Study Notes on Transport in Humans

Chapter 9: Transport in Humans

Overview of Transport in Simple and Complex Organisms

  • Unicellular Organisms (e.g., Amoeba)
    • Substances enter and exit the cell via diffusion at the cell membrane.
  • Multicellular Organisms
    • Inquiry into how nutrition and essential substances are acquired by body cells, such as oxygen for respiration.

9.1 The Human Transport System

  • Purpose of Transport Systems
    • To ensure the supply of useful substances to cells and the removal of waste products.
  • Main Components
    • Circulatory System and Lymphatic System.

Functions of the Circulatory System

  • Blood
    • Role: Carries useful substances and waste to and from body cells.
  • Heart
    • Function: Acts as a pump to drive blood throughout the body.
  • Blood Vessels
    • Function: Allow exchange of materials between blood and body cells; distribute blood across the body.

9.2 What is Blood?

  • Composition of Blood
    • Blood is a tissue composed of blood cells suspended in plasma.
    • Separation: Blood can be separated using a centrifuge.
    • Blood Cell Types:
    • Red Blood Cells
    • White Blood Cells
    • Blood Platelets
    • Plasma Composition:
    • Light yellow in color.
    • Composes approximately 55% of human blood.
      • Constituents:
      • 90% water
      • 10% dissolved substances (including hormones, plasma proteins, nutrients, and metabolic wastes such as urea and CO₂).
    • Functions of Plasma:
    • Transports dissolved substances and distributes heat.

Types of Blood Cells

  • Red Blood Cells (RBCs)

    • Shape: Biconcave disc.
    • Color: Red due to the pigment hemoglobin.
    • Maturity: No nucleus when mature.
    • Production: Produced in bone marrow (including limb bones, ribs, vertebrae, etc.).
    • Destruction: Occurs in the liver or spleen; hemoglobin is broken down into iron and bile pigment.
    • Function: Carries oxygen; lifespan is about 120 days.

  • White Blood Cells (WBCs)

    • Shape: Irregular.
    • Color: Colorless.
    • Nucleus: Large round or lobed nucleus in phagocytes.
    • Production: Originates from bone marrow and spleen, matures in lymph nodes.
    • Function: Defends the body against pathogens and diseases; lifespan varies (approximately 13 to 20 days, with some types living for years).

  • Blood Platelets

    • Shape: Irregular.
    • Color: Colorless, no nucleus.
    • Production: Formed in bone marrow; destruction occurs in liver or spleen.
    • Function: Involved in blood clotting; lifespan is around 7-10 days.

9.3 Enrichment – Blood Clotting

  • Process of Blood Clotting:
    • When a blood vessel is damaged, blood platelets are attracted to the wound and initiate a series of reactions that convert fibrinogen into a net of fibrin.
    • Blood cells (platelets, red blood cells, and white blood cells) become trapped in the fibrin net, forming a blood clot to seal the wound, preventing pathogen entry and stopping bleeding.

Functions of Blood

  • Transport of Substances:
    • Oxygen Transport: Through oxyhaemoglobin (O₂ binds to hemoglobin in RBCs). Distributes oxygen throughout the body.
    • Carbon Dioxide Transport: CO₂ produced in cellular respiration is primarily transported to the lungs as hydrogencarbonate ions (HCO₃⁻).
    • Nutrient Distribution: Nutrients absorbed in the small intestine (e.g., glucose, amino acids) travel in plasma to the liver first, then throughout the body.
    • Urea Transport: Urea is transported in blood to the kidneys for excretion in urine.
    • Hormone Transport: Hormones are carried in blood to target organs.
    • Antibody Distribution: Antibodies produced by some white blood cells (e.g., B-Cells) are transported in blood to provide immune response.

Enrichment: Endocrine vs Exocrine Secretion

  • Endocrine Glands: Release their secretions (hormones) into the blood.
  • Exocrine Glands: Release their secretions outside the blood (e.g., gastric juice is an exocrine secretion).

9.5 Functions of Blood in Body Defense

  • Blood Platelets: Play a critical role in blood clotting, preventing excessive blood loss and blocking pathogen entry.
  • Phagocytes: Engulf and digest pathogens via phagocytosis.
  • Lymphocytes: Produce antibodies to kill pathogens or neutralize toxins.

