1. 16.1 Intro to the Excretory System

2. Systems The excretory system includes:
Respiratory system (already studied)
Circulatory system (already studies)
Urinary system (focus of this unit)
Integumentary (skin) system (brief intro in this unit)

3. Main Functions of Urinary System
To maintain homeostasis by:
Removing metabolic waste products, notably nitrogenous waste from breakdown of amino acids:
Urea
Creatine
Uric acid
Maintaining water-salt balance
Kidneys perform this function
Blood volume and blood pressure are closely connected
More salts = more blood volume = higher blood pressure

4. Main Functions of Urinary System
Maintaining acid-base balance
Kidneys perform this function
Monitor and maintain blood pH at 7.4
Excrete H+ ions and reabsorb HCO3- ions as needed
Secretion of hormones
Kidneys excrete renin (hormone) that stimulates the excretion of aldersterone.
Aldersterone promotes the reabsorption of Na+ ions in the kidneys
Kidneys secrete eruthropoietin, which stimulates red blood cell production

5. Organs of Urinary System
A. Kidney 1. Bean-shaped 2. Located between peritoneum and the back muscles 3. Renal pelvis – funnel-shaped structure at the beginning of the ureter 4. Medulla a, Inner, striated layer b. Striated cones are renal pyramids c. Base of pyramids empty into cuplike cavities called calyces 5. Cortex – composed of millions of microscopic nephrons

6. Organs of Urinary System
B. Nephron – functional unit of kidney
1. Bowman’s capsule
2. Glomerulus
3. Proximal convoluted tubule
4. Loop of Henle
5. Distal convoluted tubule
6. Collecting tubule
C. Ureters
1. One from each kidney
2. Smooth muscle tube with mucous membrane lining

7. Organs of Urinary System
D. Urinary bladder
1. Hollow, muscular organ
2. Made of elastic fibers and involuntary muscle
3. Stores urine – about 500 cc
E. Urethra
1. Connects bladder with urinary meatus
2. Urinary meatus is opening to body