Body Fluids And Circulation Notes

Introduction

Body fluids and circulation are essential topics in the study of zoology, particularly for students preparing for the NEET exam. Understanding how organisms transport nutrients, gases, and wastes is crucial for comprehending physiological processes. This study note will cover the composition and functions of body fluids, the mechanisms of circulation, and the various components involved in these processes.

Body Fluids

Blood

Blood is the primary circulating fluid in the human body, performing vital functions such as transportation, regulation, and protection.

Composition of Blood

Blood is composed of plasma and formed elements.

1. Plasma:
   • Plasma constitutes about 55% of the blood's volume.
   • It is a straw-colored liquid composed mainly of water (90-92%), with proteins, electrolytes, gases, nutrients, and waste products.
   • Major plasma proteins include albumins, globulins, and fibrinogen.
2. Formed Elements:
   • These include erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).
   • Erythrocytes: They are biconcave, anucleate cells that contain hemoglobin for oxygen transport.
   • Leukocytes: These are nucleated cells involved in immune responses. They are further classified into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).
   • Thrombocytes: Also known as platelets, these are cell fragments that play a crucial role in blood clotting.

Lymph

Lymph is a clear fluid that circulates through the lymphatic system, carrying lymphocytes and other immune cells.

• Composition: Similar to plasma but with lower protein content.
• Functions: It helps in the removal of interstitial fluid, absorption of dietary fats, and immune responses.

Circulatory System

The circulatory system is responsible for the transport of blood and lymph throughout the body. It consists of the heart, blood vessels, and lymphatic vessels.

Types of Circulatory Systems

1. Open Circulatory System:
   • Found in arthropods and most mollusks.
   • Blood is pumped by the heart into the body cavities, where tissues are directly bathed in blood.
2. Closed Circulatory System:
   • Found in annelids, cephalopods, and vertebrates.
   • Blood circulates within a network of blood vessels, providing efficient nutrient and gas exchange.

Human Circulatory System

The human circulatory system is a closed system with a double circulation pathway, ensuring efficient oxygenation of blood and nutrient distribution.

Heart

The heart is a muscular organ responsible for pumping blood throughout the body.

• Structure: It has four chambers—two atria and two ventricles.
• Valves: Ensure unidirectional flow of blood. These include the tricuspid valve, bicuspid (mitral) valve, pulmonary valve, and aortic valve.

Blood Vessels

Blood vessels form a closed network for blood circulation.

1. Arteries: Carry oxygenated blood away from the heart (except pulmonary arteries).
2. Veins: Carry deoxygenated blood towards the heart (except pulmonary veins).
3. Capillaries: Microscopic vessels where exchange of gases, nutrients, and wastes occurs.

Blood Pressure

Blood pressure is the force exerted by circulating blood on the walls of blood vessels.

• Systolic Pressure: Pressure during heart contraction.
• Diastolic Pressure: Pressure during heart relaxation.

$$ \text{Blood Pressure} = \frac{\text{Systolic Pressure}}{\text{Diastolic Pressure}} $$

Conclusion

Understanding body fluids and circulation is fundamental to grasping how organisms maintain homeostasis and respond to their environment. This knowledge is crucial for NEET aspirants aiming to excel in zoology.