Placenta Development
Introduction
The placenta (Greek, plakuos = flat cake) named on the basis of this organs appearance. The placenta a mateno-fetal organ which begins developing at implantation of the blastocyst and is delivered with the fetus at birth.
During that 9 month period it provides nutrition, gas exchange, waste removal, endocrine and immune support for the developing fetus. (More? Placental Overview | Histology).
There are essentially 3 separate aortic/venous circulatory systems: umbilical, systemic and vitelline. The umbilical system is lost at birth, the vitelline contributes to the portal system and the systemic (embryonic) is extensively remodelled to fom the the cardiovascular system.
System Links: Introduction | Cardiovascular | Coelomic Cavity | Endocrine | Gastrointestinal Tract | Genital | Head | Immune | Integumentary | Musculoskeletal | Neural | Neural Crest | Placenta | Renal | Respiratory | Sensory | Birth |
Reading
- Human Embryology (2nd ed.) Larson Chapter 7 p151-188 Heart, Chapter 8 p189-228 Vasculature
- The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 14: p304-349
- Before we Are Born (5th ed.) Moore and Persaud Chapter 12; p241-254
- Essentials of Human Embryology Larson Chapter 7 p97-122 Heart, Chapter 8 p123-146 Vasculature
- Human Embryology Fitzgerald and Fitzgerald Chapter 13-17: p77-111
Placental Classification
Classification of placenta is on the basis of histological (microscopic) structural organization and layers between fetal and maternal circulation.
Three main groups:
- Haemochorial - placenta where the chorion comes in direct contact with maternal blood (human).
- Endotheliochorial - maternal endometrial blood vessels are bare to their endothelium and these comes in contact with the chorion (dogs, cats).
- Epitheliochorial - maternal epithelium of the uterus comes in contact with the chorion, considered as primitive (pigs, cows).
The presence of these three differing types of placenta have also been used to describe the pattern mammalian evolution.
Placental Cord Histology
- ==Placental Abnormalities==
- * '''Placenta Accreta''' - abnormal adherence, with absence of decidua basalis. The incidence of placenta accreta also significantly increases in women with previous cesarean section compared to those without a prior surgical delivery.
- * '''Placenta Increta''' - occurs when the placenta attaches deep into the uterine wall and penetrates into the uterine muscle, but does not penetrate the uterine serosa. Placenta increta accounts for approximately 15-17% of all cases.
- * '''Placenta Percreta''' - placental villi penetrate myometrium and through to uterine serosa.
- * '''Abruptio Placenta''' - a retroplacental blood clot formation, abnormal hemorrhage prior to delivery.
- ===Placental Cord Abnormalities===
- * '''Cord knotting''' - can also occur (1%) in most cases these knots have no effect, in some cases of severe knotting this can prevents the passage of placental blood.
- * '''Cord torsion''' - Rare event where even without knot formation can also affect placental blood flow, even leading to fetal demise.
- ===Placental Infections===
- ===Placental Pathology===
- '''MH -''' content in this section is not examinable.
- * Chronic Villitis - can occur following placental infection leading to maternal inflammation of the villous stroma, often with associated intervillositis. The inflammation can lead to disruption of blood flow and necrotic cell death.
- * Massive Chronic Intervillositis (MCI) - maternal blood-filled space is filled with CD68-positive histiocytes and an increase in fibrin, occuring more commonly in the first trimester.
- * Meconium Myonecrosis - prolonged meconium exposure leads to toxic death of myocytes of placental vessels (umbilical cord or chorionic plate).
- * Neuroblastoma - a fetal malignancy that leads to an enlarged placenta, with tumor cells in the fetal circulation and rarely in the chorionic villi.
- * Thrombophilias - (protein C or S deficiency, factor V Leiden, sickle cell disease, antiphospholipid antibody) can generate an increased fibrin/fibrinoid deposition in the maternal or intervillous space, this can trap and kill villi.
- ==References==
- ===Reviews===
- ===Articles===
- ===Search PubMed===
- Search April 2010
- * Placenta Development - All (10032) Review (1896) Free Full Text (2435)
- * Placental Development - All (9103) Review (1762) Free Full Text (2219)
- * Placental Membranes - All (10083) Review (748) Free Full Text (1728)
- ==Terms==
- * '''anastomosis''' - Term used to describe the connection between two tubes. Applied to describe the connection between peripheral blood vessels without an intervening capillary bed.
- * '''coelocentesis''' - A sampling of extracoelomic fluid usually for an early prenatal diagnostic technique.
- * '''cord knotting''' Term describing umbilical or placental cord knotting. This occurs in about 1% prevents the passage of placental blood, pseudoknots also occur usually with no effect.
- * '''cord prolapse''' - A term used to describe at birth the descent of the umbilical cord through the cervix alongside (occult) or past (overt) the presenting part in the presence of ruptured membranes (incidence of 0.1% to 0.6%).
- * '''decidua capsularis''' - The term given to the uterine endometrium which has been converted to decidua surrounding the conceptus on the smooth chorion side.
- * '''placentophagia''' - Term used to descrbe the maternal ingestion of afterbirth materials (placental membranes and amniotic fluid) that can occur following mammalian parturition (birth).
- ==Additional Images==
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- Fetal circulation overview.jpg
Fetal circulation overview
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Cite this page: Hill, M.A. (2024, April 18) Embryology Placenta Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Placenta_Development
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G