Perineal Pouches: Anatomy, Conditions, and Surgical Interventions

The image below shows the Coronal Section of the Female, the Front View of the Urinary Bladder, and Pouches.

• The deep perineal pouch has two muscles;
  • One which Runs transversely - DTP
  • Another that Runs around the urethra-  external urethral sphincter.
    • Helps to hold the urine at our own will with the help of the pudendal nerve.
• DTP + external urethral sphincter makes the Urogenital diaphragm.
  • The urogenital diaphragm is present in the deep perineal pouch.
• Pelvic diaphragm - Majorly contributed by levator ani muscle (LAM) and contributed by other muscles.
• In females, the internal urethral sphincter is poorly developed but well developed in males.

Lithotomy Position 

In a female in the lithotomy position has all the structures which help in forming the perineal pouches.

• Anterior bone - Pubis bone 
• Posterior bone -  Sacrum and coccyx bone.
• Lateral bone - Ischial tuberosity.
• Anterolateral - Ischiopubis Ramus.

Female in Lithotomy Position

• Female perineum
  • Glans clitoris - From genital tubercle.
  • Labia minora - Urethral or genital phore.

• Hymen - it is a Membrane covering the vaginal opening partially.
• Below the hymen, there is a vestibule where the urethra and vagina open.
  • The vestibule is the space bounded by the two flaps of labia minora.

Inferior View of a Female Perineum

• Great vestibule gland of bartholin
  • More posteriorly present.
  • It is present at the junction of the middle 1 ⁄ 3rd of the labia majora and the posterior 1 ⁄ 3rd of the labia majora.
  • Bartholin gland present in the superficial perineal pouch, and the duct also opens in the superficial perineal pouch.
• Hymen, a membrane incompletely covering the vaginal orifice.
  • It is deeper and superior in an anatomical position.
  • Sometimes, Bartholin gland cysts are also present there more posteriorly.

Bartholin Gland Cyst

This is a very important pathology as it is very commonly seen in the obstetrics and gynecology OPD. this is also an important topic for the NEET-PG/ INICET/ FMGE examination.

• Bartholin gland cysts are majorly present at the junction of the middle 1 ⁄ 3rd of the labia majora and the posterior 1 ⁄ 3rd of the labia majora.
• The Bartholin gland is present in the superficial perineal pouch and the duct also open in the superficial perineal pouch.
  • It is presented more posteriorly.

• Anterior bone - Pubis.
• Posterior bone - Sacrum and coccyx bone.
  • The sacrotuberous ligament presents posterolateral boundary in the perineum. 
  • It gives origin to the gluteus maximus muscle.
  • It is between the sacrum and tuberous (Ischial tuberosity) bone, thus the name sacrotuberous ligament.
• Lateral bone - Ischial tuberosity.
• Anterolateral - Ischiopubis Ramus.
• The urogenital triangle is present in the perineum.
  • Reason: It is where the urethra and vagina opens.
• The anal triangle is where the Anal opening is present.
• Between the vagina and anus, the perineal body is present.
  • The perineal body is present at the midline with central perineal tendon, common peroneal tendon, between the vagina anteriorly and the anal canal posteriorly.

• Superficial transverse perineal muscle (STP)
  • It is present in the superficial pouch.
  • The STP and external sphincter muscle are quite superficial in the section.
  • If gone deeper in the section, deep perineal pouch and pelvic diaphragm.
    • Pelvic diaphragm is basically levator ani muscle (LAM) - Deeper most muscle in the section.
    • Gluteus maximus muscle present. It originates from a sacrotuberous ligament.
• Deep transverse perineal muscle (DTP)
  • It is present in a deep perineal pouch.

Inferior View

After removing the skin and Colles fascia, a superficial perineal pouch is present.

