Lecture Outline I. Overview of the Urinary System (p. 829) A. Primary organs 1. Kidneys B. Accessory organs

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1 Thibodeau: Anatomy and Physiology, 5/e Chapter 28: Urinary System It will be helpful to begin this chapter by pointing out that the urinary system does more than simply produce urine. It can also be thought of as the "blood plasma balancer." Each kidney processes incoming blood plasma in ways that allow it to leave the kidney in better condition. Water content is adjusted so that the body does not have too much or too little water to maintain constancy of the internal environment. Likewise, the blood content of important ions such as sodium and potassium is adjusted to match set point levels. Even the ph of the blood can be altered to match the set point level. In these ways, the urinary system regulates the content of blood plasma so that the homeostasis of the entire internal fluid environment can be maintained within normal limits. This chapter examines the unified structure and function of all crucial components of the urinary system, beginning with a discussion of the gross structure (kidney, ureter, urinary bladder, and urethra) and then the microscopic structure (including Bowman's capsule, proximal tubule, loop of Henle, distal tubule, and collecting ducts), in addition to the blood vessels of the kidney. Overall function of the kidney is examined in terms of filtration and reabsorption. A number of renal and urinary disorders are covered. Objectives After students have completed this chapter, they should be able to: 1. List the major organs of the urinary system. 2. Discuss and compare the structure and the functions of the ureters, urinary bladder, and urethra. 3. Locate or position the kidneys in the abdominal cavity and identify the gross internal structures visible in a coronal section. 4. Name the parts of a nephron and describe the role of each component in the formation of urine. 5. Describe the renal blood supply and trace blood flow through the specialized vessels of the kidney. 6. Discuss how the kidneys form urine and trace urine from its point of formation to the exterior of the body. 7. Discuss filtration, reabsorption, and secretion in relation to the formation of urine by the kidneys. 8. Discuss the countercurrent mechanisms for concentrating or diluting urine. 9. Explain how urine volume is regulated under normal conditions. 10. Describe the physical characteristics of normal urine. Lecture Outline I. Overview of the Urinary System (p. 829) A. Primary organs 1. Kidneys B. Accessory organs C. Function 1. Ureters 2. Urinary bladder 3. Urethra 1. Blood plasma balancer

2 Chapter 28: Urinary System 2 a. Balances water content of plasma b. Balances ions in plasma c. Balances ph of plasma II. Anatomy of the Urinary System (Fig. 28-1) A. Gross structure 1. Kidney (Fig. 28-2) a. Location b. Parts 1) Left kidney larger and higher 2) Right kidney slightly smaller and lower 3) Kidneys retroperitoneal 4) Three layers of connective tissue around the kidney a) Outer renal fascia hold kidney to other structures b) Middle adipose capsule (renal fat pad) surrounds kidney (Fig. 28-1) c) Inner renal capsule (fibrous capsule) surround the kidney tightly (Fig. 28-2) 1) Hilum (Fig. 28-2) a) Concave depression where blood vessels and ureter enter and leave kidney 2) Cortex (outer layer) (Fig 28-2) a) Renal columns (inward projections of cortex) 3) Medulla (Fig 28-2) a) Renal pyramids are the sections of medulla (6 to 18 per kidney) b) Renal papilla is the tip of the pyramid 4) Calyx (Fig 28-2) a) A membrane that surrounds the tip of the pyramid b) First urine gathering tube; all nephrons empty in the calyces 5) Renal pelvis (Fig 28-2) a) All calyces join together to form the renal pelvis b) Renal pelvis is in cavity called the renal sinus c) Renal pelvis becomes the ureters c. Blood vessels of the kidneys (Fig. 28-3)

3 Chapter 28: Urinary System 3 1) Lobar artery 2) Interlobar arteries 3) Arcuate arteries 4) Interlobular artery 5) Afferent arteriole 6) Glomerular capillaries (Glomerulus) 7) Efferent arteriole 8) Peritubular capillaries (including vasa recta) 9) Venules 10) Interlobular veins 11) Arcuate veins 12) Interlobar veins 13) Renal vein 2. Ureter (Figs. 28-2, 28-5) a. Muscular wall propels urine by peristalsis b. Ureter starts at renal pelvis and ends at urinary bladder 3. Urinary bladder (Fig. 28-5) a. Below the peritoneum and posterior to pubic symphysis b. Muscular walls c. Inner epithelium folded to form rugae when bladder is empty d. Trigone a posterior area between the two ureter openings and the urethral opening 4. Urethra (Fig. 28-5) a. Length: female 3 cm; male 20 cm b. In male, it passes through the prostate gland and is joined in that gland by two ejaculatory ducts; it passes through the penis and ends as a urinary meatus c. Micturition (p. 835) 1) The process of voiding urine B. Microscopic structure of the nephron (Fig. 28-4) a) First, relaxation of external bladder sphincter muscle b) Then, contraction of bladder muscle 1. Renal corpuscle made of two parts (Fig. 28-6) a. Bowman's capsule tubular component b. Glomerulus vascular component 2. The tube of the nephron 1) Glomerular-capsular membrane (Fig. 28-7)

