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Embryo > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Embryology

A

Study of the embryo

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2
Q

When does primordial germ cells first appear?

A

24 days

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3
Q

List the Migration route of the primordial germ cell into the gonads

A

1) Yolk Sac
2) Hindgut Epithelium
3) Dorsal Mesentery
4) Into developing gonads

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4
Q

Tetraoma

A

Growths from misdirected migrating primordial germ cells

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5
Q

What are tetraomas made of?

A

Highly misdirected differentiated tissues

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6
Q

Meiosis Prophase 1: Leptotene

A
  • Chromosomes are thread like
  • Each chromosome consists of two chromatids connected via cohesin
  • Chromosomes begin to coil
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7
Q

Meiosis Prophase 1: Zygotene

A
  • Homologous chromosomes pair (Synapsis)

- Synaptonemal complex forms

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8
Q

Meiosis Prophase 1: Pachytene

A
  • Maximum coiling
  • Tetrads
  • Crossing over begins and occurs at hot spots
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9
Q

Meiosis Prophase 1: Diplotene

A
  • Crossing over continues

- Chiasmata are well defined

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10
Q

Meiosis Prophase 1: Diakinesis

A
  • Crossing- over is complete
  • Terminalization
  • Spindle apparatus is in place
  • Nuclear membrane is disrupted
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11
Q

Meiosis: Metaphase 1

A
  • Tetrads line up along equatorial plate

- Centromeres do not divide

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12
Q

Meiosis: Anaphase 1

A
  • Homologous chromosomes consisting of two chromatids move to opposite poles
  • Chromatids are not genetically identical b/c of crossing over
  • Daughter cells will be haploid
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13
Q

Meiosis: Telophase 1

A
  • Cytokinesis occurs
  • Nuclear membranous reform and spindle apparatus disassembles
  • Chromosomes may uncoil to varying degrees
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14
Q

Meiosis: Prophase II

A
  • Chromosomes again condense
  • Nuclear membrane disappear
  • Each chromosome consists of two chromatids
  • Each daughter cell has one complete set of chromosomes (haploid)
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15
Q

Meiosis: Metaphase II

A

-Chromosomes line up on equatorial plate

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16
Q

Meiosis: Anaphase II

A
  • Centromeres divide
  • Chromosomes move to opposite poles
  • Each chromosome consists of a single chromatid
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17
Q

Meiosis: Telophase II

A
  • Chromosomes uncoil
  • Cytokinesis is complete
  • Nuclear membranes reform
  • End result is four genetically unique haploid daughter cells
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18
Q

Nondisjunction

A

Failure of homologous chromosomes or sister chromatids to separate properly

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19
Q

Aneuploidy

A

Abnormal # of chromosomes

Examples: Monosomy and Trisomy

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20
Q

Euploidy

A

Changes in number of complete sets of chromosomes

Examples: Monoploidy (Haploidy), Diploidy, Polyploidy

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21
Q

oocyte at birth

A

2 million

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22
Q

of oocyte shortly after birth

A

400,000

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23
Q

of oocyte prior to puberty

A

40,000

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24
Q

Describe the follicle and oocyte: Before Birth

A
  • Primordial Follicle

- Primary oocyte (2n4c)

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25
Q

Describe the follicle and oocyte: After Birth

A 
Primary Follicle
Primary Oocyte (2n4c)
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26
Q

Describe the follicle and oocyte: After Puberty

A

Secondary Follicle

Primary Oocyte - arrested @ metaphase I

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27
Q

Describe the oocyte associated with a Tertiary Follicle

A
  • Secondary Oocyte + Polar Body I

- 1n2c

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28
Q

What come after the tertiary follicle

A

Secondary oocyte + Polar body I

-1n2c

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29
Q

Fertilized Ovum

A
  • Occurs after the ovulated ovum
  • Fertilized ovum + Polar body II
  • 1n1c + sperm
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30
Q

Describe the structure of the mature follicle

A

1) Theca Externa- Produces Angiogensis factor
2) Theca International - with LH receptors
- secretes testosterone
3) Membrane granulosa
4) Mural granulosa cells
- Develops FSH receptors
- Synthesizes aromatase in response to FSH
- Aromatase converts testosterone into 17B-estradiol
- Estrogen stimulates formation of LH receptors on granulosa cells
5) Antrum
6) Cumulus (oophorus) cells
- Facilitates the release of ovum @ ovulation
- Doesn’t express receptors
7) Zona Pellucida
- Involved in fertilization
8) Oocyte

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31
Q

How is aromatase synthesized and what does it do?