• MUSCLES In the superficial perineal pouch :-
  • Bulbospongoius - Around the bulb of the vagina.
  • Ischiocavernosus - Lateral muscle.
    • It doesn't insert in the perineal body.
    • Reason: The ischiocavernosus is lateral muscle and cannot run into the midline where the perineal body is present.
  • Superficial transverse perineal muscle
• After removing superficial transverse perineal muscle, and going deeper, more superior in anatomical position, a perineal membrane is present.
  • It is the boundary line between the superficial perineal pouch and deep perineal pouch.
  • It is triangular in shape.
• If the perineal membrane is removed, the section shows the deep perineal pouch.
  •  DTP muscle is present.
  • External urethral sphincter is also present at the DPP.
    • It helps to hold the urine at our own will.
    • These muscles are inserted into the deep perineal body.

• The deeper most muscle - levator ani muscles.
  •  it can elevate the anus at that site.
  • It makes the boundary line for the pelvic diaphragm.
• If the pelvic diaphragm is removed, where the pelvic viscera is seen,
  • Rectum
  • Uterus
  • Urinary bladder.
• The last boundary to the pelvis is the pelvic diaphragm.
  • It is the boundary between the deeper and superficial pelvis and perineum.

Ischiorectal Fossa

• It is the space between the ischium bone laterally and the rectum in the midline (Deeper).
• Also called the ischioanal fossa, as the superficial structure is anus in the midline.
• Sometimes, pus will form called an ischiorectal abscess and it should be drained.
• Boundaries of the ischiorectal fossa:
  • Medial - Levator ani.
  • Lateral wall - Obturator internus.
    • It will have some obturator internus muscle with obturator fascia.
    • In the obturator fascia, the pudendal canal is present with the pudendal nerve a part of pudendal NVB.
    • The pudendal nerve is present at the lateral wall of the ischiorectal fossa.
    •  the inferior rectal nerve, a branch pudendal nerve, is given.
    • The inferior rectal vessels and a nerve will come to the anus.
    • inferior rectal Neurovascular bundle, the content of the ischiorectal fossa, comes to the anus.
    • The pudendal Neurovascular bundle gives the inferior rectal Neurovascular bundle, which comes towards the anus.
  • Anterior - Perineal membrane (Triangular shaped) with the STP muscle.
  • Posterior - Sacrotuberous ligament with called gluteus maximus.
• The hip bone has three parts;
  • Anteriorly - Pubis bone.
  • Laterally - Ilium bone.
  • More posteriorly - Ischium bone.

Ischiorectal Fossa Front View 

• Ischium bone is present on the lateral side of the Uterus + Vagina or Rectum + Anal canal.
• The obturator internus is present on the ischium bone.
• Levator ani muscle forms the pelvic diaphragm.
• Ischiorectal fossa, the space between ischium bone laterally and rectum in the midline (More deeper).

• Levator ani muscle supporting the viscera like rectum, uterus, urinary bladder and forms the pelvic diaphragm.
• Deep perineal pouch is presented with a urogenital diaphragm having DTP and external ureteral sphincter.
• The floor of the urogenital diaphragm, perineal membrane and is also the roof of superficial perineal pouch.
• The floor of the superficial perineal pouch is the Colles fascia.
  • In dissection, below the skin, the Colles fascia is seen.
  • It has;
    • Ischiocavernosus muscle laterally.
    • Bulbospongiosus medially (Near the midline).
    • It is the floor of DPP.
    • The deep perineal pouch has two muscles in the urogenital diaphragm.
• Levator ani muscle forms the pelvic diaphragm, also related to the ischiorectal fossa.
• Urinary bladder + urethra or rectum + anal canal beside;
  • Ischium bone on which obturator internus is present, upon which obturator fascia is present.
• The levator ani muscle is the medial boundary for the ischiorectal fossa.
• The lateral boundary is the ischium bone for the ischiorectal fossa.
• The pudendal canal is presented at the obturator fascia. 
• Pudendal canal got pudendal NVB in the lateral wall of ischiorectal fossa,
  • Pudendal nerve,
  • Pudendal artery, and 
  • Pudendal vein.

This topic can be quite challenging for someone reading it for the first time. Thus, it is highly advisable that the video be watched along with it. This will give you a better understanding of the topic, and you will be able to pass all your competitive and theoretical exams with flying colors.

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