The Large Intestine In The Digestive System – The large intestine lies below the stomach and liver and almost completely encloses the small intestine. The muscle fibers of the colon form three distinct bands called teniae coli that run the length of the colon and exert tension, creating a series of pouches called haustra, which incise into the intestinal lumen. The folds between the haustra affect the mucosa and create a series of internal folds. The haustra allows for the expansion and lengthening of the colon. Epiploic appendages are small sacs of visceral peritoneum filled with fat that hang from the surface of the colon. They are unknown functions. The large intestine consists of the cecum, large intestine, rectum and anal canal. FIGURE 24-16 shows the large intestine.

At the beginning of the large intestine, the cecum is an enlarged sac-like structure that hangs below the ileocecal opening. A narrow tube extending downward from the cecum is the appendix or vermiform appendix, which is usually about 9 cm long. The size and shape of the appendix can vary significantly. The small mesentery, which is a two-layered hanging peritoneal tissue called the mesoappendix, connects the appendix to the ileum and cecum. The mucosa and submucosa of the appendix are dominated by lymphoid nodes, and the main function of the appendix is ​​as an organ of the lymphatic system. This structure has a closed end and has no established function related to digestion, but is partially composed of lymphatic tissue.

The Large Intestine In The Digestive System

The next part of the large intestine is the large intestine, which has a larger diameter and thinner walls than the small intestine. The large intestine consists of four parts:

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■■ Ascending colon: Begins at the cecum, continues upward along the posterior abdominal wall, inferior to the liver, and then turns sharply to the left at the right colic or hepatic flexure.

■■ Transverse colon: The longest, most mobile part, it is suspended by a fold of the peritoneum and bends in the middle, below the stomach; near the spleen, it turns sharply downward at the left colic or splenic flexure.

■■ Descending colon: A mostly vertical section that makes an S-shaped curve near its lowest point at the sigmoid flexure.

■■ Sigmoid colon: The last part, which is only 15 cm or 6 inches long, that becomes the rectum. The sigmoid colon lies behind the urinary bladder.

Digestive System: Large Intestine Diagram

The rectum is next to the sacrum and resembles its curvature. It is about 15 cm (6 inches) long and is attached to the sacrum via the peritoneum. The rectum ends about 5 cm below the tip of the coccyx and becomes the anal canal, which consists of the last 2.5-4 cm of the large intestine.

In the anal canal, the mucosa is folded between six and eight longitudinal anal columns. The distal end of the canal opens to the outside as the anus, controlled by two sphincter muscles. The internal muscle of the anal sphincter consists of smooth muscles and is under involuntary control. The external muscle of the anal sphincter consists of skeletal muscles and is under voluntary control.

The large intestine has little or no digestive function. It contains many tubular glands composed almost entirely of goblet cells (FIGURE 24-17). Mucus is the only important secretion of the large intestine and protects the intestinal wall from abrasion and binds particles of fecal matter. Mucus is alkaline, helping to control the pH of the colon.

Chyme in the large intestine contains undigested or unabsorbed materials, as well as electrolytes, mucus, bacteria and water. In the proximal half of the colon, water and electrolytes are absorbed normally. The remaining substances form feces, which are stored in the distal part of the large intestine. The intestinal flora, which is normal bacteria, breaks down some of the molecules that are not digested by the enzymes. An example is cellulose, which moves through the small intestine with little change, but can be broken down by colonic bacteria to be used as energy. These bacteria synthesize vitamins such as cobalamin (B12), vitamins K phylloquinone and menaquinone, riboflavin (B2) and thiamin (B1), which are absorbed by the intestinal mucosa. Bacterial action in the colon can also cause intestinal gas or bloating.

Digestion: Anatomy, Physiology, And Chemistry

Mixing in the large intestine is usually slower than in the small intestine. Peristaltic waves of the colon occur only two to three times a day. The intestinal walls are strongly constricted in mass movements to force the contents towards the rectum. These movements usually follow a meal, but can also be caused by irritation of the intestinal mucosa. Conditions such as colitis or an inflamed colon can also cause frequent mass movements.

