fertilization
what happens at conception?
define: gametes and zygote
- sperm penetrates the ovum
- gametes: sex cells that contain 23 unpaired chromosomes
- zygote: the sperm and ovum combine their gametes to form 23 pairs of a new cell
- prenatal or gestation is the process that transforms
what are the stages of prenatal development?
define: cephalocaudal pattern and proximodistal pattern
germinal, embryonic, fetal
- cephalocaudal pattern: development that proceeds from the head downward,, babies first learn how to support their own head
- proximodistal pattern: development that happens from the middle of the body outward,, spine-> internal organs-> arms and legs -> toes and fingers
stages of prenatal development
describe the germinal stage
what happens?
- from fertilization- 2 weeks
- shortest stage
- when the cells specialize and cell divison happens rapidly
- day 5: becomes a blastocyst
- day 12: blastocyst implants in the uterine tissue
- placenta: specialized organ exchanges nutrients from mother to baby
- umbilical cord: organ that connects the embryo to the placenta
- amnion: fluid-filled sac in which the fetus floats util just before it is born
stages of prenatal development
describe the embryonic stage
what becomes from the endoderm, mesoderm and ectoderm
- end of week 2- 8 weeks
- zygote is now called an embryo
- organogenesis: organ development
- gonads: sex glands develop ovaries and testes in week 6
- neurons: neural tube is form and develops the brain and spinal cord by week 4
- endoderm: digestive sys, liver, pancreas, lungs (inner layers)
- mesoderm: circulatory sys, lungs (epithelial layers), skeletal syst, muscular sys
- ectoderm: hair, nails, skin, nervous sys
stages of prenatal development
describe the fetal stage
what are the milestones of the fetal stage?
- end of week 8- birth
- formally starts when differentiation and refinement of major organs has occurred
- now called a fetus
- viability: ability of the fetus to survive outside the womb
9-12: fingerprints, grasping reflex, facial expressions, swallowing, breathing, peeing
13-16: hair follicals, response to sound
17-20: fetal movements,
21-24: vernix protects skin, lungs produce surfactant, most born dont survive
25-28: recgonition of mothers voice, good chance of survival
29-32: rapid growth
33-36: movement to head-down position for birth, lungs mature
Fetal stage
what happens to the brain during the fetal stage?
define: neuronal proliferation
- pace of neural formation picks up dramatically b/w the 10th and 19th weeks
- b/w the 13th and 21st weeks, newly formed neurons migrate to the parts of the brain where they will reside for the rest of the individual’s life
- once at the final destination within the fetal brain, the neurons begin to develop connections, called synapses
Prenatal development and capabilities
Vision
- eyelids closed until 26th week but sensitive to light weeks 17-20, can visually track
- fetus will respond to light with increase heartrate
prenatal capabilites
touch
- is the first sense to develop at 8 weeks
- first area to display sensitivity to touch is the perioral region (around the mouth)
- by 32 weeks, all of the fetus displays sensitivity to touch
ex. can see when one twins touches the other, they respond
mother touching the womb
prenatal capabilities
taset and smell
taste
- amniotic fluid contains a variety of flavours from the mother
- fetus likely tastes, taste buds look developed when born and most likely has a sweet tooth; shows purposeful behaviour to sweetness with the study of amniotic fluid dyed and with sacchride
- mother can pass on food preferences, eg. carrot study where mother drank carrot juice and babies prefer carrot juice later on
smell
- amniotic fluid takes on odours from mother’s food
- opportunity for odour receptor stimulation
- mother can pass down smell preferences
prenatal capabilites
hearing
- plentiful internal and external sounds
- memory for sounds is possible, study with 2 stories, child sucks on the pacifer more when they hear the story from a teddy bear read by their mothers voice, muffled
- mother’s voice is special
- likes the rhythm
what are the differences in prenatal development and behaviour?
male vs female and the stable individual differences
- females: grow more slowly and advance more rapidly in skeletal development which persists through childhood and early adolescence, more responsive to sound
- males: more responsive to touch
- behaviour in the womb can continue out the womb
causes of developmental deviation
list the genetic disorders
define: autosomal and sex-linked
- autosomal: caused by genes located on chromosomes other than sex chrm
- sex-linked: genes(mostly recessive) are found on the X chromosome
- autosomal dominant disorders: huntington’s, hbp, extra fingers, migraine/ headaches, schizophrenia
- autosomal recessive: phenylketonuria, sickle-cell, cystic fibrosis, tay-sachs, kidney cysts in infants, albinism
- sex-linked: hemophilia, missing front teeth. diabetes, muscular dystrophy
causes of developmental deviation
what are some chromosmal errors
define: trisomy
- trisomy: condition in which a child has three copies of a specific autosome
- trisomy 21: down-syndrome
- Klinefelters: XXY
- Turner’s: XO
causes of developmental deviation
what are some teratogen and what affect does it have on the development of the baby?
- tetrogens: agents or conditions that can cause congenital abnormalities
- eg) maternal diseases, drugs, mutagenic, environmental and epimutagenic, paternal influence
- the greatest risk from most teratogens is in the first eight weeks of gestation where most organ systems are developing rapidly
mutagens: cause changes (mutations in genomic DNA
environmental teratogens: damage cells or disrupt normal cell development
epimutagenic teratogens: cause abnormal gene silencing or expression
