SFP: contents of male pelvis Flashcards
Describe the basic positioning of the sigmoid colon
Begins superior to the pelvic inlet and extends to the 3rd sacral vertebra
What is found anterior to the sigmoid colon in males?
The urinary bladder
What is found anterior to the sigmoid colon in females?
Superior portion of the uterus
What arterial/venous branches supply and drain the sigmoid colon?
Sigmoid arteries/veins from the inferior mesenteric artery and vein
What is the sympathetic nerve supply to the sigmoid colon?
Fibers from L1 and L2 (lumbar splanchnic nerves)
Where do sympathetic nerve fibers to the sigmoid colon synapse?
Inferior hypogastric plexuses or inferior mesenteric ganglia
What is the parasympathetic nerve supply to the sigmoid colon?
S2-4 (pelvic splanchnic nerves)
Where do parasympathetic nerve fibers to the sigmoid colon synapse?
Ganglia within or near viscera
Describe the general positioning of the rectum
It is anterior to the curve of the sacrum and coccyx and ends as it passes through the pelvic diaphragm
What is the rectovesical pouch?
Space between the upper 2/3rds of the rectum and urinary bladder in males formed by reflection of peritoneum
Describe the lower 1/3rd of the rectum in males
Posterior to the bladder, below peritoneum, and site of termination of the vas deferens, seminal vesicles, and the prostate
What is the rectouterine pouch?
Space between the upper 2/3rds of the rectum and uterus/posterior wall of the vagina in females formed by the anterior reflection of the peritoneum
Describe the lower 1/3rd of the rectum in females
Not covered by peritoneum and the interior portion is in contact with posterior aspect of the vagina
What forms the external longitudinal layer of ME in the rectum?
The tenia coli
What are transverse folds?
Projections/folds formed by the union of a mucus membrane and circular muscle layer of ME
What is the arterial supply of the rectum?
Arterial supply is divided into thirds; superior rectal artery, middle rectal artery, inferior rectal artery
Describe the superior rectal artery
Branch of inferior mesenteric artery; divides into left and right branches that anastomose distally with each other as well as middle and inferior arteries
The middle rectal artery branches from…
Internal iliac artery
The inferior rectal artery branches from…
Internal duodenal artery
What veins drain the rectum?
Superior, middle, and inferior rectal veins
Where does the superior rectal vein drain to?
Inferior mesenteric vein (portal system)
Where does the middle rectal vein drain to?
Internal iliac vein (caval system)
Where does the inferior rectal vein drain to?
Internal duodenal vein (caval system)
What communication between caval and portal circulations exist in relation to the rectum?
The superior rectal vein anastomoses with the middle and inferior rectal veins
What is the sympathetic innervation to the rectum?
Fibers from L1 and L2, aka lumbar and sacral splanchnic nerves
What is parasympathetic innervation to the rectum?
S2-4 aka pelvic splanchnic nerves
What do visceral afferent fibers from the rectum follow in terms of nerves?
Pelvic splanchnic nerves to levels S2-4
What is the lymphatic drainage of the rectum?
Upper part drains to the inferior mesenteric nodes and lower part drains to internal iliac nodes
Describe the general positioning of the anal canal
Distal to the rectal ampulla at the level of the sling formed by the puborectalis muscle; found in the anal triangle
What is the ischiorectal fossa?
Fat-filled pockets that bind the anal canal laterally in both men and women; they allow for space/flexibility of the anal canal
What is the pectinate line?
It divides the superior and inferior portions of the anal canal
Describe the histology of the superior portion of the anal canal
Lined by columnar epithelium, has anal columns, valves, and sinuses
Describe the histology of the inferior portion of the anal canal
Lined by nonkeratinized stratified squamous epithelium and does not contain anal columns or associated structures
Describe the internal anal sphincter
Involuntary smooth muscle sphincter formed from the thickening of the internal circular layer of smooth muscle
Describe the external anal sphincter
Voluntary striated muscle sphincter divided into 3 parts (deep, superficial, subcutaneous)
Describe the superficial part of the external anal sphincter
Attached posteriorly to the coccyx and anteriorly to the perineal body
What is the anorectal ring?
Formed from the internal sphincter and 3 parts of the external sphincter; it is palpable on rectal exam
The puborectalis muscle blends with the ___ and forms ___
Deep part of the external anal sphincter; sling that passes at the junction of rectum and anal canal
Describe blood supply of the anal canal
Superior to the pectinate line it is the superior rectal artery, inferior to the pectinate line it is the inferior rectal artery. The middle rectal artery forms anastomoses with the superior and inferior to supply the anal canal as well. Venous supply follows the same.
Describe nerve supply to the anal canal superior to the pectinate line
Sacral and pelvic splanchnic nerves aka autonomic innervation
Describe nerve supply to the anal canal inferior to the pectinate line
Somatic motor innervation/ somatic afferents through the inferior rectal nerve
What is the detrusor muscle?
Three layers of smooth muscle that make up the bladder wall
When full, how can the bladder be palpated?
Through the anterior abdominal wall superior to the pubic symphysis
How does the apex of the bladder connect to the body?
Connected to the umbilicus by the umbilical ligament (urachus remnant)
What are is the trigone of the bladder?
A smooth triangular area between ureteric orifices
What are ureteric orifices?
Openings of ureters into the urinary bladder at the superolateral angles
Describe vas deferens/seminal vesicles in relation to the bladder
They terminate on the inferior aspect of the posterior surface of the bladder superior to the prostate
What is the blood supply to the bladder?
Superior and inferior vesical arteries (branches of internal iliac)
What is the venous drainage of the bladder?
The vesical venous plexus that drains to the internal iliac vein via superior and inferior vesical veins
What does the vesical venous plexus communicate with in males?
Prostate venous plexus
What is the sympathetic innervation of the bladder?
Lumbar and sacral splanchnic
What is the parasympathetic innervation of the bladder?
Pelvic splanchnic nerves
What do pelvic splanchnic nerves do in the bladder?
Stimulate contraction of the smooth muscle wall and inhibit action of internal urethral sphincter
Describe the internal urethral sphincter
Involuntary sphincter formed by a thickening of circular smooth muscle at the neck of the bladder
Describe the external urethral sphincter
Voluntary sphincter that has somatic innervation from the perineal nerve
What are the parts of the male urethra?
Prostatic, membranous, spongy
Describe the prostatic urethra
The widest part of the urethra surrounded by the prostate gland; posterior wall contains urethral crest, prostrating groove with openings for the prostate gland, prostatic utricle, and ejaculatory ducts
Where do the male reproductive and urinary systems communicate?
The prostatic urethra
Describe the function of the prostate gland
Secretes thin alkaline fluid that adds to seminal fluid at the time of ejaculation. This helps neutralize acidity in the vagina to help the sperm survive
What is the posterior aspect of the prostate related to?
The rectal ampulla
What binds the prostate laterally?
Levator ani muscles
Describe the lobes of the prostate
- Anterior lobe has little glandular tissue 2. Middle lobe is between the prostatic urethra and ejaculatory ducts; may enlarge with BPH 3. Posterior lobe is posterior to the ejaculatory ducts; palpable on rectal exam
What is the arterial supply of the prostate?
Inferior and middle rectal arteries from the internal iliac artery
What do sympathetic fibers do to the prostate?
Stimulate smooth muscle during ejaculation
What is the innervation of the prostate?
Lumbar and pelvic splanchnic nerves
Describe the ascending pathway of vas deferens
It ascends through the spermatic cord and deep ring, crosses external iliac vessels, passes along the lateral pelvis and crosses ureters, runs on superior bladder surface, and joins the duct of seminal vesicle
