URINARY SYSTEM OVERVIEW P 1104 1120 STRUCTURES AND FUNCTIONS TO THE URINARY SYSTEM KIDNEYS Macrostructure o Two bean shaped organs located behind the peritoneum on either side of the vertebral o About 5 inches long surrounded by fat and connective tissue with an adrenal gland on column T12 L3 top of each one o Right kidney is lower than the left level of the 12th rib o Capsule covers the kidney acts as shock absorber o Hilus entry site of renal artery nerves exit site for renal vein ureter medial side o Parenchyma kidney tissue cortex outer layer medulla inner layer Microstructure o Nephron functional unit of the kidney Glomerulus Bowman s capsule Tubular system Proximal and distal convoluted tubule Loop of Henle Collecting tubules Blood supply Glomerular function o 1200 ml min 20 25 of cardiac output o Aorta hilus renal artery divide into two branches more branches afferent arteriole capillary network glomerulus efferent arteriole capillary network peritubular capillaries venous system renal vein inferior vena cava o Semipermeable membrane where blood is filtered and urine formation begins o Hydrostatic pressure of blood in glomerular capillaries filtered across membrane Bowman s capsule tubule makes ultrafiltrate similar composition to blood o Glomerular filtration rate GFR amount of blood filtered each minute Normal 125 ml min Tubular function o Reabsorbs essential materials and excretes nonessentials Reabsorption substance lumen of the tubules tubule cells capillaries Active and passive transport Proximal convoluted tubules reabsorbs 80 of electrolytes glucose amino acids small proteins Loop of Henle water sodium urea chloride ions and other solutes Secretion substance capillaries tubular cells lumen of the tubules Hydrogen ions and creatinine o Changes the composition of the glomerular filtrate Functions of Segments of Nephron table 45 1 o The basic function of the nephron is to cleanse blood plasma of unnecessary substances o Golmerulus selective filtration o Proximal Tubule Reabsorption of 80 of electrolytes and water reabsorption of all glucose and amino acids reabsorption of HCO3 secretion of H and creatinine o Loop of Henle Reabsorption of Na and Cl in ascending limb reabsorption of water in descending loop concentration of filtrate o Distal Tubule Secretion of K H ammonia reabsorption of water regulated by ADH reabsorption of HCO3 regulation of Ca and PO4 by parathyroid hormone regulation of Na and K by aldosterone o Collecting Duct Reabsorption of water ADH required ADH allows water to be reabsorbed into circulation by making the tubules and collecting ducts permeable to water Other functions of the kidneys o RBC production o Reduction of SVR and BP regulation Kidneys produce erythropoietin hormone secreted in response to hypoxia and decreased renal blood flow the kidney assumes if it is not getting blood the whole body must not be getting blood Kidney failure decrease erythropoietin production anemia Renin is produces and secreted by the kidneys increases BP Decreased renal perfusion decreased arterial blood pressure decreased ECF decreased serum Na concentration and increased urinary Na renin release Angiotensin I activation ACE converts to Angiotensin II aldosterone release Na and water retention increase in BP Kidneys synthesis prostaglandins PG vasodilation Na secretion counter angiotensin aldosterone lower BP by lowering SVR Renal failure decreases PG production leading to hypertension Ureters o Carry urine from the renal pelvis to the bladder Bladder Ureteropelvic junction UPJ where the ureter connects to the renal pelvis Very narrow and often the site of obstruction Sympathetic parasympathetic and vascular supply stimulation acute severe pain called renal colic Supposed to be one way when reflux occurs it leads to infection o A distensible able to ill at low pressures organ positioned behind the symphysis pubis and anterior to the vagina and rectum o Primary functions Serve as a reservoir for urine Eliminate waste products from the body o Normal output is 1500 ml day varies with intake o Urinate more during the day than at night because of ADH secretion during the day o 200 250 ml of urine will cause moderate distention and urge to empty your bladder o 400 600 ml can cause severe discomfort o 600 1000 ml is the maximum capacity Urethra o Small muscular tube that leads from the bladder neck to the external meatus o Primary function serve as a conduit for urine from the ladder to outside the body o Female is only 1 2 inches o Male 8 10 inches Prostatic urethra bladder neck to the urogenital diaphragm through prostate Membranous urethra through the urogenital diaphragm and is encircles by the rhabdosphincter Penile urethra beyond the urogenital diaphragm to the urinary meatus Urethrovesical unit o Bladder urethra and pelvic floor muscles allows for continence o Damaged by diabetes mellitus MS paraplegia and tetraplegia o Drugs effecting nerve transmission can also cause poor bladder function Gerontologic considerations o 20 30 decrease in size 30 90 years accelerated by atherosclerosis o 30 50 loss of glomeruli function by 70 o Decreased renal blood flow decreased GFR o Alteration in hormone levels AHD aldosterone and ANP inability to concentrate urine excrete water sodium potassium and acid o Bladder urethra and pelvic floor lose elasticity leading to incontinence o Kidney specific changes Decrease in renal tissues number of nephrons and blood vessles Decreased loop of Henle and tubules function Thickened basement membraneof Bowman s capsule and glomeruli o Assessment changes Less palpable Decrease creatinine clearance increased serum BUN and Creatinine Altered drug excretion nocturia less concentrated urine o Ureter bladder and urethra specific changes Decreased elasticity and muscle tone weakened sphincter Decreased capacity and sensory receptors Increase in unstable bladder contractions Prostatic enlargement thin dry vaginal tissue Retention of urine and stress incontinence Frequency urgency nocturia overflow incontinence overactive bladder dyuria ASSESSMENT OF THE URINARY SYSTEM Subjective data o Past health history Renal or urologic diseases or problems Hypertension DM gout metabolic problems connective tissue disorders skin or upper airway infections strept lupus TB viral hepatitis neurologic conditions and trauma Cancer frequent infections BPH and calculi Any past surgeries that effected urination o Medications Many drugs can be nephrotoxic or change