development + some hormones

• 3 types of stimuli

  • hormonal
  • humoral
  • neural
• Hormonal is the most common type of stimuli
• Organs involved in endocrine system

  • hypothalamus
  • pituitary
  • pineal glands
  • thyroid
  • parathyroid
  • adrenal
  • pancreas
  • gonads
• Hormonal


  Hormones travel through the blood and trigger other hormones
• Humoral


  Changes in ions/nutrients (blood) trigger hormones
• Neural


  Nerve synapses trigger hormones
• Hormones produced by organs

  • Posterior pituitary: oxytocin & anti-diuretic hormone
  • Anterior pituitary: growth hormone, ACTH, prolactin, FSH, LH, TSH
  • Thyroid/parathyroid: calcitonin, thyroid stimulating hormone
  • Thymus: thymosin
  • Adrenal: cortisol, sex hormones, epinephrine & noepinephrine
  • Pineal: melatonin
  • Pancreas: insulin, glucagon
  • Gonads: sex hormones, sperm, eggs
• Pancreas: endocrine (blood sugar) and exocrine (digestive) functions
• Down syndrome is trisomy 21, leading to mental developmental issues
• Chromosomal abnormalities


  • Down syndrome (trisomy 21)
  • Triple X (female)
  • Turner syndrome (female)
  • Klinefelter (male)
• Gestation period


  Last menstrual period - birth
• Pregnancy

  Fertilization - birth
• Embryonic period


  Fertilization - week 8
• Zygote


  Developing offspring after fertilization
• Fertilization

  Oocyte released from ovary -> covered in protective layers -> sperm penetrates layers -> fusion of sperm and egg plasma membranes -> only sperm head nucleus enters oocyte -> oocyte undergoes changes to prevent more sperm
• Syngamy


  Completion of fertilization -> zygote formed -> maternal and paternal DNA mix -> readies for mitosis
• Embryonic development


  Series of mitotic divisions -> cells split quickly without growing -> forms tissues
• Blastulation


  Morula keeps dividing -> surpasses 100 cells -> begins to hollow out -> blastocyst forms with trophoblast and inner cell mass
• Implantation


  Blastocyst attaches to endometrium on day 7 -> secretes HCG
• Gastrulation


  Inner cell mass forms 2 layers: epiblast and hypoblast -> primary yolk sac forms
• Germ layers formation

  Bilaminar disc becomes trilaminar -> ectoderm, mesoderm, endoderm form
• Neurulation


  Ectoderm cells in primitive streak fold inwards -> forms neural tube -> central nervous system
• Organogenesis


  Development of all organs takes place from week 3 to week 8
• Placental development

  Chorionic villi form -> combine with uterine tissue -> umbilical cord develops -> placenta fully functioning by week 3
• Fetal development

  Head dominant but body elongating, brain still gets bigger -> facial features, sensory organs, bones distinct -> fetal position, increase in weight
• mesoderm: the middle layer of cells or tissues of an embryo; muscles, and bone and heart.
• endoderm: the innermost layer of cells or tissue of an embryo in early development; becomes digestive and respiratory systems
• ectoderm: the outermost layer of cells or tissue of an embryo in early development; epidermis and nervous system