embryology

• Where does fertilization usually occur in the female reproductive system?

  Distal portion of the fallopian tube
• What is the role of the acrosome in spermatozoa?

  To digest outer cells of the ovum
• What are the stages of parental development?

  • Germination period: first 2 weeks, primitive germinal layers form
  • Embryonic period: 2nd to 8th week, organ systems develop
  • Foetal period: last 30 weeks, organs mature for survival
• What is the germinal period?

  First 14 days post fertilization
• What happens during the first cleavage of the zygote?

  The zygote divides to form 2 cells
• Where does early development usually take place?

  In the fallopian tube
• What risk arises if there is prior damage to the fallopian tube?

  The early conceptus can become marooned
• What is an ectopic pregnancy?

  Implantation occurs in the fallopian tube
• What is a morula?

  A solid ball of 12 or more cells
• What forms the blastocoel in the blastocyst?

  Cells migrate from the center to the periphery
• What are the two major regions of the blastocyst?

  The trophoblast and inner cell mass
• What does the trophoblast develop into?

  The placenta
• When does the blastocyst arrive in the uterus?

  Around day 5-7
• What does progesterone stimulate during implantation?

  Production of sticky mucus called 'uterine milk'
• What is the purpose of uterine milk?

  Provides nutrition to the blastocyst
• What can happen during the implantation process?

  Rupturing of blood vessels may occur
• What happens to the inner cell mass during the late germinal period?

  It thickens and differentiates into two layers
• What are the two layers formed from the inner cell mass?

  Ectoderm and endoderm
• What occurs during the embryonic period?

  Organ systems develop from the germ layers
• What is organogenesis?

  Formation of body organs
• When are all organ systems recognizable?

  By the 8th week
• What organ systems develop from the germinal layers?

  • Ectoderm: nervous system, epidermis
  • Mesoderm: skeletal system, muscles, dermis, reproductive, urinary, cardiovascular systems
  • Endoderm: GI tract, epithelial linings, respiratory system
• What is neurulation?

  First event of organogenesis forming CNS
• What happens to the ectoderm during neurulation?

  It thickens to form the neural plate
• What forms the neural tube?

  Neural plate folds inward and fuses
• What does the anterior end of the neural tube become?

  The brain
• What is required for the closure of the neural tube?

  Adequate levels of folic acid
• What can result from failure of the neural tube to close?

  Spina bifida, a congenital defect
• What are the types of birth defects?

  • Genetic: inherited, predictable ratios
  • Congenital: developmental, unpredictable causes
• What is spina bifida?

  Failure of closure of the neural tube
• What happens if the anterior portion of the neural tube doesn’t fuse?

  The brain cannot develop properly
• How is anencephaly defined?

  Absence of cranial vault
• How is anencephaly detected?

  Early in pregnancy via ultrasound scans
• What is spina bifida occulta?

  Neural tube closes but vertebrae fail to close
• What is meningocoele?

  Meninges herniated through vertebrae spaces
• What is myelomeningocele?

  Most serious form of spina bifida
• What is hydrocephalus?

  Accumulation of cerebrospinal fluid in the brain
• What are teratogens?

  Environmental factors causing birth defects
• What is cytomegalovirus (CMV)?

  A virus transmitted by sexual contact
• What are the effects of alcohol on fetal development?

  Causes fetal alcohol syndrome and effects