Question

Explain human excretory system with the help of a suitable diagram.

Answer 1

Excretory organs remove the wastes such as salts, carbon dioxide and urea produced by the body during homeostasis. The kidney is the primary or major excretory organs of man and other vertebrates. These are one pair bean-shaped, large-sized slightly flattened structures present in the upper part of the abdominal cavity between the last thoracic and third vertebra close to the dorsal along the dorsal body wall.

Complete answer:
Human excretory system includes organs that facilitate the removal of elimination of wastes such as salts, carbon dioxide and urea produced by the body during homeostasis. The main excretory organs include:

A pair of kidneys
A pair of ureters
A urinary bladder
Urethra.

KIDNEYS

These are the primary or major excretory organs of man and other vertebrates.
These are one pair bean-shaped, large-sized slightly flattened structures present in the upper part of the abdominal cavity between the last thoracic and third vertebra close to the dorsal along the dorsal body wall.
Ureters, blood vessels, nerves etc enter or leave the kidney through the hilum.
The outer layer is called the capsule. Internally, each kidney is divided into the outer granulated cortex and inner striated medulla. The cortex extends in between the medullary pyramids as renal columns termed columns of Bertini.
Inside, each kidney is composed of nearly one million uriniferous or renal tubules of nephrons.
Nephrons are called the functional units of the kidney.
URETERS
These are one pair, long (25-30 cm), narrow, muscular, tubular structure.
These arise from the hilus of kidneys by its upper broader part termed as renal pelvis.
These are lined with transitional epithelium.
Being muscular it undergoes peristalsis to pass urine from kidneys to the urinary bladder.
URINARY BLADDER
It is a large, thin-walled, distensible, pear-shaped sac present in the pelvis region of the abdominal cavity.
It has an upper-body with two openings of ureters and lower trigone leading to the urethra and guarded by two sphincters: inner of smooth muscle fibers and outer of striated muscle fibers.
URETHRA
The tube emerging from the urinary bladder to release urine having sphincters at both ends.
In women, it is a short tube opening separately below the clitoris in the vulva.
In man, urethra joins the ejaculatory duct to form a urogenital canal which passes through the penis and opens by the urogenital aperture at the tip of the penis. It is a common passage for urine and seminal fluid.
The function of the excretory system:
Elimination of waste such as urea, ammonia, and uric acid from the bloodstream by the production of urine.
Maintain volume and ionic balance in extracellular fluid
Maintain pH and osmotic concentration of the extracellular fluid.

Note:
Humans are ureotelic organisms i.e. they excrete urea. Responsibility of the excretory organs is to remove the wastes such as salts, carbon dioxide and urea produced by the body during metabolic reactions. In the vertebrate’s kidney are the primary or major excretory organs. Kidneys are paired bean-shaped, large-sized slightly flattened structures present in the upper part of the abdominal cavity between the last thoracic and third vertebra close to the dorsal along the dorsal body wall.