A hernia is any condition in which the viscera protrude through a weak point in the muscular wall of the abdominopelvic cavity. The most common type to require treatment is an inguinal hernia. In the male fetus, each testis descends from the pelvic cavity into the scrotum by way of a passage called the inguinal canal through the muscles of the groin. This canal remains a weak point in the pelvic floor, especially in infants and children. When pressure rises in the abdominal cavity, it can force part of the intestine or bladder into this canal or even into the scrotum. This also sometimes occurs in men who hold their breath while lifting heavy weights. When the diaphragm and abdominal muscles contract, pressure in the abdominal cavity can soar to 1,500 pounds per square inch—more than 100 times the normal pressure and quite sufficient to produce an inguinal hernia, or "rupture." Inguinal hernias rarely occur in women.

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

352 Part Two Support and Movement

Trapezius -


External intercostals

Erector spinae: Spinalis thoracis Iliocostalis thoracis Longissimus thoracis

Latissimus dorsi

Iliocostalis lumborum Thoracolumbar fascia

External intercostals

Latissimus dorsi

Iliocostalis lumborum Thoracolumbar fascia

Intercostals Cadaver

Figure 10.19 Deep Back Muscles of the Cadaver.

Two other sites of hernia are the diaphragm and navel. A hiatal hernia is a condition in which part of the stomach protrudes through the diaphragm into the thoracic cavity. This is most common in overweight people over 40. It may cause heartburn due to the regurgitation of stomach acid into the esophagus, but most cases go undetected. In an umbilical hernia, abdominal viscera protrude through the navel.

Before You Go On

Answer the following questions to test your understanding of the preceding section:

12. Which muscles are used more often, the external intercostals or internal intercostals? Explain.

13. Explain how pulmonary ventilation affects abdominal pressure and vice versa.

14. Name a major superficial muscle and two major deep muscles of the back.

15. Define perineum, urogenital triangle, and anal triangle.

16. Name one muscle in the superficial perineal space, one in the urogenital diaphragm, and one in the pelvic diaphragm. State the function of each.

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    Which muscles are used more often, the external intercostals or internal intercostals Explain.?
    5 years ago

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