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
What is the maternal placenta and what are its structures and functions?
Endometrium
Provides blood vessels of maternal placenta, maternal blood fills into inter0villus space delivering nurtients and taking wastes
What are the chorionic villi? What is their function?
Extensions from chorion containing fetal capillaries that project into intervillous spaces of the maternal placenta
Function: Absorb nutrients and deposit wastes into maternal blood
No blood cell movements between blood cells of baby and mother
What occurs and does not occur at placenta?
Maternal blood cells do not pass into chorionic villi
Fetal cells can enter the mothers blood stream
microchimerism: baby cells present in all mother body tissue (not many but they are there
Transport:
Waste: CO2, nitrogenous/metabolic wastes
Nutrients: O2, carbs, proteins, triglycerides
Pathogens: some pass through although most are prevented
-toxins & drugs (nicotine, alcohol, THC mercury etc.) most drugs can get through
What is present at the 4 week mark and how long is the baby at the 7-week and 8-week mark?
4: 0.6 cm, pharyngeal arches (gill-like structures), tail, arm bud, heart bulge, somites (future muscles), future lense
7: 1.0 cm
8: 2 cm
What is the external genitalia development?
Structures not differentiated until 9-12 wks
Structures come from same embryonic organs (homologous)
Penis to clitoris and lamia minor
Scrotum to labia majora
At what point is the baby considered a fetus? What occurs at this point?
At 9 wks
Blood vessels in and around heart are arranged differently because umbilical cords bring O2
-O2-rich from vein dumps into right atrium via inferior vena cava, superior vena cava brings O2-poor blood from rest of body
-Foramen ovale: allows O2 rich blood to move from R to L atria
-Ductus arteriosus connects aorta with pulmonary trunk allowing both ventricles to get blood into the aorta (to head, body, and placenta)
What months correlate with the trimesters?
First trimester: 1-3 months
Second trimester: 4-6 months
Third trimester: 7-9 months
