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Urinary System Anatomy
Terms in this set (47)
What are the layers of tissue supporting the kidney?
1. Renal fascia (false capsule)
-The anchoring outer layer of dense fibrous connective tissue
-Fascia of Gerota: anterior portion of the fascia
-Fascia of Zuckerkandl: posterior portion of the fascia
2. Perirenal fat capsule
-A fatty cushion
3. Fibrous capsule (true capsule)*
-Prevents spread of infection to kidney
What are the anatomical parts of the kidney?
1. Renal cortex: granular superficial region
2. Renal medulla
-Presents about 8 to 18 cone-shaped medullary (renal) pyramids separated by renal columns* (Bertin column)
3. Lobe: medullary pyramid and its surrounding cortical tissue
4. Papilla: tip of pyramid; releases urine into minor calyx
5. Renal pelvis
The funnel-shaped tube within the renal sinus
6. Major calyces
-The branching channels of the renal pelvis that collect urine from minor calyces
-Empty urine into the pelvis
-Urine flows from the pelvis to ureter
What is the nerve supply of the kidney?
Sympathetic fibers from the renal plexus
What is the arterial blood supply of the kidney?
What is the path of blood flow through renal blood vessels?
Aorta --> Renal A --> Segmental A --> Interlobar A --> Arcuate A --> Cortical radiate A/Interlobular A --> Afferent arteriole --> Glomerulus (capillaries) --> Efferent arteriole --> Peritubular capillaries and vasa recta --> Cortical radiate vein --> Arcuate vein --> Interlobular vein --> Renal vein --> IVC
What are some peculiarities of renal arteries?
1. Branches of renal arteries are end arteries
2. Renal blood passes through two sets of capillary plexuses
-A high pressure glomerular plexus
-A low pressure peritubular plexus
3. Blood circulating through the cortex is about 4-5 times more than medulla
4. Brodel's line: Pale blood-less line along the lateral border of the kidney where often surgical incisions are made to minimize bleeding
5. Independent vascular segments: five in each kidney
What is the brodel's line?
Pale, blood-less line along lateral border of kidney where often surgical incisions are made to minimize bleeding
What is the structural and functional unit that forms urine?
What are the two main parts of the nephron?
1. Glomerulus: a tuft of capillaries
2. Renal tubule: begins as cup-shaped glomerular (Bowman's) capsule surrounding the glomerulus
What makes up the renal corpuscle?
Glomerulus and glomerular capsule
What type of endothelium is found in the glomerulus?
Fenestrated glomerular endothelium: allows filtrate to pass from plasma into the glomerular capsule
What type of epithelium is found in the glomerular capsule?
1. Parietal layer: simple squamous epithelium
2. Visceral layer: branching epithelial podocytes
-Extensions terminate in foot processes that cling to basement membrane
-Filtration slits allow filtrate to pass into the capsular space
What type of cells are found in the proximal convoluted tubule (PCT)?
-Cuboidal cells with dense microvilli and large mitochondria
What is the function of the PCT?
Reabsorption and secretion
What part of the kidney are PCT confined to?
What constitutes the loop of henle and what cell types are found in each region?
1. Descending limb (thin segment)
-Simple squamous epithelium
-Freely permeable to water
2. Ascending limb (thick segment)
-Cuboidal to columnar cells
-Acts as counter-current osmotic multiplier
What is the function of the distal convoluted tubule?
Function more in secretion than reabsorption
What cell types are found in the distal convoluted tubule?
Cuboidal cells with very few microvilli
What part of the kidney is the distal convoluted tubule confined to?
Confined to cortex
Where do the collecting ducts receive filtrate from?
Receive filtrate from many nephrons
Fuse together to deliver urine through papillae into minor calyces
The collecting ducts fuse together to deliver urine through ___ into ___.
Papillae; minor calyces
What are the cell types found in the collecting ducts?
1. Intercalated cells
-Cuboidal cells with microvilli
-Function in maintaining the acid-base balance of the body
2. Principal cells
-Cuboidal cells without microvilli
-Help maintain the body's water and salt balance
What are the two general classes of nephrons?
