Chapter 18 - Urinary System and Fluid Balance PDF

ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 URINARY SYSTEM KIDNEY KIDNEY CHARACT...

ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 URINARY SYSTEM KIDNEY KIDNEY CHARACTERISTICS o The urinary system is the major excretory system of the body FUNCTIONS OF THE URINARY SYSTEM 1. Excretion 2. Regulation of blood volume and blood pressure o Bilateral retroperitoneal organs 3. Regulation of blood solute o Retroperitoneal – behind concentration an organ with peritoneum 4. Regulation of extracellular fluid pH 5. Regulation of RBC synthesis Shape and size 6. Regulation of Vitamin D synthesis o Bean-shaped COMPONENTS OF THE URINARY o Weighs 5 ounces (bar of soap or SYSTEM size of fist) 1. Two kidneys Location 2. Two ureters 3. One urinary bladder o Between 12th thoracic and 3rd 4. One urethra lumbar vertebra ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 KIDNEY STRUCTURES o Calyx – tip of pyramids (major and minor calyx) o Minor calyx – collects the urine coming from the tip of the renal pyramids o Major calyx – where the urine collected in minor calyx flows o Adipose tissue – surrounds kidney LONGITUDINAL SECTION OF THE KIDNEY o Hilum – indention; contains renal artery veins, nerves, ureter o Renal capsule – connective tissue around each kidney; protects and BLOOD FLOW THROUGH THE KIDNEY acts as a barrier o Renal sinus – contains renal pelvis, blood vessels, fats o Renal cortex – outer portion o Renal medulla – inner portion o Renal pyramid – junction between cortex and medulla o Renal artery – has oxygen-rich blood o Renal vein – has poor blood oxygen o Renal fascia – connective tissue 1. Renal artery that surrounds the kidney; divides 2. Interlobar artery the layers of fats in the kidney 3. Arcuate artery o Renal papilla – where the urine 4. Interlobular artery that has been formed exits 5. Afferent arteriole o Renal pelvis – where calyces 6. Glomerulus join; narrows to form the ureter 7. Efferent arteriole ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 8. Peritubular capillaries ▪ Approximately 85% 9. Vasa recta of the nephrons 10. Interlobular vein o The nephron includes: renal 11. Arcuate vein corpuscle, proximal tubule, loop 12. Interlobar vein of Henle, distal tubule, and collecting duct NEPHRON NEPHRON COMPONENTS Renal corpuscle o Structure that contains a Bowman’s capsule and glomerulus Bowman’s capsule o Enlarged end of nephron o Opens into proximal tubule o Contains podocytes o Podocytes ▪ Specialized cells around glomerular capillaries ▪ Have spaces where o The nephron is the functional unit the fluid could stay of the kidney o Each kidney has over one million Glomerulus nephrons o Contains capillaries wrapped o There are two types of nephrons: around it (1) juxtamedullary and (2) cortical Filtration membrane o Juxtamedullary nephrons o In renal corpuscle ▪ Loop of henle o Includes glomerular capillaries, extends to the deep podocytes, and basement part of the medulla membrane ▪ Approximately 15% Filtrate of the nephrons o Cortical nephrons o Fluid that passes across filtration ▪ Loop of Henle does membrane no extend to the Proximal tubule deep part of the medulla o Where filtrate passes first ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 Loop of Henle o Contains descending and ascending loops o Water and solute pass through thin walls by diffusion Distal tube o Structure between loop of Henle and collecting duct Collecting duct o Empties into calyces (major and minor) o Carry fluid from cortex through FLOW FILTRATE THROUGH medulla NEPHRONS RENAL CORPUSCLE AND 1. Renal corpuscle FILTRATION MEMBRANE 2. Proximal convoluted tubule 3. Descending loop of Henle 4. Ascending loop of Henle 5. Distal convoluted tubule 6. Collecting duct 7. Papilalry duct URINE FORMATION Urine formation involves three processes: 1. Filtration – occurs in the renal corpuscle 2. Reabsorption – involves removing substances from the ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 filtrate and placing back into the o Proximal tubule – primary site for blood reabsorption of solutes and water 3. Secretion – involves taking o Descending loop of Henle – substances from the blood at a concentrates filtrate nephron area, other than the renal o Reabsorption of water and solutes corpuscle, and putting back into from distal tubule and collecting the nephron tubule duct is controlled by hormones FILTRATION REABSORPTION IN THE PROXIMAL CONVOLUTED TUBULE o Movement of water, ions, small molecules, through filtration membrane into