Transcript Overview: Digestion and Absorption

Overview:
Digestion and Absorption
NFSC 303
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
folds


intestine wall – thousands of

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.