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Important Notes For NEET Biology – Body Fluids and Circulation

Blood

Composition of Blood:

Composition of Blood
  • Blood is a fluid connective tissue consisting of cells (RBCs, WBCs, and platelets).
  • Plasma constitutes 55% of blood volume. It is a viscous fluid containing 90-92% water, 6-8% proteins (fibrinogens, albumins, globulins), amino acids, glucose, and electrolytes (Na+, Ca++, Cl–).
  • Formed Elements include erythrocytes, leukocytes, and platelets.

Erythrocytes (RBCs):

  • Most abundant cells in blood.
  • Formed in bone marrow, biconcave, anucleate.
  • Lifespan of 120 days, destroyed in the spleen.

Leukocytes (WBCs):

Leukocytes (WBCs)
  • Colorless due to the absence of hemoglobin.
  • Life span of 3-4 days.
  • Granulocytes: Neutrophils, Eosinophils, Basophils.
  • Agranulocytes: Lymphocytes, Monocytes.

Blood Platelets (Thrombocytes):

  • Formed from megakaryocytes in bone marrow.
  • Involved in blood clotting.

Blood Groups

Blood Groups

ABO Blood Group System:

  • Four types: A, B, AB, O.
  • Based on surface antigens on RBCs (A and B antigens).
  • Blood Group A: Antigen A, Anti-B antibodies.
  • Blood Group B: Antigen B, Anti-A antibodies.
  • Blood Group AB: Antigens A and B, no antibodies (universal acceptor).
  • Blood Group O: No antigens, Anti-A and Anti-B antibodies (universal donor).

Rh Grouping:

  • Rh antigen present in 80% of people (Rh+).
  • Erythroblastosis fetalis: Mother is Rh–, father is Rh+, fetus is Rh+. The condition can be managed by administering anti-Rh antibodies to the mother after the first childbirth.

Coagulation of Blood

  • Blood clotting prevents excessive blood loss from injuries.
  • Clot consists of fibrin, which traps blood cells.
  • Clotting process:
    • Inactive fibrinogen → Fibrin (by Thrombin).
    • Prothrombin → Thrombin (by Thrombokinase).
  • Ca++ is crucial in the coagulation process.

Lymph

  • Lymph is a fluid connective tissue that drains interstitial fluid back to major veins.
  • Contains lymphocytes, part of the immune system.
  • Absorbs fats in the intestine through lacteals and transports them to blood.

Circulatory Pathways

Types:

  • Open Circulatory System: Blood is in open cavities (sinuses), found in arthropods and molluscs.
  • Closed Circulatory System: Blood circulates in vessels, found in annelids and chordates.

Human Circulatory System:

Human Circulatory System
  • Heart: Four-chambered, mesodermal origin, located between lungs in the thoracic cavity, protected by pericardium.
  • Heart Structure:
    • Valves: Bicuspid (mitral) between left atrium and ventricle; Tricuspid between right atrium and ventricle; Semilunar at openings of pulmonary artery and aorta.
    • Nodal Tissue: SAN (pacemaker), AVN, Bundle of His, Purkinje fibers.
    • Blood Vessels: Arteries, veins, and capillaries; made of tunica intima, media, and externa.

Cardiac Cycle

Cardiac Cycle
  • Joint Diastole: All four chambers relaxed.
  • Atrial Systole: SAN initiates contraction.
  • Ventricular Systole: AVN transfers action potential, ventricles contract.
  • Ventricular Diastole: Semilunar valves close.
  • Stroke Volume: Blood pumped by each ventricle per cycle (~70 ml).
  • Cardiac Output: Total blood output per minute (~5 L).

Heart Sounds:

  • Lub: Closure of bicuspid and tricuspid valves during ventricular systole.
  • Dub: Closure of semilunar valves during ventricular diastole.

Electrocardiogram (ECG)

Electrocardiogram (ECG)
  • P Wave: Atrial depolarization.
  • QRS Complex: Ventricular depolarization.
  • T Wave: Ventricular repolarization.
  • Measures heart rate and detects abnormalities.

Double Circulation

  • Pulmonary Circulation: Deoxygenated blood to lungs via pulmonary artery; oxygenated blood to left atrium via pulmonary vein.
  • Systemic Circulation: Oxygenated blood from left ventricle to body; deoxygenated blood returns to right atrium.

Hepatic Portal System: Connects liver and digestive tract, transporting nutrients.

Regulation of Cardiac Activity

  • Myogenic Heart: Activity regulated by nodal tissue.
  • ANS Regulation: Sympathetic (increases rate) and parasympathetic (decreases rate) neural signals from medulla oblongata.

Disorders of the Circulatory System

  • Hypertension: High blood pressure (>140/90 mm Hg).
  • Coronary Artery Disease (CAD): Narrowing of arteries due to plaque.
  • Angina: Chest pain due to insufficient oxygen to heart muscles.
  • Heart Failure: Inability to pump sufficient blood.
  • Coronary Thrombosis: Clot in coronary artery leading to heart attack.

FAQs

What is the difference between pulmonary and systemic circulation?2024-08-30T16:47:51+05:30

Pulmonary circulation involves the exchange of gases in the lungs, while systemic circulation supplies oxygenated blood to the body and returns deoxygenated blood to the heart.

What causes hypertension?2024-08-30T16:47:18+05:30

Hypertension is caused by factors like genetics, lifestyle, stress, and underlying health conditions.

What is an electrocardiogram (ECG)?2024-08-30T16:46:55+05:30

An ECG is a graphical representation of the electrical activity of the heart used to detect heart conditions.

How does the heart regulate its own activity?2024-08-30T16:46:37+05:30

The heart’s activity is regulated by the sinoatrial node (pacemaker) and the autonomic nervous system.

What is the significance of the Rh factor in blood transfusions?2024-08-30T16:46:16+05:30

The Rh factor determines compatibility for blood transfusions; mismatched Rh factors can lead to immune reactions.

How is oxygen transported in the blood?2024-08-30T16:45:57+05:30

Oxygen is primarily transported by hemoglobin in red blood cells.

What are the main components of blood?2024-08-30T16:45:36+05:30

Blood consists of plasma (fluid part) and formed elements (RBCs, WBCs, and platelets).

What is the primary function of blood?2024-08-30T16:44:21+05:30

Blood transports oxygen, nutrients, hormones, and waste products throughout the body.

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