Ch.10 Part 2 repro.pdf

CHAPTER 10 PART 2 Pregnancy Embryonic Period (weeks 3-5) During the embryonic period all major internal and external features take shape. Very susceptible to disturbance during this time period. Week 3: the neural tube begins to develop (brain and spinal cord). Week 4: Eyes, otic pits, pharyngeal...

CHAPTER 10 PART 2 Pregnancy Embryonic Period (weeks 3-5) During the embryonic period all major internal and external features take shape. Very susceptible to disturbance during this time period. Week 3: the neural tube begins to develop (brain and spinal cord). Week 4: Eyes, otic pits, pharyngeal arches, and heart. Week 5: rapid brain expansion, limb bud differentiation for hands Human Reproductive Biology, 4th Ed. (2014) pg. 189 Embryonic Period (weeks 6-8) Week 6: pigmentation in eyes, hind limb bud differentiation for feet, brain/head now half the size of the embryo, finger rays emerge. Week 7: toe rays emerge, intestinal development which protrudes at the umbilical region. Week 8: now 1.25 inches long, eyelids, fingers and toes clearly visible, tail bud has disappeared. Human Reproductive Biology, 4th Ed. (2014) pg. 189 Fetal Period From 9 weeks post-fertilization – birth. Further growth and development of the systems established during the embryo phase. Week 12 – fetal heart beat can be detected 4-5 months – carrier can feel fetal movement 6 months – skin covered in fatty secretions (vernix caseosa) and downy hair (lanugo) Weeks 25-38 – gain fat and skin stretches, respiratory system last to develop Human Reproductive Biology, 4th Ed. (2014) pg. 191 Positioning Human Reproductive Biology, 4th Ed. (2014) pg. 191 As the developing fetus grows, the uterus must enlarge to accommodate its growth. As the uterus grows, other organs within the abdominal and pelvic region of the carrier are temporarily displaced. In addition to organ displacement, the muscles and skin of the abdominal area must stretch (and sometimes separate) to accommodate the growing fetus. Digestive/Urinary System Most of the developing fetus’s nutrients are coming from the carrier through the umbilical cord in the umbilical vein. • Includes sugars, amino acids, fatty acids, vitamins and minerals. Wastes produced by the fetus then pass back into the carrier via the umbilical arteries. Later on in gestation, the fetus will swallow amniotic fluid, which provides some additional nutrients. Although urine is excreted by the developing fetus, fecal matter generally is released once the baby is born. Circulatory System Important to keep in mind that the umbilical vein carries the oxygenated blood, and the umbilical arteries carry deoxygenated blood. Human Reproductive Biology, 4th Ed. (2014) pg. 192 Three mechanisms of diversion: ductus venosus, foramen ovale, and ductus arteriosus Nervous System The nervous system begins development very early on, around week 8. Early development of the nervous system allows for neuromuscular coordination early on. Sensory nervous system allows for detection of stimuli in utero: sound, light, temperature, and touch. Endocrine System Already discussed the role of FSH and LH in sex determination and reproductive system maturation. hCG may also play a role in gonadal development. Pancreas secrets insulin so fetus can utilize glucose. Two hormones involved in amniotic fluid function: prolactin and arginine vasotocin (AVT). https://www.rcsb.org/structure/1rw5 Fetal Disorders Approximately 30% of preembryos die prior to implantation. Another 30% die after implantation but before next menstrual period. 10% more die after the missed menstrual period. In total only 1/3 of all embryos created result in a live birth. Of those which make it to through birth, ~2% are born with major congenital disorders. Genetic/Chromosomal Abnormalities Several chromosomal/genetic abnormalities are related to congenital disorders. Approximately 1/200 newborns have some form of genetic/chromosomal abnormality Some are mild (colour blindness) and other are quite severe. Some abnormalities can lead to permanent disability (physical and/or cognitive). Common examples: cleft palate/lip, club foot, atypical skeletal presentations, heart/lung defects. https://www.mayoclinic.org/diseases-conditions/cleftpalate/symptoms-causes/syc-20370985 Rhesus Disease A.k.a Rh incompatibility – affects any future fetus carried by the carrier, but not usually the original fetus. Occurs when carrier is Rh- and sperm donor is Rh+ This creates a scenario where the fetus could be Rh+ and the carrier will develop antibodies against the Rh antigen. If a second pregnancy with an Rh+ fetus occurs, carriers antibodies will attack it. https://www.mountsinai.org/health-library/diseasesconditions/rh-incompatibility Interfering Substances and Agents Many substances (alcohol, drugs, environmental contaminants) and agents (viruses and bacteria, radiation) can cause harm to the developing child. Particularly susceptible during embryo development. https://pubchem.ncbi.nlm.nih.gov/compound/Thalidomide Are often mutagenic, causing damage to DNA, or are teratogenic, affecting fetal growth and development pathway. Viruses and Bacteria Many viruses are implicated in fetal death and severe defects/damage. These viruses include HIV, smallpox, chickenpox, mumps, herpes, and rubella. Although bacteria cannot pass as easily to the developing fetus, several can still cause harm. Syphilis, pneumonia, tuberculosis, typhoid, and even bacterial vaginosis can be damaging. https://my.clevelandclinic.org/health/diseases /17798-rubella Environmental Pollutants Especially damaging during weeks 4-7 of embryo development. Prior to this there is a higher chance of killing the embryo, afterwards the effects are reduced. Includes: mercury, lead, cadmium, arsenic, PCBs, DDR, benzene, and carbon tetrachloride. Minimata disease – fish containing