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41 Cards in this Set
- Front
- Back
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direct development
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-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
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embryonic membranes
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4 membranes that protect and nourish the embryo
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chorion
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-outermost embryonic membrane
-forms the fetal part of the placenta -surface for gaseous(CO2/O2), nutrient and waste exchange |
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amnion
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-sac around embryo
-keeps embryo enclosed in fluid (amniotic fluid) |
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allantois
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-forms blood vessels of umbilical cord
-carries blood between embryo and placenta |
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yolk sac
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-forms part of umbilical cord and digestive tract
-membranes sac with very little yolk, but forms blood cells |
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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 |
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zygote
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fertilized egg after 1st cell division
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blastula
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(in humans-a blastocyst)
-embryo consists of a hollow ball with an outter layer of cells |
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blastocoel
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space inside the blastocyst/blastula
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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 |
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Blastopore
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(an indentation)
forms on one side of blastula |
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endoderm
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innermost layer of embryonic tissue
develops into digestive, resp. system, liver and pancreas |
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ectoderm
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outermost layer of embryonic tissue
develops into hair and epidermis, nervous system and glands |
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mesoderm
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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 |
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notochord
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firm, flexible, found in vertebrates
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Organogenesis
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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 |
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Differentiation
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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 |
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Human Development: In 4 days
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egg is fertized in oviduct, then travels to uterus
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Human Development: Week 1 to 2
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-blastocyst forms
-contains inner cell mass -implantation -outer layer of cells helps form placenta -gastrulation occurs |
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blastocyst
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hollow ball of cells
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inner cell mass
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cluster of cells that develops into embryo
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implantation
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outer wall of blastocyst is sticky, so it adheres to uterus and burrows into the uterine wall to obtain nutrients
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placenta
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-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 |
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Fetal Alcohol Syndrome
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alcohol can pass through the placenta and enter the baby's blood stream
-smaller brain -inhibited growth |
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Embryonic disc
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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 |
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Human Development: Week 3
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-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 |
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chorionic villi
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extensions into endometrium
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Human Development: Week 4
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-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 |
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embryonic gut
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a tube that is destined to become digestive system
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Human Development: Week 5
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-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 |
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umbilical cord
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links embryo to placenta
-exchange nutrients and wastes without allowing them to mix |
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Human Development: Week 6
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-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 |
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Human Development: Weeks 7 to 8
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-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 |
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Human Development: Last 7 Months
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-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 |
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Labor & Delivery
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Labor: contraction of uterus
Delivery: expulsion of the baby from uterus |
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Labor
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-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 |
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Delivery
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-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) |
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Mammary Glands (after birth)
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-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 |
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Colostrum
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fluid contained in breast milk during the first few days after birth-proteins and antibodies
regula mother's milk contains more fat and lactose |
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Aging
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-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 |
