Ovum model and Fertilisation Fertilization Fertilization is the

Ovum model and Fertilisation

Fertilization Fertilization is the union of egg and sperm Occurs in Fallopian Tubes (usually) 200 million sperm to one egg! (sometimes 2, 3 or more eggs!). When 1 sperm penetrates the zona pellucida (clear zone around egg), cortical granules are released that prevent any other sperm from penetrating the egg After fertilization, the egg and sperm and nuclei fuse, and a new diploid human zygote results (2 n) - the first cell of the new animal

Cleavage of zygot Cleavage: The first days and weeks after conception: mitotic cell divisions begin, converting the zygote to a multicellular organism Day 1: first cleavage - 1 cell becomes 2 Day 2: second cleavage - 4 -cell stage Day 3: 6 -12 cell stage - can test at this stage for genetic diseases if done by IVF Day 4: 16 -32 cell stage - solid ball of cells morula

Morula develops Day 5: Solid morula develops into hollow, fluidfilled blastula The embryo will develop from the inner cell mass, or embryonic disc

Im pl an ta t io n Day 6 -7: Blastocyst attaches to the endometrium and burrows in: implantation.

Gastrulation Days 7 -10: Gastrulation: major cellular reorganization into 2 or 3 tissue (germ) layers: -Ectoderm: skin, nervous system -Endoderm: lining of gut and internal organs -Mesoderm: muscles, bones, heart Gastrula: Early embryo with 3 tissue layers. All cells have the same DNA; however, different cells now begin to "turn on" (or "express") different genes to become different organs.

c i n o y r b Em Days 10 - 14: Pregnancy becomes established -Fluid filled amniotic cavity starts to form -Yolk sac starts to form (will make blood cells, germ cells) -Embryo starts to form from embryonic disc - Chorion (placenta) starts to form At the end of this stage, a woman will have just missed her period!

y d Bo n a Pl Days 15 - 21: Emergence of the vertebrate body plan Primitive streak starts to form - this is the site of gastrulation (formation of the 3 tissue layers - ecto, endo, and mesoderm) Neural groove (future spinal cord and brain) begins to form Somites (bands of tissue that will become muscles and bones) begin to form Pharangeal arches (future face, neck, mouth, nose) begin to form

Embryonic Development Days 21 on. . . Week 3 - Week 8 (Embryo) - Development of all organ systems Day 22: Cardiac cells (early heart) begins to beat. Day 24 embryo shown at right

How you looked at 1 month past conception. . ? And now for the rest of development. . . Here come the organs!

FETUS BECOME Week 4 -8 is whan all the major organ systems of the body are formed and when most teratogens have their greatest effect

The Baby’s development finished After 12 weeks or so, the baby's development is largely "finished" - except brain and lung development

Week 20 - Love that thumb!

Week 36 - 40 - Partruition. . !

Keep Our Baby The early processes of development all need to occur at a precise time and place - that is why poor maternal nutrition, fever, drugs, alcohol, (particularly in the 1 st trimester) all have potentially serious effects of the developing baby. However, ALSO remember that ~9, 000 human babies are born EVERY HOUR of every day (a net increase of 2. 5 babies per second, or about 80 million every year!*) and the vast majority are healthy and perfectly formed, even sometimes under adverse conditions

Kelas 8 Senin, 8 Agustus ulangan chapter 1. Growth and development. (I jam pelajaran).