RESUMO
This paper discusses anatomical aspects of internal oblique muscle at the inguino-hypogastric area, particularly of its inferomedial insertion aiming at finding an anatomical substrate which justifies the appearance of direct inguinal hernia. Eighty-four inguino-hypogastric regions were studied in fresh corpes of 20 adult females and 64 adult males. It was noticed that the inferomedial aspect of the internal oblique muscle is either inserted into the pubis or the lateral margin of the recuts abbominis sheath, the former being more frequent: 95,0 per cent in females and 57,82 per cent in males (p<0,05). As far the insertion of the internal oblique muscle into the lateral margin of the recuts abdominis sheath is concerned, the distance between the pubic tubercle and the inferomedial insertion of the muscle is of up to 3,3 cm in males and up to 0,7 cm in females. If only the portion of the internal oblique muscle which does not exhibit gaps is considered, the inferomedial insertion is then located up to 4,5 cm from the pubis in males and up to 2,4 cm in females. The internal oblique muscle wasclassified into five categories according to its dysmorphism and it was noticed that gaps are more frequent in males. The data suggest that the less frequent insertion of the internal oblique muscle into the pubis and also the higher incidence of muscular dysmorphism of this muscle may be factors responsible for the higher frequence of direct hernias in males.