LM 5.1: Histology of Lower Urinary Tract

Question 1

what are the components of the lower urinary tract?

Answer 1

1. renal pelvis
2. calyces
3. ureters
4. bladder
5. urethra

Question 2

what is the function of the lower urinary tract?

Answer 2

storage and excretion of urine at a convenient time

no further modification of the urine is possible after it leaves the renal medulla

Question 3

what type of cells line the lower urinary tract?

Answer 3

urotheleium aka transitional epithelium

urothelium is found only within the conducting passages of the urinary system, for which it is especially adapted

some of the epithelial cells have two nuclei which is not unusual for urothelium

Question 4

what is the pelvicalyceal system?

Answer 4

it’s the proximal end of the ureter

it’s the apex of the renal pyramid with the ducts of bellini that open into the minor calyx which then drains into the major calyces and renal pelvis

Question 5

what are the histologic layers of the ureter?

Answer 5

lumen
lamina propria
longitudinal SM
circular SM
collagenous adventitia

the urothelium which lines the lumen is visible as a band of highly cellular tissue – under the epithelium is the thin submucosa and the layers of smooth muscle lie outward from the submucosa

Question 6

what are the histologic layers of the bladder?

Answer 6

the organ is lined by three to five cell layers of urothelium that sits on a basement membrane under which is a thin fibrous submucosa

the bulk of the urinary bladder consists of smooth muscle fibers which are organized in inner and outer coats of longitudinally oriented fibers and a middle layer of circularly arranged smooth muscle bundles –> the 3 layers of smooth muscle are together called the detrusor muscle

the bladder is covered by adventitial connective tissue except for the upper surface which has a serosa of simple squamous epithelium on a layer of connective tissue

Question 7

what is the epithelium of the bladder like?

Answer 7

it is stratified, comprising three to six layers of cells, the number of layers being greatest when the epithelium is least distended

the cells of the basal layer are compact and cuboidal in form, while those of the intermediate layers are more columnar, with their nuclei orientated at right angles to the basement membrane

the surface cells are called umbrella cells and have unique features that allow them to maintain the impermeability of the epithelium to urine, even when at full stretch – this permeability barrier also prevents water from being drawn through the epithelium into hypertonic urine –> the surface outline has a characteristic scalloped appearance and the superficial cytoplasm is fuzzy, indistinct and more intensely stained than the rest of the cytoplasm

Question 8

what makes up the serosa of the bladder?

Answer 8

peripheral to the smooth muscles in the bladders an outer perimuscular connective tissue that is covered by a single layer of squamous epithelium

the connective tissue and squamous epithelium make up the serosa

Question 9

what are the 3 subdivisions of the male urethra? what types of cells line each?

Answer 9

1. prostatic

passes through the prostate and is lined with urothelium

2. membranous

courses through the urogenital diaphragm and is lined with pseudostratified epithelium

3. penile

associated with the corpus spongiosum and lined with either pseudostratified epithelium proximally or stratified squamous epithelium distally

Question 10

what type of cells line the female urethra?

Answer 10

urothelium in the portion near the bladder

it then changes to stratified squamous epithelium in the distal region of the urethra

then under the epithelium is the lamina propria which contains small mucous glands and numerous blood vessels – deep to that is the muscular which has 2 layers of smooth muscle

so it goes urothelium, lamina propria then smooth muscle

Question 11

what is the histologic hallmark of the ureter?

Answer 11

star-shaped lumen