Chapter 23 (Urinary System) PDF

CHAPTER 24 The Urinary System Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation, Educatio, Inc. Inc. The Urinary System Kidneys Maintain the chemical consistency of the blood Filter many liters of fluid from blood Send toxins, metabolic wastes, and excess water out of the body Mai...

CHAPTER 24 The Urinary System Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation, Educatio, Inc. Inc. The Urinary System Kidneys Maintain the chemical consistency of the blood Filter many liters of fluid from blood Send toxins, metabolic wastes, and excess water out of the body Main waste products Urea, uric acid, and creatinine Organs of the Urinary System Kidneys Ureters Urinary bladder Urethra Hepatic veins (cut) Esophagus (cut) Inferior vena cava Adrenal gland Aorta Renal artery Renal hilum Renal vein Kidney Iliac crest Ureter Rectum (cut) Uterus Urinary bladder Urethra (a) Location and External Anatomy of Kidneys Located retroperitoneally Lateral to T12–L3 vertebrae Average kidney – 12 cm tall, 6 cm wide, 3 cm thick Hilus – on concave surface Vessels and nerves enter and exit Renal capsule surrounds the kidney Relationship of the Kidneys to Vertebra and Ribs 12th rib (b) Position of the Kidneys with in the Posterior Abdominal Wall Anterior Peritoneum Peritoneal cavity (organs removed) Renal vein Supportive tissue layers Renal fascia anterior posterior Renal artery Body of vertebra L2 Body wall (a) Inferior vena cava Aorta Perirenal fat capsule Fibrous capsule Posterior Jejunum Duodenum Liver Inferior vena cava Aorta Right kidney Vertebra L1 (c) Left renal vein Left kidney Erector spinae muscle in posterior abdominal wall Internal Gross Anatomy of the Kidneys Frontal section through the kidney Renal cortex, renal pyramids, and renal pelvis Gross vasculature Internal Anatomy of the Kidneys Nerve supply – renal plexus A network of autonomic fibers An offshoot of the celiac plexus Microscopic Anatomy of the Kidneys Uriniferous tubules Composed of: Nephron – renal corpuscle plus renal tubules Collecting duct – involved in concentrating urine Uriniferous Tubule Mechanisms of Urine Production Filtration filtrate of blood leaves kidney capillaries Reabsorption most nutrients, water, and essential ions reclaimed Secretion active process of removing undesirable molecules Basic Kidney Functions Afferent arteriole Glomerular capillaries Efferent arteriole Cortical radiate artery Glomerular capsule Rest of renal tubule containing filtrate Peritubular capillary Three major renal processes PLAY Urine Formation Glomerular filtration Tubular resorption Tubular secretion To cortical radiate vein Urine The Nephron Renal corpuscle – glomerulus and glomerular capsule Glomerulus – tuft of capillaries Capillaries are fenestrated Glomerular (Bowman’s) capsule Parietal layer – simple squamous epithelium Visceral layer – consists of podocytes Renal Corpuscle and the Filtration Membrane Efferent arteriole Glomerular capsular space Afferent arteriole Glomerular capillary covered by podocytecontaining visceral layer of glomerular capsule (a) Renal corpuscle Cytoplasmic extensions of podocytes Parietal layer of glomerular capsule Proximal convoluted tubule Filtration slits Podocyte cell body Fenestrations (pores) Glomerular capillary endothelium Foot processes (podocyte covering of podocyte and basement membrane removed) (b) Glomerular capillary surrounded by podocytes Renal Corpuscle and the Filtration Membrane Capillary Filtration membrane Capillary endothelium Basement membrane Foot processes of podocyte of glomerular capsule Filtration slit Plasma Filtrate in capsular space Slit diaphragm Foot Fenestration processes (pore) of podocyte (d) Three parts of the filtration membrane Tubular Section of Nephron Filtrate proceeds to renal tubules from glomerulus Proximal convoluted tubule Loop of Henle Descending limb Thin segment Thick segment Distal convoluted tubule Tubular Section of Nephron Classes of Nephron Cortical nephrons – 85% of nephrons Juxtamedullary nephrons – 15% of nephrons Collecting Tubules (Collecting ducts) Collecting tubules – receive urine from distal convoluted tubules Microscopic Blood Vessels Nephrons associated