Embryology Flashcards
What happens during the first week of development?
Fertilization, cleavage, and implantation
What happens during the second week of development?
Period of 2: the embryoblast divides into the epiblast and the hypoblast; the trophoblast divides into the cytotrophoblast and the syncytiotrophoblast; two cavities are present, the amniotic cavity and the yolk sac
What happens during the third week of development?
Period of 3: mesoderm differentiation; gastrulation (ectoderm, endoderm, and mesoderm); neurulation happens (neural plate, groove, and tube)
What is gametogenesis?
It is a process by which the chromosome number is reduced by half, and the shape of the cell is altered, creating sperm and oocytes
Where does fertilization happen?
In the ampulla of the uterine tube
What are the phases of fertilization?
- Capacitation and acrosomal reaction. 2. Penetration (of 3 layers). 3. Zona reaction
What are the results of fertilization?
- After the sperm penetrates the secondary oocyte, the ooctye completes meiosis 2, forming the ovum and the second polar body. 2. The sperm and ovum nuclei swell, forming pronuclei. 3. pronuclei approach each other and mitotic spindle forms between them. 4. Chromosomes of the pronuclei intermix, fertilization is accomplished. Then, the DNA replicates in preparation for the first cleavage division.
What is the end product of fertilization?
The restoration of the normal diploid number of chromosomes and the determination of the chromosomal sex of the embryo
Describe the process of cleavage?
- Zygote
- 4-cell stage
- Morula
- Early blastocyst
- Implanting blastocyst
Where is the site of implantation?
The posterior superior wall of the uterus
What is an ectopic pregnancy?
It is a tubal pregnancy where the blastocyst implants within the ampulla. It is presented with uterine bleeding, sudden onset of abdominal pain (appendicitis), missed menstrual period, and and +HCG test
What are the parts of the placenta?
Maternal: decidua basalis
Fetal: chorionic villi
What is the function of the placenta?
It assists with gas exchange (oxygen, carbon dioxide), nutrient exchange (glucose, fatty acids, amino acids, and electrolytes), as well as hormonal and immunologic exchange.
What is the result of endoderm folding?
The endoderm becomes enclosed inside the embryo forming the gut-tube
What is the result of ectoderm folding?
The ectoderm covers the embryo from outside and amniotic sac expand to surround the embryo
What is the process of limb development?
Limb buds develop from the ventrolateral body wall. The digital rays form notches which form webbed fingers which form separate digits.
Which direction do the upper limbs rotate?
They rotate 90 degrees laterally
Which direction do the lower limbs rotate?
They rotate 90 degrees medially
What is amelia?
The absence of an entire limb
What is meromelia?
The absence of part of a limb
What is polydactyly?
Extra digit(s)
What is syndactyly?
The fusion of digits``
What separates maternal blood and fetal blood during the later stages of pregnancy?
The syncytiotrophoblast and fetal endothelium
What must degenerate for blastocyst implantation to occur?
The zona pellucida
What is the placenta previa?
It occurs when an implanted embryo is near the internal os of the pregnancy
What are the two components of the placenta?
Chorionic villi and decidua basalis
What is the purpose of chorionic villi?
They serve as finger like projections that insert themselves into the uterus
What are somites?
They surround the notochord and differentiate to form the vertebral column, along with the vertebral muscle skin. They will give sclerotome, myotome, and dermatome
