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Embryology 2019 > Exam 1 Review > Flashcards

Exam 1 Review Flashcards

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1
Q

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

A

endodermal layer of the yolk sac

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2
Q

• Define morphogenesis, differentiation, ontogeny, and determination.

A

morphogenesis: Generation of form or assumption of a new shape

Differentiation: Complex of changes involved in progressive specialization of structure and function, often resulting in the formation of luxury molecules
(Luxury molecules are molecules that are not necessary for the survival of a the cell, but are crucial to fueling the developmental process)

Ontogeny: Includes 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

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5
Q

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

A

Trisomy: having more chromosomes than you should have (47 for example)

Monosomy: having less chromosomes than you should have (45 for example)

Aneuploidy: abnormal number of chromosomes

Polyploidy: more than 2 complete sets of chromosomes

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6
Q

• During oogenesis, when does the first meiotic arrest occur?

A

during the diplotene stage of meiosis I

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7
Q

• During oogenesis, when does the second meiotic arrest occur?

A

during metaphase of meiosis 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

it is 2n 2c with no follicle

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9
Q

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

A

progesterone

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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

7 million in the early female embryo

400,000 after birth

the number decreases as time passes and only about 400-450 eggs will be ovulated

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11
Q

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

A

they die (degeneration

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12
Q

• Describe the oocyte at the time of ovulation.

A

It is an ovum at metaphase II

has its first polar body, zona pellucida, corona radiata, and an expanded cumulus oophorus)

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13
Q

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

A

an LH surge is what triggers meiosis to resume

LH shuts down gap junctions between granulosa cells and the oocyte which decreases cAMP levels

decreased cAMP levels activates MPF (maturation promoting factor)

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14
Q

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

A

Theca Externa: produces angiogenesis factor

Theca Interna: has LH receptors so that it may release testosterone upon the presence of LH hormone

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15
Q

• What components of the Graafian follicle form the corpus luteum?

A

The corpus luteum is formed by the “residual theca and granulosa cells” that proliferate together to form the large granular structure known as the corpus luteum.

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16
Q

• What is the function of aromatase?

A

Aromatase converts testosterone into 17Beta-estradiol

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17
Q

• What hormone stimulates formation of LH receptors on granulosa cells?

A

Estrogens stimulate the formation of the LH receptors that develop on these cells

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18
Q

• What is the principal energy source for ejaculated spermatozoa?

A

fructose (added to the sperm by the seminal vesicles

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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

In the 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 (2N)

Spermatogonia (2N): this includes Type A stem cells and Type B cells which leave the mitotic cycle and enter the meiotic cycle under the influence of retinoic acid

Primary Spermatocytes (2N): first maturation division occurs here (meiosis I)

Secondary Spermatocytes (N): Second maturation division occurs here (meiosis II)
	X2 cells

Spermatids (N): x4 cells

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21
Q

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

A

spermatogonium and preloptene spermatocytes

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22
Q

• Describe the functions of Sertoli cells and cells of Leydig.

A

Sertoli cells form an immunological barrier (blood-testis barrier) between the forming sperm cells and the rest of the body and spermatogonia
(secrete estrogen, inhibin, and anti-Mullerian factor)

Leydig cells produce testosterone

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23
Q

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

A

LH: LH binds to LH receptors on interstitial cells of Leydig, which then synthesize testosterone from cholesterol

FSH: activates FSH receptors of Sertoli cells, causing them to make testosterone to estrogen AND Leydig cell stimulatory factor

Estrogen: necessary for spermatogenesis

Testosterone: Testosterone from interstitial cells of Leydig is carried via the blood to androgen receptors on Sertoli cells and stimulates the formation of a new blood-testis barrier closer to the basal lamina

Inhibin: suppresses FSH

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24
Q

• What changes to sperm occur in the head of the epididymus?

