View source for Medicine:Decidua

{{Short description|Part of uterus modified in pregnancy}}
{{Infobox anatomy
| Name        = Decidua
| Latin       =
| Image       = Gray33.png
| Caption     = Diagrammatic sections of the uterine mucous membrane: A. The non-pregnant uterus. B. ''Decidua parietalis''; the mucous membrane in the pregnant uterus and not beneath the placenta.
| Image2      = Gray34.png
| Caption2    = Sectional plan of the gravid uterus in the third and fourth month
| System      =
}}

The '''decidua''' is the modified [[Biology:Mucous membrane|mucosal lining]] of the [[Biology:Uterus|uterus]] (that is, modified endometrium) that forms every month, in preparation for [[Medicine:Pregnancy|pregnancy]]. It is shed off each month when there is no fertilised egg to support.<ref name="MW1">{{cite web |title=Definition of DECIDUA |url=https://www.merriam-webster.com/dictionary/decidua |website=www.merriam-webster.com |access-date=25 October 2022 |language=en}}</ref> The decidua is under the influence of [[Chemistry:Progesterone|progesterone]]. Endometrial cells become highly characteristic. The decidua forms the maternal part of the [[Biology:Placenta|placenta]] and remains for the duration of the pregnancy.  After birth the decidua is shed together with the placenta.<ref name="MW1"/>

==Structure==
The part of the decidua that interacts with the [[Biology:Trophoblast|trophoblast]] is the '''''decidua basalis''''' (also called '''''decidua placentalis'''''), while the '''''decidua capsularis''''' grows over the [[Biology:Embryo|embryo]] on the luminal side, enclosing it into the endometrium. The remainder of the decidua is termed the '''''decidua parietalis''''' or '''''decidua vera''''', and it will fuse with the decidua capsularis by the fourth month of gestation.

Three morphologically distinct layers of the decidua basalis can then be described:
* Compact outer layer ('''''stratum compactum''''')
* Intermediate layer ('''''stratum spongiosum''''')
* Boundary layer adjacent to the myometrium ('''''stratum basalis''''')
Within the decidua, occasional fibrinoid deposits form where the syncytiotrophoblast is damaged. The region of fibrinoid deposition where trophoblasts meet the compact portion of the decidua basalis is called '''''Rohr's layer''''', while the fibrinoid deposits that occur between the compact and spongy layer of the decidua basalis is termed '''Nitabuch's layer''' (for Raissa Nitabuch). This layer is absent in [[Medicine:Placenta accreta|placenta accreta]].<ref>{{cite book|title=Williams obstetrics|publisher=McGraw-Hill Professional|year=2005|isbn=9780071413152|editor-last=Cunningham|editor-first=F. Gary|edition=22nd|location=New York; Toronto}}</ref>[[File:Endometrium ocp use3.jpg|thumb|right|[[Micrograph|Micrograph]] of decidualized endometrium due to exogenous progesterone. H&E stain.]]
The decidua has a [[Biology:Histology|histologically]]-distinct appearance, displaying large polygonal [[Biology:Decidual cells|decidual cells]] in the stroma. These are enlarged endometrial stromal cells, which resemble [[Biology:Epithelium|epithelium]] (and are referred to as "epithelioid").

Decidualization includes the process of differentiation of the spindle-shape stromal fibroblasts into the plump secretory decidual cells, which create a pericellular extracellular matrix rich in fibronectin and laminin (similar to epithelial cells).

Vascularity, as well as vascular permeability, is enhanced in the decidualizing endometrium.

Its leukocyte population is distinct, with the presence of large endometrial granular leukocytes being predominant, while polynuclear leukocytes and [[Biology:B cell|B cell]]s are scant.

The large granular lymphocytes ([[Biology:Neural cell adhesion molecule|CD56]] bright) are called [[Biology:Uterine natural killer cells|uterine natural killer cells]]| (uNK cells).

==Development==
After ovulation, in placental mammals, the endometrial lining becomes hypertrophic and vascular under the influence of the [[Biology:Sex hormone|sex hormone]]s, [[Biology:Estrogen|estrogen]] and [[Chemistry:Progesterone|progesterone]].

In animals exhibiting hemochorial placentation, the endometrium undergoes decidualization following [[Biology:Implantation (human embryo)|implantation]]. If implantation does not occur, the secretory lining will be absorbed (estrous cycle) or shed ([[Medicine:Menstrual cycle|menstrual cycle]]).

The decidua is shed with the placenta during [[Biology:Birth|birth]].

