2009 Lecture 3
From Embryology
Week 1 and 2
Introduction
Following fertilization the first week is a series of rapid cell divisions, still contained within the zona pellucida, and still floating and being propelled within the uterine tube towards the uterine body. At the end of the first week and within the second week the process of implantation and early differentiation of cells that will form the embryo and the placenta.
Lecture Overview
- Week 1-2 of human development
- Fertilization options - In vitro fertilization
- Zygote, Morula, Blastocyst
- Cell layers - Trophoblast, Syncytiotrophoblast, Cytotrophoblast, Embryoblast
- Implantation - Normal, Ectopic, Uterine changes, Blastocyst implantation changes
Fertilization Options
- Natural sex
- Artificial insemination of mother with father's sperm, with mother with donor sperm, with egg and sperm donors, using surrogate mother
- In vitro fertilization (IVF) using egg and sperm of parents
- Intra-Cytoplasmic Sperm Injection (ICSI), frozen embryos, pre-implantation Genetic Diagnosis (PGD), egg donor, sperm donor, egg and sperm donor, surrogate using parents' egg and sperm, surrogate and egg donor, surrogate and sperm donor, surrogate using her egg and sperm from baby's father, surrogate using egg and sperm donors
Formation of Zygote
- male and female pronuclei, 2 nuclei approach each other and nuclear membranes break down
- DNA replicates, first mitotic division
- sperm contributes centriole which organizes mitotic spindle
Cleavage of Zygote
- cleavage of zygote forms 2 blastomeres and is cleavage with no cytoplasm synthesis
- special "embryonic" cell cycle S phases and M phases alternate without any intervening G1 or G2 phases (MSMSMSMS, adult MG1SG2) therefore individual cell volume decreases
- cell division is initially synchronous, then asynchronously
- slow- centre cells, larger fast- peripheral cells
Morula
- about day 4 is a solid ball of 16-20 cells with peripheral cells flattened against zona pellucida
- compaction occurs forming a cavity and leading to blastocyst
Blastocyst
- about day 5 have 2 identifiable cell types and a fluid-filled cavity (blastoceol)
- trophoblast layer - peripheral flattened cells
- inner cell mass - embryoblast, mass of rounder cells located on one wall of the blastocoel
UNSW Embryology Links
Glossary Links
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Next Lecture
- Dr Mark Hill 2009 UNSW CRICOS Provider Code No. 00098G
