Title: Reabsorption and Secretion Along the Proximal Tubule - Anatomy & Physiology - WikiVet English
Headings: Reabsorption and Secretion Along the Proximal Tubule - Anatomy & Physiology
A Tribute to Nick Short
Reabsorption and Secretion Along the Proximal Tubule - Anatomy & Physiology
Contents
Introduction to Reabsorption
Proportion of Filtered Substances Reabsorbed in the Proximal Tubule
Epithelial Transport
Ions and Compounds
Sodium
Water
Potassium
Urea
Glucose
T Max and Splay
The Kidneys Role In Glucose Regulation
The Secretion of H+ and the Reabsorption of HCO3-
Reabsorption of HCO3-
Protein
Primary Active Secretion - Organic Acids and Bases
Calcium
Revision

Content: he has left many legacies which will ensure that he will be remembered for many years. Our thoughts are with his friends and family at this heartbreaking time. A book of remembrance has been set up for anyone that would like to leave a message of condolence for Nick and his family have asked that anyone who wishes to do so make a donation to BipolarUK, a charity that was close to Nick’s heart. Reabsorption and Secretion Along the Proximal Tubule - Anatomy & Physiology
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Reabsorption and Secretion Along the Proximal Tubule - Anatomy & Physiology
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WikiVet LIVE - at the Virtual Congress 2021 - WikiVet has partnered with The Webinar Vet and created a student stream at the Virtual Congress 2021
There is a limited number of FREE tickets for students – on a first come first serve basis. Contents
1 Introduction to Reabsorption
2 Proportion of Filtered Substances Reabsorbed in the Proximal Tubule
3 Epithelial Transport
4 Ions and Compounds
4.1 Sodium
4.2 Water
4.3 Potassium
4.4 Urea
4.5 Glucose
4.5.1 T Max and Splay
4.5.2 The Kidneys Role In Glucose Regulation
4.6 The Secretion of H+ and the Reabsorption of HCO3-
4.6.1 Secretion of H+
4.6.2 Reabsorption of HCO3-
4.7 Protein
4.8 Primary Active Secretion - Organic Acids and Bases
4.9 Calcium
5 Revision
Introduction to Reabsorption
The proximal tubule is a major site for reabsorption and some secretion. Gradients are small across the epithelium so tight regulation is not possible
This occurs in the distal tubule
65-80% of the filtrate is reabsorbed
Most reabsorption is coupled to sodium ion movement
Small proteins and peptide hormones are reabsorbed by endocytosis
Other substances are secreted or reabsorbed in the tubules passively by facilitated, non-facilitated diffusion or ion channels down chemical or electrical gradients. Other substances are secreted or reabsorbed by active transport against such gradients
Movement is via ATPases. The reabsorbed material enters peritubular capillaries
This is mainly driven by the Sodium/Pottasium ATPase in the basolateral membrane. This protein removes sodium from the cell maintaining the gradient between the lumen and the epithelium. Sodium reabsorption is driven by this protein
Water and chloride then follow the transported sodium
This is the most important transport mechanism in the proximal tubule
Proportion of Filtered Substances Reabsorbed in the Proximal Tubule
Substance
% of Filtrate Reabsorbed
Sodium and Water
~66%
Organic solutes e.g. glucose and amino acids
~100%
Potassium
~65%
Urea
~50%
Phosphate
~80%
Epithelial Transport
Sodium is the most important ion in relation to reabsorption from the proximal tubule.