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Embryology Test 1 > Review Questions > Flashcards

Review Questions Flashcards

1
Q

What is the site of origin of the primordial germ cells in the early mammalian embryo?

A

Found in endodermal layer of yolk sac.

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2
Q

Define morphogenetic, differentiation, ontogeny, and determination.

A

Morphogenesis: Generation of form or assumption of new shape.

Differentiation: Complex of changes involved in progressive specialization of structure and function, often resulting in the formation of luxury molecules.

Ontogeny: All developmental processes from conception to death.

Determination: Process by which a cell or part of an embryo becomes restricted to a given developmental pathway.

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3
Q

At what sub-stage of meiosis I does pairing of homologous chromosomes occur?

A

Zygotene

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4
Q

At what stage of meiosis I does crossing-over occur?

A

Pachytene of Prophase I

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5
Q

Compare trisomy,monoploidy ,aneuploidy, and polyploidy and explain how they relate to human gametogenesis.

A

Trisomy: A form of aneuploidy in which you have three of a certain chromosome.

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6
Q

During oogenesis, when does the first meiosis arrest occur?

A

Diplotene stage of meiosis.

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7
Q

During oogenesis, when does the second meiotic arrest occur?

A

Metaphase II

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8
Q

Describe the oogonium in the ovary during the early fetal period with relation to meiotic stage and cellular make-up of the follicle.

A

They are diploid in nature and have no follicle. They have 1 chromatid/chromosome.

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9
Q

Which hormone is required for rapid transport of the egg through the isthmus of the oviduct?

A

Progesterone

L2S5

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10
Q

What is the maximum number of germ cells present in the early female embryo, and how do these numbers change throughout the lifetime of the individual?

A

At embryonic midterm, there are 7 million germ cells. 2 million remain at birth. Then shortly after birth there are about 400,000 primary oocytes. Approximately 40,000 will survive to puberty. About 400 will actually be ovulated in a lifetime.

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11
Q

What is the fate of most of the female germ cells?

A

They become atretic.

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12
Q

Describe the oocyte at the time of ovulation.

A
  • The egg is surrounded by a layer of follicle cells (Corona Radiata)
  • Accompanied by a very small, nucleated sister cell called a polar body

L3S13

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13
Q

What is the role of LH in resumption of meiosis? How is this related to MPF?

A

Due to LH surge which shuts down gap junctions between granulosa cells and oocyte. Then cAMP concentration is reduced, allowing activation of MPF.

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14
Q

Distinguish between theca interna and externa and their relationships to angiogenesis factor and to LH receptors and testosterone?

Lecture 1:33

A

Theca externa produces angiogenesis factor.

Theca interna has LH receptors and secretes testosterone.

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15
Q

What components of the Graafian follicle form the corpus luteum?

A

The residual thecal and granulosa cells of the follicle are left to proliferate and form the corpus luteum.

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16
Q

What is the function of aromatase?

A

Aromatase converts testosterone in 17beta-estradiol.

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17
Q

What hormone stimulates formation of LH receptors on granulosa cells?

A

Estrogens

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18
Q

What is the principal energy source for ejaculated spermatozoa?

A

Fructose or maybe ATP

L2S23

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19
Q

With regard to the passage of sperm through the female reproductive tract, where do they encounter the lowest pH?

A

Upper vagina

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20
Q

List the types of cells involved in spermatogenesis and indicate whether they are haploid or diploid.

A 
Primordial germ cells Diploid
Spermatogonia Diploid
Primary spermatocytes Diploid
Secondary spermatocytes Haploid
Spermatids Haploid
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21
Q

Which of the cellular stages of spermatogenesis lie outside the blood-testis barrier?

A

Acrosomal and maturation phase?

L2S13

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22
Q

Describe the functions of Sertoli Cells and cells of Leydig.

A

Sertoli: form an embryological barrier between sperm cells and the rest of the body and spermatogonia

Leydig: secrete testosterone, made from cholesterol

L2S16-20

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23
Q

What role do LH,FSH,estrogen, testosterone, and inhibin play in sperm cell production?

A

LH: binds to LH receptors on interstitial cells of Leydig. They in turn synthesize testosterone from cholesterol.

FSH: binds to surface FSH receptors on Sertoli cells. Which convert testosterone to estrogens. Also produce androgen-binding protein.

