What Your Pulse Is Actually Telling You

The circulatory system is a delivery network with three parts: the heart, which pumps; the blood vessels — arteries and veins — which carry; and the blood itself, which does the carrying.

This page covers everything in the CBSE Class 7 Science chapter's third part: the circulatory system, what blood is made of, measuring your pulse, and how the body removes its wastes.

The heart is a muscular organ, roughly the size of your closed fist, that pumps blood continuously throughout life.

Arteries carry blood away from the heart. Because that blood is pushed out under high pressure, arteries have thick, elastic walls, and they lie deeper in the body.

Veins carry blood back to the heart. The pressure there is lower, so veins have thinner walls and contain valves that stop blood flowing backwards.

The reliable way to remember it: Arteries carry blood Away from the heart.

For example, the veins visible on the back of your hand are near the surface, while the arteries supplying the same hand run deeper and are not visible.

One exception is worth noting so it does not confuse you later: arteries usually carry oxygen-rich blood and veins oxygen-poor blood, but the direction — away from or back to the heart — is what actually defines them.

Blood has four components, each with a distinct job.

Plasma is the pale yellow liquid part. It carries the other components along with digested food, wastes and dissolved substances.

Red blood cells (RBCs) contain haemoglobin, a red pigment that binds oxygen and carries it to every cell. Haemoglobin is why blood is red, and why iron in your diet matters — iron is needed to make it.

White blood cells (WBCs) fight germs and protect the body from infection.

Platelets help blood to clot, sealing a cut so bleeding stops.

So blood transports three things at once: oxygen from the lungs to the cells, digested food from the small intestine to the cells, and wastes from the cells to the organs that remove them.

For example, when you cut your finger and it stops bleeding on its own, that is platelets forming a clot — and the scab that follows is that clot dried.

Each time the heart beats it pushes blood into the arteries, and the artery wall stretches slightly with the surge. That regular throb felt in an artery near the skin is the pulse.

So your pulse rate equals your heart rate — counting one measures the other.

To measure it, place two fingers on the inside of your wrist below the thumb, or on the side of your neck, until you feel the beat. Count the beats for one full minute. Do not use your thumb, which has a noticeable pulse of its own and can give a false reading.

A resting pulse of roughly 72 beats per minute is typical for an adult, and children's rates are usually higher.

Like breathing rate, pulse rate rises after exercise, because muscles need oxygen and food delivered faster — so the heart pumps more often. It is the circulatory half of the same response you saw in respiration.

Excretion is the removal of the harmful wastes produced by the body's own processes, chiefly urea and excess water and salts.

The kidneys are the main excretory organs. Blood carrying wastes flows into them, and they filter it, keeping the useful substances and removing the wastes and surplus water as urine. The urine travels down tubes to the urinary bladder, where it is stored until it is passed out.

But the kidneys are not the only route. The lungs remove carbon dioxide and some water vapour every time you breathe out. The skin removes water, salts and a little urea as sweat — which also cools the body as it evaporates.

For example, on a hot day you sweat more and pass less urine, because more water leaves through the skin; on a cold day the balance reverses.

The distinction to keep clear: excretion removes wastes made inside the body by its own chemistry, while egestion removes undigested food that never entered the cells at all.