Basic Body Plan/Embryology Flashcards
What does the ectoderm form?
Central and peripheral nervous systems
Epidermis, hair, nails
Sensory epithelium of the nose, ear, and eye
What does the mesoderm form?
Skeletal, smooth and cardiac muscle
Cartilage, bone, connective tissue, blood
Kidneys and gonad
What does the endoderm form?
The epithelium of gut and its derivatives (liver, gallbladder, pancreas)
Epithelium of the respiratory
What is agenisis?
Missing organ caused by missing embryonic tissue (renal agenesis)
What is aplasia?
Missing organ due to growth failure of embryonic tissue (thymic aplasia)
What is hypoplasia?
Incomplete organ development (microcephaly)
What is a malformation?
Abnormal development of a structure (neural tube defects, cleft lip or palate, congenital heart defect)
What are the extrinsic errors of embryonic development?
Disruption and deformation
What is disruption?
External force leads to normal tissue growth arrest (amniotic band syndrome occurs when fibrous bands in amniotic cavity constrict growth of limbs or digits)
What is deformation?
External force leads to abnormal growth but not arrest, resulting in deformed or misshaped structures (potter sequence of syndrome is when the fetus is exposed to decreased amniotic fluid so the face and limbs are deformed because of lack of cushioning
What does exposure to teratogens during the first two weeks do?
Spontaneous abortion or no effect
What does exposure to teratogens during weeks 3-8 do to the baby?
This is when organogenesis occurs. It is a period of susceptibility, a period of maximum sensitivity to teratogens and when errors in morphogenesis are most likely to occur.
What effect do teratogens have 9 weeks until birth.
The organs are mature and the fetus rapidly grows. Exposure during this time disrupts growth and function.
What is a sequence?
A sequence is a primary anomaly itself resulting in additional defects
When is the embryo most susceptible to teratogen induced Limb malformations.
Weeks 4-5 because this is when limb patterning begins
What are reduction defects?
When part of (meromelia) or the entire limb (Amelia) is missing.
What are duplication defects?
This is when extra limb elements are present.
What is dysplasia?
This is malformation of part of the limb.
And example of this is abnormal fusion of the digits resulting from reduced apoptosis. Fingers do not separate into 5 regions
What occurs during the first week of embryogenesis?
Fertilization, cleavage, blastocyst formation and implantation
What are the Pluripotent stem cells and trophoblast cells of the embryo?
The pluripotent stem cells can give rise to any type of cell in the body, but not the placenta. The outer cells or trophoblast cells around the inner mass And blastocyst cavity;they form the fetal part of the placenta.
What happens by week two of embryogenesis?
The embryo blast and trophoblast each differentiate into two layers.
What happens at the end of week two in embryogenesis?
3 things
-The embryo has two layers: the epiblast and hypo blast.
-The trophoblast has two layers: the synctiotrophoblasts and cytotrophoblast
-two cavities form: the amniotic cavity and chorionic cavity
^the yolk sac is blastocyst cavity lined with hypoblast cells
What happens during week three of embryogenesis?
Establishment of the three germ layers that will give rise to all adult issues: the ectoderm, mesoderm and endoderm arise.