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Professor, University of Florida College of Medicine

Radiation should only be considered when it is effective and potentially beneficial for the diagnosis or treatment of the patient. Needless or excessive exposures are not justified, and patients should be guaranteed that the treatment given is reliable and that the individuals administering the radiation are adequately trained. Regulations must be in place to facilitate informed and rational decision making, and to protect against unwise choices [7. Governments should authorize regulatory bodies, give them the funding and authorization to develop rules to carry out relevant laws and policies, and ensure that the regulatory body is effectively independent in its safety related decision making. Roles and responsibilities of the regulatory body A single regulatory body is rarely responsible for all radiation safety related activities. Coordination is critical to ensure there are no gaps or overlaps in regulatory authority. Memoranda of understanding, regular meetings and communication/coordination should be used to achieve a comprehensive working regulatory environment. Regulatory authority over the use of radiation in medicine may be the responsibility of one ministry or may be shared between several ministries. Regulatory authority may be shared among several levels of government, such as federal, state, provincial, regional and local governments. An example could be that patient protection would be the responsibility of the ministry of health, while regulation of the possession of radioactive material would be the responsibility of the ministry of the environment, and educational requirements and worker safety would be the responsibility of the ministry of labour. Some governments may have a department of radiation protection which would be responsible for all aspects of radiation protection and safety. Regulatory authority may be shared between different levels of government, for example importing of sources would be controlled by the federal government, but the qualification of medical personnel may be the responsibility of the local health authority. However, the government should ensure that all radiation safety related responsibilities are assigned to a relevant authority in order to ensure that there is no gap in responsibilities in relation to radiation safety related activities. Potential registrants and licensees should be aware of the situation within their country. Potential registrants or licensees may need to assist in promoting the development of these regulatory requirements. They were established to protect people and the environment from harmful effects of ionizing radiation. Responsibilities of the government Ultimately, the government is responsible, either through its actions or through the actions of others, via regulations, inspection and enforcement, to ensure the safety of the public and the environment. An active regulatory programme that performs all of these activities (authorization, inspection and enforcement) is essential to ensure the safe use of radiation in medicine. Most governments have some general regulatory requirements and some specific requirements that should be considered prior to establishing radiotherapy in a country. The government is responsible for establishing and maintaining the legal and regulatory framework (regulatory body), establishing regulations and guides, enabling inspections and enforcement of the regulations, and issuing guidelines for radiation protection and safety. Responsibilities of the regulatory body the regulatory body should adopt regulations that are commensurate with the characteristics of the practice or the source within a practice, and with the magnitude and likelihood of the exposures. The requirements will vary from location to location, and are usually based on the complexity and risk of exposure of people and the environment. For planned exposures in medicine (diagnostic and therapeutic), the registrant or licensee should be prepared to comply with regulations concerning general radiation safety as well as specific regulations concerning the safe use of radiation in medicine. Some of the issues that should be considered by the regulatory body when promulgating regulations include: Notification and authorization; Review and assessment of facilities and activities; Inspection of facilities and activities; Enforcement of regulatory requirements; the regulatory function relevant to emergency exposure situations and existing exposure situations; - Provision of information to , and consultations with, parties affected by its decisions and, as appropriate, the public and interested parties. Responsibilities of the registrant or licensee Registrants and licensees will need to establish and implement technical and organizational measures for the types of activities they are performing. They may need to establish a radiation protection or safety committee and appoint a 112 - - - - - radiation protection officer who is qualified to perform tasks associated with radiation protection and safety. Some of the duties of a radiation protection officer are to: communicate with the regulatory body to inform it of, and to gain authorization for, the possession and use of radiation devices; develop or coordinate the development of operating procedures; arrange for protection and safety; perform periodic reviews; maintain records; and inform management of these activities. Some of the activities that could be assigned to the radiation protection officer are testing and performing or overseeing maintenance of the equipment, surveying restricted areas, record keeping, and acting as a point of contact for reporting accidents and incidents to the regulatory body. The radiation protection officer may also be part of the management team or may be a consultant with contractual obligations to respond on behalf of the registrant or licensee.

