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Fertilization to Fetal Development Overview

May 15, 2025

Development Review Worksheet Key

I. Process of Fertilization

  • Fertilization: Union of the nucleus of egg and sperm.
  • Location: Occurs in the fallopian (uterine) tube.
  • Chromosomes in Gametes: 23 (haploid).
  • Chromosomes in Fertilized Egg: 46 (diploid).

II. Embryonic Development

Section 2: Definitions

  • Zygote: Fertilized egg, first cell of a new individual, single diploid cell.
  • Embryo: Earliest developmental stage from the first cell division (zygote) to about 8/10 weeks.
  • Fetus: From about eight weeks GA (10 weeks from LMP) until birth.

Section 3: Early Embryonic Events

  • Event A: Sperm penetration (fertilization).
  • Resulting Cell from Event A: Zygote.
  • Process B: Cleavage.
  • Embryonic Structure B1: Blastocyst.
  • Completed Process C: Implantation.

Diagram Labels:

  • Blastocyst
    • Cleavage
    • Fertilization
    • Gastrula
    • Implantation
    • Morula
    • Zygote

Section 4: Derivative Structures from Embryonic Layers

Ectoderm

  • Epidermis of skin, hair, nails, skin glands, sense receptors, inner ear, cornea, lens of eye, tooth enamel.
  • Central nervous system (brain and spinal cord), epithelium of pineal and pituitary glands.

Mesoderm

  • Notochord, skeletal system, muscular system, circulatory and lymphatic systems, excretory system, reproductive system.

Endoderm

  • Epithelial lining of digestive and respiratory systems, liver, pancreas, thyroid, parathyroids, thymus.

III. Fetal Development

Section 5: Fetal Development Events

  • Labor: Culmination of pregnancy with birth of newborn infants from uterus.

Section 7: Phases of Parturition (Labor)

  1. Dilation: Beginning of labor until full cervical dilation (~10 cm); longest phase.
  2. Expulsion: Full dilation to delivery; baby moves through cervix and vagina (birth).
  3. Placental: Expulsion of placenta; follows delivery.

Section 8: Labor Feedback Loop

  • Type: Positive feedback loop.
  • Initial Stimulus: Infant head putting pressure on cervix.
  • Oxytocin: Increases.
  • Uterine Contractions: Increase.
  • Stop Event: Baby born; no longer pressure against cervix.

IV. Additional Concepts

Section 9: Stem Cell Descriptions

  • Stem Cells: Master cells; building blocks of organ tissue, blood, and immune system.
  • Pluripotent: Differentiate into all derivatives of three primary germ layers.
  • Multipotent: Produce limited number of cell types, such as blood stem cells.
  • Bone Marrow Stem Cells: Multipotent stem cells in bone marrow.
  • Cord Blood: Multipotent blood remaining in placenta and umbilical cord.

Section 10: STD and Disease/Disorder Descriptions

  • Breast Cancer: Leading cause of cancer death in women; starts in mammary tissues.
  • Gonorrhea: Bacteria causing painful urination in men, often asymptomatic in women.
  • Human Papilloma Virus (HPV): Most common STI; can cause genital warts and increase cervical cancer risk.
  • Ovarian Cancer: Begins in female organs that produce eggs.
  • Syphilis: Bacteria causing painless sore, leading to rash and potentially serious complications.
  • Prostate Cancer: Occurs in prostate, wraps around urethra.
  • Genital Herpes: Virus causing genital sores, fever, and increased cervical cancer risk.
  • Testicular Cancer: Most common cancer in young men; occurs in seminiferous tubules.
  • Chlamydia: Bacteria causing painful urination and intercourse, discharge.