Sertoli cells produce inhibin.

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24
Q

What changes to sperm occur in the head of the epididymis?

A

The glycoproteins in the plasma membrane of sperm head.

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25
Q

Describe the relationship and functions of each of the following hormones to the menstrual cycle—both the ovarian aspect of the cycle and the uterine aspect of the cycle.

A

Ovarian:

  • FSH: in charge of the development of the Graafian follicle
  • LH: sharp rise in LH acts as a stimulus for ovulation
  • Progesterone: the outer part of the Graafian follicle remains behind and is made up of thecae cells which secrete progesterone.

Endometrial or Uterine:
- Estradiol: the granulosa cells of the developing follicle secrete estradiol, which is responsible for the proliferation of the endometrium

L3

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26
Q

A surge in which hormone level occurs 24 hours prior to ovulation?

A

Luteinizing Hormone (LH)

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27
Q

Describe the fate of the Graafian follicle after ovulation both in the event of fertilization and in the event of the absence of fertilization.

A

Residual thecal and granulosa cells of the follicle secrete estrogen and progesterone. Breakdown of the membrane granulosa allows the growth of blood vessels into the cavity of the ruptured follicle. Luteinization of granulosa cells, which secrete increasing amounts of progesterone plus some estrogen. They make the corpus luteum. The progesterone and estradiol are necessary to maintain the implantation of the fertilized oocyte.

IF NOT: CL regresses and levels of progesterone and estradiol descrease which starts next menstrual phase. Inhibin, released by the granulosa cells, inhibits secretion of gonadotropins, especially FSH, results in regression of the CL.
Replacement of granulosa lutein cells with collagenous scar tissue results in formation of the corpus albicans.

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28
Q

What is the role of inhibin in relation to the ovarian cycle?

A

Inhibits the secretion of FSH and gonadotropins. This causes the regression of the corpus luteum.

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29
Q

What is the most likely site of fertilization?

A

Ampulla

L2S26

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30
Q

Compare fertilization and menstrual age with regard to establishing the age of the embryo.

A

Fertilization age dates age of embryo from time of fertilization. Menstrual age dates age of embryo from start of mother’s last menstrual period. Two weeks greater than fertilization age.

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31
Q

Describe capacitation and explain where it occurs.

A

Required for sperm to undergo across all reaction.

Involves;

Removal of cholesterol from sperm surface.

Removal of glycoproteins.

Occurs inside the uterine tube in isthmus.

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32
Q

What is the major action of hyaluronidase?

A

It helps to breakdown the hyaluronic acid component of the intercellular matrix between the corona radiata cells.

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33
Q

Define “zygote”.

A

Term used to denote the single-called stage at which the male and female pronuclei have fused together and share a common membrane, establishing the diploid chromosome number.

34
Q

With regard to fertilization, what are the characteristics of the fast block to polyspermy?

A

Rapid depolarization of egg plasmalemma

-70 to +10 mV within 2-3 seconds

May last a little longer in mammals

Allows time for the egg to establish the slow block.

35
Q

With regard to fertilization, what are the characteristics of the slow block to polyspermy?

A

Mostly characterized by release of polysaccharides from the cortical granules located just under the plasmalemma of the egg.

Polysaccharides enter perivitelline space.

Hydration produces a swelling that increase the width of the pervitelline space.

36
Q

What roles do Z3 and phospholipase C zeta play in egg activation?

A

ZP3 protein stimulates across all reaction in mammals. Massive influx of calcium ion through sperm plasma membrane. Then the egg activation is initiated by release of calcium ion within egg cytoplasm in response to introduction of phospholipase C zeta by sperm.

37
Q

What ion initiates metabolic activation of the egg? What are the results of this activation?

A

Calcium

Initiates blocks to polyspermy

Stimulates increase in egg respiration and metabolism via the sodium-hydrogen ion exchange mechanism.

Results in an increase in pH and an increase in oxidative metabolism.

38
Q

What is the relation of Oct-4 to early cleavage?

A

Required to permit cleavage to proceed to 2-cell stage.

39
Q

What gene(s) is/are involved in the initiation of cleavage and the first cleavage division?

A

Oct-4

L5S25

40
Q

Describe the general structure of the blastocyst, including the different components.

