Urinary Tract Structure

Compare and contrast the gross anatomy of the urinary tract, including the anatomical relationships of ureters, bladder and urethra, in males and females
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In both males and females, the minor calyces collect urine from the medullary pyramids and combine to form major calyces. From here, they empty into the renal pelvis, which narrows to form the ureter. The ureter then connects to the bladder obliquely such that a valve is formed to prevent backflow.

- In women, the ureters are crossed by the uterine arteries (lateral to the cervix).
The bladder contains a smooth traingular area called the trigone in between the ureteral openings. This allows the bladder to empty fully during contraction of the detrusor.

- In women, the bladder is anterior to the cervix and vagina.

- In men, the bladder is anterior to the seminal vesicles and rectum.
The bladder contains a transitional epithelium supported by lamina propria. There may be a muscularis mucosae in the bladder, composed of fine smooth muscle strands. The muscularis propria composes the detrusor muscle, and at the neck of the bladder, the involuntary internal sphincter. The outer layer is mostly adventitia, but has some serosa in areas.
Image: Describe the histology of renal calyces, renal pelvis, ureters, *bladder* and urethra, including the distribution of transitional epithelium in males and females
The urethra contains transitional epithelium near the bladder (prostatic urethra in men). The epithelium transitions to pseudostratified columnar, then to stratified squamous in the distal length. In both men and women, periurethral glands surround the urethra.

Transitional epithelium lines the calyces, renal pelvis, ureters, urinary bladder, and proximal urethra (in both males and females). In males, the proximal urethra is the prostatic urethra.
Image: Describe the histology of renal calyces, renal pelvis, ureters, bladder and *urethra*, including the distribution of transitional epithelium in males and females
The renal pelvis is the funnel which combines all of the major calyces and narrows the tube to connect to the ureter.

The calyx is the part of the urinary tract that collects urine from the medullary pyramid and delivers it to the ureter.

The ureteropelvic junction is the point where the renal pelvis joins to the ureter; there is a narrowing at this junction. (Constriction point)

The ureter is the tube that delivers urine to the bladder from the hilum of the kidney.

The ureterovesicle junction is where the ureter connects to the bladder; there is a narrowing at this junction. (constriction point)

The urethra is the tube that allows urine to be emptied from the bladder to outside of the body.
Summarize neural regulation of micturition as presented in the Nervous System BlockStorage mode. The bladder spends most of its time in storage mode, maintained in that state (oddly enough) by sympathetic inputs. Sympathetic preganglionics from T11-L2 project to one of the prevertebral ganglia (the inferior mesenteric ganglion). Postganglionics then promote relaxation of the detrusor by releasing norepinephrine on postganglionic parasympathetic ganglion cells in and near the bladder wall and on the detrusor itself (the latter a relatively minor effect). At the same time, urethral resistance is maintained by tonic contraction of the external sphincter, innervated not by autonomic neurons, but rather by lower motor neurons from a small cluster in S2 (which also innervates the external anal sphincter). The intrinsic elasticity and some smooth muscle of the ureter also contribute to urethral resistance. The relaxed detrusor allows the bladder to fill with relatively little rise in intravesical (= inside the bladder) pressure. Elimination mode. The bladder periodically enters elimination mode, in which the parasympathetics take over and storage conditions are reversed. Sympathetic inhibition of postganglionic parasympathetics ceases. This allows S2-S4 parasympathetics to cause detrusor contraction, raising intravesical pressure. At the same time, urethral resistance falls because lower motor neurons in S2 are inhibited and sympathetic activation of the internal sphincter stops.