internal fluids lec 6 first quiz coverage

• Exchanging Materials


  • Every organism must exchange materials with its environment
  • This exchange ultimately occurs at the cellular level
• Exchanging Materials (unicellular organisms)


  These exchanges occur directly with the environment
• Exchanging Materials (multicellular organisms)


  Direct exchange with the environment is not possible for most of the cells making up multicellular organisms
• Open and Closed Circulatory Systems


  More complex animals have one of two types of circulatory systems: open or closed

  
• Open and Closed Circulatory Systems


  • Both have three basic components: a circulatory fluid (blood), a set of tubes (blood vessels), and a muscular pump (the heart)

  
• Open Circulatory System


  In insects, other arthropods, and most molluscs, blood (hemolymph) bathes the organs directly
• Closed Circulatory System


  • Blood is confined to vessels and is distinct from the interstitial fluid
  • Closed systems are more efficient at transporting circulatory fluids to tissues and cells

  
• Invertebrate Circulation


  • The wide range of invertebrate body size and form is paralleled by a great diversity in circulatory systems
  • Simple animals, such as cnidarians, have a body wall only two cells thick that encloses a gastrovascular cavity
  • The gastrovascular cavity functions in both digestion and distribution of substances throughout the body

  
• Gastrovascular Cavities


  Some cnidarians, such as jellies have elaborate gastrovascular cavities
• Survey of Vertebrate Circulation


  • Humans and other vertebrates have a closed circulatory system called the cardiovascular system
  • Blood flows in a closed cardiovascular system consisting of blood vessels and a two- to four-chambered heart
  • Arteries carry blood to smaller vessels called arterioles, then to the tiny capillaries - the sites of chemical exchange between the blood and interstitial fluid
  • Blood then flows from capillaries into venules then to larger veins which return blood to the heart

  
• Fishes


  • A fish heart has two main chambers: one ventricle and one atrium
  • Blood pumped from the ventricle travels to the gills, where it picks up O2 and disposes of CO2
• Amphibians


  • Frogs and other amphibians have a three-chambered heart, with two atria and one ventricle
  • The ventricle pumps blood into a forked artery that splits the ventricle's output into the pulmocutaneous circuit and the systemic circuit

  
• Reptiles


  • Reptiles have double circulation with a pulmonary circuit (lungs) and a systemic circuit
  • Turtles, snakes, and lizards have a three-chambered heart
  • Crocodilians have a four-chambered heart
• Mammals and Birds


  • In all mammals and birds, the ventricle is completely divided into separate right and left chambers
  • The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood
  • A powerful four-chambered heart was an essential adaptation of the endothermic way of life characteristic of mammals and birds

  
• Mammalian Circulation: The Pathway

  1. Heart valves dictate a one-way flow of blood through the heart

  2. Blood begins its flow with the right ventricle pumping blood to the lungs

  3. In the lungs, the blood loads O2 and unloads CO2

  4. Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped to the body tissues by the left ventricle

  5. Blood returns to the heart through the right atrium

  
• The Mammalian Heart: A Closer Look


  • The heart contracts and relaxes in a rhythmic cycle called the cardiac cycle
  • The contraction, or pumping, phase of the cycle is called systole
  • The relaxation, or filling, phase of the cycle is called diastole
  • The heart rate, also called the pulse is the number of beats per minute
  • The cardiac output is the volume of blood pumped into the systemic circulation per minute

  
• Heart


  • The heart is located in the mediastinum and is enclosed by the pericardial cavity

  
• Layers of the Heart Wall


  • Epicardium: visceral layer of serous pericardium
  • Myocardium: consists mainly of cardiac muscle
  • Endocardium: sheet of endothelium resting on a thin layer of CT; lines heart chambers and makes up heart valves

  
• The Human Heart has 4 Chambers


  • L&R atria (receiving chambers)
  • L&R ventricles (pumping chambers)
  • The atria are separated by an interatrial septum
  • The ventricles are separated by an interventricular septum

