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Histo/ Embryo/ Cell Bio > Embryology > Flashcards

Embryology Flashcards

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1
Q

Define ovum. What are its structural components?

A
  • unfertilized egg
  • ovum nucleus in center, surrounded by zona pellucida and corona radiata cells on outer layer
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2
Q

Define sperm. What are its structural components?

A
  • male gametocyte
  • head w/ acrosomal cap, mitochondrial sheath, tail
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3
Q

Define embryo.

A

developing human until the 8th week of gestation

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4
Q

Define fetus.

A

developing human from week 9 to birth

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5
Q

Define conceptus.

A

all structures that deveop from zygote

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6
Q

What are the general steps that occur in fertilization?

A
  1. ovum suspended in meiosis II released into oviduct
  2. sperm enters oviduct and undergoes capacitation (loss of glycocalyx)
  3. sperm meets egg, genetic mingling takes 24 hours
  4. once fertilized, egg completes meiosis II and is activated
    • zygote is now diploid, has a genetic sex
  5. cleavage initiated
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7
Q

What are the specific steps that occur when sperm first meets egg?

A
  1. sperm penetrates corona radiata
    • enzymes: hyaluronidase, tube enzymes
    • sperm tail wagging
  2. sperm penetrates zona pellucida
    • sperm acrosome releases enzymes
    • lysosomal enzymes from cortical granules in egg released
    • zona reaction: becomes impermeable to other sperm
  3. ovum-sperm membrane fusion
    • ovum completes meiosis II
    • sperm mitochondria destroyed
    • ovum activation
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8
Q

WEEK ONE: What happens during cleavage?

A

zygote undergoes division in oviduct, becomes morula (compaction) and then **blastocyst **(cavity organizes) which then hatches

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9
Q

WEEK ONE: What happens during hatching & implantation?

A

blastocyst hatches out of the zona pellucida & implants in the uterine lining (endometrium) via the blastocyst’s cytotrophoblast cells

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10
Q

WEEK TWO: What happens during the final stages of implantation & the decidual reaction?

A
  • Cytotrophoblast cells give rise to syncytiotrophoblastic cells: mass of cells without cell walls that spreads out from inner cell mass, and engulfs the uterine glands, releasing nutrients that encourage growth in conceptus, and maternal blood vessels, which create lakes of blood (lacunae coalesce)
  • Decidual Reaction: maternal cells undergo change to contain nutrients and lipids to feed conceptus
  • envelopment of maternal blood vessels establishes utero-placental flow
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11
Q

WEEK TWO: What happens during the formation of the bilaminar disk?

A
  • former contents of the inner cell mast (hypoblast and epiblast) combine to form the bilaminar disk
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12
Q

WEEK TWO: What happens during the formation of amniotic cavity & yolk salk?

A

spaces form between inner mass cells to create amniotic cavity; yolk sac begins to expand to form embryonic mesoderm

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13
Q

What does the Epiblast become?

A
  • EMBRYO
    • embryonic ectoderm
    • embryonic mesoderm
    • embryonic endoderm
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14
Q

What does the Hypoblast become?

A
  • extra-embryonic endoderm of yolk sac –> extra-embryonic mesoderm
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15
Q

What is the amnion?

A
  • large sac containing amniotic fluid in which the fetus is suspended by the umbilical cord
  • fluid: absorbs jolts, allows for fetal movements, prevents adherence of embryo to surrounding tissues
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16
Q

Why is the second week called the “week of twos”?

A
  • everything divides into TWOs
    • inner cell mass: epiblast and hypoblast
    • trophoblast: cytotrophoblast and syncytiotrophoblast
    • yok sacs: primary and secondary
    • cavities: amnion and chorion
    • chorionic cavity: lined by two layers of extraebryonic mesoderm
    • two-layered membranes: amnion, chorion, yok sac
17
Q

What are some clinical consequences of abnormal implantation and abnormal embryos?

A
  • ectopic pregnancy: implantation of embryo in oviduct
  • Spina Bifida: abnormal closure of neural folds between 3-4 weeks, neural tube defects, spinal defect
18
Q

WEEK 3: Describe the steps to gastrulation.

A
  • primitive streak moves caudally to cranially
    • establishes polarity, cranio/caudal region, right and left
  • epiblast migrate to form 3 germ layers: trilaminar disc
    • ectoderm
    • mesoderm
    • endoderm

https: //www.youtube.com/watch?v=iHmBIJs77ZQ
https: //www.youtube.com/watch?v=nQU5aKKDwmo&src_vid=rN3lep6roRI&feature=iv&annotation_id=annotation_1295988581

19
Q

WEEK 3: Describe notochord formation.

A
  1. cord of cells branch off primitive streak and dive into mesoderm and continue moving cranially
    • oropharyngeal node: cranial end
    • primitive node: caudal end
  2. induces overlying ectoderm to form neural plate
  3. functions as primary signaling center for early embryo
  4. neural plate forms grove and invaginates at the neural crests to become neural tube on top of notocord
    • zips from cranial to caudal end
20
Q

What is differential growth?

A
  • some areas grow faster than others
    http: //www.indiana.edu/~anat550/genanim/latfold/latfold.swf

Histo/ Embryo/ Cell Bio (5 decks)

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