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anatomy I > Embryology Lecture 1 > Flashcards

Embryology Lecture 1 Flashcards

1
Q

What does “N” stand for?

A

The amount of DNA

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2
Q

what does 2N mean?

A

The cell is diploid. Human cell that is 2N has 46 DNA strands (chromatids)

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3
Q

What is Gametogenesis?

A

The production of gametes

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4
Q

What occurs in Meiosis I that allows for more genetic diversity?

A

Synapsis and crossing over

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5
Q

What is a chromatid?

A

One of the two strands of a chromosome, which are bound together by a centromere

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6
Q

What is crossing over

A

An important step in Meiosis I that allows for the independent assortment of genes.

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7
Q

what is a spermatogonia

A

The parent cell that is divided at the beginning of spermatogenesis.
Diploid
Reside in the testes
First divides by mitosis into primary spermatocyte

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8
Q

What is ploidy?

A

The number of chromosomes

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9
Q

New sperm cells possess what?

A

Head, mid-piece, and tail

22 autosomes and either a single X or Y

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10
Q

what are the major stages of embryogenesis

A

Cleavage, gastrulation, and organogenesis

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11
Q

what is cleavage

A

division of zygote & formation of blastocyst

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12
Q

What is gastrulation

A

Formation of germ layers

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13
Q

What is organogenesis

A

Germ layers differentiate so as to give rise to all organs in the human body

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14
Q

When are spermatogonia present

A

At birth but not active till puberty

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15
Q

Why are men able to produce more sperm throughout aging

A

the spermatogonia undergo mitosis before meiosis

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16
Q

When is K selection favorable

A

For longer living, larger animals, long time till gestation and invest more with offspring

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17
Q

What is polar body twinning

A

If secondary oocyte divides more evenly than normal then both can be fertilized by separate sperm

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18
Q

In cleavage what increases

A

The cell number increases but cells decrease in size so that the zygote remains the same size

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19
Q

What is a Morula

A

Cluster of blastomeres (16-32), tightly bound ball of cells, after the 8-stage cell cycle

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20
Q

What are blastomeres

A

Totipotent up to eight-cell stage

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21
Q

What is asynchronous

A

One cell will divide at a time

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22
Q

What is a blastocyst

A

Occurs when fluid secreted within the morula forms a blastocyst cavity

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23
Q

what are the three germ layers

A

Ectoderm, mesoderm, and endoderm

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24
Q

what forms the embryonic disk

A

Ectoderm, mesoderm, and endoderm

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25
Q

what is the difference between embryology and teratology

A

Embryology- branch of biology that deals with the development of an embryo from the fertilization of the ovum to the fetus stage
Teratology- is the study of congenital abnormalities and abnormal functions
- can account for non-birth developmental stages (ex. Puberty)

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26
Q

what is nondisjunction

A

when the separation of homologous chromosome pairs fails to happen
leads to monosomy and trisomy

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27
Q

Is it worse for nondisjunction to be in the first meiotic division or the second

A

The first
because if nondisjunction happens in Meiosis I then all four gametes will have a trisomy and monosomy
if it happens in Meiosis II then only half of the gametes will have a monosomy or trisomy (1 each)

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28
Q

Examples of monosomy

A

Turner’s syndrom (XO)

- phenotypic female

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29
Q

Example of trisomy

A 
Trisomy 21 (Down's syndrom) most common
Klinefelter syndrom (XXY)- phenotypic male
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30
Q

Where does fertilization occur

A

in the ampulla

  • Lateral 1/3 of the uterine tube
  • widest part of the uterine tube
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31
Q

What stage of meiosis is the secondary oocyte arrest in till fertilization

A

Metaphase II

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32
Q

What is the acrosome reaction

A

When the sperm binds to the zone pellucida of the secondary oocyte
- trigger the release of acrosomal enzymes (acrosin) which allow the sperm to penetrate the zone pellucida

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33
Q

What is the cortical reaction

A

After a sperm penetrates the zone pellucida then lysosomal enzymes form cortical granules near the oocyte of the cell membrane

  • these lead to a change in the oocyte cell membrane potential and inactivate sperm receptors on the zone pellucida
  • changes are called the polyspermy block
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34
Q

What is the polyspermy block

A

Changes in the cell membrane potential that inactivates sperm receptors on the zona pellucida

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35
Q

What is a male pronucleus

A
  • when the nuclear contents and central pair of the sperm enter the cytoplasm of the oocyte
  • tail and mitochondria of the sperm degenerate
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36
Q

