Development And Inheritance Flashcards
What is Fertilization?
When the sperm and oocyte combine and their nuclei fuse
What is the cell made in fertilization called?
A zygote
What does a zygote consist of?
Half the genetic information from the mother and half from the father
How many sperm cells are needed for fertilization?
Hundreds of millions
What prevents sperm cells from reaching fertilization?
Acidity of vagina canal and thick cervical mucus (millions), phagocytic leukocytes (thousands)
How many sperm survive?
Thousands
How fast do the surviving sperm travel through the tubes?
30 - 120 minutes
How long can sperm survive in the tube?
3 - 5 days
When can intercourse lead to fertilization?
a few days before ovulation
How long does an oocyte last after ovulation?
24 hours
What is capacitation?
The membrane over the sperm head thins and allows the sperm to prepare for fertilization
What are the two layers of the oocyte?
Corona Radiata and Zona Pellucida
What layer of the oocyte does the sperm penetrate through?
Corona Radiata
What must the sperm bind to in the oocyte?
A receptor in the Zona Pellucida
What is the Acrosomal Reaction?
The enzyme filled cap of the sperm releases enzymes to penetrate the 2 layers of the oocyte
What does the sperm fuse to in the oocyte?
The plasma membrane of the oocyte
How many sperm cells does it take for the acrosomal reaction?
Hundreds of sperm to release enzymes
What happens to the sperm and oocyte after fertilization?
The oocyte plasma membrane depolarizes to prevent further penetration; protiens between layers shock excess sperm to be killed and released; oocyte receptors are destroyed
What forms after fertilization?
An impenetrable protein barrier forms called the fertilization membrane
What happens to the female zygote (oocyte) upon fertilization?
Meiosis is completed and the last polar body is ejected
Once the oocyte has complete meiosis it is called a ____ until the ___ intermingle.
Ovum, DNA
How are fraternal twins created?
1% of the time, 2 oocytes are released and fertilized at the same time
How are identical twins created?
When the female zygote (oocyte) splits
What is gestation?
The time it takes for full fetal development
How long is the pre-embryonic stage?
The first 2 weeks
When does the zygote become an embryo?
From weeks 3 - 8
When does an embryo become a fetus?
From weeks 9 - birth
What happens during the embryo stage?
The organs begin to form
What is conceptus?
The zygote and associated membranes moving to the uterus
How long does conceptus take?
About 3 days
What happens in conceptus?
The zygote divides from 2 cells to 16 cells
What do the zygote cells eventually form into in the uterus?
An inner mass (embryo) and outer shell (placenta)
What are the inner cells for a few more days after reaching the uterus?
Totipotent cell
What is totipotent cell?
An ultimate stem cell capable of becoming anything (muscle, nerves, connective or epithelial tissue, organs, etc.)
What happens to the zona pullucida during embryonic development?
It is broken down for implantation in the uterus
When and where should implantation be done?
By the end of the first week and within the uterine wall.
__% - __% of blastocytes fail implantation and shed with ______
50% - 70%, menses
How does the grouping of cells implant into the uterine wall?
By digesting endometrial (stratum functionalis) cells of uterus
What happens after the grouping of cells implants into the uterine wall?
The uterus will rebuild the uterine mucosa wall and the blastocyte will be enclosed within the wall.
Why is Human Chorionic Gonadotropin (hCG) released?
It is released during implantation to keep the corpus luteum healthy, growing and secreting progesterone so menses does not begin.
When is implantation done?
By the middle of the second week
When can you see a positive pregnancy test and why?
By the middle of the second week because hCG is in the blood stream for a positive pregnancy test/
What is an ectopic pregnancy?
Implantation outside of the uterus
What is placenta previa?
When implantation happens in the inferior section of the uterus and the placenta covers the opening of the cervix
Where should implantation happen in the uterus?
In the posterior superior section of the uterus
What happens if the placenta is blocking the cervical canal?
The baby will not be able to come out during birth
What is the amnion?
A sac that surrounds the embryo and is filled with fluid of protection
What is the yolk sac?
A sac that provides nourishment until the placenta is functional; it is a source for blood cells and germ cells
What is the embryo/fetus floating in?
Amniotic Fluid
What is the allantois?
A primitive excretory duct that will become a part of the urinary bladder
What forms the outer layer of the umbilical cord?
The yolk sac and the allantois
What is the chorion?
The membrane that surrounds the amnion, yolk sac, and allantois
What is the umbilical cord?
The connections between the placenta and the fetus
When does embryogenisis happen?
During week 3
What happens in embryogenisis?
The 2 layer disc becomes 3 layers and cells go from totipotency to multipotency
What is the primitive streak?
indentation for new cells to travel along to form endoderm or mesoderm
How does the ectoderm form?
From the cells that do not migrate
The endoderm, mesoderm, and ectoderm are the _______, ______, or _______ layer of the different organ systems.
inner, middle, outer
When does the placenta start to develop?
During weeks 4 - 12 (starts in the embryonic phase and stops at the fetus phase)
What does the placenta do?
Feeds the embryo
What is the placenta composed of?
Maternal and embryonic tissue
True of False: The placenta connects to the conceptus through the umbilical cord?
True.
When is the placenta completed?
At week 14 - 16
True or False: Some substances cross the placenta due to peristalsis.
False.
Some substances cross the placenta due to SIMPLE DIFFUSION.
Which substances use simple diffusion to cross the placenta and which substances to active transport?
Simple Diffusion: Oxygen and Carbon Dioxide
Active Transport: Amino acids and Iron (they are in high demand)