A

Surrounded by zone pellucida

Large, eccentrically placed blastocoel

Consists of two types of cells:
Outer layer of cells-Trophoblasts
Inner mass of cells- Inner cell mass

Polarized has embryonic pole where the inner cell mass is located and abembryonic pole marks the opposite pole.

41
Q

Describe the role of specific transcription factors in the subdivision of the inner cell mass into epiblast and hypoblast.p

A

Nanog -> Cells entering inner cell mass earliest express nanog and are destined to become epiblast cells

Gata 6 -> Cells entering inner cell mass later express
Gata 6 and are destined to become hypoblast cells.

  • Gata 6 expression may be induced by FGF-4 secretion from the earlier cells.
42
Q

At what point in development does most transcription via the embryonic genome begin to occur?

A

By the four cell stage.

43
Q

Be familiar with the methylation cycle and know at what point during early development would methylation be lowest in both the maternal and paternal chromosomes?

A

Both Maternal and Paternal methylation are lowest during the Morula stage (8 to 16 Cells)

44
Q

What is the most common condition associated with spontaneously aborted embryos?

A

Chromosomal abnormalities

45
Q

Describe the inside-out hypothesis and cell polarity model theories for the establishment of polarity.

A

Inside out theory: Fate of blastomere is determined by its position within the embryo, not from intrinsic properties.

Cell Polarity: Depends on plane of cell division during cleavage

46
Q

Describe the role Nanog, Sox2, and Oct-4 in early differentiation.

A

Nanog: maintains integrity inner cell mast, no nano means differentiation into endoderm

Sox2: controls regulation genes involved in differentiation

Oct-4: with it, stays as inner cell mast and without it, it differentiates into trophoblast. Permits cleavage into 2 cell stage.

L5S25-26

47
Q

Compare Prader-Willi and Angelman Syndromes and relate to genomic imprinting.

A

PW: long arm of Ch 15 is deleted from the paternal Ch, the maternal is methylated

  • insatiable hunger
  • mental retardation
  • short stature, small hands and feet

AS: long arm of Ch 15 is deleted from the maternal Ch, the paternal is methylated

  • frequent laughter
  • uncontrolled muscle movement
  • unusual seizures
48
Q

What does Bateson’s rule refer to?

A

states that when duplicated structures are joined during critical development stages, one structure is the minor image of the other

49
Q

Define regulation and relate to twinning.

A

the ability of the embryo to compensate for removal of structures or for addition of structures?

50
Q

Relate number of X chromosomes to various phenotypes discussed in lecture and to Barr body formation.

A

Turner: XO (0)
Klinefelter: XXY (1), XXYY (1), XXXY (2), XXXXY (3)
Triplo-X: XXX (2)
Poly-X female: XXXX (3), XXXXX (4)

51
Q

When does X-inactivation take place in humans?

A

First few weeks of development

52
Q

What role does Xist play in X-inactivation?

A

a gene on the X chromosome that produces an RNA molecule that coats the X chromosome and induces X inactivation

53
Q

Describe the Barr body and number in normal male and female individuals and in individuals with abnormal numbers. Relate this to chromosome number in humans.

A

a Barr body is an extra X chromosome. 0 in normal males and 1 in normal females

54
Q

What tissue from the implanting embryo directly interfaces with the endometrial connective tissue?

A

syncytiotrophoblast

55
Q

Identical twinning is made possible by what process or property of the early embryo?

A

Regulation

56
Q

List functions of the zona pellucida.

A

Prevents the premature implantation of the cleaving embryo

57
Q

Describe the trophoblast and relate to its two main divisions. Which division directly interfaces with the endometrial connective tissue?

A

Divides into cellular cytotrophoblast (closest to inner cell mass) and a multinucleated syncytiotrophoblast (closest to the endometrium).

Syncytiotrophoblast penetrates the endometrial basal lamina.

58
Q

Describe the process of implantation.

A
  1. Attachment of expanded blastocyst to the endometrial epithelium.
  2. Penetration of the uterine epithelium.
  3. Invasion into the tissues underlying the epithelium.
  4. Erosion of the maternal vascular supply.
59
Q

What is the most common site for ectopic pregnancy?

A

Ampulla

60
Q

Describe the decidual reaction and its function(s).