The establishment of a functional zygote depends on whose centriole pair

A

The sperms because the oocyte loses its centriole pair during meiosis

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37
Q

when is the mature ovum present

A

after the secondary oocyte completes meiosis II

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38
Q

What is the female pronucleus

A

The nucleus of the ovum

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39
Q

what is syngamy

A

term to describe a successful completion of fertilization and formation of a zygote, when the male and female pornuclei fuse and the cytoplasmic machinery for the proper cell division exists

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40
Q

what must degenerate for implantation to occur

A

The zona pellucida must degenerate

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41
Q

Where does the blastocyst implant

A

within the posterior superior wall of the uterus, within the functional layer of the endometrium during the secretory phase of the menstrual cycle

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42
Q

What implants in the posterior superior wall of the uterus

A

The blastocyst

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43
Q

During what phase of the menstrual cycle does the blastocyst implant within the functional layer of the endometrium in the posterior superior wall of the uterus

A

The secretory phase

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44
Q

when does the blastocyst enter the lumen of the uterus

A

By the end of the first week after fertilization

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45
Q

what does a trophoblast differentiate into

A

The cytotrophoblast and the syncytiotrophoblast

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46
Q

what is gametogenesis

A

Formation of gametes

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47
Q

how much DNA content do oocytes and sperm have

A

half of the regular DNA content, haploid, 23 chromosomes , N

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48
Q

how many autosome pairs do humans have

A

22 pairs

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49
Q

How many pairs of sex chromosomes do humans have

A

1

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50
Q

What do autosomes contain

A

The genetic information for most human characteristics

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51
Q

what is a pair of similar autosomes called

A

Homologous chromosomes

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52
Q

What does Ploidy mean

A

Number of chromosomes

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53
Q

What does (N) mean

A

The amount of DNA

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54
Q

how many secondary oocytes are formed by female gametogenesis

A

1

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55
Q

how many sperm are produced by gametogenesis by males

A

4

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56
Q

When are homologous chromosomes separated

A

Anaphase I, after synapsis and crossing over events

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57
Q

When are sister chromatids separated

A

Anaphase II

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58
Q

what is a chromatid

A

One of the two strands of a chromosome joined together by a centromere

59
Q

What is independent assortment

A

When two chromosomes, normally homologous (functionally the same) pair up and exchange DNA
is heritable and increases variation

60
Q

Prophase I

A

homologous double-stranded chromosomes pair up (synapsis), and he pair forms a tetrad. crossing over occurs between maternal and paternal chromosomes

61
Q

Metaphase I

A

Homologous double-stranded chromosomes line up above and below the equator of the cell, forming a double line of chromosomes. Spindle fibers attach to the chromosomes

62
Q

Anaphase I

A

Maternal and paternal pairs of chromosomes are separated and pulled to the opposite ends of the cell, a process called reduction division. Note that at the sister chromatids remain attached in each double-stranded chromosome

63
Q

Telophase I and Cytokinesis

A

nuclear division finishes and the nuclear envelope re-form. the cytoplasm divides and two new cells are produced, each containing 23 chromosomes only. The chromosomes are still double-stranded

64
Q

prophase II

A

Nuclear envelope breaks down

chromosomes gather together (no crossing over)

65
Q

Metaphase II

A

Double-stranded chromosomes line up along the equator of the cell. spindle fibers extend from the centrioles to the chromosomes

66
Q

Anaphase II

A

Sister chromatids of each double stranded chromosome are pulled apart at the centromere. Sister chromatids (now called single-stranded chromosomes) migrate to opposite ends of the cell

67
Q

Telophase II and cytokinesis

A

Nuclear division finishes and the nuclear envelopes re-from. The four new daughter cells that are produced each contain 23 SINGLE-stranded chromosomes

68
Q

what are spermatogonia

A

parent or stem cells that produce sperm, They are diploid

69
Q

Where do spermatogonia reside

A

in the testes

70
Q

Spermatogenesis

A

Process of meiosis that primary spermatocyte undergoes to form spermatids

71
Q

what are three distinct structural characteristics sperm

A

distinctive head, mid piece, and a tail

72
Q

For spermatids to become sperm they must undergo what changes

A

Lose much of their cytoplasm and grow a long tail called a flagellum

73
Q

where do oogonia reside

A

in the ovaries

74
Q

what are oogonia

A

Diploid cells that divide to form primary oocytes

75
Q

what stage are Primary oocytes arrested in till puberty

A

from about the 5th month in utero they are arrest in Prophase I

76
Q

How many secondary oocytes are ovulated each month

A

normally one

77
Q

Do the ovaries alternate which one ovulates each month

A

Maybe

50-50 chance of releasing egg from the opposite side as the month before

78
Q

The secondary is arrested in what phase until fertilization

A

Metaphase II

79
Q

what is a polar body

A

A second cell that receives only a tiny bit of the cytoplasm

80
Q

what eventually happens to the polar

A

Eventually degenerates

81
Q

What happens if a secondary oocyte is not fertilized

A

It degenerates in about 24 hours after ovulation, still arrested in metaphase II

82
Q

what are mosaics

A

individuals who possess cells with a different number of chromosomes in them.

