1. Chapter 36 BIOL 1000 Dr. Mohamad H. Termos
Excretory System
Chapter 36
BIOL 1000
Dr. Mohamad H. Termos

2. Biology, 9th ed, Sylvia Mader
Chapter 38
Body Fluid Regulation
An excretory system regulates body fluid concentrations
Osmoregulation – maintenance of ion concentrations (in blood)
-Homeostasis!
The concentration of urine produced by an animal varies depending on its environment, as well as water and salt intake
Excretory Systems

3. Biology, 9th ed,Sylvia Mader
Chapter 06
Tonicity
Metabolism
Tonicity – the strength of a solution/ conc. of solutes compared to a cell
Isotonic: solute concentration of solution is equal to the solute concentration of cells =no gain or loss of water
Hypertonic: Solution with greater solute concentration (lower water concentration) than cells =cells lose water
Hypotonic: Solution with lower solute concentration (higher water concentration) than cells = cells gain water

4. Challenges of aquatic environments
Biology, 9th ed, Sylvia Mader
Chapter 38
Challenges of aquatic environments
Body surface is in contact with water  Can easily gain/lose water and solutes. This can be a challenge for organisms
Isotonic: Body fluids are very similar to sea water. Little osmoregulation is needed. Examples: sharks, rays, crabs.
Hypertonic: In marine bony fish body fluids have less solutes than sea water; therefore, they passively lose water through gills (osmosis). Must constantly drink seawater to compensate. Excess salt ions actively transported back into seawater through the gills.
Hypotonic: In freshwater bony fish the body fluids have more solutes than fresh water  Passively gain water through gills (osmosis). Eliminate excess water through copious dilute urine. Salts brought into body via gills
Excretory Systems

5. Biology, 9th ed, Sylvia Mader
Chapter 38
Terrestrial Animals
Terrestrial animals lose water through: Sweat, urine, feces, breathing, insensible perspiration. Must consume water to make up for loss. Water loss is reduced by skin covering, concentrated urine, dry fecal material, and specialized nasal passages
Excretory Systems

6. Biology, 9th ed, Sylvia Mader
Chapter 38
Nitrogenous Waste
Nitrogenous wastes – amino groups that are left when amino acids are broken down
Animals must excrete these:
Ammonia- excreted by aquatic animals. Very toxic.
Urea- excreted by mammals and amphibians and produced in the liver. Less toxic than ammonia. Needs water to excrete.
Uric Acid-excreted by reptiles, birds, and arthropods. Requires much less water than ammonia or urea.
Excretory Systems

7. Biology, 9th ed, Sylvia Mader
Excretory Organs
Chapter 38
They collect and filter water, salts and wastes from body fluids. Concentrate the wastes. Maintain internal fluid homeostasis. Examples: flame cells, nephridia, malpighian tubules, and kidneys.
Flame cells: are found in planaria and other flatworms, which have an excretory system consisting of branching tubules that end in flame cells and nephridiopores. The flame cells are ciliated cells that draw water into the network of tubes. Nephridiopores are openings in body wall where urine is excreted.
Nephridia: Fluid enters the tubule and nutrients are reabsorbed. Wastes exit through a pore in the body wall. Ex. earthworm
Excretory Systems

8. Biology, 9th ed, Sylvia Mader
Excretory Organs
Biology, 9th ed, Sylvia Mader
Chapter 38
Malpighian Tubules: Tubules attached to the gut that absorb uric acid and water from the hemolymph. Water and some ions are reabsorbed at the hind gut. Urine is released out of the body. Ex. Ants
Kidneys: Birds, reptiles, and mammals have Kidneys, which are efficient in water conservation. Some have specialized salt glands that function to actively transport salt from the blood to the external environment
Excretory Systems

