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By M. Jensgar. Saint Rose College.
It can also result from the body’s fail- mocytic; normal cells that are of normal ure to absorb iron buy levitra super active 40 mg without prescription, excessive or chronic color are called normochromic buy levitra super active 40 mg with mastercard. Anemias in blood loss, or increases in the body’s iron which the color of the red blood cells is requirements. Anemias in which the red blood caused by the inadequate secretion by the cells are larger than usual are called stomach of a substance (intrinsic factor) macrocytic anemias, and those with cells that is necessary for the intestine to absorb smaller than usual are called microcytic vitamin B12. For The deﬁciency of vitamin B12 impairs pro- example, anemias may result from an duction and maturation of blood cells. Destruction of red blood cells is called Regardless of the cause, anemia disrupts hemolysis. Anemias caused by excessive the transport of oxygen to tissues through- and/or premature destruction of red blood out the body. Common symp- ety of abnormal conditions can cause red toms of anemia are pale skin (pallor), blood cell destruction. Hemolytic anemia weakness, fatigue, difﬁculty in breathing 236 CHAPTER 8 CONDITIONS OF THE BLOOD AND IMMUNE SYSTEM (dyspnea), and fast heart rate (tachy- Polycythemia cardia). Other possible symptoms of anemia include the inability to concen- In polycythemia, there is an increase in trate, irritability, and susceptibility to the number of red blood cells and in the infection. There are several types of poly- If anemia is the result of blood loss, blood cythemia. One type, polycythemia vera, is replacement through transfusion may be associated with an overproduction of necessary. Because of the increased number of cells in the Thalassemia blood, individuals with this condition may experience hypertension, congestive heart The thalassemias are inherited hemolyt- failure, stroke, or heart attack (see Chapter ic anemias common in individuals from 11), or they may experience a hemorrhage the Mediterranean region, Africa, the because the congestion in the blood ves- Middle East, India, and Southeast Asia sels may cause the vessels to rupture. Thalassemias are charac- Secondary polycythemia occurs in con- terized by the production of thin, fragile junction with another disease. When the red blood cells and defective hemoglobin body’s demand for oxygen increases, the synthesis. As a result, the hemoglobin bone marrow produces additional red content of the red blood cells is inade- blood cells to meet the increased demand. In addition, there is often some Chronic obstructive pulmonary disease is interference with erythrocyte metabo- a condition in which secondary poly- lism that causes the red blood cells to be cythemia may occur (see Chapter 12). Symptoms of thalassemia are similar to Although there is no actual increase in the those of other types of anemias. Indi- number of red blood cells, loss of ﬂuid viduals whose symptoms are severe and increases the proportion of red blood cells consequently diagnosed early in life may in the blood. In these cases, treatment require regular transfusions to survive involves ﬂuid replacement to decrease the (Olivieri, 1999). In addition to transfusion therapy, iron Agranulocytosis is the marked reduc- chelation therapy is often necessary to tion in the level of a speciﬁc type of leuko- prevent iron overload (Rodgers, 2000), cyte. This reduction in leukocytes is called and in some instances bone marrow leukopenia. A common cause of agranu- transplantation may be indicated locytosis is toxic reaction to certain medica- (Giardini, 1997). Because the platelet may also result from exposure to certain count is normal in hemophilia, bleeding chemicals or to ionizing radiation. However, the deﬁcien- in ﬁghting infection, a reduction in the cy in clotting factors does pose the dan- number of these cells increases individu- ger of bleeding into the internal organs, als’ susceptibility to infection.
