HUMAN BODY ANATOMY

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HUMAN EMBRYOGENESIS (STEP 1-4)

- junio 30, 2018

Embryogenesis, the first eight weeks of development after fertilization, is an incredibly complicated process. It’s amazing that in eight weeks we’re transforming from a single cell to an organism with a multi-level body plan. The circulatory, excretory, and neurologic systems all begin to develop during this stage. Luckily, like with many complex biological concepts, fertilization can be broken down into smaller, simpler ideas. The big idea of embryogenesis is going from a single cell to a ball of cells to a set of tubes. Starting from the very beginning Step 1 : a zygote is the single cell formed when an egg and a sperm cell fuse; the fusion is known as fertilization Step 2 : the first 12-to 24-hours after a zygote is formed are spent in cleavage – very rapid cell division The zygote’s first priority is dividing to make lots of new cells, so it’s first few days are spent in rapid mitotic division. With each round of division, it doubles in c...

HUMAN EMBRYOGENESIS (STEP 5-7)

- junio 30, 2018

Making Tubes Step 5 : During gastrulation the three germ layers form; the cell mass is now known as a gastrula Step 5a : The primitive streak forms Step 6 : The notochord is formed Week 3 of development is the week of gastrulation . A germ layer is a layer of cells that will go on to form one of our organizational tubes. Our anatomy can really be boiled down to an inner tube (our digestive tract), and a series of tubes that wrap around it. The three germ layers that will translate into these tubes are the ectoderm , the mesoderm , and the endoderm . Germ Layer What does the prefix mean? Goes on to form: Ectoderm Outer, external Epidermis (outer layer of skin), hair, nails, brain, spinal cord, peripheral nervous system Mesoderm Middle Muscle, bone, connective tissue, notochord, kidney, gonads, circulatory system Endoderm Within Epithelial lining of the digestive tract; Stomach, colon, liver, pancreas, bladd...