The Pancreas Butts In

As pictured in Figure 14.5, the pancreatic (pan-kree-AT-ik) duct extends from the pancreas and merges with the base of the common bile duct. The pancreatic duct is the main passageway for the pancreatic juice. Surrounding both of them at their point of union is the hepatopancreatic (heh-PAT-oh-pan-kree-AT-ik) sphincter. The hepatopancreatic sphincter is a ring of smooth muscle that regulates the empyting of both the common bile duct (the hepatic or ''liver'' portion) and the pancreatic duct into the small intestine.

When this sphincter (muscular ring) relaxes, bile and pancreatic juice flow through the duodenal (dew-AH-deh-nal) papilla (pah-PIL-lah). The duodenal papilla is a ''little nipple or pimple'' (papill)-like projection with a hole in its center. Bile from the liver, as well as pancreatic juice from the exocrine gland portion of the pancreas (Chapter 10), drip into the duodenum through the hole in the duodenal papilla.

The pancreatic juice contains sodium bicarbonate (buy-KAR-buh-nayt), symbolized chemically as NaHCO3, as well as a variety of digestive enzymes. These enzymes include amylases (starch-splitters), lipases (LIE-pay-sez) or ''fat-splitters,'' and proteases (PROH-tee-ay-sez) or ''protein-splitters.'' The lipases, for example, complete the chemical digestion of fat or lipids, after they have been emulsified by bile into a fatty foam. The resulting products, such as fatty acids and the substance glycerol (GLIH-sir-ahl), are then absorbed across the walls of the small intestine, and into the bloodstream.

Similarly, the proteases continue the chemical breakdown of proteins into amino acids, which are also absorbed into the bloodstream. And the amy-lases in the small intestine generally finish the chemical breakdown of carbohydrates into simple sugars such as glucose, which are then absorbed.

Capsulizing the small intestine's absorption of nutrients:

Organ 2

NUTRIENTS Simple sugars + Amino acids + ABSORBED (such as glucose) (from proteins)

Fatty acids & glycerol (from fats)

IN THE SMALL INTESTINE:

Organ 2

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