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2. Diagram the major features of the pelvic girdle. 

The pelvic girdle connects the lower back (i.e. lumbar vertebrae & sacrum) to the lower limbs (i.e. femurs and beyond).

The bony pelvis is composed of a pair of coxal (hip) bones. They form 2 sacro-iliac (SI) joints with the sacrum, and the coxal bones meet anteriorly at the pubic symphysis, a cartilaginous joint.

The coxal bones are each a set of 3 fused bones:

• Ilium: superior and fan-shaped

• Ischium: more posteriorly-placed

• Pubis: anteriorly-placed

These parts of the bone all meet and fuse within the acetabulum (where the femoral head articulates with the coxal bone).

When discussing the pelvic girdle, it is sometimes useful to delimit the true (lesser) pelvis from the false (greater) pelvis. These are divided by the pelvic brim.

• Pelvic brim: bony elements that define the pelvic inlet

  • Connects the sacral promontory (the anterior projecting edge of the body of the S1 vertebrae), around the ilium, to the superior portions of the pubis bones

• False (greater) pelvis: lies superior to the pelvic brim

  • Predominantly occupied by abdominal viscera

• True (lesser) pelvis: lies inferior to the pelvic brim and superior to the pelvic outlet

  • Will include organs of the pelvic cavity and deepest portions of the perineum

3. Describe the spatial relationships of the viscera and peritoneum of the pelvic cavity.

The pelvis contains viscera of the GI, urinary, and reproductive (and associated endocrine) systems.

Gastrointestinal

The pelvis transmits the distalmost portions of the digestive system: the distal sigmoid colon, rectum, and anal canal. The rectum is found in the posterior aspect of the pelvic cavity.

Reproductive

When present in the pelvis, reproductive organs are typically situated anterior to the rectum, and posterior, lateral, superior, or inferior to the urinary bladder depending on the organ.

Reproductive (or associated endocrine) organs potentially located in the pelvic cavity include:

• Uterus

• Uterine (Fallopian) tubes

• Ovaries

• Vagina

• Prostate gland

• Seminal vesicles (glands)

• Ductus (vas) deferens

• Bulbo-urethral glands

Urinary

The pelvis contains the urinary bladder, and transmits the distal ureters to the urinary bladder. The ureters enter the pelvic cavity adjacent to the bifurcation of the common iliac aa., and connect to the posterior aspect of the urinary bladder. The urinary bladder is found in the anterior aspect of the pelvic cavity, closely associated with the pubic symphysis.

Peritoneum

The pelvic viscera are variably covered with peritoneum. Depending on their relationship to the peritoneum, these structures may be intra-, retro-, or subperitoneal.

Assigned Female At Birth (AFAB) Peritoneum/Pelvic Cavity Relationships

The peritoneum contacts the anterior abdominal wall, covers the posterior portion of the bladder, reflects superiorly to cover the anterior surface of the uterus (if present), traverses over the fundus of the uterus, and covers the posterior surface of the uterus.

At about the level of the internal os of the cervix, the peritoneum reflects onto the rectum and continues up the posterior wall. This leaves the vagina and bottom third of the rectum devoid of any peritoneum covering.

Areas where the peritoneum reflects from one portion of viscera to another create pouches, or are simply referred to as reflections. 

There are typically two pouches in individuals assigned female at birth:

• Vesico-uterine pouch/Bladder reflection/Anterior cul-de-sac

  • Created by the reflection between the urinary bladder and uterus

• Recto-uterine pouch/pouch of Douglas/Posterior cul-de-sac

  • Created by the reflection between the uterus and rectum

  • Most inferior extension of the peritoneum

  • Close relationship with the posterior vaginal fornix

As gravity may guide fluid inferiorly, materials (blood, exudate, etc.) may accumulate in the recto-uterine pouch. This area may be accessed with a hypodermic needle via the posterior vaginal fornix in a procedure called culdocentesis.

Assigned Male At Birth (AMAB) Peritoneum/Pelvic Cavity Relationships

The peritoneum contacts the anterior abdominal wall, covers the posterior portion of the bladder and reflects superiorly onto the rectum, and continues to the posterior wall. This leaves the prostate, seminal vesicles, and the bottom third of the rectum devoid of any peritoneal covering.

