Chapter 10-11 Bio 20

• Arteries


  Blood vessels that carry blood away from the heart
• Arteries


  • Thick walls composed of distinct layers
  • Outer and inner layers - primarily connective tissue
  • Middle layers - muscle fibres and elastic connective tissue
• Blood flow through arteries

  1. Heart contracts, blood surges from heart and enters arteries

  2. Arteries stretch to accommodate inrush of blood

  3. Heart contraction followed by relaxation phase, pressure drops and elastic fibres in artery walls recoil
• Pulse


  Created by changes in the diameter of the arteries (following heart contractions)
• Arterioles


  Smaller arteries that blood from arteries passes into
• Arterioles


  • Middle layer composed of elastic fibres and smooth muscle
  • Autonomic nervous system regulates diameter through vasoconstriction and vasodilation
• Vasoconstriction


  Nerve impulse causes smooth muscle in arterioles to contract, reducing diameter of blood vessel
• Vasodilation


  Relaxation of smooth muscle causes dilation of arterioles, increasing blood flow
• Precapillary sphincter muscles


  Regulate movement of blood from arterioles into capillaries
• Atherosclerosis


  Excess lipid in blood deposited in artery walls, narrowing inside diameter, calcium and minerals form plaque
• Atherosclerosis


  Can narrow arteries and lead to high blood pressure, blood clots can totally block artery and cut off blood flow
• Aneurysm


  Bulge that forms in weakened wall of blood vessel, often due to atherosclerosis, can rupture
• Capillaries


  Sites of fluid and gas exchange between blood and body cells, single layer of cells, very small diameter
• Capillaries


  • Most are 0.4-1.0 mm long with diameter less than 0.005 mm, red blood cells must travel in single file
• Capillary beds


  Easily destroyed, high blood pressure or impact can rupture thin-layered capillaries
• Venules


  Small veins that deoxygenated blood collects in and is carried back to heart
• Venules and veins


  • Walls contain smooth muscle, diameter increases as approach heart
• Venous blood flow


  Valves in veins open in one direction to steer blood toward heart, skeletal muscle contractions also aid venous return
• Up to 65% of total blood volume can be found in the veins
• Pericardium


  Fluid-filled membrane that surrounds the heart
• Heart


  • Two parallel pumps separated by septum, right pump receives deoxygenated blood and pumps to lungs, left pump receives oxygenated blood and pumps to body
• Pulmonary circulatory system


  Vessels that carry blood to and from the lungs
• Systemic circulatory system


  Vessels that carry blood to and from the body
• Heart


  • Four-chambered, composed of two thin-walled atria and two thick-walled ventricles
• One-way blood flow


  Deoxygenated blood from head/upper body enters right atrium via superior vena cava, deoxygenated blood from lower body enters right atrium via inferior vena cava, oxygenated blood from lungs enters left atrium via pulmonary veins
• Atrioventricular (AV) valves


  Separate atria from ventricles, prevent backflow of blood
• Semilunar valves


  Separate ventricles from arteries, prevent backflow of blood
• Aorta


  Largest artery, carries oxygenated blood away from heart
• Coronary arteries


  Supply heart muscle with oxygen and nutrients
• Angina


  Chest pain caused by insufficient oxygen reaching heart
• Cardiac catheterization


  Procedure to detect coronary artery blockage, catheter inserted into artery in groin and pushed up to heart
• Cardiac muscle


  • Striated, branching pattern, can contract without external nerve stimulation (myogenic)
• Sinoatrial (SA) node


  Pacemaker that sets heart's rhythm of about 70 BPM
• Atrioventricular (AV) node


  Conducts nerve impulses from atria to ventricles via Purkinje fibres
• Sympathetic and parasympathetic nervous systems

  Regulate heart rate, sympathetic increases rate, parasympathetic decreases rate
• Tachycardia


  Heart rate exceeding 100 BPM
• Heart sounds


  Lubb-dubb sounds caused by closing of heart valves, diastole when atria and ventricles relaxed, systole when ventricles contract
• Heart murmurs


  Caused by incomplete closing of heart valves, allowing blood leakage
• Leaky heart valves


  Decrease oxygen delivery, but increased blood volume in atrium stretches it and drives blood to ventricle with greater force
• Digitalis


  Medication derived from foxglove plant, used to treat heart conditions