Pelvis+Viscera

toc =**Lecture Notes**=

[|Lecture 1]

=**Objectives**=


 * 1. Describe the surfaces of the urinary bladder and the viscera which contacts them.**

The bladder rests posterosuperiorly on the posterior aspect of the pubic symphysis. The most superior and anterior region is known as the apex, where the median umbilical ligament connects to the bladder. The area facing the posterior abdominal wall is the base, and the area of the internal urethral orifice is known as the neck, where the pubovesicular ligament (women) or the Puboprostatic ligament (men) attaches. The superior portion of the bladder is covered by abdominal peritoneum and is continuous with the greater sac of the abdomen. The inferior portion rests in a bed of endopelvic fascia, aureolar connective tissue specialized for "padding" the organs of the pelvic region. The bladder, when empty, is a resident of the true pelvis, resting on the posterior surface of the pubic symphysis (in a female, the uterus rests on the superior surface of the bladder in its normal anterverted and antiflexed position). However, when full, it may extend as far as the inferior portion of the small pelvis.



The peritoneum covering the bladder is reflected in the following places:

(1) Onto the anterior abdominal wall. (2) On the lateral aspects of the bladder, creating two grooves known as paravesical fossae (3) Onto the rectum in males directly posterior to the bladder, known as the rectovesical pouch. (4) Superiorly, onto the uterus in females directly posterior to the bladder, creating a recess known as the vesicouterine pouch. At the reflection point, there is very lose connective tissue attaching the peritoneum to the pubic symphysis, allowing for the peritoneum to separate from the abdominal wall to accommodate the filling of the urinary bladder.


 * 2. Describe the pelvic course of the ureters.**

The ureters run medioinferiorly away from the hilum of the kidney towards the urinary bladder, crossing anteriorly to psoas major a few cm below the bifurcation of the aorta and IVC (around L5). They enter the bladder on its posterior wall, at the apices of the inverted triangular region known as the trigone. When passing through the posterior wall of the bladder the ureters take an oblique course.


 * 3. Define the bladder trigone.**

The area arising embryologically from the mesonephric duct, the trigone is a smooth, epithelially lined triangular regiion at the neck of the bladder on the posterior inner aspect, defined in three corners by the entrances of the ureters on the posterior wall, and the urethral orifice.


 * 4. Describe the pelvic course of the vas deferens.**

The vas deferens arise from the epididymus, travelling through the spermatic cord to the inguinal canal, where they then exit the deep inguinal canal, running over top of and posterior to the bladder. At the inferior junction of bladder and prostate, the ductus deferens widen into the ampullas, and meet the outlet of the seminal vesicles on either side, forming the ejaculatory ducts, which then enter the prostate gland and ultimately the urethrra.


 * 5. Describe the the position and gross anatomical structure of the seminal vesicles.**

The seminal vesicles are a pair of tubular ducts directly posterointerior to the bladder in males, formed by an outpocketing of the ampulla of the vas deferens. They secrete about 60% of what will ultimately become semen in the final ejaculate, joining the vas deferens as they enter the prostate gland. No sperm enter the seminal vesicles. Their secretions consist of proteins, enzymes, fructose, flavin, vitamin c, prostaglandins and mucoid lubrication to provide support and nutrition to the sperm as they travel the female reproductive tract.

Sperm are formed in the seminiferous tubules, where they then enter the epididymus through the rete testis and travel up the ductus deferens, which pass through the inguinal canal, exiting the deep inguinal ring and traveling over the pubic ridge and over the apex of the bladder. The sperm follow the ductus deferens down the base of the bladder and enter the ejaculatory duct, where they are joined by the seminal mucoid secretions of the seminal vesicles during emission. The prostatic urethra contracts during ejaculation, propelling the sperm through the membranous then the spongy portions of the urethra, where it exits the dorsal aspect of the glans of the penis.
 * 6. Discuss the route of a sperm cell during emission and ejaculation.**

The posterior wall of the prostatic urethra has a central ridge known as the urethral crest, coming to an apex in a bulge of tissue known as the seminal colliculus. The seminal colliculus houses three orifices, two pin-sized entrances of the ejaculatory ducts, and a larger vestigial orifice known as the prostatic utricle (remnants of the vaginal canal in males).
 * 7. Describe the anatomy of the posterior wall of the prostatic urethra.**

The prostate is typically divided into three lobes based on the sagittal view of the ductwork that enters it. The "Y"- shaped pattern created by the entrance of the urethral canal and its descent through the prostate (left branch and stem) and the convergence of the two ejaculatory ducts on that canal (represented together as the right branch of the Y). The area to the left of the Y- shape is known the anterior lobe. The area to the right of the Y is known as the posterior lobe, and the area enclosed by the top branches of the Y is analagous to the medial lobe.
 * 8. Define the lobes of the prostate and understand how enlargement effects urine flow and retention.**

Enlargement is most common in the medial lobe, and may cause urethral compression. This "benign prostatic enlargement", or BPE, is associated with the inability to completely void urine from the bladder, as well as a sensation of frequent need to urinate. Urine that lies stagnant in the inferior ridges of the bladder as a result of BPE predisposes the patient to urinary bladder infections.


 * 9. Describe the peritoneal reflections on the pelvic viscera in both sexes.**

Females: The peritoneum of the abdomen descends down the anterior abdominal wall, reflecting over the bladder to form paravesical fossae on the lateral sides. Posterior to the bladder, it reflects slightly down the anterior wall of the uterus and superior part of the cervix, forming the vesicouterine pouch. The peritoneum then reflects up and over the uterus, uterine tubes, and ovaries, becoming a double-layered Broad Ligament of the Uterus where its inferior surfaces contact each other and fuse around the uterine structures. Posterior to the uterus, the peritoneum reflects back up over the superior third of the rectum on the anterior and lateral sides (intraperitoneal), and on the middle third of the rectum on the anterior side (retroperitoneal).