==Function==
As the maternal interface to the embryo the decidua participates in the exchanges of nutrition, gas, and waste with the gestation. It also protects the pregnancy from the maternal [[Biology:Immune system|immune system]]. Further, the decidua has to allow a very controlled invasion of the trophoblast.

In invasive placental disorders like [[Medicine:Placenta accreta|placenta accreta]] decidualization have been consistently found to be deficient.

===Hormone production===
The decidua secretes hormones, [[Biology:Growth factor|growth factor]]s, and [[Biology:Cytokine|cytokine]]s. It has receptors for [[Biology:Estrogen|estrogen]], [[Chemistry:Progesterone|progesterone]], [[Biology:Growth hormone|growth hormone]], and others.

Among its products are hormones commonly associated with other organs such as [[Chemistry:Cortisol|cortisol]], [[Biology:Corticotropin-releasing hormone|CRF]], GnRH, [[Biology:Prolactin|prolactin]], and [[Biology:Relaxin|relaxin]]. Decidual prolactin is not under [[Biology:Dopamine|dopamine]]rgic control.

Insulin-like growth factor-binding protein 1 (IGFBP1) also called placental protein 12, and [[Biology:PAEP|PAEP]] (glycodelin) appear to be specific products of the secretory and decidual lining.

Other factors released include interleukin-15 and [[Biology:Vascular endothelial growth factor|vascular endothelial growth factor]] (VEGF). A reasonable understanding of the role and interplay of these hormones and factors has not been evolved.

===Other===
[[File:Decidua in a lymph node - very high mag.jpg|thumb|right|[[Micrograph|Micrograph]] of decidua in a lymph node. H&E stain.]]
*In case of an [[Medicine:Ectopic pregnancy|ectopic pregnancy]], the endometrium nevertheless becomes decidualized. A woman may shed the lining in the form of a decidual cast, which may be mistaken as a [[Medicine:Miscarriage|miscarriage]], when, in fact, the ectopic pregnancy still persists.
*A decidual reaction can be observed in tissue of the peritoneum and [[Biology:Ovary|ovary]] during a pregnancy, and represents a response of stromal tissue to [[Chemistry:Progesterone|progesterone]].
*Decidua in a [[Biology:Lymph node|lymph node]] may mimic [[Medicine:Metastasis|metastatic]] [[Medicine:Carcinoma|carcinoma]].<ref name=pmid15859655>{{Cite journal  | last1 = Wu | first1 = DC. | last2 = Hirschowitz | first2 = S. | last3 = Natarajan | first3 = S. | title = Ectopic decidua of pelvic lymph nodes: a potential diagnostic pitfall | journal = Arch Pathol Lab Med | volume = 129 | issue = 5 | pages = e117–20 |date=May 2005 | doi = 10.5858/2005-129-e117-EDOPLN | pmid = 15859655 }}</ref>

==Clinical significance==
A long-lasting [[Medicine:Infection|infection]] of the decidua, [[Medicine:Chronic deciduitis|chronic deciduitis]], is associated with [[Medicine:Preterm birth|pre-term labour]].<ref name=pmid18171100>{{Cite journal  | last1 = Edmondson | first1 = N. | last2 = Bocking | first2 = A. | last3 = Machin | first3 = G. | last4 = Rizek | first4 = R. | last5 = Watson | first5 = C. | last6 = Keating | first6 = S. | title = The prevalence of chronic deciduitis in cases of preterm labor without clinical chorioamnionitis | journal = Pediatr Dev Pathol | volume = 12 | issue = 1 | pages = 16–21 | year =  2009| doi = 10.2350/07-04-0270.1 | pmid = 18171100 | s2cid = 25693917 }}</ref>
<gallery>
File:Chronic deciduitis - intermed mag.jpg|[[Micrograph]] of [[Medicine:Chronic deciduitis|chronic deciduitis]]. H&E stain.
File:Histopathology of acute choriodeciduitis.jpg|Acute choriodeciduitis, with [[Biology:Neutrophil|neutrophil]]s seen in the chorion and decidua.
</gallery>

==History==
The word comes {{ety|la|deciduus|falling off / shedding}}.

==Additional images==
<gallery>
File:Gray39.png|Scheme of placental circulation.
File:Gross pathology of fetal membranes versus decidua.jpg|Gross pathology of fetal membranes versus decidua
</gallery>

==References==
{{Reflist}}

==External links==
* {{URL|http://www-medlib.med.utah.edu/WebPath/PLACHTML/PLAC094.html|Histologic picture at med.utah.edu}}
* {{BUHistology|19904loa}}

{{Extraembryonic and fetal membranes}}

[[Category:Obstetrics]]

{{Sourceattribution|Decidua}}