9. Urinary System in Humans
Biology, 9th ed, Sylvia Mader
Urinary System in Humans
Chapter 38
Human kidneys are located on either side of vertebral column, just below the diaphragm. Three main sections: 1- Renal Cortex- outermost layer, 2- Renal Medulla- between the cortex and pelvis, 3- Renal Pelvis- innermost layer where urine collects.
Excretory Systems

10. Biology, 9th ed, Sylvia Mader
Nephrons
Biology, 9th ed, Sylvia Mader
Chapter 38
Approx. a million in each kidney
Tiny tubules
Composed of:
Glomerular capsule
Glomerulus
Proximal convoluted tubule
Loop of the nephron
Distal convoluted tube
Collecting duct
Excretory Systems

11. Biology, 9th ed, Sylvia Mader
Chapter 38
Urine Formation
Consists of:
1. glomerular filtration
2. tubular re-absorption
3. tubular secretion
Human produces between 1-2 liters per day
Hypertonic solution (more solute and less water concentration than blood plasma)
Excretory Systems

12. Flow Chart through Kidneys
Biology, 9th ed, Sylvia Mader
Flow Chart through Kidneys
Chapter 38
Renal Artery-branches to smaller arteries to arterioles which go to each nephron
Glomerulus
Capillary beds that branch from arterioles
Blood pressure causes water, nutrients, salts and wastes (together know as filtrate) to move out of the blood
What is not in the filtrate?
Glomerular capsule- surrounds the glomerulus. Receives the filtrate from the glomerulus
Excretory Systems

13. Flow Chart through Kidneys
Biology, 9th ed, Sylvia Mader
Flow Chart through Kidneys
Chapter 38
Proximal convoluted tubule: salt ,water, and nutrients return to the blood here. Nearly 75% of the filtrate is reabsorbed (tubular reabsorption).
Peritubular capillary network: Secondary capillary bed that surrounds nephron.
Loop of the Nephron (Henle’s Loop): concentrates the urine. Descending limb: water moves out of loop. Ascending loop: NaCl moves out.
Distal Convoluted Tubule: More ions and water move out of filtrate (tubular reabsorption). Some molecules are removed from blood here and transported into tubules (tubular secretion).
Collecting duct: transports urine from several distal convoluted tubules through the renal medulla to the renal pelvis. Water continues to move out of filtrate here.
Excretory Systems

14. Biology, 9th ed, Sylvia Mader
Chapter 38
Flow chart of urine
Renal Pelvis- collecting tubules bring urine to the renal pelvis
Ureter- carries urine to the urinary bladder
Urinary bladder- where urine is stored
Urethra-opening through which urine is voided.
Excretory Systems

15. Biology, 9th ed, Sylvia Mader
Path of blood
Chapter 38
Renal Artery
Arteriole
Glomerulus
Peritubular capillary network
Venule
Renal Vein
Excretory Systems

16. Functions of the Kidneys
Biology, 9th ed, Sylvia Mader
Chapter 38
Functions of the Kidneys
Homeostatic functions through:
Excretion of metabolic wastes
Maintenance of water-salt balance
Maintenance of acid-base balance (pH balance)
Secretion of hormones: Erythropoietin to stimulate red blood cell production
Maintaining Water Balance.
Hormones: ADH-antidiuretic hormone- increases the amount of water reabsorbed, decreases amount of urine produced (more concentrated).
Maintenance of pH: pH is regulated by the bicarbonate buffer system by either the reabsorption of the bicarbonate ions, or the secretion of hydrogen ions. It is also regulated by breathing: Excretion of carbon dioxide by the lungs affects bicarbonate levels in the blood
Note: Kidney structures adapted to environments. Beaver- short loop of henle and dilute urine. Dessert Rodents- very long loop of henle, concentrated urine. 16
Excretory Systems

17. Biology, 9th ed, Sylvia Mader
Chapter 38
Homeostasis
Maintenance of normal internal conditions by self regulating mechanisms
Examples:
body fluid and salt balance
Temperature
glucose levels in blood
Excretory Systems