BIO 169 - Test 6: Pregnancy and Development Exam Questions and Answers Graded A

What is development? - The gradual modification of anatomical structures and physiological characteristics during the period from fertilization to maturity. What is fertilization? - Fertilization occurs when genetic material in sperm combines with that of a secondary oocyte to form a diploid zygote, first cell of the new individual cell of the new individual. Prenatal development is called.. - gestation. The first two months are called... - Embryological development Month 2-9 are celled... - Fetal development Fertilization - -Presence of multiple sperm are required to deliver adequate acrosomal enzymes to digest a path through the zona pellucida and corona radiata surrounding the secondary oocyte. When the first sperm contacts the secondary oocyte.. - the membranes fuse, and the cytoplasm and nucleus of the sperm enter the oocyte cytoplasm. Fusion of the membranes also causes.. - the oocyte nucleus to complete meiosis to form the ovum and the second polar body. Nuclei of the sperm and ovum fuse, and - the chromosomes are mixed to form the first diploid cell of the new individual, called a zygote. Cleavage - Over the next 6-7 days, the zygote undergoes several rounds of rapid mitosis without cell growth, which is called cleavage. This is to produce a hollow ball of small cells called blastocyst. As cleavage occurs within uterine tube, developing embryo is transported towards uterus by a combination of: - -peristaltic contractions of smooth muscle, and -action of cilia within uterine tubes Once within the uterus, the developing embryo is nourished by.. - secretions from the endometrial glands. Implantation - -Given a properly prepared endometrium and appropriate development of the blastocyst, implantation begins 7 days after ovulation Unfertilized oocytes survive.. - 2 days Sperm survive in female reproductive system for... - 3 days Upon arriving in the uterus, a properly developed blastocyst consists of.. - a sphere of trophoblast cells and a cluster of cells called the inner cell mass Upon making contact with the endometrium, trophoblast cells initiate formation of the placenta by: - -secreting factors that cause endometrium to thicken at the point of contact, and -proliferating and invading endometrium by digesting endometrial cells Invading trophoblasts cells, also release an LH-like hormone called HCG which... - -maintains the corpus lutuem (prevents menustration) -is detected by pregnancy test As the endometrium is eroded... - blastocyst burrows into and becomes surrounded by endometrium Implantation is usually complete by... - Day 12 post ovulation (it is a process not an event) Inner cell mass develops into.. - embryonic disk, which develops into fetus and most surrounding membranes