1. Cortical nephrons—85% of nephrons; almost entirely in the cortex
2. Juxtamedullary nephrons
-Long loops of Henle deeply invade the medulla
-Extensive thin segments
-Important in the production of concentrated urine
What does the juxtaglomerular apparatus (JGA) regulate?
-Important in regulation of filtrate formation and blood pressure
-One per nephron
What does the juxtaglomerular apparatus (JGA) involve?
Involves modified portions of the:
-Distal convoluted tubule (macula densa)
-Afferent (sometimes efferent) arteriole (juxtaglomerular cells)
-Extraglomerular mesangial (lacis) cells
What types of cells compose the juxtoglomerular apparatus (JGA)?
1. Juxtaglomerular, or JG cells
-Enlarged, smooth muscle cells of arteriole
-Secretory granules contain renin
-Act as mechanoreceptors/baroreceptors that sense blood pressure
2. Macula densa
-Tall, closely packed cells of the DCT
-Act as chemoreceptors that sense NaCl content of filtrate
3. Extraglomerular mesangial (lacis) cells
-Polyhedral clusters of cells between the vascular pole of nephrons and the DCT
-Interconnected with gap junctions
-May pass signals between macula densa and JG cells
What is the filtration membrane?
Porous membrane between the blood and the capsular space
What does the filtration membrane consist of?
1. Fenestrated endothelium of the glomerular capillaries
2. Visceral membrane of the glomerular capsule (podocytes with foot processes and filtration slits)
3. Gel-like basement membrane (fused basal laminae of the two other layers)
What does the filtration membrane allow passage for?
Allows passage of water and solutes smaller than most plasma proteins:
-Fenestrations prevent filtration of blood cells
-Negatively charged basement membrane repels large anions such as plasma proteins
-Slit diaphragms also help to repel macromolecules
Ureters convey urine from ___ to ___.
Where do ureters enter?
-Enter the base of the bladder through the posterior wall
How is backflow of urine prevented in the ureters?
-As bladder pressure increases, distal ends of the ureters close, preventing backflow of urine
Are ureters intraperitoneal or retroperitoneal organs?
What are the three layers of the ureter wall?
1. Lining of transitional epithelium
2. Smooth muscle muscularis
-Contracts in response to stretch
3. Outer adventitia of fibrous connective tissue
What are the three constrictions that are present in the ureters?
1. Junction of renal pelvis and ureter
2. When ureter crosses the pelvic brim
3. At the point where the ureter pierces the bladder wall; it is the narrowest of all constrictions
What is the function of urinary bladder?
Muscular sac for temporary storage of urine
Where is the urinary bladder located?
Retroperitoneal, on pelvic floor posterior to pubic symphysis
-Males: prostate gland surrounds the neck inferiorly
-Females: anterior to the vagina and uterus
What borders the trigone area of the urinary bladder?
-Smooth triangular area outlined by the openings for the ureters and the urethra
What is the clinical significance of the trigone area of the urinary bladder?
Infections tend to persist in this region
What are the layers of the bladder wall?
-Transitional epithelial mucosa
-Thick detrusor muscle (three layers of smooth* muscle)
-Fibrous adventitia (peritoneum on superior surface only)
The urinary bladder collapses and expands/rises in response to what?
-Collapses when empty; rugae appear
-Expands and rises superiorly during filling without significant rise in internal pressure
What is the urethra?
What is the lining epithelium of the urethra?
-Mostly pseudostratified columnar epithelium, except
-Transitional epithelium near bladder
-Stratified squamous epithelium near external urethral orifice
What are the urethral sphincters?
1. Internal urethral sphincter
-Involuntary (smooth muscle) at bladder-urethra junction
-Contracts to open
2. External urethral sphincter
-Voluntary (skeletal) muscle surrounding the urethra as it passes through the pelvic floor
What are the characteristics of the female urethra?
Female urethra (3-4 cm):
-Tightly bound to the anterior vaginal wall
-External urethral orifice is anterior to the vaginal opening, posterior to the clitoris
What does the male urethra carry?
Semen and urine
What are the three named regions of the male urethra?
1. Prostatic urethra (2.5 cm): within prostate gland
2. Membranous urethra (2 cm): passes through the urogenital diaphragm
3. Spongy urethra (15 cm): passes through the penis and opens via the external urethral orifice
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