The defecation reflex can usually be initiated voluntarily by holding a deep breath and contracting the muscles of the abdominal wall. As the rectum fills, its wall stretches, triggering a defecation reflex. The internal anal sphincter relaxes, the diaphragm descends, the glottis closes, and the muscles of the abdominal wall contract. The pressure in the stomach increases and the rectum is compressed. The external anal sphincter relaxes, and feces are expelled. Defecation can be inhibited by voluntary contraction of the external anal sphincter.

Undigested materials, unabsorbed materials, water, electrolytes, mucus, discarded intestinal cells and bacteria comprise feces. Water makes up about 75% of fecal matter; its color comes from bile pigments that are under the influence of bacterial action. The pungent smell of feces is the result of compounds produced by bacteria. TABLE 24-7 summarizes nutrient absorption. Embark on a fascinating journey through the alimentary canal with our guide to the anatomy and physiology of the digestive system. Nursing students, enjoy the complexity of the processes that turn bites into energy and let curiosity guide your research.

The organs of the digestive system can be divided into two main groups: those that make up the alimentary canal and the auxiliary organs for digestion.

Difference Between Small Intestine And Large Intestine

The alimentary canal, also called the gastrointestinal tract, is a continuous, hollow muscular tube that winds through the ventral body cavity and is open at both ends. Its organs include the following:

The role that teeth play in food processing requires little introduction; we chew or chew by opening and closing the jaws and moving them from side to side while continuously using the tongue to move food between the teeth.

Specifically, the digestive system takes in food (swallows it), breaks it down physically and chemically into nutrient molecules (digests it), and absorbs the nutrients into the bloodstream, then rids the body of indigestible waste (defecates).

Activities that occur in the mouth, pharynx, and esophagus are swallowing food, breaking down food, and propelling food.

Anatomy Of The Abdominal Viscera: Large Intestine

The sight, smell and taste of food stimulate reflexes of the parasympathetic nervous system, which increase the secretion of gastric juice by the gastric glands.

What is finally delivered to the colon contains some nutrients, but that residue has another 12 to 24 hours to spend there.

Age-related changes in the gastrointestinal system include decreased saliva, decreased esophageal and gastric motility, decreased gastric emptying time, decreased intrinsic factor production, and decreased intestinal absorption, motility, and blood flow. In addition, tooth enamel becomes harder and more brittle, making teeth more susceptible to fractures.

Health promotion lessons for the elderly include preventive dental care and effective oral hygiene, proper nutrition and adequate fluid intake, regular bowel maintenance and the importance of colorectal cancer screening.

Extraordinary Facts About Large Intestine (colon)

Marianne leads a double life, working as a nurse during the day and working as a writer at night. As an ambulatory nurse, she honed her skills in providing health education to her patients, making her a valuable resource and study guide writer for future nurses.

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About 15 feet in size, your intestines break down and absorb essential nutrients from food and drink. These nutrients are then transported into your bloodstream.

Your intestines are a key part of your digestive system. They are where most vitamins and nutrients from food are broken down and absorbed into your bloodstream.

Large Intestine 3d Illustration Human Digestive System Anatomy For Medical Concept Stock Photo

Your gut does a lot of work to provide you with the energy and nutrition you need to stay healthy, function and thrive every day.

So, have you ever wondered how your intestines work or how long they are? We’ll help you better understand what your gut is doing.

Your small intestine runs from your stomach to your large intestine. It continues the digestion process that started in your stomach.

Absorption of food occurs in the small intestine. What is left over from this process is then transferred to your large intestine.

Colon: Anatomy, Histology, Composition, Function

It can vary between about 10 feet (3 meters) to over 16 feet (5 meters). In comparison, a standard basketball hoop is 10 feet high.

Different parts of the small intestine are also different lengths. The ileum is the longest part, while the duodenum is the shortest.

Since it’s so long, you might wonder why the small intestine is called “small” in the first place. This terminology actually refers to the diameter of the small

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