Biology · Class 11 Science

Ch 15Body Fluids and Circulation — Class 11 Biology, concept-first.

Every living cell depends on a steady supply of nutrients and oxygen, and just as steadily needs its waste and harmful by-products carried away — a demand that never really stops as long as the tissue stays alive.

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Blood Formed Elements

Think of blood as a busy river. Most of what you notice is the water it flows in, but the river is also full of things being carried along — boats, logs, swimmers.

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Chapter contents

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Introduction

15.1

Blood

Blood is not the simple red liquid it appears to be. It is classified as a special type of connective tissue, because like other connective tissues it links different parts of the body and is built ar…

15.1.1

Plasma

Plasma is the fluid matrix of blood — a straw-coloured, viscous liquid that makes up the larger share of blood, close to 55 per cent of its total volume.

15.1.2

Formed Elements

The cellular part of blood is made up of three components — erythrocytes, leucocytes and platelets — which together are called the formed elements.

15.1.3

Blood Groups

Although a sample of human blood looks much the same from one person to the next, blood in fact differs in certain chemical respects, and these differences let it be sorted into groups.

15.1.3.1

ABO grouping

The ABO system sorts blood according to the presence or absence of two surface antigens on the red blood cells, called A and B. Antigens are chemicals capable of triggering an immune response.

15.1.3.2

Rh grouping

Besides the ABO blood groups, human blood is classified by another important antigen on the surface of the red blood cells — the Rh antigen, so called because an antigen very like it was first observe…

15.1.4

Coagulation of Blood

When you cut your finger, the bleeding does not go on indefinitely; after a short while the blood stops flowing on its own.

15.2

Lymph (Tissue Fluid)

As blood flows through the tiny capillaries within the tissues, it does not stay entirely enclosed. Some of its water, together with many small water-soluble substances, seeps out of the capillaries i…

15.3

Circulatory Pathways

Circulation in animals follows one of two broad patterns — open or closed — and among vertebrates the heart itself varies in the number of chambers it has, which in turn determines how oxygenated and…

15.3.1

Human Circulatory System

The human circulatory system, also known as the blood vascular system, is built from three components working together: a muscular chambered heart, a network of closed, branching blood vessels, and th…

15.3.2

Cardiac Cycle

The cardiac cycle is the orderly, repeating sequence of contraction (systole) and relaxation (diastole) of the atria and ventricles that drives blood through the heart.

15.3.3

Electrocardiogram (ECG)

An electrocardiogram (ECG) is a graphical record of the electrical activity of the heart across a single cardiac cycle.

15.4

Double Circulation

In humans, blood does not move randomly — it follows a fixed route through the blood vessels, and the whole system is arranged as a double circulation, meaning blood passes through the heart twice in…

15.5

Regulation of Cardiac Activity

The heart is capable of regulating its own beating without depending on outside signals, but that intrinsic rhythm can still be adjusted by the nervous system and by hormones.

15.6

Disorders of Circulatory System

Several disorders can affect the heart and blood vessels. The common ones are described below.

Summary

Vertebrates circulate blood, a fluid connective tissue, to carry essential substances to the cells and to remove wastes from them.

Exercises

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Exemplar Problems

Higher-order thinking / exemplar-style practice problems.

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