The Kidney's Role in Homeostasis

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The Kidney's Role in Homeostasis by Mind Map: The Kidney's Role in Homeostasis

1. Erythropoietin Production

1.1. Erythropoietin- producing cells of the kidney identified as peritubular cells (cortical fibroblasts)

1.1.1. Erythropoietin production stimulated by hypoxia and inhibited when hypoxia is corrected – production controlled by negative feedback principle

1.2. Erythropoietin Hormone is glycoprotein that promotes proliferation and differentiation of erythrocytes precursors in the bone marrow

1.2.1. Erythropoietin: maintenance of a normal red blood cell count and prevention of anemia

2. Regulates Blood Pressure

2.1. The kidneys are to some extent able to auto regulate the pressure of the blood entering the glomerular capillaries

2.2. Kidneys are the source of hormone renin which has a direct effect on blood pressure via renin-angiotensin pathway

2.2.1. Renin-Angiotensin Pathway Dehydration, Na+ Deficiency or hemorrhage --> decrease in blood volume and pressure --> Kidney Release Renin --> Angiotensin I release Angiotensin Converting Enzyme --> Angiotensin II --> Aldosterone released by Adrenal Cortex --> In the Kidneys more Na+ and water return to blood and more K+ eliminated in urine --> Increased in blood volume and blood pressure

2.3. Hypertension Related to Chronic Kidney Disease

2.3.1. Patient Assessment #1 Objective Assessment Weight Gain Vital Signs: Blood pressure systolic is > 130 mmHg and/or diastolic > 80mmHgntly Frequency of urination decreased Peripheral Edema Lab Tests: GFR - a.45-59 or b.30-44 ml/min/1.73 m2 Subjective Assessment Nursing Diagnosis #1 Excess fluid volume related to decrease in glomerular filtration rate Nursing Intervention #1

2.3.2. Patient Assessment #2 Objective Assessment Increase in plasma sodium concentration Oliguria Peripheral Edema weight gain Elevated blood pressure Subjective Assessment complains of lethargy complains of weakness Nursing Diagnosis #2 Nursing Intervention #2 Excess fluid retention related to sodium retention

2.3.3. Patient Assessment #3 Nursing Diagnosis #3 Nursing Intervention #3 ineffective tissue perfusion related to vasoconstriction of blood vessels manifested by high blood pressure Objective Assessment Subjective Assessment Decrease Urine output Constant elevated blood pressure Cold and clammy skin

2.3.4. Patient Assessment #4 Nursing Diagnosis #4 Nursing Intervention #4 Fatigue and light-headedness secondary to very high blood pressure, low hemoglobin Subjective Assessment Fatigue light-headedness Objective Assessment Low hemoglobin

3. Regulation of Body fluid volume and osmolality

3.1. Sodium levels hence fluid volume are regulated by 3 hormones:

3.1.1. 1. Antidiuretic Hormone (ADH): Release and control plasma osmolality - Sodium and chloride contributes to 95% of the extracellular fluid osmolality 1. Sensors: osmoreceptors in hypothalamus detect a rise in plasma osmolality 2. ADH – secreted from posterior pituitary gland into circulation 3. Effector: ADH binds to receptors on the surface of the collecting duct cells in the nephron 4.Response: bound ADH causes water channels to open in the collecting ducts and water is reabsorbed into the blood, diluting the plasma and reducing the osmolality to normal 5.Stimulation of the osmoreceptors is reduced (negative feedback) 2. Aldosterone – steroid hormone secreted from adrenal cortex . Effects on distal tubule of the nephron: the more aldosterone is secreted the more sodium is reabsorbed. Aldosterone is regulated by angiotensin II peptide. 3. Atrial Natriuretic Peptide - Peptide released from cardiac atrial cells in response to increased atrial stretch. 5 major effects are inhibition of aldosterone, reduction of renin release, reduction of ADH release, vasodilation and natriuresis and diuresis.

4. Minerals (Regulation of Calcium, Phosphate and Magnesium

4.1. Calcium: 2 forms: 50% exists in the free ionised form (1.25mmol/L) and 50% in a bound form (in protein) particularly albumin (1.25mmol/L)

4.2. Phosphate: 2 forms acid phosphate and alkaline phosphate - normal plasma range 0.87-1.45 mmol/L. Phosphate important in buffer systems to maintain the plasma pH and exists in equilibrium with calcium

4.3. Magnesium: An intracellular cation and involved in energy storage and production and magnesium balance linked to calcium.55% of body magnesium is found in bones

5. Acid –Base Control

5.1. Maintaining the constancy of the pH of the body's fluids (normal pH: 7.35-7.45)

5.1.1. To maintain a constant hydrogen ion concentration (and hence constant pH), both acids and bases need to be present in the solution to donate or accept free hydrogen ions as required. Acid and bases working together in this way to minimize changes in pH are called buffers. Most important physiologically is the bicarbonate buffering system. CO2 + H2O <--> H2CO3 <--> H+ + HCO3-

5.2. When plasma bicarbonate concentration is normal(25mmol) then all of the filtered bicarbonate is reabsorbed in the proximal tubule (90%) and distal tubule (10%).

6. Waste (Urea, Creatinine ad uric acid)

6.1. Primary excretory organ – responsible for getting rid of waste through formation and excretion of urine

6.2. Excretion of metabolic waste +urea(generated from protein) + Creatinine(generated from muscle)+ uric acid(by product of purines) + bilirubin (from hemoglobin) + metabolites(from hormones)

6.3. drug metabolites: excreted from the body through the kidneys

7. Electrolytes

7.1. Filtration

7.1.1. Glomerular filtration is the process of filtration of plasma across the glomerular basement membrane from the glomerulus into the Bowmans Capsule.

7.2. Reabsorption

7.2.1. Proximal Tubule - 65% of reabsorption - active transport mechanism absorption: sodium (60-70%), chloride, potassium (60-70%),, glucose (100%), amino acids (100%), phosphate, and bicarbonate - passive diffusion absorption: urea (50%) - water absorbed by osmosis (50%) Distal Convoluted Tubule - Hormones that form negative feedback system – communication between cells, distal tubule and rest of the body for homeostatic control of ions and water -Sodium and water reabsorption: Aldosterone and ADH - PTH – Calcium and Phosphate

7.3. Secretion

7.3.1. Secretion occurs in proximal and distal tubules: involves movement of substances from blood flowing through the peritubular capillaries through tubule wall cells into tubular fluid. Substances that are secreted into the tubules are excreted in the urine Creatinine secretion – filtered by glomerulus – total creatinine excretion is increased by 20% by the process of secretion Hydrogen Ions that are transported into the tubules by secretion (proximal and distal) and Potassium secreted (distal tubule) in exchange for sodium reabsorption (by aldosterone)