Comprehensive Study Guide for Transport in Humans and Animals

Transport in Unicellular vs. Multicellular Organisms

  • Unicellular Organisms Characteristics:

    • Small body mass resulting in a larger Total Surface Area over Volume ratio (TSA/V).

    • Short distance between the external environment and the cell.

    • Substance exchange occurs via simple diffusion; oxygen diffuses into the cell and carbon dioxide diffuses out down the concentration gradient.

    • Specialised transport systems are not required.

    • Principle: The smaller the mass of an organism, the higher the TSA/V ratio and the higher the rate of diffusion.

  • Multicellular Organisms Characteristics:

    • Large body mass and a lower Total Surface Area over Volume ratio (TSA/V).

    • Large distance between the external environment and internal cells.

    • Substance exchange cannot occur by simple diffusion alone.

    • Requires a specialised transport system (blood circulatory system) and a respiratory system.

    • Transports gases (O2O_2 and CO2CO_2), nutrients (amino acids, glucose, lipids), waste substances (urea), antibodies, and hormones.

    • Principle: The larger the mass of an organism, the smaller the TSA/V ratio and the lower the rate of diffusion.

  • Numerical Comparison of TSA/V Ratios (based on cube size):

    • 1 cm1\,cm cube: Total Surface Area = (1×6)=6 cm2(1 \times 6) = 6\,cm^2; Volume = 1×1×1=1 cm31 \times 1 \times 1 = 1\,cm^3; TSA/V ratio = 6:16:1.

    • 2 cm2\,cm cube: Total Surface Area = (4×6)=24 cm2(4 \times 6) = 24\,cm^2; Volume = 2×2×2=8 cm32 \times 2 \times 2 = 8\,cm^3; TSA/V ratio = 3:13:1.

    • 4 cm4\,cm cube: Total Surface Area = (16×6)=96 cm2(16 \times 6) = 96\,cm^2; Volume = 4×4×4=64 cm34 \times 4 \times 4 = 64\,cm^3; TSA/V ratio = 1.5:11.5:1.

Types of Circulatory Systems

  • Open Circulatory System:

    • Medium: Haemolymph flows directly into the body cavity (haemocoel) and bathes the cells.

    • Haemolymph: A blood-like nutritious liquid found in invertebrates like insects and molluscs.

    • Does not contain haemoglobin and does not transport respiratory gases.

    • Flow pattern: Heart contraction pumps haemolymph into the haemocoel; substance exchange occurs via simple diffusion between haemolymph and cells. When the heart relaxes, haemolymph flows back through openings called ostia.

  • Closed Circulatory System:

    • Medium: Blood is always contained within a continuous closed blood vessel and distributed to the whole body.

    • Substance exchange occurs across the walls of blood capillaries.

  • Single Circulatory System:

    • Blood flows through blood vessels and through the heart in one direction (single pathway).

    • Example: Fish. The heart has two chambers (1 atrium, 1 ventricle).

  • Double Circulatory System:

    • Blood flows through blood vessels and through the heart twice in one complete cycle (double pathway).

    • Incomplete Double Circulatory System: Deoxygenated and oxygenated blood mix. Example: Amphibians (3 chambers: 2 atria, 1 ventricle).

    • Complete Double Circulatory System: Deoxygenated and oxygenated blood do not mix. Examples: Mammals and birds (4 chambers: 2 atria, 2 ventricles).

Comparison of Blood Circulatory Systems in Insects, Fish, Amphibians, and Humans

  • Similarities: Found in all multicellular organisms; consists of a heart to pump blood/haemolymph; functions to transport nutrients and waste; heart has valves to ensure one-way flow.

  • Differences:

    • Insects: Open system; Single; Oxygenated/deoxygenated blood separation not applicable; No lungs; No septum; 1 chamber; Low blood pressure; Low flow rate.

    • Fish: Closed system; Single; No mixing (single loop); Gills present; No septum; 2 chambers; Low blood pressure; Low flow rate.

    • Amphibians: Closed system; Double incomplete; Mixing occurs in ventricle; Lungs and skin (pulmocutaneous) present; No septum; 3 chambers; Moderate blood pressure; Moderate flow rate.

