URINARY SYSTEM ANATOMY BIO 139 ANATOMY PHYSIOLOGY II

URINARY SYSTEM ANATOMY BIO 139 ANATOMY & PHYSIOLOGY II

Urinary System Organs • Kidneys • Ureters • Urinary Bladder • Urethra

The Kidneys • Posterior abdominal cavity, slightly above waistline • Retroperitoneal • Right kidney lies below left kidney • Due to presence of liver • Supplied by renal artery and renal vein at the renal hilus • Functional unit is the nephron

Kidney Anatomy (Coronal) • Renal Hilus – indention of kidney • Renal Cortex – outermost layer, granular • Renal Medulla – striated, composed of renal pyramids (kidney tubules here) • Renal Pyramids • Minor Calyx – receive urine from renal pyramids • Major Calyx – receive urine from minor calyces • Renal Pelvis – funnel shaped portion of ureter; receives urine from major calyces • Ureter

Ureters • 25 cm long tubes • transport urine from the renal pelvis of the kidneys to the bladder through peristalsis

Urinary Bladder • Hollow, distensible organ that sits on the pelvic floor • Has a capacity that averages 700 -800 m. L • Urine exits through the urethra

Location of Male and Female Urinary Bladders Contains Transitional Epithelium • Bladder sits on top of the prostate in males

Male Urinary Bladder Longitudinal section and posterior view of male urinary bladder n. Why does prostatitis affect urinary output in men?

Urination (Micturition) • Urge to micturate (urinate) occurs when the bladder contains 150 -200 m. L • When volume increases, stretch receptors send signals to a micturition center in the spinal cord triggering a spinal reflex – the micturition reflex. • In early childhood, we learn to initiate and stop the reflex voluntarily. • This then encourages the bladder to expel urine through the external urethral orifice

Histology of Ureter and Urinary Bladder • Inner layer is transitional ET – Distensibility • Smooth muscular layer surrounds the ET Ureter

Urethra • Tube that connects the bladder to the outside of the body • Excretory function in males and females • Also has a reproductive function in males • Passage of sperm • 1 -2 inches long in females • About 7 inches in males

Male and Female Urethras 20 -35

Urinary Anatomy • Kidneys • Ureters • Urinary Bladder • Urethra • External urethral orifice

THE FUNCTIONAL UNIT OF THE KIDNEY IS THE NEPHRON. A nephron is the smallest unit that can make urine.

The Nephron • Functional unit of kidney • 1 million per kidney • Consist of 2 components: • Vascular Component • Tubular Component

Tubular Component of Nephron • Bowman’s Capsule - cortex • Surrounds a glomerulus (capillaries where blood is filtered, 1 st step in urine formation) • Bowman’s capsule receives the glomerular filtrate • Afferent arteriole leads to glomerulus • Efferent arteriole leads away from glomerulus

Tubular Component of Nephron • Proximal Convoluted Tubule (PCT) –cortex • Receives from Bowman’s capsule • Loop of Henle – dips down into the medulla • Descending • Ascending • Distal Convoluted Tubule (DCT) - cortex • Collecting Duct • DCT fluid drains into here and then to the renal pelvis and ureter • Not an actual nephron structure

Tubular Component of Nephron

Histology of Tubular Component • Bowman’s Capsule • Lined by simple squamous epithelium • Filtration • Kidney Tubules • Lined by simple cuboidal epithelium • Secretion and reabsorption

Vascular Component of Nephron • Afferent Arteriole - Branch of renal artery • Sends blood to glomerulus • Glomerulus - Tuft of capillaries in Bowman’s capsule • Filtration of plasma occurs here • Efferent Arteriole • Receives unfiltered blood from glomerulus • Peritubular Capillaries • Form from efferent arteriole • Surrounds tubular component • Eventually drains back into renal vein

Vascular Component of Nephron

Juxtaglomerular Apparatus • Formed where DCT comes in close contact with Bowman’s capsule, between the afferent and efferent arteriole • (see picture from H/O) • Important in regulating kidney function • JG apparatus releases the hormone renin

Nephron Types • Bowman’s capsule & PCT always in renal cortex • Loop of Henle dips into renal medulla • Juxtamedullary • Cortical Nephrons • BC near outer edge of cortex • Loop of Henle only dips slightly into medulla Nephrons • BC in cortex near medulla • Loop of Henle deep through entire length of medulla • Vasa Recta – branches of peritubular capillaries surrounding juxtamedullary nephrons

Nephron Types