Urinary System (Obj 7) 2024 PDF

Objective 7: Urinary System PN 1241 Chapter 25 7. Discuss the structure and function of the urinary system. 7.1 Define key terms related to the urinary system. 7.2 Discuss the primary functions of the urinary system. 7.3 Identify the main structures of the urinary system. 7.4 Discuss the structure a...

Objective 7: Urinary System PN 1241 Chapter 25 7. Discuss the structure and function of the urinary system. 7.1 Define key terms related to the urinary system. 7.2 Discuss the primary functions of the urinary system. 7.3 Identify the main structures of the urinary system. 7.4 Discuss the structure and functions of the kidneys. 7.5 Discuss the structure and functions of the nephrons. 7.6 Discuss the three steps involved in the formation of urine. 7.7 Discuss how the kidneys regulate the volume and concentration of urine. 7.8 Discuss the normal and abnormal characteristics of urine. 7.9 Discuss the structure and functions of the: a) ureters. b) urinary bladder. c) urethra. 7.10 Discuss the process of micturition. Kidneys, a major excretory organ, maintain the body’s internal environment by: Function of Kidneys © 2016 Pearson Education, Inc. Regulating total water volume and total solute concentration in water Regulating ion concentrations in extracellular fluid (ECF) Ensuring long-term acid-base balance Excreting metabolic wastes, toxins, drugs Producing erythropoietin (regulates blood pressure) and renin (regulates RBC production) Kidneys are part of the urinary system, which also includes: Ureters: transport urine from kidneys to urinary bladder Function of Kidneys Urinary bladder: temporary storage reservoir for urine Urethra: transports urine out of body Summary: Urinary System Structures (visiblebody.com) © 2016 Pearson Education, Inc. Hepatic veins (cut) Esophagus (cut) Inferior vena cava Renal artery Adrenal gland Renal hilum Renal vein Aorta Kidney Iliac crest Ureter Rectum (cut) Uterus (part of female reproductive system) Urinary bladder Urethra Figure 25.1 The urinary system. © 2016 Pearson Education, Inc. Location and External Anatomy Gross Anatomy of Kidneys © 2016 Pearson Education, Inc. bean shaped Retroperitoneal, in the superior lumbar region Located between T12 and L5 Right kidney is crowded by liver, so it lies lower than left Convex lateral surface Concave medial surface with vertical renal hilum leads to internal space called renal sinus Ureters, renal blood vessels, lymphatics, and nerves enter and exit at hilum and occupy the sinus Adrenal (suprarenal) gland sits atop each kidney 12th rib © 2016 Pearson Education, Inc. Three layers of supportive tissue surround kidney: Location and External Anatomy (cont.) Renal fascia Anchoring outer layer of dense fibrous connective tissue Anchors adrenal gland and kidney to surrounding structures Peri-renal fat capsule Fatty cushion around kidney Protects it Helps hold in position Fibrous capsule Transparent capsule that prevents spread of infection in close regions from spreading to kidney © 2016 Pearson Education, Inc. Internal kidney has three distinct regions: 1. Renal cortex: superficial region 2..Renal medulla: deep, composed of cone-shaped medullary (renal) pyramids Renal pyramids are separated by renal columns Lobe: each medullary pyramid and its surrounding cortical tissue make up a lobe; about eight lobes per kidney Internal Gross Anatomy 3. Renal pelvis Funnel-shaped tube continuous with ureter Branching extensions form: Minor calyces Cup-shaped areas that collect urine draining from pyramidal papillae Major calyces Areas that collect urine from minor calyces Empty urine into renal pelvis © 2016 Pearson Education, Inc. Urine flow Internal Gross Anatomy (cont.) Renal pyramid → minor calyx → major calyx → renal pelvis → ureter -> bladder The walls of the calyces, pelvis, and ureter contain smooth muscle that contracts to propel urine by peristalsis Summary: Kidneys | Urinary Anatomy (visiblebody.com) © 2016 Pearson Education, Inc. Figure 25.4 Internal anatomy