Bowman’s capsule o 19% plasma becomes filtrate o 180L of filtrate are produced by the nephrons each day o 1% of the filtrate (1.8L) become urine, the rest is reabsorbed o Only small molecules are able to pass through filtration membrane o Formation of filtrate depends on REABSORPTION IN THE LOOP OF filtration pressure HENLE o Filtration pressure forces fluid across filtration membrane and this filtration pressure is influenced by blood pressure FILTRATION PRESSURE REABSORPTION o 99% of filtrate is reabsorbed and re-enters circulation ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 DISTAL CONVOLUTED TUBULE AND COLLECTING DUCT REABSORPTION REABSORPTION IN THICK SEGMENT OF THE ASCENDING LIMB SECRETION o Tubular secretion – removes some substances from the blood; occurs through either active or passive mechanisms o These substances include byproducts of metabolism that become toxic in high concentrations and drugs or other molecules not normally produced by the body o Ammonia secretion is passive o Secretion of H=, K=, creatinine, and histamine is by active transport o The secretion of H+ plays an important role in regulating body fluid pH ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 URINE CONCENTRATION o Consequently, solutes diffuse out of the nephron o Descending limb of loop of Henle – critical site for water URINE-CONCENTRATING reabsorption MECHANISM o The filtrate leaving the proximal convoluted tubule is further concentrated as it passes through the descending limb of the loop of Henle o The mechanism for this water reabsorption is via osmosis ▪ Renal medulla – contains very concentrated interstitial fluid that has large amounts of Na+, Cl-, and urea o Wall of the thin segment of descending limb – highly permeable to water o As the filtrate moves through the medulla URINE CONCENTRATION AND containing the highly VOLUME REGULATION concentrated interstitial Three major hormonal mechanisms are fluid, water is reabsorbed involved in regulating urine concentration out of the nephron by and volume osmosis o The water enters the vasa 1. Renin-angiotensin-aldosterone recta 2. Antidiuretic hormone (ADH) o Ascending limb of loop of Henle 3. Atrial natriuretic hormone – dilutes the filtrate by removing solutes RENIN-ANGIOTENSIN-ALDOSTERONE o Thin segment of the MECHANISM ascending limb 1. Renin acts on angiotensinogen ▪ Not permeable to o Produces angiotensin water 2. Angiotensin-converting enzyme ▪ Permeable to o Converts angiotensin I → solutes angiotensin II ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 3. Angiotensin II causes ADH and the regulation of the vasoconstriction extracellular fluid 4. Angiotensin II acts on adrenal cortex o Release aldosterone o Increases rate of active transport of Na+ in distal tubules and collecting duct 5. Volume of water → decreases Aldosterone actions ATRIAL NATRIURETIC HORMONE ANTIDIURETIC HORMONE 1. ANH is secreted from cardiac MECHANISM muscle in the right atrium of the 1. ADH is secreted by the posterior heart when blood pressure pituitary gland increases o ADH acts on kidneys → o ANH acts on kidneys → absorbs more water → decrease Na+ reabsorption decrease in urine volume 2. Sodium ions remain in nephron to o Results to a maintain in normal become urine blood value and blood o Increased loss of sodium and pressure water → reduced blood volume and blood pressure ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 HOMEOSTATIC CONTROL OF BLOOD URINE MOVEMENT AND URINE VOLUMES Micturition reflex URETERS AND URINARY BLADDER o Activated by stretch of urinary bladder wall o Action potentials are conducted from bladder to spinal cord through pelvic nerves o Parasympathetic action potentials – cause bladder to contract o Stretching of bladder stimulates sensory neurons to inform brain that the person needs to urinate Ureters BODY FLUID COMPARTMENTS o Small tubes that carry urine from the renal pelvis of kidney to o Intracellular fluid compartment – bladder includes the fluid inside all the cells of the body Urinary bladder o Approximately two-thirds of o In pelvic cavity all the water in the body is o Stores urine in the intracellular fluid o Can hold a few ml to a maximum of compartment 1000 milliliters o Extracellular fluid compartment – includes all the fluid outside the URETHRA cells o Tube that exits bladder o Includes the interstitial o Carries urine from urinary fluid, plasma, lymph, and bladder to outside of the body other special fluids, such as joint fluid and cerebrospinal fluid ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 