A
  • FSH binds to FSH receptors on mural granulosa cells
  • Stimulates the synthesis of aromatase
  • Aromatase converts testosterone into 17-B Estradiol
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32
Q

Where are LH receptors located?

A

Granulosa cells of the Theca Interna

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33
Q

What is the action of LH?

A

LH stimulates the release of Testosterone

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34
Q

What does estrogen stimulate when interacting with granulosa cells of the Theca interna?

A

Cause the stimulation of LH receptors

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35
Q

When there is increased levels of cAMP in an embryonic oocyte what occurs?

A

cAMP inactivated maturation promoting factor (MPF) which causes meiosis arrest

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36
Q

LH causes closure of what type of junctions of cumulus cells

A

Gap Junctions

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37
Q

Describe the fate of the follicle after ovulation occurs

A

1) Oocyte is released (Ruptured Follicle)
2) Corpus Luteum forms
3) Corpus Albicans forms

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38
Q

Describe the events that propel the egg down the uterine tube

A

1) Fimbriae of uterine tube moves closer to ovary and sweeps across surface
- Increase in ciliation of tube epithelial cells
- Increase in activity of tubal smooth muscle cells
2) Capture of egg and surrounding follicle cells by uterine tube
3) Transport of egg occurs mostly via contractions of tubal smooth muscle

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39
Q

Describe the time it take for the egg to get to the Uterus

A

1) Slow transport in ampulla last about 72hrs
2) Rapid Transport through isthmus lasts about 8hrs: requires progesterone
3) Uterine arrival time is in about 3-4 days

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40
Q

What does a surge in LH cause?

A

Release of oocyte and corona radiata

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41
Q

Define Spermiogensis

A

The differentiation and maturation of the spermatids into motile spermatozoa (Final part of spermatogenesis)

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42
Q

Define Spermatogenesis

A

Complete process of the production of functional male gametes

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43
Q

List the stages of spermatogenesis

A

1) Primordial Germ Cells (2N)
2) Spermatogonia (2N
- Type A: Stem Cells
- Type B ~ leave mitotic cycle and enter meiosis cycle under influence of retinoic acid
3) Primary Spermatocytes (2N)
- First maturation division (meiosis I)
4) Secondary Spermatocytes (N) x 2
- Second maturation division (meiosis II)
5) Spermatids (N) x 4
- immature haploid gametes
6) Spermatozoa via spermiogensis
- haploid gametes

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44
Q

Location of Leydig cells

A

Testes

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45
Q

Function of Leydig cells

A

Produce Testosterone

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46
Q

Describe major meiosis events that occurs at each stage of spermatogenesis

A

1) First meiotic division occurs in primary Spermatocytes

2) Second meiotic division occurs on secondary Spermatocytes

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47
Q

List four major stages of spermiogenesis

A

1) Golgi Phase
2) Cap Phase
3) Acrosomal Phase
4) Maturation Phase

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48
Q

Describe the major events that occur during the four stages of spermiogenesis

A

1) Golgi Phase
- Proacromal vesicles
- Acromal vesicles
2) Cap Phase
- mature acromosome forms a cap over nucleus
3) Acrosomal Phase
- Rotation of sperm so that Acrosomal pole faces wall of seminiferous tubule cytoplasm displaced toward tail
4) Maturation Phase
- Completion of flagellum
- completion of nuclear condensation

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49
Q

Where are steroli cells (sustentacular cells) located

A

Seminiferous Tubules of the testes

50
Q

Describe the Functions of Sertoli Cells

A

1) Physical Spport and maintenance
2) Maintain and coordinate spermatogenesis
3) Secrete estrogen, inhibin and anti-mullerian factor
4) Maintain blood-testis barrier
5) Secrete tubular fluid
6) Phagocytose residual bodies of sperm cells

