1. Advanced Biology | Chapter 26
The Urinary System
Advanced Biology | Chapter 26

2. The Urinary System Includes: Kidneys – urine forming organs
Urinary bladder – temporary storage reservoir for urine
Ureters and urethra – tube-like organs which transport urine

3. Kidney Anatomy Bean-shaped Protected by lower rib cage About 150 g
About 12cm × 6cm × 3cm

4. Kidney Anatomy
Adrenal glands rest on top of the kidneys but are not part of the endocrine system
Kidneys are surrounded by three layers of tissue:
Renal capsule – fibrous; adheres to the kidney directly
Adipose capsule – helps attach kidneys to posterior body wall and cushions against blows
Renal fascia – dense fibrous connective tissue; surrounds kidneys; hold adrenal glands in place

5. Internal Anatomy Three main regions of a kidney:
Renal cortex – light in color; granular appearance; outer covering of kidney
Renal medulla – thickest part of the kidney; contains renal pyramids (medullary)
Renal pelvis – site of entry for renal veins and arteries and ureters

6. Blood and nerve supply
Renal arteries – deliver blood to the kidneys to be filtered
Renal veins – take blood away from the kidneys and back to the inferior vena cava
Nerve supply is from the renal plexus

7. Nephrons Main player of the kidney One million per kidney on average
Parts:
Glomerulus
Glomerular (Bowman’s) capsule
Proximal convoluted tubule (PCT)
Loop of Henle:
Descending limb – thin segment
Ascending limb – thin and thick segment
Distal convoluted tubule (DCT)

8. Nephrons Glomerulus is under high pressure
1/5 of fluid is squeezed out into Bowman’s capsule
Squeezes out:
Small ions
Glucose molecules
Amino acids
Does not squeeze out:
Red blood cells

9. Nephrons Proximal convoluted tubule Near the beginning of the nephron
Begins reabsorbing “good stuff”; uses active transport
Glucose
Amino acids
Some sodium (Na)
Some water

10. Nephrons Loop of Henle Crosses into the renal medulla from cortex
Descending limb:
Only secretes water because the medulla is hypertonic
Ascending limb:
Wants to increase the salts in the medulla by active transport of Na, K, Cl
Makes the medulla hypertonic

11. Nephrons Distal convoluted tubule Further away from the beginning
More reabsorption of calcium and other electrolytes
Tubule then contains concentrated water and wastes
Dumps into collecting ducts

12. Nephrons Collecting duct Runs back into the medulla
Hormones (antidiabetic hormones) causes or allows more water to be reabsorbed and concentrates wastes even more

13. Nephrons

14. Table 26.1