Body Fluids and Circulation

Key Concepts

Composition of Blood

Blood is a special connective tissue consisting of a fluid matrix (plasma) and formed elements.

Plasma (55%): A straw-colored viscous fluid. 90-92% water, 6-8% proteins (Fibrinogen for clotting, Globulins for defense, Albumins for osmotic balance). Plasma without clotting factors is called Serum.
Formed Elements (45%):
- Erythrocytes (RBCs): Biconcave, lack nucleus (in most mammals), contain haemoglobin for gas transport. Life span: 120 days.
- Leucocytes (WBCs): Nucleated, part of the immune system. Includes Granulocytes (Neutrophils, Eosinophils, Basophils) and Agranulocytes (Lymphocytes, Monocytes).
- Platelets (Thrombocytes): Cell fragments from megakaryocytes involved in blood coagulation.

Blood Groups and Coagulation

ABO Grouping: Based on A and B antigens on RBCs. Group O is the universal donor; AB is the universal recipient.
Rh Grouping: Based on the Rh antigen. Erythroblastosis foetalis occurs when an Rh-ve mother carries an Rh+ve foetus.
Coagulation (Clotting): A "cascade" process. Prothrombin is converted to Thrombin (by thrombokinase), which converts Fibrinogen to Fibrin threads that trap dead cells to form a clot. Calcium ions are essential.

Human Circulatory System

Heart Anatomy: A 4-chambered muscular organ tilted to the left. Protected by the pericardium.
- Valves: Tricuspid (right side), Bicuspid/Mitral (left side), and Semilunar valves prevent backward flow.
- Nodal Tissue: The Sino-atrial node (SAN) is the pacemaker as it generates the maximum action potentials (70-75/min).

The Pacemaker The SAN can generate action potentials without any external stimuli, making the heart 'myogenic'. This intrinsic rhythm is what maintains the heart's steady beat.

Cardiac Cycle: Includes Atrial systole, Ventricular systole, and Joint diastole. Duration: 0.8 seconds.
Cardiac Output: Stroke volume (70 mL) $\times$ Heart rate ( $\approx 72$ bpm) $\approx 5$ Litres/min.
Heart Sounds: 'Lub' (closure of tricuspid/bicuspid valves) and 'Dub' (closure of semilunar valves).

Electrocardiogram (ECG)

A graphical representation of the heart's electrical activity.

P-wave: Depolarisation (excitation) of atria.
QRS complex: Depolarisation of ventricles (marks beginning of systole).
T-wave: Repolarisation (return to normal) of ventricles.

Double Circulation

Humans possess two separate circulatory pathways:

Pulmonary Circulation: Right ventricle $\rightarrow$ Pulmonary artery $\rightarrow$ Lungs $\rightarrow$ Pulmonary veins $\rightarrow$ Left atrium.
Systemic Circulation: Left ventricle $\rightarrow$ Aorta $\rightarrow$ Body tissues $\rightarrow$ Vena cava $\rightarrow$ Right atrium.

Hepatic Portal System: A unique vascular connection between the digestive tract and the liver.

Regulation and Disorders

Regulation: The heart is myogenic (auto-regulated). The medulla oblongata can moderate activity via the Autonomic Nervous System (ANS).
Hypertension: Blood pressure higher than normal (e.g., 140/90).
Coronary Artery Disease (CAD): Atherosclerosis; narrowing of arteries due to deposits.
Angina Pectoris: Acute chest pain due to inadequate oxygen reaching the heart.
Heart Failure: Heart not pumping blood effectively; often involves lung congestion.

Activities

Measure your pulse rate and notice its rhythm.
Learn about the "universal donor" and "universal recipient" concepts through a blood donation drive.
Draw a diagram of the human heart and trace the path of blood during double circulation. re:** Heart not pumping blood effectively; often involves lung congestion.

Activities

Measure your pulse rate and notice its rhythm.
Learn about the "universal donor" and "universal recipient" concepts through a blood donation drive.
Draw a diagram of the human heart and trace the path of blood during double circulation.

