Embryology/ Limb Development Flashcards
Embyonic Disk
Give rise to germ layers that form all the tissues and organs of the embryo
What gives the begining of morphogenesis
Gastrulation
Establishment of the body of the Cylindrical Embryo
Is a result of the folding of the flat trilaminar embryonic disk
What surrounds the secondary oocyte
Zona Pellucida and Corona Radiata
Cleavage
2 cell to 4 cell to 8 cells all happen in the uterine tube.
16-32 cells is classified as the morula
The morula enters the uterus considered a blastocyst
Blastocyst has inner cell mass called EMBRYOBLASTt and outer cell mass called TROPHOBLAST
When does implantation begin? Where does it occur?
It begins on the first week and ends on the second week. It implants on the posterior wall of the superior part as the zona pellucida dissapears
What does the trophoblast become?
- Cytotrohpoblast
- Syncytiotrohoblst
Note: #2 forms a blood filled lacunae that erodes the mothers endometrial blood vessels and establishes a uteroplacental circulation
What are two types of abnormal pregnancies
- Ectopic Pregnancy
- Placenta previa (implantation in the inferior segment of the uterus near the internal os) In this case patients would present with vaginal bleeding.
Second Week of Development (Bilaminar Germ Disc)
Period of 2’s
1. Inner Cell Mass- becomes epiblast and hypoblast
- Outer Cell Mass- becomes Cytotrophoblast and Synctiotrophoblast
- Cavities form (2)- Amniotic Cavity and the Yolk sac cavity
- Extraembryonic (Lateral) Mesoderm splits- Somatic Layer and Splanchnic Layer
Third Week of development (Trilaminar Germ Disc)
Period of Threes
1. Primitive Streak (Gastrulation gives us the Three Germ Layers)
- Primitive Node ( Neuralation gives us the Neural Plate, Neural Groove, and Neural Tube)
- Mesoderm on each side of the notochord (Paraxial gives us the intermediate mesoderm, the lateral plate mesoderm, and the neural crest cells
What structure gives rise to all three germ layers
Epiblast. It is called gastrulation
What structure gives the neural tube?
Ectoderm. It is called neuralation
What structure produces HCG
The Placenta
What two parts make up the placenta
The Villous Chorion (baby) Decidua Basalis (Mom)
Note: There are three different types of Decidua
Which structure will regress by the fourth month of pregnancy?
Cytotrophoblast. As a result the exchange from mother to baby an baby to mother takes place across the synctiotrophoblst and fetal endothelium.
Umbilical Cord
Umbilical vessels = 2 arteries plus LEFT umbilical vein
Ducts = 2 Ducts Allantois plus virelline duct (both of which will be atrophied
When considering twins which structure must each baby have of it’s own regardless of whether they are monozygotic or dyzygotic twins?
A. Placenta
B. Chorion
C. Amnion
D. Yolk Sac
Amnion
How many degrees is limb rotation
90 degrees
Amelia
absence of an entire limb
Meromelia
Absence of part of a limb
Phocomelia
Short, poorly formed limb
Polydactyly
Extra digit
Syndactyly
Fusion of digits
Lobster Claw Deformity
Middle digit is absent
How do limb buds elongate
By proliferation of the mesenchyme
Relationship between growth and rotation of limbs and cutaneous nerve supply.
Know that there is a relationship
When does the initial growth of limbs occur
4-8 weeks
Which limb buds develop first upper or lower
Upper by approximately 2 days
AER (Apical Ectodermal Ridge)
has an inductive influence on the limb mesenchyme which promotes growth and development of the limbs
(PROXIMODISTSAL AIXS)
How do limb buds elongate
By proliferation of the mesenchyme within them.
The limb grows in how many different axes
proximal- distal
dorsal-ventral
posterior-anterior
What genes and what signaling mechanisms are essential for the limb outgrowth carried out by AER?
FGF Signaling HOX genes (retinoic acid and/or ethanol can effect the HOX genes)