    • Humans: Closed system; Double complete; Proper separation of oxygenated/deoxygenated blood; Lungs present; Septum present; 4 chambers; High blood pressure; High flow rate.

Blood Components and Functions

  • Blood Composition:

    • Blood Plasma (55%55\%): Consists of Water (90%90\%) as a solvent/transport medium, and dissolved substances.

      • Plasma Proteins: Fibrinogen (blood clotting), Albumin (osmotic pressure control), Globulin (antibodies/defense).

      • Solutes: Nutrients (energy/growth), Waste (toxic substances for disposal), Gases (O2O_2 for respiration), Hormones and Enzymes.

    • White Blood Cells & Platelets (<1%<1\%): Leucocytes and clotting fragments.

    • Red Blood Cells (44%44\%): Erythrocytes.

  • Erythrocytes (Red Blood Cells):

    • Produced in bone marrow (sternum, ribs); life span of approximately 120 days120\,days; destroyed in the liver/spleen via phagocytosis.

    • Biconcave disc shape increases TSA/V for efficient gas exchange.

    • No nucleus in mature stage to allow more space for haemoglobin.

    • Elastic plasma membrane allows squeezing through capillaries.

    • Contains haemoglobin (red pigment) with an iron atom (hemeheme group) as a binding site for oxygen.

    • Forms oxyhaemoglobin in high oxygen partial pressure regions and releases oxygen in low partial pressure tissues.

  • Platelets:

    • Produced from cell cytoplasm fragments in bone marrow; life span less than one week; essential for blood clotting.

  • Leucocytes (White Blood Cells):

    • Contains a nucleus and no haemoglobin; life span less than 5 days5\,days. Can diffuse out of capillaries to fight pathogens.

    • Granulocytes (with granules):

      • Basophil: S-shaped nucleus; contains heparin to prevent clotting.

      • Eosinophil: Two-lobed nucleus; releases enzymes for inflammation and allergic reactions.

      • Neutrophil: 2 to 5 lobes; ingests bacterial and dead cells via phagocytosis.

    • Agranulocytes (without granules):

      • Lymphocyte: Large nucleus with little cytoplasm; produces antibodies to destroy bacteria/viruses and antitoxins.

      • Monocyte: Largest leucocyte; spherical nucleus; ingests bacteria and dead cells via phagocytosis.

Blood Vessel Morphology and Function

  • Artery:

    • Wall: Thick, muscular, and elastic to withstand high blood pressure from cardiac contraction.

    • Lumen: Small.

    • Valves: None (except semilunar valves at the base of aorta and pulmonary artery).

    • Function: Transports oxygenated blood (except pulmonary artery) from the heart to the body.

  • Vein:

    • Wall: Thin, less muscular, less elastic.

    • Lumen: Large.

    • Valves: Present to maintain one-way flow under very low pressure.

    • Function: Transports deoxygenated blood (except pulmonary vein) from body cells to the heart.

  • Capillary:

    • Wall: One-cell thick, not muscular/elastic.

    • Lumen: Smallest.

    • Valves: No valves.

    • Pressure: Low.

    • Function: Site of substance exchange between blood and body cells; connects arteries to veins.

Human Heart Anatomy and Physiology

  • Chambers and Valves:

    • Right Atrium: Receives deoxygenated blood via superior and inferior vena cava.

    • Right Ventricle: Pumps deoxygenated blood to lungs via pulmonary artery; has the Tricuspid valve (3 leaflets) to prevent backflow.

    • Left Atrium: Receives oxygenated blood via pulmonary veins.

    • Left Ventricle: Pumps oxygenated blood to the body via the aorta; has the Bicuspid valve (2 leaflets/mitral) and very thick muscular walls to generate high pressure.

    • Semilunar Valves: Located at the base of the aorta and pulmonary artery to prevent backflow into ventricles during diastole.

    • Septum: Separates left and right sides to prevent mixing of oxygenated and deoxygenated blood.

