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41 Cards in this Set

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direct development
-humans undergo this process where the offspring is born as miniature (but sexually immature) version of adult, and does not change dramatically as the body grows and matures
embryonic membranes
4 membranes that protect and nourish the embryo
chorion
-outermost embryonic membrane
-forms the fetal part of the placenta
-surface for gaseous(CO2/O2), nutrient and waste exchange
amnion
-sac around embryo
-keeps embryo enclosed in fluid (amniotic fluid)
allantois
-forms blood vessels of umbilical cord
-carries blood between embryo and placenta
yolk sac
-forms part of umbilical cord and digestive tract
-membranes sac with very little yolk, but forms blood cells
cleavage
(1st step in embryo formation)
-mitotic divisions of fertilized egg
-egg does not yet increase in size
-egg cell is considered a large cell at first
-cell size is reduced-gene regulation substances get distributed to various cells
-cytoplasm is split into smaller and smaller cells
-morula is formed-embryo becomes a solid mass of cells (spherical)
-continues until blastula is formed
zygote
fertilized egg after 1st cell division
blastula
(in humans-a blastocyst)
-embryo consists of a hollow ball with an outter layer of cells
blastocoel
space inside the blastocyst/blastula
Gastrulation
(2nd step in embyro formation)
process where the blastula develops into gastrula: 3-layered embryo

cells then move through the blastopore to form 3 layers
Blastopore
(an indentation)
forms on one side of blastula
endoderm
innermost layer of embryonic tissue

develops into digestive, resp. system, liver and pancreas
ectoderm
outermost layer of embryonic tissue

develops into hair and epidermis, nervous system and glands
mesoderm
middle layer of embryonic tissue
-formed from cells that migrate between ectoderm and endoderm, mesoderm is last to develop
-develop into muscles, skeletal system, circulatory system, sex organs
-kidneys, dermis, outer lining of resp. & digestive systems
-notochord
notochord
firm, flexible, found in vertebrates
Organogenesis
the 3 layers of tissue develop into organs
-excess cells die(tail, webbed hands & feet)
-genetic & environmental factors regulate growth & development of sex organs & sexual maturity
-each differentiated cell in organism contains all the genetic info needed to develop entire organism
Differentiation
specialization of embryonic cells into different types of cells(muscles, nerves, epithelials)
-in any given type of cells the particular combination of genes that are transcribed determine the shape, structure, function of cells
-the transcription of these genes is controlled by regulatory proteins such as hormones
Human Development: In 4 days
egg is fertized in oviduct, then travels to uterus
Human Development: Week 1 to 2
-blastocyst forms
-contains inner cell mass
-implantation
-outer layer of cells helps form placenta
-gastrulation occurs
blastocyst
hollow ball of cells
inner cell mass
cluster of cells that develops into embryo
implantation
outer wall of blastocyst is sticky, so it adheres to uterus and burrows into the uterine wall to obtain nutrients
placenta
-structure formed by combination of uterine lining and embryonic membrane
-allows the selectie exchange of materials between mother and baby
-secretes estrogen-stimulates growth of uterus & mammory glangs
-secretes progesterone-stimulates mammory glands and prevents uterine contractions
Fetal Alcohol Syndrome
alcohol can pass through the placenta and enter the baby's blood stream
-smaller brain
-inhibited growth
Embryonic disc
double layer of cells that separates the two fluid-filled sacs
-double layer of cells=future embryo
-one sac=yolk sac
-one sac=amnion;eventually surrounds embryo
Human Development: Week 3
-embryo is enclosed in amniotic sac(in amnionic fluid)
-"head fold" is formed-by curling of embryo
-newly formed heart begins to beat
-chorionic villi form & become vascularized (blood vessels form)
-placenta begins to form
chorionic villi
extensions into endometrium
Human Development: Week 4
-endoderm forms embryonic gut
-rudimentary tail is present
-embryo is connected to chorion by body stalk
-muscles develop along spine, arm & leg buds form
*10,000x larger than original size
embryonic gut
a tube that is destined to become digestive system
Human Development: Week 5
-embryo begins to take up space in the uterus
-umbilical stalk(future umbilical cord) has formed
-mouth, nose, ears form
-placenta allows O2 to diffuse from maternal to fetal blood and CO2 to diffuse from fetal to maternal blood
-nutrients enter fetal blood
-urea diffuses into mother's blood
umbilical cord
links embryo to placenta
-exchange nutrients and wastes without allowing them to mix
Human Development: Week 6
-notochord, tail, and gill grooves are present
-eyes, fingers, toes begin to develop
-brain grows and develops
-reflex response, brain waves detected
-spontaneous movement
-skeleton forms
Human Development: Weeks 7 to 8
-other major organs have formed-liver, repro. organs (secreting hormones)
-after 2 months the embryo is called a fetus
-embryo/fetus is very susceptible to environmental factors & their effects during the 1st 2 months
-large protein substances can't pass through placenta, but some small, harmfull chemicals (alcohol), pathogens can pass
-lips are sensitive to souch, 3 cm long, 8 1/2 weeks-fingerprints
Human Development: Last 7 Months
-brain continues to develop
-head remains large
-brain & spinal cord grow, causing certain behaviors-thumb sucking, smiling, kicking, swallowing
-lungs, stomach, kidneys, and intestines grow-function vocal cords, hair
-fetus positions itself head down in uterus
-baby weight increases, baby recognizes mother's voice
Labor & Delivery
Labor: contraction of uterus
Delivery: expulsion of the baby from uterus
Labor
-as baby grows, it presses against uterus & stretches uterine muscles
-"near-term" fetus produces steriod hormones that increse estrogen & prostaglandins produced by placenta & uterus
-the hormones and stretching cause uterus to contract
-baby's head pushes against cervix - dialates
-neurons(Stretch receptors) in cervix send message to hypothalamus to release oxytocin
Delivery
-baby is expelled through birth canal(vagina)head first
-skull is compressed to fit through pelvis
-baby needs to breathe on its own
-continued uterine contractions expel the placenta(after birth)
-prostaglandins from umbilical cord constrict fetal blood vessels in cord(to stop blood flow)
Mammary Glands (after birth)
-estorgen and progesterone stimulate mammary glands to grow and develop, then the hormone levels decreases after birht
-prolactin level increases-causes milk production
-baby's suckling stimulates mammary glands-stimulates glands to release milk into ducts
Colostrum
fluid contained in breast milk during the first few days after birth-proteins and antibodies

regula mother's milk contains more fat and lactose
Aging
-accumlation of random damage to DNA and other biomolecules
-free radicals damage cells
-DNA repair enzymes become less functional due to mutations in genes causing malfunctions in cell metabolism