Copyright © 2016 by Elsevier Inc. All rights reserved. Urinary System Chapter 18 Copyright © 2016 by Elsevier Inc. All rights reserved.

Learning Objectives Lesson 18.1: Urinary System Identify the major organs of the urinary system and give the generalized function of each. Name the parts of a nephron and describe the role each component plays in the formation of urine. Explain how the kidneys act as vital organs in maintaining homeostasis. Copyright © 2016 by Elsevier Inc. All rights reserved.

Learning Objectives Lesson 18.1: Urinary System (Cont.) Explain the importance of filtration, reabsorption, and secretion in urine formation. Discuss the mechanisms that control urine volume, including the normal amount and composition of urine. Explain the process of urine elimination. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Kidneys Location of the kidneys Under back muscles, behind parietal peritoneum, just above waistline Right kidney usually a little lower than left (Figure 18-1) Gross structure: Internal anatomy (Figure 18-2) Renal cortex Outer layer of kidney substance Renal medulla Inner portion of kidney Renal pyramids Triangular divisions of medulla Both kidneys are protected a bit by the lower rib cage. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Kidneys (Cont.) Gross structure: Internal anatomy Renal papilla (pl. papillae) Narrow, innermost end of pyramid Renal pelvis Expansion of upper end of ureter; lies inside kidney Calyx (pl. calyces) Division of renal pelvis Once the peritoneum has been cut/opened, the potential for spread of infection throughout the entire abdominal cavity increases. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Urinary System Figure 18-1, A, shows the anterior view of urinary organs. Figure 18-1, B, shows surface markings of the kidneys, eleventh and twelfth ribs, spinous processes of L1 to L4, and lower edge of pleura viewed from behind. Figure 18-1, C, shows horizontal (transverse) section of abdomen, which shows the retroperitoneal position of the kidneys. Figure 18-1, D, shows x-ray film of urinary organs. B From Abrahams P, Marks SC, Hutchings RT: McMinn’s color atlas of human anatomy, ed 5, Edinburgh, 2003, Mosby. Copyright © 2016 by Elsevier Inc. All rights reserved.

Internal Structure of the Kidney Figure 18-2, A, shows an artist’s rendering of a coronal section of the kidney. Figure 18-2, B, is a photomicrograph of a coronal section of a preserved human kidney. From Abrahams PH, Spratt JD, Loukas M, van Schoor AN: McMinn & Abrahams’ clinical atlas of human anatomy, ed 7, Edinburgh, 2013, Elsevier Ltd. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Kidneys (Cont.) Microscopic structure Nephrons are microscopic units of kidneys Consist of renal corpuscle and renal tubule (Figure 18-3) Renal corpuscle (Figure 18-4) Bowman capsule Cup-shaped top of a nephron Glomerulus Network of blood capillaries tucked into the Bowman capsule More than a million microscopic units called nephrons make up each kidney’s interior. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Kidneys (Cont.) Microscopic structure Renal tubule Proximal convoluted tubule (PCT) First segment of a renal tubule Nephron loop (Henle loop) Extension of proximal tubule; consists of straight descending limb, hairpin turn, and straight ascending limb Distal convoluted tubule (DCT) Part of tubal distal to ascending limb of nephron loop Collecting duct (CD) Straight part of a renal tubule The shape of a nephron is unique, unmistakable, and admirably suited to its function of producing urine. It looks like a tiny funnel with a very long stem. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Location of Nephrons Figure 18-3: Magnified wedge cut from a renal pyramid shows an example of a cortical nephron and a juxtamedullary nephron. Copyright © 2016 by Elsevier Inc. All rights reserved.

Renal Corpuscle Figure 18-4, A, is a schematic drawing that shows the relationship of glomerulus to Bowman capsule (together called the renal corpuscle) and adjacent structures. Figure 18-4, B, is a scanning electron micrograph showing several glomeruli and their associated blood vessels. Courtesy Andrew P Evan, University of Indiana. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Kidneys (Cont.) Overview of kidney function Excretes toxins and nitrogenous wastes Regulates levels of many chemicals in blood Maintains water balance Helps regulate blood pressure via secretion of renin Secretes erythropoietin (EPO) Homeostasis cannot be maintained if the kidneys fail and the condition is not soon corrected. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Formation of Urine Occurs by a series of three processes that take place in successive parts of nephron (Figure 18-6 and Table 18-1) Filtration Goes on continually in renal corpuscles Glomerular blood pressure causes water and dissolved substances to filter out of glomeruli into Bowman capsule Normal glomerular filtration rate 125 mL per minute The kidneys have 2 million (or more) nephrons. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Formation of Urine Figure 18-6: Diagram shows examples of the steps in urine formation in successive parts of a nephron: filtration, reabsorption, and secretion. Copyright © 2016 by Elsevier Inc. All rights reserved.

Functions of Parts of Nephron in Urine Formation Table 18-1 shows the functions of parts of the nephron in urine formation. Copyright © 2016 by Elsevier Inc. All rights reserved.

