Body fluids and blood circulation

BODY FLUIDS AND CIRCULATION

  • Cells require nutrients, oxygen (O2), and removal of waste.

  • Different organisms have evolved methods to transport these substances.

    • Simple organisms (e.g., sponges) circulate water through body cavities.

    • Higher organisms (e.g., humans) use blood and lymph for transport.

15.1 BLOOD

General Composition

  • Blood: connective tissue with a fluid matrix and formed elements.

  • Plasma: 55% of blood, contains 90-92% water, 6-8% proteins (albumins, globulins, fibrinogen).

Plasma Functions

  • Fibrinogen: coagulation.

  • Globulins: defense.

  • Albumins: osmotic balance.

  • Contains minerals and nutrients.

Formed Elements

  • Erythrocytes (RBC), leucocytes (WBC), platelets make up ~45% of blood.

Erythrocytes

  • Most abundant, biconcave, no nucleus, contain hemoglobin (12-16 gms/100 ml).

  • Lifespan: 120 days, destroyed in the spleen.

Leucocytes

  • Two categories: granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).

  • Neutrophils: most abundant (60-65%); involved in phagocytosis.

  • Lymphocytes: immune response (20-25%).

Platelets

  • Fragments from megakaryocytes; crucial for clotting (1,500,000-3,500,000/mm3).

Blood Groups

ABO System

  • Grouping based on antigens A and B.

  • Compatibility crucial for transfusions (O: universal donor, AB: universal recipient).

Rh Grouping

  • Rh+ve (80% of humans) vs. Rh-ve; exposure to mismatched blood can cause complications (erythroblastosis foetalis).

Coagulation of Blood

  • Process helps prevent blood loss after injury.

  • Clot formation involves fibrinogen, thrombin, and prothrombin, with calcium ions playing a key role.

15.2 LYMPH (TISSUE FLUID)

  • Interstitial fluid is derived from blood and facilitates exchange of substances between blood and cells.

  • Collected by lymphatic system, contains lymphocytes.

15.3 CIRCULATORY PATHWAYS

  • Two types: open (arthropods) and closed (vertebrates).

  • Structure: muscular heart and closed blood vessels.

  • Fish: 2-chambered heart, amphibians/reptiles: 3-chambered heart, birds/mammals: 4-chambered heart.

15.3.1 Human Circulatory System

  • Composed of heart, vessels, and blood.

  • Heart: four chambers (atria and ventricles), contains valves to ensure unidirectional blood flow.

15.3.2 Cardiac Cycle

  • Sequence of events during a heartbeat: diastole and systole.

  • Average heart rate: 70-75 beats/min (stroke volume: ~70 mL).

  • Cardiac output: volume of blood per minute (5 liters).

15.3.3 Electrocardiograph (ECG)

  • Measures electrical activity of the heart; P-wave, QRS complex, T-wave.

  • Clinical significance for diagnosing heart conditions.

15.4 DOUBLE CIRCULATION

  • Distinction between pulmonary (lungs) and systemic (body tissues) circulation.

  • Unique hepatic portal system connects digestive tract and liver.

15.5 REGULATION OF CARDIAC ACTIVITY

  • Heart activities are auto-regulated by nodal tissues.

  • Can be moderated by autonomic nervous system and hormones.

15.6 DISORDERS OF CIRCULATORY SYSTEM

  • Hypertension: blood pressure above normal (140/90).

  • Coronary artery disease: caused by arterial blockage.

  • Angina: chest pain due to insufficient oxygen to heart muscle.

  • Heart failure: ineffective blood pumping.

SUMMARY

  • Blood circulates nutrients, O2, and wastes; lymph assists in transport.

  • Components of blood: plasma and formed elements (RBCs, WBCs, platelets); grouped by ABO and Rh systems.

  • Closed circulatory system functions through a pumping heart.

  • Cardiac cycle consists of rhythmic systoles and diastoles; ECG monitors heart activity.