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January 23, 2014 Morphogenesis.docx
January 23, 2014 Morphogenesis.docx

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York University
Natural Science
NATS 1610

The loving Body – Morphogenesis -chapter 16/17 -Embryonic period: extends from the 3 to the 8 week, pre-embryo now called embryo, • Period of morphogenesis o Development of the body form o Tissues and organs form • By the end of the embryonic period distinct human appearance (all organs have been formed) -Major events during embryonic period 1. Gastrulation a. Movement of cells within the inner cell mass b. Forming primary germ layers – ectoderm, mesoderm, endoderm c. Embryo during this period is called a gastrula 2. All the tissues develop from the primary germ layers – the organs develop 3. A notochord develops from the mesoderm a. Providing the long axis of the embryo b. The vertebral column later forms in this region 4. Neurulation follows a. To form the central nervous system b. Embryo during this period is called neurula 5. Organs and anatomical features form -gastrulation begins the process by which the developing embryos (gastrula) body takes shape and becomes organized • During implantation - inner cell mass moves from surface to blastocyst • Inner cell mass flattens – plate like structure – embryonic disk – becomes embryo • Amniotic cavity forms – lined by amnion – filled with amniotic fluid -cells of embryonic disk differentiate (change and specialize) and migrate inward forming 3 primary germ layers (ectoderm, mesoderm, endoderm) -totipotent: cell that can divide and produce all of the differentiated cells in an organism, including extraembryonic tissues. Is capable of developing into any cell type (only Morula cells are totipotent -Pluripotent: cell that has the potential to differentiate into any of the 3 germ layers and give rise to any fetal or adult cell type. Cannot develop into an organism because cannot contribute to ectraembryonic tissue -Multipotent: cell that can give rise to cells from multiple but limited cell lineages – i.e. hemoatopietic cells are blood cells that can develop into any type of blood cell only -Unipotent: can differentiate into only one cell type -The development of organs can be related to the three germ layers • Different sets of cells within each layer develop differently • Some groups of cells migrate to localized regions of embryo • Organs are communities of tissues – work co-operatively -Organ origins • Ectoderm – outer layer o Nervous system, spinal cord, brain, epidermis of skin, hair, nails, oil glands, sweat glands, mammary glands, portions of eyes & teeth, and epithelial lining of mouth & rectum & digestive tract • Mesoderm – middle layer o All connective tissues including muscle, bone, blood, de
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