Transport in Animals

Left Atrium (LA)

  • Receives oxygenated blood from the lungs.

  • Four pulmonary veins open into the left atrium.

Left Ventricle (LV)

  • Located below the left atrium.

  • Largest chamber with thickest walls; pumps oxygenated blood throughout the body.

  • Blood flows from the left atrium to the left ventricle.

  • Oxygenated blood is pumped via the aorta.
    Note: Arteries carry blood away from the heart; veins carry blood to the heart.

  • The pulmonary arteries are the only arteries in the body that transport deoxygenated blood. All the other arteries transport oxygenated blood.

  • The pulmonary veins are the only veins in the body that transport oxygenated blood. All the other veins transport deoxygenated blood.

Cardiac Valves

  • Prevent backflow of blood, ensuring one-way flow.

Tricuspid Valve

  • Between the right atrium and right ventricle; has three flaps.

  • Flaps connect to ventricle walls via chordae tendineae and papillary muscles.

  • Prevents backflow into the right atrium when the right ventricle contracts.

Bicuspid (Mitral) Valve

  • Between the left atrium and left ventricle; has two flaps.

  • Prevents backflow into the left atrium when the left ventricle contracts.

Semilunar Valves

  • Located at the base of the aorta and pulmonary artery.

  • Prevent blood from flowing back into the ventricles.

Functioning of the Heart

  • Pumps blood to transport O2O2 and nutrients and remove CO2CO2 and wastes.

Events of the Cardiac Cycle

  • Heart beats 72 times per minute; each beat lasts 0.8 seconds.

  • Systole: Contraction; Diastole: Relaxation.

  • Three phases: Atrial systole, Ventricular systole, General diastole.

Atrial Systole (0.1 s)

  • Atria contract, squeezing blood into ventricles.

Ventricular Systole (0.3 s)

  • Ventricles contract, pumping blood into pulmonary artery and aorta.

General Diastole (0.4 s)

  • Ventricles and atria relax; blood flows into atria and then ventricles.

Mechanisms Controlling the Heartbeat

  • Cardiac muscle contracts and relaxes automatically.

  • Heartbeat sound: lub-dup.

  • Lub: Closing of bicuspid and tricuspid valves.

  • Dup: Closing of semilunar valves.

How Does the Heart Beat?

  • SA node (pacemaker) in the right atrium initiates contraction impulses.

  • AV node at the septum transmits impulses to the bundle of His.

  • Bundle of His extends through the septum, branching into Purkinje fibres.

  • Purkinje fibres conduct impulses for ventricular contraction.

Control of the Heartbeat

  • Controlled by nervous system and hormones.

  • Autonomic nervous system: Sympathetic nerves accelerate, parasympathetic nerves slow.

  • Adrenaline and thyroxine accelerate the heartbeat.

Effect of Exercise on the Heartbeat

  • More respiration occurs in muscles, increasing CO2CO2.

  • Receptors detect CO2CO2 increase, sending impulses to the brain.

  • Sympathetic nerves accelerate heartbeat.

  • Increased blood flow delivers O2O2 and removes CO2CO2.

Blood Vessels

  • Blood is transported in a closed system of vessels.

  • Three types: Arteries, Capillaries, Veins.

Arteries

  • Carry blood away from the heart.

  • Walls have three layers: fibrous, muscle/elastic, and endothelial.

  • Middle layer stretches and resists high pressure.

  • No valves, except for semilunar valves in the aorta and pulmonary artery.

Capillaries

  • Microscopic tubes between tissue cells.

  • Walls are one thin layer of endothelium.

  • Exchange of substances occurs between blood and cells.

  • Blood flow is slow for effective gas exchange.

Veins

  • Carry blood back to the heart.

  • Walls have three layers (thinner than arteries).

  • Blood flows under low pressure.

  • Skeletal muscle contraction aids blood flow.

  • Semilunar valves prevent backflow.

The Lymphatic System
Blood and Lymph as Tissue
Blood

  • Liquid connective tissue.

Blood Plasma

  • 90% water, 10% dissolved substances.