A

changes in the glycoproteins in plasma membrane on the head of the sperm

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25
• A surge in which hormone level occurs 24 hours prior to ovulation?
LH
26
• Describe the fate of the Graafian follicle after ovulation both in the event of fertilization and in the event of the absence of fertilization.
If fertilization does not occur: The Corpus luteum regresses and levels of progesterone and estradiol will subsequently decrease (leading into the next menstrual phase) If fertilization DOES occur: Chorioic gonadotropin from future placental tissues keeps the corpus luteum functional Granulosa lutein cells are replaced by theca lutein cells Corpus luteum remains functional for several months into the pregnancy
27
• What is the role of inhibin in relation to the ovarian cycle?
Inhibin is released by granulosa cells and inhibits the secretion of gonadotropin (especially FSH), which leads to the regression of the corpus luteum (this is when fertilization does not occur)
28
• What is the most likely site of fertilization?
In the Ampulla of the isthmus
29
• Compare fertilization and menstrual age with regard to establishing the age of the embryo.
Fertilization age: dates age of embryo from the time of fertilization Menstrual age: Dates age of embryo from the start of the mother's last menstrual period (2 weeks greater than the fertilization age)
30
• Describe capacitation and explain where it occurs.
Capacitation is an activity that requires the binding of sperm to the tubal epithelium and removes the cholesterol (from the surface of the sperm) and glycoproteins (from the epididymis) it occurs inside of the isthmus of the uterine canal
31
• What is the major action of hyaluronidase?
Hyaluronidase is one of the major enzymes in the acrosome that destroys the hyaluronic acid component of the intracellular matrix between each cell of the corona radiata
32
• Define “zygote.”
Zygote: the single-celled stage at which the male and female pronuclei have fused together and share a common membrane(should be diploid at this point)
33
• With regard to fertilization, what are the characteristics of the fast block to polyspermy?
Fast Block: consists of a rapid depolarization of the egg plasmalemma, which temporarily prevents polyspermy and allows time for the egg to establish the slow block
34
• With regard to fertilization, what are the characteristics of the slow block to polyspermy?
Slow Block: mostly characterized by the release of polysaccharides from the cortical granules from just beneath the plasmalemma of the egg cell
35
• What roles do ZP3 and phospholipase C zeta play in egg activation?
ZP3 is one of 4 glycoproteins that make up the SP, and is responsible for the attachment of the sperm to the SP ZP3 also stimulates the acrosomal reaction in mammals by acting through G proteins in the sperm's plasma membrane Phospholipase C zeta is released by the sperm and initiates a release of Ca2+ ions within the cytoplasm of the egg
36
• What ion initiates metabolic activation of the egg? What are the results of this activation?
Ca2+ Initiates blocks to polyspermy Stimulates increase in egg respiration and metabolism via the sodium-hydrogen ion exchange mechanism increases pH and an increase in oxidative metabolism
37
• What is the relation of Oct-4 to early cleavage?
Oct-4: Expressed in developing oocytes/zygotes and is required to permit cleavage to proceed to the 2-cell stage Expressed in all morula cells and may play a role in the maintenance of the undifferentiated state (Without Oct-4, inner cells differentiate into trophoblast)
38
• What gene(s) is/are involved in the initiation of cleavage and the first cleavage division?
Oct 4 Cdx-2 Nanog Sox2
39
• Describe the general structure of the blastocyst, including the different components.
Has a large, eccentrically placed, blastocoel and still has an intact zona pellucida on the outermost edge Embryonic pole is where the inner cell mass is The Abembryonic pole is opposite the inner cell mass
40
• Describe the role of specific transcription factors in the subdivision of the inner cell mass into epiblast and hypoblast.
Nodal and Wnt are in the Epiblast Left 1 is in the hypoblast (Cer1 blocks Nodal activity from moving into the hypoblast region)
41
• At what point in development does most transcription via the embryonic genome begin to occur?
By the 4 cell stage
42
• 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?
Methylation is at it's lowest for both maternal and paternal genes between the 8 cell stage and the morula stage (8-16 cell ball stage)
