UNSW Embryology

Embryology for K12 Students

© Dr Mark Hill (2008)

Acknowledgements

Week 2

In the second week of development the dividing zygote forms a solid ball of cells and is now called a blastocyst. The cells on the surface of the ball will not form part of the embryo and will go on to make the placenta and membranes that surround the embryo. Inside the ball of cells a fluid filled space forms beside which is a small clump of cells. This small clump of cells (embryoblast) will form all the parts of the embryo.

During this second week the blastocyst will stick to the inside of the uterus and will no longer float free. This sticking process is required to allow the blastocyst to begin to get food from the mother. (You start as a single cell, how many cells are you now?)

Blastocyst

(More? Year 7-12 Detailed Embryology Notes - week 2)

Next

Go to Week 3 the ball of cells forms first connections with mother.

Facts

Most of the early important stages of embryo growth occur before the mother knows she is pregnant.

Words Used

Words Used

• blastocyst- a solid ball of cells that then forms a hollow ball of cells with a clump on the inside on one wall.
• egg- the cell from the mother that contributes half the genes of the embryo.
• embryo- the name given to the baby during the early time of growth.
• fertilization- A process where a single male (father) and female (mother) cell are joined together.
• genes- information in the cell that gives it rules on how to grow and what cell to become. This information is stored in DNA in the cell nucleus.
• sperm- the cell from the father that contributes half the genes of the embryo.
• uterus- the space within the mother where the embryo grows. It also grows when the embryo does and has lots of blood to feed the embryo and strong muscles in its walls for childbirth.
• zygote- The first cell formed after fertilization.

Quick Movie Links

Movie of Human Embryo Growth (this shows a human embryo growing, all images are to scale)

Movie of Limb Growth(this shows development of the human arm from bud to paddle, to hand with arm)

Movie of Mouse Embryo Growth (this shows a mouse embryo growing)

Movie of Rotating Embryo(this shows an early embryo from all angles)

All Moviesthis shows many different ways of looking in at changes in different embryos.

Quick Links

Week 1 | Week 2 | Week 3 | Week 4 | Week 5 to 8 | Week 9 to 12 | Week 13 to 15 | Week 16 to 20 |

Development Notes ----------------- Menstrual Cycle Week 1 Week 2 Week 3 Week 4 Placenta Serial Images Genes/DNA Molecular Dev Abnormal Dev Postnatal Dev Notes Index

System Notes ----------------- Heart/Cardiovascular Respiratory Coelomic cavity Gastrointestinal Tract Head and Neck Neural Neural Crest Eye Ear Nose Endocrine Urogenital Musculoskeletal Integumentary

Movies ----------------- Embryo Growth Ultrasound Week 1 Week 2 Week 3 Week 4 Stage 13/14 Stage 22 Neural Head and Neck Heart Vasculature Gastrointestinal Urogenital Other Embryos Larsen Internet

Other Embryos ----------------- Chicken Fly Frog Mouse Rabbit Rat Worm Zebrafish Guinea Pig

UNSW Embryology ISBN: 978 0 7334 2609 4

UNSW CRICOS Provider Code No. 00098G