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Block 1 Week 3 > Human Embryology 2 > Flashcards

Human Embryology 2 Flashcards

1
Q

why do eggs need to accumulate resources before fertilization?

A
  • initial cell divisions immediately after fertilizations are done entirely by egg
  • doesn’t bring in outside material, so accumulates proteins, energy resources in cytoplasm to prepare
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2
Q

Where does egg arrest in women?

A
  • in prophase 1 as a baby

- in metaphase 2 until reach puberty

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3
Q

Polar body 1 and 2 expulsion occur? Is chromosme count equivalent in 1 vs 2 polar body?

A

1) after meisosis 1
2) after meisos 2, when egg is fertilized

-no, first polar body will be diploid, second will be haploid

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4
Q

polar bodies contribution to embryonic process?

A
  • different by species, some polar bodies don’t contribute to baby others contribute to the protection of developing fetus
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5
Q

oogenesis general steps:

A

1) oogonium (2n) becomes primary oocyte
2) primary oocyte (2n) grows & matures undergoes meisosis 1
3) secondary oocyte (1n) + first polar body, they undergo meisos 2
4) fertilization, meiosis 2 complete, get ootid & second polar body
5) differentiation occurs & get ovum

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6
Q

How often is an oocyte released from ovary?

A

-once a month in post-puberty women

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7
Q

sperm vs egg differences

A

1) stay in syncytium until maturation complete

2) complete meiosis

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8
Q

sperm vs egg differences

A

1) sperm stay in syncytium until maturation complete
2) sperm complete meiosis & continually make more cells
3) eggs don’t finish meiosis 2 until fertilization; have a set number of oocytes are born with

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9
Q

oocyte movement overview

A

1) each month (at ovulation), oocyte released from ovary
2) fimbriae of uterine tube sweep over the ovary (usually the two are separate)
3) oocyte is brought into the ampulla of the uterine tube
4) ovary travels through uterine tube towards the Uterine Cavity

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10
Q

How specifically does oocyte get into the fallopian tube?

A

1) secondary oocyte has a vesicle sticking out called stigma which pops the wall of the ovary when timbre of tube is close
2) follicular fluid from the 2 oocyte flows into the tube, cilli push secondary oocyte with it, then the fluid pulls oocyte rest of way through tubes to the uterus

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11
Q

how sperm fertilize egg?

A

-sperm enters at end of vagina, has to go through cervix then all theway to meet egg in middle of fallopian tube (pretty far)

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12
Q

Fertilization and the cervix?

A

-usually cervix blocked by thick layer of mucus, during ovulation becomes thin layer of mucus so the sperm can break through and enter uterus

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13
Q

Uterus structure and embryonic development?

A
  • uterus structure is important for new embryo
  • has uterian glands, dense vascularization, veins, arteries, and spaces inbetween with lacunae
  • makes good place to receive embryo
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14
Q

lacunae?

A

spaces that fill with blood in the uterus to help keep embryo nourished

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15
Q

What are they Female Reproductive organs?

A

Uterus, Uterine Tubes and Ovaries

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16
Q

What 2 hormones control gametogenesis?

A

1) Steroid hormones
2) Peptide hormones
- both have similar regulatory loops sperm & oocyte formation

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17
Q

steroid hormones?

A
  • cholesterol derivatives
  • include testosterone, estrogen, & progesterone
  • act via series of nuclear receptors (receptors that lie within the cell, not membrane-bound)
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18
Q

nuclear receptors?

A

receptors that lie within the cell, not membrane-bound

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19
Q

Peptide hormones

A

including:
1) follicle-stimulating hormone (FSH)
2) luteinizing hormone (LH)
3) gonadotropin-releasing hormone (GNRH).

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20
Q

Why/how release same hormones w/ same feedback loops but get 2 different gametes? What happens if sperm gametes don’t reach testes?

A
  • cell components in ovary & testes are diff
  • interpret hormonal signals in diff ways
  • all gametes are identical before reach testes/ovaries
  • once reach…differentiation occurs
  • if male gamete does NOT reach, testes, then will mature into an oocyte, require testes signals to become sperm
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21
Q

The three major naturally occurring forms of estrogen in women are:

A

1) Estradiol
2) Estriol
3) Estrone

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22
Q

Me stroll cycle and hormone levels?

A

1) beginning, uterine wall very thin
2) LH surge is signal for uterine wall to become thick & ovulation to occur
3) if embryo received wall will continue to grow, if not receieved go through menstrual cycle returns to thin uterian wall

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23
Q

When does LH surge occur?

