The placenta is a temporary organ that develops during pregnancy to support the growth and development of the fetus. It has protective, vascular, and endocrine functions, including delivering nutrients and oxygen to the fetus and removing waste. The placenta is composed of the placental disc, which attaches to the uterine wall, the umbilical cord that connects to the fetus, and fetal membranes surrounding the fetus. At term, the placenta weighs 400-600 grams and is 15-25 centimeters in diameter. It exchanges gases, nutrients, and waste between the mother and developing fetus through chorionic villi in the placenta and maternal blood in the uterine wall.

1. FLASHPATH
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2. ANATOMY OF THE
PLACENTA
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3. GENERAL
• Placenta is a maternal-fetal organ that start developing following
implantation of blastocyst, and delivered with the fetus at birth
• Role of placenta:
– Protective function
• Encircle the fetus with amniotic sac (containing fluid)
• Attach the fetus to the uterine wall
– Vascular function
• Deliver nutrients, oxygen, and maternal antibodies to the fetus
• Remove waste products from the fetus
– Endocrine function
• Secret many hormones e.g. estrogen, progesterone, HCG

4. GENERAL
• The placenta formed of three parts:
–Placental disc
–Umbilical cord
–Fetal membranes
• The decidua share the maternal circulation with the placenta
Fetal
origin

5. PLACENTAL DISC
• Weight (at term):
– 400 – 600 gm
• Diameter (at term):
– 15 – 25 cm
• Thickness (at term):
– 1.5 – 3 cm
• Insertion (at the uterus)
– Commonly upper segment
– Commonly posterior wall
Before weighing the placenta, the disc should
be
“trimmed”  cord cut-off, membrane cut-off
“fresh”  not fixed by formalin (most weight
tables are based on fresh state)

6. PLACENTAL DISC
• Fetal surface
– Also called “chorionic plate”
– Covered by shiny, translucent membranes
• Fetal surface is light blue – pink
• Also showing radiating chorionic blood vessels
– Site of umbilical cord insertion
• Maternal surface:
– Also called “basal plate”
– Divided into 15 – 20, dark red lobules “cotyledons”
– Attached to the decidua basalis

7. UMBILICAL CORD
• Length (at term):
– 50 – 60 cm
• Diameter (at term):
– 1 – 3 cm
• Insertion (at the placenta)
– Chorionic plate (central / mildly eccentric)
• Cut section
– Two arteries (thick walled)
– One vein (thin walled)
– Wharton’s jelly (whitish – gelatinous)

8. UMBILICAL CORD
Twisting (coiling)
• Like the telephone cord
• Coiling index:
– Gross: total number of coils
total length of the cord
– Ultrasound: 1
intercoil distance (distance between two coils)
– Normal: 0.2 (+/- 0.1)
• One coil / 5 cm
• Up to three coils / 10 cm

9. FETAL MEMBRANES
• Forming the gestational sac
– Containing the fetus & amniotic fluid
• Features
– Smooth, glistening surface
• Layers
– Amnion (inner)
– Chorion (outer)
• Attachment (at the placenta)
– At the edges of the disc
The amnion reflects to cover the fetal
surface of the placental disc, and the outer
surface of umbilical cord

10. FETAL MEMBRANES
• Chorion Laeve (smooth)
– Free part
– Forming gestational sac (with amnion)
– No chorionic villi (atrophied)
• Chorion Frondosum (leaf-like)
– Embedded part in the placenta proper
– Forming chorionic plate
– Extending into chorionic villi

11. DECIDUA
• Endometrium of the pregnant uterus
– Contains maternal (endometrial) vessels
• Three parts
– Basalis: site of placental disc attachment
– Parietalis: lines of the rest of uterus
– Capsularis: covers the developing sac
• Eventually will fuse with the parietalis
in enlarged sac

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