Kidneys and Urinary System - LO 5

5. List the structures of the excretory pathway. 

Distal convoluted tubules of nephrons → collecting ducts → Minor calices (@ renal papillae)* → Major calices* → Renal pelvis* → Ureter* → Urinary bladder* → Urethra*

*Grossly visible

Minor calices

There are typically 3-4  minor calices for each major calyx.

Each minor calyx has a renal papilla, an indentation of the apex of the renal pyramid, where urine is excreted.

Major calices

There are typically 2-3 major calices in a kidney, which receive urine from the minor calices, and drains into the renal pelvis.

Renal pelvis

The renal pelvis is the superior expansion of the ureter which receives urine from the major calices.

Ureters

The ureter is a muscular duct that connects the kidney to the bladder and transmits urine.

There are 3 parts of the ureter:

• Abdominal part: crossed by gonadal vessels and crosses over bifurcation of the common iliac a.

  • Retroperitoneal

• Pelvic part: traverses the pelvic cavity retro- and then subperitoneally

• Intramural part: contained within the wall of the base of the urinary bladder

Urinary bladder

The urinary bladder is a distensible, urine-storing, subperitoneal organ.

The apex of the urinary bladder is supero-posterior to the superior portion of the pubic symphysis. 

Inferior from the apex is the anterior surface of the bladder, which lies adjacent to the pubic symphysis. 

Posterior to the apex is the superior surface of the bladder. The superior surface is covered by peritoneum. 

The base/fundus of the bladder is the posterior-most wall (opposite the apex). It may be closely associated with either the vagina (women), or the rectum (men). 

The wall of the base contains the intramural parts of the ureters, which open into the lumen of the bladder via ureteric orifices. 

The neck is the inferior-most portion of the bladder, and contains the internal urethral meatus. In males, the neck of the bladder is superiorly adjacent to the prostate gland, and in females, the neck is very closely associated with vagina. The neck is held in place anteriorly and anterolaterally by the pubovesical ligament (women) / puboprostatic ligament (men). 

The triangular space proscribed by the ureteric orifices and the internal urethral meatus is called the trigone.

Urethra

The urinary bladder voids urine to the external environment through the urethra. The urethra is substantially sexually polymorphic.

The typical female urethra begins at the internal urethral meatus, travels anteroinferiorly between the pubic symphysis and vagina, and terminates in the external urethral meatus. The external urethral meatus is typically found in the vestibule of the vagina between the glans clitoris and the opening of the vagina.

The typical male urethra is tripartite, its parts including:

• • intramural (preprostatic) part: neck of bladder to prostate

  • prostatic part: begins at the internal urethral meatus, traverses the prostate gland, where it receives secretions of the prostate as well as from the ejaculatory ducts (this is the point of entry of semen into the urethra)

  • membranous part: traverses the pelvic diaphragm

  • spongy/penile part: traverses the corpus spongiosum of the penis; ends in the external urethral meatus on the distal ventral portion of the glans penis.