A
  • production of secondary oocyte (end of meiosis 1), right before ovulation occurs
  • signals for ovulation to happen
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24
Q

sexual intercourse-mediated fertilization?

A

1) how oocyte & sperm normally meet
2) erect penis inserted into vagina
3) ejaculation of sperm at cervix lets sperm enter uterus & uterine tubes
4) 100 million sperm per ml of ejaculate ( 2 -6 ml; ~400 x10^6)

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25
Q

How much sperm per ejaculation

A
  • 100 million sperm per ml of ejaculate -usually 2 -6 ml so:
  • ~400 x10^6 sperms
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26
Q

How long does it take for sperm to meet egg? Sperm lifespan in normal humans?

A

1) 30min- 2hr to reach egg

2) life span is short, sometimes can maintain viability for couple days is rare

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27
Q

Sperm lifespan in other species?

A
  • if sperm has longer life span, can be released into uterus, then days fertilize egg,
  • some species store sperm in inert stage; save for later better procreation states then activate & fertilize
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28
Q

Steps for spermatozoa maturation, activation and fertilization?

A

1) mature sperm form, stored in epididymis in immobile state
2) activation when ejaculate get mobile sperm
3) Capacitation in proximity to the oocyte
4) Acrosome reaction when meet egg

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29
Q

Capacitation

A
  • destabilisation of acrosomal sperm head membrane allows greater binding between sperm & oocyte
  • membrane changes in sperm occur, hyperactivity facilitates passage through corona radiata to access the Zona Pelucida
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30
Q

Acrosome reaction

A

1) sperm binds zona pelucida (at ZP3) & release hydrolytic enzymes stored in acrosome vesicle
2) these enzymes degrade Zona Pelucida
3) allows sperm movement into perivitelline space, fusion with Oocyte’s plasma

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31
Q

zona pelucida

A

the thick transparent membrane surrounding a mammalian ovum before implantation
-contains glycoprotein ZP3 on extracellular matrix

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32
Q

perivitelline space

A

-space between the zona pellucida and cell membrane of an oocyte or fertilized ovum

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33
Q

complications sperm can experience when released into uterus?

A

1) immune cells can attack sperm (see as foreign)

2) sperm has to move against the flow of liquid trying to push egg from Fallopian tube into the uterus

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34
Q

Oocyte response after fusion with sperm?

A

1) Oocyte Activation
2) Fast Blockade
3) Slow Blockade
- Oocyte starts fast, needs to block further entry of other sperm or get polyspermy and get fucked up chrom. #

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35
Q

Oocyte Activation

A

1) once sperm enters oocyte
2) creates blockade against polyspermia
3) completion of Meiosis 1

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36
Q

oocyte fast blockade?

A

-membrane depolarizes; prevents fusion of new sperm membranes even if already in the space

37
Q

oocyte slow blockade?

A

1) Ca2+ influx leading to Oocye vesicle secretions that inactivate ZP3 (glycoprotein on ECM of zone pellucida)
2) prevents acrosome rxt

38
Q

ZP3

A
  • a glycoprotein on the zona pellucida’s extracellular matrix
  • receptors on sperm plasma membrane attach to ZP3
  • contents it’s acrosome, (hydrolytic enzymes) spill out & degrade zona pellucida near sperm head
39
Q

what happens when have fussion of one Sperm and the Oocyte (5 general steps?

A

1) sperm uses ZP3 mediated binding to bind ZP
2) Release acrosome vesicle enzymes, to digerst ZP.
3) move into perivitelline space,
4) fusion w/ Oocyte’s plasma membrane
5) sperm head, neck and tail enter oocyte

40
Q

Mitochondria of the sperm

A
  • entire sperm enters the oocyte including mitochondria
  • BUT mitochondrial proteins enter ubiquinated…so are automatically sent to proteomes for degradation therefore only express mothers mitochondrial DNA
41
Q

fertilization steps (x5)

A

1) fertilization occurs in the ampulla of fallopian tube
2) sperm passed through corona radiata
3) acrosome of sperm breaks down zona pellucida. Zona rxt prevents other sperm from entering oocyte
4) head & tail of sperm enter the oocyte
5) pronuclei combine to form zygote w/ 46 chromosomes. cleavage begins

42
Q

how estrogen + progesterone, and progesterone only contraceptives work?

