UNSW Embryology

Beginnings, Growth and Development - Lecture Endocrine Development

© Dr Mark Hill (2007)

Acknowledgements

Introduction

This lecture covers Endocrine Development, note that a better understanding can be made if you understand the adult function of each endocrine organ (though this will not be covered in the Lecture). Use the links below to either view the Lecture slides (1/page) or print (4/page).

Endocrine development is sometimes divided into Neuroendocrine and Endocrine and is also generally covered piecemeal in all embryology textbooks, so you may have to look in several different chapters to find supporting textbook information.

You may also find interesting Prof JJ Carmody recent broadcast on the Centenary of the word 'hormone'. For a more detailed background on endocrine development see also Endocrine Development Notes.

Page Links: Introduction | Lecture Slides | iLecture Broadcast | Endocrine Podcast | Textbooks | Online Resources | Development Overview | Histology | Acronyms | Glossary |

Lecture Slides

The links below are to PDF versions of lecture slides. Note that movies shown in lecture will not run in these documents and are linked below.

BGDL33Endocrines View 1 slide/page (73 pages 1.7 Mb, note large size)

BGDL33Endocrines Print 4 slides/page (19 pages, 1.1 Mb)

iLecture Broadcast

The external link below is to the lecture iLecture 2005 broadcast of Endocrine Lecture (24 Aug 2005 - 09:00).

iLecture 33 Endocrine Development Broadcast.

Erratum: Please note error in audio when describing the region of Thyroid formation. In Lecture audio I have mistakenly used the term "median eminence" when I meant "hypopharyngeal eminence". Lets see if I make the same mistake again....

Note that Lecture starts 9:30 minutes into broadcast.

iLecture Audio Summary (timing minutes:seconds)

• 9:30 - Introduction, endocrine system, hormones, organs
• 18:50 - Pineal
• 21:50 - Hypothalamus
• 29:10 - Thyroid (see erratum above)
• 36:14 - Parathyroid
• 39:25 - Pancreas
• 50:30 - Adrenal
• 55:20 - Gonads
• 58:20 - Placenta

About UNSW iLecture : "The Pilot iLecture system will enable automatic audio recording and processing into a variety of streaming media formats." (both Quicktime and Windows Media are supported)

UNSW BGD Embryology Lectures (2005) Podcast

Listen to Dr Mark Hill 2005 Medicine BGD Lecture 2005-08-24 on Endocrine development. Copy and paste the URL link below into iTunes 4.9 "subscribe to podcast" (in the Advanced menu)

http://embryology.med.unsw.edu.au/Podcast/MHLecture/BGDEmbryology2005.xml

Alternatively, download the MP3 files: Introduction, endocrine system, hormones, organs (2.1 Mb) | Pineal (700 Kb) | Hypothalamus (700 Kb) | Thyroid (1.7 Mb) | Parathyroid (736 Kb) | Pancreas (2.5 Mb) | Adrenal (1.1 Mb) | Gonads (716 Kb) | Placenta (432 Kb)

Other embryology audio content is being made available at UNSW Embryology Podcast

Podcast - Listen ABC Radio Ockham's Razor 2005-07-31 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.

Slip this MP3 into your player and listen! 13 minutes 32seconds 6.2 Mb mp3

ABC Radio Ockham's Razor Transcript | ABC Radio Ockham's Razor | About Podcasts (Embryology MP3s)

Textbooks

Histology and Cell Biology Kierszenbaum, AL.

• Chapter 18 Neuroendocrine System pp477-497
• Chapter 19 Endocrine System pp499-527

Human Embryology (3rd ed.) Larson Chapter 9, 10, 12

The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud

• Chapter 10 pp230-233
• Chapter 12 pp280-282
• Chapter 13 pp319-347

Human Embryology Fitzgerald and Fitzgerald Chapter 24 pp166-167

Online Resources

UNSW Embryology: See the linked notes pages in the Development Overview listed below (these notes are in more detail than required for this current lecture) Pineal Development Notes | Pituitary Development Notes | Thyroid Development Notes | Parathyroid Development Notes | Thymus Development Notes | Pancreas Development Notes | Adrenal Development Notes | Endocrine Gonad Notes | Endocrine Placenta Notes | Endocrine Other Cells Notes

Online Textbooks

Endocrinology: An Integrated Approach table of Contents

NIH Genes & Disease Chapter 41

Colorado State University Pathophysiology of the Endocrine System (2000)

EndoText Endocrine System

Development Overview

Links: hypothalamus | Pineal | Pituitary | Thyroid | Parathyroid | Thymus |Pancreas | Pancreas | Gonads | Placenta | Maternal | Other Cells

hypothalamus Hypothalamus Development Notes

• Neuroectoderm – prosenecephalon
• Diencephalon – ventro-lateral wall intermediate zone proliferation
• Mamillary bodies - form pea-sized swellings ventral wall of hypothalamus