of the kidney. Renal hilum Renal cortex Renal medulla Major calyx Papilla of pyramid Renal pelvis Minor calyx Ureter Renal pyramid in renal medulla Renal column Fibrous capsule Photograph of right kidney, frontal section © 2016 Pearson Education, Inc. Diagrammatic view Blood and Nerve Supply Blood: kidneys cleanse blood and adjust its composition, so it has a rich blood supply Renal arteries deliver about one-fourth (1200 ml) of cardiac output to kidneys each minute; branches in kidney until it reaches each nephron © 2016 Pearson Education, Inc. Nerve supply: sympathetic fibers from renal plexus Figure 25.5b Blood vessels of the kidney. Aorta Inferior vena cava Renal artery Renal vein Segmental artery Interlobar vein Interlobar artery Arcuate vein Arcuate artery Cortical radiate vein Cortical radiate artery Peritubular capillaries or vasa recta Afferent arteriole Efferent arteriole Glomerulus (capillaries) Nephron-associated blood vessels (see Figure 25.8) Path of blood flow renal © 2016through Pearson Education, Inc. blood vessels Nephrons are the structural and functional units that form urine > 1 million per kidney Nephrons © 2016 Pearson Education, Inc. Two main parts Renal corpuscle: glomerulus & glomerular (Bowman’s) capsule Renal tubule Two parts of renal corpuscle: Renal Corpuscle © 2016 Pearson Education, Inc. 1. Glomerulus High pressure capillary bed composed of fenestrated endothelium Highly porous Allows for efficient filtrate formation Filtrate: plasma-derived fluid that renal tubules process to form urine 2. Glomerular capsule Also called Bowman’s capsule: cupshaped, hollow structure surrounding glomerulus Consists of two layers: Parietal layer: doesn’t play a role in forming filtrate Renal Corpuscle (cont.) Visceral layer : clings to glomerular capillaries; consists of branching epithelial cells (podocytes) Podocytes are octopus-like structures Filtration slits allow filtrate to pass into capsular space into glomerular capsular © 2016 Pearson Education, Inc. Renal cortex Renal medulla Glomerular capsule: parietal layer Renal pelvis Basement membrane Ureter Podocyte Kidney Fenestrated endothelium of the glomerulus Renal corpuscle Glomerular capsule Glomerulus Glomerular capsule: visceral layer Distal convoluted tubule Apical microvilli Mitochondria Highly infolded basolateral membrane Proximal convoluted tubule Proximal convoluted tubule cells Cortex Apical side Medulla Basolateral side Thick segment Thin segment Nephron loop Descending limb Ascending limb Distal convoluted tubule cells Collecting duct Nephron loop (thin-segment) cells Principal cell © 2016 Pearson Education, Inc. Collecting duct cells Intercalated cell Figure 25.6 Location and structure of nephrons. Renal tubule is about 3 cm (1.2 in.) long Consists of single layer of epithelial cells, but each region has its own unique histology and function Renal Tubule and Collecting Duct Three major parts: 1. Proximal convoluted tubule closest to renal corpuscle 2. Nephron loop 3. Distal convoluted tubule farthest from renal corpuscle Distal convoluted tubule drains into collecting duct © 2016 Pearson Education, Inc. Renal Tubule and Collecting Duct (cont.) © 2016 Pearson Education, Inc. 1. Proximal convoluted tubule (PCT) Cuboidal cells with dense microvilli that form brush border Increase surface area Also have large mitochondria Functions in reabsorption of water and solutes from filtrate and secreting substances into it Found only in renal cortex Renal Tubule and Collecting Duct (cont.) 2. Nephron loop Aka: Loop of Henle U-shaped structure consisting of two limbs: Descending limb Proximal part of descending limb is continuous with proximal tubule; thin Ascending limb Thick ascending limb © 2016 Pearson Education, Inc. Renal Tubule and Collecting Duct (cont.) © 2016 Pearson Education, Inc. 3. Distal convoluted tubule (DCT) Cuboidal cells with very few microvilli Function more in secretion than reabsorption Found only in cortex Renal Tubule and Collecting Duct (cont.) © 2016 Pearson