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Anatomy > Early Development I > Flashcards

Early Development I Flashcards

1
Q

Gametes

A

. Derived from primordial germ cells
. Male: spermatogonia
. Female: oogonia

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2
Q

Primordial germ cell

A

. From wall of yolk sac then migrate to developing gonads
. Diploid, carry full chromosomal complement of 46 chromosomes (2N)
. Proliferate via mitosis

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3
Q

Spermatogenesis

A

. Spermatogonia dormant until puberty
. Begin to multiply
. Enter meiosis I becoming primary spermocytes
. Complete meiosis I yielding 2 secondary spermatocytes
. Undergo meiosis II yielding 4 haploid spermatids (n, 23)
. Morphological changes mature spermatozoa

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4
Q

Oogenesis

A

. Oogonia multiply w/in ovary via mitosis during embryo phase
. Fetal phase oogonia begin 1st meiotic division becoming primary oocytes occupying primitive follicles
. Arrested in meiosis I until puberty
. After 1st period primary oocytes mature from reproductive hormones
. During ovulation primary oocyte completes meiosis I making secondary oocyte and enters meiosis II
. Arrested in meiosis II until fertilization when it finishes and makes mature ovum (n, 23)

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5
Q

Ovulation occurs on day ___ if 1st day of period is day 1

A

14

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6
Q

How pregnancy timeline is calculated

A

. 280 dates (40 weeks) from date of last period

. 366 days (38 weeks) from date of fertilization

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7
Q

Pregnancy trimesters

A

. 3 trimesters of 13 weeks each

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8
Q

Pre-embryonic period

A

. Weeks 1-2
. Begins at fertilization
. Initial differentiation of embryonic and extraembryonic tissues and implantation

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9
Q

Embryonic period

A

. Weeks 3-8

. Establishment of primary germ layers, vertebrate body plan, and organogenesis

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10
Q

Fetal period

A

. Weeks 9-38

. Organ system maturation and growth

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11
Q

How long is secondary oocyte viable for?

A

24 hours after ovulation

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12
Q

Fertilization

A

. Ovum and spermatozoon produce diploid zygote

. Day 1 week 1 of development

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13
Q

Most common site of fertilization

A

Ampulla of uterine tube

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14
Q

Acrosomal reaction

A

. Coat of enzymes (acrosome) covers head of sperm

. Binds to and breaks down protein coat of zone pellucida surrounding oocyte

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15
Q

Zygote

A

. Diploid

. Cytoplasm mostly maternally inherited

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16
Q

Conceptus

A

. Zygote and it’s derivatives

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17
Q

Blastomeres

A

. Derived from zygote mitotically dividing as it descends down uterine tube

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18
Q

Morula

A

. Solid ball of 1620 blastomeres in 2 cell groups
. Inner cell mass: internal cells that become embryo proper
. Trophoblast: surface blastomeres that contribute to placenta and fetal membranes
. Contains ETCHbox genes

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19
Q

ETCHbox genes

A

. Homeobox genes unique to placental mammals

. Exclusively expressed during 8-cell through morally phase

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20
Q

Blastocyst

A

. Forms as conceptus enters uterus on day 4
. Has blastocele cavity that separates inner mass (embryoblast) from most of the trophoblast
. Embryoblast occupies one pole
. Trophoblast forms external wall

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21
Q

In terms of differentiating ability, Blastomeres are ___ while embryoblast are ___

A

. Totipotent (can form complete embryo)

. Pluripotent (can give rise to lost any cell of tissue)

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22
Q

Implantation

A

. Day 6
. Zone pellucida degenerates
. Blastocyst implants w/in endometrial lining of uterus
. Most common in posterosuperior uterine wall
. Embryoblast oriented toward the wall
. Trophoblast adjacent to embryoblast, releases enzymes that erode into endometrial surface
. Takes several days
. At end blastocyst is surrounded by endometrium

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23
Q

Ectopic implantation

A

. Common in uterine tube but can also happen in cervix, ovary, and abdominal cavity
. In tubal pregnancies, not viable beyond 2 months
. Leading cause of first trimester bleeding

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24
Q

What occurs on day 8?

