📝 Chapter Notes & Revision

Body Fluids and Circulation

🏫 MP BoardClass 11Biology

📐 Formula & Cheat Sheet (English)

Quick Revision Notes: Class 11 Biology

Chapter: Body Fluids and Circulation

1. Introduction

  • Body Fluids: Circulatory systems transport essential nutrients, oxygen, and waste products to and from cells.
  • Types of Circulatory Systems:
    • Open Circulatory System: Blood flows in open spaces or sinuses (e.g., Arthropods, Molluscs).
    • Closed Circulatory System: Blood flows through a closed network of vessels (e.g., Annelids, Chordates).

2. Blood (Fluid Connective Tissue)

Blood consists of a fluid matrix (Plasma) and Formed Elements (Blood cells).

A. Plasma (55% of Blood)

  • Composition: 90-92% water, 6-8% proteins (Fibrinogen, Globulins, Albumins).
  • Proteins & Functions:
    • Fibrinogen: Needed for blood clotting (coagulation).
    • Globulins: Primarily involved in defense mechanisms (antibodies).
    • Albumins: Help in osmotic balance.
  • Also contains minerals ($Na^+$, $Ca^{2+}$, $Mg^{2+}$, $HCO_3^-$, etc.) and glucose, amino acids, and lipids.

B. Formed Elements (45% of Blood)

  1. Erythrocytes (RBCs):

    • Most abundant of all blood cells.
    • Formed in the red bone marrow in adults.
    • Biconcave, devoid of nucleus in humans (except camels, llamas).
    • Contain iron-containing protein hemoglobin (Hb).
    • Lifespan: 120 days.
    • Function: Transport of $O_2$ and $CO_2$.
    • Normal Count: 5 to 5.5 million $mm^{-3}$ of blood.

  2. Leucocytes (WBCs):

    • Colorless, nucleated, amoeboid.
    • Normal Count: 6,000 to 8,000 $mm^{-3}$ of blood.
    • Divided into two main categories:
      • Granulocytes: Neutrophils, Eosinophils, Basophils.
      • Agranulocytes: Lymphocytes, Monocytes.
    • Functions: Phagocytosis, immune response, and inflammation.

  3. Thrombocytes (Platelets):

    • Cell fragments produced from megakaryocytes (special cells in bone marrow).
    • Normal Count: 1,50,000 to 3,50,000 $mm^{-3}$.
    • Function: Release clotting factors essential for blood coagulation.

3. Blood Groups

A. ABO Grouping

Based on the presence or absence of surface antigens on RBCs (Antigen A and Antigen B).

  • Group A: Antigen A, Antibody anti-B
  • Group B: Antigen B, Antibody anti-a
  • Group AB: Both Antigens A & B, No antibodies (Universal Recipient)
  • Group O: No antigens, Both anti-a & anti-b antibodies (Universal Donor)

B. Rh Grouping

  • Rh factor (similar to Rhesus monkey antigen) is observed on the surface of RBCs in ~80% of humans.
  • Rh-positive ($Rh^+$): Antigen present.
  • Rh-negative ($Rh^-$): Antigen absent.
  • Erythroblastosis Foetalis: Hemolytic disease of the newborn occurring when an $Rh^-$ mother carries an $Rh^+$ fetus.

4. Lymph (Tissue Fluid)

  • As blood passes through capillaries, some water and soluble substances leak out into the spaces between tissue cells, forming Tissue Fluid (Interstitial Fluid).
  • It has the same mineral distribution as plasma.
  • Lymphatic System: A network of vessels that collects this fluid and drains it back into the major veins.
  • Functions:
    • Carrier for nutrients, hormones, etc.
    • Fat absorption in the intestine via lacteals.
    • Immune defense through lymphocytes.

5. Human Circulatory System

  • Consists of a muscular chambered heart, a closed branching network of blood vessels, and blood.

