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. 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.
PARTS
KIDNEYS:
These are two bean-shaped organs about15 cm long.There is one on either side of spinal column.They are surrounded by a thik layer of fat.
The kidneys are formed by strucutures called nephrons,wich produce urine.
There is an adrenal gland on top of each kidney.These glands are part of the endocrine system.
The renal artery enters the kidney on its concave side.The renal vein and ureter also leave on this side.
URETERS:
These are two 25 cm-long,narrow tubes.They take urine from this kidneys to the urinary bladder.
URINARY BLADDER:
This is an expandable,muscular organ.Up to half a litre of urine can collect here.
Urine flows continuously from the ureters into the bladder.
When the bladder is full,urination occurs.
URETHRA:Urine flows this tube from the bladder to the outside of the body during urination.
THE NEPHRON
The nephron
is the basic structural and functional unit of the kidney.Its functions are
vital to life and are regulated
by the endocrine system by hormones such as antidiuretic hormone, aldosterone, and parathyroid
hormone. In humans, a normal kidney contains 800,000 to
1.5 million nephrons.
FUNCTIONS OF THE NEPHRON
Remove excess water,wastes and other substances from your blood.
Return substances like sodium, potassium or phosphorus whenever any of these substances run low in your body.
Each nephron is composed of two main structures: the glomerulus and renal (kidney) tubule.
The Glomerulus
The glomerulus is a tiny blood vessel or capillary, which looks like a ball of yarn. Actual filtering of your blood occurs in the glomerulus.
Each of your glomeruli acts like a sieve that helps keep normal proteins and cells in your bloodstream and allows wastes, excess fluid and other substances to pass.
The Tubule
The tubule, also called renal or kidney tubule, is a tiny tube where the wastes, extra fluid and other recyclable substances like sodium and potassium filtered out from the glomerulus pass through.
Your kidneys measure out chemicals like sodium, phosphorus, and potassium and release them back to the blood to return to the body when need arises. In this way, your kidneys regulate the your body’s level of these substances. The right balance is necessary for you to function properly.
Remove excess water,wastes and other substances from your blood.
Return substances like sodium, potassium or phosphorus whenever any of these substances run low in your body.
Each nephron is composed of two main structures: the glomerulus and renal (kidney) tubule.
The Glomerulus
The glomerulus is a tiny blood vessel or capillary, which looks like a ball of yarn. Actual filtering of your blood occurs in the glomerulus.
Each of your glomeruli acts like a sieve that helps keep normal proteins and cells in your bloodstream and allows wastes, excess fluid and other substances to pass.
The Tubule
The tubule, also called renal or kidney tubule, is a tiny tube where the wastes, extra fluid and other recyclable substances like sodium and potassium filtered out from the glomerulus pass through.
Your kidneys measure out chemicals like sodium, phosphorus, and potassium and release them back to the blood to return to the body when need arises. In this way, your kidneys regulate the your body’s level of these substances. The right balance is necessary for you to function properly.
THE URINE
Urine is a liquid produced by the kidneys to remove waste products from the bloodstream. Human urine is yellowish in color and variable in chemical composition, but here is a list of its primary components.
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PRIMARY COMPONENTS
Human urine consists primarily of water (91% to 96%), with organic solutes including urea, creatinine, uric acid, and trace amounts of enzymes, carbohydrates, hormones, fatty acids, pigments, and mucins, and inorganic ions such as sodium (Na+), potassium (K+), chloride (Cl-), magnesium (Mg2+), calcium (Ca2+), ammonium (NH4+), sulfates (SO42-), and phosphates (e.g., PO43-).
