excretory products and elimination

Question 1

describe ammonotelism

Answer 1

• process of excreting ammonia
• Bony fishes, aquatic amphibians, aquatic insects.

Question 2

why are kidneys not important for ammonotelic organisms?

Answer 2

• 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.

Question 3

which are ureotelic organisms?

Answer 3

organisms excreting urea-marine fishes, mammals, and terrestrial amphibians

Question 4

why are they ureotelic?

Answer 4

• some amount of urea from the blood may be retained in the kidney matrix to maintain a desired osmolarity

Question 5

uricotelic organisms

Answer 5

reptiles, birds, land snails and insects.
in the form of pellet or paste

Question 5

how much percentage of reabsorption occurs in the PCT and what is the feature that enables it?

Answer 5

• 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.

Question 5

where are kidneys located

Answer 5

between the levels of last thoracic and third lumbar close to the dorsal inner wall of the abdominal cavity.

Question 5

dimensions of the kidney in an adult human

Answer 5

• length: 10-12 cm
• width: 5-7 cm
• thickness: 2-3 cm

Question 5

weight of kidneys

Answer 5

120-170 g

Question 5

nephron divided into

Answer 5

renal tubules and glomerulus

Question 5

kidney differentiated into

Answer 5

outer cortex and inner medullary

Question 5

malphigian body or renal corpuscle?

Answer 5

glomerulus along with bowman’s capsule

Question 6

what are juxtamedullary and cortical nephrons?

Answer 6

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

Question 6

glomerular filteration rate?

Answer 6

• 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.

Question 6

how much blood is filtered per min?

Answer 6

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.

Question 6

special feature of epithelium of bowman’s capsule?

Answer 6

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.

Question 6

the 3 layers through which glomerular filtration takes place

Answer 6

endothelium og glomerular blood vessels, epithelium of bowman’s capsule, and the basement membrane between these 2 layers

Question 6

susbtances reabsorbed by tubular epithelial cells and which transport?

Answer 6

• glucose, amino acids, Na+(sodium ions)-active transport
  -nitrogenous wastes and water are absorbed passively

Question 6

peritubular capillaries

Answer 6

fine capillary network formed by the efferent arteriole around the renal tubules

Question 7

How does PCT maintain pH and ionic balance?

Answer 7

• by reabsorption of bicarbonate ions and secretion of H+ ions, potassium ions, and ammonium ions into the fiulterate

Question 8

role of henles loop and its limbs?

Answer 8

• 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

Question 9

DCT

Answer 9

• 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

Question 10

collecting duct

Answer 10

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

Question 11

explain counter current mechanism 😘😘😘

Answer 11

later 😝😝

Question 12

what do osmoreceptors do?

Answer 12

osmoreceptors in the body are activated by changes in blood volume, body fluid volume, and ionic conc.
- An excessive loss of fluid can activate these receptors which stimulate the hypothalamus to release ADH.
-ADH facilitates water reabsorption to prevent diuresis
- increase in body fluid volume turns off the receptors and suppress ADH release.
- ADH can increase BP due to its constrictory effects on blood vessels which can increase GFR

Question 13

explain JGA/RAAS mechanism

Answer 13

1. fall in glomerular blood flow/pressure/rate can activate JG cells to release renin
2. renin converts angiotensin in blood to angiotensin I and further into angiotensin II which activates adrenal cortex to release aldosterone which causes reabsorption of water and Na+ from distal parts of the tubule thereby increasing GFR.

Question 14

role of ANF

Answer 14

• increase in blood flow to the heart can cause release of ANF.
• ANF can cause vasodilation and thereby decrease BP, this acts as a check on RAAS mechanism.

Question 15

explain micturition

Answer 15

lazy

Question 16

an adult human, on average, excretes how many litres? and how much urea per day?

Answer 16

• 1-1.5 L per day
• 25-30 gm of urea

Question 17

sebaceous glands secrete

Answer 17

hydroicarbons, sterols, sebum waxes

Question 18

renal calculi?

Answer 18

stone or insoluble mass of crystallized salts(oxalates,etc.) formed within the kidney