reproductive embryology Flashcards
How long can sperm survive
5 days
describe the journey of an egg
1 - egg leaves ovary and enters fallopian tube
2 - sperm enters egg and nucleus fuses together
3 - fertilised egg divides
4 - cells attach to the uterus
What are the steps of implantation
Hatching
Apposition
Adhesion
Invasion
Describe hatching
The trophoectoderm cells produce protease which dissolves the zona in preparation for implantation
Describe apposition
First connection between blastocyst and endometrium, apposes to microvilli like structure called pinopodes expressed on receptive endometrium
Describe adhesion
The blastocyst attaches itself to the endothelial layer of the maternal endometrium - hCG begins to be secreted
Describe invasion
The trophoblast proliferates, differentiates and crosses the epithelial basement membrane and invades the endometrial stroma to form the placenta - the uterine spiral arteries are remodelled by the invasive trophoblast
What is the changes done to the endometrium prior to implantation - decidualisation
Stromal cell differentiation - elongated fibroblast like cells converted into decidual rounded epithelial cells
Angiogenesis
Increased inflammatory response e.g macrophages, lymphocytes and decidual leukocytes for maternal immune tolerance
Describe gastrulation
-Groove appears in caudal end of the epiblast called the primitive streak
- The epiblast cells migrate into the hypoblast which displaces them, forming the endoderm
- The epiblast cells continue through the primitive streak which forms the mesoderm
- the remaining epiblast forms the endoderm
What does the ectoderm become
Epidermis, CNS, PNS, hair, nails, neuroendocrine organs like the pituitary gland and enamel of teeth
What does the mesoderm become
Dermis, MSK, CVS, kidneys, ureters, trigone of bladder, gonads, adrenal cortex, visceral and parietal linings e.g peritoneum
What does the endoderm become
Lining of GI tract, liver parenchyma, pancreas, thyroid gland, parathyroid gland, tonsils, thymus, bladder (not trigone) and the urethra
Describe dizygotic multiple pregnancy
Two or more eggs fertilising and implanting - non identical
Describe monozygotic multiple pregnancy
One embryo splitting - identical twins
What does the kidney and ureter form from
nephrogenic cord
What does the ureteric duct form
Ureter
What does the metanephric mesenchyme form
kidney
What does the gonad form from
The gonadal ridge
Where does the kidney develop
The pelvis and then ascends into the abdomen with the final position in the 12th week
What does the urogenital sinus form
Bladder and the urethra
What protein acts on the indifferent gonad to promote formation of testes
SRY protein - contained in the Y chromosome
What does the fused portion of the paramesonephric duct form
the uterus and the upper 2/3rd of the vagina
What does the unfused portions of the paramesonephric duct form
The fallopian tube
What forms the lower 1/3rd of the vagina
urogenital sinus
