And Linear Heart Tube Formation

The cells that will become the heart are among the first cell lineages formed in the vertebrate embryo (6,7). By day 15 of human development, the primitive streak has formed (8), and the first mesodermal cells to migrate (gastrulate) through the primitive streak are cells fated to become the heart (9,10) (Fig. 2). These mesodermal cells migrate to an anterior and lateral position where they form bilateral primary heart fields (Fig. 1A) (11). Studies of chick development have not supported the previously held notion of a medial cardiac crescent that bridges the two bilateral primary heart fields (12). Complete comparative molecular and developmental studies between the chick and mouse are required to confirm these results. The posterior border of the bilateral primary heart field reaches to the first somite in the lateral mesoderm on both sides of the midline (Fig. 1A) (3,12).

At day 18 of human development, the lateral plate meso-derm is split into two layers: somatopleuric and splanchno-pleuric (8). It is the splanchnopleuric mesoderm layer that contains the myocardial and endocardial cardiogenic precursors in the region of the primary heart fields as defined above.

Fig. 1. The four major contributors to heart development illustrated in the chick model system: primary heart field, secondary heart field, cardiac neural crest, and proepicardium. (A) Day 1 chick embryo (equivalent to day 20 of human development). Red denotes primary heart field cells. (B) Day 2.5 chick embryo (equivalent to ~5 wk of human development). Green denotes cardiac neural crest cells; yellow denotes secondary heart field cells; blue denotes proepicardial cells. (C) Day 8 chick heart (equivalent to ~9 wk of human development). Green dots represent derivatives of the cardiac neural crest; yellow dots represent derivatives of the secondary heart field; red dots represent derivatives of the primary heart fields; blue dots represent the derivatives of the proepicardium. Ao, aorta; APP, anterior parasympathetic plexis; Co, coronary vessels; E, eye; H, heart; IFT, inflow tract; LA, left atrium; LV, left ventricle; Mb, midbrain; NF, neural folds; OFT, outflow tract; Otc, otic placode; P, pulmonary artery; RA, right atrium; RV, right ventricle; T, trunk.

Fig. 1. The four major contributors to heart development illustrated in the chick model system: primary heart field, secondary heart field, cardiac neural crest, and proepicardium. (A) Day 1 chick embryo (equivalent to day 20 of human development). Red denotes primary heart field cells. (B) Day 2.5 chick embryo (equivalent to ~5 wk of human development). Green denotes cardiac neural crest cells; yellow denotes secondary heart field cells; blue denotes proepicardial cells. (C) Day 8 chick heart (equivalent to ~9 wk of human development). Green dots represent derivatives of the cardiac neural crest; yellow dots represent derivatives of the secondary heart field; red dots represent derivatives of the primary heart fields; blue dots represent the derivatives of the proepicardium. Ao, aorta; APP, anterior parasympathetic plexis; Co, coronary vessels; E, eye; H, heart; IFT, inflow tract; LA, left atrium; LV, left ventricle; Mb, midbrain; NF, neural folds; OFT, outflow tract; Otc, otic placode; P, pulmonary artery; RA, right atrium; RV, right ventricle; T, trunk.

Table 1

Developmental Timeline of Human Heart Embryology

Days of human Developmental development process

Table 1

Developmental Timeline of Human Heart Embryology

Days of human Developmental development process

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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