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Pregnancy & Development - Anatomy & Physiology

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  • What is fertilization?

    Fertilization is the joining of two haploid gametes (ovum and sperm) to form a diploid zygote with 46 chromosomes.

  • Define cleavage in embryonic development.

    Cleavage is a sequence of rapid cell divisions of the zygote that ends when the embryo contacts the uterine wall.

  • What is implantation and when does it occur?

    Implantation is the adhesion of the blastocyst to the uterine wall, occurring about day 7 after ovulation (around day 21 of the menstrual cycle).

  • What is the syncytial trophoblast and its function?

    The syncytial trophoblast is the outer layer of the trophoblast that burrows into the endometrium by producing hyaluronic acid to break down the membrane.

  • What are the three germ layers formed during gastrulation?

    The three germ layers are ectoderm, mesoderm, and endoderm, which give rise to different tissues and organs.

  • Which systems develop from the ectoderm?

    The ectoderm forms the integumentary, digestive, respiratory, and nervous systems.

  • What systems arise from the mesoderm?

    The mesoderm forms muscular, skeletal, lymphatic, cardiovascular, urinary, reproductive, and endocrine systems.

  • What does the endoderm develop into?

    The endoderm forms the inner linings of the digestive, respiratory, urinary bladder, and reproductive systems (including gametes).

  • What is neurulation?

    Neurulation is the embryological process that forms the central nervous system from the ectoderm.

  • When does organogenesis occur and what happens?

    Organogenesis occurs around week 4 when organs begin to form and limb buds appear; the embryo is about 5 mm long.

  • Difference between embryo and fetus stages?

    Embryo stage is from 0 to 3 months; fetus stage is from 3 to 9 months of development.

  • What is the role of the corpus luteum in pregnancy?

    The corpus luteum produces progesterone during the first trimester to maintain the endometrium until the placenta takes over.

  • Name the extra-embryonic membranes and their functions.

    Yolk sac: first site of blood cell formation.
    Amnion: produces amniotic fluid for cushioning.
    Allantois: forms urinary bladder.
    Chorion: surrounds amnion and forms placenta projections.

  • What is the function of the placenta?

    The placenta supplies oxygen and nutrients to the fetus and removes CO2 and waste products.

  • What hormone does the placenta produce to maintain pregnancy?

    Human Chorionic Gonadotropin (HCG) is produced by the syncytial trophoblast to maintain the corpus luteum during the first 3 months.

  • Describe the three stages of labor.

    Dilation: cervix dilates (8-14 hours).
    Expulsion: birth of baby (~45 minutes).
    Placental: delivery of placenta (20-40 minutes after birth).

  • What hormones are involved in labor?

    Oxytocin: stimulates uterine contractions.
    Prostaglandins: cause smooth muscle contraction.
    Relaxin: softens ligaments for delivery.

  • What is placenta previa and its risk?

    Placenta previa is when the placenta implants low in the uterus, blocking the birth canal, risking placental abruption and requiring C-section.

  • What are the components of the umbilical cord?

    The umbilical cord contains two umbilical arteries carrying deoxygenated blood from fetus to placenta and one umbilical vein carrying oxygenated blood to fetus.

  • What is the decidua basalis?

    The decidua basalis is the portion of the endometrium beneath the placenta that supports fetal development.