IB Biology Topic D3.3.8 Role of the Glomerulus, Bowman’s Capsule and Proximal Convoluted Tubule in Excretion Revision Notes (HL)

IB Biology Topic D3.3.8 Role of the Glomerulus, Bowman’s Capsule and Proximal Convoluted Tubule in Excretion Revision Notes (HL) | RevisionDojo

Written by official IB examiners

The Nephron Filters Blood Then Reclaims What the Body Needs

The kidney removes waste from the blood while keeping useful substances such as glucose and ions.
This work happens in the nephron, the functional unit of the kidney.
Two steps matter here: ultrafiltration in the glomerulus and Bowman's capsule, then selective reabsorption in the proximal convoluted tubule.

Note

The nephron filters blood and forms urine.

High Blood Pressure in the Glomerulus Drives Ultrafiltration

Blood enters the glomerulus, a ball of capillaries, through the wide afferent arteriole and leaves through the narrower efferent arteriole.
This difference in width raises the hydrostatic (blood) pressure inside the glomerulus.
The high pressure forces water, ions, glucose, urea, and other small molecules out of the blood into Bowman's capsule.
The liquid that collects in Bowman's capsule is the glomerular filtrate.

Tip

Ultrafiltration is filtration under pressure, driven by the high hydrostatic pressure in the glomerulus.

The Filtration Barrier Acts as a Sieve That Holds Back Large Molecules

The filtration barrier lets small molecules pass while holding back blood cells and large plasma proteins.
The barrier has three layers.
Fenestrated capillary endothelium
1. Its pores let fluid and small solutes leave the blood while blocking cells.
Basement membrane
1. This mesh of negatively charged glycoproteins repels plasma proteins by size and charge.
Podocytes of Bowman's capsule
1. Their interlocking foot processes leave narrow filtration slits that admit only small molecules.

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The Nephron Filters Blood Then Reclaims What the Body Needs

The kidney removes waste from the blood while keeping useful substances such as glucose and ions.
This work happens in the nephron, the functional unit of the kidney.
Two steps matter here: ultrafiltration in the glomerulus and Bowman's capsule, then selective reabsorption in the proximal convoluted tubule.

Note

The nephron filters blood and forms urine.

High Blood Pressure in the Glomerulus Drives Ultrafiltration

Blood enters the glomerulus, a ball of capillaries, through the wide afferent arteriole and leaves through the narrower efferent arteriole.
This difference in width raises the hydrostatic (blood) pressure inside the glomerulus.
The high pressure forces water, ions, glucose, urea, and other small molecules out of the blood into Bowman's capsule.
The liquid that collects in Bowman's capsule is the glomerular filtrate.

Tip

Ultrafiltration is filtration under pressure, driven by the high hydrostatic pressure in the glomerulus.

The Filtration Barrier Acts as a Sieve That Holds Back Large Molecules

The filtration barrier lets small molecules pass while holding back blood cells and large plasma proteins.
The barrier has three layers.
Fenestrated capillary endothelium
1. Its pores let fluid and small solutes leave the blood while blocking cells.
Basement membrane
1. This mesh of negatively charged glycoproteins repels plasma proteins by size and charge.
Podocytes of Bowman's capsule
1. Their interlocking foot processes leave narrow filtration slits that admit only small molecules.

Definition

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anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic D3.3.8: Role of the Glomerulus, Bowman’s Capsule and Proximal Convoluted Tubule in Excretion Notes

The Nephron Filters Blood Then Reclaims What the Body Needs

High Blood Pressure in the Glomerulus Drives Ultrafiltration

The Filtration Barrier Acts as a Sieve That Holds Back Large Molecules

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

The Nephron Filters Blood Then Reclaims What the Body Needs

High Blood Pressure in the Glomerulus Drives Ultrafiltration

The Filtration Barrier Acts as a Sieve That Holds Back Large Molecules

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics