Topics to be Learn : 

  • Respiration
  • Organs of respiratory exchange
  • Human respiratory system
  • Mechanism of respiration
  • Regulation of breathing
  • Modified respiratory movements
  • Common disorders of respiratory system
  • Transportation in living organisms
  • Circulation in animals
  • Circulatory system in human
  • Red blood corpuseles / erythrocytes
  • White blood corpuseles / leucocytes
  • Thrombocytes / platelets
  • Heart
  • Working mechanism of human heart
  • Blood vessels
  • Blood Pressure (BR)
  • Electrocardiogram
  • Lymphatic system
Respiration:
  • Definition: Biochemical process of oxidation of organic compounds for liberation of chemical energy as ATP.
  • Formula: C6H12O6 + 6O2 → 6CO2 + 6H2O + 38 ATP
  • Features of Respiratory Surface:
    • Large surface area
    • Thin, highly vascular, permeable
    • Moist surfaces

Organs of Respiratory Exchange:

  • Plants: Stomata on leaves, lenticels on stem.
  • Animals: Specialized based on organization complexity.

Respiratory Organs in Different Organisms:

1) Aquatic Organisms:

  • Protists, Sponges, Coelenterates: Plasma membrane
  • Limulus (Arthropod): Book gills
  • Amphibian Tadpoles, Fish: External/ internal gills
  • Flatworms, Annelids: Plasma membrane, moist skin

2) Terrestrial Organisms:

  • Insects: Tracheal tubes, spiracles
  • Arachnids: Book lungs
  • Reptiles, Birds, Mammals: Lungs

3) Underwater Organisms:

  • Turtles: Cloaca (accessory air bladders for underwater respiration)
Human Respiratory System:

  1. 1) Nostrils and Nasal Chambers:

    • Nostrils: External openings of the nose.
    • Function: Oxygen intake, CO2 and water vapor release.
    • Nasal Chambers: Lined with mucous membrane, ciliated epithelium.
      • Divided into right and left by mesethmoid cartilage.
      • Regions: Vestibule (dust prevention), Respiratory (warms and moistens air), Sensory (smell detection).

  2. 2) Pharynx:

    • Structure: Short, vertical tube (~12 cm).
    • Crossroads: Respiratory and food passages intersect.
    • Parts: Naso-pharynx (air passage), Laryngo-pharynx/Oro-pharynx (food passage).
    • Tonsils: Made of lymphatic tissue, kill bacteria trapped in mucus.
    3) Larynx:
  3.   
    • Function: Produces sound.
    • Adam’s Apple: Enlargement in males at puberty.
    • Glottis: Opening through which air enters.
    • Epiglottis: Guarding flap, prevents food entry into trachea.
    • Vocal Cords: Made of elastic tissue, produce sound.
    • Voice Production: Air passage between vocal cords, modulated by tongue, teeth, lips, and nasal cavity.

4) Trachea (Windpipe):

  • Length: About 10-12 cm, width: 2.5 cm.
  • Location: In front of the esophagus, runs downwards in the thorax.
  • Structure: Fibrous muscular tissue with 'C' shaped cartilages.
  • Cartilage Rings: 16 to 20 for support.
  • Lining: Ciliated epithelium, mucous glands.
  • Function: Removes dust particles via mucous and ciliary action.
 5) Bronchi: Divide from trachea into two branches, enter lungs.
  • Bronchioles: Further divisions, lack cartilage rings.
  • End Structure: Bronchioles terminate in alveoli, making the lung spongy and elastic.
    Bronchi and Bronchioles:

6) Lungs:

  • Location: Principal respiratory organs in thoracic cavity.
  • Characteristics: Pinkish, soft, hollow, paired, elastic, and distensible.
  • Enclosure: Pleural sac with outer parietal and inner visceral membranes.
  • Pleural Fluid: Lubricates, prevents friction between membranes.
  • Vascularity: Rich blood capillaries.
  • Lobes: Left lung has two, right lung has three.
  • Structure: Each lobe contains bronchioles and alveolar sacs.

7) Alveoli:

  • Structure: Spherical, thin-walled sacs containing about 20 alveoli each.
  • Capillary Network: Covered by capillaries from pulmonary artery and vein.
  • Alveolar Size: Each alveolus is about 0.1 mm in diameter.
  • Wall Composition: Thin and elastic, made of simple, non-ciliated, squamous epithelium with collagen and elastin fibers.
  • Quantity: Approximately 700 million alveoli in each lung, maximizing surface area for gas exchange.
  • Lobule Composition: Includes alveolar ducts, alveolar sacs, and alveoli where gaseous exchange occurs.

8) Diaphragm:

  • Description: Muscular septum separating thoracic and abdominal cavities.
  • Shape: Dome-shaped, flattens upon contraction.
Mechanism of Respiration:

Process of Respiration: Includes breathing, external respiration, internal respiration, and cellular respiration.

Breathing:

  • Definition: Process of air movement into and out of the lungs.
  • Importance: Facilitates gaseous exchange, Integral part of respiration. 

Inspiration:

  • Active process.
  • Muscle Action: Contraction of ribs, intercostal muscles, sternum, and diaphragm.
  • Thoracic Cavity Expansion: Increases volume.
  • Pressure Change: Decreases lung pressure, allowing air intake.
Expiration:
  • Passive process.
  • Muscle Action: Relaxation of intercostal muscles and diaphragm.
  • Thoracic Cavity Reduction: Decreases volume.
  • Pressure Change: Increases lung pressure, forcing air out.
Respiratory Cycle:
  • Alternating inspiration and expiration.
  • Frequency: 16 to 20 cycles per minute in adults.
  • Control: Medulla oblongata in the brain regulates respiration.
External Respiration/Exchange of Gases at the Alveolar Level:

Process:

  • Exchange of gases between alveolar air and blood.
  • Occurs through thin squamous epithelial layer of alveoli and capillary wall.

Principle:

  • Gases diffuse from higher partial pressure to lower partial pressure.
  • Carbon dioxide (CO2) diffuses from capillaries to alveoli.
  • Oxygen (O2) diffuses from alveoli to capillaries.
Internal Respiration:

  • Transport of O2: Only 3% carried in dissolved state by plasma, 97% as oxyhaemoglobin from lungs to tissues.

Oxygen Dissociation Curve:

  • Sigmoid curve showing oxygen-haemoglobin dissociation.
  • Reflects relationship between oxyhaemoglobin saturation and oxygen tension.

Bohr Effect: Shift of oxyhaemoglobin dissociation curve due to CO2 partial pressure change in blood.


 Haldane Effect: Increase in hydrogen ions decreases blood pH, affecting CO2 transport.

Transport of CO2:

  • 7% as carbonic acid by plasma.
  • 70% as sodium bicarbonate and potassium.
  • 23% as carbaminohaemoglobin.

Hamburger’s Phenomenon/Chloride Shift: Movement of chloride ions to maintain RBC-plasma ionic balance.

Cellular Respiration: Food oxidized in cell, producing ATP for vital processes.

Carbon Monoxide Poisoning:

  • Haemoglobin has 250 times more affinity for CO than O2.
  • Forms stable carboxyhaemoglobin, hindering O2 transport.
  • Causes oxygen starvation, leading to asphyxiation or death.
  • Treatment: Administering oxygen-carbon dioxide mixture to dissociate CO.
  • Occurs in closed spaces with incomplete combustion sources.
Lung Volumes:
  • Tidal Volume (T.V.): Volume of air inspired/expired during normal breathing. 500 ml.
  • Inspiratory Reserve Volume (IRV): Extra volume of air inspired during forced breathing beyond T.V. 2000 to 3000 ml.
  • Expiratory Reserve Volume (ERV): Maximum volume of air expired during forced breathing post normal expiration. 1000 to 1100 ml.
  • Dead Space (DS): Air volume in respiratory tract not involved in gas exchange. 150 ml.
  • Residual Volume (RV): Air volume remaining in lungs and dead space after max expiration. 1100 to 1200 ml.

Lung Capacities:

  • Total Lung Capacity: Max air lungs can hold after forceful inspiration. 5200 to 5800 ml.
  • Vital Capacity (VC): Max air breathed out after max inspiration. Sum of TV, IRV, and ERV. 4100 to 4600 ml.
Regulation of Breathing:
  • Involuntary Control: Controlled by inspiratory and expiratory centers in medulla, pneumotaxic center in pons, and apneustic center in medulla.
  • Hering-Breuer Reflex: Regulates breathing rate and depth, prevents lung overinflation.
  • Voluntary Control: Cerebral cortex prevents entry of water or irritating gases.
 Modified Respiratory Movements:
  • Used for expressing emotions and clearing air passages.
  • Includes reflexes and voluntary actions like yawning.

Common Disorders of Respiratory System (Cause, Symptoms, Treatment):

  1. 1) Emphysema:

    • Cause: Cigarette smoking, air pollution.
    • Symptoms: Alveoli overinflation, rupture.
    • Treatment: Quit smoking, oxygen therapy.

  2. 2) Bronchitis:

    • Cause: Bacterial/viral infection, smoking, pollution.
    • Symptoms: Bronchi inflammation, cough with sputum.
    • Treatment: Quit smoking, antibiotics, decongestants.

  3. 3) Sinusitis:

    • Cause: Viral infection, common cold.
    • Symptoms: Sinus lining inflammation.
    • Treatment: Antibiotics, decongestants, vaporizer.

  4. 4) Laryngitis:

    • Cause: Viruses, bacteria.
    • Symptoms: Hoarseness, cough, larynx inflammation.
    • Treatment: Antibiotics, voice rest.

  5. 5) Pneumonia:

    • Cause: Bacteria, viruses, mycoplasma.
    • Symptoms: Alveolar fluid accumulation, chest pain.
    • Treatment: Antibiotics, cough medicines.

  6. 6) Asthma:

    • Cause: Allergy to substances like pollen, dust.
    • Symptoms: Bronchi narrowing, wheezing, difficulty breathing.
    • Treatment: Inhalants, avoid irritants.

  7. 7) Occupational Respiratory Disorders (Silicosis, Asbestosis):

    • Cause: Long-term exposure to silica/asbestos dust.
    • Symptoms: Irritation, fibrosis.
    • Treatment: Protective gear.

Treatment:

  • Antibiotics, inhalants, vaporizers, cough medicines.
  • Quit smoking, use preventive masks, avoid pollution.

Artificial Ventilation: Induced breathing when unable to breathe.

Ventilator: Supports breathing when normal breathing fails.

Transportation in Living Organisms:
  • All living organisms exchange materials with their surroundings and within their bodies.
  • Organisms take up oxygen and nutrients for metabolic activities.

Circulation in Animals:

  • Diffusion and active transport suitable for small organisms.
  • Intracellular transport via cyclosis seen in many organisms like Paramoecium, Amoeba, root hair cells, and white blood cells.
  • Extracellular transport involves circulating water or body fluid; examples include sponges, coelenterates, roundworms, and flatworms.

Blood Vascular System:

In higher animals, the blood vascular system comprises blood, heart, and blood vessels.
 
Two types:
  • Open circulation: Blood flows into body cavities; found in arthropods and mollusks.
  • Closed circulation: Blood circulates within vessels; found in vertebrates, higher mollusks, and annelids.

Types of Closed Circulation:

  • Single Circulation (in fishes): Blood passes through the heart once per cycle, from heart to gills for oxygenation, then to body parts before returning.

Double Circulation (in humans):
  • Blood follows two routes: pulmonary and systemic.
  • Pulmonary circulation: Heart to lungs and back; oxygenation occurs.
  • Systemic circulation: Heart to body organs (except lungs) and back.
  • Coronary circulation: Supplies oxygenated blood to cardiac muscles; coronary arteries supply, coronary veins collect.
Circulatory System in Humans:
  • Made up of blood vascular system and lymphatic system.
  • Blood vascular system includes blood, heart, and blood vessels.

Blood Composition and Coagulation:

  • Haematology: Study of blood.
  • Blood is a bright red, slightly alkaline fluid derived from mesoderm.
  • Blood Volume: Approximately 5 liters, around 8% of total body weight.

Composition of Blood:

  1. Plasma (55%):

    • Straw-colored fluid, 90-92% water, and 8-10% solutes.
    • Solutes include proteins (serum albumin, serum globulin, heparin, fibrinogen, prothrombin), nutrients, nitrogenous wastes (urea, uric acid, ammonia, creatinine), gases (oxygen, carbon dioxide, nitrogen), regulatory substances (enzymes, hormones), and inorganic substances (bicarbonates, chlorides, phosphates, sulphates of sodium, potassium, calcium, magnesium).

  2. Blood Corpuscles (45%):

    • Three types: erythrocytes (RBCs), leucocytes (WBCs), and thrombocytes (platelets).