At the time of ovulation, the oviduct shows active movements that bring the infundibulum and fimbria close to the ovary. Cilia on the surface of the fimbria sweep the ovum into the ampulla of the oviduct where fertilization, if it is to occur, takes place. The human ovum remains fertile for between 24 and 48 hours, after which it degenerates if fertilization does not occur. Approximately 300 million sperm are released into the vaginal lumen during coitus but it is estimated that only 300-500 spermatozoa reach the site of fertilization. Muscular contractions within the walls of the uterus and oviduct propel the spermatozoa to the proximal region (ampulla) of the oviduct where fertilization takes place. The smooth muscle cells are thought to contract in response to prostaglandins and/or oxytocin released during sexual intercourse. Of the millions of sperm initially deposited in the female tract, only one penetrates the ovum. There is no evidence for chemotactic attraction, and random movement brings sperm and ovum together. The zona pellucida is important in fertilization as it provides sperm recognition sites for sperm binding and is the most efficient trigger of the sperm acrosome reaction. The acrosome reaction results in the release of acrosomal enzymes (acrosin and trypsinlike enzymes) needed to digest a hole in the zona pellucida. At the time of fertilization, when a spermatozoon pushes through the hole in the zona pellucida to enter the ovum, a period of hyperactivity of flagellar beat occurs, propelling the spermatozoon into the ovum. Thus, flagellar beat appears to be more important at the moment of fertilization rather than getting to the site of fertilization. Electron micrographs suggest that the plasma membranes of the sperm and ovum fuse, that of the spermatozoon being left at the surface of the ovum. Penetration is followed by release of electron-dense cortical granules that underlie the plasmalemma of the ovum (cortical granule reaction) and by immediate changes in the permeability of the zona pellucida, which thereafter excludes entry by any additional competing sperm (polyspermy). The ovum now completes the second maturation division and extrudes the second polar body. The nucleus (head) of the spermatozoon swells and forms the male pronucleus, and the sperm body and tail are resorbed. The two pronuclei move to the center of the cell, and two centrioles, supplied by the anterior centriole of the spermatozoon, appear. The chromatin of each pronucleus resolves into a set of chromosomes that align themselves on a spindle to undergo a normal mitotic division of the first cleavage. Each cell resulting from this division receives a full diploid set of chromosomes. The cells are bounded by the zona pellucida, and a mulberry-like body, the morula, is formed. Cleavage is a fractionating process: no new cytoplasm is formed, and at each division the cells become smaller until a normal, predetermined, cytoplasmic-nuclear ratio is reached. Cleavage occurs as the morula slowly is moved along the oviduct by the waves of peristaltic contractions in the muscle coat. The fluid increases in amount, the intercellular spaces become confluent, and a single cavity, the blastocele, is formed. The morula has now become a blastocyst that forms a hollow sphere containing, at one pole, a mass of cells called the inner cell mass that will form the embryo proper. The capsule-like wall of the blastocyst consists of a single layer of cells, the trophoblast. After reaching a critical mass, the blastocyst breaks through the surrounding zona pellucida and remains free within the uterine cavity for about a day; then it attaches to the endometrium, which is in the secretory phase. Encasement within the zona pellucida protects the forming blastocyst from the possible damaging effects of oviductal movements, possible adverse effects of oviductal and uterine secretions, and/or destruction by maternal tissues until it reaches a critical mass for survival. During cleavage, the zona pellucida progressively thins and coupled with the expansion of the blastocoele, the blastocyst hatches and crawls through and out of the surrounding zona pellucida. The hatched blastocyst makes contact with the maternal endometrial surface through apposition of its trophectoderm to the uterine lining epithelial cells. The initial contact is mediated by cell surface oligosaccharides that play an important role in recognition, adhesion and attachment to the uterine epithelium. Following these events, trophoblast cells penetrate between surface uterine epithelial cells and establish direct contact with underlying decidual cells.

The glands vary in size and consist of a cluster of two to five oval alveoli drained by a single duct. The secretory alveoli lie within the dermis and are composed of epithelial cells enclosed in a welldefined basement membrane and supported by a thin connective tissue capsule. Cells abutting the basement membrane are small and cuboidal and contain round nuclei. The entire alveolus is filled with cells that, centrally, become larger and polyhedral and gradually accumulate fatty material in their cytoplasm. Secretion is of the holocrine type, meaning the entire cell breaks down, and cellular debris, along with the secretory product (triglycerides, cholesterol, and wax esters), is released as sebum. Myoepithelial cells are not observed with sebaceous glands, but the glands are closely related to the arrectores pilorum muscle. Contraction of this smooth muscle bundle helps in the expression of secretory product from the sebaceous glands. In the nipple, smooth muscle bundles are present in the connective tissue between the alveoli of these glands. The short duct of the sebaceous gland is lined by stratified squamous epithelium that is a continuation of the outer epithelial root sheath of the hair follicle. Replacement of secretory cells of the alveolus comes mostly from division of cells close to the walls of the ducts, near their junctions with the alveoli. Collectively, the hair follicle, hair shaft, sebaceous gland, and erector pili muscle are referred to as the pilosebaceous apparatus. The pilosebaceous apparatus