A
  • The decidual reaction is the response of the endometrial stroma cells to the invading blastocyst.
  • Forms Large cellular matrix which completely surrounds embryo and endometrium
  • Prevents trophoblasts from degrading through the endometrial wall
  • A primary function of the decidual reaction is to provide an immunologically privileged site to protect the developing embryo from being rejected.
61
Q

Which signaling pathway is often involved in lateral inhibition?

A

Delta-Notch Pathway

62
Q

Which signaling pathway is often utilized by TGF-beta?

A

Tyrosine-Kinase Pathway

  • specifically, serene/threonine kinase receptor Type II
63
Q

Describe loss-of-function and gain-of-function mutations and give examples.

A
  • Loss of Function: Mutations in a gene which lose an ability normally found. Ex. Posterior to anterior transformation via inhibition of XIHBox in tadpoles
  • Gain of function: A type of mutation in which the altered gene product possesses a new molecular function or a new pattern of gene expression. Ex.
64
Q

Know which of the Drosophila genes involved in symmetry of the early embryo are derived from the maternal genome (maternal effect genes) rather than the embryonic genome.

A
  • Bicoid
  • Nanos
  • Hunchback
65
Q

Describe functions of the egg-polarity, gap, pair-rule, segment polarity, and homeotic genes in Drosophila.

A

Gap genes: Delete adjacent segments.

Pair-rule genes: Delete same part of pattern in every other segment.

Segment-polarity genes: Affect polarity of segment.

Homeotic genes: Determine the identity of individual segments. Activists other genes that encode these segment specific characteristics.

Egg polarity genes: Important in the establishment of the dorsal-ventral and anterior-posterior axes in the fruit fly.

66
Q

What signaling factor family is related to the segment polarity molecules in Drosophila?

A

Hedgehog family

67
Q

Describe the MiRNA pathway and its components.

A
  • miRNA precursor is cleaved via Dicer
  • AGO complexes with miRNA
  • Complex targets matching mRNA
68
Q

Describe the interrelationships among the Dorsal protein, Cactus protein and Toll protein in establishing the dorsal-ventral axis of Drosophila.

A
  • Dorsal protein is a product of the dorsal gene and is expressed in the ovary.
  • Cactus protein, product of the cactus gene, is also expressed in the ovary and binds to the dorsal protein and traps it in the cytoplasm.
  • Toll protein, produced by the toll gene, is also expressed in the ovary and leads to the degradation of the cactus protein, allowing the dorsal protein to move into the nuclei of the ventral cells.
69
Q

Which genes in Drosophila play a role in the establishment of the anterior-posterior axis?

A
  • Bicoid
  • Nanos
  • Hunchback (Of Notre-Dame)
70
Q

Zinc-finger transcription factor are associated with which gene family?

A
  • Sox family

- Wt1

71
Q

What is a morphogen?

A

A protein that varies in concentration and causes different developmental responses as a result of the concentration differences.

72
Q

What are bottle cells and what role do they play in gastrulation?

A

Transforming Epithelial cells are freed from basal lamina and lose E-Cadherins. Which then they turn into mesenchymal cells.

73
Q

What are the two major signaling molecules that play a role in the formation of the primitive streak?

A

TGF-B and Wnt

74
Q

What tissues are derived from the hypoblast?

A

extra-embryonic endoderm

75
Q

What tissues are derived from the epiblast?

A

ectoderm, endoderm, mesoderm

76
Q

When does gastrulation occur in humans?

A

end of the second week of gestation

77
Q

Describe the results of grafting a second dorsal lip to the blastocoel of an early amphibian embryo.

A

Grafting a second dorsal lip to the blastocoel of another embryo causes a second embryo to form below the first embryo.

78
Q

What factor represents the first sign of asymmetry in the mammalian embryo?

A

TGF-Beta

79
Q

Name the three classical markers of the organizer region in many vertebrates.

A

Chordin, Gossecoid and Fox-2.

80
Q

Which signal molecule is expressed by the isthmus organizer?

A

Wnt-1 (ant) and FGF-8 (post)

81
Q

Describe the results to neural action that would be caused by the absence of the planar cell polarity pathway.
Lecture 9:29

A

In the absence of the PCP pathway, neural folds remain apart and neural tube closure is absent.

Embryology Test 1 (1 decks)

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