Marc was a participant in a clinical study to determine how much niacin cures pellagra, the niacin deficiency disease. During the study, he consumed only a formula diet that was deficient in niacin. After developing pellagra, he was given 2 mg of niacin a day for 2 weeks, but he still suffered from the disease, so the scientists added 2 mg of the vitamin to Marc's formula. By the beginning of the 5th week of the study, the researchers noticed that Marc's signs and symptoms were greatly improved. At the end of the 5th week, he was feeling fine. The researchers concluded that:

prophase: we can observe the chromosomes to coil up and condense. they become visible. nuclear membrane and envelope disintigrate.s

metaphase: chromosomes align at the center, the metaphase plate. spindle fibers attach to centromeres of the sister chromatids. they meet at kinetochores.

anaphase: sister chromatids are pulled towards each opposing centromere, set on different poles.

telophase: chromosomes are now clustered up only on either sides of the cell. nuclear membranes reform, and a new cell wall forms along the cell plate. this will lead to cytokinesis, the process that divides the cell membrane and forms the cell wall.

trachea, alveoli, lung capillaries, arteries

the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

i hope this : )