Lecture 12: Dev't of Cardiovascular System

• How is the embryo nourished during the early phases of development?

  Through diffusion from fluid secreted by uterine glands
• Why does the embryo need a circulatory system as it develops?

  To distribute nutrients and oxygen and remove carbon dioxide and metabolites

  
• When does the circulatory system begin to develop in the embryo?

  As early as the third week of gestation

  
• What is the first functional organ system in the embryo?

  The circulatory system

  
• What is hematopoiesis?

  The formation of blood cells
• In how many overlapping periods does hematopoiesis occur?

  Three overlapping periods
• Where does the first period of blood formation occur?

  In the yolk sac
• What organs become the major blood-forming organs during the second period of hematopoiesis?

  The liver and the spleen
• What is the main blood-forming organ during the third period of hematopoiesis?

  The bone marrow
• Where do the first blood cells appear during development?

  In the visceral mesoderm of the yolk-sac wall
• What are blood islands?

  Spaces in the mesoderm occupied with clusters of haemangioblasts
• What do outer cells of blood islands differentiate into?

  Angioblasts, forming endothelial cells
• What is vasculogenesis?

  The process of spontaneous blood-vessel formation

  
• What is angiogenesis?

  The formation of new vessels by sprouting

  
• What are the first blood cells formed during the mesoblastic period?

  Primitive nucleated erythrocytes
• What evolves into mature erythropoiesis?

  Primitive erythropoiesis
• At what crown-rump length does the mesoblastic period start in cattle?

  8 mm
• What hematopoietic cells can be seen in the liver at 8 mm in cattle?

  Erythropoietic stem cells and megakaryocytes
• When does the liver become the most prominent hematopoietic organ in cattle embryos?

  Up to the 5th month of pregnancy
• What happens to the liver's blood-forming activity during the sixth month?

  It declines and ceases at birth
• When does the spleen become active in hematopoiesis in cattle?

  From the third to the seventh month of pregnancy
• When does the bone marrow begin its hematopoietic activity in cattle?

  At a crown-rump length of about 18 cm during the 4th month
• What will be the main source of blood cells in adult animals?

  The bone marrow
• From what does the heart develop?

  The horseshoe-shaped cardiac tube
• When do embryonic heart beats begin in pigs?

  Day 22 of pregnancy
• When do embryonic heart beats begin in dogs and cattle?

  Day 23 of pregnancy
• When do embryonic heart beats begin in horses?

  Day 24 of pregnancy
• What are the steps for the formation of the four-chambered mammalian heart?

  1. Loop formation of the cardiac tube
  2. Internal division of the cardiac tube
  3. Positioning of the atrium dorsal to the ventricle
  4. Development of the left and right ventricles

  
• What is the shape of the cardiac tube after loop formation?

  1. shaped with the loop pointing ventrally
• What sets the rhythm of the developing heart?

  Pacemakers in the sinus venosus
• What happens to the atrium during the enclosure process?

  It becomes positioned dorsal to the ventricle
• What shape does the loop of the heart take during development?

  The shape of an S

  
• What are the steps for the formation of heart chambers?

  1. Incorporation of the sinus venosus into the atrium
  2. Division of the atrioventricular channel
  3. Division of the atrium
  4. Division of the ventricle and bulbus cordis
  5. Division of the conus cordis and truncus arteriosus

  
• What marks the transition between the ventricle and the bulbus cordis?

  A groove externally and a muscular fold internally
• What does the primitive ventricle expel blood into?

  The conus cordis
• What is the purpose of dividing the bulbus cordis and truncus arteriosus?

  To complete the division of the cardiac tube into right and left halves
• What are the key components involved in the formation of heart chambers?

  • Sinus venosus
  • Atrioventricular channel
  • Atria
  • Ventricles
  • Bulbus cordis
  • Conus cordis

  
• What are the main stages of heart development?

  1. Formation of the cardiac tube
  2. Loop formation
  3. Enclosure of the heart
  4. Division into chambers
  5. Maturation of the heart

  
• What is the first step in the formation of heart chambers?

  Division of the ventricle and the bulbus cordis
• What structure does the bulbus cordis develop into?

  Right ventricle