Development, Pregnancy, and Genetics Part 2 PDF

Development and Pregnancy Marie A. Román Martínez, PhD Department of Biology Office hours: by appointment Email: [email protected] Copyright-This presentation is intended for educational purpose only. No part of this presentation may be reproduced or transmitted in any form without written permiss...

Development and Pregnancy Marie A. Román Martínez, PhD Department of Biology Office hours: by appointment Email: [email protected] Copyright-This presentation is intended for educational purpose only. No part of this presentation may be reproduced or transmitted in any form without written permission. Objectives 1. Describe the processes of fertilization, pre-embryonic development, and implantation. 2. Explain the importance of the three germ layers. 3. Identify the extraembryonic membranes and their functions. 4. Describe the structure and function of the placenta. 5. Describe the fetal development. 6. Explain the fetal cardiovascular adaptations and their value to the fetus. 7. Describe the cardiovascular changes that occur in postnatal development. 8. Describe the control of lactation and milk ejection. 9. Describe disorders during pregnancy and the pre and post natal development. 2 Fetal Cardiovascular Adaptations Circulation in the fetus and adult are different. Mothers blood volume rises about 30%. 1 to 2 liters of extra blood Fetal digestive tract, lungs, and kidneys are not functioning. Oxygen and nutrients are obtained from maternal blood in the placenta. Carbon dioxide and other wastes are removed by maternal blood in the placenta. Umbilical vein carries O2 and nutrient-rich blood to fetus from placenta. Half of the blood enters the liver. Half enters the ductus venosus and into the inferior vena cava. 3 Fetal Cardiovascular Adaptations Ductus venosus empties blood into the inferior vena cava. Full blood flow through fetal liver is not necessary. Mother’s liver removed hazardous substances before her blood enters the placenta. Increases blood pressure in inferior vena cava and right atrium. Keeps the foramen ovale open. 4 Fetal Cardiovascular Adaptations Foramen ovale: Opening in the interatrial septum into the left atrium. Most venous blood entering right atrium flows into left atrium. Ductus arteriosus: Duct connecting the pulmonary trunk and aortic arch. Blood that does enter the right ventricle passes from the pulmonary trunk and into the aortic arch. Foramen ovale and ductus arteriosus help to bypass the nonfunctional fetal lungs. Send O2 and nutrient-rich blood directly to body, rather than to lungs first. Enough blood does enter the lungs to maintain lung tissue. 5 Fetal Cardiovascular Adaptations Umbilical arteries: Form from internal iliac arteries. Carry deoxygenated blood to placenta. 6 Postnatal Cardiovascular Changes Distal portion of umbilical arteries constrict. Inhibit flow to placenta. Umbilical arteries become the: Superior vesical arteries Medial umbilical ligaments Umbilical vein constricts: Becomes the round ligament Ductus venosus constricts: Becomes the ligamentum venosum in the wall of the liver. Umbilical cord stem cells 7 Postnatal Cardiovascular Changes Foramen ovale closes due to a decrease in right atrial pressure and increase in left atrial pressure. Becomes the fossa ovalis. Ductus arteriosus constricts: Becomes the ligamentum arteriosum. Changes are functionally complete within 30 min. Up to 1 year to make them permanent. 8 Lactation Lactation is the process of milk secretion. Maintained by a positive-feedback mechanism. Hypothalamus secretes prolactin-releasing hormone (PRH). PRH causes anterior lobe of pituitary gland to produce prolactin. After birth, blood levels of estrogens and progesterone drop, which allows prolactin to stimulate milk secretion 2 to 3 days after birth. In the meantime, the mammary glands produce colostrum. 9 Lactation For the first 3 days, mammary glands produce colostrum. Contains higher protein concentration and no fat. Provides boost of essential nutrients for protein synthesis. Needed for continued growth and development. After day 3, prolactin effects are seen on milk production. Secretion of prolactin and milk is maintained by mechanical stimulation of the nipples. Suckling triggers production of action potentials. Action potentials cause the hypothalamus to secrete PRH. PRH causes prolactin secretion. 10 Lactation Milk ejection (“letdown”) occurs approx. 30 second after suckling begins. Suckling triggers action potentials that are sent to the hypothalamus. Hypothalamus triggers the release of oxytocin from the posterior lobe. Stimulates contraction of specialized epithelial cells surrounding the ducts and alveolar glands in the mammary gland. Milk production continues as long as suckling continues. Volume of milk gradually declines. Cessation of suckling ends milk production in approx. 1 week. Breast-feeding advantages 11 12 13 Disorders of Pregnancy, Prenatal Development, and Postnatal Development Disorders are classified as: Pregnancy Disorders Prenatal and Postnatal Disorders 14 Pregnancy Disorders Eclampsia (toxemia of pregnancy) a disorder that occurs in two forms. 1. Preeclampsia Late pregnancy Increased blood pressure, edema, proteinuria (protein in the urine). 2. Eclampsia Can lead to convulsions and coma. High mortality for both fetus and mother. Pregnancy may need to be terminated. 15 Pregnancy Disorders Ectopic pregnancy: Implantation of pre-embryo anywhere except the uterus. Treatment is surgical removal of the embryo. 16 Pregnancy Disorders Morning sickness: Nausea and vomiting upon getting up in the morning. Lasts from 1 to 6 weeks. Cause unknown: High blood hCG and progesterone levels may play a role. Occurs in about 60% of women. 17 Prenatal and Postnatal Disorders Birth defects may be inherited or may be caused by a variety of teratogens. Teratogens Environmental agents that produce physical abnormalities during prenatal development. Example: alcohol, illegal drugs, therapeutic drug, X-rays, German measles (rubella). Generally, the earlier the embryo is exposed, the greater the defect produced. Alcohol is the most common teratogen. Fetal alcohol syndrome  characterized by a small head, intellectual disability; facial deformities; and abnormalities of the heart, genitals and limbs. 18 Prenatal and Postnatal Disorders Physiological jaundice: Postnatal disorder RBCs are destroyed faster than the liver can remove bilirubin, resulting in excess bilirubin in the blood. Phototherapy (UV light) speeds up bilirubin breakdown. Usually resolves once the newborn’s liver gains full function. Infant respiratory distress syndrome (IRDS): Postnatal disorder. Inability to produce surfactant within infant’s lungs. Decrease ability of infant to successfully inflate its lungs. Most common in premature infants. 19 Prenatal and Postnatal Disorders Sudden infant death syndrome (SIDS): Postnatal disorder Sudden death of infant with no medical history or explanation upon autopsy. Highest risk during sleep. Cause unknown: Risk factors include hypoxia, deficits in respiratory control, nicotine exposure during development. 20