BIOL10002 Lecture Notes - Lecture 30: Endometrium, Pyruvic Acid, Zygote

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2 Jul 2018
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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)

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