GENERAL INFORMATION
The sphincter ani externus is the region between the pubic symphysis and the coccyx, located between the thighs. It 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, as well as defecation.
SPHINCTER ANI EXTERNUS
The external anal sphincter is a muscle located in the perineum. It forms a circular band around the anus and helps control the opening and closing of the anal canal.
ORIGIN
The external anal sphincter muscle originates from the central tendon of the perineum, which is located near the coccyx.
INSERTION POINT
The sphincter ani externus inserts into the skin surrounding the anus.
MAJOR ARTERIES
The sphincter ani externus receives its blood supply from the inferior rectal artery, a branch of the internal pudendal artery.
NEURAL INNERVATION
The perineum is innervated by the inferior rectal nerve, a branch of the pudendal nerve (S2-S4).
TRIGGER POINT
Trigger points in the sphincter ani externus muscle can cause pain and dysfunction, such as anal fissures or difficulty with bowel movements.
CONCENTRIC FUNCTION
During contraction, the sphincter ani externus muscle tightens, closing the anus and maintaining continence.
ECCENTRIC FUNCTION
The eccentric function of the external anal sphincter occurs during relaxation. It allows the anus to open for the passage of stool during defecation.
ISOMETRIC FUNCTION
The external anal sphincter also contracts isometrically to maintain continence when intra-abdominal pressure increases, such as during coughing or sneezing.
RELATED MUSCLE SCIENTIFIC NAMES
- Sphincter ani externus: This muscle is essential for controlling the passage of stool through the anal canal by tightening and relaxing as needed.
ANTAGONIST MUSCLES
- Puborectalis: This muscle helps maintain continence by forming a sling around the rectum, pulling it forward to close the anal canal.
- Levator ani: This group of muscles supports pelvic organs and assists in maintaining continence by working in opposition to the sphincter ani externus.
COMMON INJURIES
- Anal fissures: Small tears in the lining of the anus, causing pain and bleeding.
- Hemorrhoids: Swollen veins in the lower rectum or anus, leading to discomfort and bleeding.
- Perineal tears during childbirth: Tears in the sphincter ani externus occur during vaginal delivery, varying in severity.
EXERCISES
- Kegel exercises: Strengthen the pelvic floor muscles by contracting and relaxing them repeatedly.
- Squats: Engage the perineal muscles and improve pelvic stability by lowering the body into a seated position and standing up.
- Pelvic floor muscle exercises: Improve perineal strength and control through targeted contractions and relaxations.
- Bridge pose: Strengthens the pelvic floor and gluteal muscles by lifting the hips off the ground while lying on the back.
- Lunges: Enhance pelvic stability and engage the perineal muscles by stepping forward and lowering the body.
STRETCHES
- Butterfly stretch: Stretches the inner thighs and perineal muscles by sitting with the soles of the feet together and gently pressing the knees towards the ground.
- Happy baby pose: Releases tension in the sphincter ani externus and lower back by lying on the back and holding the feet with the hands while drawing the knees towards the chest.
- Seated forward fold: Stretches the hamstrings and perineal area by sitting with the legs extended and reaching forward towards the feet.
- Child’s pose: Stretches the sphincter ani externus and relaxes the pelvic floor muscles by kneeling and bending forward to rest the forehead on the ground.
- Deep squat stretch: Stretches the perineal muscles and enhances flexibility by squatting deeply with the feet flat on the ground.