Excretory Products and their Elimination

Excretory Products and Their Elimination PDF Notes, Important Questions and Synopsis

SYNOPSIS

Excretion is the process by which living organisms get rid of waste substances either totally or partially accumulated during metabolic activities.
Modes of Excretion in Animals

Organs of Excretion in Animals

Animal group	Excretory structures
Protozoans	Contractile vacuole
Sponges	Body surface
Coelenterates	Body surface
Platyhelminthes	Protonephridia or flame cells
Annelids	Nephridia
Echinoderms	Tube feet and dermal branchiae

In the two limbs of the loop of Henle, urine flows in the opposite direction which forms a
counter current.
Similarly, the flow of blood in the two limbs of the vasa recta are also in the counter current pattern.
This system of a liquid flowing in the two limbs in two opposite directions is termed the counter
current mechanism.
It helps to maintain the concentration gradient in the renal medulla and hence helps in concentrating urine in the loop of Henle.

Regulation of Kidney Function

Myogenic Autoregulation	Neural Control	Hormonal Control
When the systemic blood pressure increases, the afferent arteriole narrows down which decreases GFR.	Nerve fibres of the sympathetic nervous system innervate the blood vessels of the kidneys which decreases GFR.	Anti-diuretic hormone (ADH) Renin Atrial natriuretic factor (ANF)

Role of Other Excretory Organs

Sweat glands	Excrete sweat
Lungs	Remove carbon dioxide and water vapour
Liver	Eliminates cholesterol, inactivated products of steroid hormones, vitamins and drugs
Large intestine	Removes salts such as calcium phosphate