L42 The Perineum and External Genitalia Flashcards
What is the perineum divided into?
Urogenital triangle and an anal triangle
What is the ischioanal fossa and what are its boundaries?
The space between the ischium and the anal canal. It is a fat filled space. It is important as it allows the anus to expand during defecation.
Medially: Anal Canal
Laterally: Muscles of the Levator ani
Inferiorly: A layer of fat and skin
What passes through the ischioanal fossa?
Going through the ischial anal fossa is the pudendal neurovascular bundle. The pudendal nerve gives off a branch that supplies the external anal sphincter - the inferior rectal nerve. The inferior rectal artery is given off from the internal pudendal artery. The pudendal nerve is also important in the external urethral sphincter and also supplies branches of the levator ani. It helps with continence and keep the pelvic structures in the pelvis. It comes from S2-4.
Give details of the innervation of the anal canal?
The anal sphincter is a complex. There is an internal anal sphincter - which is smooth muscle that forms some of the rectal and anal wall. It is under autonomic control.
Control from the superior rectal and hypogastric plexuses
There is also an external anal sphincter - fails safe mechanism. This is made of straited muscle - it is under somatic control. You can contract the external anal sphincter. This is also a complex. There are different parts - a deep part, a superficial and a subcutaneous part just underneath the skin.
Control from the Inferior rectal nerve (somatic control)
What is the urogenital diaphragm composed of?
Separating the perineum pouches from one another is a urogenital diaphragm. The inferior edge of the urogenital diaphragm is formed from the perineum membrane (the membrane between the ischial tuberosities). Just superior to the perineal membrane is a layer of straited muscle. The medial most part of the straited muscle forms the external urethral sphincter. Sat just on top of the muscle is a layer of loose connective tissue.
Superior to this is an anterior extension of the sischioanal fossa.
What is the perineal membrane?
The urogenital triangle is covered by the perineal membrane. The external genitalia are hung from the perineal membrane. In the female, the attachment point is called the labia majora. In the male it is called the bulbous root of the penis. It almost covers the entirely of the urogenital triangle. The opening is for the urethra (and vagina). Where the perineal membrane attaches is the ischium - the ischial pubic ramus. Posteriorly there is a free edge. It is a point of attachment for the external genitalia. It separates the external; genitalia from a superficial part and a deep part.
What is found within the deep perineal pouch?
Deep perineal pouch – a potential space between the deep fascia of the pelvic floor (superiorly) and the perineal membrane (inferiorly). It contains part of the urethra, external urethral sphincter, and the vagina in the female. In males, it also contains the bulbourethral glands and the deep transverse perineal muscles
What is found within the superficial perineal pouch?
Superficial perineal pouch – a potential space between the perineal membrane (superiorly) and the superficial perineal fascia (inferiorly). It contains the erectile tissues that form the penis and clitoris, and three muscles – the ischiocavernosus, bulbospongiosus and superficial transverse perineal muscles. The greater vestibular glands (Bartholin’s glands) are also located in the superficial perineal pouch. The pouch is bounded posteriorly to the perineal body.
How does the penis become erect?
When the corpus spongiosum fills with blood, the penis becomes turgid and the corpus spongiosum straightens out for ejaculation.
What does the corpus spongiosum from?
The glands penis on the distal part of the penis. It also forms the ventral surface of the penis and the bulb of the penis.
What three chambers is the penis made from?
The penis is made up of three chambers - 2 corpora cavinosa which will fill with blood and on the ventral surface corpus spongiosum .
Which chamber does the penile urethra flow through?
Corpus spongiosum
What are the muscles covering the erectile tissue?
Around the bulb of the vestibule and the bulb of the penis is the bulbospongiosus muscle. The bulbospongiosus muscle the male covers the proximal part of the corpus spongiosum. The female, the bulbospongiosus muscle covers the bulb of the vestibule. Covering the corpora cavernous on either side is the ischialcarvernosus muscle. n the male the bulbospongiosus muscle is also important in micturition. Some males, as they get older, can suffer from post-micturition drippling.
All theses muscles do is keep blood in the erectile tissue.
What forms the clitoris?
The glands clitoris is formed by the corpus spongiosum. The aura and the body of the clitoris is formed by the corpora cavernous.
What is the path of the internal pudendal artery?
The internal pudendal leaves via the greater sciatic foreman and goes underneath the sacrospinous ligament and enters the perineum. Some branches supply the anal sphincter, some to the levator ani and some into the penis. A branch of the internal pudendal is in the erectile tissue - in the corpora cavernous.
