Composition of Blood

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Topic: BLOOD COMPOSITION

Presented by:
Abdullah & Yousufxt

Class: XI -A School:
New Indian School

Learning objective

By the end of the lesson, students will be able to identify and explain the four major components of blood—plasma, RBCs, WBCs, and platelets—and state their functions with at least 80% accuracy using a blood-composition model.

Text

Use this to surface prior knowledge and misconceptions before the lesson begins. Likely responses may include oxygen, red, heart, cells, veins, clotting, plasma or life.

What is blood?

Blood is a fluid connective tissue that circulates through blood vessels.

It is made of two main parts:

• Plasma

• Formed elements

A simple summary is:

Blood = Plasma + Formed elements

Why blood matters

• transports oxygen and nutrients

• removes carbon dioxide and wastes

• protects against infection

• helps blood clot

• helps maintain body balance

Two major components

• Plasma is the liquid part of blood.

• Formed elements are the cells and cell fragments in blood.

• Plasma makes up about 55% of blood.

• Formed elements make up about 45% of blood.

Plasma

Plasma is the pale yellow liquid part of blood.

It makes up about 55% of blood and acts as the medium that carries dissolved substances around the body.

What plasma contains

• 90–92% water

• proteins

• minerals

• nutrients

• hormones

• gases and waste products

Plasma proteins

The three major plasma proteins are:

• Albumin

• Globulins

• Fibrinogen

Each has a different role in keeping the blood and body functioning normally.

Functions of plasma proteins

Albumin

Maintains the osmotic balance of blood, helping keep the right amount of water inside blood vessels.

Globulins and fibrinogen

Globulins help in defence and immunity.

Fibrinogen helps in blood clotting.

If needed, explain osmotic balance simply as preventing too much water from leaving the blood into surrounding tissues.

Complete the plasma summary

Blood has two main parts: plasma and formed elements. Plasma is the liquid part of blood and makes up about 55% of it. One major plasma protein is albumin, which helps maintain osmotic balance in the blood.

liquid

55%

osmotic balance

45%

clotting

nucleus

solid

All three blanks come directly from the plasma block. Remind students that albumin is linked with water balance, not immunity or clotting.

Formed elements

Formed elements make up about 45% of blood.

They include:

• Red blood cells (RBCs)

• White blood cells (WBCs)

• Platelets

Each component has a different function.

Red blood cells

• also called erythrocytes

• most abundant blood cells

• biconcave in shape

• mature human RBCs have no nucleus

How RBCs work

The main function of RBCs is to transport oxygen from the lungs to body tissues.

They also carry some carbon dioxide back to the lungs.

RBC → Haemoglobin → Oxygen transport

Haemoglobin

Haemoglobin is the red pigment inside RBCs.

It binds with oxygen and allows oxygen to be carried in the blood.

RBC life cycle

• produced mainly in the red bone marrow

• average lifespan is about 120 days

• old RBCs are removed mainly by the spleen and liver

What allows RBCs to carry oxygen in the blood?

A

Haemoglobin

B

Fibrinogen

C

Globulins

D

Platelets

Uses nearby confusable terms from the lesson: fibrinogen and globulins are plasma proteins, not the oxygen-carrying pigment in RBCs.

Complete the RBC description

Red blood cells are also called erythrocytes and their main job is to transport oxygen . They are produced mainly in the red bone marrow and usually live for about 120 days .

erythrocytes

oxygen

red bone marrow

120 days

leucocytes

carbon dioxide

liver

45 days

A recap of the full RBC block: name, function, production site and lifespan.

White blood cells

• also called leucocytes

• have a nucleus

• protect the body from infection and foreign substances WBC defence roles Granulocytes Agranulocytes neutrophils monocytes

Types of WBC

Granulocytes

• neutrophils

• eosinophils

• basophils

• lymphocytes

• monocytes

Agranulocytes

WBC defence roles

• Neutrophils can destroy bacteria by engulfing them.

• Lymphocytes are important in specific immune responses.

• Some lymphocytes help produce antibodies.

WBC → Defence and immunity

Platelets

• also called thrombocytes

• small, irregularly shaped cell fragments

• main role: blood clotting

How platelets help

When a blood vessel is damaged, platelets gather at the injured area and help form a clot.

This reduces blood loss and helps the wound begin to heal.

Platelets → Blood clotting

Quick comparison

RBC and WBC

Platelets - help blood clot

A simple memory aid:

Transport, Protection, Clotting

Platelets

RBCs - transport oxygen

WBCs - protect against infection

Which blood component helps stop bleeding after a cut?

A

Globulins

B

Platelets

C

Lymphocytes

D

Haemoglobin

Tests whether students can distinguish clotting from immunity and oxygen transport.

Which formed element is easiest for you to remember?

1

RBCs

2

WBCs

3

Platelets

Why blood is red

Blood is red because of haemoglobin in RBCs.

With more oxygen, blood is bright red.

With less oxygen, blood is darker red.

Blood groups

Two important blood group systems are:

• ABO system

• Rh system

The ABO groups are A, B, AB and O.

The Rh system classifies blood as Rh-positive or Rh-negative.

Why blood groups matter

Blood grouping is important during blood transfusion.

If incompatible blood is mixed, it can cause dangerous reactions.

Matching donor and recipient blood helps transfusion happen safely.

Composition of blood

Blood is a complex connective tissue made of plasma and formed elements.

Plasma carries dissolved substances.

RBCs transport oxygen.

WBCs provide defence.

Platelets help blood clot.

Use this as the closing summary before moving to key terms.

Why is blood red?

A

Plasma water

B

White blood cells

C

Haemoglobin

D

Platelet clots

Checks the idea from slide 20 that haemoglobin in RBCs gives blood its red colour.

Complete the final summary

Blood is made of plasma and formed elements. In the ABO system, the blood groups are A, B, AB and O . Blood groups matter during a blood transfusion because incompatible blood can cause dangerous reactions.

plasma

blood transfusion

Rh

platelets

immunity

haemoglobin

Combines the closing ideas: overall composition plus the purpose of blood grouping.

Glossary

blood - A fluid connective tissue that circulates through blood vessels.

plasma - The pale yellow liquid part of blood.

formed elements - The cellular part of blood, including RBCs, WBCs and platelets.

red blood cells (RBCs) - Blood cells that mainly transport oxygen.

haemoglobin - The red pigment in RBCs that binds with oxygen.

white blood cells (WBCs) - Blood cells that protect the body from infection.

platelets - Small cell fragments that help blood clot.

globulins - Plasma proteins involved in defence and immunity.

fibrinogen - A plasma protein needed for blood clotting.

erythrocytes - Another name for red blood cells.

leucocytes - Another name for white blood cells.

thrombocytes - Another name for platelets.

blood transfusion - The transfer of blood from a donor to a recipient