Embryonic Development

• The human body is made up of cells, tissues, organs, organ systems, and the whole body.
• Mitosis: single cell division where one somatic cell duplicates its genetical material and splits into two identical daughter cells
• Meiosis: A type of double cell division of reproductive cells known as gametes that produces four haploid daughter cells from one diploid parent cell, haploid cells hold half the genetic information of the diploid parent cell
• Morula Stage: microscopic zygote (about 16 cells total), pre-embryonic, 24 hours into pregnancy
• Blastula Stage: 70-100 cells, fluid-filled sphere called the blastocoel (a term only used for mammals)
• Gastrula Stage: a hollow cup shape from as the blastocoel opens up, develops 3 germ layers
• Organogenesis Stage: the formation of all organs of the body, period of development from gastrula until the moment of birth
• Fertilisation: when two gametes, the paternal sperm and the maternal egg, fuse together to form a zygote.
• Mitosis is the fourth stage of the cell cycle. It consists of prophase, metaphase, anaphase, telophase
• Germ layers = endoderm, mesoderm, ectoderm
• Endoderm = inner layer, creates: digestive tract, respiratory tract, liver, pancreas, embryonic gut, glands
• Mesoderm = middle layer, creates: muscular-skeletal system, circulatory system, excretory system, dermis skin layer, supportive tissue, connective tissue
• Ectoderm = outer layer, creates: hair, lining of the nose and mouth, nervous system, brain, sweat glands, nails, epidermis skin layer, tooth enamel, some endocrine glands, cornea and lens of the eye
• Differentiation Potential: the unlimited potential of the zygote to differentiate its cells. Cells can develop into any cell type. As the organism develops, the differentiation potential decreases. Once developed enough, cells can no longer change, taking on one specific form and function
• Gene Expression = the regulation of genes so that some genetic traits are activated and others are deactivated during the course of development. This is why some people's hair darkens as they age.
• The lungs are one of the final organs developed in gestation