4 Chapter 28: Urinary System 4 a. Bowman's capsule b. Proximal convoluted tubule c. Loop of Henle 1) Descending limb 2) Loop 3) Ascending limb d. Distal convoluted tubule 3. Collecting duct a. Several nephron distal convoluted tubules enter the collecting duct b. Collecting ducts join to make larger collecting ducts c. Larger collecting ducts empty by way of renal papilla into the calyx 4. Juxtaglomerular apparatus (Fig. 28-4) III. Physiology of the Urinary System (p. 838) A. Overview of kidney function a. Located where afferent arteriole touches the distal convoluted tubule b. Juxtaglomerular cells in afferent arteriole secrete renin when blood pressure drops; the cells are mechanoreceptors (See Figure for the details; use for review) c. Macula densa cells in distal tubule of the juxtaglomerular apparatus are chemoreceptors that can sense solute concentration in the tubule 1. Urine formation (Fig. 28-8; Table 28-1) a. Filtration (Figs. 28-8, 28-9, 28-10) 1) Occurs between glomerulus and Bowman's capsule 2) Effective filtration pressure: 10 mm Hg (Fig ) 3) Glomerular filtration rate: gives 180 liters of filtrate per day b. Reabsorption (Figs. 28-9, 28-11) 1) Proximal tubule (p. 841) a) Active transport of sodium out of tubule b) Cotransport of glucose and amino acids out of tubule c) Chloride ions moving out of tubule d) Water moving out of tubule e) Urea moving out of tubule f) No control over this reabsorption 2) Loop of Henle (p. 842)

5 Chapter 28: Urinary System 5 a) Countercurrent flow (Figs , 28-13, 28-14) b) Water moving out of the tube in descending limb c) Sodium and chloride moving out in ascending limb d) Result: concentrated NaCl deep in the pyramid 3) Distal tubules and collecting ducts (Figs , 28-16) a) Reabsorption of water ADH b) Movement of urea out of tubule c. Tubular secretion by distal convoluted tubules and collecting ducts (Fig. 28-8) 1) Tubular secretion means movement of molecules from the blood into the tubular fluid 2) Molecules are secreted 2. Regulation of urine volume (Fig ) a) Potassium ion secretion increases in the presence of aldosterone; Na ions move back into the blood b) Hydrogen ion secretion increases when blood H+ increases c) Ammonium ions diffuse into the tubules as formed a. Antidiuretic hormone (ADH) gives more concentrated urine; conserves water in blood b. Aldosterone gives more concentrated urine: conserves water in blood c. Atrial natriuretic hormone (ANH) gives more dilute urine because of Na + secretion into the urine d. Tubuloglomerular feedback e. Myogenic mechanism 3. Urine composition (Table 28-2) a. Water (about 95% of the urine) 1) ph: ) Specific gravity: b. Nitrogenous wastes c. Electrolytes d. Toxins e. Pigments

6 Chapter 28: Urinary System 6 f. Hormones g. Abnormal constituents IV. Cycle of Life: Urinary System (p. 850) A. Kidney function less efficient in newborn B. Adult changes from disease or trauma C. Older adult deterioration of kidney function V. The Big Picture: Urinary System and the Whole Body (p. 850) A. Regulated by nervous and endocrine systems B. Interactions with other body cells 1. Removal of toxins 2. Water, ph, and electrolyte homeostasis VI. Mechanisms of Disease: Renal and Urinary Disorders (p. 850) A. Obstructive disorders hydronephrosis 1. Renal calculi (kidney stones) 2. Neurogenic bladder 3. Tumors and other obstructions B. Urinary tract infections 1. Urethritis 2. Cystitis 3. Nephritis C. Glomerular disorders 1. Nephrotic syndrome a. Proteinuria b. Hypoalbuminemia c. Edema 2. Acute glomerulonephritis 3. Chronic glomerulonephritis D. Kidney failure 1. Acute renal failure 2. Chronic renal failure a. Stage 1 b. Stage 2 c. Stage 3