Anatomy & Physiology II – Human Development (Ch. 28)

Vocabulary flashcards covering key terms from fertilization, early embryonic development, implantation, hormonal regulation of pregnancy, labor stages, and related clinical concepts.

Fertilization

Fusion of one haploid sperm nucleus with one haploid oocyte nucleus to create a diploid zygote.

Capacitation (Priming)

Series of functional changes a sperm undergoes in the female tract that enable it to fertilize an oocyte.

Acrosomal Reaction

Release of digestive enzymes from the sperm’s acrosome that penetrates the zona pellucida of the oocyte.

Zona Pellucida

Glycoprotein layer surrounding the oocyte that sperm must penetrate for fertilization.

Fast Block to Polyspermy

Instant depolarization of the oocyte membrane via Na⁺ influx preventing additional sperm entry.

Slow Block (Cortical Reaction)

Release of cortical granules that destroy sperm receptors and create a physical barrier to further sperm.

Zygote

Diploid cell formed after fusion of sperm and ovum nuclei; first cell of the new individual.

Cleavage

Series of rapid mitotic divisions of the zygote without overall growth, forming smaller blastomeres.

Morula

Solid ball of about 16 cells produced by cleavage; precedes the blastocyst stage.

Blastocyst

Hollow ball of ~70–100 cells with an inner cell mass and trophoblast; stage that implants in uterus.

Trophoblast

Outer cell layer of the blastocyst that contributes to extra-embryonic tissues, including placenta.

Inner Cell Mass

Cluster of cells inside the blastocyst that develops into the embryo proper.

Totipotent Cells

Early embryonic cells able to form both embryo and extra-embryonic tissues; can produce identical twins if split.

Pluripotent Cells

Cells (in inner cell mass) capable of forming all body cell types but not extra-embryonic tissues.

Multipotent Cells

Cells whose potential is restricted to specific lineages; appear after the third embryonic week.

Gastrulation

Process that forms the three primary germ layers—ectoderm, mesoderm, and endoderm—from the inner cell mass.

Ectoderm

Outer germ layer that forms skin and nervous system, including brain and spinal cord.

Mesoderm

Middle germ layer that gives rise to muscle, bone, blood, heart, and most other organs.

Endoderm

Inner germ layer that develops into digestive tract, respiratory epithelium, and associated organs.

Monozygotic Twins

Identical twins produced when one zygote splits into two embryos during totipotent stages.

Dizygotic Twins

Fraternal twins resulting from fertilization of two separate oocytes by two sperm.

Implantation

Embedding of the blastocyst into the uterine endometrium, normally 6–8 days post-fertilization.

Human Chorionic Gonadotropin (hCG)

Hormone secreted by trophoblast that rescues the corpus luteum and is detected by pregnancy tests.

Ectopic Pregnancy

Implantation of the embryo outside the uterine cavity, most commonly in the uterine tube.

Placenta Previa

Condition where the placenta covers the cervical os, risking hemorrhage at birth.

Embryogenesis

First 3–8 weeks of development when germ layers form and rudimentary organs begin.

Organogenesis

Formation of rudimentary structures of all major organs by the end of the 8th week.

Fetal Development

Period from week 9 to birth characterized by growth and maturation of organ systems.

Sexual Differentiation

Process between weeks 9–12 in which male or female genitalia develop.

Placenta

Temporary organ derived from trophoblast and endometrium that exchanges nutrients, gases, and hormones between mother and fetus.

Corpus Luteum

Ovarian structure that secretes progesterone and estrogen early in pregnancy until the placenta takes over.

Estrogen (Pregnancy)

Hormone that rises 30-fold, suppresses FSH/LH, promotes fetal growth, and stimulates uterine and mammary tissue enlargement.

Progesterone (Pregnancy)

Hormone that suppresses FSH/LH and uterine contractions; falls late in pregnancy to permit labor.

Relaxin

Hormone from corpus luteum and placenta that increases ligament elasticity and dilates the cervix before childbirth.

Thyrotropin (TSH) in Pregnancy

Anterior pituitary hormone that elevates maternal thyroid activity, boosting metabolic rate.

Prolactin

Anterior pituitary hormone that enlarges mammary glands and readies them for milk production.

Adrenocorticotropic Hormone (ACTH)

Anterior pituitary hormone that raises maternal cortisol to aid fetal protein synthesis.

Parathyroid Hormone (PTH)

Hormone that mobilizes maternal calcium for fetal bone development.

Stage 1: Dilation

First stage of labor in which the cervix dilates to >10 cm and the amniotic sac often ruptures.

Stage 2: Expulsion (Presentation)

Second stage of labor involving delivery of the infant from full cervical dilation to birth.

Stage 3: Afterbirth

Final stage of labor when the placenta and membranes detach and are expelled.

In Vitro Fertilization (IVF)

Assisted reproduction technique in which eggs and sperm combine in a dish; resulting zygote is implanted into the uterus.