Explain The Molecular Basis Of Fertilization Flashcards

Order of prenatal development zygote, cleavage, morula, blastocyst, embryo, fetus process that makes it possible for sperm to penetrate the egg is called capacitation In the slow block to polyspermy, sperm penetration releases an inflow of ___________, which in turn stimulates the ________. Ca2+; cortical reaction In the fast block to polyspermy, binding of sperm opens up _________ channels, which depolarizes the egg membrane and _________ Na+; prevents the entrance of any more sperm The optimal "window of opportunity" to conceive a child is a few days before ovulation to less than a day after The spheroidal stage of early prenatal development with about 16 to 64 cells is called a/an Morula Twins produced when a single egg is fertilized are called _____________ twins, and twins produced from two eggs ovulated at the same time are called ___________ twins monozygotic; dizygotic In the blastocyst, the trophoblast will become ____________, whereas the embryoblast will become __________ part of the placenta; the embryo Primary germ layers are formed during gastrulation Mesenchyme gives rise to muscle, bone and blood During implantation, the trophoblast divides into a deep layer, the _________, composed of individual cells, and a superficial layer, the ___________, composed of a multinucleate mass of cytoplasm cytotrophoblast; syncytiotrophoblast By the time the conceptus arrives in the uterus it consists of 16 or more cells Out of the 300 million ejaculated sperm, only about ____________ reach the vicinity of the egg 3,000 Prior to ejaculation, __________ in the sperm plasma membrane prevents premature release of ______________ cholesterol; acrosomal enzymes These are derivatives of ectoderm except the dermis The first body cavity is called the coelom By the end of 8 weeks, the individual is considered a fetus because all of the organ systems are present The ___________ completely encloses the embryo and provides a stable environment for it. amnion The ___________ encloses all the rest of the membranes and the embryo chorion The embryonic membrane that forms the fetal portion of the placent the villous chorion As it implants, the conceptus is nourished by means of trophoblastic nutrition The vessel that provides oxygenated blood to the placenta is a maternal artery In fetal circulation, the __________ bypasses the liver and the _________ bypasses the lung ductus venosus; ductus arteriosus In fetal circulation, blood bypasses the lungs by flowing through the foramen ovale and ductus arteriosus Which of the following major events of prenatal development happens first? -eyes are fully open-body covered with lanugo-bone calcification begins-central nervous system begins to form-meconium accumulates in intestines the central nervous system begins to form Oxygenated blood reaches the fetus through the umbilical vein The embryonic membranes include all of the following except the placenta _______ pass(es) from the maternal blood to the fetal blood; while fetal _________ pass(es) the other way Oxygen and nutrients; wastes The digital rays of a fetus give rise to fingers and toes The first 6 weeks of postpartum life constitute the neonatal period The fossa ovalis is a remnant of the ___________ of the fetus foramen ovale During birth, an infant is normally stimulated to breathe by CO2 accumulating in the baby's blood Which organ system shows the greatest anatomical change in the transitional period after birth? Circulatory Infant respiratory distress syndrome (IRDS) is caused by deficiency of pulmonary surfactant. Which organ system faces the greatest physiological challenge in the transitional period after birth? Respiratory A teratogen is most likely to cause a deformity of the limbs. These are have potentially teratogenic effects except-smoking-alcohol-infectious diseases-sunlight-x-rays sunlight. Down syndrome (trisomy-21) results from nondisjunction. The most likely outcome of nondisjunction is the production of a gamete receiving 22 chromosomes. Only autosomal trisomies involving chromosomes 13, 18, and 21 are survivable. why would this be? These are relatively gene-poor chromosomes. Urine retention is a greater problem for elderly men than for elderly women because men usually develop benign prostatic hyperplasia. Muscular weakness tends to develop in old age for all of the following reasons except:-aged muscle has less glycogen, myoglobin, and creatine phosphate.-there are fewer motor neurons in the spinal cord.-aged muscle fibers have fewer myofibrils.-there are fewer and smaller mitochondria.-myocytes do not synthesize myosin anymore. myocytes do not synthesize myosin anymore. Older people may require lower drug doses than younger people because they have lower rates of renal clearance. Telomeres are DNA segments at each end of a chromosome. The observation that there is a limit to how many times a cell can divide is the basis for the replicative senescence theory. Clinical death is widely defined as brain death. Which of the following systems shows the least overall senescence? endocrine system Senescence of the immune system makes older people more subject to cancer and infectious disease because of a decline in antigen-presenting cells and helper T cells. Congenital anomalies can result from all of the following except-an infectious disease in the mother during pregnancy.-genetic disorder-exposure to teratogens during pregnancy-smoking during lactation-smoking during pregnancy smoking during lactation.