A. Human Heart Anatomy

  • Origin: Mesodermal in origin.
  • Location: Thoracic cavity, in between the two lungs, slightly tilted to the left.
  • Covering: Protected by a double-walled membrane called Pericardium.
  • Chambers: 4 chambers – Two upper Atria (Auricles) and two lower Ventricles.
  • Valves:
    • Tricuspid Valve: Between Right Atrium and Right Ventricle.
    • Bicuspid (Mitral) Valve: Between Left Atrium and Left Ventricle.
    • Semilunar Valves: At the openings of the right ventricle into the pulmonary artery and the left ventricle into the aorta.

6. Cardiac Cycle

The sequential events in the heart which cyclically repeat are called the cardiac cycle. It consists of systole (contraction) and diastole (relaxation) of atria and ventricles.

  • Duration: 0.8 seconds.
  • Steps:
    1. Joint Diastole (0.4 sec): All four chambers are in a relaxed state. Blood flows freely from atria into ventricles.
    2. Atrial Systole (0.1 sec): Atria contract, increasing the flow of blood into ventricles by about 30%.
    3. Ventricular Systole (0.3 sec): Ventricles contract, closing tricuspid/bicuspid valves (producing 'Lub' sound) and opening semilunar valves to pump blood into vessels.
  • Stroke Volume: Volume of blood pumped out by each ventricle per beat $\approx 70\text{ mL}$.
  • Cardiac Output: Volume of blood pumped out by each ventricle per minute. $$\text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate}$$ $$\text{Cardiac Output} = 70\text{ mL} \times 72\text{ beats/min} \approx 5000\text{ mL} \text{ or } 5\text{ Liters}$$

7. Electrocardiograph (ECG)

  • A graphical representation of the electrical activity of the heart during a cardiac cycle.
  • Standard ECG Waves:
    • P-wave: Represents depolarization (excitation) of the atria, leading to atrial systole.
    • QRS complex: Represents depolarization of the ventricles, initiating ventricular systole.
    • T-wave: Represents repolarization of ventricles (return to normal state).

8. Double Circulation

  • Blood flows twice through the heart in one complete cycle (seen in humans, birds, and mammals).
    1. Pulmonary Circulation: Right Ventricle $\rightarrow$ Pulmonary Artery $\rightarrow$ Lungs $\rightarrow$ Pulmonary Veins $\rightarrow$ Left Atrium. (Oxygenation of blood).
    2. Systemic Circulation: Left Ventricle $\rightarrow$ Aorta $\rightarrow$ Tissues $\rightarrow$ Vena Cava $\rightarrow$ Right Atrium. (Nutrient/gas exchange with body tissues).
  • Hepatic Portal System: A unique vascular connection between the digestive tract and liver before blood returns to the systemic circulation.
  • Coronary System: Circulation of blood exclusively to and from the heart musculature itself.

9. Regulation of Cardiac Activity

  • Neural Regulation: Autonomic Nervous System (ANS) can moderate the cardiac output through the medulla oblongata.
    • Sympathetic nerves: Increase heart rate and cardiac output.
    • Parasympathetic (Vagus) nerve: Decrease heart rate and cardiac output.
  • Hormonal Regulation: Adrenal medullary hormones (Adrenaline and Noradrenaline) can increase cardiac output.

10. Disorders of the Circulatory System

  • High Blood Pressure (Hypertension): Normal blood pressure is $120/80\text{ mmHg}$. If BP is persistently $140/90\text{ mmHg}$ or higher, it is hypertension. It harms vital organs like brain and kidneys.
  • Coronary Artery Disease (CAD) / Atherosclerosis: Often referred to as "atherosclerosis," it affects the vessels supplying blood to the heart muscle due to deposits of calcium, fat, cholesterol, and fibrous tissue.
  • Angina Pectoris: A chest pain occurring when no enough oxygen is reaching the heart muscle.
  • Heart Failure: State of heart when it is not pumping blood effectively enough to meet the needs of the body (often called congestive heart failure).