oral histo pdf

• Cytomorphosis refers to the changes a cell undergoes during various stages of its existence.
• The cell cycle is the ordered sequence of events that a cell undergoes from its origin, divided into interphase and mitosis.
• Physiological cell death, also known as apoptosis, is a natural and controlled process crucial for maintaining tissue homeostasis, development, and eliminating damaged cells.
• Pathological cell death, such as necrosis, is a consequence of external factors like infections, toxins, or trauma, and tends to be uncontrolled, causing inflammation and potentially harming surrounding tissues.
• Static cells are terminally differentiated (permanent) cells that are not actively dividing or changing, and cannot be replaced when lost.
• Renewing/labile cells are continuously dividing throughout an individual’s life, have a high regenerative capacity, and are typically found in tissues with a high turnover rate like the epidermis of skin, blood cells, and mucosa of mouth.
• Facultative/stable cells are cells that are in a non-dividing state but can re-enter the cell cycle and divide when stimulated, needed, or when cells are lost.
• The morula, characterized by a spherical appearance and is made up of blastomeres, which are the individual cells produced during cleavage, is the next stage after the blastula.
• The spermatozoa determine the sex of embryo during fertilization.
• The genetic sex of zygote is determined during fertilization.
• The blastocoel, a fluid-filled cavity in the blastula, is the site where the embryo implants.
• During early stages of cleavage, the zona pellucida acts as a porous filter through which certain substances can reach the egg.
• The cells derived during cleavage stage are known as blastomeres.
• The diploid chromosome number is restored during fertilization.
• The zona pellucida, which protects the embryo and acts as a filter to provide needs of zygote, is present during cleavage stage.
• The cleavage stage ends with the formation of blastula.
• Hardening of the zona pellucida is crucial to ensure that only one sperm successfully fertilizes the egg, maintaining the correct chromosome number and preventing genetic abnormalities.
• Division of cells in early embryo is known as cleavage stage.
• The zygote undergoes a rapid cell cycle with no significant increase in size of zygote during cleavage stage.
• With the onset of puberty, a portion of these primary oocytes is activated each menstrual cycle.
• Fertilization is the fusion of a sperm cell nucleus and an egg cell nucleus, which takes place in the oviduct.
• Sperm and egg nuclei fuse.
• The secondary oocyte is released from the ovary during ovulation and enters the fallopian tube.
• Ejaculation produces about 5ml of semen which contains 450 million sperm.
• Sperm and nucleus enter egg.
• Spermatozoa has to penetrate four layers before it fertilizes.
• Egg becomes activated and undergoes developmental changes.
• The zona pellucida serves as a barrier that normally allows any sperm of the same species access to the egg.
• The activated primary oocyte undergoes meiosis I, resulting in the formation of a secondary oocyte and a smaller polar body.
• Sperm contacts egg.
• The sperm uses both chemical and physical means to penetrate the corona radiata or the protective layers surrounding the egg.
• The zona pellucida becomes hardened, creating a barrier that prevents other sperm from penetrating the already fertilized egg.
• These changes include the zona reaction, which involves changes in the glycoproteins of the zona pellucida, making it impermeable to additional sperm.
• The ovum is about 85,000 times larger than a sperm cell.
• The fertilized egg is called the zygote.
• Females are born with a finite number of primordial follicles, each containing an immature egg cell.
• If fertilization occurs, the secondary oocyte completes meiosis II, resulting in the formation of a mature ovum and another polar body.
• Trophoblast develops into placenta, which is the outer layer of cells in the blastocyst.
• Before birth, some primordial follicles develop into primary oocytes (immature egg cells) and enter a state of meiotic arrest.
• Ectoderm, the outermost layer of cells in the blastocyst, includes the sweat glands, hair follicles, epithelial lining of mouth, tooth enamel, adrenal medulla, and sense receptors.