A

1) block ovulation
2) block uterus endometrium maturation (change lining of uterus, so can’t implant egg into uterus)
3) reduce sperm passage through cervix (increase mucus at cervix)
* ONLY WOMEN USE*

43
Q

what is ovulation exactly?

A

release of an egg from the ovaries into the fallopian tube and eventually uterus

44
Q

concerns about implant birth control?

A

-can potentially cause inflammation & rejection

45
Q

male contraceptives?

A
  • hormone processes are same for sperm & egg production yet only women take BC
    1) vasectomies
    2) Vasalgel
    3) male BCP
46
Q

vasectomies

A
  • block epidermis and prevent relase of new sperm
  • sperm is made but then degraded
  • not popular cuz is permanent
47
Q

Vasalgel

A
  • daily gel that stops sperm production
  • polymer injected into sperm-carrying tubes; through the scrotum
  • blocks sperm & is reversible through a second injection that dissolves it
48
Q

male birth control pills?

A

-entering phase two clinical studies
issue: the sperm-suppressing hormone changes that the drug induces clear the body too quickly, would require more
than a once daily dose
-once daily dose only last 18hr

49
Q

assisted reproductive technologies?

A

1) cryopreservation: freeze sperm & egg
2) surrogate Mothers
3) artificial insemination
4) in Vitro Fertilization and Embryo Transfer (IVF)
5) intracytoplasmic Sperm Injection (inject sperm directly into eggs)

50
Q

Who did first IVF fertilization?

A

Sir Robert G. Edwards, Louise Brown was first test tube baby in 1978

51
Q

IVF process?

A

1) Super ovulate get lots of eggs, put in petri dish, add sperm
2) Sperms active & mobile, fertilize egg
3) blastocyst screen and check for genetic defects,
4) choose 1 early embryo & deposit in back of uterus (normal implantation area)

52
Q

assisted reproductive technologies?

A

1) cryopreservation: freeze sperm & egg
2) surrogate Mothers
3) artificial insemination
4) in Vitro Fertilization and Embryo Transfer (IVF)
5) intracytoplasmic Sperm Injection (inject sperm directly into eggs)

53
Q

Who did first IVF fertilization?

A

Sir Robert G. Edwards, Louise Brown was first test tube baby in 1978

54
Q

IVF process?

A

1) Super ovulate get lots of eggs, put in petri dish, add sperm
2) Sperms active & mobile, fertilize egg
3) blastocyst screen and check for genetic defects,
4) choose 1 early embryo & deposit in back of uterus (normal implantation area)

55
Q

Prenatal vs Postnatal

A 
Prenatal
Embryonic: First 8 weeks, day 1-56
Fetal: After 8th week until birth
Postnatal:
Infancy, childhood, puberty, adulthood
56
Q

First week of pregnancy?

A

1) fertilization
2) cleavage
3) blastocyst

57
Q

Cleavage of the zygote definition?

A

-the rapid, multiple rounds of cell division that turn zygote into blastula

58
Q

Cleavage of the zygote mechanism?

A

1) two cell stage
2) 4 cell stage
3) 8 cell stage
4) Morula blastomers
5) (first differentiation event) tropoblasts or early blastocyst
6) late blastocyst develop embryo blast (or ICM)

59
Q

blastomere

A

a cell formed by cleavage of a fertilized egg

60
Q

Morula?

A
  • contain identical cells, each has potential to give rise to full new embryo
  • still contains zone pellucida around it, haven’t excepts help from sperm yet, done this on own
61
Q

first differentiation event?

A
  • from identical Morula blastomers to Trophoblasts

- loose the zone pellucida

62
Q

Trophoblasts

A

are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta

63
Q

late blastocysts?

A

-embryoblast or inner cell mass (ICM ) forms in blastocysts

64
Q

Animal vs Vegetal Pole

A

animal pole: used for implantation, directly contacts uterus, acts as anchor for attachment
-was where inner cell mass was

vegetal pole=the opposite side

65
Q

embryoblast or inner cell mass (ICM )

A

generate all tissue of futrure embryo, characterized by many TF like OCT4 (key stem cell gene)

66
Q

First step of Implantation?

A
  • blastocyst attachment to endometrium*
    1) trophoblast attaches the blastocyst (through animal pole) to the endometrium
    2) trophoblast divides into a syncytiotrophoblast (syncytium) and cytotrophoblast
    3) Syncytiotrophoblast layer invades endometrium pulling embryo with it
67
Q

What day of pregnancy does attachment happen?

