Name: small and large intestine functions
Uploaded: 2019-03-11T09:21:25.000Z
Duration: 1 min 23 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Human Anatomy and Physiology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.HA.1.10

Anatomy of the Intestines

The small and large intestines are responsible for absorbing nutrients and water.
While the small intestine is rather narrow, the organ is approximately 22 feet long and compacted into the abdominal cavity. Chyme first reaches the duodenum and then travels to the middle part, the jejunum.
Here, the inner lining contains mucosal folds, which are covered in finger-like villi. The overlying layer of epithelial cells have cytoplasmic extensions called microvilli. These three structures increase the surface area of the small intestine to ensure that nutrients are optimally absorbed.
At the end of the small intestine is the ileum, which attaches to the large intestine by the ileocecal valve. In the first part of the large intestine, the cecum, there are no folds or villi.
Dangling at the bottom of the cecum, is the appendix, a small lymphatic structure. Above it, starts the ascending colon, followed by the transverse colon, which absorbs most of the remaining water and electrolytes, turning chyme into feces. The last regions, the descending colon, sigmoid colon, and rectum, store feces until elimination through the anus.

anatomy of the intestines

Although digestion of proteins, carbohydrates, and lipids may begin in the stomach, it is completed in the intestine. The absorption of nutrients, water, and electrolytes from food and drink also occurs in the intestine. The intestines can be divided into two structurally distinct organs&#8212;the small and large intestines.
<h4>Small Intestines</h4>
The small intestine is an ~7&#160;meter-long tube with an inner diameter of just 2.5 cm. Since most nutrients are absorbed here, the inner lining of the small intestine is highly convoluted and covered in finger-like extensions called villi, each containing hundreds of microvilli. The folds, villi, and microvilli of the small intestine amplify the surface area of absorption 60 to 120 times. The increased surface area provides ample opportunity for nutrients to be absorbed.
The small intestine connects to the stomach by the pyloric sphincter, which closes off when chyme moves into the duodenum&#8212;the beginning of the small intestine. The middle part of the small intestine is the jejunum. The ileum ends the small intestine, where it attaches to the large intestine by the ileocecal valve.
<h4>The Large Intestines</h4>
The large intestine starts at the cecum. The appendix, a small lymphatic structure, dangles from the bottom of the cecum. Above the cecum, starts the ascending colon followed by the transverse colon. They absorb most of the remaining water and electrolytes from the chyme, turning it into feces. The descending colon, sigmoid colon, and rectum store feces until elimination through the anus.
Overall the large intestine is about 1.5 m long with an inner diameter of 4.8 cm. It does not contain folds and villi, but the absorptive epithelial cells have microvilli. The large intestine is home to a bacterial ecosystem, which performs the final stages of digestion&#8212;breaking down cellulose and fiber, compounds which the stomach and small intestine are ill-equipped to process.
<h4>Bacterial Diversity</h4>
The large intestine contains over 700 different species of bacteria. Bacterial diversity is thought to be related to obesity and the development of Type 2 diabetes. Obese individuals have fewer bacterial strains than their non-obese counterparts. Low bacterial diversity has also been associated with insulin resistance. The intestinal bacterial ecosystem&#8212;the gut biome&#8212;is established shortly after birth, with those babies being breastfed developing their gut biome from bacteria present in breast milk. After birth, the biome is shaped by an individual&#8217;s genetics, diet, age, sex, and immune system. External factors like diet, health status, medications, and geographical location also significantly influence the complexity of the gut biome.

Although digestion of proteins, carbohydrates, and lipids may begin in the stomach, it is completed in the intestine. The absorption of nutrients, water, ...

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JoVE Core

Biology

Human Biology

Nutrition and Digestion

KEY TERMS AND CONCEPTS

small and large intestine functions

The small and large intestines complete digestion and absorb nutrients, water, and electrolytes. They are two structurally distinct organs with different shapes and jobs. Together, they move food material from the stomach toward elimination.

The small intestine is about 7 meters long and has an inner diameter of only 2.5 cm. Most nutrient absorption happens here, so its inner lining is highly folded and covered with villi, which are finger-like projections. Each villus contains hundreds of microvilli, and the folds, villi, and microvilli increase the surface area for absorption by 60 to 120 times.

The small intestine connects to the stomach through the pyloric sphincter. When chyme moves into the duodenum, which is the start of the small intestine, this sphincter closes off. The middle section is the jejunum, and the ileum is the final part. The ileum joins the large intestine at the ileocecal valve.

The large intestine begins at the cecum. The appendix, a small lymphatic structure, hangs from the bottom of the cecum. Above it are the ascending colon and then the transverse colon. These sections absorb most of the remaining water and electrolytes from chyme and help turn it into feces.

The descending colon, sigmoid colon, and rectum store feces until they leave the body through the anus. The large intestine is about 1.5 m long and has an inner diameter of 4.8 cm. Unlike the small intestine, it does not have folds or villi, although its absorptive epithelial cells do have microvilli.

The large intestine also supports a bacterial ecosystem that carries out the final stages of digestion. These bacteria can break down cellulose and fiber, which the stomach and small intestine are not well equipped to process. The large intestine contains over 700 different species of bacteria, and this diversity may be linked to obesity and Type 2 diabetes. People with obesity tend to have fewer bacterial strains than people who are not obese, and low diversity has also been associated with insulin resistance.

The gut biome is established shortly after birth. Babies who are breastfed develop it from bacteria present in breast milk. After birth, genetics, diet, age, sex, and the immune system help shape the biome. External factors such as diet, health status, medications, and geographical location also affect how complex the gut biome becomes.

