Circulatory

• Circulatory System


  Cardiovascular system composed of the heart (cardio) and blood system (vascular)

  
• Function of the Circulatory System

  • Delivers essential nutrients and oxygen throughout the body
  • Removes both metabolic wastes and pathogens before harmful concentrations are reached
  • Serves all bodily functions but is most closely associated with respiration, excretion, osmoregulation, and digestion
• Open Circulatory System


  Blood not enclosed in blood vessels, blood (or hemolymph) circulates around the organs, heart pumps blood into the hemocoel or body cavity, tissues surrounding the vessels are not directly bathed by blood, high percentage of blood volume, low blood pressure
• Closed Circulatory System

  Blood contained inside blood vessels, blood circulates unidirectionally from the heart, high pressure needed for blood to reach all parts of the body, blood volume considerably lower
• Fish Heart

  • The heart is the pump that produces the pressure needed for blood to circulate
  • Composed of 4 chambers: Sinus venosus, Atrium, Ventricle, Conus or bulbus arteriosus

  
• Valves in Fish Heart

  • Sinoatrial aperture, Atrio-ventricular aperture, Semilunar or bulbar valve
  • Prevent backflow of blood and maintain pressure in the circulatory system
• Sinus venosus

  Thin-walled triangular sac located at the base of the heart, attached to the transverse septum, weakly contractile

  
• Atrium

  Large contractile chamber situated dorsal to the ventricle, thin-walled single and undivided chamber with distensible spongy cavity
• Ventricle


  Thick-walled muscular contractile chamber, main pumping and propulsive chamber responsible for the generation of the blood pressure
• Conus arteriosus (elasmobranch)/bulbus arteriosus (teleost)

  Bulbous or tubular in shape and contains the semilunar/bulbar valve, thick-walled and extends between the ventricle and the ventral aorta, extremely elastic to store and release kinetic energy
• Fish Circulatory System

  1. Deoxygenated blood enters sinus venosus

  2. Passes through sinoatrial aperture into atrium

  3. Passes through atrioventricular aperture into ventricle

  4. Goes to conus or bulbus arteriosus via bulbar/semilunar valve before exiting heart
• Blood Vessels

  • Arteries carry blood from heart to tissue, have smaller internal diameter, thicker walls, higher blood pressure, difficult to find if animal is dead, deeper
  • Veins carry blood from tissue to heart, have bigger internal diameter, thinner walls, lower blood pressure, usually filled with blood if animal is newly dead, more superficial
• Ventral Aorta

  Straight thick-walled tube that lies on the mid-ventral line of the floor of the pharynx, has a muscular swelling at the point of origin from the bulbus arteriosus in teleosts, appears to be an extension of the conus arteriosus in elasmobranchs, branches off to 4 pairs of afferent branchial arteries
• Dorsal Aorta

  Main route of blood transport from the gills (via the efferent branchial arteries) to the body, carrying oxygenated blood, unpaired and located behind the gills, extends posteriorly, lies directly beneath the vertebral column, becomes the caudal artery posteriorly, several major arteries branch off
• Arterioles

  Smaller branches of arteries
• Venules


  Smaller branches of veins
• Capillaries


  Smaller blood vessels with thin walls that allow gas exchange, nutrient transfer and waste removal between the blood and the tissue fluid
• In the typical circulatory route, the blood of the fish passes through only one set of capillaries
• Portal Systems


  Capillary networks inserted between 2 venous segments, blood draining from one capillary bed flows through a portal vein that branches again to supply another capillary bed
• Hepatic Portal System


  Carries blood from the digestive tract and associated glands to the liver
• Renal Portal System


  Carries blood from the posterior portion of the body to the kidneys, absent in mammals but well developed in fishes
• Fish Circulatory System


  1. Venous (deoxygenated) blood enters heart and is pumped to the gills for oxygenation via ventral aorta and afferent branchial arteries

  2. Blood enters gills for gas exchange

  3. Oxygenated arterial blood exits gills through efferent branchial arteries that join to form dorsal aorta

  4. Blood flows to different body parts through arteries branching off dorsal aorta

  
• Blood Composition


  Composed of blood cells suspended in plasma that are circulated throughout the body tissues
• Blood Volumes


  Range from 3-7% of total body weight in bony fishes, 4-8% in elasmobranchs, 8-20% in agnatha
• Primary Hematopoietic Organs


  Mesodermal envelope surrounding the gut in hagfish, Leydig organ, Epigonal organ, spleen in elasmobranchs, spleen and kidney in teleosts
• Blood Cells


  • Erythrocytes (red blood cells)
  • Leukocytes (white blood cells)
  • Thrombocytes (platelets)
• Erythrocytes


  Most abundant cells in fish blood, contain hemoglobin and carry oxygen, nucleated and show a wide range of sizes
• Leukocytes


  Less abundant than RBCs, include granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes)
• Thrombocytes

  Function in the clotting of circulating fluids, appear as spiked, spindle, oval, and lone nucleus forms
• Titrimetry


  Analytical methods widely used in analytical chemistry to determine acids, bases, oxidants, reductants, metal ions, proteins, and many other species
• Titration


  1. Reaction between the analyte (titrand) and a standard reagent (titrant), which is added in increments

  2. The point of chemical equivalence (equivalence point) is signaled by an indicator color change or a change in an instrumental response

  3. Common reactions involved: acid–base, redox, precipitation, complexation

  
• Titration


  • The reaction stoichiometry between the titrant and the titrand should be known
  • The titration reaction effectively must proceed to completion
  • The titration reaction must occur rapidly
  • There must have a suitable method for accurately determining the end point

  
• Titration: General Procedure

  1. Standardization of standard solution

  2. Titration of sample

  3. Data analysis
• Titrant


  A standard solution of exactly known concentration of a reagent
• Primary/secondary standard

  A compound whose purity was established by a chemical analysis, used as the reference material in titrimetric analysis
• Standardization


  Process in which the concentration of titrant solution is established

  
• Equivalence point


  The point in a titration in which the amount of the dispensed titrant is equivalent to the amount of an analyte, according to the stoichiometry of the reaction

  
• End point

  The point in a titration in which a change of a physical property of the titrated sample solution (e.g., the change of color) associated with achieving the equivalence point is observed

  
• Indicator


  A substance added to a titrated sample whose change of physical property appears at or close to the equivalence point and indicates the end point of titration

  
• Titration curve


  A plot showing the relationship between a p-function of an analyte (or a reagent, in back titrations) concentration, or a signal registered by an instrument, and a volume of titrant introduced to a sample, usually applied to identify the end point in titrations with instrumental detection