Page 94 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

v Veins carry deoxygenated blood from all parts of the body back to the heart.

v Vena cava is the main vein. Pulmonary vein carries oxygen-rich blood from the lungs to the
heart.

v Capillaries are small, thin blood vessels that connect the arteries & veins.
v Heart is a musclular organ that pumps blood in the blood vessels.

v Human heart has four chambers–the upper two chambers called the right & left atrium and

the lower two chambers called the right & left ventricles.
v The valves present between different chambers of the heart ensure that the blood flows

only in a particular direction, i.e., they prevent the backflow of blood in the heart.
v The rhythmic contraction & expansion of various chambers of the heart maintains the

transport of oxygen to all body parts.
v The rhythmic contraction & relaxation of the heart, as it is pumping blood, produces a

thumping sound known as heartbeat.

v Heartbeat can be heard using an instrument called stethoscope.
v The number of times the heart of a person beats per minute is called the pulse rate. The

normal pulse rate is 70 to 80 beats per minute.
v The process of removal of waste materials, produced during various metabolic activities,

from the body is called excretion.
v The system responsible for excretion is called the excretory system that includes the

following excretory organs, such as liver, kidneys, lungs and the skin.

v Lungs excrete carbon dioxide, liver excrete urea & sweat is excreted by the skin via sweat
glands in the deeper layer of the skin.

v The excretory system of human beings consists of two kidneys, two ureters, urinary bladder
& urethra.

v Kidneys are a pair of purplish-brown organs located below the ribs towards the middle of
the back. Kidneys remove urea from the blood through tiny filtering units called nephrons.

The filtered waste so formed called urine is transported to the urinary bladder via ureters,

where it is temporarily stored till it is expelled by micturition. Urethra expels urine from the
body. The opening of the urethra is guarded by sphincter muscles that controls the opening

& closing of urethra.
v Transportation of various substances in a plant is done through special kind of tissues called

vascular tissues or conducting tissues. These are pipe-like vessels.
v There are two types of vascular tissues in plants – xylem & phloem.

v Xylem connects the roots to the leaves through the stem and the branches. It helps in the
transportation of water & minerals from the roots to the leaves.

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