51
Q

Describe the relation of steroli cells to the blood testis barrier

A

They form an immunological barrier between the forming sperm cells and the rest of the body and spermatogonia

52
Q

Role of testosterone in the blood testis barrier

A

Stimulates the formation of a new blood testis barrier closer to the basal lamina

53
Q

Describe the action of LH on interstitial cells and Sertoli cells with regard to sperm cell production

A

1)LH is secreted by a anterior pituitary in response to GnRH from hypothalamus

2) LH binds to receptors on interstitial cells of leydig
- cause leydig cells to synthesize testosterone from cholesterol

3) Testosterone is carried via the blood to Sertoli cells and to secondary tissues
4) FSH stimulates sertoli cells to convert testosterone to estrogen and stimulate leydig cell stimulatory factor

5) Sertoli cells produce androgen-binding protein
- Binds testosterone and Carries it to fluid compartment of seminiferous vesicles

6)Sertoli cells produce inhibin

54
Q

List the mechanisms that propel the immobile sperm through male tract

A

1) Passive transport via testicular fluid
2) Smooth muscle contractions
3) Cilia form seminiferous tubules
- Occurring through rate testis, efferent ductules, head of epididymis

55
Q

Where does sperm maturation occur, and how long does it require

A

1) Maturation occurs in Epididymis

2) up to two weeks

56
Q

What contributions are made to semen by the seminal vesicles and the prostate gland

A

Seminal vesicles: Fructose and Prostaglandins

Prostate: Citric Acid, Zn, Mg, Phosphatase

57
Q

Optimal pH for stem motility

A

6.0-6.5 (Found in. The Cervix)

58
Q

How does the optimal pH compare to the upper Vagina

A

1) Upper Virginia has a pH of 4.3 and the optimal pH of the sperm is 6.0-6.5
2) Seminal Fluid buffers the acidity and increases pH to 7.2

59
Q

What mechanisms move sperm up the oviduct

A

1) Swimming movements

2) Peristaltic contractions

60
Q

Where does fertilization usually occur

A

Ampulla

61
Q

Describe Sperms Rapid Transport through the cervical canal

A

1) Some spermatozoa reach uterine tubes within 15-20min after ejaculation
2) Relies mostly on muscular movements of female tract
3) Sperm not as capable of fertilizing egg

62
Q

Describe sperm slow transport

A

1) Involves swimming through cervical mucous
2) 2-3mm per hr
3) Storage in cervical crypts
4) may not reach oviducts for 2-4 days

63
Q

When does ovulation occur in the ovarian cycle and what role do FSH and LH play in ovulation

A

1) Ovulation occurs on day 14 of the cycle
2) FSH cause development of the Graffian Follicle
3) LH surge causes development of corpus luteum

64
Q

What is the source of estradiol during the follicular phase and what is it responsible for?

A

1) Granulosa lutein cells secrete increased amounts of progesterone + estrogen
2) Necessary to maintain the implantation of the fertilized oocyte

65
Q

What components of the Graafian follicle form the corpus luteum

A

Residual Theca and Granulosa Cells

66
Q

What is the fate of the corpus luteum in absence of fertilization

A

1) Corpus luteum regresses due to decrease in FSH secretion via inhibin
2) Levels of progesterone and estradiol decreases which results in new menstrual phase

67
Q

Function of Inhibin

A

1) Released by granulosa cells
2) Inhibits secretion of gonadotropins (esp. FSH)
- Results in regression of corpus luteum
* *Replacement of granulosa lutein cells with collagenous scar tissue results in the formation fo the corpus albicans

68
Q

What is the function of ZP3 in Acrosomal reaction

A

1) Zona Pellucida (ZP) mediates attachment of sperm to ZP
- Glycoproteins cause an increased influx of Ca2+ through sperm plasma membrane
- Influx Na+ and Efflux H+ increase the pH

