The Perineum Flashcards
1
Q
What is the perineum?
A
- it corresponds to the outlet of the pelvis and is lozenge-shaped
- it can be divided into two triangular parts by drawing a line transversely between the ischial tuberosities
- -> the anterior triangle which contains the external urogenital organs (urogenital triangle)
- -> the posterior triangle which contains the termination of the anal canal (anal triangle)
2
Q
Describe the urogenital triangle
A
- it is bound anteriorly and laterally by the pubic symphysis and the ischiopubic rami
- it has been divided into two compartments
- -> the superficial and deep perineal spaces
- -> separated by the perineal membrane which spans the space between the ischiopubic rami
- the levator ani muscles are attached to the cranial surface of the perineal membrane
- the vestibular bulb and clitoral crus lie on the caudal surface of the membrane and are fused with it
- -> these erectile tissues are covered by the bulbospongiosus and the ischiocavernosus muscles
3
Q
Describe the 3 different superficial muscles of the perineum
A
- superficial transverse perineal muscle
- -> it is a narrow slip of a muscle that arises from the inner and forepart of the ischial tuberosity and is inserted into the central tendinous part of the perineal body
- -> the muscles from the opposite side, the external anal sphincter from behind and the bulbospongiosus in the front all attach to the central tendon of the perineal body - bulbospongiosus
- -> runs on either side of the vaginal orifice covering the lateral aspects of the vestibular bulb anteriorly and the bartholin’s gland posteriorly
- -> some fibres merge posteriorly with the superficial transverse perineal muscle and the EAS in the central fibromuscular perineal body
- -> anteriorly its fibres pass forward on either side of the vagina and insert into the corpora cavernosa clitordis, a fasiculus crossing over the body of the organ so as to compress the deep dorsal vein
- -> this muscle diminishes the orifice of the vagina and contributes to the erection of the clitoris - ischiocavernosus muscle
- -> is elongated, broader at the middle than at either end and is situated on the side of the laterally bound perineum
- -> it arises by tendinous and fleshy fibres from the inner surface of the ischial tuberosity, behind the crus clitoridis, from the surface of the crus and from the adjacent portions of the ischial Ramus
Deep muscle -> pubococcygeus
4
Q
What does the anal triangle include?
A
- anal canal
- anal sphincters
- ischioanal fossae
5
Q
Describe the anal canal
A
- the rectum terminates in the anal canal
- it is surrounded by an inner epithelial lining, a vascular subepithelium, the internal anal sphincter, the external anal sphincter and fibromuscular supporting tissue
- the proximal anal canal is lined with rectal mucosa (columnar epithelium) and is arranged in vertical mucosa folds (columns of Morgagni)
- each column contains a terminal radical of the superior rectal artery and vein
- the vessels are largest in the left-lateral, right-posterior and right-anterior quadrants of the wall of the anal canal where the supepithelial tissues expand into 3 anal cushions
- -> these cushions seal the anal canal and help maintain continence of flatus and liquid stools
- the columns are joined together by anal valves
- since the epithelium in the lower canal is well supplied with sensory nerve endings, acute distension or invasive treatment of haemorrhoids in this area causes profuse discomfort, whereas if treatment is carried out in the upper canal lined by columnar epithelium few symptoms are experienced
- as a result of tonic circumferential contraction of the sphincter, the skin is arranged in radiating folds around the anus (anal margin)
6
Q
Describe the anal sphincter complex
A
- the anal sphincter complex consists of the EAS and IAS separated by the conjoint longitudinal coat
- external anal sphincter
- -> compromises of striated muscle and appears red in colour
- -> as the EAS is usually under tonic contraction it tends to retract when completely torn - internal anal sphincter
- -> the IAS is a thickened continuation of the circular smooth muscle of the bowel and ends with a well-defined rebounded edge 6-8mm above the anal margin at the junction of the superficial and subcutaneous part of the EAS
- -> the IAS has a pale appearance to the naked eye - longitudinal layer and the conjoint longitudinal coat
- -> situated between the EAS and IAS and consists of a fibromuscular layer, the conjoint longitudinal coat and the interspincteric space with its connective tissue components - nerve supply from branches of the pudendal nerve
7
Q
Describe the ischioanal fossa
A
- it extends around the anal canal and is bound anteriorly by the perineal membrane, superiorly by the fascia of the levator ani muscle and medially by the EAS complex at the level of the anal canal
- it contains fat and neurovascular structures including the pudendal nerve and the internal pudendal vessels
8
Q
What are the different stages of perineal trauma that can occur?
A
- superficial -> grazes to the skin where the epidermis has split owing to the pressure of distension, they require no treatment but can be uncomfortable and stinging due to the disruption of nerve endings
- first degree -> a tear in the skin and underlying superficial tissues, often the wound will heal spontaneously as the skin edges are usually in apposition, tears on the labia minora (well innervated area) can cause a lot of discomfort, if bilateral tears are present suturing may be considered as the labia can fuse together
- second degree -> tear involving perineal muscles, usually sutured
- episiotomy -> surgical incision to enlarge the vaginal opening to facilitate the delivery of the baby, usually performed mediolateral
- third degree -> muscle of the anal sphincter is involved, obstetric repair is essential
- fourth degree -> anal sphincter may become completely divided
