Large Intestine and Umbilical Hernias
by Robert Tallitsch, PhD | October 6, 2022
Video with Patient Case Example of Umbilical Hernias and Explanation of the Large Intestine!
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Written by: Robert Tallitsch, PhD
A hernia is defined as a protrusion of an organ or any part of an organ through a weakness or gap in the abdominal wall. The National Institutes of Health estimates that approximately 2% of the adult population within the United States will develop a hernia of some sort within their lifetime. Umbilical hernias are a specific type of hernia in which the patient has an imperfect closure or weakness of the umbilical ring, resulting in a protrusion of abdominal contents (a portion of the small or large intestine) through the umbilicus. (For the anatomy of the small intestine please visit the Small Intestines and Celiac Disease Brain Builder.) In this Brain Builder we will discuss the anatomy of the large intestine, the anatomy of the umbilical ring, and the cause, symptoms, and treatment of an umbilical hernia.
Gross Anatomy of the Large Intestine (Colon)
The function of the large intestine is the reabsorption of water from the semi-solid chyme that exits the small intestine. This results in the formation of feces that will be temporarily stored within the distal portions of the large intestine before it is removed from the body via the anal canal.
Externally the large intestine possesses the following three gross anatomical characteristics:
- Significantly larger diameter than the small intestine
- Teniae coli, which are three distinct, visible bands of smooth muscle located within the muscularis externa of the intestinal wall.
- Haustra, which are sacculations of the intestinal wall located between the teniae coli.
The large intestine is subdivided into the following segments:
- Cecum and the associated appendix
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Anal canal
The cecum, which is the first portion of the large intestine, is a blind-ended pouch. It is continuous with the terminal segment of the ileum proximally, and the ascending colon distally. It is located within the iliac fossa, in the lower right quadrant of the abdominal cavity.
The appendix (vermiform appendix) is a small, tubular appendage located off of the posteromedial side of the cecum. The appendix is rich in lymphatic tissue and often becomes clogged with fecal matter, which may lead to appendicitis.
The ascending colon ascends on the right side of the abdominal cavity, and often comes into contact with the inferior surface of the right lobe of the liver deep to the 9th and 10th ribs. Here the ascending colon turns left at the right colic flexure (hepatic flexure) and becomes the transverse colon.
The transverse colon, which is the longest and most mobile segment of the large intestine, crosses the abdomen cavity from the right to left, inferior to the diaphragm. The transverse colon ends at the left colic flexure (splenic flexure) anterior to the inferior portion of the left kidney.
The descending colon begins at the left colic flexure, and ends at the sigmoid colon as it passes anteriorly to the lateral border of the left kidney.
The s-shaped sigmoid colon is continuous proximally with the descending colon and distally with the rectum, at approximately the level of the 3rd sacral vertebra.
The rectum and anal canal are the terminal portions of the colon. The anal canal possesses two sphincters, which are circular bands of muscle. The internal anal sphincter is an involuntary sphincter composed of smooth muscle, and is controlled by the autonomic nervous system. Sympathetic stimulation closes the internal anal sphincter, while parasympathetic stimulation relaxes the sphincter, allowing the passage of fecal material distally to the location of the external anal sphincter.
The external anal sphincter is a ring of striated muscle controlled by the voluntary somatic nervous system. Stimulation of the inferior rectal nerve causes contraction of this sphincter, preventing the passage of fecal material through the terminal portion of the anal canal.
Linea Alba and the Umbilical Ring
The linea alba is a sheath of connective tissue that runs vertically from approximately the level of the 5th costal cartilage to the pubic symphysis. This piece of connective tissue separates the right and left rectus abdominis muscles, and carries nerves and blood vessels to the anterior abdominal wall. Approximately at its midpoint the linea alba lies deep to the umbilicus and contains the umbilical ring. The umbilical ring is an interruption of the linea alba, and is the structure through which the umbilical vessels pass to and from the umbilical cord and placenta of the developing fetus. As a result the umbilical ring is an inherent weak spot within the linea alba and the anterior abdominal wall.
Umbilical hernias are the most common form of hernia seen in infants and young children. Although less common, umbilical hernias are also seen in adults – especially adults that are overweight or obese, have a persistent cough, routinely lift heavy objects, or have given birth to twins or triplets.
An umbilical hernia typically presents as a painless lump at or near the umbilicus (navel) that often gets larger while laughing, coughing, crying, or defecation. Umbilical hernias are often painless in newborns or young children and, in infants or young children, an umbilical hernia will often “go back in” and the muscles of the umbilical ring will reseal before the age of 5 or 6 years. Umbilical hernias that develop during the adult years typically cause abdominal discomfort, and need to be watched carefully. The risk of complications from an umbilical hernia increases with the size of the hernia. In adults umbilical hernias often require surgical repair.
Surgical repair of an umbilical hernia is typically done under general anesthetic and involves the movement of the protruding abdominal contents back into the abdominal cavity and a strengthening of any weaknesses in the abdominal wall. Umbilical hernias may be repaired either by open or laparoscopic surgical procedures. Umbilical hernia repair is a simple and safe procedure. Seldom is a second procedure required provided that the patient follows their physician’s post-surgical orders — especially those pertaining to heavy lifting and possible reduction in overall body weight.
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