69
Q

Where is acrosin (Zona Lysin) initially found and what’s its function in fertilization

A

1) Acrosin is from the acrosome and is linked to the plasma membrane when acrosome fuses with membrane
2) Has serine protease activity and involved in penetration of ZP
- Allows spermatozoa through ZP

70
Q

Fast Block

A
  • Rapid depolarization of egg plasmalemma

- Temporarily prevents polyspermy for the egg to set up slow block

71
Q

Slow Block

A

Swelling that increases width of periviteline space cause by carbohydrate release from cortical granules

72
Q

Describe the formation of the fertilization membrane from the Vitelline membrane and cortical granules

A

1) Sperm penetrates the jelly coat
2) Lytic enzymes of the acrosomal filaments allows penetration of vitelline and plasma membrane
3) Hyaline cytoplasm flows toward sperm creating fertilization cone
4) Cortical granules with dark bodies move closer and fuse with vitelline membrane when dark bodies are released
5) Space between vitelline membrane and plasmalemme increase due to increased H20 in space
6) Dark bodies form continuous layer fused with the undersurface of the vitelline membrane

73
Q

What is the role of phospholipase C zeta in metabolic activation of egg following fertilization

A

-Phospholipase C Zeta is released by sperm and initiates release of Ca2+ within egg cytoplasm

74
Q

Distinguish between pronuclei and Zygote

A

1) Proneucleus: Nuclear material of spermatozoa or oocyte after oocyte has been penetrated
2) Male and female pronuclei fused and share common membrane

75
Q

Dating Pregnancy

A

1) Fertilization Age: Dates of embryo from time of fertilization
2) Menstrual Age: Dates age of embryo from start of mother’s last menstrual period
- 2 weeks greater than fertilization age

76
Q

Describe events that occur following fertilization and prior to implantation as the embryo travels down the oviduct

A

1) Zygote becomes metabolically active
2) Zygote begins to undergo cleavage (mitotic activity)
3) Embryo is transported down uterine tube to uterus
4) Journey takes several days
5) Embryo loses ZP prior to implantation
6) Implantation

77
Q

Describe the process of cleavage in the mammalian embryo, including the formation of the blastocyst

A

1) Zygote undergoes mitotic division to form an 8 cell embryp
2) Cell division continues and compaction occurs
- Outer blastomere adhere via gap junctions facilitated by E-cadherins and Ca2+-dependent CAMs
- Out blastomere lose their individual identity
3) Water is transported into the ball of cells
- Occurs 4 days after fertilization
- Results in the formation of a blastocell as a result of cavitation
- Requires Na and K-ATPase transport
4) Embryo is referred to as blastocyst at this stage (58 cells)

78
Q

Describe and compare trophoblast cells and cells in the inner cell mass

A

Trophoblast = outerlayer of cells of blastocyst
-Forms extraembryonic structures including placenta
Inner cell mass = inner mass of cells of blastocyst
-Forms embryo proper and some extraembryonic structures

79
Q

Define Blastocoel

A

Fluid filled cavity of blastula and results from cleavage of oocyte after fertilization

  • Creates polarization
    - Embryonic Pole = @ location of inner cell mass
    - Abembryonic Pole = Marks opposite pole
80
Q

Compare genetic control of cleavage between mammalian and non-mammalian embryos

A

1) Non-mammalian vertebrates
- Early controls of cleavage via gene products transcribed from maternal genome
- Embryonic gene products often don’t appear until after blastulation

2) Mammalian Embryo
- Mammalian gene products are produced but generally degraded by 2 cell stage of development
- By the four cell stage, most transcription is via embryonic genome

81
Q

Describe the methylation cycle in mammalian gametes and embryo

A

1) DNA of mature eggs and sperm is highly methylated
2) Demethylation of maternal and parental genomes occurs shortly after fertilization until the early morula
3) Remethylation of inner cell mass occurs until late blastocyst state
4) Methylation levels fall after primordial germ cells enter genital ridges
5) Remethylation occurs later during gametogenesis and may lead to maternal/parental imprinting

82
Q

Cdx-2

A

Essential for trophoblast cell differentiation and antagonistic toward Oct-4

83
Q

Oct-4

A

Oocyte and Zygotes express in order to permit cleavage to proceed to 2 cell stage along with Oct-4

84
Q

All morula cells express what?