43
• What is the most common condition associated with spontaneously aborted embryos?
Chromosomal abnormalities, such as polyploidy or trisomy’s of individual chromosomes
44
• Describe the inside-out hypothesis and cell polarity model theories for the establishment of polarity.
Inside-out hypothesis: states that the fate of the blastomere is determined by it's position within the embryo, not from intrinsic properties
45
• Describe the role of Nanog, Sox2, and Oct-4 in early differentiation.
Oct-4: Expressed in developing oocytes/zygotes and is required to permit cleavage to proceed to the 2-cell stage Expressed in all morula cells and may play a role in the maintenance of the undifferentiated state Without Oct-4, inner cells differentiate into trophoblast Nanog: Produced by inner cells late in the morula stage and maintains the integrity of the inner cell mass (along with Oct-4) Without Nanog, inner cells differentiate into endoderm Sox2: First expressed in the 8-cell stage and helps (along with Oct-4) control the regulation of genes involved in differentiation
46
• Compare Prader-Willi and Angelman syndromes and relate to genomic imprinting.
Prader-Willi Syndrome: Deletion in the long arm of chromosome 15 and is always inherited from the father Small hands/feet and short stature Poor sexual development Mental retardation Voracious appetite (usually causes obesity) Angelman Syndrome: Deletion in the long arm of chromosome 15 and is always inherited from the mother Exhibit frequent laughter (severe mental retardation) Uncontrolled muscle movement (ataxia) Large mouth Unusual seizures
47
• What does Bateson’s rule refer to?
Bateson's Rule: states that when duplicate structure are joined during critical developmental stages, one structure is the mirror image of the other (a reversal of symmetry of organs or even entire embryos)
48
• Define regulation and relate to twinning.
Regulation: Refers to the ability of an embryo to compensate for the removal of structures or for the addition of structures can lead to severe deformities/siamese twinning
49
• Relate number of X chromosomes to various phenotypes discussed in lecture and to Barr body formation.
Barr bodies: basically the small, compacted remnant of the X chromosome that was inactivated (found only in females bc males express their single X chromosome) males are more likely to express x-linked diseases bc they have one less X
50
• When does X-inactivation take place in humans?
during the first few weeks of development
51
• What role does Xist play in X-inactivation?
The Xist gene is an X inactivation-specific transcript that is found on the X chromosome It produces an RNA molecule that coats that X chromosome and induces X-inactivation (via removal of acyl groups from histones)
52
• Describe the Barr body and numbers in normal male and female individuals and in individuals with abnormal numbers. Relate this to chromosome number in humans.
Barr bodies: basically the small, compacted remnant of the X chromosome that was inactivated (found only in females bc males express their single X chromosome) basically makes sure women dont have an extra X chromosome (male Y chromosomes are small enough to be overlooked)
53
• What tissue from the implanting embryo directly interfaces with the endometrial connective tissue?
The syncytiotrophoblast
54
• Identical twinning is made possible by what process or property of the early embryo?
regulation?
55
• List functions of the zona pellucida.
promotes maturation of the oocyte and follicle Serves as a barrier that allows only sperm of the same species through Initiates acrosomal reaction After fertilization, it prevents polyspermy serves as immunological barrier between mother and child but still lets necessary signals through prevents blastomeres from dissociating facilitates differentiation of trophoblastic cells prevents premature implantation of the embryo
56
• Describe the trophoblast and relate to its two main divisions. Which division directly interfaces with the endometrial connective tissue?
a Trophoblast is divided into the cytotrophoblast (closest to the inner cell mass) and the syncytiotrophoblast (which interfaces with the endometrial CT)
57
• Describe the process of implantation.
