2018 Group Project 1
The Contribution of Neural Crest Cells to the Adrenal Medulla
|Projects 2018: 1 Adrenal Medulla | 3 Melanocytes | 4 Cardiac | 5 Dorsal Root Ganglion|
Z5014972 (talk) 12:47, 14 August 2018 (AEST)z5014972 good review article https://link.springer.com/article/10.1007%2Fs12022-009-9070-6
Developmental time course
 - The adrenal gland, consisting of a cortex and a medulla, with each component arising from different embryonic origins. - The adrenal cortex arises from intermediate mesoderm. - The medulla is composed from chromaffinoblast cells of neural crest origin, which migrate. - Medulla much thicker prenatally. - The migrant neuroblast cells infiltrate the adrenal cortex as sympathochromaffin cells from the neural crest.
 - Initially the chromaffin cells are scattered as islands in the cortex - Adrenal gland grows rapidly after second month
 - Week 9 neural crest cells migrate - Until third trimester adrenal gland is abnormally large - Medulla part of sympathetic nervous system - Medulla 10% adult mesoderm - From neuro-ectoderm – modified sympathetic ganglion
NORMAL STRUCTURE AND FUNCTION OF THE ADRENAL MEDULLA
The cells of the adrenal medulla are derived from the neural crest as opposed to the mesodermal origins of the cortex. The medulla contains secretory cells called chromaffin cells, due to the agents they produce when oxidised, such as chromate. These cells secrete epinephrine and norepinephrine in response to various substances such as acetylcholine.
There are three types of cells in the adult adrenal medulla: 1) Epinephrine cells 2) Norepinephrine cells 3) Small granule-containing cells (SGCs) These cells also produce various other peptides such as substance P and neurotensin. The adrenal medulla also contains presynaptic sympathetic ganglion cells.
The tissue and organ structure of the adrenal medulla should be understood with regard to its specialised function within the sympathetic nervous system.
The medullary region of the adrenal glands is tasked with the endocrine secretions of adrenaline and nor-adrenaline in response to environmental stressors that are signalled for by the sympathetic nervous system. That is, the secretion of fight-or-flight response hormones in order to restrict vasculature to the trunk and increase vascular activity in the peripheral musculature.
The adrenal glands are supplied by several branches of the great vessels in the abdominal cavity. The secreted catecholamines in the medulla are directly able to pass to the blood stream this way.
These adrenal glands and their contents are retroperitoneal in the adult and varied in shape, with the left often being semilunar and right being pyramidal. Nervous supply of the adrenal glands is achieved by contributions from the splanchnic nerves of the celiac plexus.
Role of Adrenal Medulla in the Neonate and Adult
Understanding the biochemistry of catecholamines is necessary to see how the adrenal medulla is designed in the stages of embryology and how it is suited for life as a neonate and adult.
The epinephrine and norepinephrine in the neonate and adult work by changing the osmoregulatory state of vasculature.
>Norepinephrine is a constrictor of peripheral vasculature by antagonising the action of surface receptors expressed on the endothelium of blood vessels, specifically Alpha-1 and Alpha-2 receptors, such that vascular resistance increases.
Genes and Transcription Factors Involved with the Adrenal Medulla's Development
Animal models are an integral part of research in embryology. In particular due to the moral concerns regarding the use of humans in scientific research. As a result different animals are used as substitutes to simulate the same environments and hope to achieve results that would also be able to represent humans as well. Two of the most common animals used in the research regarding embryology is the chicken and mouse embryos, for their similarity to human embryos, ease of reproduction (allowing for a large specimen bank), ease of handling, cost effective and there are also no ethical issues limiting its use.
Current research (labs)
- El-Nahla SM, Imam HM, Moussa EA, Elsayed AK & Abbott LC. (2011). Prenatal development of the adrenal gland in the one-humped camel (Camelus dromedarius). Anat Histol Embryol , 40, 169-86. PMID: 21175739 DOI.
- Quinn TA, Ratnayake U, Dickinson H, Nguyen TH, McIntosh M, Castillo-Melendez M, Conley AJ & Walker DW. (2013). Ontogeny of the adrenal gland in the spiny mouse, with particular reference to production of the steroids cortisol and dehydroepiandrosterone. Endocrinology , 154, 1190-201. PMID: 23354096 DOI.
- Kempná P & Flück CE. (2008). Adrenal gland development and defects. Best Pract. Res. Clin. Endocrinol. Metab. , 22, 77-93. PMID: 18279781 DOI.