The Digestive SystemTiffany AguilarAria DavisDaidreana PaytonMary Starks

Anatomy and PhysiologyBlock C13 May 2009

Villi & Microvilli• Vascular projections from

the mucous membrane of the small intestine

• Shapes:▫ Short and leaf shaped

(duodenum)▫ Tongue shaped

(jejunum)• Slow passage of food so

the nutrients in the food is absorbed

Villi & Microvilli: Structure

•Structure:▫Lacteal: rich capillary bed and a modified

lymphatic capillary▫Vessels▫Epithelium▫Basement membrane: surround lacteal,

muscular tissue, and blood vessels▫Muscular tissue of mucosa▫Held together by retiform lymphoid tissue

The Anatomy of the Stomach• The stomach is a C-Shaped

organ and holds a principal role in digestion. The stomach is about 25 centimeters long. When the stomach has reached its maximum capacity it can hold 4 liters or 1 gallon of food. When empty the stomach collapses in to itself. Most of the digesting occurs in the pylorus region.

• The stomach is composed of a couple of major regions▫ The Cardiac Region ▫ The fundus ▫ The Body ▫ The Pyloric Antrum▫ The Pylorus

What does the stomach do?• The stomach is used to help digest particles of

food.• With the strong muscles contained in the

stomach; the stomach is easily able to physically breakdown food along with mixing and churning the food. The stomach is also a place where the chemical breakdown of proteins begins.

• The stomach secretes gastric juice made up of hydrochloric acid, pepsin, and rennin to begin the process.

• The stomach churns and mixes the solutions with the food particles and it becomes chyme and proceeds into the small intestine.

The Anatomy of the Small Intestine • The Small Intestine is the

major digestive organ of the body. It is also the longest and most convoluted of all organs. The Small Intestine can average a length of 2.5 to 7 meters long or 8 to 18 feet.

• The Small Intestine is composed of three main parts▫ The Duodenum▫ The Jejunum ▫ The Ileum

What goes on in the Small Intestine?• The Small Intestine’s main purpose is to

chemically digest food. • The food, or chyme, comes into the first part of

the Small Intestine, the Duodenum, small portions at a time. Once full, the process begins. Pancreatic enzymes and bile are added to the food particles and begin to churn and mix to further breakdown the food and access nutrients.

• As the broken down food travels down the jejunum and the ilium, and eventually to the large intestine, villi and microvilli are able to absorb nutrients.

What is the Large Intestine (Colon)?• The colon is a tube 6 cm wide and 1.5 m long

located between the small intestine and the rectum.

• Its main purpose is to process remaining undigested chyme into feces.

• The colon’s exocrine glands secrete a viscous mucous that aids to mold the solid fecal matter and protect the colon wall from possible mechanical damage by the moving and churning solid contents.

• There are four main segments: Ascending, Transverse, (site of water and sodium absorption) Descending, and Sigmoid (storage of fecal matter).

How does the Large Intestine (Colon) work?• Peristalsis waves

force dehydrated feces along the colon at regular intervals (2-3 daily movements after meals).

• On average it takes 1-3 days for complete digestion of food.

• 1 Liter of water is absorbed daily in this process so drink up!

Rectum

•Continuous with the sigmoid colon and extends to the anus

•Stores solid waste until it leaves the body through the anus

•The colon and the rectum form the large intestine▫Colon is the first 6 feet▫Rectum is the last 8 to 10 inches

The Liver• The liver is the largest gland in the body, located under the diaphragm to the right

of the body. It has 4 lobes and is attached to the stomach by a mesentery cord called the falciform ligament. It has many metabolic and regulatory functions but one of its main functions is to produce bile, a at-digesting enzyme.

• Without a liver a person would die in 24 hours• The not only produces bile but:

1. Detoxifies drugs and alcohol in the body

2. Degrade ( dilute) hormones

3. Make substances for the body to use such as albumin and cholesterol

• The hepatic portal circulation drains nutritious blood to liver first. The liver cleans out amino acids, fatty acids, and glucose to store them for later and the liver’s phagocytic cells clean out bacteria.