mercury from fertilizer contamination. https://www.minamatadiseasemuseum.net/10things-to-know Drugs, Alcohol, and Tobacco Most sever negative effects during the first trimester. Includes therapeutic drugs as well (ex. NSAIDS). Major incident in the 1950s/60s with thaliodomide prescriptions to help with morning sickness and 1940s-70s with synthetic estrogen diethylstilbestrol which was meant to prevent miscarriage. Alcohol is able to pass across the placental barrier. Chronic use of alcohol (3 oz + daily) increases risk of fetal alcohol syndrome. Several nontherapeutic drugs can also cross the placenta barrier and lead to drug addiction and increased rates of miscarriage. Raditation Exposure to radiation can be harmful to the developing child as it acts as a mutagen. Xrays use to be used to monitor pregnancies in the early 1950s. https://www.hopkinsmedicine.org/health/treat ment-tests-and-therapies/xrays Babies exposed to radiation are at a higher risk of developing birth defects. This has been found in babies exposed to radiation fall out of atomic bombs an nuclear weapons. Fetal Evaluation Amniocentesis – genetic abnormalities, weeks 14-16. Chorionic villus sampling (CVS) – weeks 8-10, faster results but higher risk. Fetoscopy – abdominal incision with viewing window, week 15-20. Ultrasound – helpful for assessing heart beat, number of developing fetuses, little risk. Human Reproductive Biology, 4th Ed. (2014) pg. 197 Carrier Nutrition In general, caloric intake must increase both during pregnancy and lactation. Specific key nutrients: protein, iron, calcium folic acid, and vitamin B6. Recommended weight gain is on average 25lbs – less than half of that being fat. Exercise is recommended and based heavily on carriers prior exercise routine. https://www.walmart.ca/en/ip/jamieson-folic-acid1000-mcg-tablets-unisex/6000101672342 Physical Changes of Carrier The cardiovascular system output increases as blood volume increases by 45-50%. Blood pressure often also increases. Overall red blood cell count only increases 20-30%. Heart rate and respiratory rate both increase. These both help to pump more oxygen dense blood to the developing child. Kidneys enlarge and increase filtration rate by 50%. Endocrinology of Carrier Progesterone from the corpus luteum helps to establish the placenta and increases fat depositions. hCG prevents the corpus luteum from regressing. hCG is potentially regulated by GnRH from the placenta. Around week 5 the placenta begins to secrete several estrogens: mainly estriol. Progesterone is also secreted by the placenta. This continues throughout pregnancy and involved the fetal adrenal glands. Placenta also produces human placental lactogen (hPL). Helps increase glucose for fetal nutrition. Human Reproductive Biology, 4th Ed. (2014) pg. 199 Pregnancy Complications During pregnancy several milder symptoms may occur. Constipation, headaches, varicose veins, and heartburn are all very common. Some serious complications can develop which put the developing fetus and carrier at risk. • Preeclampsia • Gestational diabetes • Ectopic pregnancies • Miscarriage Preeclampsia (toxemia) Develops in months 8-9 in 6-7% of pregnancies. Most common in primiparous/multiparous carriers over age 35, black carriers, those with hypertension, and obesity. Cause is linked to a failure of trophoblast cells to penetrate deep into uterine blood vessels to retrieve adequate blood supply for the fetus. Not found in other mammals. Mild forms treated with diet/monitoring, severe requires premature delivery. https://www.baptisthealth.com/blog/mother-and-babycare/mild-vs-severe-preeclampsia-symptoms Gestational Diabetes Fairly common, occurring in 1/350 in the US. The carrier’s cells do not respond well enough to insulin. Causes an increase in blood glucose levels and abnormally large fetuses (macrosomia). In response, the fetus will increase blood insulin levels. Once born this causes a drastic drop in circulating glucose and hyperglycemia. Controlled through diet, exercise, and in severe cases medication. https://www.mountsinai.org/health-library/diseasesconditions/gestational-diabetes Ectopic Pregnancy Occurrence rate of 1% in US. Most occur as tubal pregnancies (96%), and rest are abdominal pregnancies (4%). Higher risk of carrier death in tubal pregnancies. https://www.verywellfamily.com/ruptured-ectopicpregnancy-symptoms-and-signs-2371253 Abdominal pregnancies calcify and turn into stone babies. Risk factors include age, multiparious carriers, non-whites, previous pelvic inflammation/endometriosis, certain forms of birth control use (mini pill, IUD, tubal sterilization). Other Complications Hydatidiform Moles – embryo implants and then development of chorionic villi is abnormal resulting in a fluid-filled cystic tumor. Septic Pregnancy – bacteria enter the uterus and severe infection occurs. Hemorrhage – excessive uterine bleeding during or immediately following delivery. Commonly associated with placenta previa and abruptio placenta. https://my.clevelandclinic.org/health/dis eases/17889-molar-pregnancy Miscarriage Nearly half of all zygotes/preembryos spontaneously abort – miscarry – right before or after implantation. Roughly 15% of established pregnancies result in miscarriage, highest during first trimester. Rate is higher in older carriers. Most individuals who miscarry can have a successful pregnancy afterwards. Some carriers functionally infertile. Some markers for increased risk are known: B1-glycoprotein – low levels after week 9 associated with miscarriage. Chances of Successful Pregnancy Of those pregnancies which reach full term, 87% involve healthy newborns. 11% are born with minor congenital defects, while 2% are born with severe congenital defects. Pregnancy risk of death for carrier in Canada is 11/100000. (0.0011%) Human Reproductive Biology, 4th Ed. (2014) pg. 202