L4 Fetal Nourishment and Development Flashcards
(55 cards)
How long is the embryonic period?
Week 1 to 8
How long is the fetal period?
Week 9 to 38
What are the 3 stages of cell development?
Hyperplasia: increased cell division
Hyperplasia and Hypertrophy: cell division and cell growth
Hypertrophy: increased cell size
Explain the steps in fertilization (x4).
A sperm perforates the outer layer of the oocyte and breaches the plasma membrane of the oocyte. Enzymes in the acrosome on the sperm break down the zona pellucida.
Sperm enters the cytoplasm of the oocyte without its plasma membrane.
Zona pellucida now closes off and doesn’t allow any more sperm to enter.
What does fertilization trigger?
Sperm entering and first meiosis.
Explain the 4 stages that occur in week one of fetal development?
Where in the reproductive system do they occur?
Stage 1: fertilization > zygote
Stage 2: Zygote divides > 2cell > 4 cell > 8 cell > morula (16-32 cells). Both stages occur within the fallopian tube. Zona pellucida intact
Stage 3: Early blastocysts > late blastocyst
Stage 4: Implantation begins at about the 6th day
What is the main nutrient for the fertilized egg in week 1 and what is it supplied from?
Glycogen supplied by the uterine gland.
In stage 3 of week one of fertilization, what occurs?
A blastocyst cavity develops surrounded in the embryoblast, and then trophoblasts (outer layer).
The blastocyst then enters the uterus and the zona pellucida degenerates.
What occurs week 2 of fetal development?
Implantation - blastocyst is fully embedded in the endometrium and an inner cell mass forms the embryonic plate.
What occurs early in week 2 of fetal development?
Trophoblasts invade the endometrium and secrete proteolytic enzymes (break down proteins).
What is the syncytiotrophoblast?
Placental villi that originate from the trophoblast layer that invade the endometrium to establish circulation of nutrients between the mother and the fetus.
What happens late in week 2 of fertilization?
Inner cell mass becomes a flattened disk of 2 layers and the amniotic cavity develops.
The 2 layers are the epiblast layer and the hypoblast layer.
What is the epiblast layer (top)?
Forms late in week 2 of fertilization and give rise to the ectoderm and the mesoderm.
It is adjacent to the amniotic cavity.
What is the hypoblast?
Forms late in week 2 of fertilization and give rise to the endoderm. As this layer thickens it will develop into the cranial region.
What are the lacunar networks and when do they form?
They are spaces within the trophoblast that fill with maternal blood. It is how the trophoblast absorbs nutrients and oxygen to the embryonic disk. It marks the beginning of maternal-fetal circulation.
Occurs in week 2 of fertilization.
What are 3 main events that occur in week 3 of pregnancy?
Gastrulation
Neurulation
Cardiovascular system begins to develop.
What is gastrulation?
The formation of the 3 germ layers:
- Embryonic ectoderm
- Embryonic mesoderm
- Embryonic endoderm
Which germ layer gives rise to the epidermis, nails, teeth, teeth enamel, inner ear, retina, CNS, and PNS?
Embryonic ectoderm
Which germ layer gives rise to the epithelial lining of the respiratory, and GIT including the glands, and liver pancreas, and bladder?
Embryonic endoderm
Which germ layer gives rise to the muscle, connective tissue, skeleton, cardiovascular system including vessels, blood cells, and bone marrow, as well as the reproductive and excretory systems?
Embryonic mesoderm
The folding of the neural tube stems from what tissue and occurs during what week of pregnancy?
Ectoderm
Week 3
These structures come from the mesoderm and develop into the skeleton and musculature.
What week do they develop?
Somites
Week 3
What is the likely result if the neural plate forms improperly?
Misscarige
What is a coelum and when do they develop?
Spaces within the mesoderm that become body cavities. Develop in the 3rd week.
