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general embryology > 1st week of development > Flashcards

1st week of development Flashcards

1
Q

at puberty female begins

A

monthly cycles

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2
Q

sexual cycles are controlled by

A

gonadotropin releasing hormone produced by hypothalamus

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3
Q

gonadotropin releasing hormone acts on

A

anterior lobe (adenohypophysis) on the pituitary gland that release gonadotropin

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4
Q

gonadotropin hormone are

A

FSH

LH

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5
Q

what happens at the beginning of each ovarian cycle?

A

15-20 preantral follicles are simulated to grow under the influence of FSH (Taken from the pool of primary follicles)

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6
Q

what happens when follicles become atretic

A

the oocyte and the follicular cells surrounding it degenerate and replaced by connective tissue and makes the corpus atreticum

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7
Q

FSH also stimulates

A

production of follicular (granulosa)

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8
Q

proliferating of granulosa is mediated by

A

TGF B ( differentiation factor 9)

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9
Q

theca interna and granulosa cells produce

A

estrogen

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10
Q

theca interna cells produce

A

androstenedione and testosterone

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11
Q

granulosa cells does what with secretions of theca interna

A

convert androstenedione and testosterone into estrone and 17 beta estradiol

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12
Q

estrogen function

A

endometrium enters proliferation or follicular stage
thinning of cervical mucus allow passage of sperm
anterior lobe of pituitary gland releases LH

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13
Q

LH function

A

elevates conc of maturation promoting factor causing oocytes to complete meiosis 1 and initiate meiosis 2
- release of progesterone
progesterone causes rupture and ovulation’s

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14
Q

progesterone’s are released by

A

follicular stromal cells (luteinization)

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15
Q

overview of ovulation

A

right after ovulation under the influence of FSH AND LH

  • the primary vesicular follicle grows and changes into mature vesicular follicle (Graafian follicle)
  • abrupt LH increase (end of formation of Graafian follicle) which causes primary oocyte to complete meiosis one and primary follicles to enter the preovulation mature vesicular stage
  • meiosis 2 starts and oocyte is rested at metaphase for 3 hours prior ovulution
  • stigma appears at the apex of ovary
  • prostaglandin causes muscular contraction which releases oocyte and granulosa at the site of cumlus oophorus breaks free (ovulution)
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16
Q

Some of cumulus oophorous rearrange themselves ?

A

against the zona pellucida to form corona radiata

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17
Q

corpus luteum

A

after ovulution, granulosa cells rearrange themselves in the ruptured follcile and with the theca interna are vasculrized, under LH they form a yellow pigment lutein and form corpus luteum

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18
Q

corpus luteum releases what and what does the ‘released’ product does

A

estrogen and progesterone
which makes the uterine mucosa to enter the progestational stage or secretory stage for prepare for the implantation of embryo

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19
Q

oocyte transport is done how

A

by fimbriae of the uterine tube that sweep the oocyte which has granulosa cells surrounding it
also the cilia on the epithelial lining

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20
Q

what happens when the oocyte is in the tube?

A

the cumulus cytoplasmic process let go off the zona pellucida and lose contact with oocyte.

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21
Q

fertilized oocyte reaches the uterine lumen in how many days

A

3-4 days

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22
Q

corpus lutetium reaches max development when

A

when fertilization does not occur after 9 days of ovulation

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23
Q

what happens to corpus luteum if fertilization does not occur

A

it shrinks and degenerates because of lutein cells, form a mass of fibrotic scar tissue.
progesterones release decreases causes the menstrual cycle and change into corpus albicans

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24
Q

what happens to corpus luteum if fertilization occurs

A

it makes the corpus luteum of pregnancy (graviditatis)
end of third month it is one half or one third the size
release progesterone till 3 months and diminished till after 4 month

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25
Q

degeneration of corpus luteum is stopped by what in fertilization occurs?

A

human chorionic gonadotropin release by synctiotrophoblast of the developing embryo

26
Q

fertilization occurs at the

A

ampullary region of the uterine tube

27
Q

movement of sperm from cervix to uterine tube is done by?

A

muscular contraction of uterus and uterine tube and less by its own propulsion

28
Q

trip from cervix to oviduct is?

A

30 mins or could be 6 days

29
Q

female genetial tract must undergo

A

capacitation

and acrosome reaction

30
Q

capacitation

A
  • conditioning of the female reproductive tract last for 7 hours
  • condition of capacitance occurs in the uterine tube
  • the glycoprotein coat and seminal plasma protein on the covering of the acrosomal part of spermatozoa is removed
  • interaction beween the sperm and mucusal surface of the tube
31
Q

acrosome reaction

A

occurs after the binding to zona pellucida under the zona proteins
reaches a climax with the release of enzymes like
acrosin and trypsin

32
Q

phases of fertilization

A

phase 1: penetration of corona radiata
phase2: penetration of zona pellucida
phase 3: fusion of oocyte and sperm

33
Q

phase 1

A

200 to 300 million only 500 to 300 sperms reach the fertilization site and only one capacitated penetrated the corona radiata

34
Q

phase2: what is zona

A

glycoprotein shell that covers the oocyte and facilitates and maintains the binding of sperm and induces acrosome reaction

35
Q

phase 2 binding and acrosome reaction is mediated by

A

ligand ZP3 (zona protein)

36
Q

phase 2 release of what acrosomal enzyme and what does it doe

A

acrosin allows sperm to come in contact with zona and sperm penetrates the plasma membrane of oocyte

37
Q

phase 2 permeability of zona pellucida …..

