The Urinary System PDF

# The Urinary System ## The Urinary System - The kidneys are the major excretory organs of the body. - They remove waste products from the blood - Many waste products are toxic, but most are metabolic by-products of cells and substances absorbed from the intestine. - The skin, liver, lungs, and...

# The Urinary System ## The Urinary System - The kidneys are the major excretory organs of the body. - They remove waste products from the blood - Many waste products are toxic, but most are metabolic by-products of cells and substances absorbed from the intestine. - The skin, liver, lungs, and intestines can eliminate some of these waste products. - The body cannot compensate if the kidneys fail to function. ## Different Urine Color | Color | Description | |---|---| | Clear | Pale Amber | | Pink | Red | | Amber | Blue | | Orange | Green | | Dark Orange | Cloudy | | Urine | White | | Milky | - | ## Major Functions of the Urinary System - Regulation of blood volume and pressure - Kidneys control extracellular fluid volume in the body. - They can produce a large volume of dilute urine or a small volume of concentrated urine. - Kidneys regulate blood volume and blood pressure. - Regulation of the concentration of solutes in the blood - Kidneys help to regulate the major molecules and ions like glucose, Na+, Cl-, K+, Ca2+, HCO3-, and HPO42–. ## Kidneys: Regulation, Synthesis and Excretion - Regulation of Extracellular Fluid pH Value - Kidneys excrete variable amounts of H+ to help regulate extracellular fluid pH. - Regulation of Red Blood Cell Synthesis - Kidneys secrete a hormone, erythropoietin, that regulates the synthesis of red blood cells in bone marrow. - Regulation of Vitamin D Synthesis - Kidneys play an important role in controlling blood levels of Ca2+ by regulating the synthesis of Vitamin D. ## Functions & WET BED - Functions - Filters blood - Absorbs water - Removes wastes (Creatinine & Urea) - Control Acid-Base Balance - Produces: - Renin (controls BP) - Calcitriol (form of Vitamin D) - Erythropoietin (hormone for RBC production) - *Adrenal Gland* - Cortisol (Steroid Hormone/Stress Hormone) - Reduction of inflammation - Regulating BP - Increase BGL - Remember: A WET BED - Acid-base balance - Water balance - Electrolyte balance - Toxin Removal - Blood pressure control - Erythropoietin - Vitamin D metabolism ## Anatomy of the Kidneys - **External Anatomy** - Kidney - *bean-shaped organ* - Hilum - indented area on medial side - Renal artery - brings blood in - Renal vein - takes blood away - Ureter - tube carrying urine away - **Internal Anatomy** - **Renal Cortex** - Outer region - Contains most nephrons - **Renal Medulla** - Inner region - Contains renal pyramids - **Renal Pelvis** - Funnel-shaped space - Collects urine from renal pyramids - Empties into ureter ## The Nephron - **Functional unit of the kidney** - **Responsible for filtering blood and producing urine** - **Parts of a nephron** - Glomerular capsule (Bowman's capsule) - Surround the glomerulus - Collects filtrate - Glomerulus - Ball of capillaries - Site of filtration - Proximal convoluted tubule - First segment of renal tubule - Site of reabsorption - Loop of Henle - Descending limb - Permeable to water - Ascending limb - Impermeable to water - Distal convoluted tubule - Second segment of renal tubule - Site of reabsorption and secretion - Collecting duct - Carries urine to the renal pelvis ## Urine Production - The primary function of the kidney is regulation of body fluid composition. - The kidney is the organ that sorts the substances from the blood for either removal in the urine or return to the blood. - Substances that are waste products, toxins, and excess materials are permanently removed from the body. - Other substances need to be conserved to maintain homeostasis. ## Filtration - Occurs when blood pressure nonselectively forces water and other small molecules out of glomerular capillaries and into the Bowman capsule. - This creates a fluid called filtrate. - An average of 21% of the blood pumped by the heart flows through the kidneys to the glomerular capillaries. - About 19% passes through the filtration membrane to become filtrate. - The nephrons of the kidneys produce 180 liters of filtrate each day. - Less than 1% of the filtrate becomes urine because most of the filtrate is reabsorbed. ## Tubular Reabsorbtion - Takes place from the renal tubules into the peritubular capillaries. - In 24 hours, the kidneys create 150-180 liters of filtrate, but the normal urinary output is 1-2 liters. - Most of the renal filtrate is reabsorbed back into the blood in the peritubular capillaries. - Only 1% of the filtrate becomes urine. ## Urine Formation - **Glomerular Filtration**: - Blood flow kidneys: 120mL/min - Filtration of H2O, Electrolytes and minute molecules in the glomerulus - Large molecules like proteins remain in the bloodstream. - **Tubular Reabsorption**: - Filtered