     1) Red Blood Corpuscles / Erythrocytes:

  • Circular, biconcave, enucleated cells, approximately 7 μm in diameter and 2.5 μm in thickness.
  • RBC count: Male (5.1-5.8 million/cu mm), Female (4.3-5.2 million/cu mm).
  • Erythropoiesis: Formation of RBCs occurs in liver and spleen in fetuses, and in red bone marrow in adults.
  • Old RBCs are destroyed in liver and spleen.
  • Polycythemia: Increase, erythrocytopenia: Decrease in RBC count.
  • Contain haemoglobin for oxygen and carbon dioxide transport.
  • Haemoglobin Content: Male (14-17 gm/100 ml), Female (13-15 gm/100 ml).
  • Functions: Oxygen transport from lungs to tissues, carbon dioxide transport from tissues to lungs, maintaining blood pH, viscosity.
  • Contains carbonic anhydrase enzyme.
  • Haematocrit: Ratio of RBC volume to total blood volume.

2) White Blood Corpuscles / Leucocytes:

  • Colorless, nucleated, amoeboid, and phagocytic cells.
  • Show diapedesis (squeezing out of blood capillaries by amoeboid movement).
  • Size: Approximately 8 to 15 μm.
  • Total WBC count: 5000 to 11000 WBCs/cu mm of blood.
  • Leucopoiesis: Formation of WBCs occurs in red bone marrow, spleen, lymph nodes, tonsils, thymus, and Payer’s patches.
  • Leucocytosis: Increase, leucopenia: Decrease in WBC count.
  • Leukaemia: Pathological increase in WBC count.
  • Dead WBCs are destroyed by phagocytosis in blood, liver, and lymph nodes.
  • Two types: granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (monocytes, lymphocytes).

 Characteristics of Different Types of Leucocytes:

Granulocytes:

  • Cells with granular cytoplasm and lobed nucleus.
  • Three types: neutrophils, eosinophils, and basophils.

(I) Neutrophils:

  • Cytoplasmic granules take up neutral stains.
  • Nucleus: Three to five lobed.
  • Also known as polymorphonuclear leucocytes or polymorphs.
  • Approximately 70% of total WBCs.
  • Phagocytic; engulf microorganisms.

(II) Eosinophils or Acidophils:

  • Cytoplasmic granules take up acidic dyes (e.g., eosin).
  • Nucleus: Bilobed.
  • Approximately 3% of total WBCs.
  • Non-phagocytic.
  • Increased during allergic conditions; possess antihistamine properties.

(III) Basophils:

  • Cytoplasmic granules take up basic stains (e.g., methylene blue).
  • Nucleus: Twisted.
  • Smallest, approximately 0.5% of total WBCs.
  • Non-phagocytic.
  • Release heparin (anticoagulant) and histamine (inflammatory and allergic reactions).

Agranulocytes:

  • Do not show cytoplasmic granules; nucleus is not lobed.
  • Two types: lymphocytes and monocytes.

(I) Lymphocytes:

  • Agranulocytes with a large round nucleus.
  • Approximately 30% of total WBCs.
  • Responsible for immune response; produce antibodies.

(II) Monocytes:

  • Largest WBCs; large kidney-shaped nucleus.
  • Approximately 5% of total WBCs.
  • Phagocytic; can differentiate into macrophages.
  • Active at sites of infections.

  1.  Thrombocytes / Platelets:
  • Non-nucleated, round, and biconvex blood corpuscles.
  • Smallest corpuscles, measuring about 2.5 to 5 µm in diameter, with a count of about 2.5 lakhs/cu mm of blood.
  • Life span: Approximately 5 to 10 days.
  • Formed from megakaryocytes of bone marrow, breaking from these cells as fragments during thrombopoiesis.
  • Thrombocytosis: Increase in platelet count; thrombocytopenia: Decrease in platelet count.
  • Possess thromboplastin aiding in blood clotting.
  • Aggregate at the site of injury to form a platelet plug, releasing thromboplastin, initiating further blood clotting reactions.

Blood Clotting / Coagulation of Blood:

  • Active anticoagulants like heparin and antithrombin are present in intact blood vessels.
  • Upon rupture of a blood vessel, bleeding starts; fluid blood is converted into a semi-solid jelly by blood coagulation or clotting.
  • Clotting Factors: Many factors (12 clotting factors) present in plasma and tissues are involved.