Extra: Other Immune Cells

  • Macrophages: Specialized cells in the spleen that detect, phagocytose, and destroy harmful organisms; present antigens to T cells.
  • Eosinophils: Typically found in the stomach, play a role in combating parasites.
  • Killer T Cells: Bind to infected cells and kill them by perforating cell membranes.
  • Natural Killer Cells: Identify and destroy infected cells and cancer cells.

Blood Group Classification

  • Types of Blood Groups: A, B, AB, O.

    • Determined by antigens on the surfaces of red blood cells:
    • Blood Type A: Contains antigen A.
    • Blood Type B: Contains antigen B.
    • Blood Type AB: Contains antigens A and B.
    • Blood Type O: Contains no antigens.

  • Antibodies in Plasma:

    • Types of antibodies include Anti-A and Anti-B.
    • Reaction details of antibodies with their specific antigens, e.g., Anti-A antibodies attack Antigen A.

Compatibility in Blood Transfusion

  • Need for Compatibility: Donor's blood must be compatible with the recipient’s blood to prevent agglutination (clumping of red blood cells) which can lead to clots that block blood vessels.
  • Universal Recipients and Donors:
    • Blood Type AB: Universal recipient (can take all blood types).
    • Blood Type O: Universal donor (can donate to all types).

9.3 - Blood Vessels

  • Types of Blood Vessels: Arteries, Veins, Capillaries.
  • Arteries: Carry oxygenated blood away from the heart (except pulmonary artery). Thick walls to withstand high blood pressure, contain muscular and elastic fibers, and have no valves.
  • Veins: Carry deoxygenated blood towards the heart (except pulmonary veins). Larger lumen, thinner walls compared to arteries, and contain valves to prevent backflow.
  • Capillaries: Site for material exchange between blood and tissues; one cell thick, highly branched providing a large surface area.

Blood Pressure Dynamics

  • Blood Pressure Change: Varies across blood vessels - higher in arteries, lower in veins.
  • Systolic and Diastolic Pressure: Definitions and relevance in measuring blood pressure.

9.4 The Heart

  • Heart Structure: Located between the lungs and protected by the rib cage, composed mainly of cardiac muscle, and surrounded by pericardium.
  • Coronary Arteries and Veins: Supply oxygen to cardiac muscles and remove carbon dioxide and waste.
  • Chambers of the Heart: Divided into atria (upper chambers) and ventricles (lower chambers), separated by septum to prevent mixing of blood types.
Septum and Heart Valves
  • Septum: Separates left and right sides of the heart.
  • Heart Valves: Prevent backflow of blood - bicuspid and tricuspid valves in the atria, semilunar valves in the aorta and pulmonary artery.
Adaptive Features of Heart Functioning
  • Continuous contraction without fatigue, thick muscular walls in ventricles, presence of valves to ensure unidirectional blood flow.

9.5 Blood Circulation

  • Circulation Overview: Blood circulates through the body in a double loop (pulmonary and systemic circulation).
  • Pulmonary Circulation: Deoxygenated blood flows from the right atrium to the right ventricle, then to the lungs for oxygenation, before returning as oxygenated blood to the left atrium.
  • Systemic Circulation: Oxygenated blood flows from the left atrium to the left ventricle, then out to the body via the aorta, returning deoxygenated blood to the right atrium.
Hepatic Portal Vein
  • Unique feature where the liver receives blood from both the hepatic artery and hepatic portal vein connecting food absorption from the intestines to liver metabolism.

Importance of Double Circulation

  • Ensures efficient supply of oxygenated blood to tissues despite pressure drops in the pulmonary system.

9.6 Exchange of Materials between Blood and Cells

  • Tissue Fluid: Medium for exchange of materials; pressure allows components of plasma to leave the capillaries while red blood cells and plasma proteins remain.
  • Material Exchange: Nutrients and oxygen diffuse from the tissue fluid into body cells; waste products diffuse into the tissue fluid from cells.

9.7 Lymphatic System

  • Components of the Lymphatic System: Comprises lymph, lymph vessels, lymph nodes.
  • Functionality: Returns excess tissue fluid, transports lipids from intestines, and filters out pathogens to protect against diseases.