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Flashcards in Chapter 12 Deck (35):
1

Mitosis

cell division with 46 chromosomes in each cell—In all cells but the gamete cells

2

Meiosis

cell division of the gamete cells with 23 chromosomes in each cell ---- Spermatogenesis & oogensis so that the fertilized ovum will have a complete compliment of chromosomes (23 + 23= 46)

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gamete cells

reproductive cells - sperm and ovum (each 23)

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spermatogenesis

process of developing mature sperm

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oogensis

split and resplit until mature ovum

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autosomes

chromosomes that don't deal with the sex of the child

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who determines the sex of the child

the male

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end up with ___ sperm capable of

4 sperm capable of fertilizing mature ovum

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the ovum will not divide into truly mature ovum unless

fertilized by sperm

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ovum

Relatively large cell that can be seen with the naked eye
Chromosomes in the ovum

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Spermatoza

Overall length is ¼ that of the ovum
Travels at the rate of 1cm in 3 mins.-active swimming movements- can reach cervix in 90 seconds and fallopian tube in 3 days
Capable of fertilizing an ovum for up to 3 days
Determines the sex of the child
The head of the sperm has a covering layer that secretes an enzyme called Hyaluronidase (enzyme that helps with penetration of the ovum, also will help let other sperm penetrate the ovum)
Fertilizes the ovum usually in the outer third of the tube

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mature human sperm

once sperm penetrates ovum looses tail
200-500 million sperm release in ejaculation, released in 1 teaspoon of fluid

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conception

-Requires correct timing between the release of a mature ovum and
-Ejaculation of enough healthy, mature sperm into the vagina.
-Ovum usually lives no longer than 24 hours after oogenesis

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Fertilization

-The method by which the spermatozoa penetrates the ovum
-The enzyme (hyaluronidase) causes the zona pellucida to be penetrated
-This prevents other sperm from entering
-The ovum, in the 2nd stage of meiotic division, now completes meiosis and becomes a mature ovum
-The sperm goes through the membrane and loses its’ tail
-The nucleus of the sperm and ovum unite and cell division begins

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progression of cell division

-The union of the sperm and ovum produces a structure called the ZYGOTE, and with cell division each cell will have 46 chromosomes
-Cell division is now by mitosis and the rapid cell division is called cleavge (everytime cell division occurs)
-This structure continues to move through the fallopian BUT the size of the structure - remains the same (if it got bigger and bigger wouldn't make it up the fallopian tube)
-Each separate cell during this division is called a BLASTOMERE
-When the structure has 16 cells it is called a MORULA -at 60-72 hrs. after fertilization 16 cells

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blastocyst

The morula enters the uterus approx. 3-4 days after conception and at this point has approx. 100 cells and is now called a BLASTOCYST and remains in the uterus for 2-4 days before implantation
Inner cells of the structure will become the embryo- EMBRYOBLAST
The outer cells will become the placenta and fetal membranes-TROPHOBLAST

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trophoblast

The trophoblast (part of the blastocyst) embeds into the endometrial tissue (shed during mensis)
(now called the DECIDUA -capsularis, basalis,vera)
NIDATION: the process of implantation of the fertilized ovum into the decidua
It divides into 2 distinct layers which will become the placenta and fetal membranes (Chorion)

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decidua basalis -

where it beds into tissue

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decidua capsularis -

covers front of structure

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decidua vera -

anything else not in contact with it

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embryoblast

A compact inner layer of cells from which the embryo will develop

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Changes occur within the embryoblast and the cells form:

1.Amniotic cavity- that will gradually grow and encircle the developing fetus
2. Yolk Sac--that will feed the embryo
3. Embryonic disc--from which the fetus will develop

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yolk sac -

feeds cells until placenta takes over

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all body parts and systems develop from

embryonic disk

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if deformity look at all three layers which are

amniotic, yolk sac, embryonic disk

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embryonic disk three layers

1.ENDODERM: lining of GI and Resp. tracts, thyroid, liver, pancreas
2.ECTODERM: brain and spinal cord, pituitary gland, hair, mammary glands, tooth enamel
3. MESODERM: bone, muscle tissue, ovaries/testes, heart, spleen

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after about the 3rd week after fertilization form

layers fo embryonic disk

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stages of development

pre embryonic stage, embryonic stage, fetal stage

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pre embryonic stage

the first 14 days from conception until the primary villa appear

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embryonic stage

the beginning of the 3rd week until end of the 8th week, all body systems are established by the end of this stage

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fetal stage

the beginning of the 9th week until delivery

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when are all structures and systems formed? **

end of 3 months (12 weeks)

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will not see birth defects until

3rd week (week 8 most concerned)

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most dangerous stage of development

embryonic stage

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can determine gestational age with

crown-rump length