Embryology - Fertilization (3) Flashcards
(28 cards)
What are the female sex cells called
Gametes - secondary oocyte cells (immature cells only undergone the first stage of meiosis
Gonads = ovaries
Explain the menstrual cycle
- Each menstrual cycle is about 14 days once menstruation begins
- one ovary matures a female gamete cell and prepares to release it
- gamete cell are released during ovulation
- the oocyte leaves the ovary and travels to the fallopian tube and enters the ampulla region where fertilization occurs.
Label the diagram
Now long are sperm and oocytes viable for respectively?
Sperm lives up to 6 days (typ)ically 24hr]
Oocyte viable for 24hrs
Window - 6 days before ovulation and 1 day afterwards
Now does the sperm travel through the vagina?
- Sperm is self-propelled via flagella (tail) - once in the region of the uterus, muscular contraction in the uterus help pus h sperm - contraction can be due to hormone release of Roxy toein and prostaglandins that support sperm and stimulate contraction
What are the 3 periods of prenatal development (conception - birth)
- Germinal period = first 2 weeks of development; formation of primitive germ layers
- Embryonic period = week 3 to end of week 8; organ systems develop
- Fetal period = 9th week until birth; organ systems grow and mature
What is the difference between clinical age and embryonic age
14 days less than clinical age
Explain the initial steps of fertilization
The sperm that makes it to the uterine tube (100 - 200) have to move through the corona radiadica to reach the zone pellucida. To break through this protective layer and reach the plasma membrane of the oocute, the sperm binds to the ZP3 glycoprotein which causes a acrosomal reaction - the sperm then binds to integrin alpha-6 beta l on the plasma membrane to cause fast depolarization (fast block to polyspermy ) such that only I sperm can make it inside the oocyte.
What stops multiple sperm from f fertilizing the oocyte
1.) fast block polyspermy= depolarization via binding to integrin ab61
2.) slow block to polyspermy = intracellular release of calcium causing exyctosis of water where the oocyte shrinks, zone pellucida denatures and ZP3 protein inactivates
The _______ region of the uterine tube is typically where fertilization occurs
The AMPULLA region of the uterine tube is typically where fertilization occurs
Put the following steps of fertilization in order
- acrosomal reaction
- oocyte undergoes second meiosis division
- sperm binds to integrin a6B1 receptor
- formation of zygote
- male and female pro nucleus form
- depolarization of the oocyte plasma membrane
- sperm pushes through corona radiata
- sperm binds to ZP3 receptor
- sperm pushes through corona radiata
- sperm binds to ZP3 receptor
- acrosomal reaction
- sperm binds to integrin a6B1 receptor
- depolarization of the oocyte plasma membrane
- oocyte undergoes second meiosis division
- male and female pro nucleus form
- formation of zygote
A group of 12 or more cells that developed following fertilization is called?
Morula
Implantation in the endometrium of the uterus occurs about ___ days after fertilization?
7
In the blastocyst the cells that develop into the embryo are the _______?
Inner cell mass
The fluid space above the epiblast layer of cells is called the _____ _____
The fluid space above the epiblast layer of cells is called the AMNIOTIC CAVITY
Some of the cells migrate through the primitive streak which forms the 3 germ layers. Which layer is formed from the cells that do not migrate?
Ectoderm
The pericardial, pleural, and peritoneal cavities develop from the _____
Coelom
Around day 20, a structure called the ____ forms and will eventually become part of the bladder
Allantois
The thickened ectoderm layer that stimulates the outward growth of the limbs is call?
Apical ectodermal ridge
The foremen ovale closes due to
A) increased pressure in the right atria
B) decreased pressure in left atria
C) cutting of umbilical cord
D) increased pressure in the left atria
D - increased pressure in the left atria
The inner cell mass cells form 2 chambers. What is the top layer, what is the bottom layer?
Top layer = epiblast and will become the embryo - 3 germ layers
Bottom layer = hypoblast cells help form extra embryonic tissues and embryonic disc
When does gastrulation occur, and what is it?
Day 13/14
- epiblast layer elongates and proliferates - forms primitive streak near the caudal end
- epiblast cells migrate through primitive streak towards hypoblast layer where some displace this layer
- endoderm cells = most inner layer and displace the hypoblast layer
- mesoderm cells = middle layer that does not displace the hypoblast layer
- ectoderm cells = outer layer that do not migrate through primitive streak
= germ layers that differentiate to develop the embryo and fetus
When is the notochord formed and how?
Day 16
- from mesodermal cells and forms cylinder shape under the ectoderm
- notochord is involved in induction which sends chemical signal to ectoderm to form the neural plate which surrounds the notochord (day 18)
Describe the formation of the neural tube
Day 18-26
- ectoderm forms neural plate around notochord
- lateral edges of the neural plate rise and form NEURAL FOLDS
- these neural folds come higher and form indentation where the ridged form the CRESTS OF THE NEURAL PLATE
- neural crests come together and merge to form NEURAL TUBE
- neural tube becomes spinal cord and brain, the crest cells break off and migrate to build parts of the PNS