Key Concepts

Blood is a special connective tissue consisting of a fluid matrix (plasma) and formed elements.

Plasma (55%): A straw-colored viscous fluid. 90-92% water, 6-8% proteins (Fibrinogen for clotting, Globulins for defense, Albumins for osmotic balance). Plasma without clotting factors is called Serum.

Formed Elements (45%):

Erythrocytes (RBCs): Biconcave, lack nucleus (in most mammals), contain haemoglobin for gas transport. Life span: 120 days.
Leucocytes (WBCs): Nucleated, part of the immune system. Includes Granulocytes (Neutrophils, Eosinophils, Basophils) and Agranulocytes (Lymphocytes, Monocytes).
Platelets (Thrombocytes): Cell fragments from megakaryocytes involved in blood coagulation.

ABO Grouping: Based on A and B antigens on RBCs. Group O is the universal donor; AB is the universal recipient.

Rh Grouping: Based on the Rh antigen. Erythroblastosis foetalis occurs when an Rh-ve mother carries an Rh+ve foetus.

Coagulation (Clotting): A "cascade" process. Prothrombin is converted to Thrombin (by thrombokinase), which converts Fibrinogen to Fibrin threads that trap dead cells to form a clot. Calcium ions are essential.

Heart Anatomy: A 4-chambered muscular organ tilted to the left. Protected by the pericardium.

Valves: Tricuspid (right side), Bicuspid/Mitral (left side), and Semilunar valves prevent backward flow.
Nodal Tissue: The Sino-atrial node (SAN) is the pacemaker as it generates the maximum action potentials (70-75/min).

The Pacemaker The SAN can generate action potentials without any external stimuli, making the heart 'myogenic'. This intrinsic rhythm is what maintains the heart's steady beat.

Cardiac Cycle: Includes Atrial systole, Ventricular systole, and Joint diastole. Duration: 0.8 seconds.

Cardiac Output: Stroke volume (70 mL)

\times

Heart rate (

\approx 72

bpm)

\approx 5

Litres/min.

Heart Sounds: 'Lub' (closure of tricuspid/bicuspid valves) and 'Dub' (closure of semilunar valves).

A graphical representation of the heart's electrical activity.

P-wave: Depolarisation (excitation) of atria.

QRS complex: Depolarisation of ventricles (marks beginning of systole).

T-wave: Repolarisation (return to normal) of ventricles.

Humans possess two separate circulatory pathways:

Pulmonary Circulation: Right ventricle

\rightarrow

Pulmonary artery

\rightarrow

Lungs

\rightarrow

Pulmonary veins

\rightarrow

Left atrium.

Systemic Circulation: Left ventricle

\rightarrow

Aorta

\rightarrow

Body tissues

\rightarrow

Vena cava

\rightarrow

Right atrium.

Hepatic Portal System: A unique vascular connection between the digestive tract and the liver.

Regulation: The heart is myogenic (auto-regulated). The medulla oblongata can moderate activity via the Autonomic Nervous System (ANS).

Hypertension: Blood pressure higher than normal (e.g., 140/90).

Coronary Artery Disease (CAD): Atherosclerosis; narrowing of arteries due to deposits.

Angina Pectoris: Acute chest pain due to inadequate oxygen reaching the heart.

Heart Failure: Heart not pumping blood effectively; often involves lung congestion.

Activities

Measure your pulse rate and notice its rhythm.

Learn about the "universal donor" and "universal recipient" concepts through a blood donation drive.

Draw a diagram of the human heart and trace the path of blood during double circulation. re:** Heart not pumping blood effectively; often involves lung congestion.

Body Fluids and Circulation

Body Fluids and Circulation

Key Concepts

Composition of Blood

Blood Groups and Coagulation

Human Circulatory System

Electrocardiogram (ECG)

Double Circulation

Regulation and Disorders

Activities

Activities

On this page

Body Fluids and Circulation

Body Fluids and Circulation

Key Concepts

Composition of Blood

Blood Groups and Coagulation

Human Circulatory System

Electrocardiogram (ECG)

Double Circulation

Regulation and Disorders

Activities

Activities

On this page