Pelvic Girdle, Inlet, Outlet & Styles

• The pelvic girdle connects the lower limb to the axial skeleton.
• Pelvic ligaments originate from the sacrum and attach to the pelvic bone, lumbar spine, and other pelvic points.

Pelvic Inlet and Outlet

• The pelvic inlet marks the boundary between the pelvic and abdominal cavities.
• It is located at the sacral promontory and the superior aspect of the pubic bones.
• The pelvic outlet is the inferior bony opening at the base of the pelvis.
• The pelvic outlet consists of the pubic arch, ischial spines, sacrotuberous ligaments, and the coccyx.
• The true pelvis is the space enclosed by the inlet and outlet.

Pelvic Styles

• There are four pelvic "styles": gynecoid, android, anthropoid, and platypelloid.
• Gynaecoid pelvises are common in females of Western civilization.
  • The inlet is slightly oval along the transverse axis.
  • Ischial spines are blunt and don't protrude.
  • The sacrum is broad with deep concavity.
  • It is ideal for vaginal delivery.
• Android pelvises are common in males.
  • The inlet is heart-shaped due to a large sacral promontory.
  • Ischial spines are conical and protrude.
  • The sacrum is slightly curved.
  • Ideal for bulky muscle attachment.
• Anthropoid pelvises have features of both android and gynaecoid pelvises.
  • The inlet is oval in the anteroposterior axis.
  • Ischial spines are blunt.
  • The sacrum is long, narrow, and less curved than a gynecoid pelvis.
  • High risk of obstructed labor in vaginal delivery.
• Platypelloid pelvises are a contracted pelvis type.
  • They have a narrow inlet and broad outlet.
  • They are characterized by a decreased antero-posterior diameter.
  • The inlet and ischial spines resemble those of gynecoid pelvises
  • Sacrum is slightly curved.

Female Pelvic Organ Support Ligaments

• Round ligaments connect the uterus to the mons pubis.
  • They attach near the uterine tubes and extend to the labia majora.
  • They prevent excessive movement of the pregnant uterus.
• The broad ligament is a flat sheet of peritoneum related to the uterus, fallopian tubes, and ovaries.
• Uterosacral ligaments attach the upper vagina, cervix, and uterus, to the 3rd sacral vertebra, providing posterior stability.
• Cardinal ligaments connect the upper vagina, cervix, and uterus to the pelvic sidewalls.

Endopelvic Fascia

• The endopelvic fascia is a connective tissue network enveloping the pelvic viscera and pelvis.
• It lines the walls and floor of the pelvis and fuses to the periosteum of the hipbones.
• It consists of parietal fascia (covering pelvic muscles) and visceral fascia (covering pelvic organs, vessels, and nerves).
• Three levels of endopelvic fascial support in women:
  • Level 1 suspends the upper vagina and cervix.
  • Level 2 supports the middle vagina and posterior bladder wall.
  • Level 3 attaches the lower vagina to the perineal membrane and includes urethral suspensory ligaments.

External Female Genitals (Vulva)

• The mons pubis, a fatty pad over the pubic bone, becomes covered in pubic hair after puberty.
• Labia majora are hair-covered skin folds posterior to the mons pubis.
• Labia minora are thinner, pigmented folds medial to the labia majora.
  • They protect the urethra and entrance to the reproductive tract.
• The clitoris (glans clitoris) is located where the labia minora meet.
  • The clitoris is rich in nerves for sexual sensation and orgasm.
• The hymen is a membrane that partially covers the vaginal entrance.
• The vaginal opening is between the urethra and anus.
• The Bartholin's glands flank the vaginal opening.

Vagina

• The vagina is a muscular canal (~10 cm long).
  • The vagina acts as the entrance to the reproductive tract and exit from the uterus.
• Anterior and posterior vaginal walls form longitudinal columns or ridges.
• The superior vagina (fornix) meets the cervix.
• Vaginal walls consist of:
  • Outer fibrous adventitia
  • Middle smooth muscle layer
  • Inner mucous membrane with transverse folds (rugae)
• The middle and inner layers allow expansion for intercourse and childbirth.
• The hymen can partially surround the vaginal orifice which can be ruptured during exercise, intercourse, and childbirth.
• Bartholin's and lesser vestibular glands secrete mucus to moisten the area.
• The vagina maintains a normal flora of microorganisms.
  • Lactobacillus bacteria secrete lactic acid, maintaining an acidic pH (below 4.5).
  • The acidic environment protects against pathogens, making the vagina self-cleansing.

