GENERAL INFORMATION
The perineum is the region between the pubic symphysis and the coccyx, located between the thighs. Sphincter ani contains various structures, including muscles, nerves, blood vessels, and genitals. The perineum plays a role in supporting pelvic organs and is involved in sexual function, urination, and defecation.
SPHINCTER ANI
The sphincter ani is a muscle located in the perineum. It forms a circular band around the anus and helps control the opening as well as closing of the anal canal.
ORIGIN
The sphincter ani muscle originates from the central tendon of the perineum, which is located near the coccyx.
INSERTION POINT
It inserts into the skin surrounding the anus.
MAJOR ARTERIES
The sphincter ani receives its blood supply from the inferior rectal artery, a branch of the internal pudendal artery.
NEURAL INNERVATION
The sphincter ani is innervated by the inferior rectal nerve, a branch of the pudendal nerve (S2-S4).
TRIGGER POINT
Trigger points in the external anal sphincter muscle can cause pain and dysfunction, such as anal fissures or difficulty with bowel movements.
CONCENTRIC FUNCTION
During contraction, the external anal sphincter muscle tightens, closing the anus and maintaining continence.
ECCENTRIC FUNCTION
The eccentric function of the sphincter ani occurs during relaxation. It allows the anus to open for the passage of stool during defecation.
ISOMETRIC FUNCTION
The sphincter ani also contracts isometrically to maintain continence when intra-abdominal pressure increases, such as during coughing or sneezing.
RELATED MUSCLE SCIENTIFIC NAMES
- Bulbospongiosus: A muscle that contributes to the stability and function of the pelvic floor.
- Ischiocavernosus: Assists in maintaining erection by compressing the veins of the penis or clitoris.
- Superficial transverse perineal muscle: Provides support to the pelvic floor and stabilises the perineum.
- Deep, transverse perineal muscle: Plays a role in supporting the pelvic organs and maintaining continence.
ANTAGONIST MUSCLES
- Puborectalis: Part of the pelvic floor muscles, it helps maintain continence by creating a kink in the anal canal.
- Levator ani: A group of muscles that support the pelvic organs and assist in maintaining continence.
COMMON INJURIES
- Anal fissures: Small tears in the lining of the anus causing pain and discomfort.
- Hemorrhoids: Swollen blood vessels in the rectum or anus, leading to pain, itching, and bleeding.
- Perineal tears during childbirth: Tears in the perineum that can damage the sphincter ani muscle.
EXERCISES
- Kegel exercises: Strengthen the pelvic floor muscles, including the sphincter ani, through contraction and relaxation.
- Squats: Engage the perineal muscles and improve pelvic stability and strength.
- Pelvic floor muscle exercises: Improve perineal strength and control, enhancing overall pelvic health.
STRETCHES
- Butterfly stretch: Stretches the inner thighs and perineal muscles, enhancing flexibility.
- Happy baby pose: Releases tension in the perineum and lower back, promoting relaxation.
- Seated forward fold: Stretches the hamstrings and perineal area, relieving tension.
- Child’s pose: Stretches the perineum and relaxes the pelvic floor muscles, aiding in overall muscle relaxation.