Endocrine System Development

Introduction

Human adrenal gland (Week 10)

The endocrine system resides within specific endocrine organs and both organs and tissues with other specific functions. Epithelia (ectoderm and endoderm) form the majority of the “ductless” endocrine glands like gastrointestinal and skin associated “ducted” glands. Differentiation of several also organs involves a epithelial/mesenchye interaction, seen in repeated in many differentiation of many different tissues. The endocrine glands produce hormones, which are distributed by the vascular system to the many body tissues, subsequently these organs are richly vascularized.

Hormones are recognised by either cell surface receptors (modified amino acids, peptides, proteins) or cytoplasmic/nuclear receptors (steroids). Hormones “orchestrate” responses in other tissues, including other endocrine organs, and these overall effects can be similar or different in different tissues. In addition, these hormone effects (like music) can be rapid, slow, brief, diurnal, or long-term. Hormone effects can be mimicked, stimulated, and blocked by therapeutic drugs, nutritional and environmental chemicals.

The human fetus is dependent upon endocrine development for hormones, which support normal development. Peripheral endocrine glands (thyroid, pancreas, adrenals, gonads) form early in the second month from epithelial/mesenchye interactions and differentiate into the third month. The fetus also has a unique hormonal system that combines not only its own developing endocrine system, but also that of the placenta and maternal hormones.

Abnormal endocrine development/function can impact on many different systems. For example, insufficient maternal dietary iodine impacts on fetal thyroid gland thyroid hormone production, which in turn can lead to abnormal neural development. Alternatively, we now know many environmental and therapeutic chemicals have a wide range of effects on the endocrine system.

Sex hormones from the gonads have significant effects prenatally and postnatally, specifically at puberty with a role to play in male/female biological maturity and have wide actions throughout the body.

This current page provides a general introduction to the endocrine system, use the links below to explore development of specific endocrine organs.

Historic Embryology - Endocrine
1903 Islets of Langerhans \| 1903 Pig Adrenal \| 1904 interstitial Cells \| 1908 Pancreas Different Species \| 1908 Pituitary \| 1908 Pituitary histology \| 1911 Rathke's pouch \| 1912 Suprarenal Bodies \| 1914 Suprarenal Organs \| 1915 Pharynx \| 1916 Thyroid \| 1918 Rabbit Hypophysis \| 1920 Adrenal \| 1935 Mammalian Hypophysis \| 1926 Human Hypophysis \| 1927 Adrenal \| 1927 Hypophyseal fossa \| 1930 Adrenal \| 1932 Pineal Gland and Cysts \| 1935 Hypophysis \| 1935 Pineal \| 1937 Pineal \| 1935 Parathyroid \| 1940 Adrenal \| 1941 Thyroid \| 1950 Thyroid Parathyroid Thymus \| 1957 Adrenal

| original page

Some Recent Findings

Endocrine Pancreas^[1] "The transcription factor Pax6 functions in the specification and maintenance of the differentiated cell lineages in the endocrine pancreas. It has two DNA binding domains, the paired domain and the homeodomain, in addition to a C-terminal transactivation domain. The phenotype of Pax6-/- knockout mice suggests non-redundant functions of the transcription factor in the development of glucagon-expressing alpha-cells as this cell type is absent in the mutants."
Pituitary Gland Development^[2] recent review article looking at molecular mechanisms of development.

Textbooks

In general, not dealt with as a system in many textbooks, so various chapters: nervous system, head, gastrointestinal tract, reproductive organs, etc.

Human Embryology (3rd ed.) Larson Chapter 9 Gastrointestinal, Chapter 10 Gonad, Kidney Chapter 12 Head
The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapters 10: p230-233; Ch12: p280-282; Ch13: p319-347
Lectures - 2010 | 2009 | 2008 | Medicine Lecture - Endocrine Development

Historic Embryology - Endocrine
1903 Islets of Langerhans \| 1903 Pig Adrenal \| 1904 interstitial Cells \| 1908 Pancreas Different Species \| 1908 Pituitary \| 1908 Pituitary histology \| 1911 Rathke's pouch \| 1912 Suprarenal Bodies \| 1914 Suprarenal Organs \| 1915 Pharynx \| 1916 Thyroid \| 1918 Rabbit Hypophysis \| 1920 Adrenal \| 1935 Mammalian Hypophysis \| 1926 Human Hypophysis \| 1927 Adrenal \| 1927 Hypophyseal fossa \| 1930 Adrenal \| 1932 Pineal Gland and Cysts \| 1935 Hypophysis \| 1935 Pineal \| 1937 Pineal \| 1935 Parathyroid \| 1940 Adrenal \| 1941 Thyroid \| 1950 Thyroid Parathyroid Thymus \| 1957 Adrenal

| original Endocrine page

Objectives

Understand the main steps in the development of the thyroid, parathyroid, adrenal, pituitary, pineal glands, thymus and gonads.
Have a general understanding of the chief functions of these endocrine organs.
Understand the endocrine contribution to embryo development.
Understand the endocrine role of the placenta during development.
Have a general understanding of different types of hormones and their signaling actions.

Hormones

Steroid hormone receptor signaling^[3]

Hormone Types

Steroid biosynthesis pathway

Amino acid derivatives - noradrenaline (norepinepherine), adrenalin (epinepherine) , thyroid hormone
Proteins, peptides - thyroid stimulating hormone, leutenising hormone, follicle stimulating hormone
Steroids - androgens, glucocorticoids, mineralocorticoids

Hormone Actions

Autocrine - acts on self (extracellular fluid)
Paracrine - acts locally (extracellular fluid)
Endocrine - acts by secretion into blood stream (endocrine organs are richly vascularized)

Hormone Receptors

Hormones are recognised by either cell surface receptors (modified amino acids, peptides, proteins) or cytoplasmic/nuclear receptors (steroids).

MH - Interested in hormone history? Listen ABC Radio Ockham's Razor 2005-07-31 6.2 Mb mp3 Centenary of the word 'hormone', Sydney medical scientist and writer Dr John Carmody commemorates the centenary of the entry of the word 'hormone' into the English language.