THE EXCRETORY SYSTEM
The excretory system is a passive biological system that
removes excess, unnecessary materials from the body fluids of an
organism, so as to help maintain internal chemical homeostasis and
prevent damage to the body. It is also responsible for the
elimination of wastes produced by homeostasis.
The four functions of the excretory system are to get rid
of wastes, eliminate useless byproducts excreted from cells,
eradicate harmful chemical buildups and maintain a steady,
balanced chemical concentration in the body.
The dual function of excretory systems is the elimination of the waste products of
metabolism and to drain the body of used up and broken down components in a liquid and gaseous
state. In humans and other amniotes (mammals, birds and reptiles) most of these substances leave
the body as urine and to some degree exhalation, mammals also expel them through sweating.
There are several parts of the body that are involved in this process, such as sweat glands,
the liver, the lungs and the kidney system.
The Human Excretory System
The primary excretory organs in the human body are the kidneys, ureters and
urinary bladder, involved with the creation and expulsion of urine. Through
these organs, much of the nitrogenous waste of the body, especially urea, is
expelled. Other organs such as the liver, large intestine and skin are also
necessary for the excretion of specific metabolic wastes. Every living
organism generates waste in its body and has a mechanism to expel it. In
humans, waste generation and disposal are taken care of by the human
excretory system.
Parts of the Human Excretory System
Urinary tract
The urinary tract is a major part of the excretory system. It
filters wastes and water from the blood, and eliminates them from the
body.
KIDNEYS
Kidneys are the main organ of the human excretory system. The
kidneys are paired, bean-shaped organs located just below the rib
cage, one on each side of your spine. The kidneys performs many
crucial functions, including: maintaining overall fluid balance
filtering waste materials from food, medications, toxic substances
and is to filter blood and form urine. Each kidney is made up of three
sections: the renal cortex which is the outer layer, the renal
medulla which is the inner layer and the renal pelvis which is
responsible for carrying the urine from the kidney to the ureter. A
nephron is the basic structural and functional unit of the kidney.
These nephrons perform the primary task of filtering blood and
, removing waste products. The nephron uses four mechanisms to convert blood into urine:
filtration, reabsorption, secretion, and excretion of numerous substances.
URINARY BLADDER
The urinary bladder is a sac-like structure with muscular walls that holds urine
until it is expelled from the body during micturition. Micturition is the act of
expelling urine from the body. The bladder receives urine from the ureters, one
from each kidney. The bladder stores urine, allowing urination to be infrequent
and controlled .When empty, the bladder is about the size and shape of a pear.
The bladder is lined by layers of muscle tissue that stretch to hold urine. The
normal capacity of the bladder is 400-600 mL.
URETER
There is one ureter that comes out of each kidney as an extension of the renal
pelvis. The ureter is a thin muscular tube that carries urine from the kidneys to
the bladder. There are two ureters, one attached to each kidney. The upper half
of the ureter is located in the abdomen and the lower half is located in the pelvic
area. The ureter is about 10 to 12 inches long in the average adult.
URETHRA
This is a tube that arises from the urinary bladder and functions to expel urine to the
outside by micturition. The urethra is the tube that carries urine from the bladder to
outside of the body. The urethra is shorter in females and longer in the males.
LIVER
The liver regulates most chemical levels in the blood and excretes a product called
bile. This helps carry away waste products from the liver. All the blood leaving the
stomach and intestines passes through the liver. The liver has an important function
in excretion. It is said to be the first line of defence when it comes to hormones, fats, alcohol, and
drugs.
Other Excretory Organs
Apart from the above mentioned excretory organs, there are other organs that also
perform some form of excretion.
Skin
The skin is the largest organ in the body. Its primary function is to protect the different
organs of the body. However, the skin helps in excretion by the way of sweat.
Lungs
The lungs in the respiratory system excrete some waste products, such as carbon dioxide
and water. But, in this process, they also function to eliminate some amount of water in the
form of vapor.
