BIOMED SCIE Lecture 6 Cardiovascular Disease I

• To understand and treat (environmental or pharmacological intervention) any disease we must first understand the physiologic and biochemical basis of that disease
• Diseases affecting the cardiovascular system account for ~36% of all deaths in Ireland and one of the leading causes of death
• Diseases affecting the cardiovascular system account for ~33% of all deaths in the EU in 2020
• The disease burden is growing with a steadily increasing morbidity, putting an enormous economical pressure on our (already overburdened) health care system
• The Institute of Public Health in Ireland (IPH) forecasted from 2010-2020 a 50% increase in the number of people living with coronary heart disease and a 48% increase in strokes
• The huge increase in the already heavy demand for our cardiovascular-related health services and a significant additional financial burden to our economy
• Closed circulatory system


  Cardiovascular system
• Cardiovascular system


  • Three main types of blood vessels: arteries, veins, and capillaries
  • Blood flow is one-way in these vessels
  • Four-chambered heart (muscular pump) with two atria and two ventricles
  • Left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood
  • Meets the body's continuous demand for O2

  
• Heart


  • Contains four valves to prevent backflow of blood
  • The atrioventricular (AV) valves separate each atrium and ventricle
  • The semilunar valves control blood flow to the aorta and the pulmonary artery
  • The "lub-dup" sound of a heart beat is caused by the recoil of blood against the AV valves (lub) then against the semilunar (dup) valves
  • Backflow of blood through a defective valve causes a heart murmur
• Cardiac cycle


  • The heart contracts and relaxes in a rhythmic cycle
  • The contraction, or pumping, phase is called systole
  • The relaxation, or filling, phase is called diastole

  
• Heart rate


  The number of beats per minute
• Heart failure


  The heart muscle becomes weak and is unable to supply sufficient blood flow to meet the needs of the body. Body tries to compensate by increasing heart rate.
• Maintaining the Heart's Rhythmic Beat


  • Some cardiac muscle cells are self-excitable, meaning they contract without any signal from the nervous system
  • The sinoatrial (SA) node, or pacemaker, sets the rate and timing (rhythm) at which cardiac muscle cells contract
  • Impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG)
  • Cardiac dysrhythmia (or arrhythmia): group of conditions where there is abnormal electrical activity in the heart (too fast or too slow, and may be regular or irregular)
  • Abnormal awareness of the heart beat (palpitations) sometimes in rare cases indicate a life-threatening condition resulting in cardiac arrest (pacemaker/defibrillator)

  
• Blood Vessel Structure and Function

  • A vessel's cavity is called the central lumen
  • The epithelial layer that lines blood vessels is called the endothelium
  • The endothelium is smooth and minimises resistance
  • Capillaries have thin walls (the endothelium plus its basal lamina) to facilitate the exchange of materials
  • Arteries and veins have an endothelium, smooth muscle, and connective tissue
  • Arteries have thicker walls than veins to accommodate the high pressure of blood pumped from the heart
  • In the thinner-walled veins, blood flows back to the heart mainly as a result of muscle action

  
• Blood


  • Consists of several kinds of cells suspended in a liquid matrix called plasma
  • The cellular elements occupy about 45% of the volume of blood
• Plasma


  • About 90% water
  • Contains inorganic salts in the form of dissolved ions, sometimes called electrolytes
  • Contains plasma proteins, which influence blood pH, osmotic pressure and viscosity
  • Plasma proteins function in lipid transport, immunity and blood clotting
• Cellular Elements


  • Erythrocytes (Red Blood Cells)
  • Leukocytes (White Blood Cells)
  • Platelets

  
• Leukocytes (White Blood Cells)

  • Five major types: monocytes, neutrophils, basophils, eosinophils, and lymphocytes
  • Function in defence by phagocytosing bacteria and debris, by killing infected cells or by producing antibodies
  • Found both inside and outside of the circulatory system
  • Circulating monocytes give rise to tissue macrophages
• Platelets


  • Normal Haemostasis: a well-regulated process that maintains blood in a fluid, clot-free state in normal vessels and induces the rapid formation of a localised haemostatic plug at the site of vascular injury
  • Thrombosis: Pathological state of inappropriate activation of the normal haemostatic process within the non-interrupted vascular system, leading to thrombus (blood clots) formation that blocks blood flow to vital areas
• Arteries branch into arterioles and carry

  blood away from the heart to capillaries
• Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid
• Venules converge into veins and return blood from capillaries to the heart
• Arteries and veins are distinguished by the direction of blood flow, not by O2 content
• Where the Blood begins its flow?

  Right ventricle pumping blood to the lungs
• In the lungs, the blood

  loads O2 and unloads CO2
• Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped through the aorta to the body tissues by the left ventricle
• The aorta provides blood to the heart through the


  coronary arteries
• Blood returns to the heart through the superior vena cava

  and inferior vena cava
• The superior vena cava and inferior vena cava flow into the right atrium
• What is the cardiac cycle

  The heart contracts and relaxes in a rhythmic cycle
• What it is called The contraction phase, or pumping?


  Systole
• The relaxation, or filling, phase is called diastole