The area where the peritoneum reflects from the bladder to the rectum is called the recto-vesical pouch.

Inferior to the pelvic viscera is the muscular floor of the pelvic cavity, the pelvic diaphragm. The pelvic diaphragm separates the pelvic cavity from the perineum, which will be discussed in the following session.

The triangular space is formed by the ureteric orifices and the internal urethral meatus in the internal bladder is called the trigone.

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

Urethra

Typical urethral anatomy of an Assigned Female at Birth (AFAB) individual

The 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.

Typical urethral anatomy of an Assigned Male at Birth (AMAB) individual

Typically, there are 3 major parts of the AMAB urethra:

• 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

Uterine (Fallopian) tubes

The uterine (Fallopian) tubes are laterally continuous with the body of the uterus, and serve as a pathway for oocytes (and their ontogenetic derivatives) from the ovary to the uterine cavity. The uterine tubes are intraperitoneal.

Four major parts of the tubes (lateral to medial):

• Infundibulum: most distal portion of the uterine tube which opens into the peritoneal cavity via the abdominal ostium

  • Have fringed processes, fimbriae, at distal-most end that are in close proximity to the ovary

• Ampulla: longest and widest portion of uterine tube

  • Fertilization of the oocyte most typically occurs in this part

• Isthmus: narrowest portion

• Uterine part: leads into the uterine cavity

Tubal ligation (‘tubes tied’) is a surgery where the uterine tubes are ligated, incised, clamped, or occluded to prevent the passage of oocytes to the uterus.

Ovaries

The typically paired ovaries are gonads in which oocytes (gamete or germ cell) develop as well as an endocrine function with production of specific hormones.

Oophorectomy is the surgical removal of an ovary.

Uterus

The uterus is a pyriform (pear-shaped), distensible organ which may host a developing embryo & fetus until parturition. 

It is structurally composed of 2 parts:

• Body: muscular, ‘upper’ two-thirds

  • Fundus: portion of the body of the uterus superior to the uterine ostia (where the uterine tubes enter the uterus)

• Cervix: lower, fibrous third

Hysterectomy is the surgical removal of the uterus.

Vagina

The vagina is a muscular passage from the cervix of the uterus to the vestibule of the vagina. It is posteriorly adjacent to the base of the urinary bladder and urethra, and is anteriorly adjacent to the rectum.

Proximally, the vaginal fornix surrounds the protrusion of the cervix into the vagina. The vaginal fornix may be conceptually divided into anterior, lateral, and posterior parts, with the posterior vaginal fornix being most clinically significant, as it offers access to the recto-uterine pouch to enter the peritoneal cavity.

Peritoneal & Endopelvic Fascial Ligaments

Broad ligament of uterus

The broad ligament of the uterus is composed of two layers of peritoneum and serves to divide the true pelvis into an anterior part (containing the bladder) and a posterior part (containing the rectum), in addition to attaching the uterus to the lateral pelvic walls.

Components of the broad ligament:

• Mesometrium: covers the body of the uterus

• Mesosalpinx: covers the uterine tube

• Mesovarium: covers the ovaries

Suspensory (Infundibulopelvic/IP) ligament of ovary 

This ligament attaches the aorta and inferior vena cava to the lateral pole of the ovary, and conducts the gonadal a. & v. This ligament is continuous with the mesovarium.

Ovarian ligament

The ovarian ligament connects the ovary and the uterus, and is a remnant of the gubernaculum.

Round ligament of uterus

The round ligament of the uterus extends from the uterus to the labium majus. The round ligament is a remnant of the gubernaculum and will traverse the inguinal canal. This ligament is closely associated with the artery of (Sampson) the round ligament.

Transverse cervical (cardinal) ligament

The transverse cervical (cardinal) ligament extends from the cervix to lateral pelvic wall, and transmits the uterine a. adjacent to the base of the broad ligament. It is in this location that the ureter travels in close approximation and inferior to the uterine a.

7. Describe the gross anatomy of the AMAB reproductive tract, spermatic cord, scrotum, and penis.

Scrotum

The scrotum is a cutaneous expansion suspended from the perineum and inferior portion of the proximal body of the penis. The scrotum contains the testes, which are suspended by the spermatic cords. The layers of the scrotum and spermatic cord are homologous and contiguous with many of the layers of the anterior abdominal wall.

