1. Fetal Membranes 2
Dr Rania Gabr

2. Objectives By the end of this lecture, the student should be able to:
Describe the structure, functions, anomalies of the placenta
Describe the structure, functions, anomalies of the umbilical cord

3. PLACENTA SHAPE: circular disc
WEIGHT: about one-sixth that of fetus ( gm)
DIAMETER: cm
THICKNESS: 2-3 cm
SURFACES:
1. Fetal surface:
smooth, transparent, covered by amnion with umbilical cord attached near its center & umbilical vessels radiating from it
2. Maternal surface:
irregular, divided into convex areas (cotyledons)

5. Each cotyledon contains 2 or more stem villi with their branch villi
PLACENTA
The fetal part of placenta is divided into cotyledons by projections from decidua basalis (placental septa)
Each cotyledon contains 2 or more stem villi with their branch villi
By the end of 4th month, decidua basalis is almost entirely replaced by cotyledons

7. PLACENTAL CIRCULATION
Poorly oxygenated blood leaves the fetus & passes through the 2 umbilical arteries to the placenta
Umbilical arteries divide into several chorionic arteries that enter chorionic villi
An arterio-capillary-venous network is formed in chorionic villi
Exchange of materials between fetal & maternal blood (in intervillous spaces) occurs across placental membrane (barrier)
Oxygenated blood returns to fetus by umbilical vein

9. Functions of the Placenta
Exchange of metabolic & gaseous products between maternal & fetal bloodstreams
Respiratory function: Exchange of gases –
Nutritive function: Exchange of nutrients & electrolytes –
Transmission of maternal antibodies –
Excretory function: Co2 and other stuff
Barrier function: prevents passage of some bacteria and some drugs from maternal to fetal blood.

10. Endocrine function: Production of hormones
Protein hormones:
Human chorionic gonadotropin (early pregnancy tests)
Human placental lactogen
Human chorionic thyrotropin
Human chorionic corticotropin
Relaxin
Steroid hormones:
Progesterone
Estrogen

11. Normally chorionic villi persist only at site of decidual basalis:
ANOMALIES OF PLACENTA
ANOMALIES IN SIZE & SHAPE:
Normally chorionic villi persist only at site of decidual basalis:
Placenta membranacea: a large thin membranous placenta due to persistence of functioning villi on the entire surface of chorionic sac
Accessory placenta: a patch of chorionic villi persisted a short distance from main placenta

12. ACCESSORY PLACENTA

13. PLACENTA PREVIA, ACCRETA & PERCRETA

14. ANOMALIES OF PLACENTA ANOMALIES IN POSITION:
Placenta previa: when blastocyst implants close to or overlying internal os of uterus late pregnancy bleeding
ANOMALIES IN EXTENSION:
Placenta accreta: chorionic villi extend to the myometrium
Placenta percreta: chorionic villi penetrate the whole thickness of myometrium & extend to perimetrium

15. ANOMALIES OF PLACENTA ANOMALIES IN ATTACHMENT OF UMBILICAL CORD:
Battledore placenta: the cord is attached to the margin of placenta
Velamentous insertion of cord: the cord is attached to the membranes surrounding placenta, umbilical vessels are liable to be ruptured

16. Velamentous insertion of cord
Battledore placenta
Velamentous insertion of cord

17. Umbilical Cord Cord like structure Connects fetus to the placenta
Attached to the ventral surface of the fetal body and to the smooth chorionic plate of the placenta

18. Umbilical Cord: Formation
Develops from the connecting stalk
The connecting stalk initially attached to the caudal end of the embryonic disc, after folding, becomes attached to the ventral surface of the curved embryonic disc, at the umbilical region
The umbilical region wider initially, becomes narrower as the folding progresses
The underlying structures are compressed together and form a cord like structure, the umbilical cord

19. Umbilical Cord: Formation cont’d
Initial contents:
Connecting stalk
Umbilical vessels
Allantois
Yolk sac
Extraembryonic celome
Intestinal loop (during 6-10 weeks)

20. Umbilical Cord: At Term
At term, the typical umbilical cord:
Is cm in length, with a diameter of cm
Has knotty appearance
Usually contains two arteries and one vein
Is surrounded by a jelly like substance called the Wharton's jelly
Is enclosed in amnion
amnion

21. Umbilical Cord: Placental Attachment
May attach to the placenta near its margin- Marginal attachment
Typically attaches to the placenta near its center- Eccentric attachment
placenta
May attach to the membranes around the placenta- Membranous (Velamentous ) attachment

22. Umbilical Cord cont’d
After delivery of the placenta the umbilical cord is usually clamped and severed
The site of its attachment leaves a scar, the navel (belly button), on the anterior wall of the abdomen

23. Abnormalities Related to Umbilical Cord
Omphalocele: Failure of returning of intestinal loops back into the abdominal cavity
Long cord may prolapse or coil around the fetus thus cause difficulty in labour
Short cord may result in premature pull and separation of placenta causing severe bleeding during birth
True knots
True knot
Prolapsed cord

24. Thank You & Good Luck