1. Urinary System

2. Four major structures
Kidneys
Ureters
Urinary bladder
Urethra

3. Kidneys
Organ that produces urine
Performs other functions
Contains nephrons
microscopic structure that produces urine

4. Left kidney lies in the upper ABD behind the spleen
Right kidney lies behind the liver
Located at what we call the flank area
Hilum
Where the renal artery, nerves, lymphatic vessels, and ureter pass into the kidney

5. Nephrons
In a young adult there are aprox. One million
We loose 10% per decade after age 40

6. Cortex
The outer tissue region of the kidney
Medulla
The inner tissue region of the kidney
Pyramids
Medulla is divided into fan-shaped regions
Papilla
Where the pyramids terminate
Casts into the renal pelvis a hollow space

7. The spaces of the pelvis come together at the derivation of the ureter
Urine forms in the cortex and medulla and leaves the kidney through the renal pelvis and the ureter

8. Nephron
Functional unit of the kidney
Forms urine
Consists of a tubule
Each tubule is divided into parts of a different structure and capillaries which form a complex net of vessels that covers the surface of the tubule

9. Glomerulus
Capillaries that filter blood into a nephron
Bowman’s capsule
First part of the nephron tubule that is a cup-shaped, hollow structure

10. Water and chemical substances enter the tubule through the bowman’s capsule and after passing through the successive parts of the tubule proximal tubule
descending loop of henley
ascending loop of henley
distal tubule
Urine drips in the collecting duct before entering the renal pelvis and ureter

11. Nephron Physiology

12. Major functions of the kidneys
forming urine
eliminating urine
Entails
Maintaining blood volume with proper balance of water,electrolytes and pH
Retaining glucose while excreting waste such as urea

13. Controlling arterial blood pressure
relies both on urine formation and another mechanism that does not involve formation of urine
Kidney cells regulate erythrocyte development ; does not involve urine formation

14. First step in urine formation
filtration of blood
Blood flows through the capillaries of the glomerulus and water and numerous chemical materials are filtered out into the Bowman’s Capsule
Blood cells and plasma proteins are not filtered as they are too large to pass through into the capsule

15. Filtrate
Fluid after the filtration process
Blood is filtered at a rate of 180L/day
Thus urea and drug metabolites can be filtered so quickly that they don’t accumulate in the blood
The process of reabsorption and secretion maintain homeostatis of the body

16. Reabsorption and Secretion
Intracellular transport
simple diffusion
facilitated diffusion
active transport

17. Simple diffusion
Molecules small enough to permiate the cell membrane randomly move in and out of the cell
Requires no energy
Higher [ ] to lower [ ] equalizes both sides

18. Osmosis
the movement of water to equalize [ ] on both sides of the membrane
Osmolarity
When particles are dissolved in water they move so that the [ ] is equal on both sides

19. Facilitated diffusion
A molecule-specif “helper” or carrier acts as a tunnel and speeds the molecule along and through the membrane
i.e.
Glucose
When insulin binds to a glucose-specific carrier, it can pass 10x quicker than without insulin

20. Active transport {“uphill”}
Net movement of lower to higher [ ].
Requires E
Essential for homeostasis by handling electrolytes and glucose as well as other substances

21. Water and Electrolytes
Na+ K+ H+
Cl-
The handling of water and electrolytes is the footing for control of blood volume and electrolyte balance

22. Maintaining blood volume
Na+ is the main cation in extracellular fluid whereas K+ is the main cation in intracellular fluid
Appropriate retention of Na+ along with osmotic retention of water

23. Electrolyte and pH balance
Retention of K+ and Cl- So

24. Filtrate formed in the Bowman’s capsule enters the proximal tubule.
65% of Na+ and Cl- is reabsorbed as well as osmotic reabsorption
At the same time H+ is secreted which through a process determines the pH of venous blood leaving the kidneys as well as the excreted urine
20% of water in the filtrate is reabsorbed

25. Diuresis
Formation and passage of a dilute urine, decreasing blood volume

26. Handling of Glucose
Freely filtered into the Bowman’s capsule
Reabsorbed before filtrate enters the proximal tubule
Retained to a certain level then glucose is lost in urine
When there is so much glucose in the filtrate reabsorption becomes insufficient so not only is glucose lost in but large amounts of water as well

27. Control of arterial blood pressure
The balance of water and electrolytes thus maintaining blood volume
Juxtaglomerular cells respond to low blood pressure by releasing the enzyme renin
Renin then produces the hormone angiotensin I
Angiotensin I flows through the lungs and by process produces Angiotensin II

28. So how do these all come into play. . . .?
Angiotensin II acts on both kidney tubular cells and on adrenal cells
Adrenal cells produce aldosterone
So how do these all come into play ?

29. Aldosterone
Target tissue; distal tubule
collecting duct
Effects increases reabsorption of Na+, Cl- and water

30. Angiotensis II
Target Tissue; Proximal tube
Effects: increases reabsorption of Na+, Cl- and water
increases secretion of H+