  • Coronary System:

    • Coronary Artery: Supplies oxygenated blood and nutrients to cardiac muscle cells.

    • Coronary Vein: Removes deoxygenated blood and waste from cardiac muscle cells.

  • Specific Muscle Characteristics:

    • Cardiac muscles are myogenic; they contract and relax uniformly without external nervous impulses.

    • Muscles intersect and are connected to allow rapid spreading of electrical impulses.

Mechanism of Heart Contraction and the 'Lub-Dub' Sound

  • Contraction Pathway:

    1. Sinoatrial (SA) Node (Pacemaker): Generates electrical impulses transmitted to the walls of both atria simultaneously, causing them to contract (atrial systole).

    2. Atrioventricular (AV) Node: Receives impulses from the SA node and generates its own nerve impulse.

    3. Bundle of His and Purkinje Fibres: Spread the impulse to the ventricle walls, causing simultaneous ventricular contraction (ventricular systole).

    4. Blood is pumped out of the heart (CO2CO_2 to lungs, O2O_2 to body).

  • Heart Sounds:

    • 'Lub': First sound caused by the closure of tricuspid and bicuspid valves.

    • 'Dub': Second sound caused by the closure of semilunar valves.

  • Artificial Pacemaker: Used if the SA node is impaired; it produces small electrical impulses to stimulate consistent heart contraction.

Blood Clotting Mechanism and Health Issues

  • Mechanism Procedure:

    1. Damaged cells and platelets release Thrombokinase.

    2. Thrombokinase, with the aid of Calcium ions and Vitamin K, converts the inactive plasma protein Prothrombin into active Thrombin.

    3. Thrombin acts as an enzyme to catalyse the conversion of soluble Fibrinogen into insoluble thread-like Fibrin.

    4. Fibrin creates a network to trap erythrocytes, forming a clot to close the wound.

  • Importance: Minimises blood loss, prevents microorganism entry, maintains blood pressure.

  • Health Issues:

    • Thrombosis: Formation of a blood clot (thrombus) due to slow blood flow or vessel damage.

    • Embolism: A thrombus that breaks loose and travels is an embolus; can cause myocardial infarction or stroke if stuck.

    • Haemophilia: Hereditary illness lacking clotting factors, leading to excessive bleeding.

Human Blood Groups and the Rhesus Factor

  • ABO System: Controlled by alleles IAI^A, IBI^B, and IOI^O.

    • Group A: Antigen A; Anti-B antibody. Can donate to A, AB; receive from A, O.

    • Group B: Antigen B; Anti-A antibody. Can donate to B, AB; receive from B, O.

    • Group AB: Antigens A and B; No antibodies. Universal acceptor.

    • Group O: No antigens; Anti-A and Anti-B antibodies. Universal donor.

    • Agglutination: Occurs if incompatible blood is mixed (e.g., Antigen B reacting with Anti-B antibody).

  • Rhesus (Rh) Factor: Antigen D.

    • Rh-positive (Rh+Rh^+): Antigen D present.

    • Rh-negative (Rh−Rh^-): Antigen D absent. Anti-D antibodies are only formed after exposure to Rh-positive blood.

  • Pregnancy and Rh Factor (Erythroblastosis Fetalis):

    • Problem arises if an Rh−Rh^- mother conceives an Rh+Rh^+ fetus.

    • During the first pregnancy, foetal Rh antigens may cross the placenta, causing the mother to produce anti-D antibodies. The first child is usually safe.

    • In a second Rh+Rh^+ pregnancy, accumulated anti-D antibodies cross the placenta and destroy foetal red blood cells.

    • Can lead to anaemia, mental retardation, or death. Treatment: Globulin injections after the first pregnancy.

Health Issues of the Human Circulatory System

  • Atherosclerosis: Formation of plaque (cholesterol, lipid, dead tissue, platelets) on artery walls, narrowing the lumen.

  • Arteriosclerosis: Plaque becomes hardened with calcium, causing loss of elasticity and high blood pressure.

  • Angina: Severe chest pain due to insufficient oxygen supply to cardiac muscles through narrowed coronary arteries.

