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44 Cards in this Set

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normal female somatic cells contain __ copies of the X chromosome
2 copies of X
normal male somatic cells contain __ copies of the X chromosome
1 Copy of X
This occurs in female cells so that males and females have the same number of X chromosomes:
inactivation of X chromosome
When does X-inactivation occur?

Does it matter which X is inactivated (paternally/maternally derived)?
X-inactivation occurs during the 1st week of embryonic development
Where can the barr body be seen in the cell?
Periphery of nuclear membrane
When can the sex of a zygote be determined?
End of 1st week- beginning of 2nd week.
What does MIS stand for? What does it do?
MIS: Mularian Inhibiting Substance

- It allows Y chromosome to induce change so that the zygote becomes male, secreation of TDF occurs (testes develop)
Primordal cells arrive at the ovary at what week?
Week 4
if testes develop when does that occur?
7th week
Oogonia become ---
Primary oocytes
The fetus has all its primary oocytes by what month?
5th month
Are any oogonia present at birth?
NO
True or false: At birth, a female has her entire supply of primary oocytes?
True!
When primary oocytes are formed they remain frozen (Diplotene stage) in this phase...until what age?
Prophase I until puberty
Each month this many primary oocytes mature...

how many reach full maturity?
15

usually only one reaches full maturity, completing meiosis I
When a primary oocyte completes meiosis I, what does it produce?
A secondary oocyte and 1st polar body
The secondary oocyte will complete meiosis II...
Only if it is fertilized, otherwise it remains in metaphase II
Does the 1st polar body undergo a second divison?
it can creating 2 polar bodies, however it usually degenerates.
What is the product of a secondary ooctye?
- It produces an mature oocyte (egg) + 1 polar body
If the secondary oocyte does not get fertalized...
cell degenerates 24 hours after ovulation
Where does fertilization occur?
In the uterine tube
Up to how many secondary oocytes are ovulated in a woman's life?
480 (40 x 12)

- 12 secondary oocyte ovulations per year
The process to produce mature sperm is divided into 3 phases:
1. spermatocytogenesis
2. meiosis
3. spermatogenesis
Primary spermatocytes arise from:
spermatogonia
There are 2 types of spermatogonia:
Type A --undifferentiated stem cells that produce more A and B cells

Type B --undergo further mitosis to form more sprmatogonia OR may enter meiosis to form Primary spermatocytes
Spermaids undergo ___ to become ___
- spermatogenesis

- spermatozoa (sperm)
Name the 3 parts of sperm
- Acrosome
- Nucleus
- Flagella
Describe acrosomal formation
- large membrane-bound vesicle that overs the anterior two-thirds of the sperm nucleus (specialized lysosome)
What is contained in the acrosome?
Enzymes that aid in penetrating the egg's corona radiata and zona pellicida
Fertilization occurs
in uterine (fallopian) tube
Clevage:
mitotic cell divison of the zygote that form cells called blastomeres

*Embryo size remains the same, but blastomeres become smaller
Morula:
A ball of 12 or more blastomeres

- 3 or 4 days after fertilization
- Enters uterus from uterine (fallopian) tube
Blastocyst:
Fluid-filled cavity forms inside morula
Describe the inner cell mass (embryoblast) of the blastocyst
gives rise to embryo and some extraembryonic tissue
Describe the trophoblast of the blastocyst
a thin outer layer of cells that enclose the embryoblast and blastocyst cavity; contributes to formation of placenta (connection b/w developing baby and mom)
how can one determine the size of the embryo
by measuring the crown-rump length (CRL): the tip of the cranium to heel of feet
An embryo refers to:
A developing human that extends to the end of week 8

*All major structures are present, but only heart and circulation are functional
Conceptus refers to:
both the embryo and its adnexa (appendages, amnion, chorionic sac, umbilical vesicle/yolk sac) or associated membranes
Amnion (amniotic sac):
the innermost extraembryonic membrane, enveloping the embryo and contains amniotic fluid
Chorionic [gestational] sac:
multilayered, outermost fetal membrane

- also called membrana serosa
- becomes part of fetal placenta
primordium:
refers to earliest stage of development of an organ or structure
Fetus refers to
developing human from week 9 to birth
abortion:
premature stoppage in development of embryo or fetus

* earlier than 24 weeks
Miscarriage:
refers to spontaneous abortion of fetus and its membranes before middle of second trimester

*First 20 weeks