Care of the Fetus during the Perinatal Period

• Embryonic stage of gestation - is the period after implantation during which all of the major organs and structures within the growing fetus are formed
• Placenta and Membranes

  • Serve as the fetal lungs, kidneys, and digestive tract in utero
  • Help to provide protection for the fetus, begins growth in early pregnancy in coordination with embryo growth
• After fertilization, the corpus luteum in the ovary continues to function rather than atrophying, because of the influence of human chorionic gonadotropin (hCG), a hormone secreted by the trophoblast cells.
• Endometrium - is now termed the Decidua (Latin word for “falling off”)because it will be discarded after the birth of the child.
• Decidua basalis – is the part of the endometrium that lies directly under the embryo or the portion where the trophoblast establish communication with the maternal blood vessels
• Trophoblast - are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta
• Blastocyst – is the stage that the human embryo reaches approximately 5-6 days after fertilization
• Decidua capsularis – the portion of the endometrium that encapsulates the surface of the trophoblast
• Decidua vera – is the remaining portion of the uterine lining.
• Chorionic Villi - once implantation is complete, trophoblastic layer of cells of the blastocyst begins to mature rapidly.
• 11th or 12th day - miniature villi that resemble probing fingers, termed chorionic villi, reach out from the single layer of cells into the uterine endometrium to begin formation of the placenta
• Syncytiotrophoblast (syncytial layer) – is the outer layer of cells that produces various placental hormones
• Cytotrophoblast or Langhan’s layer – the middle layer, present as early as 12 days gestation.
• Cytotrophoblast or Langhan’s layer

  • To protect the growing embryo and fetus from certain infectious organisms spirochete of Syphilis
  • This layer of cells disappears - between 20th and 24 wks
  • Passive antibody begins at 20th wks
• Syphilis - is not considered to have a high potential for fetal damage early in pregnancy, only after the point at which cytotrophoblast cells are no longer present The layer appears to offer little protection against viral infection
• Placenta – a flat, disc shaped organ that is highly vascular, forms in the upper segment of the endometrium of the uterus.
• Placenta - is responsible in the exchange of nutrients and gases between the fetus and the mother
• Placenta

  • 15-20 cm in diameter
  • Weight: 400g- 600g
  • 2-3 cm in depth
  • 30 Cotyledons
• Respiratory system – exchange of O2 and CO2 takes place in the placenta not in the fetal lungs.
• Circulatory system – fetal placental circulation takes place via the umbilical vein
• Renal system – waste products are excreted through the placenta.
• Nutrients pass to the fetus via the placenta
• 12th day of pregnancy - maternal blood begins to collect in the uterine endometrium sur rounding the chorionic villi.
• 4 days

  • Zygote cells known as Totipotent
  • Totipotent stem cells – are undifferentiated cells that can develop a human being
• After another 4 days:

  Totipotent cells become Pluripotent
• Pluripotent Stem cells – specific body cells (Nerve, Brain, or Skin cells
• Another few days the Pluripotent cells become Multipotent
• Multipotent cells - at the time of implantation, the blastocysts has two cavities in the inner structure (Amniotic cavity and Yolk sac)
• 2 cavities in the inner structure - Amniotic cavity & Yolk sac
• Yolk sac

  • supply nourishment only until implantation
  • Provide a source of RBC until the embryo can produce its own (12th wk.
• The Three Germ Layers

  • Ectoderm
  • Mesoderm
  • Endoderm
• Ectoderm – skin, nervous system and sense organ
• Mesoderm – musculoskeletal, circulatory and genitourinary
• PREGNANCY

  • the state of having a developing embryo or fetus within the body
  • state from conception to the delivery of the fetus
• Fetal Membranes - are membranes associated with the developing fetus.
• Amnion – inner layer of the fetal membrane
• Chorion – outermost membrane surrounding an embryo gives rise to the placent
• Umbilical cord – is about 53 cm. (21 inches) in length at term and about 2 cm. (0.75 in.) thick
• Umbilical cord – contains 2 arteries and one vein which are kept in place by the Wharton jelly
• WHARTON’S JELLY - a gelatinous substance which prevents pressure on the vein and arteries.