  • Myocardial Infarction (Heart Attack): Occurs when the coronary artery is completely clogged and cardiac muscles die.

  • Stroke: Caused by hypertension leading to burst brain vessels or a thrombus blocking flow to brain tissues.

  • Treatments:

    • Angioplasty/Stenting: Inserting a balloon and stent to widen the lumen.

    • Coronary Artery Bypass Graft (CABG): Using a healthy vessel (e.g., from the leg) to bypass the blockage.

  • Healthy Lifestyle: No smoking, ideal body weight, balanced diet (low fat/salt), regular exercise, no alcohol.

The Human Lymphatic System: Formation and Function

  • Formation of Interstitial Fluid:

    • High hydrostatic pressure at the arterial end of capillaries forces plasma out into intercellular spaces, forming tissue fluid.

    • Tissue fluid lacks erythrocytes, platelets, and large plasma proteins.

    • 85%85\% of tissue fluid is reabsorbed at the venule end (hypertonic condition).

    • The remaining 15%15\% diffuses into lymphatic capillaries to form lymph.

  • Lymphatic Circulation:

    • Lymphatic vessels have nodes and valves.

    • Right lymphatic duct: Receives lymph from the right hand, chest, and right side of head/neck; drains into the right subclavian vein.

    • Thoracic duct: Receives lymph from the left side of head/neck/chest and all parts below the ribs; drains into the left subclavian vein.

  • System Components:

    • Tonsils: Traps/destroys pathogens from mouth/nose.

    • Thymus: Synthesises T lymphocytes.

    • Spleen: Synthesises lymphocytes, destroys old RBCs, stores RBCs.

    • Bone Marrow: Synthesises WBCs (lymphocytes).

    • Appendix: Stores good bacteria for the colon.

    • Lymph Nodes: Filter lymph and produce antibodies.

Health Issues of the Lymphatic System

  • Parasitic Filariasis (Elephantiasis): Caused by Brugia sp. parasitic worms transmitted by mosquitoes. The worms block lymphatic vessels, preventing fluid return; causes swelling (oedema).

  • Pregnancy Edema: The growing foetus presses against pelvic veins, slowing blood flow and increasing tissue fluid accumulation in legs.

  • Lack of Albumin: If plasma proteins (especially albumin) are low, blood osmotic pressure decreases, resulting in less fluid reabsorption and causing swelling.

  • Bed-ridden Edema: Patients who cannot move lack skeletal muscle contraction to assist lymph and venous flow, leading to oedema.

The content can be organized into a mind map as follows:

  • Transport in Unicellular vs. Multicellular Organisms

    • Unicellular Organisms Characteristics

    • Small body mass: Larger Total Surface Area/Volume ratio (TSA/V)

    • Short distance for exchange with the environment

    • Substance exchange via simple diffusion (oxygen and carbon dioxide)

    • No need for specialized transport systems

    • Multicellular Organisms Characteristics

    • Large body mass: Smaller TSA/V ratio

    • Larger distance for substance exchange

    • Requires specialized systems (e.g., blood circulatory, respiratory systems)

    • Transports O₂, CO₂, nutrients, waste, antibodies, hormones

    • Circulatory Systems

    • Types: Open and Closed

      • Open Circulatory System

      • Medium: Haemolymph in body cavity

      • Found in invertebrates (e.g., insects, molluscs)

      • Closed Circulatory System

      • Always contained in vessels

      • Single vs. Double Circulatory System

      • Single: Fish (2 chambers)

      • Double: Mammals, birds (4 chambers)

    • Blood Components and Functions

    • Blood Plasma: Contains water, proteins, solutes

    • Red Blood Cells: For oxygen transport

    • White Blood Cells: Immune function

    • Platelets: Clotting

    • Health Issues Related to Circulatory System

    • Atherosclerosis, Angina, Myocardial Infarction, Stroke

  • Human Lymphatic System

    • Formation of Interstitial Fluid

    • Lymphatic Circulation

    • System Components: Tonsils, Thymus, Spleen

    • Health Issues: Elephantiasis, Pregnancy Edema, Bed-ridden Edema