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202: Histology I > 1.1: Intro to Embryology & Week 1 ✅ > Flashcards

1.1: Intro to Embryology & Week 1 ✅ Flashcards

1
Q

Embryology

A

Study of:

Development of gametes

Fertilization

Development of embryos and fetuses

Study of congenital disorders

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2
Q

Congenital disorders

A

Birth defects

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3
Q

Leading cause of infant mortality

A

Birth defects

Also major contributor to disabilities

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4
Q

Percentage of infants born with a birth defect

A

3-4%

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5
Q

Stages of prenatal development: PERIODS

A

Weeks 1-2: Germinal Period

Weeks 3-8: Embryonic period

Weeks 9-birth: Fetal Period

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6
Q

Stages of prenatal development: Trimester

A

Conception-12 weeks: 1st Trimester

Weeks 13-26: 2nd Trimester

Weeks 27-birth: 3rd Trimester

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7
Q

Risk of birth defect induction

A

Structural defects: 0-8ish weeks

Functional defects: 9-birth

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8
Q

Stages after fertilized egg til Blastocyte

A

Fertilized egg

2-cell stage

4-cell stage

8-cell stage

16-cell stage

Blastocyte

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9
Q

Oogenesis

A

Development of female gametes

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10
Q

Oogenesis steps

A

Before birth:
Growth/maturation- 2n, Oogonium, mitosis

->primary oocyte -> meiosis I -> arrest

Adolescence to menopause:
Secondary oocyte (n) and first polar body

->Meiosis II -> ootid (n) and second polar body

->Differentiation -> ovum (n) [only if fertilized]

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11
Q

What happens the first polar body during cell division?

A

Receives very little cytoplasm

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12
Q

When is meiosis II completed in Oogenesis?

A

Only if the oocyte is fertilized

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13
Q

How many oogonia are formed during development per ovary?

A

1-2 million

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14
Q

How many primary oocytes remain in each ovary by puberty

A

60,000 to 80,000

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15
Q

How secondary oocytes proceed to maturation each month?

A

About 20

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16
Q

Secondary oocytes

A

Follicles

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17
Q

Oogonium

A

Germ cell

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18
Q

How many secondary oocytes will develop further and proceed to ovulation each month?

A

1-2

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19
Q

What is it called when there is normal maturation division?

A

Euploid

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20
Q

Trisomy 21, chances of birth

A

Down Syndrome

Maternal age <25= 1: 2,000

Maternal age 35= 1:300

Maternal age 40= 1:100

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21
Q

Trisomy 18 name, births, survival chances

A

Edwards syndrome

1:5000 live births

85% lost from week 10-term

10% die by 2 months

5% live beyond 1 year

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22
Q

Trisomy 13 name, births, survival

A

Patau Syndrome

1:20,000 live births

90% die within first month after birth
5% live beyond 1 year

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23
Q

XXY

A

Klinefelter Syndrome

1:500 males

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24
Q

XXX

A

Trisomy X

1:1,000 females

25
Q

XYY

A

Jacob’s Syndrome

1:1,000 males

26
Q

45, XO

A

Turner Syndrome

98% spontaneously aborted

27
Q

What is the only monosomy compatible with life?

A

Turner Syndrome

28
Q

Spermatogenesis

A

Development of male gametes

Starts before birth, the spermatogonium (the germ cell) is 2n. By mitosis, it grows/matures into the the primary spermatocyte (2n)

In adolescence, it becomes the 2 secondary spermatocytes (n) by meiosis 1. It continues to meiosis 2 and becomes 4 spermatids (n)

Then by differentiation they become spermatozoa

29
Q

What is fertilization? Where does it occur?

A

Fusion of male and female gametes

Occurs in ampillary region of the uterine tube

30
Q

Give details regarding sperm travelling to the uterus

A

1% of sperm enter the cervix

Sperm moves to the uterine tube by muscular contractions of the uterus and uterine tube

The trip to the fallopian tube can take 30 min to 6 days

31
Q

What process do spermatozoa undergo to become competent for fertilization?

A

Capacitation and Acrosome reaction

  1. Capacitation
    -in Fallopian tube
    -epithelial interactions between sperm and fallopian tube surface
    Destabilizes acrosomal sperm head membrane to allow for penetration of egg’s outer layer
    -increases motility
  2. Acrosome reaction
    -reaction on acrosome of sperm to allow it to break into zona pellucida of egg
32
Q

Fertilization phases

A

Only one spermatozoon can fertilize an egg

Phase 1: penetration of corona radiata

Phase 2: penetration of zona pellucida
-inner acrosomal membrane dissolves
-secondary oocyte in 2nd meiotic division

Phase 3: fusion of sperm and oocyte cell membranes

33
Q

How does the egg respond to fertilization?