The excretory system is a passive biological system that
removes excess, unnecessary materials from the body fluids of an
organism, so as to help maintain internal chemical homeostasis and
prevent damage to the body. It is also responsible for the
elimination of wastes produced by homeostasis.
The four functions of the excretory system are to get rid
of wastes, eliminate useless byproducts excreted from cells,
eradicate harmful chemical buildups and maintain a steady,
balanced chemical concentration in the body.
The dual function of excretory systems is the elimination of the waste products of
metabolism and to drain the body of used up and broken down components in a liquid and gaseous
state. In humans and other amniotes (mammals, birds and reptiles) most of these substances leave
the body as urine and to some degree exhalation, mammals also expel them through sweating.
There are several parts of the body that are involved in this process, such as sweat glands,
the liver, the lungs and the kidney system.
The Human Excretory System
The primary excretory organs in the human body are the kidneys, ureters and
urinary bladder, involved with the creation and expulsion of urine. Through
these organs, much of the nitrogenous waste of the body, especially urea, is
expelled. Other organs such as the liver, large intestine and skin are also
necessary for the excretion of specific metabolic wastes. Every living
organism generates waste in its body and has a mechanism to expel it. In
humans, waste generation and disposal are taken care of by the human
excretory system.
Parts of the Human Excretory System
Urinary tract
The urinary tract is a major part of the excretory system. It
filters wastes and water from the blood, and eliminates them from the
body.
KIDNEYS
Kidneys are the main organ of the human excretory system. The
kidneys are paired, bean-shaped organs located just below the rib
cage, one on each side of your spine. The kidneys performs many
crucial functions, including: maintaining overall fluid balance
filtering waste materials from food, medications, toxic substances
and is to filter blood and form urine. Each kidney is made up of three
sections: the renal cortex which is the outer layer, the renal
medulla which is the inner layer and the renal pelvis which is
responsible for carrying the urine from the kidney to the ureter. A
nephron is the basic structural and functional unit of the kidney.
These nephrons perform the primary task of filtering blood and
, removing waste products. The nephron uses four mechanisms to convert blood into urine:
filtration, reabsorption, secretion, and excretion of numerous substances.
URINARY BLADDER
The urinary bladder is a sac-like structure with muscular walls that holds urine
until it is expelled from the body during micturition. Micturition is the act of
expelling urine from the body. The bladder receives urine from the ureters, one
from each kidney. The bladder stores urine, allowing urination to be infrequent
and controlled .When empty, the bladder is about the size and shape of a pear.
The bladder is lined by layers of muscle tissue that stretch to hold urine. The
normal capacity of the bladder is 400-600 mL.
URETER
There is one ureter that comes out of each kidney as an extension of the renal
pelvis. The ureter is a thin muscular tube that carries urine from the kidneys to
the bladder. There are two ureters, one attached to each kidney. The upper half
of the ureter is located in the abdomen and the lower half is located in the pelvic
area. The ureter is about 10 to 12 inches long in the average adult.
URETHRA
This is a tube that arises from the urinary bladder and functions to expel urine to the
outside by micturition. The urethra is the tube that carries urine from the bladder to
outside of the body. The urethra is shorter in females and longer in the males.
LIVER
The liver regulates most chemical levels in the blood and excretes a product called
bile. This helps carry away waste products from the liver. All the blood leaving the
stomach and intestines passes through the liver. The liver has an important function
in excretion. It is said to be the first line of defence when it comes to hormones, fats, alcohol, and
drugs.
Other Excretory Organs
Apart from the above mentioned excretory organs, there are other organs that also
perform some form of excretion.
Skin
The skin is the largest organ in the body. Its primary function is to protect the different
organs of the body. However, the skin helps in excretion by the way of sweat.
Lungs
The lungs in the respiratory system excrete some waste products, such as carbon dioxide
and water. But, in this process, they also function to eliminate some amount of water in the
form of vapor.
