Embryology Flashcards
What is formed when the (pro)Nucleus of sperm enters and fuses with the (pro)nucleus of the ovum?
Diploid cell called zygote is produced
Are mitochondrial diseases inherited from the mother or father?
The mother
What is a morula?
Solid ball of cells formed from the cell division of zygote
What cavity allows nutrition to reach the core of cells?
Blastocystic cavity
What is the outer lining of cells called?
The trophoblast
What does the morula convert into?
Blastocyst
Where does the blastocyst travel to?
Moves through uterine tube, to reach uterine cavity
Does the cell division from the zygote to blastocyst increase or decrease in speed?
Increase
How does the zygote/morula/blastocyst move to reach the uterine cavity?
Ciliated epithelium
What could occur if pregnancy is abnormal?
Ectopic pregnancy
What process occurs at day 7 (or 6) of pregnancy?
Implantation - the blastocyst begins to burrow into the uterine wall (endometrium)
What plays an important role in burrowing the blastocyst?
The chorion
What are the finger-like processes on the chorion?
Chorionic villi
What are the main processes of the chorion?
- Implantation process
- Forms part of the placenta
- Secretes human Chorionic gonadotropin (HCG)
What is human chorionic gonadotropin (HCG) used for?
Used to detect pregnancy
Also helps maintain the endometrium
What is the Decidua basalis?
Part of the endometrium deep to the implanted conceptus.
What do the cells of the inner cell mass form?
A 2-layered flat disc called the Bilaminar Disc.
What 2 cavities begin to form after the formation of the bilaminar disc?
Amniotic cavity and Yolk sac
What is the placenta?
A flattened circular organ in the uterus of pregnant eutherian mammals, nourishing and maintaining the fetus through the umbilical cord.
What are the main functions of the placenta?
- Foetal nutrition
- Transport of waste and gases
- Immune etc
Features of foetal part and surface of placenta
Smooth with foetal blood vessels and end of umbilical cord.
Maternal part of placenta
Decidua basalis of endometrium. Rough and has maternal blood vessels.
Features of fraternal/dizygotic twins
- 2 ova released, 2 sperms = 2 separate zygotes
- Different genetic makeups, 2 placentae
Features of identical/monozygotic twins
- 1 ovum, 1 sperm = 1 zygote which divides into 2
- Same genetic makeup, share one placenta.
What is Gastrulation?
Formation of germ layers
What is Neurulation?
Formation of neural tube
What is the primitive streak?
Formed in the midline of the epiblast by the dipping in of cells (invagination)
What are the 3 germ layers formed during gastrulation?
- Ectoderm
- Mesoderm
- Endoderm
=TRILAMAR DISC
How is the the trilaminar disc formed?
Cells from primitive streak invaginate, displacing hypoblast.
Solid tube of cells formed when cells from primitive streak sink down
Notochord
What does the notochord induce?
Notochord induces ectodermal cells in the midline to form a neural tube.
What does the neural tube do to the mesoderm?
Induces the mesoderm to thicken causing it to separate into three parts.
What 3 parts does the mesoderm separate to?
- Paraxial mesoderm
- Intermediate plate mesoderm
- Lateral plate mesoderm
Lateral plate mesoderm splits to form a somatic and splanchnic mesoderm.
What do paraxial mesoderms form?
Somites
What occurs 4th-8th weeks - embryonic/organogenetic period
- Folding into a tube (lateral folds) which started in 3rd week completes
- Heart starts to beat on day 24
- 43 pairs of somites form in the paraxial mesoderm and differentiate further.
Etc
What does each somite (paraxial mesoderm) divide into?
- Dermatome
- Myotome
- Sclerotome
What are the dermatome, myotome and sclerotome responsible for?
Dermatome = dermis of skin Myotome = muscles Sclerotome = bones including vertebrae
What is Teratology?
Study of when things go wrong during development.
What are teratogens?
Environmental factors that cause abnormal development.
During which weeks is there greatest sensitivity to teratogens?
Weeks 3-8