A
  1. Oocyte membrane alter their structure to prevent polyspermy
  2. Oocyte resumes 2nd meiotic division and forms female pronucleus
  3. Metabolic activation of egg
    -including cellular and molecular events leading to early mebryogenesis
34
Q

Formation of zygote

A

First stage of development of a genetically unique organism

Diploid (half genes from mother, half from father)

Doesn’t encode its own genome (maternal effect)

Very brief period
-followed by cleavage

35
Q

Indentical twins result from..

A

Early separation of zygote into 2 separate cell masses

36
Q

Fraternal twins result from..

A

Formation of 2 separate zygotes

37
Q

Cleavage

A

Rapid cell division
-leads to multicellular embryo

No increase in overal size- blastomeres become smaller

Compaction segregates inner and outer cells

Inner cells-> inner cell mass-> embryo proper
Outer cells-> outer cell mass-> trophoblast

Very first lineage acquisition of embryonic cells:
Zygote-> cleavage (2-cell, 4-cell, 8-cell) compaction at 8-cell-> morula -> blastula

38
Q

Blastocoel

A

First embryonic cavity

Fast delivery of nutrients

39
Q

How long does cleavage last and where?

A

3 days in fallopian tube

40
Q

What occurs when the morula enters the uterus?

A

Fluid goes through the zona pellucida, then into the intercellular space
-> forming the blastocoel-> blastocyst

Inner mass is found on one pole-> embryoblast

Outer cells flatten, forming epithelial wall-> trophoblast

Zona pellucida ruptures, allowing for implantation (day 6) -> hatching

41
Q

What occurs during blastocyst implantation?

A

Hormonal prep of the uterus

  1. Luteinizing hormone (LH) to receive the embryo
  2. Human chorionic gonadotropin (hCG) and IGF- to allow more embedding

Trophoblast cells secrete enzymes, penetrate between epithelial cells of uterine wall
-allow further penetration and embedding into endometrium

Immune system modulated to accept “foreign” embryo

42
Q

Uterine wall layers

A

Endometrium- inside lining (epithelial and stroma)

Myometrium- thick layer of smooth muscle

Perimetrium- peritoneal covering lining the outside wall

43
Q

Endometrium phases during menstrual cycle

A
  1. Follicular/ profilerative phase
  2. Secretory or progestational phase

3a. Gravir phase

3b. Menstrual phase

44
Q

Follicular/proliferation phase

A

Regulated by estrogen
Days 8ish-18ish

Maturation of follicle, ovulation

45
Q

Secretory or progesational phase

A

2-3 days after ovulation
Regulated by progesterone

Corpus luteum

46
Q

Gravid phase

A

Fertilisation
Endometrium assists in implantation and placenta formation

Corpus luteum of pregnancy

47
Q

Menstrual phase

A

No fertilisation

Shedding of uterus

48
Q

Abnormal implantation

A

Ectopic pregnancy
-blastocyst implants outside of uterus

Usually embryo will die during month 2

2% of all pregnancies

Diagnosed between 8-12 weeks

Tubal =90% of ectopics

49
Q

Risk factors for ectopic pregnancies

A

Previous ectopic pregnancy

Inflammation of infection

Tubal surgery

IUD

Smoking

50
Q

Types of ectopic pregnancy

A

Tubal

Interstitial

Cervical

51
Q

Embryonic stem cells

A

ESC

Can be isolated from human embryos and cultured indefinitely

Pluripotent- can become any cell type

Can be used for stem cell therapy

Main issues
-continuous division-> cancer risk
-potential immune rejection by host

52
Q

First IVF baby

A

1978

Louise Brown

In 2018, >8 million IVF babies

53
Q

ART

A

Assisted reproductive technology

Medical procedures, used primarily to address infertility

IVF and intracytoplasmic sperm injection (ICSI) are most common

1% of ART births have significant complications

54
Q

IVF

A

Success depends on maternal age

30% conceive on first try

Older women have lower chances

Multiple pregnancies due to 2-4 embryos implanted

55
Q

Risks of ART pregnancies

A
  1. Increased prematurity
  2. Low birth weight
  3. Increased risk of birth defects (6% vs 4%)
  4. Childhood malignancies
  5. Longer-term outcomes??
56
Q

PGD

A

Preimplantation genetic diagnosis (PGD)
-genetic testing of early embryo after IVF
-can also be used for couples carrying disease-causing mutations

Tests for known genetic disorders

57
Q

Preimplantation genetic test

A

Preimplantation genetic diagnosis

Preimplantation genetic screening

Embryo biopsy

DNA analysis

*implantation of embryos that will develop into a healthier individual

58
Q

PGS

A

Preimplantation genetic screening

Genetic testing of early embryo after IVF

Screens embryos of chromosomal abnormalities

202: Histology I (16 decks)

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