1. The Excretory System

2. This is not egestion which is the removal of undigested food or feces
Function:
Removal of metabolic wastes and excess substances from cellular activities that build up in bodily fluids
This is not egestion which is the removal of undigested food or feces

3. Major Metabolic Wastes Carbon Dioxide
produced from cellular respiration
Nitrogen Compounds
produced by the breakdown of amino acids
Ammonia, urea, uric acid
Mineral Salts
Water

4. Disposed of in urine and sweat

5. Organs of Excretion Kidney Liver Lungs Skin
These organs work with the circulatory, nervous and endocrine systems to help keep the body’s internal environment constant and maintain homeostasis

6. The Kidneys and the Urinary System
Composed of:
Kidneys
Ureters
Bladder
Urethra

7. Summary: Kidneys produce urine which passes to a tube called a ureter
Urine flows to the urinary bladder where it is stored.
During urination the stored urine travels from the bladder to the outside of the body through the urethra
Helps to maintain a proper fluid balance in the body

8. Structure of the Kidney
Cortex: outer part where blood is filtered
Medulla: middle part made up of tubes called collecting ducts that carry filtrate to pelvis
Pelvis: inner region connected to ureter

9. Kidney Function Filters the blood Primary organ of “Osmoregulation”
(regulating water balance)

10. The Nephron Part of the kidney where filtering of the blood happens
Each kidney has over a million nephrons
Part of nephron lies in cortex, part in the medulla

11. Filtration and Reabsorption in the Nephron
Renal vein
Renal Artery
Glomerulus
Collecting duct for urine
Bowman’s Capsule
Loop of Henle

12. Parts of the Nephron Glomerulus: Bowman’s Capsule:
group of capillaries in a tight ball at end of nephron
Where substances filter out of blood and enter nephron as “filtrate”
Bowman’s Capsule:
cup shaped structure that surrounds the glomerulus and receives filtrate from blood

13. Loop of Henle (Renal Tubule)
Long loop of the nephron
Surrounded by capillaries
Reabsorption of certain parts of filtrate back into the bloodstream takes place here.
Materials reabsorbed from filtrate

14. How is Urine Formed? Process of filtration and reabsorption
Filtration of materials from blood
Reabsorption of certain useful substances

15. Filtration:
Blood enters kidney under pressure forcing filtrate through thin walls of glomerulus into Bowman’s Capsule
Filtrate:
Composed of water, urea, glucose, amino acids, various salts

16. But: We need a lot of this fluid back!
Otherwise we lose too much water, glucose and salts
On average about 180 liters of filtrate is formed in 24 hours but only 1 to 1.5 liters of urine is produced!

18. Reabsorption: takes place in renal tubule (Loop of Henle)
Returns 99% of filtrate back to the blood
Most of the water
By passive transport
Glucose, amino acids and most of the salts
Mostly by active transport

19. Urine: made of urea, water and excess salts
Way to conserve water
Way to keep nutrients like glucose and amino acids
Filtrate becomes very concentrated as urine
Urine: made of urea, water and excess salts

21. Interactive showing Nephron Function and what is filtered and reabsorbed:

22. The Excretory System and The Nephron

23. Regulation of Urine Output
Hypothalamus (small area of brain)
Secretes hormone called ADH (antidiuretic hormone)
Fluid intake low = ADH secreted
Stimulates reabsorption of water in nephron.
Urine output decreases and is more concentrated
Fluid intake high: ADH not secreted
Less reabsorption of water in nephron
Urine output increases and is relatively dilute

24. Kidney Disorders Kidney Stones:
found when substances crystalize out of urine
may may block kidney, ureters, bladder

25. Uremia: Kidney Dialysis:
urine and other wastes are not filtered out of blood, poisoning cells
Kidney Dialysis:
when the kidneys fail, excess fluids and wastes accumulate in blood.
use artificial kidney to filter blood

26. Gout: uric acid crystals are produced and accumulate in joints
Similar to arthritis

27. Crash Course on the Excretory System
Tutorials on Kidney and Nephron Function:

28. The Liver
Helps to filter the blood and regulate the makeup of body fluids

29. Breaks Down Worn Out Red Blood Cells
Detoxifies Blood
Removes substances such as drugs, alcohol and certain toxins from the blood
Changes them to an inactive form which is excreted from the body by kidneys
Breaks Down Worn Out Red Blood Cells
RBCs don’t have nuclei and don’t live very long
Part of the hemoglobin molecule is found in bile.

30. Excretes Bile:
the liver synthesizes and excretes bile into gall bladder to add in fat digestion

31. Forms Urea
Excess amino acids from protein digestion are broken down in the liver by deamination.
Deamination:
“amino group” is removed from amino acid
changed to ammonia NH3
ammonia is toxic to the body and is changed into urea in the liver
Kidneys filter out urea in the nephron and excrete it from the body in urine.

32. Diseases of the Liver Cirrhosis:
disease caused by overloading liver with harmful materials such as alcohol
Liver becomes enlarged and overgrown with excess tissue

33. Jaundice: Bile is not secreted properly
Reabsorbed hemoglobin fragments form bilirubin in the blood and make the skin look jaundiced or yellow

34. Lungs An excretory organ
Give off carbon dioxide, and excess water both metabolic wastes.

35. Skin
Gives off sweat or perspiration to help regulate body temperature.
Sweat is composed of 99% water, salts and some urea.
Also capillaries close to skin surface help to eliminate or conserve heat.

36. Skin Skin is the largest organ of the human body.
It protects the inner organs and tissues of the body, and has sensory cells to help us detect changes in our environment.
It also has sebaceous glands that produce oil that help protect skin and keep it soft and pliable.

37. Comparative Excretory Systems in Animals

38. Excretion in Protists and Hydra
Direct contact with cell membrane and environment.
Wastes diffuse out of cell membranes or are excreted through active transport
Metabolic wastes include: carbon dioxide, ammonia and mineral salts
Ammonia is the chief nitrogenous wastes of protists

39. Freshwater protists use contractile vacuoles and active transport to remove excess water that is constantly entering the cell by osmosis.
Concentration of water greater outside cell than inside so it moves across membrane by diffusion into cell.
Salt water protists don’t have this problem.

40. Excretion in Earthworms
Pairs of nephridia found in almost every segment
Surrounded by capillaries and filter wastes from blood
Wastes form a dilute urine which passes through a bladder and out through the nephridiopore.
Urine is water, mineral salts, ammonia and urea.

41. Don’t Forget! Thin outer skin is the respiratory surface
Below skin are capillaries carrying blood with hemoglobin
Live in moist soil and constantly secretes mucus to keep skin moist
If exposed to air and dries out it will suffocate

42. Excretion in Grasshoppers
Malpighian tubules are bathed by blood from open circulatory system
Wastes enter tubules and pass into intestine
Water and other useful substances are reabsorbed and returned to body fluid
Dry nitrogenous waste product: uric acid
Helps conserve water

43. Don’t Forget! System of tracheal tubes for gas exchange
Branching air tubes carry air directly to cells
Muscle contractions pump air in and out of tubes
Spiracles: outside openings that lead to tracheal tubes