Download Excretion vs. Elimination Excretion vs. Elimination

Excretion vs. Elimination
Excretion vs. Elimination
• Your body makes several kinds of
waste, which fall into two groups:
– Undigested solid wastes
– Wastes made by cells
Elimination
• Undigested solid waste
leaves your body
through the large
intestine
– Water is removed
from the wastes in
the large intestine,
which allows for the
formation of a solid
(feces).
– The solid wastes
moves from the
large intestine to
the rectum.
– From the rectum,
the solid waste is
excreted
through the
anus.
Excretion
• When waste products made by cells
(water, heat, carbon dioxide, salts,
urea) leave your body
• In many animals, CO2 leaves the body
through the lungs
• The liquid waste, urine, is made in the
kidneys
• Urine: made up of water, heat,
harmful chemicals (urea), and
some salts
• Perspiration: when heat, water,
and salt are excreted by the body
through skin (i.e. sweating)
Write the correct waste product next to
the excretory organ:
1. Skin =
2. Large intestine =
3. Lungs =
4. Kidneys =
(word bank: carbon dioxide, solid wastes,
salt, harmful chemicals, water, heat)
The waste products are:
Skin = water, heat, salt
Large Intestine = solid waste
Lungs = carbon dioxide
Kidneys = harmful chemicals, heat, salt
The Excretory System
• The group of organs responsible for
removing waste products from the
body = the excretory system
• The main organs are:
– Lungs
– Kidneys
– Skin
Lungs
• When we breathe, we excrete CO2
waste, and small amounts of heat and
water
• Fact: your lungs are capable of
removing alcohol from the blood; this
is how a breathalyzer is able to
determine a person’s blood alcohol
level
Skin
• Largest organ; excretes most of the
body’s waste heat
• Also removes some water, salts, and
very small amounts of urea
• Perspiration: helps the body ‘cool off’
– When sweat evaporates from the skin, it
cools the body, removing heat
Kidneys
• Fist sized, bean shaped (i.e. kidney
bean) organs found on either side of
the lower spine
• Main job is to filter out wastes from the
blood, making them more
concentrated in preparation for
excretion and, in the process of doing
this, retaining as much water as
possible
• The blood enters the kidney through
the renal arteries; renal veins carry
blood back from the kidneys to the
body
• A ureter connects each kidney to the
urinary bladder; once urine has
formed, the ureter carries the urine
(produced after the blood has been
filtered for wastes) from the kidney to
the bladder
• Another tube, the urethra, carries the
urine out of the body
• In males, the urethra passes through
the penis; in females, it lies between
the pubic bone and the front wall of
the vagina
Label the diagram: bladder, kidney, renal
artery and vein, ureter, urethra
Nephrons
• The filtration of the blood takes
place in minute structures called
nephrons, found in the cortex, which
is the outer layer of the kidney
• The nephrons estimate at more than
1 million per kidney
• In spite of their size, the kidneys filter
more than 180 L of blood every 24
hours
– Most is reclaimed by the body, only 1.5 L
of urine is passed each day
– Your blood passes through the kidneys 300
times per day
Label the Kidney: cortex, medulla, renal artery,
renal pelvis, renal vein, ureter
Liver
• A secondary organ of excretion
• Does not excrete wastes, but is
important for excretion
• Handles cell wastes in several ways:
1) Breaks down dead red blood cells:
pass into digestive tract, then
eliminated with solid waste by the
bowels
2) Weakens certain harmful substances
3) Changes some harmful substances
Ex: the liver makes bile from harmful
substances – bile is important in fat digestion
– after bile works on fat, it is eliminated from
the bowels
4) Combines certain harmful chemicals
Ex) liver combines ammonia and some CO2
– forms urea, which the blood carries to the
kidneys where it becomes part of the urine