Question

14) Using the following findings of volume flow and osmolarity throughout a nephron, describe andfully explain the processes occurring at each of the listed sites of the nephron, to generate the listed flow and osmolarity.

Blood flow into the glomerulus is at 280 mOsM, of which the albumin (large proteins) constitutes 90 mOsM. FLUID OSMOLARITY FLOW VOLUME Glomerular Filtrate 300 mOsM 7.5 L per hour End of Proximal Tubule 300 mOsM 2.5 L per hour End of Descending Loop 1200 mOsM 0.625 L per hour End of Ascending Loop 100 mOsM 0.625 L per hour Distal Tubule through End of Collecting Duct 100 mOsM 0.25 L per hour GLOMERULUS -PROXIMAL TUBULE -DESCENDING LOOP -ASCENDING LOOP -DISTAL NEPHRON

15) Describe the expected immune response to the following scenario: enveloped virus particles enter through the respiratory system, infecting epithelial cells of the upper airways. As the bronchial epithelial cells die and release new viral particles, these enter lymphatic capillaries and travel to the lymph nodes in the neck

. (16) A vaccine for Coronavirus is likely to take a longer time than imagined, because the most obvious target of the vaccine should be the external spike protein on the envelope of this enveloped virus. The cellular attachment protein on epithelial cells, which the virus binds to for entry into the epithelial cell, is known to be ACE2, a receptor enzyme. Explain why the production of a vaccine targeting the coronavirus spike protein (S1), is not likely to be successful.

Answer 1

Answer:

Q-14):

1) Golomerulus :

• Ultrafiltration occurs at Golmerular capillary through fenistration slit.
• All the solute gets freely filtered. Plasma Proteins being large in size and negatively charged does not get filtered.
• Plsama preoteins are responsible for the oncotic pressure, which keeps the water bound to it.
• Hence due to more osmotic pressure in glomerular capillary less water is filtered compared to solute.
• Hence Osmolarity of filterate is more i.e. 300 compared to plasma.

2)End of Proximal tubule :

• Active reabsorption of solute occurs in PCT. 60-70% of the solute is Reabsorbed here.
• Along with solute water is also aeabsorbed by solvent drag in equal proportions.
• Hence the Osmolarity at the end of PCT remains same but the volume of filterate decreses from 7.5 L to 2.5 L/hr.

3) End of Decending tubule :

• Desending limb of henle henle is freely permiable to water hence water is reabsorbed due to hight Osmolarity of medullary interstitium.
• Hence at the end of decending limb of loop of henle Osmolarity Increases drastically from 300 to 1200 mOsm and the volume of fluid decreses from 2.5 to 0.65 L/hr.

4) Ascending Loop :

• Ascending Limb of limb of henle is impermeable to water while freely permiable to solute.
• Here the Osmolarity of the tubular fluid goes on decreasing as it moves up.
• Hence at the end of ascending limb the Osmolarity decreses from 1200 to 100 mOsm while the volume remains constant.

5) Distal convoluted tubule :

• Aldosterone act on distal tubule and salt and water reabsorption takes place along with secretion of K+ & H+.
• Hence Osmolarity remains the same but volume decreses from 0.65 L/hr to 0.25 L/hr.

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