Download MBBS Physiology Presentations 5 Tubular Processes Lecture Notes

Download MBBS (Bachelor of Medicine, Bachelor of Surgery) 1st Year, 2nd Year, 3rd Year and Final year Physiology 5 Tubular Processes PPT-Powerpoint Presentations and lecture notes


Tubular Processes ? Handling of TF

Learning Objectives

To understand

Terminology to know processes of handling tubular fluid ?

Renal Tubular Reabsorption or Secretion- Transcellular & paracellular pathway

Tubular Cells ?Tight Junctions

To calculate secretion or reabsorption rate of any solute

Nephron Terminology

Various transport mechanisms in proximal convoluted tubules

Glomerulo-tubular balance, and it's physiologic importance

Glucose transport maximum
Terminology to know processes of handling tubular fluid

Tubular Reabsorption or Secretion in Renal Tubules

PTCp

1. Reabsorption:

1

2. Secretion:

TF

2.
Tubular Cells ?Tight Junctions

PTCp

Tight junctions

1

Tight junctions ? claudins and occludins.

TF

2.

Tubular Reabsorption/Secretion - Routes/Pathways

PTCp

Transcel ular pathway:

1

Paracellular pathway:

TF

2.
Pressures favoring reabsorption by bulk flow into peritubular Cps

bulk

flow

GENERAL PRINCIPLES OF MEMBRANE TRANSPORT ? across cell membranes

Passive transport of substances (without expenditure of energy):

Active transport of subtances (with the expenditure of energy):

Solvent drag-
Nephron : Tubular Segments

Three major segments:

These segments determine the composition & volume of the urine by the

Reabsorption and Secretion Rates of substances in renal tubules
Nephron Terminology

TF/P ratio

2. TF/Pinulin

3. [TF/P]x /[TF/P]inulin ratio

Exercise questions
Segment - Proximal Convoluted Tubule ?

Tubule Characteristics --TF handling as per Permeability

+ADH/ - ADH

AQP1

Transport mechanisms of different solutes of TF ? PxCT
First half of Px CT

Active NaCl Transport

H2O

NaCl

Urea

++

Early Part of Proximal Convoluted Tubule PxCT

++

+

+

H2O

Na+ Reabsorption
Active NaCl Transport

H2O

NaCl

Urea

++

Early Part of Proximal Convoluted Tubule PxCT

++

+

+

H+ secretion and

H2O

HCO3-Reabsorption

Early Part of Proximal Convoluted Tubule

Active NaCl Transport

H2O

NaCl

Urea

PxCT

++

++

+

+

Glucose

reabsorption
Applied-

Mutations in the GLUT2 gene

Active NaCl Transport

H2O

NaCl

Urea

++

Early Part of Proximal Convoluted Tubule PxCT

++

+

+

Ca++, Mg++, K+ , Urea

Paracellular

H

reabsorption

2O
Second half of Px CT

Active NaCl Transport

H2O

NaCl

Urea

++

Second half of PxCT

PxCT

++

+

+

Na+ and Cl-

reabsorption
Active NaCl Transport

H2O

NaCl

Urea

++

Second half of PxCT

PxCT

++

+

+

(Mechanism: Na+H+ - Cl-Anion Antiporters)

Second half of PxCT

Na+-glucose symporter (SGLT1)
Second half of Proximal Convoluted Tubule

Water reabsorption

Urea reabsorption

Pinocytosis--An Active Transport Mechanism for Reabsorption of

large molecules such as Proteins in PxT
Summary of handling of % of water & solutes ? Px CT

Summary of Transporters in Px CT
Osmolality of TF Leaving PxCT

Clinical Relevance ? Acute Tubular Necrosis (ATN )
Transport Maximum (Tm)

Blood glucose level and corresponding Glucose tubular load

This glucose blood concentration (200 mg/dl) and the filtered load of 250 mg/min are

termed as the renal threshold for glucose.
Cause of difference of TmG and Renal threshold for glucose

Phenomenon of SPLAY

ideal

(or glucose amount filtered)

Regulation of Tubular processes

Because it is essential to maintain a precise balance between tubular

reabsorption and glomerular filtration, there are multiple nervous,

hormonal, and local control mechanisms that regulate tubular

reabsorption.
Glomerulo-tubular Balance

Glomerulo-tubular balance - Mechanism
Tubuloglomerular feedback vs Glomerulo-tubular balance

N
aC
l

Self Assessment

Percentage of filtered urea, reabsorbed by Px CT is about :

1. 00-25
2. 50 -65

3. 70-95

4. 80-100

If there is increased load of NaCl and water, what wil happen in Px CT

1) There wil be an increase in NaCl and water reabsorption.

2) There wil be a decrease in NaCl and water reabsorption.

3) There wil be an increase in NaCl but water reabsorption wil decrease
4) There wil not be any change

Water channel present in proximal convoluted tubule is:

1. Aquaporin 1
2. Aquaporin 2
3. Aquaporin 3

4. Aquaporin 4

At the leaving end of PxCT, percentage of filtered solute
and water is approximately:

1) 35% solute and 35% water

2) 45% solute and 45% water

3) 35% solute and 45% water
4) 45% solute and 35% water
Thank you

This post was last modified on 08 April 2022