Muscles of Abdomen and Pelvis Flashcards
External Oblique
O - 8 fleshy slips from the outer surfaces of middle of shaft of lower 8 ribs. Fibres run downards, forwards and medially.
I - Most fibres of muscle end in a broad aponeurosis through which it is inserted into xiphoid process, linea alba, pubic symphysis, pubic crest and pectineal line of pubis. Lower fibers inserted directly into Anterior 2/3rd of outer lip of iliac crest.
NS - T6-T12
Other imp points
1. The upper four slips of origin of the muscle
interdigitate with those of the serratus anterior; and
the lower four slips with those of the latissimus dorsi.
2. The junction of the muscle fibres with the
aponeurosis lies:
a. Medial to a vertical line drawn from the ninth
costal cartilage in the upper part.
b. Below a line joining the anterior superior iliac
spine to the umbilicus. Above the ninth costal
cartilage, the line curves upwards and medially.
3. Between the anterior superior iliac spine and the
pubic tubercle, the aponeurosis has a free inferior
border that is folded on itself to form the inguinal
ligament.
4. Between the linea semilunaris and the linea alba, the
aponeurosis helps to form the anterior wall of rectus
sheath.
5. Just above the pubic crest, the aponeurosis of the
external oblique muscle presents a triangular
aperture called the superficial inguinal ring
6 The muscle has free posterior and upper borders.
Internal Oblique Muscle
O - Lateral 2/3rd of inguinal ligament, anterior 2/3rd of intermediate area of iliac crest and thoracolumbar fascia. Upwards, forwards, medially
I - Upper most fibres directly into lower 3-4 ribs and their costal cartilages. Greater part of muscle ends as aponeurosis through which inserted into 7th,8th and 9th costal cartilages, xiphoid process, linea alba, pubic crest and pectineal line of pubis. (DOESNT EXTEND BEYOND COSTAL MARGIN)
NS- T7-T12, L1
Other Points
1. The junction of the muscle fibres with the
aponeurosis is roughly at the lateral border of the
rectus abdominis.
2. The aponeurosis takes part in the formation of rectus
sheath as follows. Up to the lateral margin of rectus
abdominis, the aponeurosis has only one layer.
Thereafter, the arrangement of aponeurosis differs in
its upper and lower parts.
a. In the upper three-fourths of the wall, the
aponeurosis splits into an anterior lamina that
passes medially in front of the rectus abdominis;
and a posterior lamina that lies behind the rectus.
The posterior lamina ends below, at the level
midway between the umbilicus and the pubic
symphysis, in a free curved margin called the
arcuate line or linea semicircularis, or fold of Douglas.
The line is concave downwards.
b. Below a level midway between the umbilicus and
the pubic symphysis (lower one-fourth of the
wall), the aponeurosis remains a single layer. It
passes in front of rectus abdominis to reach linea
alba. It, thus, takes part in forming the anterior
wall of rectus sheath.
3 The conjoint tendon is formed partly by this muscle.
4 The cremaster muscle is formed by fibres of this
muscle.