  
• The Human Heart has 4 Valves


  • 2 atrioventricular valves: R atrioventricular (= tricuspid) valve (3 cusps), L atrioventricular (= mitral or bicuspid) valve (2 cusps)
  • 2 semilunar valves (each with 3 cusps): Pulmonary semilunar valve (between R ventricle and pulmonary trunk), Aortic semilunar valve (between L ventricle and aorta)
  • Cusps are flaps made of endocardium and reinforced by cores of dense CT

  
• Superior View of Heart Valves

  
• Great Vessels of the Heart

  • Inferior vena cava
  • Superior vena cava
  • Pulmonary trunk
  • L pulmonary A
  • R pulmonary A
  • Aorta [A] (ascending, aortic arch, descending)
  • Entering L atrium posteriorly: 2 L and 2 R pulmonary VV

  
• The Heart's Own Blood Supply


  • Right coronary artery (emerges from R side of aorta, descends in coronary sulcus between R atrium and R ventricle, supplies R atrium, most of R ventricle, and 80% of the time, the inferior portion of the L ventricle as well)
  • Left coronary artery (arises from L side of Aorta, VERY SHORT, major branches: Circumflex A, Anterior interventricular A (= anterior descending A) which supplies anterior wall of both ventricles, Circumflex supplies L atrium and posterior part of L ventricle)

  
• Blood is pumped through 2 circuits


  • Pulmonary Circuit: blood vessels that carry blood to and from the lungs
  • Systemic Circuit: blood vessels that carry blood to and from the rest of the body

  
• The Heart's Own Blood Drainage


  • Cardiac veins carry deoxygenated blood from the heart tissues
  • Almost all venous blood from the heart drains into the coronary sinus, which feeds into the R atrium

  
• Maintaining the Heart's Rhythmic Beat


  • Some cardiac muscle cells are self-excitable, meaning they contract without any signal from the nervous system
  • The systemic circuit is longer than the pulmonary circuit, therefore the left ventricle must be able to generate greater force and pressure with each pump, than the right ventricle
  • Atria are relatively thin walled; they pump blood in the direction of gravity and only have to move blood into the ventricles

  
• Blood Flow Into and Out of the Heart


  Both atria contract at about the same time just as both ventricles contract at about the same time

  
• The Cardiac Cycle


  • It is the period of time that commences with the contraction of the atria and ends with ventricular relaxation
  • It is a carefully regulated sequence of steps that we think of as beating of the heart
  • Four Stages: a) Atrial systole (0.1 sec), b) Ventricular systole (0.3 sec), c) Atrial diastole (0.7 sec), d) Ventricular diastole (0.5 sec)

  
• Systole and Diastole


  • Systole = the period of ventricular contraction
  • Diastole = the period of ventricular relaxation
• Chamber-to-Chamber Valves
• Chamber-to-Vessel Valves
• Heart Sounds


  • Closure of heart valves causes vibrations in adjacent heart walls and blood; these vibrations constitute the heart sounds
  • "Lubb": Produced by the closing of AV valves at the start of ventricular systole
  • "Dupp": Produced by the closing of the semilunar valves at the end of ventricular systole

  
• Systole = 1st heart sound, A-V valves close = "lubb"
• Diastole = 2nd heart sound, pulmonic and aortic semi-lunar valves close = "dupp"

  
• Maintaining the Heart's Rhythmic Beat


  • A region of the heart called the sinoatrial (SA) node, or pacemaker, sets the rate and timing at which all cardiac muscle cells contract
  • Impulses from the SA node travel to the atrioventricular (AV) node
  • At the AV node, the impulses are conducted through the bundle of His and then travel to the Purkinje fibers that make the ventricles contract

  
• Maintaining the Heart's Rhythmic Beat


  • The impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG)
  • The pacemaker is influenced by nerves, hormones, body temperature, and exercise
• Blood Vessel Structure and Function


  • The "infrastructure" of the circulatory system is its network of blood vessels
  • All blood vessels are built of similar tissues and have three similar layers

  
• 44


  4/30/24
• diastole


  2nd heart sound
• Maintaining the Heart's Rhythmic Beat


  1. Sinoatrial (SA) node sets the rate and timing

  2. Impulses from SA node travel to atrioventricular (AV) node

  3. At AV node, impulses are conducted through bundle of His and to Purkinje fibers that make ventricles contract