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PP 3 Excretion in Humans. Define excretion  the removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells.

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Presentation on theme: "PP 3 Excretion in Humans. Define excretion  the removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells."— Presentation transcript:

1 PP 3 Excretion in Humans

2 Define excretion  the removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances (carbon dioxide, urea and salts) in excess of requirements.

3 the function of the kidney: removal of urea /excess water / the reabsorption of glucose and some salts  Urea: - Made in liver (from excess of proteins / a.a) - A. a. are absorbed into blood and go via the hepatic portal vein to the liver - AA in liver: 1. Pass through / pass into cells and cells use it to make proteins 2. Liver itself uses it (makes fibrinogen) 3. Excess is broken down by the liver – changed to carbs or fats for storage This requires the N part of a.a. to be removed *** Alcohol / drugs and hormones are also broken down in liver

4  Deamination – removal of Nitrogen from a.a.  - N containing part made into urea (nitrogen excretory product)  Urea is carried away from liver in blood to kidneys  Kidney’s filtering system: - Plasma is filtered into kidney - Useful substance (glucose / ions (NaCl) are taken back to blood (reabsorption) - Urea kept in kidney

5  Urine – urea in water.  Too much water in body is excess – also removed in urine  If there is not enough water in body – only little water will flow out as urine and the majority of it will be taken back into blood  Urine: water + salts + urea - urea, uric acid, ammonia, hormones, dead blood cells, proteins, salts and minerals, and toxins

6 Urine flows through here into Bladder Urine is released here After it is left the bladder

7 Outside part Inside part Both contain tiny tube = kidney tubules (start in cortex as renal capsule

8 Kidney StructureFunction Renal capsule Blood is delivered here and flows through a capillaries network blood plasma is squeezed through wall of capillary wall of capsule into the cavity inside the kidney tubule Blood plasma passes through filter It does not pass through: cells / big proteins Molecules that pass through: water, urea, glucose, ions : sodium & chloride Renal Tubule As fluid flows through tubule - anything useful is reabsorbed into the blood (not lost from body) Water is removed from the tubule Ureter collects excess water / salts / urea = urin

9 1. Blood vessels bring blood into tubule 2. In the renal capsule plasma filtered into tubule 3. 1 st part of tubule where Glucose / water / salts are Reabsorbed 4. Blood vessels take blood away from tubules 5. Last Portion Where Water Can be Reab- sorbed if Body need

10 Kidney Dialysis  Kidney stops working (infection / trauma / genetics)  Kidney no longer can remove urea / excess water  Feeling ill ->death  2 options : Kidney Transplant or if possible Kidney Dialysis  Dialysis: filtering patients blood (like the kidney does) using a Kidney Dialysis Machine by passing blood through it. - The process of diffusion of different molecules each according to its own concentration gradient though a partially permeable membrane

11 How dialysis works  blood passes through tiny channels in dialysis tubing in machine  Dialysis tubing allows only certain molecules though because of the size of holes (very small – molecule size) that the tubing is made of.  Smalls molecules can pass though – water / urea/glucose can pass through  Large molecules like proteins can not

12  Dialysis fluid – the liquid outside the dialysis tubing - This made to have similar composition of healthy human blood plasma (water / glucose / salts – but no urea) - It is sterile (no germs) - Dialysis fluid flows in 1 direction in the machine - Patients blood passes in the opposite direction - Fluid and blood will diffuse down its concentration gradient

13  Therefore:  - No urea in dialysis fluid -  urea in patients blood will diffuse out of the patient and into the dialysis fluid  If more water in blood than in dialysis fluid then water will diffuse out of blood of patient  If the opposite is true – then water will flow in from the dialysis tubing into the patients blood (same for salt and glucose)  Problems: - This needs to be done several times a week for several hours - Can make people feel sick / must be careful of what they eat /  Positive: - cheaper than transplant

14 How Dialysis works

15 Kidney transplant  Kidney taken from a donor and placed in a recipient  Problems: - not enough kidneys for number of donors - Must come from healthy donor - Cells or donor kidney must be similar to recipient’s - Immunosuppressant drugs are still needed Positive: - if transplant is successful – then kidney function is restored


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