Placenta and Fetal Membranes Flashcards
What is the decidua basalis? Where is it located?
- the part of the endometrium that participates with the chorion in the formation of the placenta
- is at the site of implantation
What is the decidua capsularis? Where is it located?
- it grows over embryo in luminal side, encapsulating it
What is the decidua parietalis? Where is it located?
- membrane lining the main cavity of uterus everywhere other than at site of attachment of the chorion
- on the opposite uterine wall to basalis/capsularis
When does implantation normally occur?
Late second week, approximately 10 days post-fertilization
What does the trophoblast differentiate into? What are each layer?
- cytotrophoblast (inner layer)
- syncytiotrophoblast (outer layer)
What are signs and symptoms of an ectopic pregnancy? (4)
- abdominal pain
- amenorrhea
- vaginal bleeding
- rupture of oviduct wall
What is the chorionic sac comprised of? (3)
- extraembryonic somatic mesoderm
- cytotrophoblasts
- syncytiotrophoblasts
What is the amnion?
The thin, tough membrane that surrounds the embryo/fetus and amniotic fluid
How does the amnion develop?
amnioblasts separate from the epiblast and enclose the developing amniotic cavity
What is the purpose of amniotic fluid? (3)
- cushions fetus
- permits fetal movements
- regulates fetal body temperature
What is hydramnios? What can cause it? (3)
- excessive amniotic fluid
- a genetic defect
- fetal defect in CNS
- blockage of GI tube
What is oligohydramnios? What can cause it? (2)
- insufficient amniotic fluid
- placental abnormality
- maternal high blood pressure
What can oligohydramnios cause? Why?
- renal agenesis
- pulmonary hypoplasia
- Because decreased fluid doesn’t provide enough cushion to fetus and umbilical cord
What is the amniochorionic membrane?
fusion of the amniotic sac and chorionic sac that occurs when amniotic sac grows faster than the C.S.
What are the two components of the placenta?
- villous chorion (fetal part)
- decidual basalis (maternal part)
How is the smooth chorion formed?
chorion that is in contact with the decidua capsularis undergoes atrophy so that villi die and it becomes smooth
How do the chorionic villi attach to the decidua basalis?
Attach through the cytotrophoblastic shell
How is the placenta formed? (3)
- cytotrophoblasts (CTBs) of chorionic villi proliferate at chorionic plate
- CTB’s extend through syncytiotrophoblasts, forming cytotrophoblastic shell
- shell attaches to and erodes decidua basalis, creating intervillous space
What are cotyledons?
Irregular convex areas of villous chorion
What do cotyledons contain? (2)
- 2+ main stem villi
- multiple branch villi
What are main stem villi?
Villi that extend from the chorionic plate
What are branch villi? What is their purpose?
- Villi that extend from a main stem villus
- increase villus surface area
What is an anchoring villi?
Villi that attach to maternal tissues through cytotrophoblastic shell
What can cross the placenta? (6)
- nutrients
- hormones
- IgG antibodies (maternal defense for baby)
- waste products
- drugs
- infectious agents
What does not cross the placenta? (3)
- protein hormones
- bacteria
- drugs w/amino acid-like structures
What runs through the umbilical cord, vessel-wise? (2)
- two umbilical arteries (deoxygenated blood)
- one umbilical vein (oxygenated blood)
What is placenta previa?
When the placenta implants in the lower part of the uterus or in the cervix
What can placenta previa lead to?
Dangerous 3rd trimester bleeding
What is placenta accreta?
Partial or complete absence of the decidua
What can placenta accreta lead to? Why?
- Severe postpartum bleeding
- The villous chorion adheres directly to the myometrium and placenta fails to separate at birth
What is a hydatiform mole?
replacement of normal villi by dilated or hydropic translucent vesicles
What are hydatiform moles caused by?
polyspermy or duplication of a single sperm
What is a partial mole? what is it caused by?
- growth of tissue when a normal ovum fertilized by two sperm
What is a complete mole caused by? What tissue does it lack?
- When an empty egg is fertilized and contains only paternal DNA from either two sperm or duplication of a single sperm
- contains no fetal tissue
What is an invasive mole? How is it treated?
- A complete mole that penetrates or perforates the uterine wall
- Is responsive to chemotherapy
What is a gestational choriocarcinoma?
highly invasive metastatic tumor that arises from trophoblast
How is gestational choriocarcinoma diagnosed?
By seeing increasing hCG titer with no uterine enlargement
What is the treatment for gestational choriocarcinoma?
Combined chemotherapy agents
What are dizygotic twins?
Aka ‘fraternal twins’, they originate from two zygotes and have two separate implantations (so separate chorions and amnions
What are monozygotic twins?
Aka ‘identical twins’, they originate from one zygote, and can have variable membranes depending on when they divide
- the earlier they divide, the more separate the membranes and placentas will be!
How do monozygotic twins form, most often?
By division of the embryoblast of the blastocyst
