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STEP #2 Make the connections to key topics.
UNIT NINE Understanding the Urinary System
UNIT NINE
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Understanding the Urinary System
Formation of Urine Urine formation involves three processes: glomerular filtra- tion, tubular reabsorption, and tubular secretion. Glomerular Filtration In glomerular filtration, blood pressure forces water and small solutes out of the glomeruli and into Bowman capsules. This fluid is called renal filtrate (Fig. 36.3). Tubular Reabsorption and Secretion Exiting the glomerular capsule, renal filtrate enters the renal tubules. Tubular reabsorption is the recovery of useful mate- rials from the renal filtrate and their return to the blood in the peritubular capillaries (Table 36.1). In tubular secretion, substances are actively secreted from the blood in the peritu- bular capillaries into the filtrate in the renal tubules. The Kidneys and Acid–Base Balance Other than exhalation of carbon dioxide by the respiratory system, the kidneys are the organs most responsible for maintaining the normal pH range of blood and tissue fluid. They compensate for the pH changes that are part of normal body metabolism or the result of disease. In acidosis, the kidneys secrete more hydrogen ions into the renal filtrate and return more bicarbonate ions back to the blood. When body fluids become too alkaline, the kidneys return hydrogen ions to the blood and excrete bicarbonate ions in urine.
is an indentation, the hilus, where the renal artery enters and the renal vein and ureter emerge. The ureter carries urine from the kidney to the urinary bladder. Internal Structure of the Kidney A frontal section of the kidney shows three areas: the cortex, medulla, and pelvis (Fig. 36.1). Blood Vessels of the Kidney The pathway of blood flow through the kidney is an essen- tial part of the process of urine formation. Blood enters the kidney from the renal artery and exits through the renal vein. Extensive branching within the kidney eventually leads arte- rial blood to each afferent arteriole. This vessel begins the microcirculation at the nephron , the functional unit of the kidney. The exchanges that take place in the capillaries of the nephrons form urine from blood plasma. Nephrons Urine is formed in the approximately 1 million nephrons per kidney. The two major parts of a nephron are the renal cor- puscle with glomerulus and the renal tubule with peritubular capillaries (Fig. 36.2). These are the two sites of exchange between blood plasma and urinary filtrate within the nephron. All parts of the renal tubule are surrounded by the peritubular capillaries. The capillaries arise from the efferent arteriole and receive the materials reabsorbed by the renal tubules.
CHAPTER 36 Urinary System Function, Data Collection, and Therapeutic Measures Maureen McDonald, Janice L. Bradford
KEY TERMS azotemia (AY-zoh-TEE-me-ah) cystoscopy (sis-TAH-skuh-pee) dysuria (dis-YOO-ree-ah) hematuria (HEE-muh-TOOR-ee-ah)
LEARNING OUTCOMES 1. Identify the normal anatomy of the urinary system. 2. Describe the normal function of the urinary system. 3. Discuss the effects of aging on the urinary system. 4. Explain data to collect when caring for a patient with a disorder of the urinary system. 5. Plan preparation and postprocedure care for patients undergoing diagnostic tests of the urinary system. 6. Plan nursing care for patients with incontinence. 7. Discuss nursing actions to decrease the risk of infection in urinary catheterized patients.
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Urinary and Renal Disorders
incontinence (in-CON-tin-ense) nephrotoxic (NEF-row-TOK-sik) nocturia (knock-TOO-ree-ah) percutaneously (PUR-kyoo-TAY-nee-us-lee)
polyuria (pa-lee-YOO-ree-ah) pyelogram (PIE-eh-loh-gram)
CHAPTER CONCEPTS
NORMAL URINARY SYSTEM ANATOMY AND PHYSIOLOGY
Caring Elimination Teaching and learning
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The urinary system consists of two kidneys and two ureters, the urinary bladder, and the urethra. The kidneys form urine, and the rest of the system eliminates the urine. The purpose of urine formation is the removal of potentially toxic waste products from the blood; however, the kidneys have other equally important functions as well: • Regulation of blood volume, pressure, and composition by excretion or conservation of water • Regulation of the electrolyte balance of the blood by excretion or conservation of minerals • Regulation of the acid–base balance of the blood by the excretion or conservation of ions such as hydrogen or bicarbonate • Production of erythropoietin, which stimulates erythrocyte production in the bone marrow • Activation of vitamin D, which maintains bone health The process of urine formation helps maintain the normal composi- tion, volume, and pH of blood and tissue fluid. Kidneys The bilateral kidneys are located against the posterior wall of the abdominal cavity. They are retroperitoneal. The superior portions of both kidneys rest on the inferior surface of the diaphragm; these por- tions are protected by the lower rib cage. The kidneys are cushioned by surrounding adipose tissue. This tissue is covered by a fibrous connec- tive membrane, the renal fascia. On the medial surface of each kidney
The renal cortex forms the outer region of the kidney.
Fibrous capsule
The renal medulla forms the inner region.
Extensions from the renal cortex, called renal columns , divide the interior region into cone-shaped sections.
The cone-shaped sections are called renal pyramids . Consisting of tubules for transporting urine away from the cortex, the base of each pyramid faces outward toward the cortex. The point of the pyramid, called the renal papilla , faces the hilum.
Urinary and Renal Disorders
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Hilum
The renal papilla extends into a cup called a minor calyx . The calyx collects urine leaving the papilla.
Renal papilla
Two or three minor calyces join together to form a major calyx .
Ureter
The major calyces converge to form the renal pelvis , which receives urine from the major calyces. The renal pelvis continues as the ureter , a tube-like structure that channels urine to the urinary bladder.
FIGURE 36.1 Interior of the kidney.
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Pre-Assessment for Urinary and Renal Disorders
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Question 2 of 6 The health-care provider alerts the nurse that a patient is at risk for chronic kidney disease. Which risk factors should the nurse expect to find in this patient’s chart? Select all that apply. Diabetes mellitus
Urinary calculi Hypertension Autoimmune disease Acute urinary tract infection
Pre-Assessment for Urinary and Renal Disorders
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