Remaining Materials Flashcards
What is the cell from the female capable of being fertilized and what surrounds it? What are the purpose of the surrounding structures? How long is it viable?
Secondary oocyte. Corona radiata & zona pellucida for protection. It is viable for 24 hours.
What must the sperm do to fertilize?
Must get to genetic material at the center of the secondary oocyte
-acrosome (tip of head) release lysosome enzyme that dissolves layers
-only 1 sperm bind to receptor on surface on oocyte
-Release nucleus into oocyte = zygote
How many sperm are released and how many are needed for fertilization.Why?
30-750 million sperm per ejaculation
-100s of sperm must get to the oocyte at the same time to layers of corona radiata and zona pellucida.
- get to s p and release everything
-only one makes contact with oocyte plasma membrane
What happens to the secondary oocyte when the sperm makes contact?
The oocyte receives the DNA and deactivates other sperm receptors. Oocyte completes meiosis II and becomes an ovum. Nuclei of ovum and sperm combine to form zygote with 46 chromosomes.
What is a zygote, what does it do, and what does it become?
It is a single cell that contains 23 chromosomes from the egg and 23 from the sperm.
It begins mitosis
It becomes the 2-cell stage then the 4-cell stage at 2 days in the ithmus
What comes after the 4-cell stage?
Morula: solid ball of cells (3 days) 16 cells “mulberry”
What comes after the morula?
Blastocyst 70-100 cells, morula hollows out and fills with fluid, (4 days) enter uterus and floats for 2-3 days and is nourished by uterine secretions then implants in endometrium of uterus (6-7 days post-ovulation)
implanting blastocyst is called the embryoblast (7 days) consists of sphere of trophoblast cells
What occurs for the blastocyte to implant?
Inflammatory-like response of endometrium
-protrusions from blastocyte invade and digest endometrium
-blastocyte burrows into lining of endometrium as it is eroded
-endocrine cells cover and seal off blastocyte
What stage occurs after implantation? What occurs at this stage?
Gastrulation at ~ 3 weeks an important change occurs
-embryo folds in on itsef
-embryonic disk transforms into 3-layered embryo with three primary germ layers (ecto/meso/endoderms)
-beginning with primitive streak: raised groove establishing the longitudinal axis of the embryo
Where is the ectoderm found in the embryonic disk and what does it give rise to?
Most superior (top layer), forms nervous system and skin (including skin accessory organs)
Where is the endoderm found in the embryonic disk and what does it give rise to?
Bottom layer: forms epithelial lining of digestive, respiratory, and urogenital system along with associated glands/organs
Where is the mesoderm found in the embryonic disk and what does it give rise to?
Middle layer: forms connective and muscular tissue of circulatory, skeletomuscular, and respiratory systems.
What are extra-embryonic membranes and what are the four?
Outside embryo supporting structures Amnion, yok sac, allantois, Chorion
What is the amnion? What is its structures and what does it do.
It lines the amnionic cavity and secretes amniotic fluid into it. It also filters embryotic waste out of fluid.
Fluid protects embryo/fetus from outside injury by absorbing stress
What is the yolk sac? What is its structures, what does it do, and what happens to it during development?
Inner structure, inside & outside embryo
Produces blood cells, germ (spermato/oogonia) cells, and part of digestive tube
Gets smaller and more outside as development continues.
What is the function of the allantois what are its structures and what do they do?
Forms blood vessels of umbilical cord
arteries- away from baby, O2 poor
veins- towards baby, O2 rich
What is the chorion and what does it do?
Fetal portion of placenta
Secreted hCG (human chorionic gonadotropin) that maintains the corpus luteum to prevent menstruation for 2-3 months after which the placenta takes over role of producing progesterone and estrogen