with two types of capillary beds Glomerulus Fed by afferent arterioles Drained by efferent arterioles Peritubular capillaries Arise from efferent arterioles Low-pressure, porous capillaries Absorb solutes Microscopic Blood Vessels Vasa recta – thin-walled looping vessels PLAY Part of the kidney’s urine-concentrating mechanism Urinary System Overview Summary of Blood Vessels Supplying 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 Afferent arteriole Peritubular capillaries and vasa recta Efferent arteriole Glomerulus (capillaries) Nephron-associated blood vessels (see Figure 24.9) (b) Path of blood flow through renal blood vessels Microscopic Anatomy of the Kidney Juxtaglomerular apparatus Functions in the regulation of blood pressure Juxtaglomerular cells Secrete renin Macula densa – portion of distal convoluted tubule Tall, closely packed epithelial cells Act as chemoreceptors Juxtaglomerular Apparatus Glomerular capsule Glomerulus Efferent arteriole Parietal layer of glomerular capsule Capsular space Afferent arteriole Foot processes of podocytes Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Efferent arteriole Juxtaglomerular apparatus Macula densa cells of the ascending limb of nephron loop Extraglomerular mesangial cells Granular cells Afferent arteriole Juxtaglomerular apparatus Lumens of glomerular capillaries Endothelial cell of glomerular capillary Mesangial cells between capillaries Renal corpuscle Ureters Carry urine from the kidneys to the urinary bladder Oblique entry into bladder prevents backflow of urine Histology of ureter Mucosa – transitional epithelium Muscularis – two layers Inner longitudinal layer Outer circular layer Adventitia – typical connective tissue Urinary Bladder A collapsible muscular sac Stores and expels urine Full bladder – spherical Expands into the abdominal cavity Empty bladder – lies entirely within the pelvis Urinary Bladder Prostate gland – in males Lies directly inferior to the bladder Surrounds the urethra Structure of the Urinary Bladder and Urethra Peritoneum Ureter Rugae Detrusor muscle Adventitia Ureteric orifices Trigone of bladder Bladder neck Internal urethral sphincter Prostate Prostatic urethra Membranous urethra External urethral sphincter Urogenital diaphragm Spongy urethra Erectile tissue of penis (a) Male. The long male urethra has three regions: prostatic, membranous, and spongy. External urethral orifice Structure of the Urinary Bladder and Urethra Peritoneum Ureter Rugae Detrusor muscle Ureteric orifices Bladder neck Internal urethral sphincter Trigone External urethral sphincter Urogenital diaphragm Urethra (b) Female External urethral orifice Urethra Epithelium Transitional epithelium – near the bladder Stratified and pseudostratified columnar – mid urethra Stratified squamous epithelium – near the distal end Internal urethral sphincter – involuntary smooth muscle External urethral sphincter – voluntarily inhibits urination Urethra In females – length of 3–4 cm In males – 20 cm in length – three named regions Prostatic urethra – passes through the prostate gland Membranous urethra – through the urogenital diaphragm Spongy (penile) urethra – passes through the length of the penis Micturition Pons Pontine micturition center Lower thoracic or upper lumbar spinal cord 4 Bladder 2 (–) Inferior hypogastric ganglion Hypogastric nerve (+) Pelvic 1 nerves Sacral spinal cord (+) (–) Internal urethral sphincter 3 Pelvic splanchnic nerves 5 External urethral sphincter 1 Visceral afferent impulses from stretch receptors in the bladder wall are carried to the spinal cord and then, via ascending tracts, to the pontine micturition center. 2 Integration in pontine micturition center initiates the micturition response. Descending pathways carry impulses to motor neurons in the spinal cord. 3 Parasympathetic efferents stimulate contraction of the detrusor muscle and open the internal urethral sphincter. 4 Sympathetic efferents to the bladder are inhibited. 5 Somatic motor efferents to the external urethral sphincter are inhibited; the sphincter relaxes. Urine passes through the urethra; the bladder is emptied. Visceral afferent Sympathetic Somatic efferent Parasympathetic Interneuron