Organic nutrients are completely reabsorbed except when renal threshold is reachedOther compounds missed by filtration process (ex: creatinine) are actively secreted into tubular fluid -Absorbed by the peritubular capillaries in the DCTUrinalysis:The analysis of a urine sampleAn important diagnostic tool 26-6: Urine is transported by the ureters, stored in the bladder, and eliminated through the urethra, aided by the micturition reflex The Urinary Tract Includes ureters, urinary bladder, and urethraTransports, storages, and eliminates urineStructures:18
Minor and major calyces, renal pelvis, ureters, urinary bladder, and proximal portion of urethraLined by transitional epithelium that undergoes cycles of distention and contractionThe Ureters A pair of muscular tubesExtend from kidneys (renal pelvis) to urinary bladderPeristaltic Contractions:Begin at renal pelvisSweep along ureter to force urine toward urinary bladderOccur every 30 secondsHistology of the Ureters:1.Mucosa-Inner layer -Contains transitional epithelium and lamina propria2.Muscular Layer-Middle layer-Contains longitudinal and circular bands of smooth muscle (involuntary contractions)3.Connective tissue layer-Outer layer-Continuous with fibrous renal capsule and peritoneum-Helps keep ureters in placeThe Urinary Bladder A hollow, muscular organFunctions as temporary reservoir for urine storageFull bladder can contain 1 liter of urineFeel need to urinate at 500 mLRugae:Folds in the lining of the bladder that allow it to expand19
Disappear as it fillsTheTrigone:A triangular area bounded by openings of ureters and the entrance to urethra Acts as a funnel and channels urine from bladder into urethraHistology of the Urinary Bladder:1.Mucosa:-Contains transitional epithelium and lamina propria-Mucosa in the bladder contains rugae except in the trigone it is smooth and thick2.Submucosa3.Muscularis Layer -Inner and outer layers of longitudinal smooth muscle with a circular layer in between-Form powerful detrusor muscleof urinary bladder -Contraction compresses urinary bladder and expels urineUrethra Extends from neck of urinary bladder to the exterior of the bodyThe Male Urethra:Extends from neck of urinary bladder to tip of penis (18–20 cm; 7-8 in.) Contains 3 parts-Prostatic urethra:passes through center of prostate gland-Membranous urethra:a short segment that penetrates the urogenital diaphragm20
-Spongy urethra(penile urethra): extends from urogenital diaphragm to external urethral orificeThe Female Urethra:Extends from the neck of the bladder to vestibuleVery short (3–5 cm; 1-2 in.)External urethral orifice is near anterior wall of vaginaExternal Urethral SphincterFound in both sexes A circular band of skeletal muscle (voluntary control)Where the urethra passes through urogenital diaphragmActs as a valve
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- Fall '19
- renal corpuscle, Nephron loop, nephrons, peritubular fluid