COMPOSITION OF FLUIDS decrease, due to a dilution effect; this causes the sensation of thirst Intracellular fluid to decrease o Contains a relatively high THIRST REGULATION OF concentration of ions, such as K+, EXTRACELLULAR FLUID magnesium (Mg2+), phosphate CONCENTRATION (PO33-), and sulfate (SO42-), compared to extracellular fluid o It has lower concentration of Na+, Ca2+, Cl-, and HCO3-, than does the extracellular fluid EXCHANGE BETWEEN FLUID COMPARTMENTS o The cell membranes that separate the body fluid compartments are ION CONCENTRATION REGULATION selectively permeable o Regulating the concentrations of o Water continually passes through positively charged ions, such as them, but ions dissolved in the Na+, K+, and Ca2+, in the body water do not readily pass through fluids is particularly important the cell membrane o Action potentials, muscle o Water movement is regulated contraction, and normal cell mainly by hydrostatic pressure membrane permeability differences and osmotic depend on the differences between the maintenance of a narrow compartments range of these o Osmosis controls the movement concentrations of water between intracellular and o Negatively charged ions, such as extracellular spaces Cl-, are secondarily regulated by REGULATION OF EXTRACELLULAR the mechanisms that control the FLUID COMPOSITION positively charged ions o The negatively charged o Thirst center of the ions are attracted to the hypothalamus – where water positively charged ions; intake is controlled when the positively o When the concentration of ions charged ions are in the blood increases, it transported, the negatively stimulates the thirst center to charged ions move with cause thirst them o When water is consumed, the concentrations of blood ions ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 SODIUM IONS CALCIUM IONS o Sodium ions (Na+) are the o The extracellular concentration of dominant ions in the Ca2+ is maintained extracellular fluid o Increases and decreases in the o About 90% to 95% of the osmotic extracellular concentration of Ca2+ pressure of the extracellular fluid have dramatic effects on the results from sodium ions and from electrical properties of excitable the negative ions associated with tissues them Parathyroid hormone (PTH) o Stimuli that control aldosterone secretion, influence the o Secreted by the parathyroid reabsorption of the kidneys, and glands the total amount of Na+ in the body o Increases extracellular Ca2+ fluids concentrations o Sodium ions – are excreted in sweat Calcitonin POTASSIUM IONS o Reduces the blood Ca2+ concentration when it is too high o Electrically excitable tissues, such as muscles and nerves, are highly PHOSPHATE AND SULFATE IONS sensitive to slight changes in the o Phosphate ions and sulfate ions extracellular K+ concentration are reabsorbed by active transport o The extracellular concentration of in the kidneys K+ must be maintained within a o The rate of reabsorption is slow, narrow range for these tissues to so that if the concentration of these function normally ions in the filtrate exceeds the o Aldosterone plays a major role in nephron’s ability to reabsorb them, regulating the concentration of K+ the excess is excreted into the in the ECF urine REGULATION OF BLOOD POTASSIUM o As long as the concentration of LEVELS these ions is low, nearly all of them are reabsorbed by active transport REGULATION OF ACID-BASE BALANCE Buffers o Chemicals resist change in pH of a solution ANGELES, Y.  ANATOMY AND PHYSIOLOGY TOPIC: URINARY SYSTEM AND FLUID BALANCE 1NU08 | BS NURSING 1ST SEMESTER | AY 2022-2023 o Buffers in body contain salts of ACIDOSIS AND ALKALOSIS weak acids or bases that Acidosis combine with H+ o Three classes of buffers: o Occurs when the pH of blood falls o Proteins below 7.35 o Phosphate buffer o Two types of acidosis based o Bicarbonate buffer upon the cause: respiratory and metabolic Respiratory involvement of Acid-Base Alkalosis o Responds rapidly to changes in pH o Increased respiratory rate raises o Occurs when the pH of blood is blood pH (more alkalotic) above 7.45 o Due to increased rate of o Two types of alkalosis based carbon dioxide elimination upon the cause: respiratory and from the body metabolic o Reduced respiratory rate reduces pH (more acidic) o Due to decreased rate of carbon dioxide elimination from the body Kidney involvement in acid-base o Nephrons secrete H+ into urine and directly regulate pH of body fluids o More H+ secretion = pH is decreasing o Less H+ secretion = pH is increasing ANGELES, Y.