Chapter 26 Urinary System 1 1

Organs of the Urinary System Kidneys (2) Ureters (2) Urinary bladder (1) Urethra (1)

Functions of the Kidney Filters blood plasma-removes waste products, toxins, H+, drugs, hormones, water, urea Produces urine Regulate blood volume and pressure through secretions of: Enzyme renin controls blood pressure and electrolyte balance Hormone erythropoietin stimulates production of RBC cells Regulate the osmolarity of the body fluids Collaborate with lungs to regulate/buffer PCO2 and acid-base balance (pH) - loss of hydrogen ions and bicarbonate ions in urine Regulates plasma ion concentrations Sodium, potassium, and chloride ions controlling urine loss Calcium ion levels through synthesis of calcitriol-Vitamin D helps to regulate calcium homeostasis Gluconeogenesis from amino acids in extreme starvation 3

KIDNEYS 3 layers of CT tissue: Renal fascia: dense, fibrous outer layer binds kidney to abdominal wall Perirenal fat capsule: thick layer of adipose tissue cushions/holds in place Renal/fibrous capsule: layer of collagen fibers encloses the kidney. On top of kidney

Anatomy of the Kidney Cortex: outer layer of the kidney Medulla: middle layer composed pyramids and renal columns. Pyramids: collecting ducts/ loops of Henle, lower portion of the nephrons. Renal columns –extension of cortex Renal sinus: internal cavity within kidney; stabilizes positions of ureter, renal blood vessels, and nerves The papilla of each pyramid projects into the calyx. Calyces collect the urine released from the papillae and allow it to drain into an enlarged collection minor calyx – drains papilla major calyces – drains minor calyx renal pelvis -connected to ureter, which drains kidney Lobe of the kidney = 1 pyramid and overlying cortex; produces urine Hilum - entry for renal artery and renal nerves; exit for renal vein and ureter

The Nephron Functional unit of the kidney Renal corpuscle Glomerular capsule (Bowman’s capsule) Capillary network (glomerulus) Renal tubule Begins at renal corpuscle Located in cortex Proximal convoluted tubule (PCT) Loop of Henle U-shaped tube Extends partially into medulla Distal convoluted tubule (DCT) http://dc220.4shared.com/doc/HzeJcp5Q/preview_html_m471d3343.jpg

Blood Access to the Nephron The nephron receives blood from the afferent arteriole. The afferent arteriole supplies the glomerulus From the glomerulus blood flows into the efferent arteriole. The efferent arteriole flows into more capillaries, the peritubular capillaries, and, in juxtamedullary nephrons, the vasa recta. Peritubular capillaries and vasa recta lead to the venous drainage of the kidney. http://resources.med.fsu.edu/gsm/hp/program/section7/7ch03/7ch03img/7c03p10.jpg

Types of Nephrons Cortical nephrons 85% of all nephrons short nephron loops efferent arterioles branch into peritubular capillaries around PCT and DCT Juxtamedullary nephrons 15% of all nephrons very long nephron loops, maintain salinity gradient in the medulla and helps conserve water efferent arterioles branch into vasa recta around long nephron loop

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Renal Corpuscle Bowman’s capsule and glomerulus. Filtration unit of the nephron The outer (parietal) layer of Bowman's capsule consists of simple squamous epithelial cells with tight junctions and serves to contain the filtrate in the capsular space. The visceral epithelium of the Bowman's capsule consists of large cells called podocytes with complex processes or “feet” (pedicels) that wrap around specialized dense layer of glomerular capillaries to produce openings called filtration slits. The glomerulus is a condensed mass of capillaries which allows substances to escape by filtration.

synthesize, store, and secrete the enzyme renin Macula densa Cells epithelial cells of DCT Increase/decrease GFR by dilating or constricting the afferent arteriole Juxtaglomerular cells (granular) (JG) - modified smooth muscle cells in the walls of the afferent arteriole synthesize, store, and secrete the enzyme renin

pedicels

Ureter, Urinary Bladder, Micturition Reflex From the collecting ducts urine passes through the papillary ducts, the minor calyces, the major calyces, and the renal pelvis. The ureters are connected to the renal pelvis and carry urine to the urinary bladder. Ureters have TWO layers of smooth muscle: a longitudinal layer (outermost) and a circular layer (innermost). Urine is stored in the bladder Micturition (urination) occurs when sphincters of the urethra open to allow urine to flow out of the body. https://userscontent2.emaze.com/images/6e47ac57-22f1-43d7-ae64-89d105d84e32/ddd64c72-96e8-45f7-bac3-bd421b1123e8.jpg

http://high-blood-pressure-symptoms. com/wp-content/uploads/2011/12/17 http://high-blood-pressure-symptoms.com/wp-content/uploads/2011/12/17.bladder-infection-symptoms.jpg Ureters

Urinary Bladder Hollow muscular elastic organ stores urine in lower pelvic cavity. Contains. 3 layers: Mucosa transitional epithelium that can be stretched Epithelial secretes mucus Rugae allow bladder to expand Detrusor muscle = 2 layers of longitudinal smooth muscle and a middle circular layer. Can spasm during infection The internal urethral sphincter (involuntary) The external urethral sphincter (voluntary) The fibrous adventitia covers the bladder attaches to the visceral peritoneum. Opening of the two ureters and urethra mark a smooth surfaced triangular area called the TRIGONE on the bladder floor.

Male and Female Urethra Urethra is a tubular organ that allows for drainage of the urinary bladder. Females - short, external orifice is located within the vulva. Males subdivided into 3 regions: prostatic, membranous, and spongy

Disorders Urinary Tract Infection (UTI) cystitis – infection of the urinary bladder common in females due to short urethra frequently triggered by sexual intercourse can spread up the ureter causing pyelitis pyelitis – infection of the renal pelvis from blood borne agents such as bacteria. Can also arise from cystitis. pyelonephritis –kidney infection Generally results from blood-borne bacteria or virus Escherichia coli (e-coli) is often the bacteria associated with infection Kidney stones form in renal pelvis hard granule of calcium phosphate, calcium oxalate, uric acid, or a magnesium salt 23-22