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Menstruation: The periodic shedding of the Endometrium and associated menstrual bleeding in the Menstrual cycle of humans and primates. Menstruation is due to the decline in circulating Progesterone, and occurs at the late Luteal phase when Luteolysis of the Corpus luteum takes place.

Oogenesis

JoVE 10906

In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from the equivalent procedure of spermatogenesis in males. First, meiotic divisions during oogenesis are asymmetric, meaning that a large oocyte (containing most of the cytoplasm) and minor polar body are produced as a result of meiosis I, and again following meiosis II. Since only oocytes will go on to form embryos if fertilized, this unequal distribution of cell contents ensures that there are enough cytoplasm and nutrients to nourish the early stages of development. Second, during oogenesis, meiosis “arrests” at two distinct points: once during embryonic growth and a second time during puberty. In mammals, oocytes are suspended in prophase I until sexual maturation, at which point meiosis I continues under hormonal influence until an egg precursor cell is released into a fallopian tube. At ovulation, the precursor exits the ovary and, only if fertilization occurs, is stimulated to complete meiosis II and form a complete egg. Defects during oogenesis can result in severe consequences. In particular, problems with chromosome segregation during either meiosis I or meiosis II may lead to an embryo being aneuploid, meaning that it contains an abnormal number of chromosomes. Increased age elevates a woman

 Core: Biology

Recording Brain Electromagnetic Activity During the Administration of the Gaseous Anesthetic Agents Xenon and Nitrous Oxide in Healthy Volunteers

1Centre for Human Psychopharmacology, Swinburne University of Technology, 2Department of Anaesthesia and Pain Management, St. Vincent's Hospital Melbourne, 3Brain and Psychological Science Research Centre, Swinburne University of Technology, 4Department of Anaesthesiology, University of Auckland

JoVE 56881

 Neuroscience

Autonomic Function Following Concussion in Youth Athletes: An Exploration of Heart Rate Variability Using 24-hour Recording Methodology

1Concussion Centre, Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital, 2Faculty of Kinesiology and Physical Education, University of Toronto, 3Rehabilitation Sciences Institute, Faculty of Medicine, University of Toronto, 4Department of Occupational Science and Occupational Therapy, Faculty of Medicine, University of Toronto

JoVE 58203

 Medicine
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