1. The Excretory System

2. Excretory System
Some call it the “urinary system”, but more than just urine is excreted from our bodies
Excretion = removing unnecessary components from an organism
Examples:
Lungs excrete CO2
Skin excretes ions/salts in the form of sweat
Kidneys excrete urine
We are gong to focus on this part of the excretory system

3. Major Function Disposing of wastes and excess ions
Regulation of blood volume and chemical makeup
Regulation of blood pressure
Manufacturing and storage of urine

4. Organs Kidney Ureters Urinary Bladder Urethra Form urine
Tubes that connect kidney to bladder and transport urine
Urinary Bladder
Store urine
Urethra
External opening to the body where urine passes
In males, the urethra does double duty and can pass semen AND urine

5. Kidneys Located in the upper lumbar region
Protected by the 12th rib
Adrenal gland sits atop the kidney
When cut lengthwise, it has 3 regions

6. Kidney-Regions Renal cortex Renal medulla Renal pelvis Outer region
Contains “medullary pyramids”
Renal pelvis
Connects to ureters that will send urine to the bladder

7. Nephrons Each kidney contains over a million nephrons
Nephron = structural and functional unit of the kidney
Responsible for forming urine

8. Nephron Each nephron consists of 2 main structures Glomerulus
Knot of capillaries
Renal tubule
Glomerular capsule
Proximal convoluted tubule
Loop of Henle
Ascending and descending loops
Distal convoluted tubule
Collecting duct

10. Urine Formation 3 processes
Filtration
Tubular reabsorption
Tubular secretion
Rule of thumb: whatever is not reabsorbed from the nephron will be found in the urine

11. Filtration
The glomerulus acts as a filter and the filtrate goes into the glomerular capsule
Will eventually be found in urine if not reabsorbed
Filtration = nonselective passive process
Only salts, glucose, urea, amino acids can pass through into the glomerular capsule
Proteins and RBCs = too large

12. Tubular Reabsorption
Begins as soon as the filtrate enters the proximal convoluted tubule and continues through all the tubes
Salts, amino acids, and water are reabsorbed back into the bloodstream

14. Tubular Secretion Essentially reabsorption in reverse
The body is trying to get rid of these substances
Hydrogen, potassium, certain drugs
Whatever is left in the nephron will go into the collecting duct and will eventually exit the body

16. What’s Next?
The filtrate that passes through the collecting duct will drain into the renal pelvis
It is called “urine” at this point
This is connected to the ureters and will transport the urine to the urinary bladder
When voided, the urine will pass through the urethra and into the outside world

17. Let’s Talk About Pee Every 24 hours, 1-1.8 liters are produced
Urine = nitrogenous wastes and unneeded substances

18. Characteristics of Urine
Generally clear and pale- to deep-yellow
Why is urine yellow?
From a pigment called urochrome that results from the body’s destruction of hemoglobin
When formed, urine is sterile
Means there is no bacteria
Why does urine smell?
The longer the urine sits, it gets exposed to bacteria and they eat the urine solutes and cause the ammonia odor

19. Characteristics of Urine
Urine pH is slightly acidic, but this can vary based on diet
Lots of protein and whole-wheat products? ACIDIC
Vegetarian diet? BASIC

20. Characteristics of Urine
Composition
Sodium, potassium, urea, uric acid, creatinin, ammonia, bicarbonate ions
Things that should NOT be found in urine:
Glucose, blood proteins, RBCs, hemoglobin, WBCs, and bile