Events during Blood Clotting:

  1. Release of thromboplastin from extrinsic source in tissue and intrinsic source in plasma at the injured site through a step-wise (cascade process).
  2. Formation of enzyme prothrombinase in the blood.
  3. Conversion of prothrombin into thrombin by prothrombinase.
  4. Conversion of fibrinogen into fibrin by thrombin.
  5. Formation of mesh by the fibrin fibers, forming the clot.
  6. Normal clotting time: 2 to 8 minutes.
Heart:
  • Hollow, muscular, conical organ about the size of one’s fist.
  • Broad base and narrow apex tilted towards the left.
  • Mesodermal in origin.
  • Situated in the middle of the thoracic cavity in a space called mediastinum, between the two lungs.
  • Length: 12 cm, Breadth: 9 cm, Weight: 250 to 300 grams.

Pericardium:

Double-layered membrane.

  • Fibrous Pericardium: Outer, tough layer of inelastic fibrous connective tissue.
  • Serous Pericardium:
    • Inner pericardium with two layers: outer parietal layer and inner visceral layer.
    • Parietal layer lines the fibrous pericardium.
    • Visceral layer (epicardium) lies next to the heart on the outer side.
    • Pericardial fluid present between parietal and visceral layers.

Heart Wall:

Consists of three layers:

  • Epicardium:Outer layer with a single layer of flat epithelial cells called mesothelium.  
  • Myocardium: Middle layer with cardiac muscle fibers responsible for heart movements.
  • Endocardium: Inner layer with a single layer of flat epithelial cells called endothelium. 

  1. External Structure of Heart:

     
  2. Atria (Auricles):

    • Two superior, small, thin-walled receiving chambers.
    • Receive blood from the body (right atrium) and lungs (left atrium).
  4. Ventricles:
    • Two inferior, large, thick-walled, distributing chambers.
    • Pump blood to the lungs (right ventricle) and the body (left ventricle).
  5. Atrioventricular Groove (Coronary Sulcus): Transverse groove between the atria and ventricles.
  6. Interventricular Sulcus: Groove between the right and left ventricles.
  7. Coronary Arteries and Veins: Present in the sulci, Coronary veins join to form the coronary sinus, which opens into the right atrium.
  8. Blood Flow:
    • Right atrium receives deoxygenated blood from the body through the superior and inferior vena cava.
    • Left atrium receives oxygenated blood from the lungs through pulmonary veins.
    • Deoxygenated blood from the right ventricle is sent to the lungs through the pulmonary trunk.
    • Oxygenated blood from the left ventricle is sent to the entire body through the systemic aorta.
  9. Ligamentum Arteriosum: Connects the pulmonary trunk and systemic aorta, representing the ductus arteriosus of the fetus.

Internal Structure of Heart:

Chambers:

  • Four chambers: two atria and two ventricles.
  • Atria are thin-walled upper receiving chambers separated by the interatrial septum.
Right Atrium:
  • Receives deoxygenated blood from the body and heart.
  • Opening of inferior vena cava guarded by Eustachian valve; opening of coronary sinus guarded by Thebesian valve.
  • Fossa ovalis: remnant of foramen ovale in the fetal heart.
Left Atrium: Receives oxygenated blood from the lungs through pulmonary veins.
Atrioventricular Apertures: Openings connecting atria and ventricles, guarded by tricuspid (right) and bicuspid/mitral (left) valves.
Valves:
  • Prevent backflow into atria during ventricular contraction.
  • Tricuspid valve (right) has three flaps; bicuspid/mitral valve (left) has two flaps.
Ventricles:
  • Two thick-walled lower distributing chambers separated by the interventricular septum.
  • Left ventricle has a thicker wall.
  • Columnae carneae/trabeculae carneae: irregular muscular ridges on the inner surface.
Arteries:
  • Pulmonary trunk (right ventricle) carries deoxygenated blood to the lungs.
  • Systemic aorta (left ventricle) carries oxygenated blood to the body.
Semilunar Valves: Three valves at the base of pulmonary trunk and systemic aorta prevent backward flow of blood during ventricular diastole.
  1. Pumping Action of the Heart:

  2. Function:

    • The heart pumps blood through rhythmic contraction and relaxation of cardiac muscles.
    • Contraction is called systole, and relaxation is diastole.

