Circulatory system

• Circulatory system


  Facilitates the transport of materials within the internal environment for exchange with cells at the cell, tissue and organ levels
• Components of blood


  • Plasma
  • Erythrocytes (red blood cells)
  • Platelets
  • Leucocytes (white blood cells)

  
• Blood transfusions


  Rely on determining blood groups and can be used to treat many different diseases and conditions
• Heart


  • Consists of four muscular chambers
  • The two on the left are separated from the two on the right by the septum
  • The upper chambers (atria) receive blood
  • The lower chambers (ventricles) are the pumping chambers
• Blood vessels


  • Arteries
  • Arterioles
  • Capillaries
  • Venules
  • Veins

  
• Arteries


  Muscular blood vessels that carry blood away from the heart
• Arterioles


  Small arteries that direct blood flow to various tissues

  
• Capillaries


  Microscopic blood vessels that connect arterioles and venules and enable the exchange of substances between blood and surrounding tissues

  
• Venules


  Small veins
• Veins


  Blood vessels that carry blood toward the heart

  
• Artery structure


  • Three layers (tunicae): tunica externa, tunica media, tunica interna
  • Thick muscle and elastic fibres allow stretching and contraction to push blood along
• Vein structure


  • Three layers (tunicae): tunica externa, tunica media, tunica interna
  • Thin muscle and elastic fibres
  • Valves to prevent backflow of blood
  • Surrounded by body muscles to squeeze veins and push blood along
• Capillary structure


  Wall is only one cell thick to enable exchange of materials between blood and body cells
• Capillary bed


  A collection of capillaries
• Layers of blood vessels

  • Tunica interna
  • Tunica media
  • Tunica externa

  
• Arteries vs Veins


  Arteries have a relatively thick, muscular wall and small lumen; Veins have a relatively thin wall and large lumen
• Double circulation


  Systemic circulation (oxygenated blood from left ventricle to body, deoxygenated blood to right atrium)

  Pulmonary circulation (deoxygenated blood from right ventricle to lungs, oxygenated blood to left atrium)

  
• Major arteries


  • Carotid Artery
  • Subclavian Artery
  • Aorta
  • Renal Artery
  • Common iliac Artery
  • Femoral Artery
  • Celiac Artery
  • Mesenteric Arteries
• Major veins


  • Jugular Vein
  • Subclavian Vein
  • Inferior vena cava
  • Superior vena cava
  • Renal Vein
  • Common iliac Vein
  • Hepatic Vein
• Components of blood


  • Red blood cells
  • White blood cells
  • Platelets
  • Plasma

  
• Red blood cells


  Contain haemoglobin to carry oxygen, can change shape to squeeze through capillaries, biconcave discs without a nucleus
• White blood cells


  Many different types, contain a large nucleus, include lymphocytes (fight disease) and macrophages (eat and digest microorganisms)

  
• Platelets


  Bits of cell that produce fibrinogen fibres to form blood clots
• Plasma


  Straw-coloured liquid that carries the blood cells and components like carbon dioxide, glucose, amino acids, proteins, minerals, vitamins, hormones, waste
• Blood pressure


  The pressure of the circulating blood against the walls of the blood vessels, highest during ventricular contraction (systole) and lowest during ventricular relaxation (diastole)

  
• Systolic and diastolic pressure

  Systolic pressure is the top number, diastolic pressure is the bottom number when measuring blood pressure
• Normal adult blood pressure is around 120/80
• Measuring blood pressure


  Usually recorded from the brachial artery in the arm, using a sphygmomanometer, reported in millimeters of mercury (mmHg)
• Blood pressure categories


  • Hypotension
  • Normal
  • Prehypertension
  • Stage 1 Hypertension
  • Stage 2 Hypertension

  
• Physiological factors affecting blood pressure

  • Pumping action of the heart
  • Blood volume
  • Blood viscosity
  • Blood vessel resistance

  
• Sinoatrial (SA) node


  Cluster of specialised cardiac cells in the right atrium that initiates the heartbeat

  
• Atrioventricular (AV) node


  Secondary pacemaker that regulates the beating of the ventricles
• Cardiac output


  Total amount of blood pumped by the heart over a particular period of time, affected by stroke volume and heart rate

  
• Stroke volume


  Volume of blood pumped by each ventricle during a cardiac cycle

  
• Frank-Starling law


  The greater the volume of blood entering the heart during diastole, the greater the volume of blood ejected during systolic contraction

  
• Factors affecting stroke volume

  • Venous return
  • Autonomic nervous system
  • Hormones
  • Calcium and potassium levels
• Factors affecting heart rate

  • Hormones
  • Temperature
  • Drugs
  • Salts (potassium and calcium)
  • Emotions
• Inflammation


  Signs: redness, heat, swelling, pain, loss of function

  Functions: prevent spread of damage, dispose of pathogens and debris, set stage for tissue repair
• Increased blood flow during inflammation results in increased local temperature and local cellular metabolism
• Increased capillary permeability and phagocytic migration to the injured tissue occurs during inflammation