The space formed between the peritoneal reflections on the uterus and the rectum is the recto-uterine pouch (a.k.a. retrouterine recess, cul-de-sac, pouch of douglas). This is the lowest point in the peritoneal cavity when the woman is standing and a place for fluid in the abdominal cavity will collect. Fluid can be aspirated for analysis through the recto-uterine pouch via vaginal opening through the posterior vaginal wall. The space formed between the peritoneal reflections on the rectum and the lateral abdominal cavity are known as pararectal fossae.

Males: The only difference is that there is no vesicouterine pouch or rectouterine pouch -- instead, the reflection posterior to the bladder is known as the rectovesical pouch.


 * 10. Define the parts of the broad ligament.**

The Broad Ligament consists of three regions: Mesometrium: Considered the mesentery of the uterus, this laterally oriented region next to the uterus is the largest part of the broad ligament. Mesosalpinx: This area of the broad ligament is associated with the uterine tubes and is bounded medially by the ligament of the ovary, inferiorly by the ovary itself, and superiorly by the uterine tube. Mesovarium: This portion of the broad ligament surrounds the ovary itself and contains the suspensory ligament of the ovary medially. It is continuous with the "germinal layer" of the ovary.


 * 11. List the structures that lie between the lamellae of the broad ligament.**

The contents of the broad ligament include: The uterus, the uterine(fallopian) tubes, the ovary, the ligament of the ovary, the ovarian and uterine arteries, and the round ligament of the uterus.


 * 12. Delineate the parts of the uterus and vagina.**

//The uterus has three parts:// (1) The cervix (Neck of the uterus), which has an inferior external and superior internal os (opening); (2) The body of the uterus, the large region superior to the internal os, to the level of the junction of the uterine tubes; (3) and the Fundus, the "cap" portion of the uterus superior to the level of the junction of the uterine tubes.

The uterus also contains a thick layer of smooth muscle, known as myometrium, just deep to the inner surface endometrial layer. The myometrium of the uterine body is thick and pronounced, and the endometrium renews itself with the passage of each menstrual cycle; however, the cervix has mostly connective tissue in place of its myometrium, and does not lose its endometrium.

The vagina joins the cervical region of the uterus at a region known as the external os of the cervix. The external os is bounded by two ridges of viscera that protrude slightly into the vaginal canal, forming spaces known as posterior, lateral(2), and anterior fornices between the outer edge of these ridges and the vaginal wall. The cervix joins the vaginal canal at a 90-degree angle on its anterior aspect, causing the anterior wall of the vaginal canal to be shorter than the posterior wall.


 * 13. Define the normal position of the uterus and the terms anteversion/anteflexion and retroversion/retroflexion.**

The normal position of the uterus is anteversion and antiflexed. //Anteversion// refers to the angle at the external os being approximately 90 degrees, measured from the angle between the vagina and the cervical canal. //Anteflexion// refers to the angle ate the internal os being approximately 170 degrees, measured from the angle between the uterine and cervical canal.

//Retroversion// is the widening of the angle between the vaginal and cervical axis greater than 90 degrees. If the angle of the external os increases and approaches 180 degrees, the uterus is in danger of fall into the vaginal canal.

//Retroflexion// is the widening of the angle between the cervical and uterine axis greater than 180 degrees.

The two angles are independent of each other, and the uterus can possibly be found in any combination of anteversion, retroversion, anteflexion, or retroflexion.

See below diagram for variants of uterine position:


 * 14. Define the ligamentous supports for the uterus.**

Inferiorly, the plevic floor plays an essential to holding up the uterus. The uterus is also supported laterally by the broad ligament, a double layer of abdominal peritoneum encasing the uterus and superior aspect of the cervix. Anterolaterally, it is supported by the round ligament of the uterus, the embryological homolog to the male gubernaculum, which plays a role in maintaining uterine anteversion. Lastly, thickening of the endopelvic fascia anchors the cervix and helps fix the uterus in place.


 * 15. Explain the relationships and importance of the pelvic peritoneal pouches.**

Pelvic peritoneal pouches are of physiological importance because they may accumulate blood, ascites, or other abdominal fluids as a result of pathology. For example, in a female, appendicitis may be detected by the presence of ascites in the rectouterine pouch. The rectouterine pouch in particular is important because it represents the lowest point of the abdominal cavity when a woman is standing, and fluid in this area can be easily sampled by insertion of a needle through the posterior fornix of the vaginal canal and aspiration of fluid for analysis. Because the inner 4/5th of the vagina contains no somatic innervation, the woman will not feel pain when a needle pierces the posterior vaginal wall.


 * 16. Distinguish between false and true pelvis and understand which organs are located in each.**

The true pelvis is the region inferior to the pelvic brim, bounded inferiorly by the pelvic outlet. Organs found in the true pelvis include the empty bladder, non-pregnant uterus, lower portion of the rectum, perineal structures, and external reproductive organs of the male and female. The false pelvis is the region superior to the pelvic brim, separated by a physiological line (continuous with the abdominal cavity) indicated by the inferior aspect of the 5th lumbar vertebral body and the anterior superior iliac spines (ASIS). Structures of the false pelvis include the upper part of the rectum, the sigmoid colon, the gravid uterus, the superior aspect of the full bladder, and the prostate in males.


 * 17. Explain the relationships of the vaginal fornices to surrounding structures.**

The cervix creates recesses called fornices where it projects into the vagina. Fornices are anterior, posterior, and lateral, being circumferential to the cervix. The posterior fornix is the deepest and most closely associated with the recto-uterine pouch. The anterior fornix lies just posterior to the urinary bladder.