1. The Excretory System

2. REGULATION Excretory & Nervous Systems
Regulation within animal systems requires maintaining homeostasis- the ability of the body or a cell to seek and maintain stability within its internal environment when dealing with external changes
There are several organ systems that work together to maintain an organism’s internal environment, despite changes that occur in its external environment.
The nervous system maintains homeostasis by controlling and regulating the other parts of the body.
The excretory system helps regulate the concentration of water and other components of body fluids.

3. Homeostasis
Every organ system plays a role in maintaining the constancy of the internal environment.
Examples:
Blood level of nutrients, blood pressure, heart activity, wastes must not be allowed to accumulate, body temperature must stay within normal limits

4. Homeostatic Control Mechanisms
Communication within the body is essential for homeostasis.
Homeostasis is accomplished primarily by:
Endocrine system (blood borne hormones)
Nervous system (electrical signals)

6. Negative Feedback vs. Positive Feedback Mechanisms
Negative Feedback Mechanism – The net effect of the response to the stimulus is to shut off the original stimulus or to reduce its intensity.
Examples: Thermostat or body temperature, heart rate, blood pressure, breathing rate, blood levels
Positive Feedback Mechanism – Feedback that tends to cause a variable to change in the same direction as the initial change; enhances the stimulus
Examples: Blood clotting, birth of a baby
More rare in the body

7. Excretion
Excretion – the process by which metabolic wastes are eliminated from the blood
One part of the many processes that maintain homeostasis.
Every cell in the body produces metabolic wastes, such as excess salts, carbon dioxide, and urea

8. Excretory System Function
The Excretory System Maintains Homeostasis In 3 Steps:
Filtration- Filters substances from the blood
Reabsorption- Regulate the chemical composition of body fluids by retaining the proper amounts of water, salts, and nutrients
Secretion- Elimination of wastes in the form of urine

9. Evolutionary Trends in Excretion Aquatic Invertebrates
Excretory System
Evolutionary Trends in Excretion
Simple
Complex
Animal Taxon
Aquatic Invertebrates
Worms and Mollusks
Insects
Vertebrates
Release Wastes By…
diffusion to remove waste across their cell membranes directly into the water
Use of nephridia- tiny pores along the body excrete wasste
Using malpighian tubules to collect and excrete wastes
Use of kidneys, ureters, and a bladder to collect and excrete waste
Picture of system
Examples
Sponges, jellyfish, planaria
Earthworm, clam, octopus
Grasshopper, ants, bees
mammals, birds, reptiles, fish, amphibians

10. Main Organs of the Excretory System
Kidneys
Renal artery
Renal Vein
Ureters
Urinary Bladder
Urethra

11. Major Organs of the Excretory System
Kidneys (renal = kidney)-
Located on either side of the spinal column near the lower back.
Paired organs that receive blood via the renal artery
The main filtering units are tissues called nephrons that separate the components of the blood
Every 45 minutes kidneys filter all the blood in your body
Excess water and urea in the form of urine leave the kidney via the ureter where it leaves as urine out the urethra
Filtered blood leaves kidneys and returns to circulation carrying nutrients, salts, and water via the renal vein

12. Ureter
A tube, called the ureter, leaves each kidney carrying urine to the urinary bladder

13. Urinary Bladder
The urinary bladder is a saclike organ where urine (a mixture of urea, water, and salt) is stored before being excreted.
When bacteria get into the bladder or kidney and multiply in the urine, they may cause a UTI.
Foley Catheter

14. Urethra
Tube that carries urine from bladder to the outside of the body
The state of the reflex system is dependent on both a conscious signal from the brain and the firing rate of sensory fibers from the bladder and urethra. At low bladder volumes, afferent firing is low, resulting in excitation of the outlet (the sphincter and urethra), and relaxation of the bladder. At high bladder volumes, afferent firing increases, causing a conscious sensation of urinary urge.

15. Levels of Organization
Excretory System
Levels of Organization
Nephrons
Kidneys, Bladder, Ureter, Urethra
Excretory
Renal cells, bladder cells, etc…

16. Kidney Stones
Sometimes substances such as calcium, magnesium, or uric acid salts in the urine crystallize and form kidney stones.
When kidney stones block the ureter they cause great pain.
Often treated using ultrasound, in which the sound waves pulverize the stones into smaller fragments
Prevent by: drink lots of water, diet lower in protein (N), sodium

17. Releases ADH into bloodstream
ADH Process
Antidiuretic Hormone
Hypothalamus |
Tells pituitary
that amount of
water in blood
is low.
Tells pituitary
that amount of
water in blood
is high.
High
amounts
of water
in blood
and low
amount
of urine
produced.
Low
amounts
of water
in blood
and high
of urine
produced
Pituitary |
Stops releasing
ADH into bloodstream
Releases ADH into bloodstream
Kidneys |
Reabsorbs
more water.
Reabsorbs
less water.

18. Other Organs: Lungs of the respiratory system remove CO2 from blood.
Skin of the integumentary system excretes water, urea, salts, and other wastes through sweat.
The circulatory system brings wastes to the lungs, kidneys, and skin for excretion.

19. Kidney Damage Humans have two kidneys and can survive with only one.
If both kidneys are damaged by disease or injury, there are two ways to keep an individual alive.
Kidney Transplant
Kidney Dialysis Machine
Expensive
Time consuming
(3 X /week for few hours)