Early landmarks Flashcards
(Day 0) Capacitation
Maturation process of the sperm that results in hyperactivity and activation of the sperm’s acrosomal coat
(Day 0) Acrosomal reaction
Acrosome releases enzymes upon reaching zona pellucida to degrade it
(Day 0) Fast block the polyspermy
Occurs once sperm has fused to membrane of the oocyte, allowing Na+ to enter the cell, depolarizing oocyte and repelling other sperms
(Day 0) Slow block to polyspermy
Cascade of events that occurs because Calcium enters the cell, causing changes to oocyte membrane and prevents other sperms from binding to receptors on the oocyte membrane
(Week 1) Morula
16 to 32 cell stage - resides in cervical os
(Week 1) Blastocyst
Free of zona pellucida (prevents premature implantation)
Inner cell mass (embryoblast)
Outer cell mass (trophoblast)
Week of 2s - Germ Layers (Bilaminar Disc)
embryoblast reorganizes into:
- hypoblast (ventral layer)
- epiblast (dorsal columnar cells adjacent to amnion)
Week of 2s - Cavities
- amniotic (dorsal to epiblast)
2. yolk sac (ventral to the hypoblast)
Week of 2s - Placental Layers
trophoblast organizes into:
- cytotrophoblast - inner proliferative layer that provides additional trophoblast cells
- synctiotrophoblast - thick outer layer without cell boundaries that invades the endometrim as the chorionic villi
Week of 2s - Extraembryonic Mesoderm Layers
Derived from yolk sac – a loose connective tissue that forms between the trophoblast and embryoblast
Splits to line tropho/embryo (remains connected at the connecting stalk, which later becomes the umbilical cord)
- splanchnopleuric - inner layer lining embryo
- somatopleuric - lining inner surface of cytotrophoblast
(Week 2) Lacunae
Connections between synctiotrophoblast and maternal vessles that form primitive uteroplacental circulation
(Week 2) Decidual Reaction
Cells in decidua (functional layer of the endometrium) enlarge b/c accumulate lipid and gluyogen to provide nourishment for the embryo until placenta is vascularized
Week of 3s - Germ Layers (Gastrulation)
Primitive node/streak near caudal end forms in epiblast layer
- Ectoderm - remaining epiblast
- Mesoderm - new layer formed between old layers
- Endoderm - Original hypoblast displaced by definitive endoderm from overlying epiblast cells
Week of 3s - Cavities
- Chorionic - from the extraembryonic mesoderm being “opened up”
- Amniotic
- Yolk
Week of 3s - Three Placental Layers
- Synctiotrophoblast
- Cytotrophoblast
- Chorionic mesoderm (from extraembryonic lining the inside of the cytotrophoblast cells)
Week of 3s - Three Body Axis
- Craniocaudal
- Dorsoventral
- Right-left
(Week 3) This is derived from mesoderm, formed during gastrulation, and sends signals for the induction of the neural tube, somites, and other surrounding structures
Notochord
Resides in the middle of the mesoderm and induces a thickening of the ectoderm above it that eventually forms a neural tube
This begins as a diverticulum of the yolk sac at the posterior wall
Allantois
(Weeks 3-8) Neural tube formation begins at ______ and closes by Week ___.
1) Neck region
Proceeds in both caudal and cranial directions
Cephalic is completed first
2) Closes by Week 4
(Weeks 3-8) The paraxial mesoderm lies next to (“para”) the ________
Neural tube
(Weeks 3-8) The intermediate mesoderm lies between (“intermediate”) __________
Paraxial and Lateral Mesoderm
(Weeks 3-8) The lateral mesoderm lies _______ to the other mesodermal segments
Lateral
The heart begins to beat during Week ___
3-4
The upper and lower limb buds begin to form during Week __
3-4
“4 weeks, 4 limbs”
By Week ___, genitalia have male or female characteristics
10
By Week ___ muscle and cartilage formation begins
4-5
By Week ___ cardiac septa form and AV cusions fuse
4-5
By Week ___ craniofacial development begins
4-5