A

changes as the sperm comes in contact oocyte surface.

38
Q

phase 2 cortical granules

A

release lysosomal enzymes that changes the properties of zona pellucida (zona reaction) preventing sperm penetration and inactivate species specific receptor sites on plasma membrane of zona

39
Q

phase 3: initial adhesion of sperm and oocyte is mediated by

A

integrins on oocyte and ligand disintegrin on the sperm

40
Q

actual fusion of egg is done with what part of sperm and why

A

the plasma membrane of acrosomal head cap disintegrated during the acrosome reaction so the oocyte membrane fuses with the posterior region of the sperm head

41
Q

cortical and zona reaction

A

cortical granules changes the properties of zona to prevent sperm from binding and penetration and makes the oocyte membrane impermeable to spermatoa which prevents polyspermy

42
Q

polyspermy

A

penetration of more than one spermatozoon

43
Q

resumption of second meiotic division

A

the oocyte finishes its 2nd meiotic division, and the daughter cell with almost no cytoplasm is the 2nd polar body and the other one is definitive oocyte (22 plus X) arrange themselves in VESICULAR NUCLEUS (female pro nucleus)

44
Q

cleavage- 2 cell stage

A

at the 2 cell stage the zygote undergoes a series of mitotic divisions to form smaller cells called as blastomeres

45
Q

cleavage- at 8 cell stage

A

they form a loosely packed clump of cells

46
Q

after 3rd cleavage

A

the blastomeres increase their contact with other blastomeres through a tight junction

47
Q

after 3rd day of fertilization

A

the embryo divides to form a 16 cell morula which is inner cells and outer cells
outer cells which helps in making of placenta and inner layer are embryoblast make the embryo proper

48
Q

how blastocyst is formed

A

when morula enters the uterine tube, fluid starts accumulating through the zona pellucida and in the end the cavity of morula has accumulated fluid, now its a single cavity called blastocele, and the cell is called blastocyst and at this stage u can see 2 layers of cells embryoblast at one pole and trophoblast which makes the epithelial wall of the blastocyst

49
Q

what induces implantation

A

zona pellucida disappears

50
Q

6th day

A

the trophoblast start penetrating the uterine epithelial mucosa

51
Q

what mediates the attachment of blastocyst with the uternine wall

A

L- selectin on the trophoblast and carbohydrate receptor in the epithelial cells of uterine wall
also ecm has laminin and fibronectin

52
Q

what happens under the influence of fibroblast growth factor

A

under the influence of FGF the embryoblast differentiate into hypoblast and epiblast which are initially scattered but later at time of implantation the hypoblast take the area ventral and epiblast take the dorsal area and make a dorsal ventral polarity.

53
Q

hypoblast cells are specified to make what things

A
  • AVE (anterior visceral endoderm) which migrate to form the cranial end of the embryo
54
Q

anterior visceral endoderm secretes what

A

nodal antagonist like carabus and leftyl

that act on adjacent epiblast cells to specify the cranial end of embryo

55
Q

what happens in the absence of the inhibitors

A

the nodal establishes the primitive streak at the caudal end and that’s how the cranial caudal axis is established (5.5-6 days)

56
Q

walls of uterus

A

endometrium (inner mucosal lining)
myometrium( middle smooth muscles)
perimetrium ( outer peritoneal covering)

57
Q

3 stages of endometrium

A

follicular or proliferation stage
secretory or progestational phase
menstrual phase

58
Q

proliferation phase begins?

A

at the end of menstrual cycle under the influence of estrogen

59
Q

secretory phase begins

A

afte 3-4 days of ovulation under the influence of progesterone

60
Q

at the time of implantation mucosa of uterus is on what stage and what happens in the following events

A

the mucosa of uterus is in secretory stage, and the arteries become coiled and tissues become succulent and three distinct layers of endometrium is established

  • superficial compact layer
  • spongy layer
  • basal layer
61
Q

explain the events following if oocyte is not fertilized

A

the venules and sinusoidal space becomes packed with blood cells, diapedesis of blood can be seen in tissues. menstrual cycle begins and the compact and spongy layer expelled (3-4 days) including stroma and some glands and blood

62
Q

which part or layer of endometrium is not expelled in menstrual cycle and what’s special about it (explain its function after menstrual cycle ends)

A

the basal layer is not expelled
and it has its own arteries basal arteries and the layer has regenerative properties and it rebuilds glands and arteries in proliferative stage

general embryology (4 decks)

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