Biology B6 - Glomerulus & Nephron Functions

Questions and Answers

What causes the blood in the glomerulus to be under very high pressure?

The efferent arteriole is smaller in diameter than the afferent one.

What are the stages of osmoregulation carried out by the nephron in order? (Select all that apply)

Reabsorption of glucose and water by the proximal convoluted tubule (correct)

Reabsorption of water by the collecting duct

Maintenance of a gradient of sodium ions in the medulla by the loop of Henle (correct)

Formation of glomerular filtrate by ultrafiltration (correct)

What part of the nephron does ultrafiltration take place?

The Bowman's capsule and glomerulus.

Explain the process of ultrafiltration.

Blood enters glomerulus from afferent arteriole under high pressure. High pressure forces water, mineral ions, urea, and glucose out, forming glomerular filtrate. Blood cells and proteins remain in the blood. Signup and view all the answers

What three layers do substances need to move through during filtration? (Select all that apply)

Basement membrane Signup and view all the answers

Describe how ultrafiltration occurs in a glomerulus.

High blood pressure forces small substances like water, glucose, ions, and urea through small gaps in the capillary endothelium and through the basement membrane. Signup and view all the answers

Approximately what percentage of glomerular filtrate is reabsorbed back into the blood?

85% Signup and view all the answers

Where does selective reabsorption take place?

Proximal convoluted tubule (PCT). Signup and view all the answers

What is the purpose of selective reabsorption?

To reabsorb useful substances into the blood. Signup and view all the answers

Explain the process of selective reabsorption.

Na+ is actively transported out of PCT cells into blood, lowering Na+ concentration in cells. A gradient forms, causing Na+ to diffuse into cells, co-transporting glucose and amino acids. Solutes then diffuse into blood, with some water moving by osmosis. Signup and view all the answers

What is usually found in urine? (Select all that apply)

Excess vitamins Signup and view all the answers

Study Notes

Blood Pressure in the Glomerulus

High pressure in the glomerulus is due to the efferent arteriole being smaller in diameter than the afferent arteriole.

Stages of Osmoregulation by Nephron

Formation of glomerular filtrate occurs via ultrafiltration.
Proximal convoluted tubule reabsorbs glucose and water.
Loop of Henle maintains sodium ion gradient in the medulla.
Water is reabsorbed in distal convoluted tubule and collecting ducts.

Location of Ultrafiltration

Ultrafiltration takes place in the Bowman's capsule and glomerulus.

Process of Ultrafiltration

Blood enters the glomerulus through the afferent arteriole under high pressure.
High pressure pushes water, ions, urea, and glucose out to form glomerular filtrate.
Blood cells and large proteins remain in the blood due to their size.

Layers for Substance Movement

Water, ions, urea, and glucose pass through three layers: capillary wall, basement membrane, and epithelium of Bowman's capsule.
Podocytes in the epithelium have gaps, allowing for easier movement.
Endothelium of glomerular capillaries has fenestrations for filtration.

Ultrafiltration in Glomerulus

High hydrostatic pressure facilitates filtration.
Small substances such as water, glucose, and ions pass through capillary pores and basement membrane.

Reabsorption of Glomerular Filtrate

Approximately 85% of glomerular filtrate is reabsorbed back into the bloodstream.

Selective Reabsorption Location

Selective reabsorption primarily occurs in the proximal convoluted tubule (PCT).

Purpose of Selective Reabsorption

To recover useful substances from the filtrate into the blood.

Mechanism of Selective Reabsorption

Sodium ions (Na+) are actively transported from PCT cells into blood capillaries, lowering Na+ concentration in cells.
Creates a Na+ concentration gradient between the PCT lumen and epithelial cells.
Na+ diffuses from the lumen into epithelial cells, while glucose and amino acids are co-transported with Na+.
Nutrients then diffuse into the bloodstream, and water follows by osmosis due to lower water potential in blood.

Composition of Urine

Urine typically contains water, dissolved salts, urea, and excess vitamins.

Description

Dive into the roles of the glomerulus and nephron in osmoregulation with these flashcards. Learn about the pressure dynamics in the glomerulus and the sequential stages involved in nephron function. Perfect for mastering key concepts in biology.