A

Oct-4

85
Q

Nanog

A

Produced by inner cells in late morula stage and maintains integrity of inner cells along with Oct-4

86
Q

What occurs when Nanog is absent

A

Inner cells differentiate into ectoderm

87
Q

What occurs when Oct-4 is absent

A

Inner cells differentiate into trophoblast

88
Q

Sox-2

A

-First expressed in 8 cell stage along with Oct-4 it helps control regulation of genes involved in differentiation

89
Q

Define Regulation

A

Refers to ability of embryo to compensate for removal of structures or for addition of structures

90
Q

Barr Bodies

A

Inactive X chromosome

-Tells us about the basis for the sex chromatin

91
Q

Define regulation

A

Refers to ability of embryo to compensate for removal of structures or for addition of structures

92
Q

Fraternal (dizygotic) twins

A

Fertilization of two ovulated eggs and mechanisms of formation involves endocrine control of ovulation

93
Q

Identical (monozygotic) twins

A

Product of a single fertilized egg. Unite from subdivision and splitting of a single embryo

94
Q

Conjoined twins

A

Incomplete separation of portions of an embryo although two embryos take shape.
They are joined by a tissue bridge

95
Q

Parasitic Twin

A

Complete portion of body protrudes from the body of an otherwise normal host twin

*Partial secondary fusion of originally separated portions of inner cell mass or formation of two primitive streaks in single embryo

96
Q

Bateson’s Rule

A

Duplicated structures that are joined are marrow image of the other

97
Q

Define Homeobox-Containing genes

A

Genes that contain a highly conserved sequence of 180 nucleotides called the homeobox which codes for the 60 amino acid homeodomain transcription factor proteins

98
Q

Homeobox vs homeodomain

A

Homeobox = codes for the 60 amino acid homeodomains found in homeodomain transcription factor proteins

Homeodomain: Made up of 60 AA

99
Q

What role do homeobox-containing genes play in vertebrate development

A

Cranio-caudal segmentation, not only along main body axis but with in the development of many organs

100
Q

In regards to homeobox-containing genes, what differentiate loss-of-function mutations and gain-of-function mutations

A

1) Loss-of-Function: Result in posterior to anterior transformations
2) Gain-of-function mutations: Result in anterior to posterior transformations

101
Q

Describe the organization of the human Hox complex

A

1) Genes on the 3’ ends of each of the complexes are expressed eariler and more anteriorly than those on the 5’ right

102
Q

Destruct Homeobox-Containing Genes: T-box genes(Tbx), Helix-loop-helix genes, Forkhead (Fox) genes

A

1) T-box genes (Tbx) - Plays a role in inducing mesodermal germ layer and in coordinating the outgrowth of the arm or leg
2) Helix-loop-Helix genes: Code for helix-loop-helix transcription factors that are involved in homodimerization and heterodimerization and important for myogenesis
3) Forkhead (Fox) genes: Type of Helix-Loop-Helix family and is expressed in many developing organs through the the body

103
Q

Compare the Hox gene complex in mammals to that in Drosophila

A

1) The mammalian Hox genes are similar in sequence to the homeotic genes found in Drosophila, and they are in the same order

104
Q

Describe the helix-loop-helix and zinc finger transcription factor motif

A

1) Helix loop helix: Basic regions of proteins bind to DNA; Can be found as hetero or homodimer; important for myogenesis
2) Zinc Finger: Proteins have Zinc ions bound to polypeptide chain that cause the chain to form finger-like projections that can be inserted into the DNA helix

105
Q

List the characteristics of Sox genes and WT1

A

1) Both are Gene families for Zinc Fingers
2) Sox genes: Transcribe transcription factors that have a high-mobility group domain that binds to minor groove on DNA rather than major groove; Involved in sex determination
3) WT1: Important in development of embryonic kidney and the adult kidney. Knock out WT1 cards Wilms tumor in children

