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Embryology
| Question | Answer |
|---|---|
| study of the origin and development of a single individual | Embryology |
| Embryonic period and major events | first 8 weeks Major events: Organs form from three primary germ layers. The basic body plan emerges. |
| Fetal period | remaining 30 weeks Major events: Organs grow in size and complexity. |
| Look at slide 6 in PP CHAP-3 to see the basic body plan | Look at slide 6 in PP CHAP-3 to see the basic body plan |
| in lateral third of uterine tube Zygote (fertilized oocyte) moves toward the uterus Cleavage—daughter cells formed from zygote | Fertilization |
| solid cluster of 12–16 blastomeres | Morula |
| fluid-filled structure of ~ 60 cells | Blastocyst |
| forms embryo | Inner cell mass |
| helps form placenta | Trophoblast |
| Stages of first week | Zygote 4-cell Morula Early blastocyst Late blastocyst (implants at this stage) |
| Look at slide 9 in PP CHAP-3 to see fertilization and the first 6 days of development | Look at slide 9 in PP CHAP-3 to see fertilization and the first 6 days of development |
| inner cell mass divided into two sheets | Bilaminar embryonic disc |
| Together they make up the bilaminar embryonic disc | Epiblast and the hypoblast |
| formed by an extension of epiblast | Amniotic sac |
| Outer membrane of amniotic sac | amnion |
| Inner membrane of amniotic sac | amniotic sac cavity (filled with amniotic fluid) |
| formed by an extension of hypoblast | Yolk Sac |
| Digestive tube forms from: | Yolk Sac |
| The Yolk Sac is NOT a major source of nutrients for embryo | The Yolk Sac is NOT a major source of nutrients for embryo |
| Tissues around yolk sac give rise to | earliest blood cells and blood vessels |
| Look at slide 13-15 in PP CHAP-3 to see implantation of the blastocyst | Look at slide 13-15 in PP CHAP-3 to see implantation of the blastocyst |
| raised groove on the dorsal surface of the epiblast | Primitive streak |
| a process of invagination of epiblast cells Begins at the primitive streak Forms the three primary germ layers | Gastrulation |
| Three Germ Layers | Endoderm—formed from migrating cells that replace the hypoblast Mesoderm—formed between epiblast and endoderm Ectoderm—formed from epiblast cells that stay on dorsal surface *All layers derive from epiblast cells |
| a swelling at one end of primitive streak | Primitive node |
| forms from primitive node and endoderm | Notochord |
| defines body axis | Notochord |
| Is the site of the future vertebral column Appears on Day 16 | Notochord |
| ectoderm starts forming brain and spinal cord | Neurulation |
| ectoderm in the dorsal midline thickens | Neural plate |
| ectoderm folds inward | Neural groove |
| a hollow tube pinches off into the body | Neural tube Cranial part of the neural tube becomes the brain Maternal folic acid deficiency causes neural tube defects |
| Cells originate from ectodermal cells Forms sensory nerve cells | Neural crest |
| Ability of one group of cells to influence developmental direction of other cells | Induction |
| our first body segments; 40 pairs Paraxial mesoderm | Somites |
| begins as a continuous strip of tissue just lateral to the paraxial mesoderm Each segment attached to a somite | Intermediate mesoderm |
| most lateral part of the mesoderm | Lateral plate |
| becomes serous body cavities | Coelom |
| next to the ectoderm | Somatic mesoderm |
| next to the endoderm | Splanchnic mesoderm |
| “Tadpole shape” by Day (blank) after conception | 24 |
| encloses tubular part of the yolk sac Site of future digestive tube and respiratory structures | Primitive gut |
| Derivatives of the germ layers | Ectoderm forms Brain, spinal cord, and epidermis Endoderm forms Inner epithelial lining of the gut tube Respiratory tubes, digestive organs, and urinary bladder |
| differentiates further and is more complex than the other two layers | Mesoderm (Somites and intermediate mesoderm Somatic and splanchnic mesoderm Notocord) |
| Somites divide into: | Sclerotome Dermatome Myotome |
| Intermediate mesoderm forms | Kidneys and gonads |
| Forms musculature, connective tissues, and serosa of the digestive and respiratory structures Forms heart and most blood vessels | Splanchnic mesoderm |
| Somatic mesoderm forms: | Dermis of skin Bones Ligaments |
| Look at slide 35 in PP CHAP-3 to see Major Derivatives of Embryonic Germ Layers | Look at slide 35 in PP CHAP-3 to see Major Derivatives of Embryonic Germ Layers |
| Embryo first looks recognizably human in week | 8 (Head is disproportionately large All major organs are in place) |
| Normal births occur how many weeks after conception | 38 |
| Birth that occurs before 38 weeks | Premature birth |
| Look at slide 38-40 in PP CHAP-3 to see Developmental Events of the Fetal Period | Look at slide 38-40 in PP CHAP-3 to see Developmental Events of the Fetal Period |
Created by:
sl1512
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