Download - Filtration Barrier
Filtration Barrier
• Lamina rara externa
• Lamina densa• Lamina rara
interna
Glomerular Filtration
• Filtering of blood in the renal corpuscle
• Glomerular filtrate – fluid that seeps from the glomerular capillaries into the Bowman’s space
Renal Tubule
• Proximal convoluted tubule• Loop of Henle– Thick descending limb– Thin descending and ascending limbs– Thick ascending limb
• Distal convoluted tubule• Collecting tubules and ducts
Renal Tubule
Proximal Convoluted Tubule
Loop of Henle Distal Convoluted Tubule
Epithelium Simple cuboidal Thick descending limb: simple cuboidalThin limb: simple squamousThick ascending: simple cuboidal
Simple cuboidal
Function Reabsorb 70-80% of H2O and sodiumReabsorb glucose, AA, chloride
H2O reabsorption except: Thick ascending: impermeable to water, NaCl reabsorption
Secretes potassium and hydrogenSmall H2O and Na reabsorption
Types of Nephrons
• Short-looped (cortical) - majority– Renal corpuscles located in outer portions of
cortex– Short Henle’s loop (no thin ascending limb)
• Long-looped (juxtamedullary)– Renal corpuscles are near the corticomedullary
junction– Long Henle’s loop (go deep into medulla, have
thin ascending limb)
Juxtaglomerular Apparatus
• Microscopic structure in the kidney which regulates the function of each nephron
• Found between the vascular pole of the renal corpuscle and the returning DCT of the same nephron
• Function: regulates filtrate formation and systemic BP
Juxtaglomerular Apparatus
• 3 cells:– Juxtaglomerular cells– Mesangial cells– Macula densa cells - area of closely packed
specialized columnar cells lining the wall of the distal tubule• Sense changes in solute concentration and flow rate of
filtrate
BLADDER AND URINARY PASSAGES
• Renal calyces• Renal pelvis• Ureter• Urinary bladder
• Same histologic structure• Walls of ureter becoming gradually thicker as
proximity to the bladder increases
BLADDER AND URINARY PASSAGES
• Function:– Store the urine
formed in the kidneys and conduct it to the exterior
BLADDER AND URINARY PASSAGES
• Mucosa:– Transitional epithelium– Lamina propria: loose to dense CT
• Muscular layer – OCIL • Adventitia or serosa– Only upper part of bladder covered by peritoneum
URETHRA
• Terminal portion of the urinary system• Function:– Passageway for urine– Males: passageway for urine and sperms
Male Urethra
• 20 cm in length• 3 segments:– Prostatic urethra– Membranous urethra– Spongy urethra (penile, cavernous)
• Terminates in the external urethral orifice (meatus)
Male Urethra
Prostatic Membranous Penile
Length and location
3-4 cmTraverses the prostate gland
1 cm Traverses the sphincter urethrae muscle
15 cm Traverses the penis
Lining epithelium
Transitional Pseudostratified columnar
Pseudostratified columnarEUM: Stratified squamous non-keratinized
Glands Urethral glands of Littre (lamina propria)
Bulbourethral glands of Cowper (embedded in the sphincter urethrae muscle)
Bulbourethral glands of Cowper
Female Urethra
• Shorter (4 cm)• Closely attached to
anterior wall of vagina
• Opens directly in front of the vaginal opening on the vestibule of the external genitalia
Female Urethra
Female Urethra
• Mucosa– Transitional → stratified squamous non-
keratinized– Lamina propria: loose CT, mucus-secreting
urethral glands
• Muscular layer: circularly arranged smooth muscle cells
Female Urethra
• Distal segment is surrounded by circularly-arranged striated (voluntary) muscle fibers (sphincter urethrae muscle – external sphincter)