A

day 6

68
Q

Types of trophoblasts?

A

1) syncytiotrophoblast invade endometrium

2) cytotrophoblast are all the rest

69
Q

What happens in stage 1, 2, 3 and 4 of pregnancy?

A

Stage 1: Zygote formation
Stage 2: days 2-3, 2 to 16 cells
Stage 3: morula–> trophoblasts–> ICM–> mature blastocyst (days 4-5)
Stage 4: Attach to posterior wall of the uterus (days 5-6)

70
Q

first step in Implantation (post attachment)?

A

Embryoblast (ICM) forms a bilaminar, embryonic disc:

1) Epiblast (on top)
2) Hypoblast (on bottom)

71
Q

embryo proper?

A
  • the amniotic membrane, yolk sac & allantois

- compared to the fetal part of the placenta

72
Q

Epiblast & Hypoblast contribute to?

A

Epiblast: embryo proper,
Hypoblast: fetal part of the placenta, make endoderm, but not actual fetus

73
Q

Embryoblast/ ICM cell types?

A
  • initially though all cells were homogenous pluripotent cell population (similar to morulas)
  • actually contains cells with different expressions, which segregate to generate epiblast and hypoblast
74
Q

How distinguish between cell types in embryo blasts/ICM?

A
  • diff trxn factors cause diff proteins to be expressed in the two cell types:
    1) oct6 expression= hypoblasts, 2) hyp4 expression= epiblasts
75
Q

Implantation days 8-9 (steps x4)

A
  1. Invading Syncytiotrophoblasts break down glands & vessels.
  2. Amniotic cavity formed between the cytotrophoblast and the epiblast.
  3. Embryonic disc lies between amniotic cavity and exocoelomic cavity/primary umbilical vesicle
  4. Hypoblast derived endoderm lines the umbilical vesicle, and this extraembryonic endoderm generates extraembryonic mesoderm
76
Q

Epiblasts make?

A
  • ectoderm
  • mesoderm
  • endoderm
77
Q

hypoblasts make?

A
  • extra embryonic tissue
  • lines umbilical vesicle
  • creates protective sack
78
Q

Implantation days 10-12 (steps x4)

A
  1. Conceptus completely embedded in uterine wall. Endometrial scar corrected by a closing plug
  2. Hypoblast derived endoderm lines the umbilical vesicle
  3. Primordial uteroplacental circulation: communication of the eroded endometrial capillaries with the lacunae provides resources to nourish the early embryo
  4. Endometrial capillaries around embryo become congested & dilated to form maternal sinusoids
79
Q

maternal sinusoids

A

thin-walled terminal vessels that are larger than ordinary capillaries

80
Q

Embryotroph

A

Maternal blood, and uterine gland debris accumulated in lacunae, provide food/ resoruces to nourish early embryo

81
Q

day 13/14 of pregnancy (implantation( x4?

A

1) Endometrial epithelium plug has been repaired;
2) Formation of small secondary umbilical vesicle;
3) Large extraembryonic coelom, surrounds the umbilical vesicle and amnion;
4) Primary Chorionic Villus. The first stage towards chorionic villi of the placenta

82
Q

Chorionic Sac Formation?

A

The extraembryonic coelom splits the extraembryonic mesoderm into two layers:

1) Extraembryonic somatic mesoderm, lining the trophoblast and covering the amnion
2) Extraembryonic splanchnic mesoderm, surrounding the umbilical vesicle

83
Q

Placenta

A

feto-maternal metabolic interchange organ

84
Q

The connecting stalk appears at where?

A

at the chorionic vesicle stage

-it is extraembryonic somatic mesoderm that connects the caudal end of the embryo to the Chorion

85
Q

what 2 layers forms Chorion? What is the chorion?

A

fetal part of the placenta; noutermost fetal membrane, forms wall of chorionic sac

1) extraembryonic somatic mesoderm
2) trophoblast

86
Q

chorionic sac

A

The embryo, amniotic sac, and umbilical vesicle are suspended in this sac

87
Q

Ectopic pregnancies examples? How occur?

A

-abdominal

  • many ways
    1) ovary fall out in transfer
    2) not enough cilia to push through to uterus
88
Q

Abdominal pregnancies?

A

Higher maternal mortality, baby mortality and morbidity compared to other ectopic pregnancies
-Occasionally
lead to a healthy delivery

89
Q

Most common place for fertilization of the egg?

A

ambula of tube (near fibers of tube)

Block 1 Week 3 (8 decks)

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