digestive system - sf

7/28/2019 Digestive System - Sf

1/26

DIGESTIVE SYSTEM

By Arvina D W


2/26

Food and Nutrition

A. Food and Energy

B. Nutrients

1. Water

2. Carbohydrates3. Fats

4. Proteins

5. Vitamins

6. Minerals

C. Nutrition and a Balanced Diet


3/26

NUTRIENTS

include

include

such as such as

are made of include includeare made using

Nutrients

Carbohydrates Fats MineralsProteins Vitamins

Simple Complex

Amino

acids Calcium Iron

Fatty Acids Glycerol

Sugars Starches Fat-solubleWater-

soluble


4/26

Body mass index

Body mass index (kg/m2) = Weight (kg) / Height (m

2)

Female (kg/m2) Male (kg/m2)

Thin < 17 (kg/m2

) < 18 (kg/m2

)

Normal 17 23 (kg/m2) 18 25 (kg/m2)

Fat 23 27 (kg/m2) 25 27 (kg/m2)

Obesity > 27 (kg/m2) > 27 (kg/m2)

Source : Health Department 2003 See food intake and body weight
http://g/digestion%20for%20sf-usi/Fundamental%20digestive%202/PREGASTRIC%20DIGESTION/foodintake.htmlhttp://g/digestion%20for%20sf-usi/Fundamental%20digestive%202/PREGASTRIC%20DIGESTION/foodintake.html


5/26

Carbohydrates

Carbohydrates

The diversity of dietary carbohydrates necessitates discussion

of several classes of these molecules, ranging from simple

sugars to huge, branched polymers

Monosaccharides or simple sugars are either hexoses (6-carbon) like glucose,

galactose and fructose, or pentoses (5-carbon) like ribose. These are the

breakdown products of more complex carbohydrates and can be efficiently absorbedacross the wall of the digestive tube and transported into blood.

Disaccharides are simply twomonosaccharides linked together by a glycosidic bond. The

disaccharides most important in nutrition and digestion are:

lactose or "milk sugar": glucose + galactose

sucrose or "table sugar": glucose + fructose

maltose: glucose + glucose

Oligosaccharides, which include disaccharides, are relatively short chains of monosaccharides

which typically are intermediates in the breakdown of polysaccharides to monosaccharides.


6/26

Polysaccharides

You should be familiar with three important polysaccharides, each of which is a large polymer of

glucose:

Starch is a major plant storage form of glucose.Cellulose is the other major plant carbohydrate. It is the major constituent of plant cell walls,

and more than half of the organic carbon on earth is found in cellulose. Herbivores subsist

largely on cellulose, not because they can digest it themselves, but because their digestive tracts

teem with microbes that produce cellulases that hydrolyze cellulose.

Glycogen is the third large polymer of glucose and is the major animal storage carbohydrate.

Like starch, the glucose molecules in glycogen are linked together by alpha(1-4) glycosidic

bonds.


7/26

Fatty acids are present in only small amounts in animal and plant tissues, but are the building

blocks of many important complex lipids. True fatty acids possess a long hydrocarbon chain

terminating in a carboxyl group. Nearly all fatty acids have an even number of carbons and havechains between 14 and 22 carbons in length. The principle differences among the many fatty acids

are the length of the chain (usually 16 or 18 carbons) and the positions of unsaturated or double

bonds. For example, stearic acid (pictured below) has 18 carbons and is saturated.

The so-called "short-chain" or volatile fatty acids are 2 to 4-carbon molecules of great importance

in intermediary metabolism and as the mainstay of ruminant nutrition. They are represented by acetic,

butyric and proprionic acids.

The most abundant storage form of fat in animals and plants, and hence the most important dietary

lipid, is neutral fat or triglyceride. A molecule of triglyceride is composed of a molecule of glycerol in

which each of the three carbons is linked through an ester bond to a fatty acid. Triglycerides cannot

be efficiently absorbed, and are enzymatically digested by pancreatic lipase into a 2-monoglyceride

and two free fatty acids, all of which can be absorbed. Other lipases hydrolyse a triglyceride into

glycerol and three fatty acids.

A triglyceride

(triacylglycerol):

tristearin

FATS


8/26

PROTEIN

ProteinsProteins are polymers of amino acids linked together by peptide bonds. Very short proteins,

typically 3 to 10 amino acids in length, are called peptides

Although very small peptides can be absorbed to a limited degree, for all intents and purposes,

proteins must be reduced to single amino acids before they can be absorbed. Enzymes that

hydrolyze peptide bonds and reduce proteins or peptides to amino acids are calledproteases orpeptidases.