Small and Large Intestine Functions

overview of human digestion

Saliva, Stomach Acid, and Gut Health

The human digestive system is monogastric, which means the stomach has one chamber for digestion. Several other animals also have monogastric digestive systems, including pigs, horses, dogs, and birds. This chapter focuses on the human digestive system. Saliva is a watery fluid released by the salivary glands into the mouth. It is about 99.5% water and also contains electrolytes, mucus, white blood cells, epithelial cells, enzymes, and antimicrobial agents. The enzymes in saliva begin...

The small and large intestines complete digestion and absorb nutrients, water, and electrolytes. They are two structurally distinct organs with different shapes and jobs. Together, they move food material from the stomach toward elimination. The small intestine is about 7 meters long and has an inner diameter of only 2.5 cm. Most nutrient absorption happens here, so its inner lining is highly folded and covered with villi, which are finger-like projections. Each villus contains hundreds of...

accessory organs

Digestive Glands and Enzymes

Digestive glands and accessory organs help break down food even though food does not pass through them. They add enzymes and other fluids to the digestive tract to support digestion. The salivary glands release saliva, a fluid that contains water, mucus, and amylase. Amylase is a digestive enzyme that starts breaking down starches and other carbohydrates before food reaches the stomach. The liver, gallbladder, and pancreas also support digestion. They send their secretions into the duodenum,...

lipid digestion

Lipases and Bile in Fat Breakdown

Lipases and bile help the body break down lipids, which are large molecules that do not mix well with water. Because most digestive enzymes are water-based, lipids need special steps before the body can use them. Lingual lipase is an enzyme made by acinar cells in the sublingual gland. It is found in saliva, but it has only a small role in the mouth. Its best pH, or acidity level, is 3.5-6.0, so it becomes active after chewed food reaches the acidic stomach. Gastric lipase is another acidic...

protein digestion

Protein Breakdown and Amino Acid Use

Protein digestion starts in the stomach, where strong acid helps unfold protein structure and expose peptide bonds in polypeptide chains. Digestive enzymes then begin breaking those chains into smaller pieces that can be processed by the body. Pepsin is a protease, which means it is a protein-digesting enzyme. It is made in the stomach and works with chymotrypsin and trypsin, enzymes released in the small intestine. These enzymes cut specific links between amino acids and form shorter...

carbohydrate digestion

Carbohydrate Breakdown in the Digestive Tract

Carbohydrate digestion breaks food carbohydrates into saccharides, or sugars, that the body can use for energy. It begins in the mouth during mastication, which means chewing. The masticated carbohydrates then pass through the stomach without being broken down further. Digestion starts again in the duodenum, the first part of the small intestine. There, pancreatic alpha-amylase and brush border enzymes on the microvilli help convert complex carbohydrates into monosaccharides. These simple...

neural regulation

Brain and Gut Control of Digestion

Brain and gut control digestion through a cephalic phase and the enteric nervous system. The cephalic phase begins when the brain sees or smells food. It sends impulses through cranial nerves to the salivary glands and stomach so the body is ready to eat. This first response is a conditioned, or learned, reaction to familiar foods. Appetite also changes the response. People may make more saliva and hear more stomach rumbling when they think about apple pie than broccoli. The hypothalamus and...

hormonal regulation

Digestive Hormones and Stomach Control

Digestive hormones control when the stomach makes acid and when food moves into the small intestine. They work with the neuroendocrine system, which links nerve signals and hormone release during digestion. In the stomach, proteins are detected by sensory neurons in the enteric nervous system. This stimulates the pyloric gland to release gastrin. Gastrin then helps trigger histamine release, and together they start hydrochloric acid production. The acid helps break food down into chyme. As the...

key terms and concepts

Explore how the small and large intestines absorb nutrients, water, and electrolytes, and learn how gut bacteria help finish digestion in high school biology.

Small and Large Intestine Functions | JoVE K12

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biology

Next Generation Science Standards

High School

Life Science

HS-LS1-2

Florida Department of Education

SC.912.L.14

SC.912.L.14.45

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New York State Science Learning Standards

Structure and Function

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9-12.HA.1.1

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2. Obtain, evaluate, and communicate information to describe how the structures of the integumentary system and its accessory organs contribute to its function. Examples: how the layers of the skin contribute to homeostasis, the role of glands in thermoregulation and in hydration of skin and mucous membranes, the protective functions of hair and nails

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a. Construct an explanation of the relationships between the integumentary system and other organ systems, including the body's mechanisms for maintaining homeostasis. Examples: Explain how changes in vessel diameter and evaporation of water over the skin contribute to thermoregulation (cardiovascular). Explain how sweat is used to excrete nitrogenous waste from the blood (cardiovascular). Explain how the skin and mucous membranes create a barrier against infection (immune system).

9-12.HA.1.2.a

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3. Develop and use a model to illustrate how the structures of the skeletal system contribute to its function. Examples: Create a diagram or 3D model to illustrate bone shape, joint types, and bones in the appendicular and axial skeletons. Use models to illustrate the role of the skeletal system in movements around joints, support of a body structure, and protection of soft tissues.

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9-12.HA.1.3.a

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9-12.HA.1.3.b

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Naming Skeletal Muscles

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9-12.HA.1.4

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a. Model the cellular physiology of skeletal muscle, including how the cell functions in muscle contraction and relaxation. Example: Use straws and paper to create a model of a sarcomere to illustrate how the fibers move during contraction and relaxation.

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9-12.HA.1.4.b

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Small and Large Intestine Functions

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