Types Of Placenta Flashcards
Types of placenta Based on degree of intimacy:
- Non deciduous placenta
- Deciduous Placenta
- Contra deciduous placenta
Types of placenta Based on types of implantation:
- Superficial Placenta
- Eccentric Placenta
- Interstitial Placenta
Types of placenta Based on distribution of chorionic villi:
- Diffused Placenta
- Cotyledonary Placenta
- Zonary Placenta
- Discoidal Placenta
- Meta discoidal placenta
Types of placenta Based on degree of involvement of foetal
and maternal tissues:
- Epitheliochorial Placenta
- Syndesmochorial Placenta
- Endotheliochorial Placenta
- Haemochorial Placenta
- Haemoendothelial Placenta
● Superficial implantation
● The blastocyst lies in the uterine cavity.
● During the attachment with the uterine wall, the blastocyst surface generates finger like projections called chorionic villi, that, penetrate into the uterine wall,and are loosely united.
● The chorionic villi are simply
withdrawn from the uterine wall.
Non deciduous placenta or Semi placenta
● ‘Decidua’ means ‘to shed’
● Implantation is more intimate.
● The chorionic villi are complicated, branched and intimately connected with the endometrium.
● At birth, uterine tissue is also pulled out with the shedding of blood.
Deciduous placenta or Placenta Vera
● The implantation is intimate but both maternal tissue as well as foetal portion of placenta get torn off and are absorbed by mother’s leucocytes.
● Found in Perameles and T alpa (mole).
Contra deciduous placenta
● Embryo is superficially attached with the uterine wall.
● The embryo remains within the lumen of the uterus.
Superficial or Central placenta
● Embryo lies within the uterine epithelial fold.
● Later, the epithelial fold encloses the embryo almost completely.
Eccentric placenta
● Embryo burrows into the uterine mucosa below the epithelium and becomes surrounded completely by the endometrial tissue of the uterus.
Interstitial placenta
● Chorionic villi are numerous and are uniformly scattered over the chorion.
Diffused placenta
● Chorionic villi are aggregated in
certain regions to form small tufts.
● The remaining part of the chorion smooth. surface remains
Cotyledonary placenta
● Chorionic villi are developed in form of a belt or a band around the middle of the embryo.
Zonary placenta
● Chorionic villi are arranged in a circular plate on the dorsal surface of embryo.
Discoidal placenta
● Chorionic villi are at first scattered all over the chorion but later becomes restricted to one or two discs.
Metadiscoidal placenta
● Involves 6 tissue barriers between the foetal and maternal circulation.
1. Maternal endometrial epithelium
2. Maternal connective tissue
3. Maternal blood vessel endothelium
4. Fetal chorion
5. Fetal connective tissue
6. Fetal blood vessel endothelium
Epitheliochorial placenta
● Involves 5 tissue barriers between the foetal and maternal circulation.
1. Maternal connective tissue (no epithelium)
2. Maternal blood vessel endothelium
3. Fetal chorion
4. Fetal connective tissue
5. Fetal blood vessel endothelium
● Found in sheep, giraffe, deer etc.
Syndesmochorial placenta
● Involves 4 tissue barriers between the
foetal and maternal circulation.
1. Maternal blood vessel
endothelium
2. Fetal chorion
3. Fetal connective tissue
4. Fetal blood vessel
endothelium
● Found in cat, dog, bear etc.
Endotheliochorial placenta
● Involves 3 tissue barriers between the foetal and maternal circulation.
1. Maternal blood (in direct contact with fetal chorion)
2. Fetal chorion
3. Fetal connective tissue
4. Fetal blood vessel endothelium
● Chorionic epithelium is bathed directly in the maternal blood.
● Found in primate, bat, mole, shrew etc.
Haemochorial placenta
● Involves only a single tissue barrier between the foetal and maternal circulation.
● Foetal blood vessel is bathed directly in the maternal blood.
● Found in rabbit, mouse, rat, guinea-pig etc.
Haemoendothelial placenta