83
Q

What is a chimera

A

cells that have a different number of chromosomes in them but the they are from different individuals
-example mother has kids with different genes than hers because her oogonium was part of her sister

84
Q

What are some of the issues with offspring in older women

A

higher incidence of chromosomal abnormalities
prolonged dormancy of oocytes
incidence of trisomy 21 increases with maternal age
primary cause is maternal meiotic nondisjunction

  • clinical findings include: severe mental retardation, , epicanthal folds, brush field spots, simian creases, and association with a decrease in alpha-fetoprotein
85
Q

what are some of the issues with offspring in older men

A

accumulated chromosomal aberrations and mutations occurring during the maturation of the male germ cells
some evidence shows that offspring of older fathers have reduced fertility and an increased risk of birth defects, some cancers, and schizophrenia
- achondroplasia (autosomal dominant congenital skeletal anomaly characterized by retarded bone growth in the limbs with normal-sized head and trunk)
- Marfan syndrome

86
Q

what are some genetic factors to chromosome structure

A

Breakage (radiation or chemical teratogens)
Reciprocal and unbalanced translocations
deletions
duplications

87
Q

what are teratogens

A

anything that can cause a congenital birth defect

external ages that produce developmental malformations

88
Q

give some examples of teratogens

A

Radiation, prenatal infections, temperature extremes, prescription drus/dietary supplements, recreational drugs (especially alcohol), environmental toxins, maternal malnutrition or disease, mechanical forces (crowding examples to many buns in the oven)

89
Q

what are the four reasons for different responses to teratogens

A
  • Concentration and method of teratogen delivery
  • timing of exposure during development
  • variation in susceptibility due to genetic variation
  • Synergistic interactions between the teratogen and other compounds
90
Q

does only the secondary oocyte have the potential to be fertilized

A

Yes

91
Q

what are the protective layers around a secondary oocyte

A

The corona radiata and the zona pellucida

92
Q

how many sperm cells are deposited in the female reproductive tract during intercourse and how many have a chance at fertilization

A

a few hundred

93
Q

only the first sperm to ender the secondary oocyte is able to fertilize it

A

True

94
Q

what is phase 3 of fertilization

A

Sperm head and tail enter the oocyte

second mitons division with production of second polar body

95
Q

In mammals the process of nuclear fusion, whereby 2 haploid cells fuse into a single diploid cell or zygote, takes how long

A

12 hours

96
Q

What marks the beginning of embryogenesis

A

The fusion of the pronuclei
return to diploid chromosome number
mitotic divine of the zygote begins

97
Q

how long is the embryonic period

A

3rd through the 8th week of development during which all major organ system appear (Critical period)

98
Q

how long is the pre-embryonic period

A

The first 2 weeks of development when the zygote becomes a spherical, multicellular structure

99
Q

how long is human pregnancy/development

A

about 38 weeks

100
Q

what is the fetal period

A

includes the remaining weeks of development prior to birth (9-38wks)
fetus continues to grow
its organs increase in complexity

101
Q

When does cleavage occur

A

shortly after fertilization, zygote undergoes a series of divisions

102
Q

What happens to individual cell size in succeeding divisions of cleavage

A

they get smaller and smaller

103
Q

What is the Morula

A

after the third cleavage division, 8-cell stage, cells are tightly compacted into a ball

104
Q

cleave of the zygote first forms

A

2-celled blastula, then 4-stage blastula and then 8-cell blastula, morula

105
Q

what are blastomeres

A

individual cells in a blastomere

106
Q

What is a blastocyst

A

Morula forms a fluid filled blastocyst cavity
has an inner cell mass (embryoblast)
and outer cell mass (trophoblast)

107
Q

When does the zona pellucida begin to dissipate

A

When the blastocyst prepares to invade the endometrium

108
Q

What causes conjoined twins

A

Secondary fusion of ICM or development of 2 primitive streaks

109
Q

when does the blastocyst enter the lumen of the uterus

A

by the end of the first week after fertilization

110
Q

What is the cell stage that enters the lumen of the uterus

A

The blastocyst

111
Q

what is implantation

A

The process by which the blastocyst burrows into and embeds within the endometrium

