HSEB Notes Physiology of Excretion
Lesson : Excretion and osmoregulation
Class : 12
Excretion is the removal of metabolic waste from body particularly nitrogenous waste. Skin, lungs, liver are considered as accessory excretory organs while kidney is the most important one which forms as important part of the4 urinary system also. Urinary system of man consists of 1. Kidneys 2. Ureters 3. Urinary bladder 4. Urethra
Kidneys paired structures, chief excretory organs in man which can act as efficient filters. Kidneys excrete nitrogenous and other metabolic wastes in the form of urine. Ureters two ureters, one arising form each kidney. Carry urine formed in side Kidney to urinary bladder. Each ureter is a thin muscular tube about 25 cm in length arising from hilum of each kidney. Urine moves by peristaltic waves of its walls.
Urinary bladder present in the form of storage sac. Collects urine from both the kidneys via ureters. Urine stored temporarily until it is released via urethra. The volume of bladder increases as it stores much urine. It has lining of transitional epithelium which stretches as the volume of urine increases. Urethra small membranous tube that carries urine at intervals urinary bladder to the exterior. There is a urethral muscular sphincter at the base of urethra which consists of a circular band of muscle. By the contraction and Relaxation of this muscle the flow of urine into urethra is controlled. Sphincter keeps urethra closed except during voiding of urine. Micturition it is act of voiding of urine. The urine is carried by peristaltic waves down the ureter. Accumulation of urine in the bladder raises its pressure And a continuous reflex is initiated. As the smooth muscle of bladder wall Contract, the urethral sphincter muscle relaxes evacuating the urine. Urine does not flow back as the ureters pass obliquely. Their terminal parts get closed during contractions. Micturition may be initiated or delayed Voluntarily.
Don't forget to Like and Share it and Please Join with us on Facebook and Google+
No comments:
Post a Comment
Don't forget to leave your comment.