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Human ova grow from primitive germ cells that are embedded in the substance of the ovaries. [10] The ovum is one of the largest cells in the human body, typically visible to the naked eye without the aid of a microscope or other magnification device. [11] The human ovum measures approximately 120 μm (0.0047 in) in diameter. [12]
An oocyte (/ ˈ oʊ ə s aɪ t /, oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction.In other words, it is an immature ovum, or egg cell.An oocyte is produced in a female fetus in the ovary during female gametogenesis.
The human eye is a sensory organ in the visual system that reacts to visible light allowing eyesight. Other functions include maintaining the circadian rhythm , and keeping balance . Arizona Eye Model.
In astronomy, the naked eye may be used to observe celestial events and objects visible without equipment, such as conjunctions, passing comets, meteor showers, and the brightest asteroids, including 4 Vesta. Sky lore and various tests demonstrate an impressive variety of phenomena visible to the unaided eye.
Human fertilization is the union of an egg and sperm, occurring primarily in the ampulla of the fallopian tube. [1] The result of this union leads to the production of a fertilized egg called a zygote, initiating embryonic development. Scientists discovered the dynamics of human fertilization in the 19th century. [2]
Among the most common methods of study is dissection, in which the corpse of an animal or a human cadaver is surgically opened and its organs studied. Endoscopy , in which a video camera-equipped instrument is inserted through a small incision in the subject, may be used to explore the internal organs and other structures of living animals.
Human reproduction naturally takes place as internal fertilization by sexual intercourse. During this process, the man inserts his erect penis into the woman's vagina and then either partner initiates rhythmic pelvic thrusts until the man achieves orgasm , which leads to ejaculation of semen containing sperm into the vaginal canal.
The first appearance of the gonad is essentially the same in the two sexes, and consists in a thickening of the mesothelial layer of the peritoneum.The thick plate of epithelium extends deeply, pushing before it the mesoderm and forming a distinct projection.