A

. Trophoblast divides into cytotrophoblast (inner layer) and syncytiotrophoblast (outer layer)
. Embryoblast divides into epiblast (cells close to trophoblast) and hypoblast (cells close to blastocele) making blastula (bilaminar disc)

25
Q

Syncytiotrophoblast

A

. Multinucleated mass from breakdown of cell membrane

. Produces human chorionic gonadotropin (hCG) to stimulate corpus luteum to produce progesterone

26
Q

Amniotic cavity

A

. Develops w/in epiblast

27
Q

Yolk sac

A

Hypoblast cells proliferate and migrate to surround blastocele

28
Q

Extraembryonic mesoderm

A

Mesenchymal cells derived from epiblast proliferate to surround the amniotic cavity, yolk sac, and embryonic disc

29
Q

Chorionic cavity

A

. Develops w/in extraembryonic mesoderm

. Expands to envelop the yolk sac, amniotic sac, and embryonic disc

30
Q

Chorion

A

. Membranous wall of chorionic cavity
. Consists of extraembryonic mesoderm and trophoblast
. Contributes to fetal portion of placenta

31
Q

Amnion

A

Membraneous wall of amniotic cavity

. Consists of extraembryonic mesoderm and epiblast

32
Q

Connecting stalk

A

. Extraembryonic mesoderm connecting bilaminar disc to trophoblast
. Contributes to future umbilical cord

33
Q

Gastrulation

A

. Embryonic cell migration that leads to formation of a trilaminar embryonic disc or gastrula
. Controlled by fibroblast growth factor 8 (FGF8)
. Initiated day 15 at caudal end of blastula by formation of primitive streak in epiblast
. Primitive streak elongates to form primitive groove that terminates cranially at primitive node

34
Q

Primitive node

A

. Raised rim of epiblast

35
Q

During gastrulation, epiblast cells proliferate and migrate ____

A

Through primitive groove moving lat. and ant.

36
Q

Endoderm

A

.cells migrate deep to epiblast and displace hypoblast

37
Q

Intraembryonic mesoderm

A

. Cells that migrate btw epiblast and endoderm

38
Q

Ectoderm

A

Nonmigratory epiblast cells

39
Q

Prechordal plate

A

. Mesodermal cells that migrate through primitive pit and move directly ant.

40
Q

Notochord

A

. Midline CT rod
. Forms cranial to caudal as primitive pit migrates post.
. Defining characteristic of all vertebrates
. Scaffold of developing vertebral column
. Persists through early childhood as part of the nucleus purposes

41
Q

At each end of embryo, a depressed region of ectoderm displaces mesoderm and fuses to endoderm forming ____

A

. Oropharyngeal membrane

. Cloacal membrane

42
Q

Oropharyngeal membrane

A

. Located at cephalic end, marking location of future mouth

43
Q

Cloacal membrane

A

. Caudal end

. Marking location of future anus and urogenital openings

44
Q

Allantois

A

. Fingerlike outpouching yolk sac invades connecting stalk

45
Q

Neurulation

A

. Formation of neural tube (precursor to CNS)
. Directed by FGF suppressioni of BMP activity
. Molecular signals secreted by primitive node, notochord, and prechordal plate induce proliferation of ectodermal cells forming midline neural plate (neuroectoderm)

46
Q

What happens on day 18?

A

. Neural plate invaginates to form neural groove flanked by neural folds
. Neural groove deepens, folds meet and fuse to make hollow neural tube cranially to caudally from center of disc
. Completed during week 4 and gives rise to brain and spinal cord

47
Q

Neural crest

A

. Special cell population in neural folds
. Become mesenchymal cells and migrate throughout developing embryo
. Gives rise to variety of structures throughout body

48
Q

Neural tube defects

A

. Failure to close causes CNS issues
. Anencephaly (lethal)
. Spina bifida
. Assoc. w/ maternal folic acid deficiency

49
Q

What happens starting day 19?

A

. Mesoderm proliferates and condenses into 3 parallel columns located lat. on notochord bilaterally
. Paraxial mesoderm
. Intermediate mesoderm
. Lateral plate mesoderm

50
Q

Paraxial mesoderm

A

. Becomes segmented into somites adjacent to notochord and neural tube
. Cranial to caudal

51
Q

Somites subdivided into _____

A

. Dermotome
. Sclerotome
. Myotome

52
Q

Dermotome

A

. Contributes to dermis of back and ventrolateral trunk

53
Q

Sclerotome

A

Gives rise to vertebrae and ribs

54
Q

Myotome

A

. Gives rise to segmental muscles of back and anterolateral body wall

55
Q

Intermediate mesoderm

A

. Gives rise to parts of urogenital system

56
Q

Lateral mesoderm

A

. Somatic mesoderm (parietal): gives rise to parietal serous membranes, parts of body wall, ventral dermis, and CT of limbs
. Splanchnic mesoderm (visceral): gives rise to visceral serous membranes, smooth muscle of gut, and blood vessels

57
Q

Intraembryonic coelom

A

. Space in between somatic and splanchnic mesoderm

. Gives rise to adult body cavities

58
Q

Cardiogenic region

A

. Extension of splanchnic mesoderm cranial to oropharyngeal membrane
. Precursor to heart

Anatomy (49 decks)

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