Excretory system

بسم الله الرحمن الرحيم
السلام عليكم ورحمة الله وبركاته

Excretory system



The excretory system is a passive biological system
that removes excess, unnecessary or dangerous materials f
rom an organism, so as to help maintain homeostasis
within the organism and prevent damage to the body.

It is responsible for the elimination of the waste products
of metabolism as well as other liquid
and gaseous wastes.

As most healthy functioning organs produce metabolic
and other wastes, the entire organism depends
on the function of the system; however,
only the organs specifically for the excretion process
are considered a part of the excretory system

As it involves several functions that are only superficially related,
it is not usually used in more formal classifications
of anatomy or function


Excretory functions

Within each kidney are an estimated
one million microscopic nephrons

Filtering of the blood takes place within these areas
Each nephron contains a cluster of capillaries
called a glomerulus

A cup-shaped sac called a bowmans capsule
surrounds each glomerolus
The blood that flows through the glomerulus
is under great pressure
This causes glomerulus, water
glucose and urea to enter the bowmans capsule

White blood cells, red blood cells
and proteins remains in the blood
As the blood continues through the blood vessels
it winds around the renal tubala

During this time, reabsorption occurs
Glucose and chemicals , such as potassium ,sodium
hydrogen magnesium and calcium are reabsorbed into the blood
Almost all the water removed during filteration
returns to the blood during the reabsorption phase

The kidneys control the amount of liquid in our bodies
Now only wastes are in the nephron
These wastes are called urine and include urea
water and inorganic salts

The cleansed blood goes into veins that carry the blood
from the kidneys and back to the heart


Component organs

Skin

Excretion by definition is passive and deals
with metabolic wastes as filtered by the kidneys
Though the sweat may contain a trace amount
of metabolic wastes, sweating is an active process
of secretion not excretion, specifically for temperature control
and pheromone release

Therefore, its role as a part of the excretory system
is minimal at best


Lungs

The lungs and gills of organisms constantly secrete
gaseous wastes from the bloodstream
as a regular part of respiration


Kidneys



The primary organs in the excretory system of vertebrates
The kidneys are placed on either side
of the spinal column near the lower back
They are primarily responsible for filtering blood
by removing nitrogenous wastes from
metabolismsalts & other excess minerals and excess water


Ureter

In human anatomy, the ureters are muscular ducts
that propel urine from the kidneys to the urinary bladder
In the adult, the ureters are usually 25–30 cm (10–12 in) long
In humans, the ureters arise from the renal pelvis
on the medial aspect of each kidney before descending
towards the bladder on the front of the psoas major muscle
The ureters cross the pelvic brim near the bifurcation
of the iliac arteries which they run
over This "pelviureteric junction" is a common site for
the impaction of kidney stones
(the other being the uteterovesical valve)
The ureters run posteroinferiorly
on the lateral walls of the pelvis

They then curve anteriormedially to enter
the bladder through the back
at the vesicoureteric junction
running within the wall of the bladder for a few centimeters
The backflow of urine is prevented by valves
known as ureterovesical valves
In the female, the ureters pass through the mesometrium
on the way to the urinary bladder


Urinary bladder

The urinary bladder is the organ that collects urine excreted
by the kidneys prior to disposal by urination
A hollow muscular, and distensible (or elastic) organ
the bladder sits on the pelvic floor
Urine enters the bladder via the ureters and exits via the urethra

Embryologically, the bladder is derived from
the urogenital sinus and, it is initially continuous
with the allantois
In males, the base of the bladder lies between
the rectum and the pubic symphysis
It is superior to the prostate, and separated from
the rectum by the rectovesical excavation
In females, the bladder sits inferior to the uterus
and anterior to the vagina
It is separated from the uterus by the vesicouterine excavation
In infants and young children
the urinary bladder is in the abdomen even when empty


Urethra

In anatomy, the urethra (from Greek οὐρήθρα - ourethra) is
a tube which connects the urinary bladder to the outside of the body
The urethra has an excretory function in both sexes
to pass urine to the outside
and also a reproductive function in the male
as a passage for semen during sexual activity

The external urethral sphincter is a striated muscle
that allows voluntary control over urine


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