106
Q

What is a morphogen

A

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

107
Q

Describe the function of each of the following sets of genes in the development of Drosophila body plan: Egg polarity genes, gap genes, pair-rule genes, segment-polarity genes, antennapedia-complex genes, and bithorax complex genes

A

1) Egg Polarity Genes: These genes are transcribed into mRNA in the ovary during egg formation and are translated into proteins after fertilization (genetic maternal effect); Establish the dorsal-ventral axis and anterior posterior axis
2) Gap genes: Delete adjacent segments
3) Pair-rule genes: Delete same part of pattern in every other segment
4) Segment-polarity genes: Affect polarity of segment
5) Antennapedia complex: Affects development of head and thorax
6) Bithorax Complex Genes: Affects development of posterior thorax and abdominal segments

108
Q

SIGNALING FACTOR FAMILIES

A

1) Transforming Growth Factor-B Superfamily
2) Fibroblast Growth Factor Family
3) Hedgehog Family
4) Wnt Family

109
Q

True or False; Hedgehog and Wnt families are apart of the growth factor family

A

True

110
Q

Fibroblast growth factor and TGF-B factor receptors possess what type of receptor activity?

A

1) Protein Kinase Activity
2) Receptors for FBF possesses tyrosine kinase activity
3) Receptors for TGF-B factors possesses serine/theronine kinase-activity

111
Q

List examples of signaling pathways

A

1) Delta Notch
2) Receptor Tyrosine Kinase Pathway
3) Hedgehog pathway
4) Wnt Signaling pathway
5) MicroRNA pathway
6) Retinol Pathway

112
Q

Describe the Delta Notch Pathway

A

1) Delta binds to notch
2) The complex binds to suppressor of hairless
3) Notch-Deltex-Suppressor of hairless complex binds to enhancer of split
4) Resultant inhibitory signal expresses Gene expression

113
Q

Hedgehog pathway

A

1) hedgehog protein complexes with cholesterol
2) Shh-cholesterol is trans located to cell surface via action of Dispersed
3) Shh-cholesterol inhibits the inhibitory actions of patched on smoothened on the target cell
4) Uninhibited smoothened signals the release of transcription Gli form a complex on Microtubule
5) Gli trans locates to the nucleus and influences gene expression

114
Q

What occurs in the absence of Wnt?

A

B- catering are bound to an intracellular destruction complex within the target cell

115
Q

Pathway for Wnt signaling

A

1) Wnt molecule (ligand) binds to Frizzled on target cell
2) Frizzled interacts with intracellular disheveled
3) Disheveled prevents the degradation of the B-catenins by the destruction complex
4) B-catenins translocations to nucleus and activates transcription factors

116
Q

What are the two major groups of miRNA

A

Piwi-interacting RNAs: Acts during gametogenesis (esp. Spermatogenesis)

Endogenous small interfering TNAs (Endo-siRNAs): Expressed in somatic tissues throughout development

117
Q

Roles of Dicer and Argonauts (AGO) Proteins

A

1) Dicer cleaves miRNA precursors

2) AGO binds to miRNA and creates a complex and then cleaves target mRNA

118
Q

What is another name for retinol

A

Vitamin A

119
Q

Describe the Retinol Pathway

A

1) Retinol binds to retinol-binding protein (RBP)
2) Complex binds to membrane RBP
3) Retinol is released into cytoplasm and binds to a CRBP 1
4) Complex trans locates into nucleus
5) Retinoic acid binds to Dimer RCR-RAR which binds to RARE which activates transcription

120
Q

Uterine Tube Transport Timeline

A

1) End of day 1: 2-cell stage in isthmus
2) Day 3: Morula is in the isthmus and corona radiata is lost by this time
3) Day 4: Blastocyst is in the uterus
4) Day 5: Loss of Zona Pellucida
5) Day 6: Beginning of implantation

121
Q

What long is the Zona Pellucida around?

A

Until the developing embryo reaches the uterus and then shedding of the ZP is accomplished through blastocyst hatching

Embryo (3 decks)

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