Embryology 1/2 (First Exam)

Front 1

Amniotic cavity

Back 1

the fluid-filled sac that forms adjacent to the epiblast of the embryonic disc; as development progresses, this sac expands and is drawn ventrally to surround the embryo

Front 2

Blastocyst

Back 2

the hollow sphere of cells derived from the morula and that consists of trophoblast cells and an inner cell mass

Front 3

Blastocoele

Back 3

the fluid-filled cavity in the blastocyst

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Chorion

Back 4

extraembryonic membrane consisting of trophoblast and extraembryonic mesoderm

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Chorionic cavity

Back 5

space that separates the embryo with its attached amnion and yolk sac from the chorion; also known as the extraembryonic coelom

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Cleavage

Back 6

the first series of cell divisions following fertilization that result in an increase in cell number without an accompanying increase in embryo mass

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Cytotrophoblast

Back 7

cells of the trophoblast that retain their cell membranes

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Ectoderm

Back 8

the layer (of the 3 germ cell layers) which forms the nervous system from the neural tube and neural crest and also generates the epidermis of the skin

Front 9

Embryonic disc

Back 9

the part of the inner cell mass of a blastocyst from which the embryo of a placental mammal develops

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Embryonic period

Back 10

typically described as the period when most of the organ systems are developing, ending at about 8 weeks post-fertilization as the fetal period begins

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Endoderm

Back 11

the layer (of the 3 germ cell layers) which forms the epithelial lining of the respiratory system, gastrointestinal tract, and accessory digestive organs

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Epiblast

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the layer of cells that, along with the hypoblast, form the bilaminar embryonic disc; eventually gives rise to virtually the entire embryo and the amnion

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Fetal Period

Back 13

weeks 9 through 38 post-fertilization in humans; the stage of development following the embryonic period

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Gastrulation

Back 14

process of epiblast ingression through the primitive streak that results in formation of the mesoderm and endoderm

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Germ layer

Back 15

three cellular layers (ectoderm, mesoderm, and endoderm) that will form all tissues of the embryo

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Gestational period

Back 16

the span of time from conception to birth

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Hypoblast

Back 17

the layer of cells that, along with the epiblast, form the bilaminar embryonic disc; the layer of cells that becomes the inner lining of the yolk sac

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Implantation

Back 18

the process of attachment and invasion of the uterine endometrium by the blastocyst

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Inner cell mass (embryoblast)

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cells that segregate within the center of the morula and will differentiate into the embryo itself

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Intermediate mesoderm

Back 20

the portion of the intraembryonic mesoderm that initially lies between the paraxial and lateral plate mesoderm and that gives rise to components of the urogenital system

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Lateral plate mesoderm

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most lateral part of intraembryonic mesoderm; splits into splanchnic (visceral) and somatic (parietal) layers

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Mesoderm

Back 22

the middle of the 3 germ cell layers of the embryo; gives rise to skeletal and connective tissue and to muscle

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Morula

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early stage in development in which the cells have divided to produce a solid mass with a "mulberry" appearance

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Neural crest

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populatiom of cells that arise from the lateral margins of the neural plate and that migrate ventrolaterally, subsequently differentiating into many different cell types including sensory neurons and melanocytes

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Neural tube

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ectodermal tube that is the progenitor of the brain and spinal cord

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Notochord

Back 26

axial mesoderm that is required for neural induction and that forms the nucleus pulposus of the intervertebral discs

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Paraxial mesoderm

Back 27

mesodermal cells close to the midline between ectoderm and endoderm, from which somites arise

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Prechordal plate

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Prechordal: situated rostral to the notochord; synonymous with prochordal. Forms the mouth (oralpharyngeal opening)

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Primitive streak

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region of epiblast located in the caudal midline where cells ingress to become definitive endoderm and mesoderm; i.e., where gastrulation occurs

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Syncitiotrophoblast

Back 30

the syncytial layer of the trophoblast that actively invades the uterine wall and contributes to the placenta

Front 31

Trophoblast

Back 31

he outer layer of the blastocyst that differentiates into the cytotrophoblast and syncytiotrophoblast

Front 32

Yolk sac

Back 32

a membranous sac that is comprised of extraembryonic endoderm and mesoderm and that is continuous with the gut cavity of the embryo

Front 33

Apical ectodermal ridge

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population of ectodermal cells located at the distal margin of the limb bud; critical for proximodistal outgrowth of the limb

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Dermatome

Back 34

the dorsolateral subsegment of each somite that contributes to development of the dermis

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Dermomyotome

Back 35

the nonsclerotomal portion of each somite; it contributes to the formation of dermis and muscles of the trunk

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Endochondral ossification

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bone formation that occurs from an ossifying cartilagenous precursor.

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Fontanelle

Back 37

region where several sutures meet in the perinatal skull; often referred to as "soft spot"

Front 38

Intramembral ossification

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the process of bone formation that does not entail a cartilaginous precursor, occurs in cranial vault and clavicle

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Mesenchyme

Back 39

an embryonic undifferentiated (loose) connective tissue derived from mesoderm or neural crest cells

Front 40

Paraxial mesoderm

Back 40

mesodermal cells close to the midline between ectoderm and endoderm, from which somites arise

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Myotome

Back 41

the portion of the dermomyotome that generates skeletal muscle

Front 42

Neurocranium

Back 42

vault and base of the skull; that part of the skull that surrounds the brain; the remainder of the skull is considered viscerocranium

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sclerotome

Back 43

ventromedial portion of each somite that form the skeletal components of the trunk and occipital portion of the skull

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somite

Back 44

segmental block of paraxial mesoderm

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Viscerocranium

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the bones of the face; mainly derived from neural crest cells that are associated with the maxillary and mandibular prominences

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Zone of polarizing activity

Back 46

region of developing limb that is critical for establishment of the cranio-caudal axis (thumb or big toe versus 5th digit side) of the limb