Embryology Lecture Flashcards
5/29/19
Mitosis
Asexual reproduction, forms 2 identical daughter cells with no mechanism for genetic diversity, undergoes Interphase, prophase, etc
Meiosis
Sexual reproduction, forms 4 haploid gametes with diverse spread of genes through crossing over and homologous recombination to create egg and sperm
Sex hormone release pathway
Hypothalamus -> GnRH -> pituitary gland -> gonadotropin -> FSH/LH
Embryonic age
Number of days since fertilization (Clinically relevant right now)
Gestational age
Number of days since start of ovarian cycle (Don’t worry about this) (embryonic age + 2 weeks)
Zygote
One cell stage of fertilized ovum before first cleavage occurs
Morula
Ball of cells composing the early embryo that produces both the embryo and the placenta and membranes - each cell is totipotential
Blastocyst
The stage that follows the morula stage. It consists of a fluid filled cavity surrounded by trophoblasts with embryoblast cells at one pole.
Trophoblast
Cells outside the blastocele, becomes the placenta
Embryoblast
Inner cell mast inside blastocele, becomes the embryo
Embryoblast
Inner cell mast inside blastocele, becomes the embryo
Fertilization occurs in the…
…distal third of the fallopian tube
What occurs 3-4 days after ovulation
Entrance in the uterine cavity
What occurs 5-6 days after ovulation
HCG levels rise, tropoblast releases enzymes that erode the uterine lining for implantation
What occurs 7-12 days post ovulation
Trophoblast cells engulf and destroy cells of the uterine lining to create blood pools, stimulate capillary growth and develop placenta
Where do ectopic pregnancies occur?
Implantation in the distal third of the fallopian tube, sometimes elsewhere as well
***Epiblast vs hypoblast
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***The first week of fertilization is…
…all or none - you either implant or misscarry
What does ectoderm form?
Epithelium and communicating (nervous tissue) structures
What does mesoderm form?
Moving structures bone, cartilage, muscle, ligament, blood
What does endoderm form?
Excretory structures, GI, respiratory, urinary
Sacrococcygeal teratoma
Leftover primary streak containing all 3 cell types, easily removed without issue
Why do dermatomes form the way they do?
They are lined up linearly on the neural fold, but projection of the limbs causes distortion of them
Why do dermatomes form the way they do?
They are lined up linearly on the neural fold, but projection of the limbs causes distortion of them
Female develops due to ________ of hormones
Absence
Female develops due to ________ of hormones
Absence
Exposure to toxins within first 9 weeks causes… exposure beyond that causes…
…greatest damage during development…minor or small changes in the infant
Meconium
product of cell loss, digestive secretion and swallowed amniotic fluid in an embryo (essentially feces)
By 24-26 weeks, what can the fetus do?
Live outside of the body
What point do doctors consider inducing labor?
40 weeks or more
What point do doctors consider inducing labor?
40 weeks or more
Week 3 major points
Primitive streak, neural plate development
finish it
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