9/26

VITAMINS

Vitamin

A (retinol)

D (calciferol)

E (tocopherol)

K

B1 (thiamine)

B2 (riboflavin)

Sources

Yellow, orange, and dark green

vegetables; dairy products

Fish oils, eggs; made by skin

when exposed to sunlight;added to dairy products

Green leafy vegetables, seeds,

vegetable oils

Green leafy vegetables; made

by bacteria that live in human

intestine

Whole grains, pork, legumes,

milk

Dairy products, meats,

vegetables, whole-grain cereal

Function

Important for growth of skin

cells; important for night vision

Promotes bone growth;

increases calcium andphosphorus absorption

Antioxidant; prevents cellular

damage

Needed for normal blood

clotting

Normal metabolism of

carbohydrates

Normal growth; part of electron

transport chain; energy

metabolism


10/26

VITAMINS

Vitamin

Niacin

B6 (pyridoxine)

Pantothenic acid

Folic acid

B12(cyanocobalamin)

Sources

Liver, milk, whole grains, nuts,

meats, legumes

Whole grains, meats,

vegetables

Meats, dairy, whole grains

Legumes, nuts, green leafy

vegetables, oranges, broccoli,

peas, fortified bread and cereal

Meats, eggs, dairy products,enriched cereals

Function

Important in energy metabolism

Important for amino acid

metabolism

Needed for energy metabolism

Coenzyme involved in nucleic

acid metabolism; prevents

neural-tube defects in

developing fetuses

Coenzyme in nucleic acidmetabolism; maturation of red

blood cells


11/26

MINERALS

Mineral

Calcium

Phosphorus

Potassium

Chlorine

Sodium

Magnesium

Iron

Fluorine

Iodine

Zinc

Sources

Diary products; salmon; sardines;

kale; tofu; collard greens; legumes

Dairy products; meats; poultry; grains

Meats; dairy products; many

fruits and vegetables; grains

Table salt; processed foods

Table salt; processed foods

Whole grains; green leafy vegetables

Meats; eggs; legumes; whole grains;

green leafy vegetables; dried fruitFluoridated drinking water; tea;

seafood

Seafood; dairy products; iodized salt

Meats; seafood; grains

Function

Bone and tooth formation; blood clotting;

nerve and muscle function

Bone and tooth formation; acid-base balance

Acid-base balance; body water balance;

nerve function

Acid-base balance; formation of gastric juice

Acid-base balance; body water balance;

nerve function

Activation of enzymes in protein synthesis

Component of hemoglobin and of electron

carriers used in energy metabolismMaintenance of tooth structure; maintenance

of bone structure

Component of thyroid hormones

Component of certain digestive enzymes


12/26

FOOD GUIDE PYRAMID

Fats

Sugars

Fats, Oils, and Sweets (use sparingly)Soft drinks, candy, ice cream, mayonnaise, and

other foods in this group have relatively few

valuable nutrients.

Milk, Yogurt, and Cheese Group

(2-3 Servings)Milk and other dairy products are rich in

proteins, carbohydrates, vitamins, and

minerals.

Meat, Poultry, Fish, Dry Beans, Eggs,and Nut Group

(2-3 servings)

These foods are high in protein.

They also supply vitamins and minerals.

Vegetable Group

(3-5 servings)

Vegetables are a low-fat

source of carbohydrates,

fiber, vitamins, and minerals.

Fruit Group

(2-4 servings)

Fruits are good sources of

carbohydrates, fiber, vitaminsand water.


13/26

The Process of Digestion

A. The Mouth

1. Teeth (Mechanical Digestion )

2. Saliva (Chemical Digestion)

B. The Esophagus

C. The Stomach

1. Chemical Digestion2. Mechanical Digestion

D. The Small Intestine

E. Absorption in the Small Intestine

F. The Large Intestine


14/26

THE ORGANS OF DIGESTIVE SYSTEM

Pharynx

Mouth

Salivary glands

Esophagus

Liver

Gallbladder(behind liver)

Rectum

Stomach

Pancreas(behind stomach)

Large intestine

Small intestine


15/26


16/26

PREGASTRIC DIGESTION

There are 3 stages to provide food for the gut to work on in the mouth:

1.Prehension the process of seizing or grasping or otherwise getting food into the

mouth.

