Circulatory System - Exam 4

• Circulatory system


  Network of connected tubes to a muscular pump (heart) and constituting a closed system
• Components of the circulatory system

  • Cardiovascular system: blood, heart and blood vessels
  • Lymphatic system: lymph nodes and lymph vessels

  
• Functions of the circulatory system

  • Transportation: CO2, O2, Nutrients, Metabolic wastes, Hormones
  • Regulation: Body Temperature, pH levels
  • Protection: Immune system, Prevents blood loss
• Cardiovascular system


  Components: Blood, Heart, Blood vessels (arteries & veins)

  
• Blood


  Composed of: liquid matrix (plasma), Cells and cell fragments (formed elements)
• Average adult has 5 liters of blood (7-8% of body weight)
• Blood is 4 times thicker than water (viscosity)
• Blood is 1 Celsius degree warmer than body temperature (37C body, 38C blood)
• Body pH is 7.35-7.45
• pH


  Measure of how acidic or alkaline a fluid is. Neutral pH: 7, Acidic: 0-7, Alkaline: 7-14
• After being spun in a centrifuge, blood components separate by weight into 55% plasma and 44% formed elements (erythrocytes, platelets, leukocytes)

  
• Leukocytes


  Contain nucleus and organelles, larger than RBC, most found in body tissues, enter blood vessels by diapedesis, important in body defense, two types: granulocytes/agranulocytes

  
• Erythrocytes


  Most abundant blood cells, lack nucleus and organelles, very small, life span ~120 days, biconcave disc allows for gas transport, transport CO2 and O2, organize in "rouleaux" in capillaries, contain hemoglobin (280 million per cell)

  
• Hemoglobin


  Red-pigmented protein, in charge of gas exchange, consists of 4 subunits with iron, CO2 and O2 bind to these subunits

  
• Platelets


  Fragments of other cells called megakaryocytes, less abundant than RBC, life span 5-9 days, help initiate clotting and vasoconstriction
• Heart


  Cone shaped muscle, weighs 250-350 gm, has four chambers (two atria, two ventricles), has two circulations (systemic and pulmonary)

  
• The right side of the heart receives oxygen-poor blood from the body and pumps it to the lungs, the left side receives oxygenated blood from the lungs and pumps it throughout the body

  
• Pericardium


  Three layered sac: (1) Fibrous pericardium, (2) Parietal layer of serous pericardium, (3) Visceral layer (epicardium) attached to heart

  
• Layers of the heart wall

  • Epicardium (visceral layer of serous pericardium)
  • Myocardium (the muscle)
  • Endocardium (lining the chambers)

  
• Cardiac muscle has a circular and spiral arrangement of muscle bundles in the myocardium

  
• Chambers of the heart

  • Two atria: Right atrium, Left atrium
  • Two ventricles: Right ventricle, Left ventricle

  
• The atria are divided by the interatrial septum, the ventricles are divided by the interventricular septum
• Right atrium


  Receives oxygen-poor blood from the systemic circuit through the superior vena cava, inferior vena cava, and coronary sinus

  
• Right ventricle


  Receives blood from the right atrium and pumps it into the pulmonary circuit via the pulmonary trunk, has trabeculae carneae, papillary muscles, and chordae tendineae

  
• Left atrium


  Receives oxygen-rich blood from the lungs through the pulmonary veins

  
• Left ventricle


  Forms the apex of the heart, has trabeculae carneae, papillary muscles, and chordae tendineae, pumps blood through the systemic circuit via the aorta

  
• The left ventricle has a thicker muscular wall than the right ventricle because it pumps blood against higher resistance in the systemic circulation
• Cardiac skeleton


  Surrounds all four heart valves, composed of dense connective tissue, anchors valve cusps, prevents overdilation of valve openings, main point of insertion for cardiac muscle, blocks direct spread of electrical impulses
• Atrioventricular (AV) valves


  Allow unidirectional blood flow from atria to ventricles

  
• Semilunar valves


  Allow unidirectional blood flow from ventricles to arteries (aortic and pulmonary valves)

  
• In the fetus, blood bypasses the lungs through the foramen ovale and ductus arteriosus

  
• Heart sounds


  "Lub" is the sound of the AV valves closing, "dup" is the sound of the semilunar valves closing
• Heartbeat


  Systole is contraction, diastole is filling/relaxation, normal rate is 60-100 bpm, slow is bradycardia, fast is tachycardia
• The atria contract together, followed by the simultaneous contraction of the two ventricles
• Conducting system of the heart

  Specialized cardiac muscle cells that carry impulses throughout the heart musculature, signaling the chambers to contract in the proper sequence, independent of extrinsic nerve impulses (autorhythmicity)

  
• lub


  The AV valves closing
• dup


  The semilunar valves closing
• Heartbeat


  • Systole: contraction
  • Diastole: filling (relaxation)
• Normal heart rate


  60-100 per minute
• Blood goes to RA, then RV, then lungs, then LA, then LV, then body; but the fact that a given drop of blood passes through the heart chambers sequentially does not mean that the four chambers contract in that order; the 2 atria always contract together, followed by the simultaneous contraction of the 2 ventricles