Also generic levitra super active 20mg with amex, the excreted NH4 can substitute in the proximal tubule lumen buy 40 mg levitra super active, an important step in the reabsorp- urine for Na and K , diminishing the loss of these cations. In the proximal tubule, the two ions Several factors influence the renal excretion of H , includ- are directly linked, both being transported by the Na /H ing intracellular pH, arterial blood PCO , carbonic anhy- exchanger in the luminal plasma membrane. Enhanced Na reabsorp- drase activity, Na reabsorption, plasma [K ], and aldos- terone (Fig. The avid renal reabsorption of Na observed in states of volume depletion is accompanied by a factor influencing the secretion and, therefore, the excretion parallel rise in urinary H excretion. An increase in PCO increases the [K ] influence the renal excretion of H. A fall in plasma 2 2 [K ] favors the movement of K from body cells into in- formation of H from H2CO3, leading to enhanced renal terstitial fluid (or blood plasma) and a reciprocal move- H secretion and excretion—a useful compensation for any condition in which the blood contains too much H CO. In the kidney tubule cells, these 2 3 (This will be discussed later, when we consider respiratory movements lower intracellular pH and increase H se- acidosis. K depletion also stimulates ammonia synthesis 2 and, consequently, less complete reabsorption of filtered by the kidneys. The result is the complete reabsorption HCO and a loss of base in the urine (a useful compensa- of filtered HCO3 and the enhanced generation of new 3 tion for respiratory alkalosis, also discussed later). Consequently, hypokalemia (or a decrease in body K stores) leads to increased plasma [HCO3 ] Carbonic Anhydrase Activity. Hyperkalemia (or excess K in the hydrase catalyzes two key reactions in urinary acidification: body) results in the opposite changes: an increase in in- tracellular pH, decreased H secretion, incomplete reab- sorption of filtered HCO3 , and a fall in plasma [HCO3 ] (metabolic acidosis). Aldosterone stimulates the collecting ducts to secrete H by three actions: + 1) It directly stimulates the H -ATPase in collecting Increased H plasma H+-ATPase duct -intercalated cells. This response leads to hy- Na+ reabsorption Decreased pokalemia, which increases renal H secretion. K+ K+ Hyperaldosteronism results in enhanced renal H ex- cretion and an alkaline blood pH; the opposite occurs with H+ - HCO - hypoaldosteronism. The secretion of H by the kidney tubules 2 2 2 3 Increased CA and collecting ducts is gradient-limited. The collecting Carbonic anhydrase PCO2 ducts cannot lower the urine pH below 4. If more buffer base (NH3, 2– HPO4 ) is available in the urine, more H can be secreted Factors leading to increased H secretion before the limiting gradient is reached. As a consequence, the plasma [HCO ] 3 3 ders characterized by chronic metabolic acidosis, a normal falls and chronic metabolic acidosis ensues. The steady state, the tubules are able to reabsorb the filtered kidneys show inadequate H secretion by the distal HCO load more completely because the filtered load is 3 nephron, excessive excretion of HCO , or reduced excre- reduced. In type 2 RTA, the ad- 4 3 In classic type 1 (distal) RTA, the ability of the col- ministration of an NH4Cl challenge results in a urine pH be- lecting ducts to lower urine pH is impaired. This disorder may be inherited, may be associated can be caused by inadequate secretion of H (defective with several acquired conditions that result in a general- H -ATPase or H /K -ATPase) or abnormal leakiness of ized disorder of proximal tubule transport, or may result the collecting duct epithelium so that secreted H ions from the inhibition of proximal tubule carbonic anhydrase diffuse back from lumen to blood. Treatment requires the inappropriately high, titratable acid excretion is dimin- daily administration of large amounts of alkali because ished and trapping of ammonia in the urine (as NH ) is when the plasma [HCO ] is raised, excessive urinary ex- 4 3 decreased. Type 1 RTA may be the result of an inherited cretion of filtered HCO occurs. A diagnosis of this form of RTA is es- both K and H is reduced, explaining the hyperkalemia tablished by challenging the subject with a standard oral and metabolic acidosis. Hyperkalemia reduces renal am- dose of NH4Cl and measuring the urine pH for the next monia synthesis, resulting in reduced net acid excretion several hours. The underlying dis- RTA involves daily administration of modest amounts of order is a result of inadequate production of aldosterone or alkali (HCO , citrate) sufficient to cover daily metabolic impaired aldosterone action. Metabolism If H ions were passively distributed across plasma + H membranes, intracellular pH would be lower than what is - + seen in most body cells.