UTWB Lesson 41: Basic Organs and Structures in the Abdominal and Pelvic Cavity

What is the ureter?

Muscular tube that transports urine from the renal pelvis in most species (major calices in cow) to the urinary bladder

What is the ureter divided into?

Abdominal part and pelvis part

Where is the abdominal part of the ureter?

Runs sagittally along the abdominal roof and laterally to the aorta or vena cava

Where is the pelvic part of the ureter?

Turns medially to enter the broad ligaments in females and the genital fold in males 

What is the structure of the ureter in relation to the bladder?

Opens obliquely on the dorsal surface of the neck of the bladder

Penetrates the bladder wall very obliquely, thereby guarding against reflux of urine into the ureter when the bladder fills up

Where is the ureter located in males vs females?

Males- ureter crosses above the deferent duct toward the end of its course

Females- Inclusion of ureter within the broad ligaments places it at some risk in spays

The distensible nature of the bladder creates what?

Variability in size, position, and relationships

What is located dorsally and ventrally to the bladder?

Dorsal- uterus and vagina within the broad ligament in the female, deferent duct and in the vesicular glands within the genital fold in the male

Ventral- Contacts the pelvic and abdominal floor 

What does the bladder look like when fully contracted?

Small and globular with thick walls and negligible lumen

What does the bladder look like when distended?

Occupies the floor of the abdominal/peritoneal cavity, but the neck remains fixes within the pelvis through its continuity with the urethra

What is the detrusor muscle?

Thick-walled muscular layer of the bladder

What are the 3 parts of the bladder?

1. Cranial Vertex (apex)

2. Intermediate Body

3. Caudal Neck 

Where does the neck of the bladder continue onto?

Internal urethral orifice at the junction with the urethra 

Ligaments of the bladder

Bladder is supported by double layers of peritoneum which reflect from the bladder wall onto the body wall

Paired lateral ligaments

Bilateral which attach the lateral surface of the bladder to lateral walls of the pelvic cavity

Median ligament

Extends from the ventral surface of the bladder dot the abdominal/pelvic floor

What is the urachus?

In the fetus, the median ligament contains the urachus (connects the bladder to the umbilicus) while the paired lateral ligaments convey the umbilical arteries to the umbilicus 

What happens to the urachus and the umbilical arteries?

They rupture at birth

What happens to the urachus and umbilical arteries after they rupture?

The remnant of the urachus forms a scar at the vertex, while the umbilical arteries are transformed to round ligaments which are found on the free edge of the lateral ligaments

What are rugae?

Folded mucosa to form mucosal elevations in the empty bladder

What happens to the rugae when the bladder distends? 

The folds disappear except at 2 positions which occur from the ureteral openings to the neck of the bladder 

What do the remaining folds create?

Unite to form the urethral crest to continue the urethra

What is the trigone?

The triangular area bounded by these folds and the opening of the urethra

This area is more sensitive to stimuli

What is the trigone cont.

Dorsal triangular area located within the lines connecting the ureteral openings in the bladder and the urethral exit of the bladder

Where does the bladder receive its main blood from?

Caudal vesical artery

Where does the caudal vesicle artery come from?

Internal iliac artery —> Internal pudendal artery —> Vaginal artery —> Caudal Vesical artery (Females)

Internal iliac artery —> Internal pudendal artery —> Prostatic artery —> Caudal Vesical artery (Males)

What artery also supplies blood to the bladder but is not the main artery?

Umbilical artery

What types of nerve innervation does the bladder receive?

Somatic, Sympathetic, and Parasympathetic

What nerve provides sympathetic innervation to the bladder?

Hypogastric nerve 

What nerve provides parasympathetic innervation to the bladder?

Pelvic nerve

Pudendal nerve

Where does sympathetic innervation enact?

Smooth muscle sphincter

Where does parasympathetic innervation enact?

Supplies the detrusor muscle

This route also provides sensory information via the pudendal nerve, as well as somatic innervation to the urethralis muscle

What are the gross features of the female urethra?

The female urethra extends caudally on the pelvic floor ventral to the reproductive tract

Passes obliquely through the wall of the vagina and opens at the external urethral opening/orifice 

Where does the female urethra open?

Occurs at the junction between the vagina and the vestibule on the urethral tubercle

What is the sole function of the urethra in females?

Convey urine

Gross features of the male urethra

Extends from an internal opening at the bladder neck to an external opening at the end of the penis

What is the male urethra responsible for?

Passage of urine, semen, and sperm 

What is the male urethra divided into?

Pelvic part

Penile part (spongy)

What is the urethra surrounded by in the male?

Corpus spongiosum (spongy)

Where does the urethra terminate in the male?

As the urethral process in horses and ruminants

What is the os penis and what does it form?

Bony structure at the distal end of the glans penis that forms the urethral groove which fits the penile urethra 

What is the colliculus seminalis?

Enlargement of the urethral crest that protrudes into the lumen of the urethra

Where is the colliculus seminalis located?

Hillock (mucosal projection) in the pre-prostatic part of the pelvic urethra

What happens at the colliculus seminalis? 

The ducts of the vas deferens and the prostate open 

What is the urethralis muscle?

Urethra is surrounded by thickened walls due to striated urethralis/urethral muscle extending most of the length

Contraction of the muscle closes the external opening and lumen of the urethra

Voluntary control of the urethral muscle is provided by the somatic fibers of the pudendal nerve

How can you see the ureters on plain radiographs or ultrasonography?

Need a contrast medium

Ureteral papillae on ultrasound 

Readily identified in the trigone region of the urinary bladder, dorsally 

Dilated terminal ends of the ureter as they open into the bladder

Represent focally thickened regions within the urinary bladder wall which slightly protrude onto the luminal surface of the urinary bladder wall

Ectopic ureter

*More common in females

Ureter may open into the urethra or vaginal wallU

Ureteral Calculi

Obstruction then urinary incontinenceH

Hydroureter 

Dilation of the ureter, may be congenital or may be result of blockage from the presence of a calculus or other obstruction 

Can also be secondary to infection 

Ultrasonography of the urinary bladder

4 layers

Hypoechoic mucosa

Hyperechoic submucosa

Hypoechoic muscularis

Hyperechoic serosa

Where do transitional cell carcinomas like to reside?

Trigone

Where do bladder stones/calculi like to reside?

Occupy the most dependent part of the bladder

What objects create a shadow on ultrasonography?

Stones create a shadow, masses do not create a shadow