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K. Ramon. University of Puerto Rico, Rio Piedras.

Unfortunately one drug can displace another from such binding and so elevate its free plasma con- centration and create the potential for toxicity order 250mg ilosone free shipping. PHARMACOLOGY AND DRUG EFFECTS 113 There are two sites in the body where a drug is not able to pass freely into the tissue. One is the placenta and the other the brain where the blood±brain barrier (see Chapter 1) is a formidable hindrance. Without pores in the capillaries a drug can only enter the CNS (or cross the placenta) by virtue of lipid solubility, as in the gut. Since a drug is a foreign object, the body does its best to get rid of it. As the organ of excretion, the kidney has a copious blood supply and drugs are easily filtered through the glomerular capillaries into the kidney tubule and urine unless they are very large (e. In fact most drugs would be rapidly lost if they were not so bound or showed sufficient lipid solubility to be reabsorbed through the wall of the kidney tubule back into the bloodstream. Thus a drug which is present in the unionised lipid-soluble form is more readily absorbed from the gut, can enter the CNS and is potentially longer acting as it will avoid excretion, unless it is rapidly metabolised. To increase the chance of removing a drug, the body converts it into a water-soluble, ionised and so excretable form. The metabolite may occasionally be as, or more, active than the parent compound but is generally less so and can sometimes even be toxic. The rate at which a drug is metabolised is generally proportional to its concentration (so-called first-order kinetics) but if there is an excess of drug and the metabolic process becomes saturated, then metabolism proceeds at a constant rate, the maximum possible, irrespective of concentration (zero-order kinetics). With some drugs, such as alcohol, this occurs even at low concentrations. The duration of action of a drug is represented by its half-life ( 1t) which is a measure of the time taken for its plasma 2 concentration to fall by 50%. Obviously drugs with a short half-life have to be taken more frequently. To use a drug properly it is necessary to know not only what con- stitutes an effective plasma concentration but also how long that is maintained following dosage. This information can be obtained from pilot studies in humans but since there is considerable variation in how an individual responds to and metabolises a drug the effect of a drug can vary considerably between subjects.

It is also the place to apply pressure in case mary gland ilosone 250mg amex, which is positioned on the pectoralis major mus- of severe arterial hemorrhage in the forearm or hand. The medial and lateral epicondyles are phatic drainage pathway is toward the axilla (see fig. When the elbow is extended, these promi- nences lie on the same transverse plane; when the elbow is flexed, they form a triangle. The ulnar nerve can be palpated in the ulnar sulcus (groove) posterior to the medial epicondyle (see fig. Surface and Regional © The McGraw−Hill Anatomy, Sixth Edition Anatomy Companies, 2001 320 Unit 4 Support and Movement Deltoid m. The cubital fossa is the depression on the anterior surface Antebrachium of the elbow region, where the median cubital vein links the Contained within the antebrachium (forearm) are two parallel cephalic and basilic veins. These veins are subcutaneous and be- bones (the ulna and radius) and the muscles that control the come more conspicuous when a proximal compression is applied. The muscles of the forearm taper dis- For this reason, they are an important location (particularly the tally over the wrist, where their tendons attach to various bones median cubital) for the removal of venous blood for analyses and of the hand. Several muscles of the forearm can be identified as transfusions or for intravenous therapy (fig. Surface and Regional © The McGraw−Hill Anatomy, Sixth Edition Anatomy Companies, 2001 Chapter 10 Surface and Regional Anatomy 321 Triceps brachii m. The ulna can be palpated along its entire length from Tendon of palmaris longus m. Nerves, tendons, and vessels are close to the surface at the Styloid process of ulna wrist, making cuts to this area potentially dangerous.

After parturition (childbirth) buy ilosone 500mg mastercard, the uterus rapidly shrinks, but it may remain somewhat canal of the uterus. The cervix attaches to the vagina at a nearly enlarged until menopause, at which time there is marked atrophy. The deep recess surrounding the protrusion of the cervix into the vagina is called the fornix (see fig. Uterine Blood Supply and Innervation The fornix is of clinical importance because it permits palpa- The uterus is supplied with blood through the uterine arteries, tion of the cervix during a gynecological examination. Occa- sionally, the deep posterior portion of the fornix provides surgical which arise from the internal iliac arteries, and by the uterine access to the pelvic cavity through the vagina. Each of these paired is important in the placement of two birth control devices—the cervi- vessels anastomose on the upper lateral margin of the uterus. The vaginal wall is composed of three layers: an inner mu- cosal layer, a middle muscularis layer, and an outer fibrous layer. Female Reproductive © The McGraw−Hill Anatomy, Sixth Edition Development System Companies, 2001 Chapter 21 Female Reproductive System 737 FIGURE 21. They also provide friction ridges for stimulation of the penis dur- ing coitus. The additives within semen, however, temporarily neutralize the acidity of the vagina to assist the survival of the spermatozoa deposited within the vagina. The mons pubis is the subcutaneous pad of adipose con- The muscularis layer consists of longitudinal and circular nective tissue covering the symphysis pubis. At puberty, the bands of smooth muscle interlaced with distensible connective mons pubis becomes covered with coarse pubic hair in a some- tissue. The distension of this layer is especially important during what triangular pattern, usually with a horizontal upper border. Skeletal muscle strands near the vaginal orifice, in- The elevated and padded mons pubis cushions the symphysis cluding the levator ani muscle, partially constrict this opening.