Prof. Saeed Makarem

1
PLACENTA

• By
• Prof. Saeed Makarem

2
PLACENTA

• This is a fetomaternal organ.
• It has two components
• Fetal part develops from the chorionic sac
• Maternal part derived from the endometrium
• The placenta and the umbilical cord are a
  transport system for substances between the
  mother and the fetus.
• Function Of The Placenta
• Protection.
• Nutrition.
• Respiration.
• Excretion.
• Hormone production, (progesterone,estrogen,Gonadot
  rophins

3
DECIDUA

• DEFINITION
• It is the functional layer of endometrium of the
  gravid (pregnant) uterus.
• It includes the endometrium of fundus body of
  uterus
• The endometrium of the cervix does not form a
  part of decidua.

4
DECIDUA

• CAUSE OF FORMATION
• Trophoblast secretes chorionic gonadotrophins
  which prolong the life of corpus luteum
• The corpus luteum of pregnancy continues to
  secrete progesterone till the 20th week
• The increasing level of progesterone in maternal
  blood induces changes in the endometrial into
  decidua

5
DECIDUA

• STEPS OF FORMATION (DECIDUAL REACTION)
• The endometrium becomes thicker more vascular
• The endometrial glands become full of secretion
• The connective tissue cells enlarge due to
  accumulation of lipid glycogen.
• They are called decidual cells

6
DECIDUA

• Decidua basalis It lies at the site of
  implantation ,it forms the maternal part of the
  placenta
• Decidua capsularis it covers the conceptus
• Decidua parietalis the rest of the endometrium
  that lines the body the fundus.

7
DEVELOPMENT OF PLACENTA

• Until the beginning of the 8th week, the entire
  chorionic sac is covered with villi, (C).
• As the chorionic sac grows, only the part that is
  associated with Decidua basalis retain its villi,
  (D).
• Villi of Decidua capsularis compressed by the
  developing sac.
• Thus, two types of chorion are formed
• Chorion frondosum (villous chorion)
• Chorion laeve bare (smooth) chorion

8
DEVELOPMENT OF PLACENTA

• The villous chorion will form the fetal part of
  the placenta.
• The decidua basalis will form the maternal part
  of the placenta.
• The placenta will grow rapidly.
• By the end of the 4th month, the decidua basalis
  is almost entirely replaced by the cotyledons.

9
DEVELOPMENT OF PLACENTA

1. FETAL PART VILLOUS CHORION
2. MATERNAL PART DECIDUA BASALIS

10
PRIMARY CHORIONIC VILLI
At the end of 2nd week, finger-like processes
formed of outer syncytiotrophoblast inner
cytotrophoblast appear
11
SECONDARY CHORIONIC VILLI
Early in 3rd week, extraembryonic mesoderm
extends inside the villi
12
TERTIARY CHORIONIC VILLI
During 3rd week, arterioles, venules
capillaries develop in the mesenchyme of villi
join umbilical vessels By the end of 3rd week,
embryonic blood begins to flow slowly through
capillaries in chorionic villi
13
(No Transcript)
14
PLACENTA

• MATERNAL SURFACE
• Irregular, divided into convex areas
  (cotyledons)
• FETAL SURFACE smooth, transparent, covered by
  amnion with umbilical cord attached near its
  center umbilical vessels radiating from it

15
FULL-TERM PLACENTA

• Cotyledons about 15 to 20 slightly bulging
  villous areas. Their surface is covered by shreds
  of decidua basalis from the uterine wall.
• After birth, the placenta is always carefully
  inspected for missing cotyledons.
• Cotyledons remaining attached to the uterine wall
  after birth may cause severe bleeding.

Maternal side
16
FULL-TERM PLACENTA(500 -600 gm- Diameter 15-20
cm)

• Fetal surface
• This side is smooth and shiny. It is covered by
  amnion.
• The umbilical cord is attached close to the
  center of the placenta.
• The umbilical vessels radiate from the umbilical
  cord.
• They branch on the fetal surface to form
  chorionic vessels.
• They enter the chorionic villi to form
  arteriocapillary-venous system.

Fetal side
17
PLACENTAL CIRCULATION
18
STRUCTURE OF STEM CHORIONIC VILLUS
19
PLACENTAL MEMBRANE

• This is a composite structure that separating the
  fetal blood from the maternal blood.
• It has four layers
• Syncytiotrophoblast
• Cytotrophoblast
• Connective tissue of villus
• Endothelium of fetal capillaries
• After the 20th week, the cytotrophoblastic cells
  disappear and the placental membrane consists
  only of three layers.

20
It separates fetal from maternal blood. It
prevents mixing of them. It is an incomplete
barrier as it only prevents large molecules to
pass ( heparin bacteria) But cannot prevents
passage of viruses(e.g. rubella),
micro-organisms(toxoplama, treponema pallidum)
drugs and hormones.
21
TRANSFER ACROSS THE PLACENTAL MEMBRANE
22
Anomalies of Placenta
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26

• BATTLEDORE PLACENTA
• VELAMENTOUS INSERTION OF CORD

27
FULL-TERM UMBILICAL CORD

• Usually it is attached near the center of the
  fetal surface of placenta.
• Length about 50 cm
• Diameter 1-2 cm
• Contains two arteries and one vein, surrounded by
  mucoid connective tissue (Wharton jelly)
• The vessels are longer than the cord and may have
  loops (false knots).