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Stack #2724152
developmental
| Question | Answer |
|---|---|
| Developmental biology | study of the sequence of events from the fertilization of a mature ovum by a sperm cell to the formation of an adult organism |
| embryonic period | from fertilization through the eighth week of development |
| fetal period | begins at week 9 and continues until birth occupies the remainder of pregnancy, from the 9th through the 40th week Tissues and organs that developed during embryonic period continue to grow and differentiate fetus is less vulnerable to the damaging eff |
| neonatal period | covers the first 28 days after birth |
| Fertilization | about seven hours after ejaculation, sperm are not capable of fertilization ne capacitated sperm must penetrate the corona radiata (granulosa cells left over from the 3o follicle) and the zona pellucida (a clear glycoprotein layer between the corona radi |
| process called capacitation | perm involved in the final action undergo a series of functional changes that cause their tails to beat even more vigorously and prepare their plasma membranes to fuse with that of the 2o oocyte’s -Only capacitated sperm are capable of responding to the |
| Embryonic Period - | several rounds of cell division, 3-4 days after fertilization a solid ball of cells (blastocyst) enters the uterine cavity |
| Implantation | is the attachment of the blastocyst to the endometrium 7–8 days after fertilization |
| formation of a embryonic disc and 4 extraembryonic membranes | The embryonic disc is composed of cells which develop to become the fetus The extraembryonic membranes will form the amniotic sac around the developing embryo, the umbilical cord and placenta |
| rapid rate of cell division at the time | leaves the developing embryo very susceptible to teratogens (can cause -incomplete closure of the spinal tubes -eyes and heart, -major organs are affected -low birth rate ) |
| embryonic disc, | visible as early as 3 weeks post-fertilization, develops into the 3 primary germ layers, from which all the tissues of the embryo derive |
| Ectoderm | differentiates into the tissues of the brain and nerves, and the epidermis of the skin |
| Mesoderm | is a loosely organized connective tissue (mesenchyme) that matures to form blood, muscles, bones, and other connective tissue derivatives |
| Endoderm | gives rise to the epithelial lining of the digestive tract, respiratory tract, and several other organs; also the smooth endothelial lining of blood vessels |
| placenta | formed by the chorionic villi of the embryo and the decidua basalis of the endometrium of the mother. -site of nutrient and waste exchange by diffusion, yet prevents any mixing of fetal and mothers blood |
| placenta functions before | Forms a barrier between mother and embryo (blood is not exchanged) Delivers nutrients, oxygen and IgG (maternal antibodies) Removes waste from embryonic blood Becomes an endocrine organ (produces hormones) and takes over for the corpus luteum Es |
| Teratogens | can cross the placental barrier and cause serious developmental abnormalities and sometimes death, especially during the embryonic period |
| rate of fetal growth | During the last 2.5 months of intrauterine life, half of the full-term weight is added head becomes more proportionate to body By week 3; fetus assumes upside-down position preparation for labor |
| Gestation | time of prenatal development; 40 weeks (9 months), divided into 3 3-month trimesters |
| First Trimester | embryological and early fetal development; organ systems laid down |
| Second Trimester: | development of organ systems |
| Third Trimester | rapid fetal growth; organ systems functional eighth week of embryonic development, all the organ systems have been laid down in rudimentary form |
| 3 weeks | Notochord forms, which will form the brain and spinal chord The heart begins to form as a single tube which is able to contract Preg sign- Breast Changes, Amenorrhea, Nausea, vomiting |
| 6 weeks | Trachea has developed, lungs begin to develop fetal circulation begins Preg sign: Nausea, vomiting, Urinary Frequency, Positive Pregnancy Test Visualization on Ultrasound, Fetal Heart Sounds |
| 8 weeks: | all systems present in basic form head ~ 50% of body length; all major brain regions present bone formation begins Preg sign:Nausea, vomiting, Urinary Frequency, Positive Pregnancy Test |
| 9-12 weeks (3rd month): | bone marrow begins making blood cells sex can be detected from genitals Preg sign: Nausea, vomiting, Urinary Frequency, Fatigue, Positive Pregnancy Test |
| 13-16 weeks (4th month): | blinking of eyes and sucking motions occur body begins to outgrow head bones are distinct with joint cavities eyes and ears assume normal position and shape begins to look human Preg sign: Quickening, Braxton Hicks Contractions |
| 17-20 weeks (5th month): | vernix caseosa and langugo cover body Preg sign: Quickening Fetal Movements Palpated |
| 21-30 weeks (6th and 7th months): | substantial weight gain – may survive if born ~ 27 weeks) finger and toe nails are present testes enter scrotum in 7th month Fetal Movements Palpated |
| 30-40 weeks (term; 8th and 9th months): | fat laid down in subcutaneous tissue surfactant production adequate by ~ 32 weeks, post-partum levels by 35 |
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