Human Development - Continuous process from fertilization until death.

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Human Development - Continuous process from
fertilization until death.
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• I. Prenatal Development - Changes that occur
  prior to birth.
• A. Fertilization - union of oocyte (egg) with
  sperm.
• Only 1 sperm can fertilization an oocyte.
• 3 days prior to ovulation to 1 day afterwards.
• Sperm uses hyaluronidase (enzyme), which is
  released from the head (acrosome), to penetrate
  the oocyte.
• Oocyte two layers
• Corona Radiata - outer layer
• Zona Pellucida - inner layer

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• B. Embryonic Period - First 8 week
• Stage Day
• Morula 1 3 12-16 cells
• Blastocyte 3 - 6 Trophoblast - placenta
• Inner cell Mass stem cells,
• Implanatation 7-14 Trophoblasts contacts the
  endometrium
• Amniotic Cavity embryo (ectoderm, endoderm)
• Chorion 14-21 Forms the placenta
• Amnion 14-21 Envelops the embryo in the amniotic
  cavity
• Gastula 21 Primitive Streak - mesoderm by
  gastrulation
• Neurula 21 Notochord grows out of mesoderm
  cells from primitive streak -
  Neuralation.

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Formation of the germ layers
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Neural Tube Crest Formation
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Maternal Changes
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• Weeks
• Body development 3 - 8
• Recognizable human by a series of folds.
• Foregut - Head cavity
• Hindgut - Tail cavity
• Midgut - Alimentary canal

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• 3rd - Week
• Placenta development
• Chronic villi - finger like projections of the
  placenta that invades the endometrium.
• Lacunae - maternal blood in the endometrium
• Placental Blood barrier - Prevents mixing of
  embryonic maternal blood.
• HCG- causes corpus letum to remain functional
  (continue production of progestron estrogen
  until it go produce its own around 3 months).

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• 4-5 Weeks
• Organogenesis - development of major organs.
• Arise from out pockets

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• C. Growth of the Fetus
• Fetus 8 wks until birth
• Start of bone ossification
• Organs function
• Covered by lanugo - fine, soft hair
• Accumulation of fat for insulation nutrient
  reserve.
• Slough of epithelial cells that protect the
  fetus from wastes that may be found in the
  amniotic fluid.

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• 36 wks - able to live outside the mother
• 38 wks - full term, lost lanugo, but still
  covered by waxy coat.
• 2.5 g - 3500 g
• 0.01 ounce - 7 pounds, 11 ounces Mitosis
• 1 inch - 20 inches

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• II Parturition - Process of giving birth
• Prior to birth
• Placenta releases estrogen which cause minor
  uterine contractions (Braxton-Hicks
  contractions).
• Increase in frequency as nearing full term.
• Prepares the myometrium for power full
  contractions necessary for birth.
• Stretching of the uterus sends a signal to the
  hypothalmus.
• Posterior pituitary releases oxytocin which
  targets the myometrium.
• Increase contractions which begins labor.

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• B. First Stage Early
• Contractions pushes fetus against the cervix.
• Amniotic sac breaks releases fluid.
• Contraction continues which dilates the cervical
  canal (positive feedback).
• Contractions increase in intensity until cervix
  is 10 cm.
• Last up to 24 hrs.

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• C. Second Stage
• Maximum dilations to deliver the fetus.
• Abdominal contractions are added.
• 1 min to 1 hr.
• D. Third stage - After birth
• Placenta separates from the uterine wall
  (bleeding).
• Estrogen progesterone levels drop
  dramatically.
• Menstrual flow begins 8-12 wks later.

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• III Postnatal Development - Birth until Death.
• A. Lacation - Production of milk by the mammary
  glands.
• Begins at paturition may last up to 2/3 years
  (regular suckling).
• Plancenta - estrogen progestrone stimulate
  the ducts in the breast
• Accumulation of fat
• Prolactin is present during pregnancy, but its
  effects are overwhelm by the high levels of
  estrogen progestrone.
• Once placenta leaves the body (lower levels of
  estrogne progestrone), the effect of prolactin
  is felt (increase in milk production).
• Colostrum is produced for the first few days
  which is high in antibodies low in fat
  lactose.
• Afterwards, antibodies levels drop, fat
  lactose levels increase.

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• B. Flow of milk requires nerve stimulation.
• 1. Suckling triggers nerve impulse to release
  oxytocin.
• 2. Oxytocin cause cells to contract milk (milk
  let down).
• 3. Suckling, crying, anticipation of schedule
  feeding.
• 4. Continues as long as nursing continues, will
  stop after several days of non -nursing.

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5 Stages in Life
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Respiratory Circulatory changes
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• C. Stages of Life - Males 73, females 77
• 1. Infancy (1-2 yrs ) neonate
• a. Circulatory changes in first few breaths
  takes up to YEAR to complete.
• 1. Foramen ovale is closed off forms the
  fossa ovalis, 4 chambered heart.
• Increase in blood pressure in the left
  atrium decrease in blood pressure in the
  right atrium.
• 2. Ductus Arteriosus closes off.
• Blood flows to lungs as they expand.
• 3. Umbilical cord - cut tied, blood goes to
  the vena cava.
• b. Rapid bone growth.
• c. Rapid muscle growth.
• d. First birthday, standing walking.

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• 2. Childhood (infancy to puberty)
• Respond to the world around them.
• Slower growth.
• Fat is lost.
• Synapse forms in the brain.
• Learns new information at the very high rate.
• Head grows slower than the rest of the body.

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• 3. Adolescence
• male 10-12 - 18yr
• female 8-11 16
• a. Physiological changes
• Sex hormones
• Reproductive organs reaches maturity.
• Secondary sex characteristics develop.
• Growth spurt
• Males max. height is reach 18 - 19 yrs. old.
• Female max. height is reached 16 - 17 yrs old.

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• 4. Adulthood- longest
• Lack of vertical growth.
• Slow effect of aging builds up.
• Increases fat deposits.
• Gradual muscle loss.
• Decrease in metabolism.
• Thinning of the skin.
• Diet, physiological stress can effect health.

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• 5. Senescene - old age
• 65- 75
• Increased in fragility
• Loss of posture
• Muscle of atrophy
• Slow nerve impulses
• Skin becomes thin, heavily pigmented.
• Immune response decreases, pneumia, tumurs,
  infections

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• 6. Death
• All body functions stops
• Failure of 1 or more organs