Introduction to Embryology Flashcards
What is the embryonic period?
Fertilization to 8 weeks (56 days)
What is the fetal period?
9th week (57 days) to term (38th week)
What generally happens during the embryonic period?
Initial development of all major structures and establishment of all organ systems.
What generally happens during the fetal period?
Differentiation and growth of organs and tissues.
During interphase the cell has how many sets of chromosomes?
2N
Preprophase the cell has how many sets of chromosomes?
4N
During mitotic prophase, metaphase, anaphase, and telophase the cell has how many sets of chromosomes?
4N
During mitosis cytokinesis the cell has how many sets of chromosomes?
2N
During meiosis 1 preprophase the cell has how many sets of chromosomes?
4N
During meiosis 1 prophase 1, metaphase 1, anaphase 1, and telophase 1 the cell has how many sets of chromosomes?
4N
During meiosis 1 cytokinesis 1 the cell has how many sets of chromosomes?
2N
During meiosis 2 prophase 2 through telophase 2 the cell has how many sets of chromosomes?
2N
During meiosis 2 cytokinesis 2 the cell has how many sets of chromosomes?
1N
How many sets of chromosomes does an unfertilized oocyte have?
1N
How many sets of chromosomes does a spermatid have?
1N
Primordial sex cells (germ cells) originate as what?
Specific cells lining the yolk sac (umbilical vesicle)
How many sets of chromosomes do primordial sex (germ cells) cells have?
Diploid 2N
Where do the primordial sex cells (germ cells) initially migrate?
They migrate to occupy gonads and mature into gametes (mature sex cells: spermatozoa & oocyte)
The genital ridge is also called what?
the gonadal ridge
What happens during gametogenesis?
This is a process that reduces chromosomal number by 1/2. Diploid to haploid. 2N to N.
What is spermatogenesis?
Spermatogonia to sperm (begins at puberty)
What is oogenesis?
Oogonia to oocyte (begins BEFORE birth, halts, continues at puberty)
How many oocytes does a female have at three months in the womb?
About 2 million
How many oocytes does a female have at five months in the womb?
About 7 million
How many oocytes does a female have at birth?
About 600 to 800 thousand
How many oocytes does a female have at menarche?
About 400 thousand
Are mature sperm 23X or 23Y?
They can be one or the other.
Are mature oocytes 23X or 23Y?
They are all 23X.
What is the outer most layer of the oocyte called?
Corona radiata
What is the layer of an oocyte just deeper than the corona radiata?
The zona pellucida
What is the superior most part of the uterus called?
Fundus
Where is the cervix located in the uterus?
This is the initial opening to the uterus from the vaginal canal.
What are the four major parts of the fallopian tube?
The isthmus, the ampulla, the infundibulum, and the fimbriae.
What two hormones are involved in ovulation?
FSH and LH
Where do FSH and LH come from?
The anterior pituitary gland
Where is the normal site of fertilization in a female?
The ampulla of the fallopian tube
How many oocytes does FSH stimulate in one cycle?
10-15 oocytes
When LH surges how many oocytes are actually ovulated?
One
The oocyte is halted in what phase at birth?
Prophase 1
At puberty a females oocyte matures but is halted again at what phase?
Metaphase 2
What is capacitation and when does it occur?
Surface proteins are removed from acrosome; this allows acrosome to react with corona radiata and ZP, and release of enzymes. This occurs about seven hours after ejaculation.
What is the acrosome reaction?
This occurs on contact with ZP; results in release of enzymes, allows penetration of ZP and facilitates fertilization.
What are the three phases of fertilization?
1.coronal cells, 2.acrosomal reaction, 3.plasma membranes fuse, meiosis 2 resumes, metabolism of oocyte increases
What is formed when haploid pronuclei fuse?
A diploid zygote is formed.
Is the sex of zygote determined at fertilization?
Yes
What is initiated as a result of fertilization?
Cleavage
Give a summary of fertilization in three phases.
Phase one: penetration of corona radiata
Phase two: penetration of the zona pellucida
Phase three: fusion of the sperm and oocyte cell membranes
Hw many hours after fertilization does zygote cleavage start?
about 30 hours
Cleavage is also the same as what?
Mitosis
What are the early embryonic cells called?
Blastomeres
What is compaction?
Cell divisions result in successively smaller blastomeres that remain confined within the space available within the zona pellucida.
Compaction begins at what stage?
At the 8 cell stage
After the 8 cell stage what is the zygote called?
A morula and looks like a mulberry or blackberry.
How many cells does a morula have?
12-32
At what time in days does a morula exist?
3-4 days
How is a morula organized?
An inner cell mass and an outer cell mass
What is the structure of a blastocyst?
The inner embryoblast, the outer trophoblast and the cavity is filled with fluid.
At how many days does attachment happen?
6 days
At how many days does differentiation happen?
7 days
Where does the trophoblast cells typically attach?
To endometrium (posterior or anterior wall of body of uterus)
Upon attachment at day seven the trophoblast differentiates into what to things?
Cytotrophoblast, and syncytiotrophoblast
What is an ectopic pregnancy?
The blastocyst implants outside the normal uterine locations.
What is the hypoblast?
This is a layer of small cuboidal cells formed from the embryoblast and separate the embryoblast from the blastocystic cavity.