  • Transports blood cells, proteins, nutrients, wastes, gases, enzymes, hormones, and heat.

Blood cells

  • Erythrocytes, Leucocytes, Thrombocytes.

Erythrocytes (red blood cells)

  • No nuclei; contain haemoglobin.

  • Transport O2O2 and CO2CO2.

Leucocytes (white blood cells)

  • Large nuclei; irregular shape.

  • Protect against infections and produce antibodies.

Thrombocytes (blood platelets)

  • Cell fragments without nuclei.

  • Aid in blood clotting.

Lymph

  • Tissue fluid that enters lymphatic vessels.

  • Three fluids: blood plasma, tissue fluid, lymph.

Structure of the Lymphatic System

  • Lymph capillaries unite into larger vessels.

  • Vessels connect to the thoracic duct and right lymphatic duct.

  • Lymph re-enters the blood system via subclavian veins.

  • Movement via organ and muscle action; valves prevent backflow.

  • Lymph nodes filter foreign particles and produce lymphocytes and antibodies.

  • Lymph nodes swell during infections.

Relationship Between Lymphatic System and Blood System

  • Lacteals in the small intestine absorb fats.

  • The lymphatic system transports tissue fluid back to the bloodstream.

Functions of the Lymphatic System

  • Prevents tissue fluid accumulation.

  • Transports plasma proteins back to the bloodstream.

  • Inefficient drainage causes oedema.

Cardiovascular Diseases

  • Diseases of the heart and blood vessels.

  • Often caused by poor lifestyle choices.

High Blood Pressure (Hypertension) and Low Blood Pressure (Hypotension)

  • Blood pressure: The force of blood on vessel walls.

  • Systolic pressure: Maximum pressure during ventricular contraction.

  • Diastolic pressure: Minimum pressure during cardiac muscle relaxation.

Measuring Blood Pressure

  • Measured with a sphygmomanometer in mmHg.

  • Normal: 120/80.

  • Influenced by stress, medication, and disease.

  • Hypertension: High pressure for a long time.

  • Hypotension: Low blood pressure.

  • Hypertension can lead to stroke or heart attack; managed by medication and lifestyle changes.

Stroke

  • Loss of brain function due to blood supply disruption.

  • Caused by blood clots or burst blood vessels.

  • Can lead to paralysis, speech difficulties, vision loss, and death.

  • Risk factors: age, high blood pressure, diabetes, high cholesterol, smoking.

Heart Attack

  • Interrupted blood supply to cardiac muscle.

  • Narrowed arteries from fat deposits (atherosclerosis).

  • Blood clots (thrombi) block coronary arteries.

  • Can result in angina (chest pain) or heart attack.

Treatment of Cardiovascular Diseases

  • Medication: dissolving clots, thinning blood, controlling blood pressure.

  • Angioplasty: stretching narrowed arteries.

  • Bypass operation: restoring blood flow with alternative routes.

  • Heart transplant: replacing an unhealthy heart.

Resting Pulse Rate in Relation to Fitness

Pulse? It is the regular contraction and relaxation of an artery, caused by the heart pumping blood through the body. It can be felt where an artery lies close to the surface, e.g., in your wrist or carotid (neck) arteries.

Pulse rate? Number of heartbeats per minute.

  • Fitter individuals have lower resting pulse rates (40-60 beats/minute).

  • Stronger cardiac muscle pumps more blood per beat.

  • Heart rate returns to normal faster in fitter individuals.

Blood Groups

Erythrocytes have antigens on their surface (A and B).

Antigen? A substance that is recognised by the body as foreign and stimulates the immune system to produce
antibodies.

Human blood is classified by the ABO system, based on the presence or absence of A and B antigens.

Four blood groups:

blood group A - has A antigens on the red blood cells.

blood group B - has B antigens on the red blood cells.

blood group AB - has both A and B antigens on the red blood cells.

blood group O - has no antigens on the red blood cells.

Antibodies against A and B antigens are in the blood plasma (anti-A and anti-B antibodies). If a person has a specific antigen on their red blood cells, they will not have the corresponding antibody in their plasma to avoid self-attack.
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