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7/28/2019 Sistem Penghadaman (BI)

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Digestive System


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Announcements

Exams

Lab notes will be on reserve in library and

on the web


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Goals of the Digestive System

1. Extract nutrients from food

2. Transform nutrients into useful forms

Ex- oreo= glucose

3. Absorb nutrients and distribute them

where they are needed


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Functions of the Digestive

System Ingestion: intake of nutrients

Digestion: breakdown of large particles intosmaller ones

Absorption: uptake of nutrient molecules

Defecation: elimination of undigested residues


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Actions of the Digestive

System

1. Motility- Breaks up food

- Moves food through the GI tract (Peristalsis)

- Mixes with digestive enzymes

2. Secretion- Release of enzymes and hormones for chemical

digestion and regulation

3. Membrane Transport- Absorption of nutrients from the tissues by the

blood and lymph for transport


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Stages of Digestion

Mechanical: physical breakdown of food

Chemical: digestive enzymes hydrolyze foodparticles to break larger molecules into smaller

ones

Some nutrients are absorbed with out digestion

Vitamins, minerals, cholesterol, water


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Anatomy of the Digestive

System Oral Cavity

Pharynx

Esophagus

Stomach

Pyloric Sphincter

Small Intestine Large Intestine


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Accessory Organs

Teeth

Tongue

Salivary Glands

Liver Gall Bladder

Pancreas


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Oral Cavity Functions:

A. Ingestion: cheeks lipsand tongue mobilize food

B. Digestion: Mechanical

Mastication

Chemical

3 salivary glands

Digests some

starches and fat


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Pharynx

Motility: pharyngeal

constrictors force food

down duringswallowing


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Esophagus

Straight muscular tube

about 1 foot long

Motility: muscularcontraction moves

food towards stomach

www.mywebmd.ca.com


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Heartburn and the EsophagusHeartburn, acid reflux, is caused by acid and food

going from the stomach into the esophagus

The diaphragm normally prevents acid reflux, inconjunction with the lower esophageal sphincter.

When this fails, the burning sensation felt is known

as heartburn

May be linked to a rare type of cancer,adenocarcinoma


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Stomach

Muscular sac on the left

side of the peritoneal

cavity

Functions:

Food storage

Mechanical digestion Chemical digestion


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Rugae in the Stomach

Rugae- folds in the

stomach lining that

allow it to expand withmore food

How do we vomit?

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion


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Pyloric Sphincter

Ring of smooth

muscle

Regulates the passage

of material from the

stomach into the

duodenum

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion


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Digestion in the Stomach

Mechanical Digestion:

Muscular contraction

Chemical Digestion:

Secretes digestive enzymes and HCl


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Small Intestine

http://www.afns.ualberta.ca/bbo/1/ANATOMY/SI1.asp

2 meters long, 1 inch

in diameter, 5-6

meters in cadaver

Functions:

Chemical Digestion

Nutrient Absorption

Motility


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Anatomy of the Small Intestine

Duodenum (25 cm):

1. Receives stomach

contents, pancreaticjuice and bile

2. Neutralizes stomach

acid and pepsin

3. Pancreatic enzymesand bile take over

chemical digestion

Fig 25.22


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Anatomy of the Small Intestine

Jejunum (2.5m)

Ileum (3.6 m) Reabsorbs bile acids


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Functions of the Small

Intestine Motility: smooth muscle

contract

Digestion: chemicalenzymes received fromthe pancreas, liver and gall

bladder

Nutrient reabsorption:

microvilli increase surfacearea

Microvilli


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Dynamic Human: Microvilli


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Large Intestine

Functions

Motility

Reabsorbtion of Water and Electrolytes

Symbiotic bacteria Synthesis Vitamins B & K


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Anatomy of the Large

IntestineTransverse Colon: right to left

Ascending Colon: Descending Colon:

up the right side down the left side

Cecum: sac on Sigmoid Colon:

lower right side S-shaped


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Enzymes Involved in

Chemical Digestion Saliva:

Amylase: breaks down starch

Lipase: breaks down fats when it enters thestomach

Low pH of the stomach activates the enzyme


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Enzymes Involved in

Chemical Digestion Stomach:

Digestive chemicals-

HCL: activates enzymes, breaks up foods

Pepsin: digests proteins

Renin: digests milk


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Pepsin Formation

Interactions between Cells

Chief Cells make pepsinogen

Parietal Cells make HCl Pepsinogen is cleaved by HCl into Pepsin


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Dynamic Human: Pepsin

Formation


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Enzymes Involved in

Chemical Digestion Small Intestine

Two sources of

enzymes

Liver and Gall bladder

Pancreas


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Enzymes Involved in

Chemical Digestion in the

Small IntestineLiver secretes bile that is active in the small

intestine

Bile: aids in fat digestion and absorptionActivates pancreatic enzymesSynthesized from cholesterolBacteria in the small intestine use bilirubin to

make your feces brown

Gall bladder stores and concentrates bile


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Gall Stones

What is a gall stone?

How do they treat gall stones?

How is the gall bladder removed?


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Enzymes Involved in

Chemical Digestion in the

Small Intestine

Pancreas: secretes pancreatic juice

1. Amylase: breaks down starch2. Lipase: breaks down fats

3. Ribonuclease (RNAase): breaks down RNA

4. Deoxyribonuclease (DNAase): breaks downDNA

5. Zymogens: inactive enzymes that activate in the

small intestine


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Mechanism of Absorption

Membrane Transport:

Nutrients pass through membrane surface

The greater the membrane surface area, thegreater the amount of nutrients that can be

transported

Surface Area Rugae

Microvilli


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Final Destinations of Digestion

Products Starches bloodstream

Fats lymph vessels (lacteals)

Proteins bloodstream


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Dynamic Human:

Visualization


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Cat Dissection

Be able to locate and

identify

Esophagus Stomach

Small Intestine

Large Intestine

Ascending colon

Transverse colon

Descending colon

Also know accessory

organs

Tongue Teeth

Gall Bladder

Liver


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Conclusion

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