UNSW Embryology

Endocrine Development - Placenta

© Dr Mark Hill (2011)

Acknowledgements

Introduction

The placenta manufactures and secretes several hormones. A chief component is secretion of human chorionic gonadotrophin (hHCG). HCG has a role in the support of the corpus luteum within the ovary, and therefore the pregant state rather than menstrual. HCG is also the component detected in maternal urine in some pregnancy testing kits.

(See also Placenta and Fetal Membranes notes)

• Placental Endocrine
  • Human chorionic gonadotrophin (hCG)
    • like leutenizing hormone, supports corpus luteum
  • Human chorionic somatommotropin (hCS)
    • or placental lactogen
    • stimulate mammary development
  • Human chorionic thyrotropin (hCT)
  • Human chorionic corticotropin (hCACTH)
  • progesterone and estrogens
    • support maternal endometrium
  • relaxin

Some Recent Findings

Reading

• Human Embryology (2nd ed.) Larson
• The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Ch10: p230-233, Ch12: p280-282, Ch13: p319-347
• Before We Are Born (5th ed.) Moore and Persaud
• Essentials of Human Embryology Larson
• Human Embryology Fitzgerald and Fitzgerald Ch24: p166-167
• Search PubMed- Medline

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.

Learning activities

• Examine the developing thyroid, adrenal and pituitary glands in the stage 13/14 and stage 22 embryos.
• Review the vascular and nerve supply of the above glands.
• Review the development of the parathyroid and pineal glands.
• Review the endocrine role of the placenta. (see below)
• Review the development and endocrine function of the gonads.

Computer Activities

UNSW Embryology:

• Stage 13/14 Embryo
• Stage 22 Embryo
• Selected Sections Stage 22 Embryo
• Abnormal Endocrine Development
• Overview Pituitary Development
• Overview Thyroid Development
• Overview Adrenal Development
• Overview of Pancreas Development See also GIT Notes- Pancreas

Human Embryology Movies:

Embryo Images Unit:

Requires Internet connection

• Pituitary Gland

Video

Development Overview

Parathyroid and Thymus

• Endoderm of 3,4,5 pharyngeal pouches form dorsal and ventral cell masses.
• Dorsal 3rd and 4th pouch form parathyroid.
• Ventral cells move medially to form thymus.

The ectoderm endoderm boundary in the pharynx forms 2 glands.

Thyroid

• The boundary endoderm in the floor region forms a pocket that separates from the surface and forms the thyroid.

Pituitary Gland (see Pituitary Development)

• The boundary epitheilal ectoderm in the roof of the pharynx forms a pocket (Rathke's pouch) that comes into contact with the ectoderm of developing brain.
• The anterior pituitary originates from the epitheilal ectoderm.
• The posterior pituitary originates from the brain neuroectoderm.

 Adrenal Gland

• Neural crest cells migrate toward the coelomic cavity wall and form the adrenal medulla.
• Overlying epithelial cells proliferate and form a capsule that will form the adrenal cortex.

Pineal

• Site of synthesis of melatonin
  • light sensitive in lower vertebrates (lost evloutionarily)

Pancreas

• Site of synthesis of insulin and glucagon.

• Selected Research Reviews
  • Adrenal
• Selected Research Articles
  • Pituitary
  • Adrenal

Development Terms

• adenohypophysis- anterior pituitary= 3 parts pars distalis, pars intermedia, pars tuberalis
• lamina terminalis- anterior region of brain where cranial neuropore closes.
• pars- (L. part of)
• pharynx- uppermost end of GIT, beginning at the buccopharyngeal membrane and at the level of the pharyngeal arches.
• Rathke's pouch- a portion of the roof of the pharynx pushes upward towards the floor of the brain forming the anterior pituirary (adenohypophysis, pars distalis, pars tuberalis pars intermedia). Where it meets a portion of the brain pushing downward forming the posterior pituitary (neurohypophysis, pars nervosa). Rathke's pouch eventually looses its connection with the pharynx.
  • [Martin Heinrich Rathke 1973-1860, embryologist and anatomist]

Glossary of Terms

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Quick Links

Development Notes ----------------- Menstrual Cycle Week 1 Week 2 Week 3 Week 4 Placenta Serial Images Molecular Dev Abnormal Dev Postnatal Dev Notes Index

System Notes ----------------- All Systems Heart/Cardiovascular Respiratory Coelomic cavity Gastrointestinal Tract Head and Neck Neural Neural Crest Eye Ear Nose Endocrine Renal Genital Musculoskeletal Integumentary

Movies ----------------- Movies Quicktime Flash Audio Week 1 Week 2 Week 3 Stage 13 Stage 22 Neural Heart Gastrointestinal Renal Genital Other Embryos

Other Embryos ----------------- All Animals Chicken Fly Frog Mouse Rabbit Rat Worm Zebrafish Guinea Pig

UNSW Embryology ISBN: 978 0 7334 2609 4

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