Pineal - Pineal Development Notes

• Neuroectoderm – prosenecephalon
• Week 10 - dorsal outpocket of diencephalon, median diverticulum, epiphysis
• Hollow diverticulum - cell proliferation to solid, pinealocytes (neuroglia), cone-shaped gland ("pine cone" shaped hence name), innervated by epithalmus
• diverticulum - walls thicken pineal recess open to 3rd ventricle
• neuroepithelial cells- 2 types pinealocytes, glial-like interstitial cells
• CNS meninges form capsule and connective tissue septa
• Melatonin- diurnal cycle, inhibits pituitary-gonad axis

Pituitary (Hypophysis, Greek hypo = under, physis = growth) - Pituitary Development Notes

• Ectoderm- ectoderm roof of stomodeum, neuroectoderm of diencephalon
• Adenohypophysis – anterior pituitary, glandular (pars anterior, pars intermedia, pars tuberalis)
• Neurohypophysis – posterior pituitary, nervous (pars nervosa)
• Week 4 – hypophysial pouch, Rathke’s pouch, diverticulum from roof
• Week 5 – elongation, contacts infundibulum, diverticulum of diencephalon
• Week 6 – connecting stalk between pouch and oral cavity degenerates
• Adenohypophysis
• Anterior wall proliferates - pars distalis
• Posterior wall little growth – pars intermedia
• Rostral growth around infundibular stem – pars tuberalis
• Neurohypophysis
• Infundibulum – median eminence, infundibulum, pars nervosa
• Week 10 – growth hormone and ACTH detectable
• Week 16 – adenohypophysis fully differentiated
• Week 20 to 24 – growth hormone levels peak, then decline

Thyroid - Thyroid Development Notes

• 24 days – thyroid median endodermal thickening in the floor of pharynx
• outpouch – thyroid diverticulum into hypopharyngeal eminence
• tongue grows, descend in neck – thryoglossal duct (proximal end foramen cecum of tongue)
• thyroid diverticulum – hollow then solid, right and left lobes, central isthmus
• pyramidal lobe – from isthmus (50% of people) attached to hyoid bone (distal end of thryoglossal duct)
• Week 11 – colloid appearance in thyroid follicles, iodine and thyroid hormone (TH) synthesis
• growth factors (insulin-like, epidermal) stimulates follicular growth
• Fetal TH - Initial secreted biologically inactivated by modification, late fetal secretion develops brown fat
• Iodine deficiency- during this period, leads to neurological defects
• Birth – TSH levels increase, thyroxine (T3) and T4 levels increase to 24 h, then 5-7 days postnatal decline to normal levels

Parathyroid Parathyroid Development Notes

• Third and Fourth Pharyngeal Pouches- endoderm (could also have ectoderm and neural crest)
• 3rd Pharyngeal Pouch – inferior parathyroid, initially descends with thymus
• 4th Pharyngeal Pouch – superior parathyroid
• Week 6 - diverticulum elongate, hollow then solid, dorsal cell proliferation
• Fetal parathyroids- respond to calcium levels, fetal calcium levels higher than maternal

Thymus - Thymus Development Notes

• Third Pharyngeal Pouch- endoderm
• Week 6 - diverticulum elongate, hollow then solid, ventral cell proliferation
• Thymic primordia- surrounded by neural crest mesenchyme
• Thymus development - epithelia/mesenchye interaction

Pancreas - Pancreas Development Notes

• Functions- exocrine (amylase, alpha-fetoprotein) and endocrine (pancreatic islets)
• Pancreatic buds- endoderm, covered in splanchnic mesoderm
• Pancreatic bud formation – duodenal level endoderm, splanchnic mesoderm forms dorsal and ventral mesentery, dorsal bud (larger, first), ventral bud (smaller, later)
• Duodenum growth/rotation – brings ventral and dorsal buds together, fusion of buds
• Pancreatic duct – ventral bud duct and distal part of dorsal bud, exocrine function
• Islet cells- cords of endodermal cells form ducts, which cells bud off to form islets
• Week 7 to 20 – pancreatic hormones secretion increases, small amount maternal insulin
• Week 10 – glucagon (alpha) differentiate first, somatostatin (delta), insulin (beta) cells differentiate, insulin secretion begins
• Week 15 – glucagon detectable in fetal plasma
• Beta cells - stimulate fetal growth, continue to proliferate through to postnatal in infancy, most abundant
• Maternal diabetes mellitus – hypertrophy of fetal beta cells, fetal abnormalities (More? Maternal diabetes mellitus

