Page 166 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Muscular System / 151

loins. The insertion is by means of a broad the cremaster m., which pulls the testicle
toward the inguinal canal.
flat tendon (aponeurosis) that meets the
VetBooks.ir insertion of the muscle from the opposite the deepest of the abdominal muscles.
The m. transversus abdominis is
side at the linea alba. Caudally, the muscle
is continued by an aponeurosis, some­ It originates from the deepest layer of
times called the inguinal ligament, at the thoracolumbar fascia, and the fibers are
junction of abdominal wall to pelvic limb. directed perpendicular to the long axis of
This ligament forms the superficial wall of the body to insert on the linea alba.
the inguinal canal for the passage of the The m. rectus abdominis forms the
spermatic cord of the male. It contains a muscular floor of the abdomen. It originates
slit, the superficial inguinal ring, through from the cartilages of the ribs and the
which the spermatic cord passes from the sternum. The fibers run directly caudad in
inguinal canal into the scrotum. a horizontal plane to attach to the pubis
The internal abdominal oblique m. by means of a strong prepubic tendon.
(m. obliquus internus abdominis) is The m. rectus abdominis characteristically
immediately deep to the external abdomi­ is divided by a series of tendinous inter-
nal oblique muscle. Its fibers pass obliquely sections. The ventral aponeuroses of the
ventrad and craniad, and the muscle also other abdominal muscles form a dense con­
inserts on the linea alba by means of an nective tissue envelope, the rectus sheath,
aponeurosis. In some animals, this muscle surrounding the m. rectus abdominis.
forms the deep wall of the inguinal canal
and also part of the deep inguinal ring.
The most caudal group of fibers from the Muscles of Respiration
internal abdominal oblique muscle passes
through the inguinal canal with the spermatic The muscles of respiration are either
cord and attaches to the outer covering of expiratory, forcing air out of the lungs by
the testicle. This slip of muscle constitutes decreasing the size of the thorax, or

L1

Rib 13

Cupula of diaphragm

Figure 7-19. Projection of the diaphragm into the thoracic region. Because of the shape of the diaphragm,
a significant percentage of abdominal contents lie under the cover of the ribcage.