Advanced Internal Anal Sphincter Quiz

Q1. A patient has normal voluntary contraction of the external anal sphincter but markedly reduced resting anal pressure. Dysfunction of which structure should be considered?

• Obturator internus
• Piriformis
• Internal anal sphincter
• Gluteus maximus

Q2. Which response normally follows distension of the rectal wall during the rectoanal inhibitory reflex?

• Permanent external anal sphincter paralysis
• Transient internal anal sphincter relaxation
• Closure of the sigmoid colon
• Maximal internal anal sphincter contraction

Q3. Which clinical condition classically involves absence of the normal rectoanal inhibitory reflex because of distal intestinal aganglionosis?

• Inguinal hernia
• Obturator neuropathy
• Hirschsprung disease
• Femoral neuropathy

Q4. Why does pudendal nerve injury not directly denervate the internal anal sphincter?

• The internal sphincter is controlled primarily by autonomic and enteric pathways
• The internal sphincter is supplied by the femoral nerve
• The internal sphincter is supplied by the obturator nerve
• The internal sphincter has no neural regulation

Q5. Which mechanism allows continence to be maintained temporarily after reflex relaxation of the internal anal sphincter?

• Relaxation of the pelvic floor
• Contraction of the external anal sphincter and puborectalis
• Contraction of the detrusor muscle
• Relaxation of the external anal sphincter

Q6. Which component of the continence mechanism is most directly lost if the internal anal sphincter is severely damaged?

• Somatic sensation of perianal skin
• Formation of the pelvic diaphragm
• Voluntary contraction of skeletal muscle
• Involuntary resting anal tone

Q7. Which anatomical distinction explains why the internal anal sphincter cannot be voluntarily contracted in the same manner as the external anal sphincter?

• It is part of the pudendal nerve
• It is composed of dense irregular connective tissue
• It lacks muscle fibers
• It is smooth muscle with autonomic and enteric control

Q8. A surgical procedure that divides part of the internal anal sphincter is most directly altering which tissue?

• Striated puborectalis fibers
• Obturator fascia
• Skeletal fibers of the external anal sphincter
• Circular smooth muscle

Q9. Which combination of sphincter behavior is most appropriate during normal voluntary defecation?

• Contraction of both internal and external anal sphincters
• Permanent internal sphincter contraction with puborectalis contraction
• Internal sphincter contraction with external sphincter relaxation
• Relaxation of both internal and external anal sphincters

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

• It is a sensory structure responsible for detecting pain below the pectinate line
• It is an involuntary smooth muscle sphincter that provides resting anal tone and relaxes reflexively with rectal distension
• It is a fascial sling responsible for creating the anorectal angle
• It is a voluntary skeletal muscle supplied primarily by the pudendal nerve