Intro to Embryology Flashcards
What is the process called where diploid cells give rise to haploid cells?
Meiosis
How many cell divisions happen in meiosis?
Two cell divisions
Meiosis I and Meiosis II
Meiosis gives you how many daughter cells?
Four
How many chromosomes are in each new daughter cell after meiosis?
23 chromosomes and one sex cell
What is the process by which germ cells (or gametes) are produced and mature?
Gametogenesis
How many chromosomes do gametes have?
23
Female gamete is an
Egg
The male gamete is a
Sperm
When a female and a male gamete unite, they form a what?
Zygote
How many chromosomes in a zygote?
46
Oogenesis produces what?
female gametes (ova/egg)
In what week of embryonic life do primordial germ cells arrive in the ovary from the yolk sac?
5th week
Is proliferation of the oogonia- female stem cells (rapid/slow) during fetal life?
Rapid
When does the meiosis of primary oocytes begin?
Before birth- but stops before the first division is complete and remains in the arrested phase until puberty
Are primary oocytes vulnerable to damage as they age?
Yes! Syndromes are more likely
How many eggs will mature during a woman’s life?
400-500
The pituitary gland produces which important hormones in the growth of oocytes and formation of zona pellucida?
Follicle-stimulating hormone FSH and Luteinizing Hormone (LH)
The maturation of oocytes takes a primary oocyte and divides it into what two things?
Secondary oocyte and polar body- these then split into one egg and three polar bodies
The polar body lies between what two things?
The zona pellucida and the cell membrane of the secondary oocyte.
If the oocyte is not fertilized how long before it degenerates?
24 hours
What is released from the follicle during ovulation?
Ovum
As the follicle ruptures, LH causes the development of what?
Corpus luteum
If fertilization occurs, what hormone does the egg begin to produce?
Human chorionic gonadotropin (hCG)
The corpus luteum secretes what hormone?
Progesterone
How long does the corpus luteum produce progesterone until placental production starts?
up to 4 months
What are spermatogonia stem cells?
Immature sperm cells
How many days does it take spermatogonia to mature?
74 days
Spermatogenesis is regulated by what hormone?
Luteinizing hormone
Testosterone binds to what kind of cells to promote spermatogenesis?
Sertoli cells
What cells in spermatogenesis are similar to follicular cells in oogenesis?
Sertoli cells
What is the transformation of spermatids into spermatozoa called?
Spermiogenesis
What covers half of the nuclear surface and contains enzymes to assist in the penetration of the egg?
Acrosome
What are the steps of spermiogenesis?
Formation of acrosome
condensation of the nucleus
formation of the neck, middle, and tail
shedding of cytoplasm
all taking approx 64 days
Where does fertilization occur?
Fallopian tubes
What percentage of sperm deposited in the vagina enters the cervix?
1%
Why would the sperm become less mobile?
An egg is not present
What is capacitation?
The period of conditioning of the sperm in the female reproductive tract
It lasts about 7 hrs
Removes glycoprotein that overlays the acrosomal region of the spermatozoa
What reaction does the zona pellucida induce?
Induces acrosome reaction
mediated by ligand ZP3 zona protein
Release of acrosomal enzymes allows sperm to penetrate the zona
After penetration of the zona what does the sperm first come in contact with?
Oocyte surface
After fertilization of the egg, what does the cell undergo?
A series of mitotic divisions increase the number of cells called blastomeres, the mass is hardly larger than a zygote
Approximately 3 days after fertilization the embryo contains 12-15 cells configured as a solid ball of cells and is called what?
Morula
What hormone helps to relax the uterine tube to allow the embryo to complete its journey into the uterus around day 3.5-4
progesterone
What is a blastocyst?
A fluid-filled cavity with a collection of cells at one end created by the embryo
What is the trophoblast?
Thin outer layer of cells that becomes embryonic part of placenta.
What does the inner cell mass give rise to?
embryo and amnion (sack)
After 2 days in the uterus the zona pellucida degenerates and disappears to allow what to happen?
Blastocyte hatches to find a permanent home in uterus
1st step of the implantation process is called what?
Attachment phase
What type of cells have specialized adhesion molecules that bind to the epithelial cells of the endometrium?
Trophoblast cells
Trophoblast differentiate into what two layers?
Inner layer - Cytotrophoblast
Outer layer - Syncytiotrophoblast, which extends into the endometrium and derives nourishment from the maternal tissue
Why is it thought that one-half of all embryos fail to implant successfully?
They are thought to have severe genetic abnormalities incompatible with survival.