Education, Inc. Collecting ducts – maintain water and Na+ balance Help maintain acid-base balance of blood Receive filtrate from many nephrons Run through the pyramids Ducts fuse together to deliver urine through papillae into minor calyces Renal cortex Renal medulla Glomerular capsule: parietal layer Renal pelvis Basement membrane Ureter Podocyte Kidney Fenestrated endothelium of the glomerulus Renal corpuscle Glomerular capsule Glomerulus Glomerular capsule: visceral layer Distal convoluted tubule Apical microvilli Mitochondria Highly infolded basolateral membrane Proximal convoluted tubule Proximal convoluted tubule cells Cortex Apical side Medulla Basolateral side Thick segment Thin segment Nephron loop Descending limb Ascending limb Distal convoluted tubule cells Collecting duct Nephron loop (thin-segment) cells Principal cell Figure 25.6 Location and structure ©of2016nephrons. Pearson Education, Inc. Collecting duct cells Intercalated cell Two major groups of nephrons: Cortical nephrons Make up 85% of nephrons Almost entirely in cortex Classes of Nephrons © 2016 Pearson Education, Inc. Juxtamedullary nephrons Long nephron loops deeply invade medulla Ascending limbs have thick and thin segments Important role in production of concentrated urine Nephron Capillary Beds © 2016 Pearson Education, Inc. Renal tubules are associated with two capillary beds: 1. Glomerulus (high pressure) 2. Peritubular capillaries (low pressure) Juxtamedullary nephrons are associated with Vasa recta Nephron Capillary Beds (cont.) 1. Glomerulus Capillaries are specialized for filtration Different from other capillary beds because they are fed and drained by arteriole Afferent arteriole enters glomerulus and leaves via efferent arteriole Efferent feed into peritubular capillaries or vasa recta Blood pressure in glomerulus high because: Afferent arterioles are larger in diameter than efferent arterioles Arterioles are high-resistance vessels Where waste products are filtered from the blood © 2016 Pearson Education, Inc. Nephron Capillary Beds (cont.) © 2016 Pearson Education, Inc. 2. Peritubular capillaries Low-pressure, porous capillaries adapted for absorption of water and solutes Arise from efferent arterioles Cling to adjacent renal tubules in cortex Empty into venules Nephron Capillary Beds (cont.) © 2016 Pearson Education, Inc. Vasa recta Long, thin-walled vessels in juxtamedullary nephrons Arise from efferent arterioles serving juxtamedullary nephrons Function in formation of concentrated urine Supply oxygen and nutrients to the tissue through which they pass Each nephron has one juxtaglomerular complex (JGC) which is part of the juxtaglomerular apparatus Juxtaglomerular Complex (JGC) Involves modified portions of: Distal portion of ascending limb of nephron loop Afferent arteriole Important in regulating rate of filtrate formation and blood pressure © 2016 Pearson Education, Inc. Juxtaglomerular Complex (JGC) (cont.) © 2016 Pearson Education, Inc. Three cell populations are seen in JGC: 1. Macula densa Tall, closely packed cells of ascending limb Contain chemoreceptors sense sodium chloride (NaCl) concentration in the filtrate 2. Granular cells (juxtaglomerular, or JG cells) Act as mechanoreceptors sense blood pressure in afferent arteriole Synthesize, store and secrete renin to control BP 3. Juxtaglomerular Complex (JGC) (cont.) © 2016 Pearson Education, Inc. Extraglomerular mesangial cells found between the afferent and efferent arterioles May pass signals between macula densa and granular cells play a role in renal autoregulation of blood flow to the kidney and regulation of blood pressure through the renin–angiotensin system. 180 L of fluid processed daily, but only 1.5 L of urine is formed Kidneys filter body’s entire plasma volume 60 times each day Physiology of Kidney Consume 20–25% of oxygen used by body at rest Filtrate (produced by glomerular filtration) is basically blood plasma except the proteins Urine Urine is produced from filtrate © 2016 Pearson Education, Inc.