  3. Heart Rate: Beats about 72 times per minute, pumping out approximately 5 liters of blood, known as cardiac output.

Conducting System of the Heart:

Components:

  • Sinoatrial node (S.A. node)
  • Atrioventricular node (AVN)
  • Bundle of His
  • Purkinje fibers

Auto-Rhythmicity:

  • Heartbeat originates from the sinoatrial node, making the heart myogenic.
  • Impulse travels through the conducting system, setting the heart's rhythm.

Impulse Pathway:

  • Sinoatrial node (Pacemaker) → Internodal pathway → Atrioventricular node → Bundle of His → Right and left bundle branches → Purkinje fibers.
Working Mechanism of the Human Heart:

Cardiac Cycle:

  • Alternating contraction (systole) and relaxation (diastole).
  • One cardiac cycle = one heartbeat.
  • Includes atrial systole, ventricular systole, and joint diastole.

Atrial Systole:

  • Atria contract, pushing blood into ventricles.
  • Lasts 0.1 second, followed by atrial diastole.

Ventricular Systole:

  • Ventricles contract, pumping blood to the lungs and body.
  • Prevents backflow with closed atrioventricular valves (lubb sound).
  • Lasts 0.3 second, followed by ventricular diastole.

Joint Diastole:

  • Atria and ventricles relax.
  • Prevents backflow from pulmonary trunk and aorta with closed semilunar valves (dub sound).
  • Lasts 0.4 second.

Regulation of Cardiac Activity:

Control Mechanisms: 

 
  • Cardiovascular center in the medulla oblongata regulates heart function.
  • Sympathetic nerves release adrenaline, increasing heart rate.
  • Parasympathetic nerves release acetylcholine, decreasing heart rate.
  • Hormones like epinephrine and norepinephrine affect heart rate.
  • Electrolyte concentrations (K+, Ca++, Na+) influence cardiac activity, with elevated K+ and Na+ levels decreasing it.

Blood Vessels: Blood vessels include arteries, veins, and capillaries. 

  • Arteries: Carry blood away from the heart, Arteries branch into arterioles, which further divide into capillaries.
  • Veins: Carry blood towards the heart, Have a wide lumen and low blood pressure.

Histological Structure of Artery and Vein:

  • Arteries are thick-walled vessels carrying oxygenated blood, except the pulmonary artery.
  • Consist of three layers: tunica externa, tunica media, and tunica interna.
    • Tunica externa: Outermost layer of connective tissue with elastic and collagen fibers.
    • Tunica media: Middle layer of smooth muscle and elastic fibers, resisting high blood pressure.
    • Tunica interna: Innermost layer of endothelium and elastic layer.

Capillaries:

  • Thinnest blood vessels formed by arteriole division.
  • Unite to form venules, which then join to form veins.

Histology of Capillaries:

  • Smallest blood vessels made of endothelium.
  • Capillary walls are permeable, allowing exchange of gases, nutrients, and waste products.

Heartbeat, Pulse, and Cardiac Output:

  • Heartbeat: Rhythmic contraction and relaxation of the heart.
  • Heart rate: Number of beats per minute (72 times per minute).
  • Stroke volume: Amount of blood pumped from the ventricles each time (about 70 ml).
  • Cardiac output: Volume of blood pumped from the ventricles per minute (around 5 liters).
  • Tachycardia: Abnormally fast heart rate (over 100 beats per minute).
  • Bradycardia: Abnormally slow heart rate (under 60 beats per minute).
  • Pulse: Pressure wave traveling through arteries after each ventricular systole.
Blood Pressure (B.P.):

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

Arterial Blood Pressure:
  • Pressure exerted on the arterial wall.
  • Described as systolic blood pressure (during ventricular contraction) and diastolic blood pressure (during ventricular relaxation).
  • Normal values: Systolic - around 120 mmHg, Diastolic - around 80 mmHg.
  • Written as a ratio, e.g., 120/80 mmHg.
  • Pulse pressure is the difference between systolic and diastolic pressure, usually around 40 mmHg.

Measurement of Blood Pressure:

  • Done using a sphygmomanometer.
  • Inflatable cuff placed around the upper arm.
  • Cuff inflated to block the brachial artery, then slowly deflated.
  • Korotkoff sounds indicate systolic and diastolic pressure.