112
Q

what is an ectopic pregnancy

A

Implantation of the blastocyst outside the uterine cavity
can be predisposed by condition that have caused inflammation & scarring of the uterine tubes (endometriosis, PID)
most common site is in the ampulla
clinical signs of an ETP: abnormal uterine bleeding, unilateral pelvic pain, increased levels of human chorionic gonadotropin (hCG) (but lower than expected for uterine implantation pregnancy), and a massive first-trimester bleed

113
Q

what is twin to twin transfusion syndrome

A

Twin is stealing all of the resources while the other one is starved

114
Q

what marks the second opportunity for cellular differentiation

A

Implantation

115
Q

The trophoblast differentiate on what day

A

around day 7

116
Q

the trophoblast differentiates into what two layers

A

Syncytiotrophoblast and cytotrophoblast

117
Q

What are the two layers that the embryoblast differentiates into

A

The Epiblast and the hypoblast

118
Q

what cavity is formed by the hypoblasts below the bilaminar disc

A

The yolk sac cavity

119
Q

What cavity is formed by the epiblasts above the bilaminar disc

A

The amniotic sac cavity

120
Q

what is the bilaminar disc

A

disk that marks the line between epiblasts and hypoblasts and the separation of the yolk sac cavity from the amniotic sac cavity

121
Q

Human chorionic gonadotrophin (HCG) is made by what cells

A

The syncytiotrophoblast

122
Q

what is the function of HCG

A

signals the ovary to continue to secrete hormones to maintain the pregnancy

123
Q

what day is ovulation

A

day 14

124
Q

what day is fertilization

A

Day 15

125
Q

What day is implantation

A

Day 22-24

126
Q

What day is expected menses

A

Day 28

127
Q

Most critical period overall is termed what

A

Period of organogenesis

128
Q

Where do primordial germ cells (from which gametes are descendants) originate

A

in the wall of the yolk sac of the embryo and then migrate into the gonad region

129
Q

At what week of embryonic development do primordial germ cells arrive in the ovary and differentiate into oogonia

A

at week 6

130
Q

at what month of fetal life are all primary oocytes present

A

the fifth month of fetal life

131
Q

What is the ploidy of a primary oocyte

A

46 duplicate chromosomes, 4N

132
Q

what is the ploidy of a primary spermatocyte

A

46 duplicated chromosomes, 4N

133
Q

what is capacitation

A

Unmasking of spermglycosyltransferases and removal of proteins coating the surface of the sperm
done in the female reproductive tract

134
Q

Diandric triploidy

A

an embryo with three sets of chromosomes, two of which come form the father

  • quite common
  • caused when polyspermy block fails
135
Q

When is the mature ovum formed

A

When the secondary oocyte completes meiosis II

136
Q

How long is the life span of a zygote

A

only a few hours because its existence terminates when the first cleavage division occurs

137
Q

The blastomeres are totipotent until when

A

the eight-cell stage

138
Q

what is totipotency

A

refers to a stem cell that can differentiate into every cell within the organism, including extraembryoinic tissues

139
Q

Embryoblast cells are what degree of potency

A

Pluripotent

140
Q

what is pluripotency

A

refers to a stem cell that can differentiate into ectoderm, mesoderm, and endoderm

141
Q

What is rectouterine punch (pouch of Douglas)

A

A common site for an ectopic abdominal pregnancy

142
Q

Steps in monozygotic (identical) twinning

A

cleavage divisions produce a cluster of blastomeres called a morula surrounded by a zona pellucida. the molecular mechanisms of “twinning” cause a splitting in the inner cell mass.
the twinning morula can now become monochorionic or dichorionic
- if splitting occurs after the differentiation of the trophoblast, then monochorionic twins will form
- if the splitting occurs before the differentiation of the trophoblast, then dichorionic twins will form

143
Q

Steps in dizygotic (fraternal) Twinning

A

secondary oocyte is fertilized by TWO sperm. nuclear contents and centriole pair of both sperm enter the oocyte cytoplasm. Secondary oocyte completes meiosis II, but does not form a secondary polar body. Instead, the DNA that would have been sequestered in the second polar body forms another female pronucleus. They each form their own separate cellular entities within the zona pellucida. The morula is a chimera, consisting of an assortment of cells with two different genotypes. Twinning causes splitting. can be monochorionic or dichorionic

anatomy I (7 decks)

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