H2O > Renal Tubules > Renal Capillaries > H2O - Reabsorption > Venous Circulation - **Tubular Secretion**: - Filtered fluid > renal capillaries > waste exit Renal Tubules > Excretion - **Urine Excretion**: - At least 30mL/hr ## Regulation of Urine Concentration and Volume - Urine production helps maintain blood volume and therefore blood pressure. - Increased blood volume can increase blood pressure, and a decrease in blood volume can decrease blood pressure. - If blood volume increases above normal, the kidneys produce a large volume of urine. - The loss of water in the urine lowers blood volume. - If blood volume decreases below normal, the kidneys produce a small volume of urine to conserve water and maintain blood volume. ## Hormonal Mechanism - 3 Major Hormonal Mechanism - Renin-Angiotensin-aldosterone System (RAAS) - Antidiuretic Hormone - Atrial Natriuretic Hormone - **Renin-Angiotensin-Aldosterone Mechanism**: - Aldosterone increases the rate of active transport of Na+ in the distal convoluted tubules and collecting ducts. - Without aldosterone, a large amount of Na+ remains in the nephron. - This causes water to increase the concentration in the filtrate and increases urine volume. - Urine volume increases and urine contains a high concentration of Na+. - **Antidiuretic Hormone**: - Secreted by the posterior pituitary gland. - Travels through the circulatory system. - Regulates the amount of water reabsorbed by the distal convoluted tubules and collecting ducts. - **Atrial Natriuretic Hormone**: - Secreted by the cardiac muscle cells in the right atrium of the heart. - Released when blood pressure in the right atrium increases above normal. - Acts on the kidneys to decrease Na+ reabsorption. - Na+ and water remain in the nephron to become urine. - Increased loss of Na+ and water reduces blood volume and blood pressure ## Urine Movement - **Anatomy and Histology of the Ureters, Urinary Bladder, and Urethra**: - Ureters: Tubes that transport urine from the kidneys to the bladder. - Urinary Bladder: Stores urine before it is released from the body. - Urethra: Tube that carries urine from the bladder out of the body. - **Micturition Reflex**: - The micturition reflex is activated by stretch of the urinary bladder wall. - As the urinary bladder fills with urine, pressure increases, stimulating stretch receptors in the wall of the urinary bladder. ## Micturition Reflex - Urine in the urinary bladder stretches the urinary bladder wall. - Stretch receptors are carried along pelvic nerves (green line) to the sacral region of the spinal cord. - Action potentials are carried by parasympathetic nerves (red line) to contract the smooth muscles of the urinary bladder. - Decreased action potentials carried by somatic motor nerves (purple line) cause the external urinary sphincter to relax ## Control of the Micturition Reflex by Higher Brain Centers - Ascending pathways carry an increased frequency of action potentials up the spinal cord to the pons and cerebrum when the urinary bladder becomes stretched. This increases the conscious urge to urinate. - Descending pathways carry action potentials to the sacral region of the spinal cord to tonically inhibit the micturition reflex, preventing automatic urination when the urinary bladder is full. - Descending pathways carry action potentials from the cerebrum to the sacral region of the spinal cord to facilitate the reflex when stretch of the urinary bladder produces the conscious urge to urinate and when a person voluntarily chooses to urinate. This reinforces the micturition reflex. ## Body Fluid Compartments - **The intracellular fluid compartment**: - The fluid inside all of the cells in the body. - The cell membranes of each cell enclose the intracellular compartment, which comprises trillions of small compartments. - **The extracellular fluid compartment**: - All the fluid outside the cells. - It composes one-third of the entire body water. - It contains the interstitial fluid, the plasma within blood vessels, and the fluid in the lymphatic vessels ## Composition of the Fluid in the Body Fluid Compartments - **Intracellular fluid**: - Contains a relatively high concentration of ions like K+, magnesium (Mg2+), phosphate (PO4 3-), and sulfate (SO4 2-), compared to the extracellular fluid. - It has a lower concentration of Na+, Ca2+, Cl-, and HCO3- than the extracellular fluid. - Contains greater protein than the extracellular fluid. - Has a fairly consistent composition from one area of the body to another. ## Exchange Between Body Fluid Compartments - The major influence controlling the movement of water between the intracellular and extracellular spaces is osmosis. - If the extracellular concentration of ions increases, water moves by osmosis from cells into the extracellular fluid ## Regulation of Extracellular Fluid Composition - **Thirst** - Water intake is controlled by neurons in the hypothalamus. - When blood becomes more