Advanced External Anal Sphincter Quiz

Q1. A lesion of the inferior rectal nerves would most directly weaken which muscle?

• Rectal circular smooth muscle
• External anal sphincter
• Detrusor
• Internal anal sphincter

Q2. Why can injury to the pudendal nerve contribute to fecal incontinence?

• It can weaken voluntary contraction of the external anal sphincter
• It eliminates all rectal peristalsis
• It blocks arterial blood flow to the rectum
• It removes the smooth muscle of the internal anal sphincter

Q3. Which feature allows the external anal sphincter to provide conscious reinforcement of continence?

• Its smooth muscle and autonomic innervation
• Its parasympathetic ganglia
• Its skeletal muscle and somatic motor innervation
• Its glandular epithelium

Q4. A tear involving the perineal body can compromise the anterior support of which part of the external anal sphincter?

• Superficial part
• Subcutaneous part only
• Rectal longitudinal muscle only
• Internal anal sphincter only

Q5. Which anatomical relationship explains why the deep external anal sphincter and puborectalis function as a closely integrated unit?

• Both muscles arise from the obturator membrane
• The deep sphincter blends with puborectalis
• Both muscles are smooth muscle
• Puborectalis forms the internal anal sphincter

Q6. During voluntary defecation, which coordinated muscular change facilitates opening of the anorectal passage?

• Relaxation of the external anal sphincter and puborectalis
• Contraction of piriformis and obturator internus
• Relaxation of all abdominal muscles with contraction of the sphincter
• Maximal contraction of the external anal sphincter and puborectalis

Q7. The external anal sphincter differs most fundamentally from the internal anal sphincter in which characteristic?

• Location within the pelvis
• Presence of blood vessels
• Association with the gastrointestinal tract
• Muscle type and neural control

Q8. A patient can generate normal rectal contractions but cannot voluntarily tighten the anus. Which structure is most likely dysfunctional?

• Rectal muscularis
• External anal sphincter
• Sigmoid mesocolon
• Superior rectal artery

Q9. Which component of continence is most specifically provided by tonic and voluntary activity of the external anal sphincter?

• Somatic reinforcement of anal canal closure
• Mucosal absorption of water
• Production of the rectoanal inhibitory reflex
• Autonomic contraction of rectal smooth muscle

Q10. Which statement best integrates the anatomy and function of the external anal sphincter?

• It is a somatically innervated skeletal muscle complex that surrounds the anal canal and contributes to voluntary continence
• It is a fascial structure that passively closes the rectum
• It is a sensory nerve complex supplying the perianal skin
• It is an autonomically controlled smooth muscle thickening of the rectal wall