Transcript The Excretory System

http://www.youtube.com/watch?v=qxb2_d9ilEw
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.
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
Homeostatic Control Mechanisms
• Communication within the
body is essential for
homeostasis.
• Homeostasis is accomplished
primarily by:
1. Endocrine system (blood
borne hormones)
2. Nervous system
(electrical signals)
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

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
The Excretory System Maintains Homeostasis In 3 Steps:
1. Filtration- Filters substances from the blood
2. Reabsorption- Regulate the chemical composition
of body fluids by retaining the proper amounts of
water, salts, and nutrients
3. Secretion- Elimination of wastes in the form of
urine
Evolutionary Trends in Excretion
Complex
Simple
Animal
Aquatic
Worms and
Taxon
Invertebrates
Mollusks
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
Insects
Using malpighian
tubules to collect and
excrete wastes
Vertebrates
Use of kidneys,
ureters, and a
bladder to collect
and excrete waste
Picture of
system
Examples
Sponges, jellyfish,
Earthworm, clam,
Grasshopper, ants,
planaria
octopus
bees
mammals, birds,
reptiles, fish,
amphibians
1.
Kidneys
1. Renal artery
2. Renal Vein
2.
3.
4.
Ureters
Urinary Bladder
Urethra
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

A tube, called the ureter, leaves each kidney
carrying urine to the urinary bladder

The urinary bladder is a saclike organ where
urine (a mixture of urea, water, and salt) is
stored before being excreted.
Foley Catheter

Tube that carries urine from bladder to the
outside of the body
Levels of Organization
Renal cells, bladder cells, etc…
Nephrons
Kidneys, Bladder, Ureter, Urethra
Excretory
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

Antidiuretic
Hormone
Hypothalamus
|
Tells pituitary
that amount of
water in blood
is low.
Low
amounts
of water
in blood
and high
amounts
of urine
produced
Tells pituitary
that amount of
water in blood
is high.
Pituitary
Stops
releasing
ADH into
bloodstream
|
Releases
ADH into
bloodstream
Kidneys
Reabsorbs
more
water.
|
Reabsorbs
less
water.
High
amounts
of water
in blood
and low
amount
of urine
produced.
 Lungs of the respiratory
system remove CO2
from blood.
 The circulatory system brings
wastes to the lungs, kidneys, and
skin for excretion.
 Skin of the
integumentary system
excretes water, urea,
salts, and other wastes
through sweat.


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.
1. Kidney Transplant
2. Kidney Dialysis Machine
▪ Expensive
▪ Time consuming
(3 X /week for few hours)