Urinary and Electrolyte Systems Key Concepts

Kidney Role

• maintain homeostasis by filtering blood to remove metabolic wastes and regulating blood volume, pressure, and composition

• produce hormones such as calcitriol and erythropoietin

• excrete wastes such as urea and creatinine

Three Basic Nephron Tasks

1. Glomerular filtration: water and most solutes in blood plasma move across the wall of glomerular capillaries where they are filtered and move into the glomerular capsule and then into the renal tube; takes place in glomerulus

2. Tubular reabsorption: water and solutes return to the blood as it flows through the peritubular capillaries and vasa recta

3. Tubular secretion: as filtered fluid flows through the renal tubules and collecting ducts they secrete other materials into the fluid; removes a substance from the blood

ADH Overview

• antidiuretic hormone

• increases water reabsorption in the collecting ducts by inserting aquaporins resulting in concentrated urine

Systems that Contribute to Waste Management

• respiratory: removal of CO2

• integumentary: heat, water, salts in sweat

• digestive: feces/solid waste

Development Overview

• kidneys develop from the intermediate mesoderm through three stages: pronephros, mesonephros, and metanephros.

Pronephros

• stage 1

• first pair of kidneys develop

• located mostly superiorly

• associated with the pronephric duct which empties into the cloaca

• cloaca serves as a common outlet for the urinary, digestive, and reproductive systems

• begins to degenerate during fourth week and is gone by sixth week

Mesonephros

• second stage

• connected to the mesonephric duct which develops from the retained portion of the pronephric duct

• is gone by eighth week

Metanephros

• third stage

• develops about the fifth week

• becomes the functional kidneys of the newborn

• form from the ureteric bud and the metanephric mesoderm

Aging of the Kidneys

• kidneys shrink

• blood flow and GFR decreases

• the ability to concentrate urine declines

Body Fluid

• consists of water and dissolved solutes

• divided into intracellular and extracellular compartments

• essential for chemical reactions and transporting nutrients and wastes

Water Balance

• water is gained through ingestion and metabolic synthesis

• lost through the kidneys (urine), skin (sweat), lungs (exhalation), and GI tract

• this centre in hypothalamus and hormones like ADH, aldosterone, and ANP regulate these levels

Acid-Base Balance

• maintained by buffer systems

• exhalation of CO2 and renal excretion of H+

• failure of this leads to either acidosis (CNS depression/coma) or alkalosis (overexcitability/spasms)

Sodium Deficiency - Cause and Symptoms

• hyponatremia

• due to decreased sodium intake

• increased sodium loss from vomiting, diarrhea, aldosterone deficieny, or taking certain diuretics

• symptoms: muscular weakness, dizziness, headaches, hypotension

Excess Sodium - Cause and Symptoms

• hypernatremia

• occur with dehydration, water deprivation, or excess sodium in diet or intravenous fluids

• causes hypertonicity of ECF which pulls water out of body cells and into ECF

• symptoms: intense thirst, hypertension, edema, agitation and convulsions

Chloride Deficiency - Causes and Symptoms

• hypochloremia

• due to excessive vomiting, overhydration, aldosterone deficiency, congestive heart failure and certain diruetics

• symptoms: muscle spasms, metabolic alkalosis, shallow respirations, hypotension

Excessive Chloride - Causes and Symptoms

• hyperchloremia

• occur from dehydration due to water loss, severe renal failure, certain types of acidosis and some drugs

• symptoms: lethargy, weakness, metabolic acidosis and rapid deep breathing

Potassium Deficiency - Causes and Symptoms

• hypokalemia

• result from excessive loss due to vomiting, decreased potassium intake, hyperaldosteronism, kidney disease, and some diuretics

• symptoms: muscle fatigue, flaccid paralysis, mental confusion, increased urine output, shallow respirations, and changes in elecocardiogram

Excess Potassium - Causes and Symptoms

• hyperkalemia

• due to excessive potassium intake, renal failure, aldosterone deficiency, crush injuries or transfusion of hemolyzed blood

• symptoms: irritability, nausea, muscular weakness, can cause death by inducing ventricular fibrillation

Calcium Deficiency - Causes and Symptoms

• hypocalcemia

• due to increased calcium loss, reduced calcium intake, elevated phosphate levels

• symptoms: numbness/tingling in fingers, hyperactive reflexes, muscle cramps, convulsions, bone fractures, spasms of laryngeal muscles that can cause death by asphyxiation

Excess Calcium - Causes and Symptoms

• hypercalcemia

• caused by hyperparathyroidism, prolonged immobilization, vitamin D overdose, or certain cancers

• symptoms: nausea, vomiting, constipation, confusion, increased thirst and urination, and can lead to kidney stones and cardiac issues.

Phosphate Deficiency - Causes and Symptoms

• hypophosphatemia

• caused by inadequate dietary intake, malabsorption, excessive excretion, or hyperparathyroidism

• symptoms: muscle weakness, bone pain, respiratory failure, impaired immune function, and can lead to rickets or osteomalacia.

Excess Phosphate - Causes and Symptoms

• hyperphosphatemia

• caused by impaired renal function, excessive dietary intake, or cellular breakdown

• symptoms: itchy skin, muscle cramps, joint pain, and can lead to calcification of soft tissues.

Magnesium Deficiency - Causes and Symptoms

• hypomagnesemia

• caused by inadequate dietary intake, gastrointestinal loss, renal loss, or certain medications

• symptoms: muscle cramps, fatigue, nausea, seizures, and can lead to arrhythmias or osteoporosis.

Excess Magnesium - Causes and Symptoms

• hypermagnesemia

• caused by renal failure, excessive dietary intake, or supplementation

• symptoms: nausea, vomiting, weakness, respiratory depression, and can lead to cardiac arrest.