1. Urine formation in Excretory System
SBI 4U: Metablic Processes
Urine formation in Excretory System
Chapter 10.1 & 10.2
McGraw-Hill Ryerson
Biology 12 (2011)
Section 1.3

2. Simple Excretory Systems
SBI 4U: Metablic Processes
Simple Excretory Systems
Unicellular organisms get rid of wastes by the use of a contractile vacuole.
It expels excess water that enters the cell through osmosis since the organism is hypertonic to the surrounding solution.
Section 1.3

3. Complex Excretory Systems
SBI 4U: Metablic Processes
Complex Excretory Systems
More complex organisms (multicellular, or living on land) need to store wastes and use special cells that are in the excretory system to remove wastes from the body.
Section 1.3

4. Organs of the Excretory system
SBI 4U: Metablic Processes
Organs of the Excretory system
Lungs: gas waste, i.e. CO2
Colon: solid wastes from the digestive system
Kidneys: water-soluble waste, as well as regulation of body pH and water levels.
Section 1.3

5. SBI 4U: Metablic Processes
Processing of Wastes
The liver transforms ingested toxins such as alcohol, heavy metals and waste from protein metabolism into soluble compounds that can be removed by the kidney:
Section 1.3

6. SBI 4U: Metablic Processes
Water soluble wastes
Ammonia: produced by protein metabolism. It is very toxic so the liver converts it to...
Urea (100,000x less toxic than ammonia)
Uric acid comes from the metabolism of nucleic acids. Less soluble than urea; a build of uric acid can lead to kidney stones.
Section 1.3

7. SBI 4U: Metablic Processes
The Urinary System
Wastes are filtered from blood into the kidneys and sent to the bladder.
Renal arteries pass blood to the kidneys.
Ureters pass urine to the bladder.
Be sure you can label this diagram!
Section 1.3

8. SBI 4U: Metablic Processes
The Urinary System
Urinary sphincter controls the release of urine from bladder.
Urethra is the tube used to void the bladder.
200 mL of urine  bladder expands  stretch receptors send a signal to the brain. You choose whether to void (voluntary control over sphincter)…to a point.
Section 1.3

9. SBI 4U: Metablic Processes
Kidney Structure
Cortex: outer layer of connective tissue
Medulla: inner layer under the cortex
renal pelvis: hollow chamber which connects the kidney with the ureter
Take a minute to memorize this diagram.
Section 1.3

10. SBI 4U: Metablic Processes
NEPHRON
Nephrons: approximately one million small functional units of the kidney spanning the cortex and the medulla
They are comprised of specialized blood vessels and tubes that wrap around each other for filtering wastes from the blood and producing urine.
Section 1.3

11. Microscopic Anatomy of the Kidneys
Filtration
Filtrate of blood leaves kidney capillaries
Reabsorption
Most nutrients, water, and essential ions reclaimed
Secretion
Active process of removing undesirable molecules

12. SBI 4U: Metablic Processes
The mammalian nephron
This nephron has been spread out.
BLUE= tubes RED = blood vessels
Section 1.3

13. Blood flow in the Nephron
SBI 4U: Metablic Processes
Blood flow in the Nephron
Afferent arterioles supply blood to the kidney from the renal artery. They end in a capillary network or capillary bed called the glomerulus.
Section 1.3

14. Blood flow in the Nephron
SBI 4U: Metablic Processes
Blood flow in the Nephron
Blood exits the glomerulus through efferent arterioles that lead to a network of peritubular capillaries which surround the tubules of the nephron.
Section 1.3

15. Blood flow in the Nephron
SBI 4U: Metablic Processes
Blood flow in the Nephron
They collect into the renal venules and blood exits the kidney through the renal vein.
Section 1.3

16. Fluid Flow in the nephron
SBI 4U: Metablic Processes
Fluid Flow in the nephron
The glomerulus is surrounded by the Bowman's capsule. It, along with the afferent and efferent arterioles and the glomerulus are in the cortex of the kidney.
Section 1.3

17. Fluid Flow in the nephron
SBI 4U: Metablic Processes
Fluid Flow in the nephron
Fluids that are to be processed as urine enter the Bowman's capsule from the blood in the glomerulus.
Section 1.3

18. Fluid Flow in the Nephron
SBI 4U: Metablic Processes
The Bowman's capsule leads to a thin tubule called the proximal tubule.
Proximal tubule use active transport to bring Na, glucose, and other solutes back into the blood
Negative ions tag along back to blood due to attraction
Water follows the ions by osmosis back into blood
Section 1.3

19. Fluid Flow in the Nephron
SBI 4U: Metablic Processes
Fluid Flow in the Nephron
Urine goes from the proximal tubule around the loop of Henle, which descends into the medulla of the kidney then ascends to the cortex.
Function is to reabsorb water and ions back to blood
Medulla is very salty so water diffuses by osmosis in descending loop
Ascending loop is impermeable to water so solutes diffuse
Thick segment of ascending limb actively transports Na in blood
Section 1.3

20. Fluid Flow in the Nephron
SBI 4U: Metablic Processes
Fluid Flow in the Nephron
Urine then moves through the distal tubule
K ions are actively secreted from blood
H+ are actively secreted from blood to maintain blood pH
Other substances not normally part of body are secreted
Section 1.3

21. Fluid Flow in the Nephron
SBI 4U: Metablic Processes
Fluid Flow in the Nephron
Urine moves into collecting ducts, which collect urine from many nephrons and lead into the renal pelvis of the kidney.
Filtrate still possesses lots of water
Permeability to water being reabsorbed is increased depending on concentration of blood plasma (i.e. dehydration leads to increased permeability meaning more reabsorbtion)
Section 1.3

22. Identify the structures:
SBI 4U: Metablic Processes D
Collecting ducts
Bowman’s Capsule
Proximal tubule
Distal tubule
Loop of Henle
Glomerulus
Peritubular Capillaries
Renal venule
Renal vein
Renal artery
Afferent arteriole
Efferent arteriole I K C B L A G H F E J
You can refer to page 447 of your textbook for help
Section 1.3

23. Homework
Pg 448 #4, 5, 6, 7, 8
Pg 455 #2-5, 11, 12
Be sure to look at Table 10.3 on pg 454!!