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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
XYY
Jacob’s Syndrome 1:1,000 males
26
45, XO
Turner Syndrome 98% spontaneously aborted
27
What is the only monosomy compatible with life?
Turner Syndrome
28
Spermatogenesis
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
What is fertilization? Where does it occur?
Fusion of male and female gametes Occurs in ampillary region of the uterine tube
30
Give details regarding sperm travelling to the uterus
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
What process do spermatozoa undergo to become competent for fertilization?
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
Fertilization phases
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
How does the egg respond to fertilization?
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
Formation of zygote
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
Indentical twins result from..
Early separation of zygote into 2 separate cell masses
36
Fraternal twins result from..
Formation of 2 separate zygotes
37
Cleavage
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
Blastocoel
First embryonic cavity Fast delivery of nutrients
39
How long does cleavage last and where?
3 days in fallopian tube
40
What occurs when the morula enters the uterus?
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
What occurs during blastocyst implantation?
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
Uterine wall layers
Endometrium- inside lining (epithelial and stroma) Myometrium- thick layer of smooth muscle Perimetrium- peritoneal covering lining the outside wall
43
Endometrium phases during menstrual cycle
1. Follicular/ profilerative phase 2. Secretory or progestational phase 3a. Gravir phase 3b. Menstrual phase
44
Follicular/proliferation phase
Regulated by estrogen Days 8ish-18ish Maturation of follicle, ovulation
45
Secretory or progesational phase
2-3 days after ovulation Regulated by progesterone Corpus luteum
46
Gravid phase
Fertilisation Endometrium assists in implantation and placenta formation Corpus luteum of pregnancy
47
Menstrual phase
No fertilisation Shedding of uterus
48
Abnormal implantation
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
Risk factors for ectopic pregnancies
Previous ectopic pregnancy Inflammation of infection Tubal surgery IUD Smoking
50
Types of ectopic pregnancy
Tubal Interstitial Cervical
51
Embryonic stem cells
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
First IVF baby
1978 Louise Brown In 2018, >8 million IVF babies
53
ART
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
IVF
Success depends on maternal age 30% conceive on first try Older women have lower chances Multiple pregnancies due to 2-4 embryos implanted
55
Risks of ART pregnancies
1. Increased prematurity 2. Low birth weight 3. Increased risk of birth defects (6% vs 4%) 4. Childhood malignancies 5. Longer-term outcomes??
56
PGD
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
Preimplantation genetic test
Preimplantation genetic diagnosis Preimplantation genetic screening Embryo biopsy DNA analysis *implantation of embryos that will develop into a healthier individual
58
PGS
Preimplantation genetic screening Genetic testing of early embryo after IVF Screens embryos of chromosomal abnormalities

202: Histology I (16 decks)

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