By T. Urkrass. Bethel College and Seminary, Saint Paul Minnesota. 2017.
This type of epithelium is Movement of the epithelial cells away from the supportive base- confined to the linings of the large ducts of sweat glands order levitra soft 20 mg amex, salivary ment membrane is accompanied by the production of keratin (ker′a˘- glands, and the pancreas, where its stratification probably pro- tin) (described below), progressive dehydration, and flattening. There are two types of stratified squamous epithelial tis- sues: keratinized and nonkeratinized. Keratinized stratified squamous epithelium contains ker- atin, a protein that strengthens the tissue. Keratin makes Transitional epithelium is similar to nonkeratinized stratified the epidermis (outer layer) of the skin somewhat waterproof squamous epithelium except that the surface cells of the former and protects it from bacterial invasion. The outer layers of are large and round rather than flat, and some may have two nu- the skin are dead, but glandular secretions keep them soft clei (fig. Nonkeratinized stratified squamous epithelium lines the permit distension (stretching) of the urinary bladder as it fills oral cavity and pharynx, nasal cavity, vagina, and anal with urine. This type of epithelium, called mucosa (myoo-ko′sa˘), being rounded when the urinary bladder is empty to being some- is well adapted to withstand moderate abrasion but not what flattened as it distends with urine. The cells on the exposed surface are alive and are A summary of membranous epithelial tissue is presented in always moistened. Stratified squamous epithelium is the first line of defense against the entryof living organisms into the body. Stratification, Body Membranes rapid mitotic activity, and keratinization within the epidermis of the skin are important protective features. An acidic pH along the surfaces of Body membranes are composed of thin layers of epithelial tissue this tissue also helps to prevent disease. Body membranes cover, separate, and sup- gion is about 6, and the pH along the vaginal lining is 4 or lower.
LH regu- lates the secretion of testosterone by the Leydig cells and Anterior pituitary FSH cheap levitra soft 20mg without a prescription, in synergy with testosterone, regulates the produc- tion of spermatozoa. FSH LH Inhibin Follistatin Hypothalamic Neurons Produce Testes Gonadotropin-Releasing Hormone Activin Hypothalamic neurons produce gonadotropin-releasing Testosterone hormone (GnRH), a decapeptide, which regulates the se- cretion of luteinizing hormone (LH) and follicle-stimulat- Accessory ing hormone (FSH). Although neurons that produce Behavior Secondary sex GnRH can be located in various areas of the brain, their reproductive characteristics tissues highest concentration is in the medial basal hypothalamus, in the region of the infundibulum and arcuate nucleus. GnRH enters the hypothalamic-pituitary portal system and The main reproductive hormones are shown in binds to receptors on the plasma membranes of pituitary boxes. Positive and negative regulations are depicted by plus and minus signs, respectively. A variety of external cues and internal signals influence the secretion of GnRH, LH, and FSH. For example, the structures, which produce sperm and hormones; a ductal amount of GnRH, FSH, and LH secreted changes with age, system, which stores and transports sperm; and accessory stress levels, and hormonal state. Little, if any, The endocrine glands of the male reproductive system secretion of hypothalamic GnRH occurs in patients with include the hypothalamus, anterior pituitary, and testes. GnRH moves down the hypothalamic- nadal from a deficiency in LH and FSH secretion because pituitary portal system and stimulates the secretion of LH of a failure of GnRH neurons to migrate from the olfactory and FSH by the gonadotrophs of the anterior pituitary. These patients do binds to receptors on the Leydig cells and FSH binds to re- not have a sufficient hypothalamic source of GnRH to ceptors on the Sertoli cells. Leydig cells reside in the inter- maintain secretion of LH and FSH, and the testes fail to un- stitium of the testes, between seminiferous tubules, and dergo significant development. Sertoli cells are located within the GnRH originates from a large precursor molecule called seminiferous tubules, support spermatogenesis, contain preproGnRH (Fig. PreproGnRH consists of a signal FSH and testosterone receptors, and produce estradiol, al- peptide, native GnRH, and a GnRH-associated peptide beit at low levels. The signal peptide (or leader sequence) allows the Testosterone belongs to a class of steroid hormones, the protein to cross the membrane of the rough ER. Sertoli cells also produce glycoprotein hormones— nhibin, activin, and Three distinct pituitary LH- and FSH-secreting cells have follistatin—that regulate the secretion of FSH. Gonadotrophs contain either LH or FSH, The duct system that transports sperm from the testis to and some cells contain both LH and FSH.
A baseline assessment of cognitive function is desired prior to initiating immunomodulating therapy c buy discount levitra soft 20mg line. A family is concerned that a patient may have cognitive impairment, but the patient denies any problems and there is no clinical evidence for such impairment d. The patient reports cognitive deficits that, although subtle or fluctuating, may have functional impact 29. Which of the following strategies is unlikely to help patients with severe cognitive deficits? Which of the following is probably the best approach that nurs- es can adopt when addressing quality of life issues with people with MS? Nurses should recognize that each patient may have different expectations and aspirations c. It is important to use quality of life questionnaires before ini- tiating conversations about quality of life 31. The degree of disability is the sole determinant of quality of life in MS b. Recognizing the need to respond to change is more important than the ability to socialize in MS c. Developing and sustaining satisfying relationships is an important factor in MS CHAPTER 22: CERTIFICATION STUDY QUESTIONS 119 32. In general terms, which of the following would be least likely to influence a person’s quality of life in MS? Which of the following statements describes the process termed “molecular mimicry? The foreign target and the self-target of the immune system share molecular features d.
