Explain how acid-base physiology leads to the regulation of fluid balance and extra cellular pH.
Hydrogen ions and bases are present in the blood and changes in the concentration creates acid-base imbalances (McCance & Huether, 2018). The normal pH range for the body is between 7.35 and 7.45. If the pH drops below 7.35, it is considered acidic and above 7.45 is alkalotic. These imbalances can be respiratory or metabolic in cause or a mix of both. When there is a increase in hydrogen ions or a loss of base, an acidic condition is formed. A decrease in hydrogen ions or a increase in base would cause alkalosis. When these conditions arise, the body tries to compensate by altering respiratory or renal functions. This compensation can include hyper and hypo ventilation and the retaining and excretion of bicarbonate by the kidneys. Sodium regulates the water balance of the body and therefore sodium bicarbonate shifts can cause alterations in the fluid balance.
2. How do changes in plasma osmolality affect the physiology of erythrocytes?
Serum osmolality is the concentration of molecules in the blood (McCance & Huether, 2018). Water in the body shifts from areas of low concentration to areas of high concentration. This creates a balance betwenn intracellular and extracellular fluids. Erythrocytes are components of this concentration and are easily impacted by outside mechanisms (Jean-Frédéric Brun et al., 2022). Research has shown that pH and osmolality can cause misshapen erythrocytes. This can lead to trapping of the erythrocytes in the spleen and a decrease in the life-span of the cell. Erythrocytes also contain Aquaporin-1 in their cell membrane, which drives water movement. This allows erythrocytes to act as “micropumps” and are major regulators of water exchange in the body. This assists in maintaining homeostasis.
References
Jean-Frédéric Brun, Varlet-Marie, E., Myzia, J., Eric Raynaud, d. M., & Pretorius, E. (2022). Metabolic Influences Modulating Erythrocyte Deformability and Eryptosis. Metabolites, 12(1), 4. https://doi.org/10.3390/metabo12010004
McCance, K. L., & Huether, S. E. (2018). Pathophysiology (8th ed.). Elsevier Health Sciences.
Select two of the following discussion questions for your discussion response. Indicate which questions you have chosen using the format displayed in the “Discussion Forum Sample.”
Explain how acid-base physiology leads to the regulation of fluid balance and extra cellular pH.
What is the equation for the carbonic acid/bicarbonate buffering system? How do actions at the lungs and kidneys affect this equation and thus compensate for alterations in plasma pH levels?
How do changes in plasma osmolality affect the physiology of erythrocytes?
Explain how acid-base physiology leads to the regulation of fluid balance and extra cellular PH
For the body to maintain homeostasis, it requires the use of many physiological adaptations. One of these adaptations is maintaining acid-base balance within the body. The PH of the human body to maintain homeostasis, ranges between 7.35 to 7.45 (). Body acids are produced as a result of cellular metabolism. The lungs, kidneys and bones are the major regulators of the body’s acid base balance (Hopkins, Sanvictores, Sharma.2022). Body acids can be volatile, with the lungs being the ones to eliminate respiratory acids or CO2 and nonvolatile, with the kidneys being the ones to eliminate the metabolic acids. There are different buffering systems that respond to acid base imbalances in the body. These buffers can absorb excessive H+ or hydroxyl Ion (OH-) to minimize the fluctuations in the body’s PH.
2.What is the equation for the carbonic acid/bicarbonate buffering system? How do actions at the lungs and kidneys affect this equation and thus compensate for alterations in plasma pH levels?
The carbonic acid -bicarbonate buffering system works with the lungs and the kidneys. The higher the carbon dioxide partial pressure (Pco2) the higher the carbonic acid. The equation for this buffering system is as follows: (H2Co3) =0.03 X Pco2(mmHg). The respiratory buffer system regulates the acid base balance by controlling the rate of ventilation where the imbalance is happening. When the environment in the body is acidic, the respiratory rate increases eliminating more Co2. When the environment is alkaline, the respiratory rate decreases retaining mire Co2. In the kidneys, the renal tubules are the one to regulate acid base imbalances by secreting hydrogen in the urine and creating bicarbonate with a urine acidity between 4.4 to 4.7. The tubules combine hydrogen ions, letting more H+ secretion before the PH value is obtained (McCance & Huether.2019).
McCance, K. L., & Huether, S. E. (2019). Pathophysiology: The biologic basis for disease in adults and children (8th ed.). Elsevier. ISBN-13: 978032340281
Hopkins E, Sanvictores T, Sharma S. Physiology, Acid Base Balance. [Updated 2022 Sep 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507807/
Edema results from increased movement of fluid from the intravascular to the interstitial space or decreased movement of water from the interstitium into the capillaries or lymphatic vessels. The mechanism involves one or more of the following:
Increased capillary hydrostatic pressure
Decreased plasma oncotic pressure
Increased capillary permeability
Obstruction of the lymphatic system
As fluid shifts into the interstitial space, intravascular volume is depleted. Each of the types can be further divided into generalized and local forms.
Renal sodium retention happens when the renin-angiotensin-aldosterone-vasopressin (ADH) pathway is activated by intravascular volume reduction. Renal sodium retention causes the kidneys to retain water, which helps to maintain plasma volume by raising osmolality. Fluid overload and edema may both be primarily caused by increased renal salt retention. Consuming too much exogenous salt may also be a factor.
Edema occasionally develops when there is insufficient plasma oncotic pressure, which can happen in conditions like nephrotic syndrome, protein-losing enteropathy, liver failure, or malnutrition.
Infections, toxicity, or inflammatory damage to the capillary walls can cause increased capilliary permeability. Focused edema in angioedema is brought on by mediators, such as bradykinin and complement-derived mediators as well as mast cell-derived mediators (such as histamine, leukotrienes, and prostaglandins).
White blood cells, protein, and some water are expelled from the interstitium through the lymphatic system. These chemicals build up in the interstitium as a result of lymphatic blockage.
Clinically, patients who are “intravascular dry and extravascularly overloaded” are patients who don’t have enough volume in their vascular system because all their fluid is getting pushed into other parts of the body, like the abdomen, lungs, extremities, and dependent areas. These patients will often have pitting edema on exam or “wet sounding” lungs with crackles or decreased breath sounds indicating pleural effusions.
References:
Bouchard, J., Soroko, S. B., Chertow, G. M., Himmelfarb, J., Ikizler, T. A., Paganini, E. P., & Mehta, R. L. (2009). Fluid accumulation, survival and recovery of kidney function in critically ill patients with acute kidney injury. Kidney international, 76(4), 422-427.
McCance, K. L., & Huether, S. E. (2018). Pathophysiology (8th ed.). Elsevier Health Sciences.
