Chap 22 – Digestive System

Learning Objectives

1. Describe peristalsis.

2. Identify the structures & explain the functions of each organ in the GI tract as well as accessory digestive organs.

3. Be able to explain some of the hormones that act in the process of digestion, their site of production, and target organs.

4. Explain chemical digestion of carbohydrates, proteins, lipids, and nucleic acids.

5. Compare & contrast absorption with malabsorption regarding nutrients.

6. Be familiar with numerous intestinal disorders discussed in class.

Begin reading Chap 22. Review Lecture notes & all practice activities.

Where It All Begins

When you were younger, did you ever hear something similar to this?

“Now, chew your food carefully BEFORE you swallow…”

(What do you think the reasoning was behind that statement?)

Swallowing video: http://video.google.com/videoplay?docid=4375530805602416900

Food Moves Down the Esophagus into the Stomach via Peristalsis

Peristalsis = __________________________?

*NOTE: Peristalsis is so strong that once food or liquid is swallowed, it will reach your stomach even if you stand on your head!

Digestion Begins in the Mouth

• __________ – chewing (_________) & tooth action breaks apart food

• _________ – saliva in mouth begins digesting ____; forms soft bolus (food ball)

Research Item – Take a minute to check it out!

What is Saliva composed of? Read the 2 paragraphs entitled

the Composition of Saliva”, page782. Note your findings to

share with the class.

Getting to Know Your GI OrgansInstructions: Match the

functions with the intestinal organ.

Write only the letter

of the answer.

Reference, pg 810.

Functions Answer Choices (Organs)

1. Releases bi-carbonate rich juices that help to neutralize acidic chyme

a. mouth

2. Stores bile and releases it to assist small intestine as needed for lipid digestion

b. esophagus

3. Mechanical digestion & propulsion; peristalsis waves mix food with gastric juice

c. stomach

4. Primary site for most absorption of nutrients; slow digestion takes place here

d. liver

5. Saliva & mechanical action begins digestive process

e. gallbladder

6. Food tube that carries bolus from mouth to stomach; first sit of peristalsis

f. pancreas

7. Removes most of the remaining water/ liquid from digesting food

g. small intestine

8. Produces bile h. large intestine

GI Tract & Primary Organs, pg. 773• Label your

practice diagram (except for the 3 “crossed out” structures).

PREDICT• To be presented in class

Stomach• To keep from

digesting itself, the stomach has a ______ _______ with:– A thick coat of

bicarbonate-rich mucus on the stomach wall

– Gastric glands that have cells impermeable to HCL

• Damaged epithelial cells are _______ replaced

Gastric pits in the mucosa of the stomach secrete HCL; lined with chief cells that secrete pepsinogen (Protein digesting enzyme)

Gastric pits

Problem: Tummy Trouble

A patient is complaining of gnawing upper abdominal pain that appears 1-3 hours after eating. The patient mentions that they seem to feel temporarily better after eating again. (NOTE: This has been ongoing for at least 4-6 months)

What might be the problem? What is the possible cause?

What Does the Stomach Do?

• The stomach:– Holds ingested food like a _____ _______ (6-

10 inches in length)– Degrades this food both _________ (mixing &

churning) and __________– Delivers chyme to the small intestine– Begins ______ digestion with ________– Secretes intrinsic factor required for

absorption of vitamin B12 – Sends liquids onward to the small intestine;

will retain solids until they are broken apart

http://video.google.com/videoplay?docid=3349901498863881080&q=stomach+view+on+endoscope&total=9&start=0&num=10&so=0&type=search&plindex=0

Stomach 101• Label your practice diagram – ONLY structures circled in red.

I Can’t Believe I Ate The Whole Thing

• Stomach usually empties __ hours after eating

• A meal high in fat may take up to __ hours

• ___ _______ meal empties quickest (which is why you feel hungry again)

Review1. Saliva begins digesting ________ in the

mouth?

2. Chief cells in the stomach mucosa secrete ________________ which act on _______?

3. Anatomical curve taking food ‘downward’ away from the stomach and into the small intestine?

Small Intestine & Associated Structures• Body’s most major digestive organ - accomplishes virtually all ___________ of liquids & nutrients

- as chyme enters the duodenum: Carbohydrates and proteins are only partially digestedNo _____ digestion has taken place

- has an extensive surface area that is made even more vast by _____ & ________________

Villi & Microvilli continued… Label your diagram (pg. 800) with the following: villi,

microvilli, lacteal, intestinal crypt, duodenal glands

Associated Organs

Small intestine completes digestion with the help of __ other organs