They are numerous enough so that every cell it is dense (approximately 13 times more dense than wa- in the body is close enough to a capillary to receive the nu- ter) buy levitra soft 20 mg with mastercard, and a relatively small column height can be used to trients it needs. The thin capillary walls allow rapid ex- measure physiological pressures. For example, mean arte- changes of oxygen, carbon dioxide, substrates, hormones, rial pressure is equal to the pressure at the bottom of a col- and other molecules and, for this reason, are called ex- umn of mercury approximately 93 mm high (abbreviated change vessels. If the same arterial pressure were measured 212 PART IV BLOOD AND CARDIOVASCULAR PHYSIOLOGY Pressure Height of mercury column FIGURE 12. For the measurement of arterial pressures it is convenient to use mercury instead of water be- cause its density allows the use of a relatively short column. A variety of electronic and mechanical transducers are used to measure blood pressure, but the convention of expressing pres- sure in mm Hg persists. The flow of fluid through rigid tubes is governed by the pressure gradient and resistance to flow. Resistance depends on the radius and length of the tube as well as the viscosity of the fluid. While not exactly descriptive of blood flow through elastic, tapering blood vessels, Poiseuille’s law is useful in under- standing blood flow. The volume of fluid flowing through a rigid tube per unit time (Q) is proportional to the pressure difference ( P) between the ends of the tube and inversely proportional to the resistance to flow (R): FIGURE 12. Because flow is determined by the fourth When fluid flows through a tube, the resistance to flow power of the radius, small changes in radius have a much greater effect than small changes in length. Furthermore, changes in (R) is determined by the properties of both the fluid and the blood vessel length do not occur over short periods of time and tube. Poiseuille found that the following factors determine are not involved in the physiological control of blood flow. The resistance to steady, streamlined flow of fluid through a pressure difference ( P) driving flow is the result of the height of rigid, cylindrical tube: the column of fluid above the openings of tubes A and B. R 8 L/ r4 (2) where r is the radius of the tube, L is its length, and is the though blood viscosity increases with hematocrit and with viscosity of the fluid; 8 and are geometrical constants.
This large chemical exchange without cellular exchange is possible because the fetal and FETAL AND PLACENTAL CIRCULATIONS maternal blood are kept completely separate levitra soft 20mg online, or nearly so. The Placenta Has Maternal and Fetal The fundamental anatomical and physiological structure Circulations That Allow Exchange Between for exchange is the placental villus. As the umbilical arter- ies enter the fetal placenta, they divide into many branches the Mother and Fetus that penetrate the placenta toward the maternal system. The development of a human fetus depends on nutrient, These small arteries divide in a pattern similar to a fir tree, gas, water, and waste exchange in the maternal and fetal the placental villi being the small branches. The human fetal placenta is sup- laries bring in the fetal blood from the umbilical arteries Fetal lung Arteries to upper body High-resistance pulmonary vessels Ductus Pulmonary arteriosus artery Foramen 31 ovale Superior FIGURE 17. Schematic representation of the left and right sides of the fe- tal heart are separated to empha- 52 62 size the right-to-left shunt of blood through the open foramen ovale in Right Left ventricle ventricle 58 the atrial septum and the right-to- Inferior left shunt through the ductus arte- vena cava 67 Abdominal riosus. The numbers 27 Portal represent the percentage of satura- vein tion of blood hemoglobin with oxygen in the fetal circulation. Iliac Closure of the ductus venosus, 26 arteries Liver 80 foramen ovale, ductus arteriosus, 58 Umbilical Umbilical artery and placental vessels at birth and Syncytiotrophoblast vein the dilation of the pulmonary vas- Cytotrophoblast culature establish the adult circula- tion pattern. The insert is a cross- sectional view of a fetal placental villus, one of the branches of the Intervillous tree-like fetal vascular system in space the placenta. The fetal capillaries Fetal provide incoming blood, and the placenta sinusoidal capillaries act as the ve- Maternal nous drainage. The villus is com- placenta pletely surrounded by the maternal blood, and the exchange of nutri- Fetal Syncytial Spiral artery Endometrial vein ents and wastes occurs across the capillary knot fetal syncytiotrophoblast. CHAPTER 17 Special Circulations 287 and then blood leaves through sinusoidal capillaries to the pinocytosis and exocytosis. Exchange occurs in the fetal cap- through the lipid bilayer of cell membranes. For example, illaries and probably to some extent in the sinusoidal capil- lipid-soluble anesthetic agents in the mother’s blood do en- laries.