Uterus and Cervix

• The uterus is a muscular organ that supports the developing embryo.
  • Average size is 5 cm wide by 7 cm long when not pregnant.
• Three sections of the uterus:
  • Fundus: superior to the uterine tube openings.
  • Body (corpus): the middle section.
  • Cervix: the narrow, inferior portion projecting into the vagina.
• The cervix produces mucus secretions, to facilitate sperm movement.
• Three layers of the uterine wall:
  • Perimetrium: the superficial, serous membrane.
  • Myometrium: the thick, middle layer of smooth muscle for contractions.
    • Fibers run horizontally, vertically, and diagonally.
    • Used for powerful contractions during labor and weaker contractions during menstruation.
  • Endometrium: the innermost layer.
    • Connective tissue lining (lamina propria) covered by epithelial tissue.

Clitoris

• The clitoris is an erectile structure, homologous to the penis.
• It is located inferior to the mons pubis at the anterior end of the vulva.
• The clitoris is composed of paired crura, a body, and a glans
• Unlike the penis, the clitoris isn't circumscribed by a foreskin.
• It serves no urinary role: the urethra opens separately, posterior to the clitoris.
• Most of the clitoris is internal, with only the glans (5-8 mm) externally positioned.
• Some clitoral tissue is in the anterior vaginal wall.
• During sexual arousal, the clitoris fills with blood.
  • Ischiocavernosus and bulbocavernosus muscles contract, compressing veins.
  • Arterial blood flow leads to engorgement of the venous spaces in the corpora cavernosa.
  • Stimulation leads to female orgasm due to rich sensory innervation.

Penis

• The penis is an external organ of the male reproductive system.
• Two main functions: sexual intercourse an micturition
• During erotic stimulation, the penis undergoes erection.
• Semen moves out of the urethra through the external urethral orifice and ejaculation occurs.
• Subsequently, the penis undergoes remission and returns to a flaccid state.
• The penis contains the urethra, which carries urine from the bladder.

Penis Structure

• The penis is made of the root, the body and the glans
• The root is the most proximal fixed part located in the superficial perineal pouch, not visible externally.
• Contains 3 erectile tissues: two crura and the bulb of the penis, and two superficial pelvic floor muscles.
• The body is located between the root and glans and is suspended from the pubic symphysis.
• The body is composed of three cylinders of erectile tissue- two corpora cavernosa, and the corpus spongiosum.
• The glans is the most distal, conical part, formed by the distal expansion of the corpus spongiosum, containing the external urethral orifice.

Erectile Tissues

• The root contains the left and right crura, and the bulb of the penis.
• The left and right crura are attached to the ischial ramus and covered by the ischiocavernosal muscles.
• The bulb is in the midline of the penile root.
• Erectile tissues extend into the body of the penis:
  • The crura continue anteriorly into the dorsal aspect to form the corpora cavernosa.
  • The bulb forms the ventral corpus spongiosum, which contains the urethra.
  • The corpus spongiosum expands distally to form the glans penis.

Neurovascular Supply

• The penis is supplied by: dorsal arteries, deep arteries, and bulbourethral artery.
• These vessels branch from the internal pudendal artery.
• The internal pudendal artery arises from the anterior division of the internal iliac artery.
• Venous blood is drained by paired veins.
• The cavernous spaces are drained by the deep dorsal vein, emptying into the prostatic venous plexus.
• Superficial structures are drained by the superficial dorsal veins.

Prostate

• The prostate is part of the male reproductive system, located below the bladder and above the pelvic floor muscles.
• The rectum is behind the prostate, allowing for manual palpation.
• Ducts in the prostate flow into the urethra, which passes through the prostate.
• The prostate is chestnut-sized (~30 grams).
• The prostate produces fluid that, with sperm cells and fluids from other glands, makes up semen.
• Prostate muscles press semen into the urethra during ejaculation.