produces hair and sebum, the latter of which protects the hair and acts as a lubricant for the epidermis to protect it from the drying effects of the environment. Sebaceous glands become more active at puberty and are under endocrine control: androgens increase activity, estrogens decrease activity. Eccrine sweat glands are distributed throughout the skin except in the lip margins, glans penis, inner surface of the prepuce, clitoris, and labia minora. Elsewhere the numbers vary, being plentiful in the palms and soles and least numerous in the neck and back. The deep part is tightly coiled and forms the secretory unit located in the deep dermis. The secretory unit consists of a simple columnar epithelium resting on a thick basement membrane. These cells secrete glycoproteins, which have been identified in secretory vacuoles. Intercellular canaliculi extend between adjacent clear cells, which contain glycogen, considerable smooth endoplasmic reticulum, and numerous mitochondria but few ribosomes. Clear cells are thought to secrete sodium, chloride, potassium, urea, uric acid, ammonia, and water. Myoepithelial cells are present around the secretory portion, located between the basal lamina and the bases of the secretory cells. These stellate cells are contractile and are believed to aid in the discharge of secretions. Eccrine sweat glands are drained by a narrow duct that at first is coiled and then straightens as it passes through the dermis to reach the epidermis. At their luminal surfaces, the cells of the inner layer show aggregations of filaments organized into a terminal web. In the epidermis, the duct consists of a spiral channel that is simply a cleft between the epidermal cells; those cells immediately adjacent to the duct lumen are circularly arranged. When eccrine sweat glands function to regulate body temperature they are regulated by postganglionic sympathetic neurons that release acetylcholine as the neurotransmitter (cholinergic innervation). In contrast, when eccrine sweat glands are involved in emotional sweating they are controlled by postganglionic sympathetic neurons that release norepinephrine (adrenergic innervation). Their secretions are thicker than those of the ordinary eccrine sweat glands and contain glycoproteins, lipids, glycolipids and pheromones. Their histologic structure also differs from eccrine sweat glands in several respects.

Uterus the human uterus is a single, hollow, pear-shaped organ with a thick muscular wall; it lies in the pelvic cavity between the bladder and rectum. The nonpregnant uterus varies in size depending on the individual but generally is about 7 cm in length, 3 to 244 the middle layer is the thickest and shows no regularity in the arrangement of the smooth muscle cells, which run longitudinally, obliquely, circularly, and transversely. This layer also contains many large blood vessels and has been called the stratum vasculare. The outer layer of smooth muscle consists mainly of longitudinally oriented cells, some of which extend into the broad ligament, oviducts, and ovarian ligaments. Elastic fibers are prominent in the outer layer but are not present in the inner layer of the myometrium except around blood vessels. New smooth muscle cells are produced in the pregnant uterus from undifferentiated cells and possibly from division of mature cells also. The connective tissue of the myometrium also increases in amount during pregnancy. In spite of a total increase in muscle mass, the layers are thinned during pregnancy as the uterus becomes distended. After delivery, the muscle cells rapidly decrease in size, but the uterus does not regain its original, nonpregnant dimensions. The myometrium normally undergoes intermittent contractions that, however, are not intense enough to be perceived. The contractions are diminished during pregnancy, possibly in response to the hormone relaxin. At parturition, strong contractions of the uterine musculature occur, causing the fetus to be expelled. This hormone is synthesized by neurons forming the supraoptic and paraventricular nuclei of the hypothalamus and released at the neurohypophysis. In the body of the uterus, the endometrium consists of a thick lamina propria (endometrial stroma) and a covering epithelium. The stroma resembles mesenchymal tissue and consists of loosely arranged stellate cells with large, round or ovoid nuclei supported by a network of fine connective tissue in which lymphocytes, granular leukocytes, and macrophages are scattered. There is no submucosa, and the stroma lies directly on the myometrium, to which it is firmly attached. The stroma is covered by a simple columnar epithelium that contains ciliated cells and nonciliated secretory cells. The epithelium dips into the stroma to form numerous uterine glands that extend deeply into the stroma, occasionally penetrating into the myometrium. The endometrium can be divided into a stratum basale (basal layer) and a stratum functionale (functional layer), which differ in their structure, function, and blood supply. The stratum basale is the narrower, more cellular, and more fibrous layer and lies directly on the myometrium. Occasionally, small pockets of stratum basale may extend into the myometrium, between muscle cells. This layer undergoes few changes during the menstrual cycle and is not shed at menstruation but serves as the source from which the functional layer is restored. The stratum functionale extends to the lumen of the uterus and is the part of the endometrium in which cyclic changes occur and which is shed during menstruation. The stratum functionale sometimes is subdivided into the compacta, a narrow superficial zone, and the spongiosa, a broader zone that forms the bulk of the functionalis. The blood supply of the endometrium is unique and plays an important role in the events of menstruation. Branches of the uterine arteries penetrate the myometrium to its middle layer, where they furnish arcuate arteries that run circumferentially in the myometrium. One set of branches from these arteries supplies the superficial layers of the myometrium, while other branches, the radial arteries, pass inward to supply the endometrium.