excretory products and elimination Flashcards
(31 cards)
describe ammonotelism
- process of excreting ammonia
- Bony fishes, aquatic amphibians, aquatic insects.
why are kidneys not important for ammonotelic organisms?
- As ammonia is readily soluble, it is generally excreted by diffusion across body surfaces or through gill surfaces (in fish) as ammonium ions thus, kidneys do not play a significant role in its removal.
which are ureotelic organisms?
organisms excreting urea-marine fishes, mammals, and terrestrial amphibians
why are they ureotelic?
- some amount of urea from the blood may be retained in the kidney matrix to maintain a desired osmolarity
uricotelic organisms
reptiles, birds, land snails and insects.
in the form of pellet or paste
how much percentage of reabsorption occurs in the PCT and what is the feature that enables it?
- 70-80% of electrolytes and water, and nearly all essential nutrients are reabsorbed because the PCT is lined by brush bordered epithelium which increases surface area for reabsorption.
where are kidneys located
between the levels of last thoracic and third lumbar close to the dorsal inner wall of the abdominal cavity.
dimensions of the kidney in an adult human
- length: 10-12 cm
- width: 5-7 cm
- thickness: 2-3 cm
weight of kidneys
120-170 g
nephron divided into
renal tubules and glomerulus
kidney differentiated into
outer cortex and inner medullary
malphigian body or renal corpuscle?
glomerulus along with bowman’s capsule
what are juxtamedullary and cortical nephrons?
juxtamedullary nephrons are those which have a ver long loop of henle that runs deep into the medulla whereas the cortical nephrons have a very short loop of Henle and extends only very little into the medulla
glomerular filteration rate?
- amount of filtrate formed by the kidneys per minute is called GFR
- in a healthy individual, GFR is 125 ml/minute, i.e., 180 litres per day.
how much blood is filtered per min?
1100-1200 ml of blood is filtered by the kidneys per minute which is roughly 1/5th of the blood pumped by each ventricle in a minute.
special feature of epithelium of bowman’s capsule?
epithelial cells of bowman’s capsules called podocytes are arranged in an intricate manner so as to leave some filtration slits or slit pores through which blood is filtered so finely that almost all the components of plasma pass onto the lumen except the proteins.
the 3 layers through which glomerular filtration takes place
endothelium og glomerular blood vessels, epithelium of bowman’s capsule, and the basement membrane between these 2 layers
susbtances reabsorbed by tubular epithelial cells and which transport?
- glucose, amino acids, Na+(sodium ions)-active transport
-nitrogenous wastes and water are absorbed passively
peritubular capillaries
fine capillary network formed by the efferent arteriole around the renal tubules
How does PCT maintain pH and ionic balance?
- by reabsorption of bicarbonate ions and secretion of H+ ions, potassium ions, and ammonium ions into the fiulterate
role of henles loop and its limbs?
- reabsorption is minimum but plays an important role in maintenance of osmolarity of medullary interstitial fluid
- the DL- is permeable to water but impermeable to electrolytes due to presence of aquaporin which conentrates the filtrate
- AL is permeable to electrolytes and impermeable to water which dilutes the filtrate as electrolytes move into the interstitial medullary fluid
DCT
- conditional resorption of sodium ioons and water take place in this segment as well as bicarbonate ions and selective secretion of H+, K+, and NH3 takes place to maintain pH and sodium-potassium balance in the blood
collecting duct
Large amounts of water are reabsorbed which concentrates the urine and ph and ionic balance of the blood is maintained by selective secretion of H+ and K+ ions.
-IT ALSO ALLOWS SMALL AMOUNTS OF UREA TO PASS INTO THE INTERSTITIAL FLUID TO MAINTAIN OSMOLARITY
explain counter current mechanism 😘😘😘
later 😝😝