BIOL10002 Lecture Notes - Lecture 30: Endometrium, Pyruvic Acid, Zygote
Lecture 30
Development – part 1
Reproduction
The ovary doesn’t use glucose, it uses carboxylic acids to support it dormancy
restrictive mitosis reduces the volume of the oocyte
Day 3-4 embryo begins to turn on genes received from the sperm
Tight junctions between cells forms an epithelium – compaction
fluid is pumped in via aquaporins with sodium-potassium HTPase to form a blastocyst
the zona pellucida protects the embryo from implanting early (eptopic pregnancy)
the embryo and uterus produce proteases to break open the zona pellucida
Steps of embryonic development
1. Cleavage
slices up
slow (12-24 hours per division)
little or no yolk
first cleavage (vertical) produces blastomere, second horizontal (i.e. rotational division) => these
divisions form the multicellular embryo
initial steps depend on mRNA and proteins stored in the egg
2. Compaction
keeps slicing a little but also compacts into a morula
have large flat trophoblast cell (become placenta) and an inner cell mass (becomes the embryo)
8-cell embryo => cadherin membrane (cadherin form tight junctions between cells)
tight junctions create polarity makes bag or oranges turn into a soccer ball
basal membrane is different to the apical surface = polar
this process is calcium dependent: the process can be reversed without calcium
3. Blastulation/Cavitation
A blastocyst forms (in humans specifically), or a bastocyte in everything else
sodium potassium ATPase – 3 Na in 2 K out : ion gradient therefore water goes in and forms a
blastocyst
The blastocyst:
high QO2 => high capacity to utilise glucose
generates energy from aerobic glycolysis and the oxidation of glucose
4. Zona hatching
fluid accumulation
zona pellucida gets thinner and thinner as proteases weaken it, and the turgid pressure causes it to
burst
Preimplantation
Pyruvate used as energy => (anaerobic) quiescent
5. Implantation
Occurs day 8-9 after fertilisation – endometrium only ‘ready’ for 2-3 days
embryo goes all the way into the myometrium (invasive) – other embryos (eccentric) do not go
into myometrium
surges of estrogen and progesterone prepare endometrium to receive blastocyst
hCG from egg tells corpus luteum to keep pumping out estrogen and progesterone
The zygote post implantation
low QO2 => limited ability to utilise glucose
generate majority of its energy from pyruvate and/or lactate with aspartate=
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Document Summary
The ovary doesn"t use glucose, it uses carboxylic acids to support it dormancy. Restrictive mitosis reduces the volume of the oocyte. Day 3-4 embryo begins to turn on genes received from the sperm. Tight junctions between cells forms an epithelium compaction. Fluid is pumped in via aquaporins with sodium-potassium htpase to form a blastocyst. The zona pellucida protects the embryo from implanting early (eptopic pregnancy) The embryo and uterus produce proteases to break open the zona pellucida. Steps of embryonic development: cleavage slices up. First cleavage (vertical) produces blastomere, second horizontal (i. e. rotational division) => these divisions form the multicellular embryo. Initial steps depend on mrna and proteins stored in the egg: compaction keeps slicing a little but also compacts into a morula. Have large flat trophoblast cell (become placenta) and an inner cell mass (becomes the embryo) 8-cell embryo => cadherin membrane (cadherin form tight junctions between cells)