Exam 4 Review:  Chapter 25:  Urinary Tract & Bladder

mucosa - The specialized epithelial lining, derived from the primary germ layer endoderm, which produces a lubricating fluid containing the sticky protein mucin which traps microbes and dirt particles and protects any body structure which is continuous with the external environment except for the skin itself.

epithelium - Tissues with a high degree of cellularity and limited extracellular material, connected with specialized contact structures such as desmsomes, often organized in layers, which have no direct blood supply and which are derived from embryonic ectoderm and endoderm.

lamina propria - The supportive loose fibrous connective tissue layer found immediately beneath the mucosal epithelium and its basement membrane and the muscularis mucosae.

muscularis - The muscular coat or tunic of any hollow organ or tubular structure; its contractions, peristalsis, propel the contents of the organ elsewhere; it lies between the inner submucosa and the outer adventitia or serosa; in the urinary tract, it typically consists of an inner circular layer and an outer longitudinal layer, but, in the bladder, it also contains a middle oblique layer.

adventitia - A loose fibrous connective tissue outer covering of an organ or a blood vessel which is not within a body cavity and therefore is not covered by a serosal membrane; this outer covering simply extends outward until the next organ or structure is encountered.

serosa - A simple squamous lining found in the various ventral body cavities which lines the walls of the cavities and the organs contained therein and produces a watery serous fluid which lubricates the lining surfaces.

ureters - The pair of long (average length ~ 1 foot), narrow retroperitoneal ducts which transport urine by gravity and peristalsis from the renal pelvis of the kidney to the urinary bladder; their walls consist of an inner mucosa of transitional epithelium, a lamina propria of loose fibrous connective tissue, a muscularis with an inner circular layer and an outer longitudinal layer of smooth muscle innervated by the ANS, and an outer adventitia of loose fibrous connective tissue.

transitional epithelium - A special stratified epithelium in which the cells' shapes vary depending on the functional status of the organ.  In the human, transitional epithelium is only found in the urinary bladder and in adjacent portions of the ureters and urethra.  When the bladder is distended, the transitional cells appear more flattened (squamous); when the bladder is relaxed, the transitional cells appear more rounded (cuboidal).

urinary bladder - The small (700-800 mL capacity, smaller in females which have to accommodate the uterus behind it) distensible hollow retroperitoneal organ in the pelvic cavity which stores urine produced by the kidney and discharged to the external environment through the urethra in response to volunatary sensations and decisions followed by parasympathetic commands from the ANS; the openings to it are guarded by smooth muscle sphincters; its wall consists of an inner mucosa of transitional epithelium, a lamina propria of loose fibrous connective tissue, a thick muscularis with an inner circular layer, a middle oblique layer, and an outer longitudinal layer of smooth muscle innervated by the ANS, and an outer adventitia of loose fibrous connective tissue.

trigone - The smooth triangular area on the inner surface of the urinary bladder, defined by the internal openings of the ureters and urethra; it is purely an anatomical marker with no special function.

internal urethral orifice - The small opening in the inferior wall of the urinary bladder, forming the anterior point of the trigone, which is guarded by the internal urethral sphincter and leads to the urethra, the passageway through which urine is expelled from the bladder.

detrusor muscle - The entire thick smooth muscle of the wall of the urinary bladder, equivalent to the muscularis layer with an inner circular layer, a middle oblique layer, and an outer longitudinal layer of smooth muscle innervated by the ANS; its contraction expels urine from the bladder through the urethra to the external environment.

internal urethral sphincter - The thickened ring of smooth muscle, continuous with the detrusor muscle, which surrounds the internal urethral orifice in the wall of the urinary bladder; it is under the involuntary control of the ANS and remains tightly closed to prevent leakage except during episodes of urination when parasympathetic impulses cause it to relax; it is lined by a mucous membrane of stratified squamous epithelium with an underlying circular skeletal muscle sphincter.

external urethral sphincter - The small thickened ring of skeletal muscle around the urethra, which is located where the urethra penetrates the urogenital diaphragm (the double layer of pelvic fascia with its included muscle which is situated between the ischial and pubic rami); it is under voluntary control of the cerebral cortex and remains closed to prevent leakage except during episodes of urination when conscious impulses cause it to relax.

urethra - The  narrow duct which transport urine (and semen in males during ejaculation) from the urinary bladder to the external environment; its wall consists of an inner mucosa of pseudostratified columnar epithelium proximally and stratified squamous epithelium distally, a lamina propria of loose fibrous connective tissue containing spongy erectile tissue, a muscularis with thin circular and longitudinal layers of smooth muscle innervated by the ANS, and an outer adventitia of loose fibrous connective tissue; dispersed throughout the urethra are mucous urethral glands which secrete mucous into the urethral canal; it is short (1-2) inches) in females and exits in the cleft between the labia and between the clitoris and the vagina; it is longer in males (8-10 inches) and exits at the tip of the penis; in males, it is subdivided by location into three parts:  the prostatic urethra within the prostate gland, the membranous urethra which extends from the base of the prostate to the base of the penis, and the spongy urethra which extends through the penis.

[Can the candirú fish swim upstream into your urethra?]

external urethral orifice - The small opening to the external environment at the distal end of the urethra through which urine (and semen in males during ejaculation) is discharged to the outside; in females it is located in the cleft between the labia and between the clitoris and the vagina; in males it is located at the tip of the penis; in both sexes, it is lined by a mucous membrane of stratified squamous epithelium with an underlying circular skeletal muscle sphincter.

prostatic urethra - The first and proximal division of the urethra in males which lies within the prostate gland and receives the distal ends of both ductus deferens and the ducts of the prostate gland itself; its wall consists of four layers -- see definition of urethra above.

membranous urethra - The second and middle division of the urethra in males which lies between the prostate gland and the base of the penis and receives the ducts of the bulbourethral glands; its wall consists of four layers -- see definition of urethra above.

spongy urethra - The third and distal division of the urethra in males which lies between the base and the tip of the penis; its wall consists of four layers -- see definition of urethra above.

4. the three histological layers of the ureters and urinary bladder.
 

Histological Layer	Description
mucosa	Consists of:  (a) transitional epithelium which tolerates extensive stretching and (b) lamina propria,the supportive loose fibrous connective tissue layer found immediately beneath the mucosal epithelium and its basement membrane.
muscularis	In the ureter, iconsists of an inner circular layer and an outer longitudinal layer of smooth muscle, but, in the urinary bladder, it also contains a middle oblique layer.
externa	Consists of:  (a) an adventitia of loose fibrous connective tissue in locations where the ureters and urinary bladder are positioned retroperitoneally; or (b) a serosa, a simple squamous lining, in locations where the ureters and urinary bladder extend into the abdominopelvic cavity.