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Oocyte (or ovum/egg) activation is a series of processes that occur in the oocyte during fertilization. Sperm entry causes calcium release into the oocyte. In mammals, this is caused by the introduction of phospholipase C isoform zeta (PLCζ) from the sperm cytoplasm. [ 1 ]
The sperm plasma then fuses with the egg's plasma membrane and their nuclei fuse, triggering the sperm head to disconnect from its flagellum as the egg travels down the fallopian tube to reach the uterus. In vitro fertilization (IVF) is a process by which egg cells are fertilized by sperm outside the womb, in vitro.
In animals, egg cells are also known as ova (singular ovum, from the Latin word ovum meaning 'egg'). [7] The term ovule in animals is used for the young ovum of an animal. In vertebrates, ova are produced by female gonads (sex glands) called ovaries. A number of ova are present at birth in mammals and mature via oogenesis.
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 female germ cells produce a primordial germ cell (PGC), which then undergoes mitosis ...
The zona pellucida is an extracellular matrix that surrounds the plasma membrane of the egg cell. It helps protect the egg, and has an essential role in fertilization by sperm. It is surrounded by the corona radiata. The corona is composed of cells that care for the egg when it is emitted from the ovary. [1]
In anatomically simple animals, such as cnidarians and flatworms, the fetal development can be quite short, and even microlecithal eggs can undergo direct development. These small eggs can be produced in large numbers. In animals with high egg mortality, microlecithal eggs are the norm, as in bivalves and marine arthropods.
In humans, CD27 is a good marker for plasma cells; naïve B cells are CD27−, memory B-cells are CD27+ and plasma cells are CD27++. [5] The surface antigen CD138 (syndecan-1) is expressed at high levels. [6] Another important surface antigen is CD319 (SLAMF7). This antigen is expressed at high levels on normal human plasma cells.
The cortical reaction is a process initiated during fertilization that prevents polyspermy, the fusion of multiple sperm with one egg.In contrast to the fast block of polyspermy which immediately but temporarily blocks additional sperm from fertilizing the egg, the cortical reaction gradually establishes a permanent barrier to sperm entry and functions as the main part of the slow block of ...