Overview:Digestion and Absorption

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McCafferty

Digestion & Absorption: Overview

Digestion: breakdown of nutrients in the GI tract– Mechanical and chemical

Absorption: transfer of nutrients through the wall of the GI tract, into circulation

Involved in D&A– GI tract

– Auxiliary organs:

________________________________

Pancreas:

– Exocrine function:

– Endocrine function:

Liver: (many functions…)

– Digestive function:

Gallbladder

–

Digestion Mouth

– Mechanical action: biting, chewing– Chemical action:

• Saliva -• Enzymes –

Esophagus– Passage tube to stomach only– Muscular contractions propel food down

•

Stomach– Mechanical “churning” and peristalsis

– Chemical:

• water

• enzymes

• HCl = –

–

Semi-liquid _______________– Released into small intestine in small

amounts

Small Intestine– Most digestion and absorption occur

here

– Peristalsis and Segmentation• chyme mixed with more enzymes

• bicarbonate (to reduce acidity), and

• bile (involved in fat absorption) “Lower” small intestine:

–

–

Large Intestine (Colon): – Removes excess

water and salts (electrolytes), forms feces.

Rectum and Anus:– Feces is held in

rectum until eliminated through the anus.

Absorption

Most absorption occurs in the small intestine… so let’s go back to the small intestine for a moment…

Small intestine wall – thousands of folds

Nutrients pass through the intestinal cells and then into blood or lymph – Capillaries:

– Lymph vessels:

Now we have all the nutrients on the inside of the body. – In the next section, we’ll learn all about

1)carbohydrates,

2) digestion and absorption of CHO, and

3) utilization of CHO once inside the body.