Factors Affecting Blood Pressure:

  • Cardiac Output: Higher cardiac output increases systolic pressure.
  • Peripheral Resistance: Diameter of blood vessels affects resistance. Vasoconstriction increases resistance and blood pressure.
  • Blood Volume: Loss of blood decreases blood pressure.
  • Blood Viscosity: Directly proportional to blood pressure.
  • Age: Increases with age due to vessel inelasticity.
  • Venous Return: Directly proportional to blood pressure.
  • Length and Diameter of Blood Vessels: Longer vessels have higher pressure. Vasodilation decreases pressure.
  • Gender: Females generally have slightly lower BP before menopause.

Hypertension:

  • Blood pressure exceeding 140/90 mmHg.
  • Can lead to organ damage due to ruptured blood vessels.
  • Contributes to conditions like angina pectoris and myocardial infarction.
  • Caused by factors like arteriosclerosis, obesity, stress, smoking, and hormonal imbalances.
  1. Coronary Artery Disease (CAD):
  • Definition: Narrowing of coronary arteries due to atherosclerosis, leading to inadequate blood supply and damage to heart muscles.
  • Symptoms: Range from mild chest pain (angina pectoris) to heart attack (myocardial infarction) depending on the degree of obstruction.
  1. Atherosclerosis: Deposition of fatty substances in artery linings, forming plaques and reducing arterial lumen size.
  2. Angina Pectoris: Chest pain due to reduced blood supply to the heart muscle caused by narrowed coronary arteries.
  3. Angiography: X-ray imaging of cardiac blood vessels to locate blockages. Procedures like angioplasty or bypass surgery are performed based on the degree of blockage.
  4. Heart Transplant: Replacement of a severely damaged heart with a healthy one from a brain-dead or recently deceased donor. Done in cases of end-stage heart failure and severe coronary arterial disease.
  5. Silent Heart Attack: Heart attack lacking typical symptoms like extreme chest pain, hypertension, shortness of breath, sweating, and dizziness. More common in men than women.
  1. Electrocardiogram (ECG):
Definition: A graphic record of electrical variations produced by the heart during one cardiac cycle.
  • Instrument: ECG machine, used to record action potentials generated by heart muscles.
  • Discovery: Einthoven in 1903, known as the "Father of Electrocardiography."

Components of a Normal ECG:

 1) P-wave:

    • Definition: Small upwards wave representing impulse generated by the SA node.
    • Cause: Atrial depolarization leading to atrial contraction.

  2. 2) QRS-complex Wave:

    • Description: Begins as a downward deflection, continues as a large upright triangular wave, and ends as a downward wave.
    • Cause: Spreading of impulse from SA node to AV node, then to bundle of His and Purkinje fibers, resulting in ventricular depolarization and contraction.

  3. 3) T-wave:

    • Description: Broad upward wave representing ventricular repolarization and relaxation.

Functions of ECG:

  • Diagnosis and Prognosis: Detects abnormal heart functioning such as coronary artery diseases, heart block, angina pectoris, tachycardia, ischemic heart disease, myocardial infarction, and cardiac arrest.
Lymphatic System:

  • Composition: Includes lymph, lymphatic capillaries, lymphatic vessels, and lymph nodes.
  • Lymph: Tissue fluid bathing the cells, collected in lymphatic capillaries; devoid of RBCs, platelets, and some plasma proteins; contains carbon dioxide and metabolic wastes.
  • Lymphatic Capillaries: Thin-walled vessels interwoven with blood capillaries, present in tissue spaces; blind-ended; wider than blood capillaries; lined by thin, flat endothelial cells.
  • Lymphatic Vessels: Formed by union of lymphatic capillaries; thin-walled with numerous valves to prevent backflow; main vessels are thoracic or left lymphatic duct and right lymphatic duct.

Functions:

  • Draining Excess Fluid: Removes excess tissue fluid from extracellular spaces back into the blood.
  • Transport: Carries carbon dioxide, metabolic wastes, lymphocytes, and antibodies from lymph nodes to blood; transports absorbed fats from intestine to blood.
  • Defense: Destroys invading microorganisms and foreign particles in lymph nodes.

Tonsils:

  • Small lymphatic nodules in pharyngeal region; strategically positioned to fight inhaled and ingested foreign substances.
  • Tonsillitis: Inflammation of tonsils due to viral or bacterial infection; symptoms include sore throat, fever, swollen lymph nodes, etc.
  • Treatment: Viral tonsillitis resolves naturally, bacterial tonsillitis requires antibiotics; tonsillectomy may be performed if necessary.

Comparison between Blood and Lymph: