This book presents an overview of a new group of progenitor stem cells. Their origins were originally detected in light- and electron microscopical sections of plastic embedded human embryonal and fetal organs.

The distribution of these cells can result in a large quantity of ectopic stem cells. The observation of these ectopic stem cells leads us to postulate the existence of a basic wave of stem cell progenitors. This process proceeds earlier and independently from germ cell migration. This first wave of progenitor stem cell migration initially reaches the peri-aortal AMG-region (Aortal-Mesonephric-Gonadal region). From here, some of these progenitor cells enter the aorta, are distributed through the vascular system and become the embryonal stem cells (reserve cells) in many peripheral tissues. A second part delivers progenitor cells for the adrenal 'anlage'. Within the peripheral Zona definitiva of the adrenal cortex the progenitor cells multiplicate and subsequently leave the adrenal cortex through a gate of the capsule. The progenitor cells arrive at the pre-aortal sympathic plexus ('second brain'). Within the plexus ganglia they form new organ-like clusters, the paraganglia. In a second process the progenitor cells (Chromaffine cells) enter sympathetic nerve bundles. Here an 'axonal migration' starts, which guides the progenitor cells to several peripheral organs. During this migration process the stem cells develop into their final state. In the adrenal cortex the ingrowing nerves guide the stem cells to the adrenal medulla. In the pancreas the ingrowing nerve fibers guide the stem cells to the islets.

These newly detected stem cells represent a specific developmental step which is found only in humans.

Inhalt
Preface.- Chapter 1. Distribution of progenitor stem cells from the AMG-system an the adrenal.- Introduction.- Materials and Methods.- Chapter 1.1. The 'bidirectional' migration of human primordial germ cells (PGCs) including other stem cells.- Chapter 1.2. Distribution of fetal stem cells on the AMG-region, and how one group enters the human aorta and circulates in embryonal capillaries.- Chapter 1.3. Formation of the adrenal primordium in the AMG region and the development of the human adrenal cortex, notably the Zona definitiva.- Chapter 1.3.1 First stage of the adrenal gland development.- Chapter 1.3.2 Second period of the adrenal gland development.- Chapter 1.3.3** **The third period of midgestational adrenal development.- Chapter 1.4. Further differentiation of the AMG-region: Development of the sympathetic cords, ganglia and paraganglia adjacent to the adrenal 'anlage': the 'second brain'.- Chapter 1.4.1 The Plexus coeliacus.- Chapter 1.4.2 The formation of paraganglia within the autonomic plexus.- Chapter 1.5. Discussion of the immigration of fetal stem cells into the autonomic NS, their role in the formation of the paraganglia and their axonal migration.- Chapter 2. Development of the adrenal medulla and other endocrine glands.- Chapter 2.1. Development of the autonomic innervation of the adrenal gland and the formation of the adrenal medulla.- Chapter 2.2. Development of the autonomic innervation of the human pancreas and origin of the pancreatic islets.- Chapter 2.3. Development of the human parathyroid gland.- Chapter 2.4. Fetal Stem Cells at perigonadal and intragonadal sites.- Chapter 2.5. Down-growth of autonomic nerves in the stomach and the intestine tube: the migration and the whereabouts of the stem cells.- Chapter 2.6. Discussion: the process of stem cell distribution and migration within the autonomic nerves to organs of the human developing organism.- Chapter 3. Final view on stem cell origin during human development.- Introduction.- Chapter 3.1. The origin of the stem cells of group II.- Chapter 3.2. Types of stem cells.-  Chapter 3.2.1 Embryonic stem cells (eSCs).- Chapter 3.2.2 Naïve stem cells and cells with primed pluripotent states.- Chapter 3.2.3 Neural crest stem cells (NCSCs).- Chapter 3.2.4 Induced stem cells (iSCs).- Chapter 3.2.5 Adult stem cells (adult SCs).- Chapter 3.3. Further stem cell categories during the human developmental process: the rôle of the AMG-region.- Chapter 3.4. How fetal stem cells deliver the progenitor cells of the adrenal cortex and how they pass into the local autonomic plexus.- Chapter 3.5. The cells multiplicated in the adrenal cortex become fetal stem cells.- Chapter 3.6. The role of the paraganglia during the stem cell storage and stem cell distribution.- Chapter 3.7. A new phylogenetical step during human development: the evolution of a new feedback system permitting a lifelong maintenance of stem cell supply. The paraganglia, autonomic nervous system, and 'axonal' stem cell migration system.- Chapter 3.8. Remaining questions and perspectives.- References.