Online Notes on Chapter = 6 ( life processes) Part 3

This is Online Notes on Chapter = 6 ( life processes)  Part 3 for 
preparation of CBSE BOARD Examination, NTSE etc.



Blood:

Lymph : A yellowish fluid escapes from the blood capillaries into the intercellular spaces contain less proteins than blood. Lymph flows from the tissues to the heart assisting in transportation and destroying germs.

Blood Vessels:

Function :

(a) Absorption and upward movement of water and minerals by creating PULL.

(b) Helps in temperature regulation in plant.

Transport of food from leaves (food factory) to different part of the plant is called Translocation.

EXCRETORY SYSTEM IN MAN

Excretory/urinary system consists of :

(1) The kidneys : The excretory organ

(2) The ureters : The ducts which drain out urine from the kidneys

(3) The urinary bladder : The urinary reservoir

(4) The urethra : The channel to the exterior

                   The human excretory system

EXCRETION

1. The metabolic activities in the body generates many kinds of wastes including

nitrogenous wastes which are harmful for the body and hence needed to be removed.

Excretion is a process by which these wastes are removed from our body.

2. Unicellular organisms remove these wastes by simple diffusion.

Human Excretory System

Formation of Urine:

• Each kidney contains many filtration units called as nephrons.

• Nephrons are made up of a cluster of thin walled capillaries called glomerulus

which is associated with a cup like structure called as Bowman’s capsule and the

long tube which terminates through this capsule.

• The renal artery brings oxygenated blood to the kidneys along with the nitrogenous wastes like urea and uric acid and many other substances.

• The blood gets filtered through the glomerulus and this filtrate enters the tubular part of nephron.

• As this filtrate moves down the tubular part, glucose, amino acids, salts and excess of water gets selectively reabsorbed by the blood vessels surrounding these tubules.

• The amount of water reabsorbed depends upon :

* How much excess of water is there in the body and,

* How much nitrogenous wastes need to be excreted out.

• So the fluid now flowing in the tubular part is urine which gets collected in collecting ducts of nephrons.

• These collecting ducts together leave the kidney at a common point by forming the ureter.

• Each ureter drains the urine in the urinary bladder where it is stored until the

pressure of expanded bladder leads to an urge to pass it out through urethra.

• This bladder is a muscular structure which is under nervous control.

• 180 litres of filtrate is formed daily but only 2 litres is excreted out as urine so the rest is reabsorbed in the body.

Functions of Nephron:

• Excretion of nitrogenous wastes.

• To maintain the water and ionic balance (osmic regulation).

Excretion in Plants:

Plants use different strategies for excretion of different products :

• Oxygen and carbon dioxide is diffused through stomata.

• Excess water is removed by transpiration.

Plants can even loose some of their old parts like old leaves and bark of tree.

• Other waste products like raisins and gums especially in old xylem cells which canalso be lost by plants.

• Plants also secrete some waste substances into the soil around them

                                               Structure of a Nephron

The urine formation involves three steps :

1. Glomerular filtration : Nitrogenous wastes, glucose water, amino acid filter from the blood into Bowman Capsule of the nephron.

2. Tubular reabsorption : Now, useful substances from the filtrate are reabsorbed back by capillaries surrounding the nephron.

3. Secretion : Urea, extra water and salts are secreted into the tubule which open up into the collecting duct & then into the ureter.

Artificial Kidney:

Haemodialysis : The process of purifying blood by an artificial kidney. It is meant for kidney failure patients.

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