1. Attachment of expanded blastocyst to the endometrial epithelium Initial contact is between the endometrial surface and the embryonic pole of the blastocyst, facilitated by adhesion molecules that are present on BOTH the endometrium and the trophoblast Leukemia inhibiting factor is expressed by the endometrium and respective receptors on the trophoblast 2. Penetration of the uterine epithelium Trophoblast separates into a cellular cytotrophoblast (closest to the inner cell mass) and a multinucleated syncytiotrophoblast (closest to the endometrium) Syncytiotrophoblast projections penetrate the endometrial basal lamina and begin to invade the endometrial stroma, which creates the appearance of trophoblastic lacunae Eroded endometrial blood vessel fill the trophoblastic lacunae with maternal blood, and the trophoblast's "invasive" behavior stops at this point 3. Invasion into the tissues underlying the epithelium 4. Erosion of the maternal vascular supply
58
• What is the most common site for ectopic pregnancy?
the fallopian tube
59
• Describe the decidual reaction and its function(s).
Decidual reaction: the response of the endometrial stroma cells to the invading blastocyst (basically what prevents the trophoblast from eroding (penetrating) too deep) The result of the decidual reaction is a massive cellular matrix that surrounds the embryo and fills most of the endometrium Infiltrating leukocytes in the endometrium secrete interleukin-2 in order to prevent the mother's immune system from treating the embryo as a foreign body The primary function of the decidual reaction is to provide an immunologically privileged site to protect the developing embryo from being rejected
60
• Which signaling pathway is often involved in lateral inhibition?
delta-notch
61
• Which signaling pathway is often utilized by TGF-β?
Receptor Tyrosine Kinase Pathway
62
• Describe loss-of-function and gain-of-function mutations
Loss-of-function mutations: result in posterior to anterior transformations Gain-of-function mutations: result in anterior to posterior transformations
63
• 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.
Bicoid Swallow Caudal Oskar Torso Trunk (SCOTT B mnemonic)
64
• Describe functions of the egg-polarity, gap, pair-rule, segment polarity, and homeotic genes in Drosophila.
egg polarity: establishes polarity Gap: defines broad regions in the egg Pair-rule: define 7 segments Segment-polarity: define 14 segments Homeotic: determines regional characteristics
65
• Describe the MiRNA pathway and its components.
miRNA precursors are cleaved by Dicer enzymes into miRNA and then loaded with AGO (argonaute) Next, the AGO and miRNA complex go to influence gene expression
66
• Describe the interrelationships among the Dorsal protein, Cactus protein, and Toll protein in establishing the dorsal-ventral axis of Drosophila.
Dorsal and cactus proteins bind together, trapping dorsal in the cytoplasm Toll degrades cactus, which allows dorsal to move into the nuclei of ventral cells (all of this occurs in the ovaries)
67
• Which genes in Drosophila play a role in the establishment of the anterior-posterior axis?
Bicoid Nanos Hunchback
68
• Zinc-finger transcription factors are associated with which gene family?
Sox genes | WT1
69
• What is a morphogen?
Morphogen: a protein that varies in concentration and causes different developmental responses as a result of the concentration differences
70
• What are bottle cells and what role do they play in gastrulation?
cells in the embryo that interact with epithelial cells to turn them into mesenchymal cells
71
• What are the two major signaling molecules that play a role in the formation of the primitive streak?
Wnt and TGF-Beta have been identified as likely inducing agents
72
• What tissues are derived from the hypoblast?
extraembryonic endoderm, which becomes the yolk sac endoderm
73
• What tissues are derived from the epiblast?
amniotic ectoderm AND embryonic epiblast
74
• When does gastrulation occur in humans?
At the end of the 2nd week of gestation (at this stage, the embryo has 2 flat layers, the epiblast and hypoblast)
75
• Describe the results of grafting a second dorsal lip to the blastocoel of an early amphibian embryo.
it induces the formation of a secondary embryo
76
• What factor represents the first sign of asymmetry in the mammalian embryo?
The first sign of asymmetry involves the beating of cilia around the primitive node, which induces asymmetrical beating to form a directional current
77
• Which signal molecule is expressed by the isthmic organizer?
FGF-8 and Wnt-1
78
• Describe the results to neurulation that would be caused by the absence of the planar cell polarity pathway.
neural folds remain far apart and the tube closure is absent
79
• What signaling factor family is related to the segment polarity molecules in Drosophila?
Hedgehog Family

Embryology 2019 (3 decks)

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