This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdominal wall ,Inguinal and Femoral region, Subject name: Anatomy
Function of external oblique muscle: 
Select and explain. 
A. Anterior flexion of veebral column, B. Active expiration, C. Closure of inguinal ring, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: External oblique: Most superficial muscle which originates from the outer pa of the 5th to 12th ribs on each side of the rib cage. This muscle then runs diagonally down each side and connects to the iliac crest, linea alba, and the pubis. Function: External oblique contributes to the maintenance of abdominal tone, increasing intra-abdominal pressure (as in active expiration), and lateral flexion of the trunk against resistance. Bilateral contraction flexes the trunk forward and aid in movement of spine and back. Contraction of external oblique muscle approximates the two crura (medial and lateral) of superficial inguinal ring like a slit valve to maintain the integrity of inguinal canal.