Urinary System15

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Urinary SystemChapter 15


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URINARY SYSTEM


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Ureters

Slender tubes that extend behind theperitoneum from the hilus of thekidney to enter the bladder

Transport urine to the bladder byperistaltic waves of smooth muscle

The ureterovesicular junction prevents

backflow of urine


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Bladder

Smooth, collapsible, muscular saclocated retroperitoneally in the pelvisthat has openings to the ureters and

urethra Serves as a reservoir for urine until it

is excreted from the body


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Urethra

Extends from the base of the bladderto the urinary meatus

Approximately 18 cm long in males

and 4 cm long in females Carries urine by peristalsis from the

bladder to the outside of the body


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Urinary meatus

External opening of the urethra


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Urine formation

Result of 3 processes:

Filtration, reabsorption and secretion

Glomerulus filters the blood which results

in a filtrate that includes waste productsand useful substances such as water,glucose, ions, and amino acids

The useful substances in the filtrate arereabsorbed into the blood by the proximaland distal convoluted tubules


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Urine formation

Tubular secretion is reabsorption inreverse. The waste products are secretedinto the filtrate in the tubules and excretedin the urine


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Micturition

Voiding

Under voluntary and involuntarycontrol

The urge to void normally occurswhen 150 to 300 ml urine hasaccumulated

The bladder normally contains nourine after voiding


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KIDNEYS


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External structures of the

kidney


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Hilum

Medial border of the kidney isindented by the hilum

Area where nerves, blood vessels,and the ureter enter the kidney

Gives the kidney its bean shapedappearance


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Internal structures of the

kidney


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Cortex

Outer portion containing theglomerules, tubules, and part of theloop of henle


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Medulla

Middle portion containing the Loop ofHenle and the collecting ducts Renal pyramids Collecting ducts with bases on the border

between the cortex and medulla

Separated by renal columns which areextensions of the cortex tissue

Papillae Apices of pyramids, which extend toward the

renal pelvis

Urine travels through the papillae to the renalpelvis


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Renal Pelvis

Inner portion where urine is collected Narrowed portion becomes the proximal

aspect of the ureter as it approaches the

hilum Minor and major calyces are recesses of

the pelvis that receive urine from papillaeof the collecting ducts


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Nephron

Functional unit of the kidney

Contains the glomerulus, tubules andcollecting ducts


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Nephron

Glomerulus Beginning of the nephron

Tuft of capillaries supplied by afferent

arterioles and drained by efferentarterioles within the Bowman capsule


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Nephron

Proximal tubule Is the convoluted portion with a border of

microvilli lining the lumen


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Nephron

Loop of Henle2 major portions:

Descending and ascending limbs

The descending loop narrows as it dipsfrom the cortex to the medulla


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Nephron

Distal tubule Passes between afferent and efferent

arterioles of glomerulus as it moves back

into the cortex


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Nephron

Collecting duct Passes through the cortex and medulla

receiving the terminal end of several

nephrons


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Renal circulation

The renal artery branches from theabdominal aorta

Subdivisions of interlobular arteries

carry blood into the corticomedullaryzone

Arcuate arteries form arches around

bases of pyramids Interlobular arteries, subdivisions of

the arcuate arteries, supply the renal

capsule


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Neurologic control

Renal innervation is supplied throughsympathetic and parasympatheticnerves. Adrenergic fibers also are in

proximity to juxtaglumerular apparatus


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Overall functions of the renalsystem Blood pressure regulation by renin

secretion

RBC production by erythropoietin

secretion Metabolism of vitamin D


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Major functions

Glomerulus Filtration

Proximal tubule 65% Na+ and H20 reabsorbed (ADH not

required) Glucose, K+, amino acids reabsorbed HC03- reabsorbed

H+ secreted Urea reabsorbed Filtrate leaves isotonic


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Major functions

Loop of Henle Countercurrent multiplying and exchange

mechanisms established between long,

thin loops of Henle of juxtamedullarynephrons and adjacent vasa recta

Filtrate leaves hypotonic


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Major functions

Distal tubule Na reabsorbed and K secreted in

presence of aldosterone opposite occurs

in absence of aldosterone Water reabsorbed with Na, ADH also

influences water reabsorption

Filtrate leaves hypotonic or isotonic


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Major functions

Collecting duct Na and K regulated by aldosterone

Acid base regulation

H- secretion HCo3 reabsorption

ADH determines final urine volume


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Fig. 18.6


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LAB AND DIAGNOSTICS


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Lab and Diagnostics

Urinalysis Involves assessment of urine color,

opacity, odor, specific gravity, osmolality

and pH Identifies presence of glucose, ketones,

proteins, RBC WBC, sediments, bacteria

Urine C/S

Requires midstream clean catch urinespecimen, detects infectivemicroorganisms


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Lab and Diagnostics

Blood analysis Plasma creatinine

Indication for renal function

BUN Analysis evaluates renal function

Blood urea nitrogen


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Lab and Diagnostics

Creatinine clearance Evaluates glomerular filtration rate GFR

Creatinine clearance increases as renal

function diminishes Intravenous and Retrograde

Pyelography

Provide info re: size, shape, position ofurinary tract structures


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DISORDERS


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Urinary retention Urine retained in the bladder

Urinary incontinence

Inability of the urinary sphincters to controlrelease of urine

Neurogenic Bladder dysfunction

Dysuncton of the bladder


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UTI Inflammation and infection of the the

urinary tract structures

Upper uti Pyelonephritis (kidney)

Lower uti

Ureteritis

Cystitis

urethritis


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Urolithiasis Renal calculi

Calculi in the bladder, ureter, or kidney

Acute Renal Failure /ARF Sudden, rapid, potenstially reversible

deterioration of renal function

Chronic Renal Failure /CRF End result of progressive irreversible loss

of functioning renal tissue

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Urinary System15