Adrenal (Suprarenal) - Adrenal Development Notes

• Cortex mesoderm, medulla neural crest
• Fetal and adult cortex
• Week 6 – fetal cortex forms from mesothelium adjacent to dorsal mesentery, medulla neural crest cells from adjacent sympathetic ganglia
• – adult cortex mesothelium mesenchyme encloses fetal cortex
• Late Fetal Period- differentiates to form cortical zones
• Birth - zona glomerulosa, zona fasiculata present
• Year 3 – zona reticularis present
• Fetal Cortex produces- a steriod precursor (DEA) converted by placenta into estrogen
• Adult Cortex produces – cortisol, etc..
• Adult Medulla produces – adrenalin (epinephrine), noradrenalin (norepinephrine)
• Fetal adrenal hormones - influence lung maturation

Gonads (Covered in Sexual Differentiation) - Endocrine Gonad Notes | Genital Development

• Gonad- mesoderm (mesothelium and underlying mesenchyme) and primordial germ cells
• Gonadal ridge – mesothelium thickening, medial mesonephros
• Primordial Germ cells- yolk sac, to mesentery of hindgut, to genital ridge of developing kidney
• Gonad differentiation - dependent on presence (testes) or absence (ovaries) of expression of testis-determining factor (TDF) from Y chromosome
• Testis
• 8 Weeks – mesenchyme, interstitial cells (of Leydig) secrete testosterone, androstenedione
• 8 to 12 Weeks - hCG stimulates testosterone production
• Sustentacular cells- produce anti-mullerian hormone to puberty
• Ovary
• X chromosome genes regulate ovary development

Placenta - Endocrine Placenta Notes | Placenta Development

• Maternal (decidua) and Fetal (trophoblastic cells, extraembryonic mesoderm) components
• Endocrine function- maternal and fetal precursors, synthesis and secretion
• Hormones- protein and steroidal
• Protein Hormones- chorionic gonadotropin (hCG), chorionic somatomammotropin (hCS) or placental lactogen (hPL), chorionic thyrotropin (hCT), chorionic corticotropin (hCACTH)
• Steroid Hormones- progesterone (maintains pregnancy), estrogens (fetal adrenal/placenta)
• hCG - up to 20 weeks, fetal adrenal cortex growth and maintenance
• hCS – rise through pregnancy, stimulates maternal metabolic processes, breast growth

Maternal

Maternal hormones - can cross the placental barrier, contribute precursors to placental hormone production.

Other Cells - Endocrine Other Cells Notes

Selected cells within the following organs also contribute to endocrine regulation. The development of their endocrine function is related to the development of the organ or tissue and their development will not be covered in the Lecture. The list below covers the types of hormones produced for more detail use the Endocrinology link.

Endocrinology: An Integrated Approach Cardiovascular and renal endocrinology

• Heart - Atrial natriuretic peptide, Endothelins
• Kidney
• Renin (Increase Angiotensin-aldosterone system)
• Prostaglandins (decrease Na+ reabsorption)
• Erythropoietin (Increase Erythrocyte (rbc) production), 1,25 (OH)2 vitamin D (Calcium homeostasis)
• Prekallikreins (Increase Kinin production)
• Digestive Tract
• Gastrin: from the stomach, control of gastric acid secretion
• Cholecystokinin: small intestinal hormone, stimulates secretion of pancreatic enzymes and bile
• Secretin: small intestinal hormone, stimulates secretion of a bicarbonate-rich fluids from the pancreas and liver
• Adipose Tissue - Endocrine Adipose Notes
• Leptin: polypeptide hormone produced in adipose and many other tissues with also many different roles
• Adiponectin: regulation of energy homeostasis and glucose and lipid metabolism, as well as acting as an anti-inflammatory on the cellular vascular wall
• Resistin: (for resistance to insulin, RETN) a 108 amino acid polypeptide and the related resistin-like protein-beta (Resistin-like molecule-beta, RELMbeta) stimulate endogenous glucose production

Histology

Blue Histology (UWA) Endocrines

Acronyms

Listed below are some common acronyms used in the endocrine system.

Acronymhormone full name (hormone type – source)

ACTH adrenocorticotropin or corticotropin (peptide – anterior pituitary)

ADH antidiuretic hormone (peptide – hypothalamus)

ANP atrial natriuretic factor (peptide – heart)

CT calcitonin (peptide - C cells of thyroid)

FSH follicle stimulating hormone (protein - pituitary)

GH growth hormone (peptide - pituitary)

LH lutenizing hormone (protein - pituitary)

MSH melaocyte stimulating hormone (peptide - pituitary)

PRL prolactin (peptide - pituitary)

PTH parathyroid hormone (peptide - parathyroid)

TH thyroid hormone (amino acid derivative - thyroid)

TSH thyroid stimulating hormone (pituitary - protein)

Glossary of Terms

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

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