1. Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – 422222, India

2. OC-SEP033-CP01-05 Introduction Programmes and Courses  SEP – SBT033 – Unit 01  SEP – SBI033 – Unit 01  SEP – SGS033 – Unit 01

3. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.3 Credits  Academic Inputs by Arun Punaji More. M.Sc. (Microbiology) Experience: 11 Years.  arunmesh@hotmail.com

4. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam.

5. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Describe structural anatomy of kidney. Describe process of urine formation. Describe various mechanisms of filtration, reabsorption and secretion by kidney.

6. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.6 Introduction-1  Metabolic processes produces many useful biological substances which are used to repair wear and tear of body and growth.  In metabolic processes harmful substances which disturb the homeostasis of the body are also produced.  These harmful products of metabolic processes have to either detoxify or have to be excreted from the body.

7. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.7 Introduction-2  Kidneys play important roles in the excretion of such harmful substances through the process of urine formation.  In this presentation you will learn about the mechanisms of excretion of the harmful substances from body by kidneys.  And how the kidneys maintain the body's homeostasis.

8. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.8 Structure of Kidney-1  Before understanding the mechanism of urine formation let I explain to you the structural features of kidney useful for filtering out harmful substances and urine formation.  The main structure of kidney involve in filtration process is called nephrons.  Nephron is also called as functional unit of kidney.  A single human kidney contain 1 million nephrons.

9. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.9 Structure of Kidney-2  Nephrons are not regenerated.  Number of functional nephrons get reduced with increasing age, in renal disease and renal injury.  Each nephron consist of glomerulus, a tuft of capillaries and a long tubule.  In glomerulus large amount of fluid is filtered out from blood.  Glomerular capillaries are covered by epithelial cells.  Glomerulus is encased in Bowman's capsule.

10. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.10 Structure of Kidney-3  Anatomical position of Kidneys: Main filter house of body. Main excretory organs of body.

11. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.11 Structure of Kidney-4  The glomerulus capillaries walls are negatively charged due to negatively charged proteoglycan of the capillary wall.  The large amount of fluid which is filtered out in glomerulus is converted into urine in the long tubule of nephron when it passes through it.

12. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.12 Urine Formation-1  Urine is solutions of various harmful or toxic substances such as drugs which are filtered out in glomerulus and are not reabsorbed in log tubules of nephrons.  The formation of urine occurs in three steps each of which having its own mechanism; these are Filtration, Tubular reabsorption, Tubular secretion.

13. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.13 Urine Formation-2  Nephron:- Functional unit of kidney. Consist of glomerulus, proximal tubule, distal Tubule Henle's loop.

14. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.14 Urine Formation-3  Filtration in Glomerulus:- In glomerulus filterable substances are filtered out from the blood whereas the non filterable substances remain in the blood only. The filterable substances are:  Water,  Glucose,  Sodium,  Bilirubin,  Uric acid,  Urea.

15. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.15 Urine Formation-4 Non filterable substances are:-  Proteins of more than 30 K dalton size,  Negatively charged proteins such as albumin.  Blood cells,  Fatty acids,  Calcium. The calcium and fatty acids are having smaller molecular sizes and can be easily filtered out in their free state. However, since the calcium and fatty acids remain associated with proteins molecules of larger size, they are not filtered out in glomerulus filtration.

16. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.16 Urine Formation-5  Filtration in Glomerulus:-

17. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.17 Urine Formation-6  Filtration in Glomerulus-I In glomerulus the filterable substances are filtered out from the blood into the glomerulus capsule. The filtrate collected in the glomerulus capsule contain the filterable substances as described above. The rate of glomerulus filtration is determined by  The hydrostatic and colloidal forces present in capillaries fluid and  Capillaries filtration coefficient (K f ). Which is product of capillary permeability and filtering surface area of the capillaries.

18. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.18 Urine Formation-7  Filtration in Glomerulus-2 The capillaries in glomerulus capsule have got higher filtration rate than other capillaries. The glomerulus filtration rate (GFR) in normal adult human being is 125 mL/min. The fraction of filtrate collected glomerulus capsule is given by the formula: Filtration fraction = GFR/renal plasma flow. Filtration fraction = 20%.

19. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.19 Co-transport of Glucose & Amino Acids Fig: Co-transport of glucose along with sodium.

20. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.20 Transport of Potassium Fig: Co-transport of pottasium.

21. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.21 Drugs Blocking Na channel

22. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.22 Urine Formation-8  Tubular reabsorption:- In reabsorption the substances absorbed travel to tubular epithelial membrane to interstitial fluid from where it is absorbed into blood through peritubular membrane of blood capillaries. Tubular reabsorption take place by two mechanisms:  Active reabsorption,  Passive reabsorption Active reabsorption requires energy which is provided by the hydrolysis of ATPs. The tubules contain numerous sodium-potassium ATPase pumps.

23. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.23 Urine Formation-9  The ATPase pump transport the sodium ions out of cells into interstitial space and potassium from the interstitial space into the cells at the expense of hydrolysis of ATP molecules.  The transport of sodium ions out of the cells causes low concentration of sodium ions and development of negative electric potential inside the cell.  The low concentration of sodium ions and negative electric potential inside the cells causes the diffusion of of sodium ions from the tubular lumen into the cells.

24. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.24 Urine Formation-10  Glucose and amino acids are also transported by the active reabsorption method.  In the glucose and amino acid transport the energy released after the diffusion of sodium ions is used to transport the glucose and amino acid molecules into the cells of tubules.  Some kind of proteins carriers molecules are also involved in the transport of glucose and amino acids.  The rate of absorption of glucose and amino acids is dependent on the maximum capacity limits of carrier proteins and ATPase pumps.

25. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.25 Urine Formation-11  The reabsorbing capacity of nephrons for glucose is 375 mg/min.  As described before the active reabsorption of sodium causes reabsorption of glucose, amino acids, chlorine and urea.

26. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.26 Urine Formation-11  Tubular secretion:- The secretion of most of the toxic metabolites from blood into the urine take place in proximal tubule. Thus the proximal tubule mostly involved in excretion function. The metabolic toxic such as bile salts, organic acids, oxalate, urate and catecholamines are excreted by proximal tubule into the glomerulus filtrate. The proximal tubules also secrete some drugs such as penicillin and salicylates (Aspirin,Dispirin) more rapidly into the filtrate. The proximal tubule also secrete para- aminohippuric acid(PAH) very fast; therefore the rate of clearance of this substance is used to measure renal plasma flow.

27. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.27 Critical Thinking Question  Why protein rich diet give more load on kidney filtration?

28. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.28 Tips for Critical Thinking Question  Absorption of proteins and amino acids by kidney is energy expensive process.

29. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.29 What We Learn…..  Structural and functional aspects of kidney.  Nephrons.  Reabsorption mechanisms of glucose, sodium, amino acids and proteins.  Mechanism of urine formation in kidney.

30. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.30 Study Tips  Book Title:Textbook of medical physiology. Dr. Arthur C. Guyton, John E. Hall. Author: Dr. Arthur C. Guyton, John E. Hall. Publication: Elsevier India Private Limited.  Book Human Physiology Title: Human Physiology C. C. Chattergy. Author: C. C. Chattergy.

31. End of the Presentation Thank You!