NAME - SAKSHI AGARWAL
ROLL NO. – 24
The kidneys regulate the amount of water, salts and
other substances in the blood.
The kidneys are fist-sized, bean shaped structures
that remove nitrogenous wastes (urine) and excess
salts from the blood.
The ureters are tubes that carry urine from the
pelvis of the kidneys to the urinary bladder.
The urinary bladder temporarily stores urine until it
is released from the body.
The urethra is the tube that carries urine from the
urinary bladder to the outside of the body.
The outer end of the urethra is controlled by a
circular muscle called a sphincter.
Each kidney is composed of three sections:
the outer (renal) cortex, the (renal) medulla (middle
part) and the hollow inner (renal) pelvis.
The cortex is where the blood is filtered.
The medulla contains the collecting ducts which carry
filtrate (filtered substances) to the pelvis.
The pelvis is a hollow cavity where urine accumulates
and drains into the ureter.
Function of the Kidney
The principal function of the kidney is to
filter blood in order to remove cellular
waste products from the body.
At any given time, 20 % of blood is in
the kidneys. Humans can function with
If one ceases to work, the other
increases in size to handle the workload.
The kidney has other functions but it is
usually associated with the excretion of
cellular waste such as :
1) urea (a nitrogenous waste produced in
the liver from the breakdown of protein.
It is the main component of urine)
2) uric acid (usually produced from
breakdown of DNA or RNA) and
3) creatinine (waste product of muscle
All of these compounds have nitrogen as a major
The kidneys are more than excretory organs.
They are one of the major homeostatic organs of
They control water pH, secrete erythropoietin (a
hormone that stimulates red blood cell
production) and activate vitamin D production in
That is why a doctor can tell so much from a
How blood is Filtered ?
The filtering units of the kidneys are the
There are approximately one million nephrons in
The nephrons are located within the cortex and
medulla of each kidney.
The tubes of the nephron are surrounded by cells
and a network of blood vessels spreads
throughout the tissue. Therefore, material that
leaves the nephron enters the surrounding cells
and returns to the bloodstream by a network of
Parts of the Nephron
Each nephron consists of the following parts:
1) glomerulus ;
2) Bowman’s capsule ;
3) proximal tubule ;
4) loop of Henle ;
5) distal tubule ;
6) collecting duct.
A few disorders of the excretory system
Renal failure - (kidney failure)
UTIs - urinary tract infections, often caused by
urethritis-inflammation of the urethra
pyelonephritis- inflammation of the
Cause - metabolic disorder involving calcium,
proteins and uric acid the build up of these
substances into a large deposit (stone)
Symptoms - irritation of the urinary tract,
bleeding in the urinary tract, in cases with
large stones there can be extreme pain as
the stone(s) try to pass through the tract
Treatments - removal by surgical means,
breakdown of stones by either physical
(ultrasound) or chemical means, dietary
changes to reduce chances of stones.
Renal (kidney) failure
Causes - infections, trauma, diabetes,
Symptoms - build up of toxins in the
blood stream (urea), jaundice, fatigue
Treatments - dialysis, drug therapy,
ureters - In human, the ureters are
tubes made of smooth muscle fibers
that propel urine from the kidneys to
the urinary bladder. In the adult, the
ureters are usually 25–30 cm long and
3–4 mm in diameter. Long narrow tubes
with expanded upper end (renal pelvis)
located inside each kidney. Function is
to drain the renal pelvis to urinary
urinary bladder- The urinary bladder
is the organ that collects urine
excreted by the kidneys before
disposal by urination. Elastic muscular
organ capable of great expansion.
Function of urinary bladder is
storage of urine.
urethra – is a tube that connects the
urinary bladder to the urinary meatus
for the removal of fluids from the body
. In male, the urethra travels through
the penis, and carries semen as well as
urine.In female , the urethra is shorter
and emerges at the female external
urethral orifice above the vaginal