Formation of Urine (Cont.) Reabsorption Movement of substances out of renal tubules into blood in peritubular capillaries Water, nutrients, and ions are reabsorbed Water is reabsorbed by osmosis from proximal tubules Secretion Movement of substances into urine in the distal and collecting tubules from blood in peritubular capillaries Hydrogen ions, potassium ions, and certain drugs are secreted by active transport Ammonia is secreted by diffusion The kidneys’ nephrons form urine by way of a combination of these three blood-balancing processes: filtration, reabsorption, and secretion. Copyright © 2016 by Elsevier Inc. All rights reserved.

Control of Urine Volume Antidiuretic hormone (ADH) Secreted from the posterior pituitary gland Decreases the amount of urine by collecting ducts permeable to water Aldosterone Secreted by the adrenal cortex Stimulates the tubules to reabsorb sodium at a faster rate Atrial natriuretic hormone (ANH) Secreted from the heart’s atrial wall Stimulates kidney tubules to secrete more sodium and thus lose more water The body has ways to control the amount and composition of the urine that it excretes – mainly by controlling the amount of water and dissolved substances that are reabsorbed by the kidney tubules. Copyright © 2016 by Elsevier Inc. All rights reserved.

Control of Urine Volume (Cont.) Abnormalities of urine volume Anuria: Absence of urine Oliguria: Scanty amount of urine Polyuria: Unusually large amount of urine Because a change in urine volume/output is a significant indicator of many diseases, measurement of both fluid intake and output is necessary. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Elimination of Urine Ureters (Figure 18-10) Structure Narrow, long tubes with expanded upper end (renal pelvis) located inside kidney and lined with mucous membrane Function Drain urine from renal pelvis to urinary bladder The renal pelvis is the basinlike upper end of the ureter located inside of the kidney. Episodes of renal colic (pain caused by the passage of kidney stone) is painful for a couple of reasons, such as tearing or stretching of the urinary lining and cramping muscles. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Ureter Cross Section Figure 18-10 shows the cross section of a ureter. From Telser A, Young J, Baldwin K: Elsevier’s integrated histology, Philadelphia, 2008, Mosby. Copyright © 2016 by Elsevier Inc. All rights reserved.

Elimination of Urine (Cont.) Urinary bladder (Figure 18-11) Structure Elastic muscular organ, capable of great expansion Lined with mucous membrane arranged in rugae, as is stomach mucosa Functions Storage of urine before voiding Voiding When the bladder is filled, its inner surface may stretch until it is smooth. Copyright © 2016 by Elsevier Inc. All rights reserved.

Structure and Location of the Urinary Bladder Figure 18-11, A, shows a frontal view of a fully distended male bladder dissected to show the interior. Figure 18-11, B, shows a sagittal section of the female urinary system (left) and the male urinary system (right) showing relationship of the bladder to other anatomical structures. Copyright © 2016 by Elsevier Inc. All rights reserved.

Elimination of Urine (Cont.) Urethra Structure Narrow tube from urinary bladder to exterior Lined with mucous membrane Opening of urethra to the exterior called urinary meatus Functions Passage of urine from bladder to exterior of the body Passage of male reproductive fluid (semen) from the body Cystitis Bladder infection Urethra is a narrow tube; only about 4 cm long in a woman and about 8 cm long in a man. In the man, a urethra has two functions: (1) terminal portion of urinary tract and (2) passageway for movement of semen. Copyright © 2016 by Elsevier Inc. All rights reserved.

Elimination of Urine (Cont.) Micturition Passage of urine from body (also called urination or voiding) Regulatory sphincters Internal urethral sphincter (involuntary) External urethral sphincter (voluntary) Bladder wall permits storage of urine with little increase in pressure Two sphincters act as valves that guard the pathway leading from the bladder. Copyright © 2016 by Elsevier Inc. All rights reserved.

Elimination of Urine (Cont.) Micturition Emptying reflex Initiated by stretch reflex in bladder wall Bladder wall contracts Internal sphincter relaxes External sphincter relaxes, and urination occurs Muscular wall of the bladder permits this organ to accommodate a considerable volume of urine with very little increase in pressure until a volume of 300 mL to 400 mL is reached. Copyright © 2016 by Elsevier Inc. All rights reserved.

Elimination of Urine (Cont.) Micturition Urinary retention Urine produced but not voided Urinary suppression No urine produced but bladder is normal Urinary incontinence Urine is voided involuntarily; a common bladder control problem in elderly people May be caused by spinal injury or stroke Retention of urine may cause cystitis Micturition is a complex body function; it requires control and integration of both voluntary and involuntary nervous system components. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Urinalysis Physical, chemical, and microscopic examination of urine Sign of a disease Changes in normal characteristics of urine Appearance of abnormal urine characteristics Like blood, urine is a fluid that reveals much about the function of the body. Urinalysis may help determine the presence and nature of a pathologic condition. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Questions? Copyright © 2016 by Elsevier Inc. All rights reserved.