concentrated, the thirst center responds by initiating the sensation of thirst. ## Ion Concentration Regulation - Regulating the concentrations of positively charged ions like Na+, K+, and Ca2+, in the body fluids is essential. - Action potentials, muscle contraction, and normal cell membrane permeability rely on these ions. - **Sodium Ions** - Na+ is dominant in extracellular fluid. - ~90-95% of the osmotic pressure of the extracellular fluid stems from Na+ and the negative ions associated with them. - **Potassium Ions** - Electrically excitable tissues (muscles and nerves) are highly sensitive to slight changes in the extracellular K+ concentration. - The concentration of K+ must be maintained within a narrow range for these tissues to function. -**Calcium Ions** - The extracellular concentration of Ca2+ is maintained within a narrow range. - Increases and decreases in the extracellular concentration of Ca2+ have dramatic effects on the electrical properties of excitable tissues. ## Hormonal Regulation - **Parathyroid hormone (PTH)** - Secreted by the parathyroid glands. - Increases extracellular Ca2+ concentrations. - The rate of PTH secretion is regulated by the extracellular Ca2+ concentration. - **Phosphate and Sulfate Ions** - Ions like PO43- and SO42- are reabsorbed by active transport in the kidneys. - Rate of reabsorption in the kidneys is slow. - Excess is excreted into urine if the nephron is unable to reabsorb them. - Nearly all of these ions are reabsorbed by active transport. - The mechanism plays a major role in regulating the concentration of PO43- and SO42- in the body fluids. ## Regulation of Acid-Base Balance - **Buffers**: - Chemical substances that resist changes in pH of a solution. - Combine with H+ when H+ increases in those fluids, or release H+ when H+ decreases in those fluids. - Keep the H+ concentration, and thus the pH, within a narrow range of values. - **Respiratory System**: - Responds rapidly to changes in pH. - Helps bring the pH of body fluids back toward normal. - **Kidneys**: - Secrete H+ into the urine. - Can directly regulate the pH of the body fluids. - A powerful regulator of pH but responds more slowly. ## Acidosis and Alkalosis - **Acidosis**: - Blood pH falls below 7.35. - Affects the central nervous system, leading to malfunctions, disorientation, and coma. - **2 categories of acidosis**: - **Respiratory acidosis**: - Result of the respiratory system's inability to eliminate adequate amounts of CO2. - CO2 accumulation in the circulatory system lowers the pH of the body fluids. - **Metabolic acidosis**: - Stems from excess production of acidic substances like lactic acid and ketone bodies - Result of increased metabolism or decreased ability of the kidneys to eliminate H+ in the urine. - **Alkalosis**: - Blood pH increases above 7.45. - Hyper-excitability of the nervous system - **2 categories of alkalosis**: - **Respiratory alkalosis**: - Results from hyperventilation, which can happen in response to stress. - **Metabolic alkalosis**: - The rapid elimination of H+ from the body - Can happen during severe vomiting or when excess aldosterone is secreted by the adrenal cortex. ## Acute Renal Failure - **Acute renal failure** - Sudden and severe decrease in kidney function. - **Causes**: - **Dehydration**: Loss of body fluids. - **Infections**: Kidney infections or urinary tract infections. - **Trauma**: Injury to the kidneys. - **Toxins**: Exposure to chemicals or drugs. - **Diseases**: Diabetes, high blood pressure, etc. - **Symptoms**: - **Nausea**: Feeling sick to the stomach. - **Vomiting**: Throwing up. - **Fatigue**: Feeling tired. - **Shortness of breath**: Difficulty breathing. - **Swelling**: In the legs or ankles. - **Treatments**: - **Dialysis**: Filters the blood to remove waste products. - **Medications**: To treat the underlying cause of the kidney failure. ## Disease and Disorders of the Urinary System - **Glomerulonephritis**: - Inflammation of the glomeruli, which are tiny blood vessels in the kidneys. - **Acute glomerulonephritis**: - Sudden onset and often occurs after a bacterial infection, such as strep throat. - Symptoms usually subside after a few weeks. - **Chronic glomerulonephritis**: - Long-term and progressive process that can damage the kidneys. - Symptoms may include proteinuria (protein in the urine), hematuria (blood in the urine), and high blood pressure. - **Renal Failure**: - Condition in which the kidneys are unable to filter waste products from the blood. - **Acute renal failure**: - Sudden onset and can result from dehydration, infections, or toxins, - It may be reversible. - **Chronic renal failure** - A long-term and progressive decline in kidney function. - Often requires dialysis or a kidney transplant. - **Cystitis**: - Inflammation of the bladder. - Often caused by a bacterial infection. - Symptoms may include pain or burning during urination, frequent urination, and blood in the urine.