1. The Human Excretory System (Urinary System)

2. Roles & Functions of the Excretory System (Kidneys)
Roles (What does the kidney do for the body?)
Functions (How is each role done?)
Excretion: removal of wastes from blood
Homeostasis: condition in which all cellular levels and processes are in equilibrium, and operating at optimal levels
Osmoregulation: regulating pH by controlling the amount of the amount of salt and other solutes that are dissolved in your blood
Filtration of blood
Selective reabsorption by active AND passive transport
Secretion

4. Organs of the Excretory System
Ureters connect the kidneys to the bladder
Urethra transports wastes out of the body
Works with the liver, transport, digestive, nervous, and endocrine systems.

7. Internal Anatomy of the Kidneys
Source: sy/images/urisys.19.gif

9. Nephrons are the functional units of the kidney

10. Each Kidney Consists of About 1 Million Nephrons
Structure of a nephron

11. Structure of the Nephron
The glomerulus and Bowman’s Capsule produce a filtrate from the blood by ultrafiltration
The proximal convoluted tubule transfers useful substances from the filtrate back in to the blood by selective reabsorption
The loop of Henle establishes high solute concentration in the medulla, so that hypertonic urine can be produced ; involves osmosis and active transport.
The distal convoluted tubule is the final site of selective reabsorption
The collecting duct feeds into the ureter and is where osmoregulation occurs.
The vasa recta is a blood network that reabsorbs materials from the filtrate.

12. How does blood move from the glomerulus into the nephron?
Narrow blood vessels cause high pressure
Fenestrations (pores) in the blood vessels allow blood to move into the nephron more easily

13. Modes of Transport in the Nephron

14. Methods of Transport Passive Transport: Active transport:
Water (osmosis)
Salt (Bottom of Loop of Henle)
Active transport:
Salt (Tubules & Ascending Limb)
Other Ions (Tubules)
Glucose, amino acids (Proximal Tubule)
Toxins

16. Kidney Stones
greater-risk-for-developing-kidney-stones

18. Role of the Collecting Duct and ADH
ADH = anti-diuretic hormone (released by the pituitary gland in the brain)
ADH causes the collecting duct to be more permeable to water (by addition of aquaporins) so that more water is reabsorbed back into the blood
ADH is released when you are dehydrated ; and suppressed when you are sufficiently hydrated

19. Role of ADH in Osmoregulation

20. Why do certain substances make you pee more often!?

21. Lifestyles Correlate with Evolutionary Trends
Osmoconformers maintain internal conditions that are equal to the osmolarity of their environment (Examples: most aquatic invertebrates)
Osmoregulators keep their body’s osmolarity constant, regardless of environmental conditions (Examples: fish, most vertebrates)

22. Nitrogenous Waste in Animal Groups

23. Excretion in Insects via Malphigian Tubules
Insects have a circulating fluid system called hemolymph that is analogous to the blood system in mammals
Malpighian tubules branch off from the intestinal tract and actively uptake nitrogenous wastes and water from the hemolymph
The tubules pass these materials into the gut to combine with the digested food products
Solutes, water and salts are reabsorbed into the hemolymph at the hindgut, whereas nitrogenous wastes (as uric acid) and undigested food materials are excreted via the anus