UNSW Embryology

Coelomic Cavity Development

© Dr Mark Hill (2008)

Acknowledgements

Introduction

The intraembryonic coelom is the primitive cavity that lies within the developing embryo that will form the 3 major body cavities: pericardial, pleural, peritoneal. The coelom forms very early in embryogenesis and is much later paritioned inferiorly by the diaphragm and pleuroperitoneal membrane; and superiorly initially by the pleuropericardial fold between the heart and lungs.

The intraembryonic coelom communicated through coelomic portals (at the level of midgut herniation) with the extraembryonic coelom.

All cavities are fluid filled and developing organs push against a wall of the cavity, generating a double coat (serosal/adventital) surrounding an organ (for example the lungs). The serous membrane is the epithelium (squamous) and its associated underlying loose connective tissue.

Stage 22 Embryo (Human)

In the human embryo, the separation of the three cavities of coelom is complete. D1-7&E1-4 : The pericardial cavity. Dl-7, E1-7: The pleural cavity, almost the same frames, indicating the nearby equal extent of the two cavities at this stage, but also that eventually the pleural cavities will become much larger. E3-7: The diaphragm can be seen as a thin, distinct membrane around the liver. Two derivatives of the coelomic epithelium are to be observed here. E6-7, F1-3: The adrenal glands. Notice the large fetal cortex, (most of the gland) and the narrow (more compact and darker staining) early permanent cortex encapsulating it. F1-3: The spleen develops in the dorsal mesogastrium and appears as a dense body on it lateral to the left adrenal gland and kidney. Review in Endocrine Development. F3-7, G1: The gonads are also in part derivatives of the coelomic epithelium but they will be discussed with the rest of the genital system. G4-5: The caudal extent of the peritoneal cavity; this appears as the rectovesical pouch in the male or as the rectouterine pouch in the female.

 

Reading

• Human Embryology (2nd ed.) Larson
  • Ch6 p127-146
• The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud
  • Ch9: p174-184
• Before we Are Born (5th ed.) Moore and Persaud
  • Ch10 p181-195
• Essentials of Human Embryology Larson
  • Ch6 p81-93
• Human Embryology Fitzgerald and Fitzgerald
  • Ch5 p29-32, Ch7 p47,48
• Additional References
• Search PubMed- Medline

Objectives

• Describe the development of the intra- and extra-embryonic coeloms.
• Describe the processes involved in the development of the three divisions of the intra-embryonic coelom; pericardium, pleural cavities and peritoneum.
• Describe the fate of the extra embryonic coelom.
• Describe the development of the diaphragm.

Learning activities

• Review the development of the 3-layered embryo, with particular reference to the antero-posterior and lateral folding processes.
• Examine the 6mm pig and 27mm human embryo microfiche cards identifying the main features of the developing coelom.
• Identify the diaphragm in the 27mm human embryo and relate this to the development of the diaphragm.
• Discuss the developmental anomalies associated with the formation of the diaphragm.

Computer Activities

UNSW Embryology: Pig coelom sections (st13/14) | Human coelom sections (st22) | Selected Human highpower (st22)

Human Embryology Movies:

Embryo Images Unit: Body Cavities (Early Week 4) | Body Cavities (Late Week 4)

Development Overview

Cartoon of the intraembryonic coelom forming in the lateral plate mesoderm

Extraembryonic Coelom cavity surrounding the developing embryo	coelomic portals transient communication between extra/intracoelom	Intraembryonic Coelom horseshoe shaped structure forms 3 main cavities	Neural Tube
		percardial cavity	Ventricular space
		L/R pleural cavities	Spinal canal
		peritoneal cavity	(not part of this section) (see neural dev notes)

Mesothelia

The epithelial covering of coelomic organs and also line their cavities.

Contribute to the vasculature of the heart and the intestinal tract. Undergo epithelial-mesenchymal transition (EMT), migration, and differentiation into endothelial cells, vascular smooth muscle cells, and pericytes.

Development Terms

• atresia- obstruction.
• eppiglottis- develops from hypobrachial eminence.
• fistula- abnormal comunication.
• hypopharyngeal eminence- fusion of 3rd pharyngeal arches, precursor of root of tongue.
• laryngotracheal groove- forms on anterior (ventral) wall of pharynx, gives rise to larynx, trachea, respiratory tree.
• larynx- lining from endoderm, cartilage from pharyngeal arch 4 and 6.
• lung buds- primordia of lungs.
• parietal pleura-outer lining of pleural cavity derived from epithelia of pericardioperitoneal canals from intraembryonic coelom.
• pleural cavity- walls derived from pericardioperitoneal canals -> intraembryonic coelom ->coelomic spaces -> lateral mesoderm -> mesoderm.
• pleuropericardial fold- restricts the communication between pleural cavity and pericardiac cavity, contains cardinal vein and phrenic nerve.
• pleuroperitoneal membrane- forms inferiorly at transverse septum to separate peritoneum from pleural cavity.
• septum transversum- mesoderm separating thoracic cavity and yolk sac, forms central tendon of diaphragm (and some of liver?).
• stenosis- narrowing
• surfactant- a detergent secreted by Type 2 alveolar cells between alveolar epithelium. Functions to lower surface tension, allowing lungs to remain inflated.
• visceral pleura- inner lining of pleural cavity derived from contact epithelia with lung bud of pericardioperitoneal canals from intraembryonic coelom.

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

Quick Links

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

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

Movies ----------------- Embryo Growth Ultrasound Week 1 Week 2 Week 3 Week 4 Stage 13/14 Stage 22 Neural Head and Neck Heart Vasculature Gastrointestinal Urogenital Other Embryos Larsen Internet

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

UNSW Embryology ISBN: 978 0 7334 2609 4

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