct and distal convoluted tube
both have low permeability to water, but due to hypertonic interstitial fluid of medulla from loop of henle, and villi water is reabsorbed into by osmosis
antidiuretic hormone (ADH) secreted by the pituitary gland stimulates the tubes to increase permeability to water
- when blood solute concentration is too low, ADH is not secreted to decrease reabsorption of water and increase solute concentration
- when blood solute concentration is too high, ADH is secreted to increase water absorption and lower solute concentration
Type of nitrogenous waste
Ammonia product of break down of amino acids is toxic and basic
- ammonia is excreted by aquatic animals because it is diluted by water in the environment
- urea is excreted by terrestrial mammals in urine because ammonia is too toxic so broken down which requires energy
- uric acid is the least toxic form excreted by birds with feces requiring the most energy (flight born animals with reduced water weight)
Dehydration and overhydration (consequences)
dehydration: more water expelled then enters the body
- high blood solute concentration
- damaged tissue from exposure to waste
- fatigue
- increased heart rate
- low blood pressure (low volume)
- muscle malfunction
overhydration: overconsumption of water
- nervous function disrupted
- swelling cells
- headaches
Treatments of kidney failure
- hemodialysis: external dyalisis machine that blood passes through with selectively permeable membrane to filter out waste and return to patient (time consuming, no travel, fatigue at the end of week, frequent visits)
- kidney transplant: failed kidney is replaced by a donor kidney (risk of rejection)
Urinalysis
examinination of urine using urine test strips to determine difference from normal composition
strip changes colour indication pH, protein, glucose levels, drugs, blood cells
- glucose: diabetes
- proteins: diabetes, damaged kidney
- white blood cells: urinary tract infection
- red blood cells: tumour, kidney stones
