{"id":341,"date":"2021-01-07T01:49:09","date_gmt":"2021-01-07T01:49:09","guid":{"rendered":"https:\/\/pressbooks.publishdot.com\/anatomyphysiology\/chapter\/6-5-development-of-the-heart\/"},"modified":"2021-12-07T09:04:33","modified_gmt":"2021-12-07T09:04:33","slug":"6-5-development-of-the-heart","status":"publish","type":"chapter","link":"https:\/\/pressbooks.publishdot.com\/anatomyphysiology\/chapter\/6-5-development-of-the-heart\/","title":{"raw":"6.5 Development of the Heart","rendered":"6.5 Development of the Heart"},"content":{"raw":"
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Learning Objectives<\/strong><\/p>\n\n<\/header>\n

\n\nBy the end of this section, you will be able to:\n
    \n \t
  • Describe the embryological development of heart structures<\/li>\n \t
  • Identify five regions of the foetal heart<\/li>\n \t
  • Relate foetal heart structures to adult counterparts<\/li>\n<\/ul>\n<\/div>\n<\/div>\nThe human heart is the first functional organ to develop. It begins beating and pumping blood around day 21 or 22, a mere three weeks after fertilisation. This emphasises the critical nature of the heart in distributing blood through the vessels and the vital exchange of nutrients, oxygen, and wastes both to and from the developing baby. The critical early development of the heart is reflected by the prominent\u00a0heart bulge<\/strong>\u00a0that appears on the anterior surface of the embryo.\n\nThe heart forms from an embryonic tissue called\u00a0mesoderm<\/strong>\u00a0around 18 to 19 days after fertilisation. Mesoderm is one of the three primary germ layers that differentiates early in development that collectively gives rise to all subsequent tissues and organs. The heart begins to develop near the head of the embryo in a region known as the\u00a0cardiogenic area<\/strong>. Following chemical signals called factors from the underlying endoderm (another of the three primary germ layers), the cardiogenic area begins to form two strands called the\u00a0cardiogenic cords<\/strong>\u00a0(Figure 6.5.1). As the cardiogenic cords develop, a lumen rapidly develops within them. At this point, they are referred to as\u00a0endocardial tubes<\/strong>. The two tubes migrate together and fuse to form a single\u00a0primitive heart tube<\/strong>. The primitive heart tube quickly forms five distinct regions. From head to tail, these include the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and the sinus venosus. Initially, all venous blood flows into the sinus venosus, and contractions propel the blood from tail to head, or from the sinus venosus to the truncus arteriosus. This is a very different pattern from that of an adult.\n\n \n\n[caption id=\"attachment_340\" align=\"aligncenter\" width=\"1024\"]\"This Figure 6.5.1. Development of the human heart.<\/strong> This diagram outlines the embryological development of the human heart during the first eight weeks and the subsequent formation of the four heart chambers.[\/caption]\n\nThe five regions of the primitive heart tube develop into recognisable structures in a fully developed heart. The\u00a0truncus arteriosus<\/strong>\u00a0will eventually divide and give rise to the ascending aorta and pulmonary trunk. The\u00a0bulbus cordis<\/strong>\u00a0develops into the right ventricle. The\u00a0primitive ventricle<\/strong>\u00a0forms the left ventricle. The\u00a0primitive atrium<\/strong>\u00a0becomes the anterior portions of both the right and left atria, and the two auricles. The\u00a0sinus venosus<\/strong>\u00a0develops into the posterior portion of the right atrium, the SA node, and the coronary sinus.\n\nAs the primitive heart tube elongates, it begins to fold within the pericardium, eventually forming an S shape, which places the chambers and major vessels into an alignment like the adult heart. This process occurs between days 23 and 28. The remainder of the heart development pattern includes development of septa and valves and remodelling of the actual chambers. Partitioning of the atria and ventricles by the interatrial septum, interventricular septum, and atrioventricular septum is complete by the end of the fifth week, although the foetal blood shunts remain until birth or shortly after. The atrioventricular valves form between weeks five and eight, and the semilunar valves form between weeks five and nine.\n
    \n

    Section Review<\/strong><\/p>\n\n<\/header>\n

    \n\nThe heart is the first organ to form and become functional, emphasising the importance of transport of material to and from the developing infant. It originates about day 18 or 19 from the mesoderm and begins beating and pumping blood about day 21 or 22. It forms from the cardiogenic region near the head and is visible as a prominent heart bulge on the surface of the embryo. Originally, it consists of a pair of strands called cardiogenic cords that quickly form a hollow lumen and are referred to as endocardial tubes. These then fuse into a single heart tube and differentiate into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus, starting about day 22. The primitive heart begins to form an S shape within the pericardium between days 23 and 28. The internal septa begin to form about day 28, separating the heart into the atria and ventricles, although the foramen ovale persists until shortly after birth. Between weeks five and eight, the atrioventricular valves form. The semilunar valves form between weeks five and nine.\n\n<\/div>\n<\/div>\n
    \n

    Review Questions<\/strong><\/p>\n\n<\/header>\n

    \n\n[h5p id=\"158\"]\n\n<\/div>\n<\/div>\n
    \n

    Critical Thinking Questions<\/strong><\/p>\n\n<\/header>\n

    \n\n[h5p id=\"159\"]\n\n[h5p id=\"160\"]\n\n<\/div>\n<\/div>\nClick the drop down below to review the terms learned from this chapter.\n\n[h5p id=\"161\"]","rendered":"
    \n
    \n

    Learning Objectives<\/strong><\/p>\n<\/header>\n

    \n

    By the end of this section, you will be able to:<\/p>\n

      \n
    • Describe the embryological development of heart structures<\/li>\n
    • Identify five regions of the foetal heart<\/li>\n
    • Relate foetal heart structures to adult counterparts<\/li>\n<\/ul>\n<\/div>\n<\/div>\n

      The human heart is the first functional organ to develop. It begins beating and pumping blood around day 21 or 22, a mere three weeks after fertilisation. This emphasises the critical nature of the heart in distributing blood through the vessels and the vital exchange of nutrients, oxygen, and wastes both to and from the developing baby. The critical early development of the heart is reflected by the prominent\u00a0heart bulge<\/strong>\u00a0that appears on the anterior surface of the embryo.<\/p>\n

      The heart forms from an embryonic tissue called\u00a0mesoderm<\/strong>\u00a0around 18 to 19 days after fertilisation. Mesoderm is one of the three primary germ layers that differentiates early in development that collectively gives rise to all subsequent tissues and organs. The heart begins to develop near the head of the embryo in a region known as the\u00a0cardiogenic area<\/strong>. Following chemical signals called factors from the underlying endoderm (another of the three primary germ layers), the cardiogenic area begins to form two strands called the\u00a0cardiogenic cords<\/strong>\u00a0(Figure 6.5.1). As the cardiogenic cords develop, a lumen rapidly develops within them. At this point, they are referred to as\u00a0endocardial tubes<\/strong>. The two tubes migrate together and fuse to form a single\u00a0primitive heart tube<\/strong>. The primitive heart tube quickly forms five distinct regions. From head to tail, these include the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and the sinus venosus. Initially, all venous blood flows into the sinus venosus, and contractions propel the blood from tail to head, or from the sinus venosus to the truncus arteriosus. This is a very different pattern from that of an adult.<\/p>\n

       <\/p>\n

      \"This
      Figure 6.5.1. Development of the human heart.<\/strong> This diagram outlines the embryological development of the human heart during the first eight weeks and the subsequent formation of the four heart chambers.<\/figcaption><\/figure>\n

      The five regions of the primitive heart tube develop into recognisable structures in a fully developed heart. The\u00a0truncus arteriosus<\/strong>\u00a0will eventually divide and give rise to the ascending aorta and pulmonary trunk. The\u00a0bulbus cordis<\/strong>\u00a0develops into the right ventricle. The\u00a0primitive ventricle<\/strong>\u00a0forms the left ventricle. The\u00a0primitive atrium<\/strong>\u00a0becomes the anterior portions of both the right and left atria, and the two auricles. The\u00a0sinus venosus<\/strong>\u00a0develops into the posterior portion of the right atrium, the SA node, and the coronary sinus.<\/p>\n

      As the primitive heart tube elongates, it begins to fold within the pericardium, eventually forming an S shape, which places the chambers and major vessels into an alignment like the adult heart. This process occurs between days 23 and 28. The remainder of the heart development pattern includes development of septa and valves and remodelling of the actual chambers. Partitioning of the atria and ventricles by the interatrial septum, interventricular septum, and atrioventricular septum is complete by the end of the fifth week, although the foetal blood shunts remain until birth or shortly after. The atrioventricular valves form between weeks five and eight, and the semilunar valves form between weeks five and nine.<\/p>\n

      \n
      \n

      Section Review<\/strong><\/p>\n<\/header>\n

      \n

      The heart is the first organ to form and become functional, emphasising the importance of transport of material to and from the developing infant. It originates about day 18 or 19 from the mesoderm and begins beating and pumping blood about day 21 or 22. It forms from the cardiogenic region near the head and is visible as a prominent heart bulge on the surface of the embryo. Originally, it consists of a pair of strands called cardiogenic cords that quickly form a hollow lumen and are referred to as endocardial tubes. These then fuse into a single heart tube and differentiate into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus, starting about day 22. The primitive heart begins to form an S shape within the pericardium between days 23 and 28. The internal septa begin to form about day 28, separating the heart into the atria and ventricles, although the foramen ovale persists until shortly after birth. Between weeks five and eight, the atrioventricular valves form. The semilunar valves form between weeks five and nine.<\/p>\n<\/div>\n<\/div>\n

      \n
      \n

      Review Questions<\/strong><\/p>\n<\/header>\n

      \n
      \n