Testes

The testes are gonads that produce spermatozoa and specific hormones. Each testis is enveloped by the tunica vaginalis, a serous membrane derived from peritoneum, and tunica albuginea, a dense white fascial layer which surrounds and compartmentalizes segments of the seminiferous tubules.

Spermatozoa travel from the coiled seminiferous tubules through straight tubules into the rete testis. From the rete testis, spermatozoa move into the epididymis before traveling to the ductus (vas) deferens. The epididymis is composed of a head and body (which receive spermatozoa from the rete testis) and tail.

 To review the pathway of spermatozoa:

Seminiferous tubules → Rete testis → Epididymis head → Epididymis body → Epididymis tail → Ductus deferens

Spermatic cord

The spermatic cord consists of 3 layers of tissues that envelop contents. These layers include (with associated homologs):

• External spermatic fascia ( = external oblique m. fascia),

• Cremaster m.. & fascia ( = internal oblique m. & fascia),

• Internal spermatic fascia ( = transversalis fascia)

The major contents of the sheath are the:

• Ductus (vas) deferens,

• Testicular a.

• Pampiniform plexus (of veins)

  • A dilation or enlargement of the pampiniform plexus (of veins) is known as a varicocele. This is more frequent on the left side due to draining into the L. renal v. versus directly into the IVC on right side).

Other contents include: artery of ductus deferens, cremasteric a., genital br. of genitofemoral n., autonomic fibers (sympathetics follow the arteries; parasympathetics follow ductus deferens), and lymphatics.

Ductus (vas) deferens

The ductus (vas) deferens conducts spermatozoa from the testis, through the spermatic cord (and through the inguinal canal) to the deep ring, and travels posteriorly to the bladder, superior to the ureter, ultimately joining the seminal vesicle to form the ejaculatory duct. The distalmost and dilated portion of the ductus deferens is referred to as the ampulla of ductus deferens.

The ligation or embolization of the ductus (vas) deferens is known as a vasectomy.

Seminal Glands (Vesicles)

The seminal glands (vesicles) are located near the prostate between the posterior bladder and anterior rectum. The seminal glands produce a fluid that is more alkaline and contains fructose, and will be a significant portion of semen. The ducts of the seminal gland will join with the ampulla of ductus deferens to form the ejaculatory duct. The ejaculatory ducts will run through the posterior prostate to reach the prostatic urethra.

Prostate Gland

The prostate gland sits inferior and in close approximation with the neck of the urinary bladder. It surrounds and conducts the prostatic urethra to the membranous urethra. The prostate gland receives the ejaculatory ducts.

With benign prostatic hyperplasia (BPH), glandular cells of the transitional (peri-urethral) zone may multiply, and exert pressure upon the prostatic urethra, which can make voiding the bladder difficult. A common treatment for BPH is transurethral resection of the prostate (TURP), a procedure involving the passing of a resectoscope through the urethra, and removing portions of the prostate gland in order to maintain patency of flow.

The prostate may be palpated through the anterior wall of the rectum.

Bulbo-urethral (Cowper’s) Glands

The bulbo-urethral (Cowper’s) glands are pea-shaped glands located posterolateral to the membranous portion of the urethra. The ducts for these glands will pass through the perineal membrane, and open into the spongy urethra located in the bulb of the penis.

Penis

The penis consists of a root (that anchors the penis to the perineum) and body (that serves the intromittent organ). The root of the penis consists of three masses of erectile tissue within the superficial perineal space (the crura and bulb of the penis).

Three tubes of erectile tissue internally traverse the penis: laterally paired corpora cavernosa and a single corpus spongiosum.

In standard anatomical position (SAP), the penis is in an erect state. The side of the penis in SAP may contact the anterior abdomen is the dorsum (dorsal surface) of the penis. Opposite from the dorsal surface is the urethral surface.

The distal end (tip) of the body is the glans penis, a bulbous, skin-covered elaboration of corpus spongiosum. 

The spongy (penile) urethra is transmitted by the corpus spongiosum and terminates at the external urethral meatus of the glans penis.