1. 9.5 Excretory System

2. Learning GOals Learn and use the vocabulary
Describe the anatomy of excretory system
Describe how it works
Know how this system maintains homeostasis
Know how a change in the environment will affect this system (i.e. Drinking more or less, filtering toxins etc.)
Pg and

3. Excretory System Function
Excretory systems needed to concentrate wastes and then excrete toxins into environment
Regulates fluids and water within the body

4. Other Organisms Unicellular organisms can excrete toxic wastes via:
Diffusion directly with environment
Ex. Paramecium and contractile vacuoles (pump water out actively maintaining osmotic balance)

5. Terrestrial animals - Multicellular organisms need organ systems because they’re too large for diffusion to be efficient

6. Invertebrate Excretory Systems
Metanephridium is a system of tubes and nephridopores that reabsorbs and excretes wastes out of worms

8. Invertebrate Excretory Systems
Malpighian Tubules: system of tubes that deliver wastes to intestines in insects via reabsorption and excretion

9. Birds and Some Reptiles
Excrete salt through glands on nose especially in salty environments

10. Human excretory system
The major organ of this system is the kidney which is made up of specialized tubules called nephrons
Other parts of the system include the bladder, the ureters and the urethra
Wastes are filtered from the blood by the kidneys and passed to the bladder by the ureters
The bladder have stretch receptors that send signals to the brain to let you know you have to urinate
Urine passes through the urethra to exit the body

11. Human excretory system
Renal = of the kidneys

12. Nephron
Nephron is a microscopic unit of filtration in the kidney; acts like sieve for reabsorption and excretion of wastes
Kidney contains millions of them

13. nephron
The nephron is divided into regions that carry out specific steps involved in excretion:
Blood enters nephron and collects in glomerulus
The glomerulus is a capillary bed where waste moves from bloodstream into the Bowman’s Capsule and then into the Proximal Tubule

14. Filtrate enters the Proximal tubule
Peritubular capillaries surround the entire nephron to reabsorb substances back into the blood
Urine is formed in the nephron tubes

15. The proximal tubule leads to the Loop of Henle which helps reabsorb any useful materials (H2O, Na+, Cl- etc.) into the bloodstream
The loop of henle leads to the Distal tubule and eventually to the Collecting ducts
Collecting ducts drain into the renal pelvis
Urine leads to ureters then bladder

16. Urine Formation: 3 steps
1. Filtration
2. Reabsorption
3. Secretion

18. Step 1. Filtration
Fluids from the blood move through the afferent arteriole into glomerulus
The capillaries of the glomerulus are under high pressure forcing dissolved solutes to move into Bowman’s Capsule from high to low pressure
Water, sodium chloride (NaCl), glucose, amino acids, and hydrogen ions (H+) will move through the wall of the glomerulus
But plasma proteins, blood cells, and platelets are too large and stay in the capillaries

19. Label where Filtration occurs in the image in your notes.

20. Step 2. Reabsorption
Must reabsorb some substances from the filtrate that enters the nephron—otherwise we’d urinate 120mL per minute!
Only 1 mL of urine is produce per 120mL of filtrate entering nephron

21. Step 2. Reabsorption
Selective reabsorption so that only particular substances stay in the body
Filtrate enters the proximal tubule
H2O, ions and nutrients transferred back to interstitial fluid using both active and passive transport
Active:
Active ion pumps transport K+, Na+, & Cl- from filtrate into the fluid surrounding the tubule
Glucose and amino acids are reabsorbed using active transport proteins

23. Step 2. Reabsorption
The reabsorption process makes the filtrate hypo-osmotic to the interstitial fluid causing water to flow out of the tubule into the interstitial fluid by osmosis
Movement of water can also be facilitated by membrane proteins called aquaporins

24. Step 2. Reabsorption
The remaining filtrate (urea & other wastes) move into the descending Loop of Henle where additional water is reabsorbed
In the ascending Loop of Henle more Na+ and Cl- are reabsorbed into the interstitial fluid using active and passive transport
The filtrate now moves into the distal tubule where additional water and salts are removed
Lastly, the filtrate moves into the collecting ducts where more water can be reabsorbed and then exits through the kidney to the bladder

26. Step 3. Secretion
Is the removal of wastes from blood and interstitial fluid
This occurs in the proximal, distal tubules and the collecting ducts
Nitrogen-containing wastes, excess H+ ions, detoxified poisons (ex. Alcohol, medications...), and other minerals (K+) are balanced by secretions from the interstitial fluid into the nephron

28. Kidney Stones When calcium deposits build up in the kidneys
Blocks urine flow
Very painful to pass

29. History Is Cool Lithotomy is one of the first surgeries
Removal of kidney stone through cut between anus and scrotal sack
No anaesthetic or doctors—barber surgeons until 1800s

30. Dialysis When kidneys malfunction machines are used instead
Patient must sit for hours several times a week to filter their blood artificially

31. Urinary System Game
The class will be split into 2 teams and you will compete against each other to see if who completes this task first.
Each person in your group will be assigned a part of the urinary system and must put it together from start to finish.
When one team is done you will need to present it in order to me. One student can represent the wastes and flow through the system with each student explaining their function as they travel along.

32. Success Criteria
Can you fill in the matching sheet and draw out the pathway?
Can you fill out the table to determine the function of each section?
Table 1 on page 342 is a great summery you should know.