Urinary Flashcards: Nephron Types

Questions and Answers

Which nephron type is characterized by long nephron loops and a higher glomerular filtration rate?

Neither

Juxtamedullary Nephron (correct)

Cortical Nephron

Both Cortical and Juxtamedullary Nephrons

What is the primary difference in structure between cortical and juxtamedullary nephrons?

Cortical nephrons have short nephron loops, while juxtamedullary nephrons have long nephron loops that maintain a salt gradient.

What is the difference in osmolarity between blood plasma and renal medulla?

The osmolarity of the renal medulla is higher than that of blood plasma.

How is the osmotic gradient of the renal medulla maintained?

The osmotic gradient is maintained by loops of Henle having different permeabilities to salt and water. Signup and view all the answers

What is the function of the vasa recta?

The vasa recta supplies blood to the medulla and removes excess solutes and water. Signup and view all the answers

What is renal autoregulation?

Renal autoregulation is the ability of nephrons to adjust their own blood flow and GFR without external control. Signup and view all the answers

What is the effect of sympathetic control on GFR?

Sympathetic control decreases GFR and urine output during stress by constricting afferent arterioles. Signup and view all the answers

How does angiotensin II influence glomerular filtration rate?

Angiotensin II constricts efferent arterioles, increasing glomerular blood pressure and GFR. Signup and view all the answers

What is the main function of peritubular capillaries?

Peritubular capillaries facilitate the reabsorption of water and solutes from the nephron. Signup and view all the answers

What is reabsorbed by the proximal convoluted tubule?

The proximal convoluted tubule reabsorbs NaCl, K, H2O, glucose, and bicarbonate. Signup and view all the answers

How do permeability characteristics of the loop of Henle differ?

The descending limb is permeable to water, while the ascending limb is impermeable to water. Signup and view all the answers

Where does urea recycling occur and what is its function?

Urea recycling occurs in the collecting duct and helps maintain the osmotic gradient of the medulla. Signup and view all the answers

Where are the receptors for aldosterone and ADH located?

The receptors for aldosterone and ADH are located in the principal cells of the collecting duct. Signup and view all the answers

What are the effects of ADH, ANP, and aldosterone on the kidney?

ADH promotes water reabsorption, ANP increases urine volume, and aldosterone promotes sodium and water reabsorption. Signup and view all the answers

Describe the renin-angiotensin-aldosterone pathway.

The pathway regulates blood pressure and fluid balance through renin release, converting angiotensinogen to angiotensin II, which stimulates aldosterone release. Signup and view all the answers

What are the typical constituents of urine?

Typical constituents include urea, NaCl, KCl, creatinine, and uric acid, with a pH range of 4.5 - 8.2. Signup and view all the answers

How do transport maxima and GFR affect reabsorption?

Transport maxima determine the maximum reabsorption capacity, while GFR influences the amount of filtrate available for reabsorption. Signup and view all the answers

Study Notes

Nephron Types

Cortical nephrons (85%): Short nephron loops with glomeruli in the outer renal cortex; responsible for excretory and regulatory kidney functions.
Juxtamedullary nephrons (15%): Long loops of Henle that penetrate deeply into the medulla; crucial for maintaining osmotic gradient and concentrating urine.

Osmolarity

Blood plasma osmolarity is crucial for physiological functions, while renal medulla osmolarity is involved in urine concentration and water balance.

Loop of Henle Function

Establishes osmotic gradient in the renal medulla, preventing excessive production of dilute urine.
Ascent and descent differ in permeability: descending limb is permeable to water; ascending limb is impermeable to water but allows solute diffusion.

Vasa Recta Structure and Function

Vasa recta provides blood supply to the medulla with high permeability to solutes and water.
Responsible for nutrient delivery and efficient removal of excess solutes and water from the interstitium.

Renal Autoregulation of GFR

Nephrons can self-regulate blood flow and GFR, maintaining stable filtration rates despite fluctuations in arterial blood pressure.

ANS and GFR Control

Sympathetic nervous system stimulation constricts afferent arterioles during stress, reducing GFR and redirecting blood to vital organs.

Renin-Angiotensin System

Drop in blood pressure activates baroreceptors, stimulating renin release, which triggers a cascade increasing blood volume and pressure via angiotensin II.

Peritubular Capillaries

High colloid osmotic pressure (COP) and low blood hydrostatic pressure (BHP) favor reabsorption of water and solutes back into circulation.

Nephron Components and Functions

Different nephron segments (proximal convoluted tubule, loop of Henle, distal convoluted tubule) are specialized for filtration, absorption, and secretion.

Proximal Convoluted Tubule Functions

Reabsorbs 65% of glomerular filtrate, including NaCl, K, water, glucose, and bicarbonate.
Secretes waste products such as urea and ammonium ions.

Urea Recycling

Occurs in the collecting duct and medulla; urea contributes to the osmolarity gradient, aiding in urine concentration.

Aldosterone and ADH Effects

Aldosterone promotes sodium and water reabsorption in the distal tubule and collecting duct.
ADH increases water reabsorption in the collecting duct, concentrating urine and reducing volume.
Atrial Natriuretic Peptide (ANP) has opposite effects, promoting sodium and water excretion.

Renin-Angiotensin-Aldosterone Pathway

Involves complex interactions starting from renin release to increasing blood pressure and fluid balance through angiotensin II and aldosterone.

Urine Composition

Normal urine composition: 95% water, 5% solutes (urea, NaCl, KCl, creatinine).
pH typically ranges from 4.5 to 8.2, usually around 6.0; elevated solutes like proteins should not be present.

Transport Maxima and GFR

Transport maximum influences reabsorption capacity; if limits are exceeded, certain substances may remain in filtrate despite normal GFR levels.

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Description

Explore the differences between cortical and juxtamedullary nephrons in this quiz. Learn how each type contributes to kidney function, especially in water conservation and osmotic gradient maintenance. Test your understanding of nephron structures and their roles in urine formation.