Abdomen Anatomy and Function

Abdomen

The abdomen refers to the portion of the trunk that connects the thorax and pelvis. It is the region between the ribs and the pelvis, encased by skin, fascia, and muscles, forming the abdominal wall. The abdominal wall provides a scaffold for the development and functioning of the abdominal viscera and offers physical protection to the organs.

Abdominal Cavity

The abdominal cavity is the space enclosed by the abdominal wall and contains the foregut, midgut, and hindgut, which are part of the digestive system. The abdominal cavity is also home to several vital organs such as the liver, stomach, pancreas, and small and large intestines. The abdominal cavity is filled with peritoneal fluid which acts as a lubricant for the internal organs and helps them move smoothly within the cavity.

Abdominal Organs

The abdominal organs are primarily involved in the digestive and excretory functions of the body. They include the liver, which has a dual role in bile production and amino acid synthesis; the pancreas, which produces digestive enzymes; the stomach, which breaks down food through acidic secretion; the small intestine, where the majority of nutrient absorption occurs; and the large intestine, which aids in the absorption of water and electrolytes and stores fecal matter until defecation. The kidneys, located in the posterior abdomen, are responsible for regulating the body's electrolyte and water balance.

Abdominal Muscles

The abdominal muscles are a group of muscles that support the trunk, allow movement, and help maintain internal abdominal pressure. They consist of five large, paired muscles, including the external oblique, internal oblique, transversus abdominis, rectus abdominis, and pyramidalis.

The external oblique muscle originates from the fifth to twelfth ribs and inserts at the pubic tubercle and anterior half of the iliac crest. It is responsible for compressing the abdominal viscera and is involved in flexing and rotating the trunk.

The internal oblique muscle originates from the thoracolumbar fascia, anterior two-thirds of the iliac crest, and inferior borders of the tenth-twelfth ribs. It supports the viscera and has minimal movement responsibility.

The transversus abdominis muscle originates from the internal surfaces of the seventh to twelfth costal cartilages, thoracolumbar fascia, iliac crest, and lateral third inguinal ligament. Its main roles are to stabilize the trunk and maintain internal abdominal pressure.

The rectus abdominis muscle is slung between the ribs and the pubis at the thoracolumbar junction. It is responsible for movement of the trunk between the ribcage and the pelvis and is responsible for the characteristic bumps or bulges in the abdominal region.

The pyramidalis muscle is a small, flat muscle located in the anterior abdominal wall. Its primary function is to support the lower abdominal viscera.

In addition to these muscles, the multifidus muscle, a deep back muscle that runs along the spine, works together with the transversus abdominis to increase spine stability and protect against back injury or strain during movement.

Together, these muscles contribute to the core muscles, which provide stability and balance to the body and protect the spine.