Suffixes

Combining Forms

Throat

The throat, or pharynx (FAIR inks), is a tube that connects the oral cavity with the esophagus. It can be divided into three main parts: the nasopharynx, the oropharynx, and the hypopharynx. The nasopharynx (nay soh FAIR inks) is the most superior part of the pharynx, located behind the nasal cavity. The oropharynx (oh roh FAIR inks) is the part of the throat directly adjacent to the oral cavity, and the hypopharynx (hye poh FAIR inks) (also called the laryngopharynx) is the part of the throat directly below the oropharynx (Fig. 5-2, B).

Esophagus

The esophagus (eh SAH fah gus) is a muscular, mucus-lined tube that extends from the throat to the stomach. It carries a masticated lump of food, a bolus (BOH lus), from the oral cavity to the stomach by means of peristalsis. The glands in the lining of the esophagus produce mucus, which aids in lubricating and easing the passage of the bolus to the stomach. The muscle that must relax before the food enters the stomach is known by three names: the lower esophageal (eh sah fah JEE ul) sphincter (SFINK tur) (LES), the gastroesophageal sphincter, or the cardiac sphincter, which gets its name because of its proximity to the heart. Sphincters are ringlike muscles that appear throughout the digestive and other body systems.

Stomach

The stomach, where digestion begins, is an expandable vessel, which is divided into three sections: the top, or fundus (FUN dus); the body; and the muscle between the stomach and first part of the small intestine, or pylorus (pye LORE us) (also called the gastric antrum) (Fig. 5-3). The portion of the stomach that surrounds the esophagogastric connection is the cardia (KAR dee ah). The fundus is the area of the stomach that abuts the diaphragm. This section of the stomach has no acid-producing cells, unlike the remainder of the stomach. The body, or corporis, is the central part of the stomach, and the pylorus (pl. pylori) is at the distal end of the stomach, where the small intestine begins. A small muscle, the pyloric sphincter, regulates the gentle release of food from the stomach into the small intestine. When the stomach is empty, it has an appearance of being lined with many ridges. These ridges, or wrinkles, are called rugae (ROO jee) (sing. ruga).

The function of the stomach is to temporarily store the chewed food that it receives from the esophagus. This food is mixed with gastric juices and hydrochloric acid to further the digestive process chemically. This mixture is called chyme (kyme). The smooth muscles of the stomach contract to aid in the mechanical digestion of the food. A continual coating of mucus protects the stomach and the rest of the digestive system from the acidic nature of the gastric juices.

Small Intestine

Once the chyme has been formed in the stomach, the pyloric sphincter relaxes a bit at a time to release portions of it into the first part of the small intestine, called the duodenum (doo AH deh num). The small intestine gets its name, not because of its length (it is about 20 feet long), but because of the diameter of its lumen (LOO mun) (a tubular cavity within the body). The second section of the small intestine is the jejunum (jeh JOO num) and the distal part of the small intestine is the ileum (ILL ee um).

Multiple circular folds in the small intestines, called plicae (PLY see), contain thousands of tiny projections called villi (VILL eye) (sing. villus), which contain blood capillaries that absorb the products of carbohydrate and protein digestion. The villi also contain lymphatic vessels, known as lacteals (LACK tee uls), that absorb lipid (LIH pid) substances from the chyme. A lipid is a fatty substance.

The suffix -ase is used to form the name of an enzyme. It is added to the name of the substance upon which the enzyme acts: for example, lipase, which acts on lipids, or amylase, which acts on starches. -ose is a chemical suffix indicating that a substance is a carbohydrate, such as glucose.

Large Intestine

In contrast to the small intestine, the large intestine or colon (Fig. 5-4) is only about 5 feet long, but it is much wider in diameter. The primary function of the large intestine is the elimination of waste products from the body. Some synthesis of vitamins occurs in the large intestine, but unlike the small intestine, the large intestine has no villi and is not well suited for absorption of nutrients. The ileocecal (ILL ee oh SEE kul) valve is the exit from the small intestine and the entrance to the colon. The first part of the large intestine, the cecum (SEE kum), has a wormlike appendage, called the vermiform appendix (VUR mih form ah PEN dicks) (pl. appendices), dangling from it. Although this organ does not seem to have any direct function related to the digestive system, it is thought to have a possible immunologic defense mechanism.

No longer called chyme, whatever has not been absorbed by the small intestines is now called feces (FEE sees). The feces pass from the cecum to the ascending colon (KOH lin), through the transverse colon, the descending colon, the sigmoid colon (the S-shaped part of the large intestine), and on to the rectum (the last straight part of the colon), where they are held until released from the body completely through the anus (the final sphincter in the GI tract.) The process of releasing feces from the body is called defecation, or a bowel movement (BM).

Accessory Organs (Adnexa)

The accessory organs are the gallbladder (GB), liver, and pancreas (Fig. 5-5). These organs secrete fluid into the GI tract but are not a direct part of the tube itself. Sometimes accessory structures are referred to as adnexa (ad NECK sah).

The two lobes that form the liver (LIH vur) virtually fill the right upper quadrant of the abdomen and extend partially into the left upper quadrant directly inferior to the diaphragm. The liver filters and stores blood and forms a substance called bile, which emulsifies (ee MUL sih fyez), or mechanically breaks down, fats into smaller particles so that they can be chemically digested. Bile is composed of bilirubin (BILL ee roo bin), the waste product formed by the normal breakdown of hemoglobin in red blood cells at the end of their life spans, and cholesterol (koh LESS tur all), a fatty substance found only in animal tissues. Bile is released from the liver through the right and left hepatic ducts, which join to form the hepatic (heh PAT ick) duct. The cystic (SISS tick) duct carries bile to and from the gallbladder. When the hepatic and cystic ducts merge, they form the common bile duct, which empties into the duodenum. Collectively, all of these ducts are termed bile vessels. Bile is stored in the gallbladder (GALL blad ur), a small sac found on the underside of the right lobe of the liver. When fatty food enters the duodenum, a hormone called cholecystokinin (koh lee sis toh KYE nin) is secreted, causing a contraction of the gallbladder to move bile out into the cystic duct, then the common bile duct, and finally into the duodenum.

The pancreas (PAN kree us) is a gland located in the upper left quadrant. It is involved in the digestion of the three types of food molecules: carbohydrates, proteins, and lipids. The pancreatic enzymes are carried through the pancreatic duct, which empties into the common bile duct. Pancreatic involvement in food digestion is an exocrine (ECK soh krin) function because the secretion is into a duct. Pancreatic endocrine (EN doh krin) functions (secretion into blood and lymph vessels) are discussed in Chapter 15.