• We have a surplus of liver tissue and the liver is one of the organs in the body that can regenerate rapidly and easily.

The Gallbladder• The gallbladder is a small, thin-walled

green sac that sits in a shallow opening in the inferior surface of the liver.

• When food is not being digested, the bile produced by the liver is goes back up in the cystic duct and is stored in the gallbladder until digestion occurs.

• Bile is a greenish-yellow, watery substance containing bile salts, bile pigments, cholesterol, phospholipids, and electrolytes.

• The phospholipids and bile salts emulsify fats, breaking them down into smaller pieces

• If bile is stored in the gallbladder for too long or becomes too concentrated, it forms gallstones, which are extremely painful. If the bile backs up into the liver, the liver cells press bile salt and pigments into the bloodstream causing jaundice, or yellowing of the tissues.

The Pancreas• The pancreas is a soft, pink, triangular gland

that extends across the abdomen form the spleen to the duodenum.

• It produces enzymes that breakdown all categories of digestible foods

• It also produces hormones called insulin and glucagon, this is related to diabetes

• The pancreas’ enzymes flow through the pancreatic ducts to the hepatopancreatic ampulla or “the liver-pancreatic enlargement” where bile and pancreatic fluids meet. After the two fluids pass into the duodenum to chemically breakdown substances.

• Alkaline pancreatic juices help make the chyme in the stomach neutralize to make a better place for enzymes to work

Vitamins C, D, and K• Water Soluble: Vitamin C• Vitamin C is involved in the metabolism of cholesterol to bile acids, which

may have implications for blood cholesterol levels and the incidence of gallstones.

• Fat-Soluble: Vitamins D and K▫ Absorbed in the chylomicrons: lipoproteins that transport dietary lipids.

• The major function of vitamin D is to maintain normal blood levels of calcium and phosphorus.

• Vitamin D2 is synthesized by plants.• Vitamin D3 is created when the skin is exposed to UVB rays from the sun.• Individuals who have inflammatory bowel disease (e.g., Crohn's disease)

are at risk for vitamin D deficiency. • Potassium is essential for the functioning of several proteins involved in

blood clotting.• Potassium is secreted in the large intestine causing a depletion during

severe diarrhea.

Metabolism• Refers to all chemical reactions that are necessary to

maintain life▫ Catabolism: substances broken down to smaller

substances▫ Anabolism: larger molecules are built from smaller

ones• Carbohydrates are broken down to make ATP• Fats are used to build cell membranes, make myelin

sheaths, insulate the body, and to produce ATP when no carbohydrates are in the diet

• Proteins are carefully conserved by body cells because they are the major structural materials used for building cell structures

Works Cited• Higdon, Jane . "Vitamin K." Oregon State University. May 2004.

Micronutrient Information Center. 10 May 2009 <http://lpi.oregonstate.edu/infocenter/vitamins/vitaminK/>.

• Higdon, Jane . "Vitamin C." Oregon State University. January 2006. Micronutrient Information Center. 10 May 2009 <http://lpi.oregonstate.edu/infocenter/vitamins/vitaminC/>.

• Wagner, CL. "Vitamin D." Mayo Clinic. 2009. Natural Standard. 10 May 2009 <http://www.mayoclinic.com/health/vitamin- d/NS_patient-vitamind>.

• Kapit, Wynn and Lawrence M. Elson. The Anatomy Coloring Book. Glenview: Pearson Education, Inc., 2002.

• Myers, Donna. What is the Rectum. July 2008. May 2009 <http://coloncancer.about.com/od/faqs/f/Rectum.htm>.

• Gray, Henry . Gray's Anatomy. 15th ed. New York: Barnes & Noble, Inc, 1995.

• Marieb, Elaine N. Essentials of Human Anatomy and Physiology. 8th ed. San Francisco: Pearson Education, Inc, 2006.

• Kapit, Wynn and Robert I. Macey and Esmail Meisami. The Physiology Coloring Book. ed. 2. San Francisco: Addison Wesley Longman, Inc., 2000

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