Chapter 15: Body Fluids and Circulation

Introduction

• Living cells require nutrients, O₂, and removal of wastes.
• Efficient mechanisms for substance movement are essential.
• Simple organisms use body cavities for circulation; complex organisms use fluids like blood and lymph.
• Blood and lymph composition, properties, and circulation mechanisms discussed.

15.1 Blood

15.1.1 Plasma

• Straw-colored, viscous fluid; 55% of blood.
• Composed of 90-92% water, 6-8% proteins (fibrinogen, globulins, albumins).
  • Fibrinogen: Clotting
  • Globulins: Defense
  • Albumins: Osmotic balance
• Contains minerals (Na⁺, Ca²⁺, etc.), glucose, amino acids, lipids.
• Serum: Plasma without clotting factors.

15.1.2 Formed Elements

• Erythrocytes (RBCs): Abundant, lack nucleus, contain hemoglobin, lifespan ~120 days.
• Leucocytes (WBCs): Nucleated, defense functions, types include:
  • Granulocytes: Neutrophils, eosinophils, basophils
  • Agranulocytes: Lymphocytes (B & T), monocytes
• Platelets: Cell fragments, involved in clotting.

15.1.3 Blood Groups

• ABO Grouping: Based on antigens A and B.
• Rh Grouping: Presence of Rh antigen (Rh+ or Rh-).
• Universal donors: O group.
• Universal recipients: AB group.
• Rh incompatibility can lead to erythroblastosis foetalis.

15.1.4 Coagulation of Blood

• Coagulation prevents excessive blood loss.
• Involves conversion of fibrinogen to fibrin.
• Calcium ions play a crucial role.

15.2 Lymph (Tissue Fluid)

• Interstitial fluid formed from blood plasma.
• Collected by lymphatic system and returned to veins.
• Contains lymphocytes, important for immune response.
• Absorbs fats via lacteals in intestines.

15.3 Circulatory Pathways

15.3.1 Human Circulatory System

• Composed of heart, blood vessels, blood.
• Heart structure: four chambers, valves (tricuspid, bicuspid, semilunar).
• Nodal tissue: SAN (pacemaker), AVN.

15.3.2 Cardiac Cycle

• Sequence: Joint diastole, atrial systole, ventricular systole.
• Cardiac output = Stroke volume x heart rate.
• Heart sounds: lub (tricuspid/bicuspid closure), dub (semilunar closure).

15.3.3 Electrocardiogram (ECG)

• Graph of heart's electrical activity.
• P-wave: Atrial depolarization.
• QRS complex: Ventricular depolarization.
• T-wave: Ventricular repolarization.

15.4 Double Circulation

• Pulmonary circulation: Right ventricle → Lungs → Left atrium.
• Systemic circulation: Left ventricle → Body → Right atrium.
• Benefits: No mixing of oxygenated and deoxygenated blood.

15.5 Regulation of Cardiac Activity

• Intrinsic regulation by nodal tissue, called myogenic.
• ANS alters heart rate and output.
• Sympathetic: Increases rate and contraction.
• Parasympathetic: Decreases rate and contraction.
• Adrenal hormones can increase output.

15.6 Disorders of Circulatory System

• Hypertension: High blood pressure.
• Coronary Artery Disease: Narrowing of heart arteries.
• Angina: Chest pain from low oxygen to heart.
• Heart Failure: Ineffective pumping of blood.

Summary

• Blood and lymph are essential in substance transport.
• Heart functions by sequential systolic and diastolic cycles.
• Double circulation prevents the mixing of different blood types.
• ECG is used to monitor heart activity.
• Heart activity is moderated by neural and hormonal influences.