2.Mastication the first step in the breakdown of complex foodstuffs and serves several

functions, including:

a. breaking large pieces into small pieces, resulting in a massive increase in

surface area which is where digestive enzymes work

b. softening of food and transformation into a size conducive to swallowing

c. lubrication of food by impregnating it with saliva

3.Swallowing the bolus is swallowed and passed on to the next part of the gut.

see the human teeth

Digestion is the process that converts the ingested foods into a form that can be

absorbed and transported.
http://g/digestion%20for%20sf-usi/Fundamental%20digestive%202/PREGASTRIC%20DIGESTION/humanpage.htmlhttp://g/digestion%20for%20sf-usi/Fundamental%20digestive%202/PREGASTRIC%20DIGESTION/humanpage.html


17/26

Dental Formulae

Deciduous2 1 0 2

2 1 0 2= 10 Permanent

2 1 2 3

2 1 2 3= 16


18/26

SALIVA

Saliva is produced in and secreted from salivary glands. The basic secretory units of salivary

glands are clusters of cells called an acini.

The three major pairs of salivary glands are:

parotid glands produce a serous, watery secretion

submaxillary (mandibular) glands produce a mixed serous and mucous secretion

sublingual glands secrete a saliva that is predominantly mucous in character

The basis for different glands secreting saliva of differing composition can be seen by examining

salivary glands histologically. Two basic types of acinar epithelial cells exist:

serous cells, which secrete a watery fluid, essentially devoid of mucus

mucous cells, which produce a very mucus-rich secretion

Saliva contains of mucus to lubricate the food and hydrogencabonate to provide the ideal condition

of pH for amylase to work.


19/26

ESOPHAGUS

The bolus can be ensured to travel down the esophagus by epiglottis.

The bolus is swallowed and enters the esophagus and it will be pushed down towards the

stomach by peristalsis (wave of esophagus muscular contraction).


20/26

STOMACH

The stomach contains digestive glands that produce 3 important secretion :

mucus protect the walls of the stomach from attack by gastric juices

pepsinProteases: Pepsinogen, an inactive zymogen, is secreted into gastric juice from

both mucous cells and chief cells. Once secreted, pepsinogen is activated by stomach acid

into the active protease pepsin, which is largely responsible for the stomach's ability to initiate

digestion of proteins. Chief cells also secrete chymosin (rennin), a protease that coagulates

milk protein.

hydrochloric acid provides the acidic conditions neede for the action of pepsin.

Hormones: The principal hormone secreted from the gastric epithelium is gastrin, a peptide

that is important in control of acid secretion and gastric motility

Inside the stomach the food is chuened up with the gastric juices into a creamy liquid called

chyme.


21/26

SMALL INTESTINE

The digestion of molecules is completed in the small intestine, using digestive juices that

contain:

enzymes from the pancreas amylase, protease, and lipase (see table 2)

enzymes from the intestine wall maltase, sucrase (see table 2)

bile from the liver.


22/26

LARGE INTESTINE

Some of food d that enter the small intetine cant be digested and absorbed into the

bloodstream.

These foods are :

indigestible fiber

undigested food some digestible food that may not be completely digested in

the small intestine

Those foods make up the bodys solid and pass into the large intestine.

In the large intestine wateris absorbed

waste materials form fecal material (faeces)

See Gastrointestinal Transit: How Long Does It Take?
http://g/digestion%20for%20sf-usi/Fundamental%20digestive%202/THE%20STOMACH/transit.htmlhttp://g/digestion%20for%20sf-usi/Fundamental%20digestive%202/THE%20STOMACH/transit.html


23/26

THE DIGESTIVE ENZYMES

Site

Mouth

Stomach

Small intestine

(from pancreas)

Small intestine

Enzyme Role in Digestion

Salivary amylase

Pepsin

Amylase

Trypsin

Lipase

Maltase, sucrase, lactase

Peptidase

Breaks down starches into

disaccharides

Breaks down proteins into large

peptidesContinues the breakdown of

starch

Continues the breakdown of

protein

Breaks down fat

Breaks down remainingdisaccharides into

monosaccharides

Breaks down dipeptides into

amino acids.


24/26

LIVER & PANCREAS

Liver

Gallbladder

Duodenum

Bile duct

Pancreas

Pancreatic duct

To rest of small intestineCholecystokinin is the principle stimulus for delivery of pancreaticenzymes and bile into the small intestine.


25/26

SMALL INTESTINE

Small Intestine Villus

Circular folds

Epithelial cells

Capillaries

Lacteal

Vein

Artery


26/26

EXERCISE

1. What happens to solids that are indigestible - for example, a rock or a penny? Will it remain

forever in the stomach?"

If the indigestible solids are large enough, they indeed cannot pass into the small intestine, and

will either remain in the stomach for long periods, induce a gastric obstruction or, as every catowner knows, be evacuated by vomition However, many of the indigestible solids that fail to pass

through the pylorus shortly after a meal do pass into the small intestine during periods between

meals.

digestive system - sf

Documents