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The Digestive System

Ch 35-1 NWRC BIO 30

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Video on Digestion

http://uk.youtube.com/watch?v=sCn5uvvc3WE&feature=relatedhttp://uk.youtube.com/watch?v=sCn5uvvc3WE&feature=related

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The esophagus is the

first part of thedigestive tract..

Approximately 10

inches in length, it

consists of three tissuelayers consistent with

the rest of the gut.The

muscles of peristalsis

begin propelling the

food bolus through the

esophagus into the

stomach.

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What stops food going

the wrong way!

The swallowing reflex

is activated by the

pushing of food to the

back of the throatfood is swallowed into

the esophagus. The

epiglottis covers the

trachea so food doesnt

go the wrong way

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The

Stomach

Very acidic

environment

(enzyme)pepsin

breaks

down

proteins

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The Stomach

The stomach is a C-shaped pouch that receives the

food bolus from the esophagus. It aids both in

mechanical and chemical digestion. Acting like achurn, the stomach mixes the food with gastric

acid and breaks down the food into a milky

substance known as chyme. The acid reduces the

pH of the stomach, in the process allowingactivation of an enzyme called pepsin. This starts

the chemical digestive process.

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The Stomach

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Small intestineThe majority of digestion occurs

in the small intestine. This

compartment has three distinctportions, each of which is highly

specialized for different digestive

functions. VIDEO

http://uk.youtube.com/watch?v=xu5jDCX2cHM&feature=relatedhttp://uk.youtube.com/watch?v=xu5jDCX2cHM&feature=related

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The small Intestine

The small intestine is the longest portion of the

digestive tract - it is more than 6-7 meters long

and is located within the middle of the abdomen. Ithas three sections, the duodenum, jejunum and

ileum

Digestion of fats, proteins and carbohydrates

contained in the foods you consume, is completedwithin the small intestine.

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The Small Intestine

The lining of the small

intestine secretes a

hormone calledsecretin, which

stimulates the

pancreas to produce

digestive enzymes.

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The pancreas

Digestive enzymes are released from the

pancreas to enable the degradation process.

Bile is released from the gall bladder andmixes with the chyme to aid in fat digestion

and absorption.

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The Liver

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The LiverThe liver is the largest

glandular organ of the body. It

weighs about 3 lb (1.36 kg). It

is reddish brown in color andis divided into four lobes of

unequal size and shape. The

liver lies on the right side of

the abdominal cavity beneaththe diaphragm.

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The Liver

Some of the functions are: to produce

substances that break down fats,

convert glucose to glycogen, produce

urea (the main substance of urine),make certain amino acids (the building

blocks of proteins), filter harmful

substances from the blood (such as

alcohol), storage of vitamins and

minerals) and maintain a proper level

or glucose in the blood.

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The Gall Bladder

The gallbladder is

about 10-12 cm long in

humans and appearsdark green because of

its contents (bile),

rather than its tissue. It

is connected to the liver

and the duodenum

(small intestine)

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The Gall Bladder

The gallbladder stores

about 50ml of bile

which is released whenfood containing fat

enters the digestive

tract.

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The Gall BladderThe bile, produced in theliver, emulsifies fats and

neutralizes acids in partly

digested food.

After being stored in the

gallbladder, the bile becomes

more concentrated than

when it left the liver,increasing its potency and

intensifying its effect on fats.

Most digestion occurs in the

duodenum

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The Large Intestine

The large intestine (the colon) has several majorcomponents. The cecum is the entrance to the right side ofthe colon. There is a circular muscle, or sphincter, that

separates the small intestine from the large intestine. Thesphincter protects the small intestine from the concentrated

bacteria of the large intestine. Following the cecum, theascending colon rises up and leads into the transversecolon. From there, the descending colon dives back down

on the left side of the abdomen into the sigmoid colon andrectum. Waste is finally eliminated through the anus.

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Assessment

1. Digestion begins in

mouth, continues in

stomach and ends insmall intestine

Each type of molecule

is broken down into its

simplest part thoroughthe use of enzymes.

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Assessment

2. Mechanicaldigestion such aschewing grinds foodinto smaller particles

Chemical digestion byacids and enzymeschanges foodchemically such as

breaking proteinsdown into amino acids

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Assessment

3. the 3 main functions

are to

A. ingest food B. break it down

C. eliminate what

cannot be digested

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Assessment

4. The villi increase

the surface area so that

more nutrients can beabsorbed, if the lining

was smooth fewer

nutrients would be

absorbed

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Extra Review

Link to printable worksheetstest yourself!

http://www.wikieducator.org/Digestive_System_Worksheethttp://www.wikieducator.org/Digestive_System_Worksheet