Prandin

By F. Dudley. Wisconsin Lutheran College.

Histology © The McGraw−Hill Anatomy purchase prandin 2mg overnight delivery, Sixth Edition of the Body Companies, 2001 Chapter 4 Histology 87 Secretion Lumen Mucus Liver Cell membrane Stomach Gallbladder Golgi complex Large intestine Small intestine Nucleus of goblet cell Rough endoplasmic reticulum Creek (a) (b) (c) FIGURE 4. Multicellular glands, as their name implies, are composed of both secretory cells and cells that form the walls of the As tissues develop in the embryo, tiny invaginations (infoldings) ducts. Multicellular glands are classified as simple or com- or evaginations (outfoldings) of membranous epithelia give rise to pound glands. The ducts of the simple glands do not specialized secretory structures called exocrine (ek′so˘-krin) glands. These glands remain connected to the epithelium by ducts, and Multicellular glands are also classified according to the their secretions pass through the ducts onto body surfaces or into shape of their secretory portion. Exocrine glands should not be confused with en- tubular glands if the secretory portion resembles a tube and docrine glands, which are ductless, and which secrete their prod- as acinar glands if the secretory portion resembles a flask. Multicellular glands with a secretory portion that resem- Exocrine glands within the skin include oil (sebaceous) glands, bles both a tube and a flask are termed tubuloacinar glands. Exocrine glands within the digestive system include the salivary and pancreatic glands. Multicellular glands are also classified according to the Exocrine glands are classified according to their structure means by which they release their product (fig. Merocrine (mer′o˘-krin) glands are those that secrete a wa- structure, there are two types of exocrine glands, unicellular and tery substance through the cell membrane of the secretory multicellular glands. Unicellular glands are single-celled glands, such as goblet glands are of this type. Apocrine (ap′o˘-krin) glands are those in which the secre- occur within most epithelial tissues. Goblet cells are found tion accumulates on the surface of the secretory cell; then, in the epithelial linings of the respiratory and digestive sys- a portion of the cell, along with the secretion, is pinched tems. The mucus secretion of these cells lubricates and pro- off to be discharged. Histology © The McGraw−Hill Anatomy, Sixth Edition of the Body Companies, 2001 88 Unit 3 Microscopic Structure of the Body Duct Secretory cells Simple tubular Simple Simple Simple acinar Simple branched tubular coiled tubular branched acinar Compound tubular Compound acinar Compound tubuloacinar FIGURE 4. The ducts of the simple glands either do not branch or have few branches, whereas those of the compound glands have multiple branches.

When the wave of depolarization associated with a nerve action potential spreads into the terminal of a motor axon order 0,5 mg prandin amex, Impulse Transmission From Nerve to Muscle several processes are set in motion. The lowered membrane Occurs at the Neuromuscular Junction potential causes membrane channels to open and external calcium ions enter the axon. The rapid rise in intracellular The contraction of skeletal muscle occurs in response to ac- calcium causes the cytoplasmic vesicles of ACh to migrate tion potentials that travel down somatic motor axons orig- to the inner surface of the axon membrane, where they fuse inating in the CNS. The transfer of the signal from nerve to with the membrane and release their contents. Because all muscle takes place at the neuromuscular junction, also the vesicles are of roughly the same size, they all release called the myoneural junction or motor endplate. When the ACh molecules arrive at the postsynaptic The Structure of the Neuromuscular Junction. On membrane after diffusing across the synaptic cleft, they reaching a muscle cell, the axon of a motor neuron typically bind to the ACh receptors. When two ACh molecules are branches into several terminals, which constitute the presy- bound to a receptor, it undergoes a configurational change naptic portion of the neuromuscular junction. The termi- that allows the relatively free passage of sodium and potas- nals lie in grooves or “gullies” in the surface of the muscle sium ions down their respective electrochemical gradients. Soon ACh diffuses away and is hydrolyzed by AChE into choline and acetate, terminating its function as a trans- mitter molecule, and the membrane permeability returns to Axon terminal Schwann cell the resting state. The choline portion is taken up by the presynaptic terminal for resynthesis of ACh, and the ace- Synaptic vesicles tate diffuses away into the extracellular fluid. These events take place over a few milliseconds and may be repeated many times per second without danger of fatigue. Synaptic cleft Schwann cell process Electrical Events at the Neuromuscular Junction.

