Unit 7.6

• Topics covered


  • Transport in Invertebrates
  • Transport in Vertebrates
  • The Human Cardiovascular System
  • Blood
• Cardiovascular System Outline


  • Transport in Invertebrates
  • Transport in Vertebrates
  • The Human Cardiovascular System

  
• Transport in Invertebrates


  • Circulatory system functions to move fluid between various parts of the body
  • Small aquatic animals with no circulatory system - each cell is exposed to water and can independently exchange gases and eliminate wastes
  • Pseudocoelomates use a fluid-filled body cavity as a means of transporting substances
  • Coelomate echinoderms may still rely on body fluids for the purpose of locomotion
• Invertebrates with a Circulatory System


  • Two types of circulatory fluids: Blood - contained within blood vessels, Hemolymph - mixture of blood and tissue fluid that fills the body cavity and surrounds internal organs
  • Open Circulatory System - Heart pumps hemolymph via vessels, vessels empty into tissue spaces
  • Closed Circulatory System - Heart pumps blood to capillaries, gases and materials diffuse to and from nearby cells, vessels return blood to heart without contact between blood and tissues

  
• Transport in Vertebrates


  • All vertebrates have a closed circulatory system called a cardiovascular system
  • Vertebrate heart: Atria receive blood from general circulation, Ventricles pump blood out through blood vessels
  • Vertebrate vessels: Arteries - carry blood away from heart, Arterioles - lead to capillaries, Capillaries - exchange materials with tissue fluid, Venules - lead to veins, Veins - return blood to heart

  
• Comparison of Circulatory Pathways


  • Fish - Blood flows in single loop, single atrium and single ventricle
  • Amphibians - Blood flows in double loop, systemic circuit and pulmonary circuit, two atria with a single ventricle
  • Other vertebrates - Blood flows in a double loop, heart divided by septum into separate sides

  
• The Human Heart


  • Fist-sized, cone-shaped, muscular organ, lies within a membranous sac (the pericardium), located between lungs and directly behind sternum, tilted so the apex (pointed-end) is oriented to the left

  
• Structure of the Heart

  • Septum separates the heart into left & right sides, each side has two chambers - upper two chambers are the atria (thin-walled, receive blood from circulation), lower two chambers are the ventricles (thick-walled, pump blood away from heart)
  • Valves open and close to control blood flow through heart - Atrioventricular valves (Tricuspid and Bicuspid), Semilunar valves (Pulmonary and Aortic)

  
• Path of Blood Through Heart


  1. Blood returning to heart from systemic circuit (O2 Poor) - Venae cavae return blood to right atrium, right atrium pumps blood to right ventricle, right ventricle pumps blood to pulmonary circuit (Lungs)

  2. Blood returning to heart from pulmonary circuit (O2 Rich) - Enters left atrium, left atrium pumps blood to left ventricle, left ventricle pumps blood to systemic circuit

  3. Oxygen-poor blood never mixes with oxygen-rich blood (in humans)

  
• Heartbeat


  • Systole - Contraction of heart chambers, Diastole - Relaxation of heart chambers, Cardiac cycle - Two-part pumping action that takes about a second
  • Pulse is a wave effect passing down the walls of the arterial blood vessels when the aorta expands and recoils falling ventricular systole
  • Rhythmic contraction of the heart is due to the cardiac conduction system - Sinoatrial node (SA) keeps the heartbeat regular, Atrioventricular node (AV) signals ventricles to contract

  
• Electrocardiogram (ECG)


  • A recording of electrical changes that occur in the myocardium during cardiac cycle
  • P wave indicates the atria are about to contract, QRS complex signals that the ventricles are about to contract and the atria are relaxing, T wave is due to electrical changes occurring as the ventricular muscle fibers recover
• Blood Pressure


  • Contraction of the heart supplies pressure that keeps blood moving in the arteries - Systolic pressure results from blood forced into the arteries during ventricular systole, Diastolic pressure is the pressure in the arteries during ventricular diastole
  • Blood pressure falls as blood flows from the aorta into arteries and arterioles, Blood flow in the capillaries is slow, Blood pressure in the veins is too low to move blood back to the heart - Skeletal muscle contraction and respiratory pump help move blood in the veins

  
• Cardiovascular Diseases


  • Hypertension - High blood pressure
  • Atherosclerosis - Accumulation of fatty materials between the inner linings of arteries
  • Stroke - Cranial arteriole bursts or is blocked by an embolus
  • Heart attack (myocardial infarction) - Coronary artery becomes completely blocked
  • Angina pectoris - Painful squeezing sensation from myocardial oxygen insufficiency due to partial blockage of a coronary artery
• Blood


  • Transports substances to and from capillaries for exchange with tissue fluid, Helps destroy pathogenic microorganisms, Distributes antibodies, Maintains water balance and pH, Regulates body temperature, Carries platelets and factors to promote clotting and prevent blood loss
• Red Blood Cells (RBCs)


  • Small, biconcave disks, Lack a nucleus and contain hemoglobin - Hemoglobin contains four globin protein chains, each associated with an iron-containing heme group (associates with and carries oxygen), Manufactured continuously in bone marrow
• Blood Types


  • Determined by the presence or absence of a surface antigen - ABO System, Rh System
  • Antibodies in the plasma can cause agglutination - Cross-reactions occur when antigens meet antibodies
• Rh factor


  • 85% of US population + for Rh factor, Rh- individuals don't have antibodies to Rh, but can make them when they encounter Rh
  • During pregnancy, if the mother is Rh negative and the father is Rh positive, the child may be Rh positive - Rh-positive red blood cells may leak across the placenta, The mother will produce anti-Rh antibodies, Antibodies may attack the embryo in a subsequent pregnancy
• White Blood Cells (WBCs)


  • Most types are larger than red blood cells, Contain a nucleus and lack hemoglobin, Important in inflammatory response
  • Granular leukocytes - Neutrophils, Basophil, Eosinophils
  • Agranular leukocytes - Monocytes, Lymphocytes (T cells and B cells)
• Platelets


  • Result from fragmentation of megakaryocytes, Involved in blood clotting (coagulation) - A blood clot consists of RBC's & Fibrin threads
• Capillary Exchange


  1. Capillaries are very narrow and tiny RBCs must go through single file, Walls of capillaries are very thin to facilitate diffusion of nutrients, gases, and wastes

  2. Water exits a capillary near the arterial end, Water enters a capillary near the venous end, Solutes diffuse into and out of a capillary according to their concentration gradient

  3. Oxygen and nutrients diffuse out of capillaries, Carbon dioxide and wastes diffuse into the capillary

  4. Excess tissue fluid collected by lymphatic capillaries, Lymph returns to systemic venous blood in shoulder region