Fetal Nourishment and Development Flashcards
What are the major developmental periods?
- fertilization - day 1
- embryonic period - week 1 to 8
- fetal period - week 9-38
What are the critican periods of fetal development?
- hyperplasia
- hyperplasia and hypertrophy
- hypertrophy
Where does fertilization occur?
fallopian tubes
Process of fertilization
Sperm encounters the egg in the fallopian tube where the acrosome at the head contains enzymes allowing it to capacite the outer wall of the oocyte, break down the zona pellucida and sperm enters the cytoplasm of the oocyte leaving behind its plasma membrane.
What is the first division with fertilization?
first mitotic division occurs and the oocyte is now called a zygote containing half chromosomes from each parent
What are the stages of week 1?
Both occur within the fallopian tube
* stage 1: fertilization → zygote
* stage 2: zygote division
* stage 3: early blastocyst → late blastocyst
* stage 4: implantation begins
What provides nutrition during zygote division?
Zona pellucida stays intact, providing nutrition and protective glycoproteins as the cell divides
What is the blastocyst structure?
- blastocystic cavity
- embryoblast (inner cell mass)
- trophoblasts (outer layer)
What happens with the blastocyst?
The morula becomes blastocyst which enters the uterus and the zona pellucida degenerates since major nutrients will start coming from the thick endometrium layer with implantation
What provides nutrients in week 1?
Uterine secretions (mostly glycogen), trophoblasts and yolk sac helps transfer nutrients to fetus until circulation established
What is the major development of embryonic development week 2?
Implantation where blastocyst wil completely imbed in endometrium and inner cell mass forms the embryonic disc to establish nutrient circulation.
* Early week 2
* Later week 2
What occurs in early week 2?
syncytio-trophoblasts (outer layer of blastocyst) invades the endometrium via proteolytic enzymes
What occurs in later week 2?
Inner cell mass becomes a flattened disc of 2 layers and amniotic cavity develops
* epiblast layer is adjacent to amniotic cavity giving rise to ectoderm and mesoderm
* hypoblast layer is adjacent to blastocyst cavity and will. give rise to endoderm
What occurs with localized thickening of the hypoblast?
develop into the cranial region
How is nutrient circulation established in week 2?
development of lacunae in the trophoblasts form into lacunar networks
* fill with maternal blood from uterine capillaries so that absorption of nutrients, oxygen can go to embryonic disc
What are the main processes for embryonic development in week 3
- gastrulation
- neurulation
- cardiovascular system begins
What happens in early week 3?
gastrulation which is the formation of the 3 germ layers:
* embryonic ectoderm (outer)
* intra-embryonic mesoderm (middle)
* embryonic endoderm (inner)
What do the three layers lead to?
complex series of folding results in the human body
What does embryonic ectoderm lead to?
- epidermis, hair, nails, teeth enamel, retinal
- CNS, PNS
What does the embryonic endoderm lead to?
- epithelium lining of respiration and GI including glands
- epithelium of liver, pancreas, bladder
What does the embryonic mesoderm lead to?
- muscle, connective tissue, skeleton
- cardiovascular system including vessels, blood cells, bone marrow
- reproductive and exretatory systems