From the reaction H HCO3 H2CO3 H2O CO2 order prandin 0,5 mg on-line, we [HCO3 ] predict that the [HCO3 ] will fall by 10 mmol, and that 10 6. If the system were closed and no CO2 could escape, the new pH would be We can also use 0. This form of the Henderson-Hasselbalch equation is Fortunately, however, the system is open and CO2 can escape via the lungs. If all of the extra CO2 is expired and useful in understanding acid-base problems. Therefore, this equation is [24 10] valid only if CO2(d) and H2CO3 are in equilibrium with pH 6. The following expression results if we take antiloga- Although this pH is low, it is compatible with life. In the body, an acidic blood pH stimulates breathing, which [H ] 24 PCO2/[HCO3 ] (16) can make the PCO2 lower than 40 mm Hg. If PCO [24 10] is 40 mm Hg and plasma [HCO3 ] is 24 mmol/L, [H ] is pH 6. As previously noted, the pK can be added to the plasma to correct the plasma of the HCO3 /CO2 system (6. Once the pH of the blood is normal, the stimu- mal pH of arterial blood. On the contrary, it is remarkably effective because it operates in an open system; that is, the two buffer components can be added to or removed from Changes in Acid Production May the body at controlled rates. Help Protect Blood pH The HCO3 /CO2 system is open in several ways: 1) Metabolism provides an endless source of CO2, Another way in which blood pH may be protected is by which can replace any H2CO3 consumed by a base added changes in endogenous acid production (Fig. A decrease in blood pH results in decreased produc- the ECF by forming new HCO3 when excess acid has tion of lactic acid and ketone body acids, which opposes been added to the body or excreting HCO3 when excess the acidic shift in pH.

Psychological factors such as Return to work for individuals with depression or decreased self-esteem can brain damage involves many factors cheap prandin 0,5mg on line. The anxiety or emo- cause of the wide variations in disability tional reactions of the individual’s sexual related to brain damage, no one model can partner may also adversely affect sexual be applied to all individuals. The degree to which individuals ity may be social isolation and limited with brain damage are able to maintain social contacts. Individuals with brain employment depends on the extent of the damage may have lost friends and con- damage and associated functional limita- tacts, or they may not have had a sexual tions as well as on their prior background, partner at the time of the injury. When age at the time brain damage occurred, opportunities to increase social interaction preinjury education, occupation, and do occur, they may, in their desire to be work history (Keyser-Marcus et al. Individuals with brain dam- motivation and support from family are age who do not have a sexual partner may also important factors in determining the need to learn acceptable outlets through individual’s rehabilitation potential. Factors that seem most related to the Some individuals with brain damage ability to return to work and to maintain may experience disinhibition, impairment employment after brain damage are the in judgment, or inability to control sexu- severity of the damage, age, and work his- al impulses. In these instances, they may tory prior to brain damage (Felmingham, engage in socially inappropriate behaviors, Baguley, & Crooks, 2001; Wagner, Hammond, such as inappropriate sexual advances or Sasser, Wiercisiewski, & Norton, 2000). Persons interpret social and environmental cues with greater disability have been shown to and in learning more socially appropriate require more extended time and more ways of expressing sexual need. Although the major- some instances the individual with brain ity of individuals with mild brain damage damage may be unaware that a problem may be able to return to work, individu- exists. Talking openly about sexuality and als with moderate and severe brain dam- 54 CHAPTER 2 CONDITIONS OF THE NERVOUS SYSTEM: PART I age have poorer outcomes (Fabiano & them find alternative ways to perform Daugherty, 1998). Even when job place- tasks and to develop strategies to reduce, ment is accomplished, for individuals with organize, and retrieve information can moderate to severe disability, job retention reduce the disabling effects of memory im- may be difficult. Since individuals may have dif- they were in before the injury also appears ficulty organizing their day, implementing to influence return to work outcome, with structured routines, using written notes or the highest rate of return to work being lists, or using audiotaped reminders may among persons with higher decision- help improve performance. Usually notes making jobs (Orr, Walker, Marwitz, & or lists will be most effective if informa- Kreutzer, 2003). Age also appears to be a tion is kept simple with no extraneous significant determinant of return to work.