1. REMOVAL OF METABOLIC WASTE BY KIDNEY
1.1. The kidneys go through series of process to get rid of waste and maintain equilibrium in the body: filtration, reabsorption, secretion and excretion are the main process the kidneys engages by the help of functional units called nephrons, which are found in the kidneys.
1.1.1. Blood is filtered into the tubules of the nephrons through the glomerulus on their journey the there is reabsorption of the needed ions and solute back into the blood stream then the unwanted waste in the form of nitrogenous substances like urea, ammonia, CO2, creatinine and other salts are excreted as wastes. The kidney normally makes about 1-2litres of urine a day. According to the body needs substances are secreted from the blood vessels through the interstitial fluid into the tubules.
1.1.2. Causes: High levels of waste may be toxic to the body, this happens in renal failure and Patient may need dialysis. Signs and symptoms: Increased levels of serum urea, weakness, confusion, nausea, vomiting, low appetite, High blood pressure
2. BLOOD PRESSURE CONTROL
2.1. The kidney response to Low Blood Pressure by releasing an enzyme called RENIN which converts the Angiotensinogen>angiotensin I in the liver and an Angiotensin Converting Enzyme (ACE) metabolizes angiotensin II: (RAAS). This constricts the efferent arterioles causing an increase in capillary blood pressure due to the narrowing of the arterioles, hence there’s an increased infiltration rate in the glomerulus (GFR). The thirst centers in the brain are also stimulated to encourage water intake
2.1.1. Angiotensin II also releases the hormone Aldosterone from the Adrenal Cortex: This is a salt-retaining Hormone which retains sodium and water but excretes potassium, this happens in both the Proximal convoluting tubules and the Distal Convoluting Tubule. Both Angiotensin II and Aldosterone together work to increase blood volume in cases of low blood pressure. They restore electrolyte balance.
2.1.2. High Blood Pressure: there is a negative feed-back signal in the glomerulus which halts the Renin production
3. ACID/BASE BALANCE
3.1. The kidney regulates the body’s acid /base balance by causing the proximal Convoluting tubules to reabsorb bicarbonate (HCO3) and excreting hydrogen ions (H+). The amount of reabsorbed bicarbonate is regulated in response to changes in blood pH the collecting duct also secretes new bicarbonate into the blood during high acid loads
3.1.1. Causes of decreased pH: Diabetic keto acidosis, renal failure, use of drugs, starvation Signs and symptoms: Headache and confusion, feeling lethargic, fatigue
3.1.2. Causes of increased pH: Heavy loss of acid load, increased serum bicarbonate, hypokalemia, hypercalcemia Signs and symptoms: Vomiting, dizziness, dysrhythmia, numbness and tingling of fingers and toes
4. ERYTHROPOIETIN PRODUCTION
4.1. Erythropoietin (EPO) is a hormone released in the renal cortex and red bone marrow. It stimulates the production of Red Blood Cell (RBC). Normal low levels of EPO are continually secreted to compensate for normal blood cell turnover. Also when there is blood loss, e.g injury anemia GI losses resulting in oxygen deficiency, the kidney responds by increasing the release of EPO production.
5. GLUCOSE MAINTENANCE
5.1. The kidney and Live rare also involved in the production of glucose (Gluconeogenesis) and its uptake and utilization.
6. ELECTROLYTES BALANCE
6.1. Sodium: In hyponatremia, there is the reabsorption of sodium ions and the tubules excrete potassium. The process triggers the release of Anti-diuretic Hormone (ADH) which causes water retention thereby balancing the sodium and water content to restore plasma volume.
6.1.1. Causes of Hyponatremia: Kidney disease, adrenal insufficiency, GI losses (Diarrhea) ADH abnormality and muscle wasting Signs and Symptoms: Dizzines, abdominal cramps nausea and vomiting diarrhea.
6.1.2. Cause of Hypernatremia: Excess Aldosterone secretion, diabetes insipidus, Dehydration and intake of large amount of salt. Signs and Symptoms: Thirst, Flushed skin, dry skin, dry sticky mouth, fever, agitation and convulsion.
6.2. Potassium: Reabsorbed and actively secreted in the DCT and the collecting duct. The hormone Aldosterone controls the potassium levels in the body. High levels of K+ triggers the cells of DCT and the collecting duct to activate the Na+/K+ pump. Na+ ions exit the cells and K+ ions enter the cell resulting in the excretion of K+
6.2.1. Causes of Hypokalemia: Diarrhea, vomiting, GI losses (bleeding), alkalosis, polyuria, The use of potassium wasting diuretic Signs and symptoms: Excessive sweating, intestinal disstention, irregular pulse, fatigue, weakness, decrease muscle tone
6.3. Calcium: In cases of low serum calcium levels the kidney is stimulated by the Parathyroid Hormone (PTH) to produce the hormone calcitriol (Calcitonin) which helps in the absorption of dietary calcium from the small intestine and increase calcium reabsorption by the tubules.
7. FLIUD VOLUME BALANCE
7.1. The kidney controls blood volume and blood pressure, by removing more or less water as needed. Water excretion by the kidneys is regulated by a number of hormones. Vasopressin (ADH) secreted by the hypothalamus. This is released when there is a low blood volume and high plasma osmolarity. This hormone causes the kidney to retain more water by increasing the water permeability of the collecting duct.
7.1.1. Causes of low volume: The use of loop diuretics, overproduction of ADH, Diabetes insipidus, dehydration Signs and symptoms: Diarrhea, nausea, vomiting
7.1.2. Causes of high volume: Chronic heart failure (CHF), interstitial fluid overload, the use of thiazides (metolazone) Signs and symptoms: Shortness of breath, edema to extremities, fatigue