THE DIGESTIVE SYSTEM

ANATOMY OF THE HUMAN DIGESTIVE SYSTEM

NUTRITION – the process of taking in and using food

NUTRIENTS – substances in food that are used as energy sources to run the system of the body

DIGESTIVE SYSTEM – the organs and glands in the body that are responsible for digestion

DIGESTION – the breakdown of food to smaller molecules

GENERAL TERMINOLOGIES

INCOMPLETE DIGESTIVE SYSTEM – common among invertebrates, there is only a

single opening for the ingestion of food (an anus is absent)

COMPLETE DIGESTIVE SYSTEM – common among nematodes, annelids, mollusks, echinoderms, and vertebrates, this type has digestive tubes with two openings (a mouth and an anus)

TWO TYPES OF DIGESTIVE SYSTEM

THE HUMANDIGESTIVE SYSTEM

The human digestive tract is a long, coiled, muscular tube that stretches from the mouth to the anus.

From mouth to the anus, the human food tube or the digestive tract is about nine meters long.

THE HUMAN DIGESTIVE TRACT

9meters

THE HUMAN DIGESTIVE TRACT MEASUREMENT

SPECIALIZED REGIONS WHERE DIGESTION TAKES PLACE

1. Food processing begins in the mouth.

2. The bite food is then swallowed and is moved through the pharynx into the esophagus.

3. Then, food is mechanically and enzymatically digested in the stomach.

4. Most enzymatic digestion takes place in the small intestine.

5. The large intestine then eliminates wastes leading to the opening for the elimination of wastes called anus.

SPECIALIZED REGIONS WHERE DIGESTION TAKES PLACE

MOUTH

PHARYNX

ESOPHAGUS

STOMACH

SMALL INTESTINE

LARGE INTESTINE

ANUS

DIGESTIVE SYSTEM WITH OTHER ASSISTING ORGANS

WHERE DIGESTION TAKES PLACE WITH ASSISTING ORGANS

1. Food processing begins in the mouth.

2. The bite food is then swallowed and is moved through the pharynx into the esophagus.

3. Then, food is mechanically and enzymatically digested in the stomach.

4. The liver secretes bile.

5. The pancreas secretes digestive enzymes.

WHERE DIGESTION TAKES PLACE WITH ASSISTING ORGANS

6. Most enzymatic digestion takes place in the small intestine.

7. Nutrients are then digested as they move the digestive tract.

8. Nerves and hormones regulate digestion.

9. Absorption takes place mainly through the villi of the small intestine.10. The large intestine then eliminates wastes leading to the opening for the elimination of wastes called anus.

MECHANICAL PHASE – involves the breaking up of food into small pieces, pushing the food down the food tube, and mixing with it digestive juices

CHEMICAL PHASE – involves the further breaking up of the larger molecules of food into smaller molecules by the action of digestive enzymes

TWO PHASES OF DIGESTION

HOW DIGESTION IS DONE?

MECHANICAL DIGESTION starts in the mouth (Mastication) where four kinds of teeth tear the food into pieces:

Four kinds of teeth: 1. INCISORS – thin-edged for cutting

food2. CANINES – are pointed used for

tearing3. MOLARS & PREMOLARS – specialized

for crushing and grinding

MECHANICAL PHASE OF DIGESTION IN THE MOUTH

THE HUMAN TEETH / MAN’S DENTAL SET

TEETH UPPER JAW LOWER JAW TOTAL

Incisors 2 ; 2 2 ; 2 8

Canine 1 ; 1 1 ; 1 4

Premolars 0 0 0

Molars 2 ; 2 2 ; 2 8

TOTAL: 20

THE TEMPORARY DENTAL SET OF MAN

TEETH UPPER JAW LOWER JAW TOTAL

Incisors 2 ; 2 2 ; 2 8

Canine 1 ; 1 1 ; 1 4

Premolars 2 ; 2 2 ; 2 8

Molars 3 ; 3 3 ; 3 12

TOTAL: 32

THE PERMANENT DENTAL SET OF MAN

Our mouth has salivary glands that secrete saliva. This saliva contains the enzyme called salivary amylase.

This salivary amylase and the enzyme called maltase (catalyzes maltose into glucose) enables the chemical digestion of the mouth to occur.

CHEMICAL DIGESTION IN THE MOUTH

THE HUMAN SALIVARY GLANDS

These salivary glands secrete salivary amylase.

CARBOHYDRATES

I. STARCH Maltose

II. MALTOSE Glucose

SALIVARY AMYLASE or PTYALIN

(or amylum/amylose) (a double sugar)

MALTASE

(a simple sugar)

HOW MOUTH’S CHEMICAL DIGESTION IS DONE?

The tongue also helps in the mechanical digestion of food. It helps push and mix food while the back part of it secretes mucus making swallowing easier.

The pharynx and esophagus conduct food to the stomach. After being chewed, the food is swallowed through the pharynx extending to the esophagus.

THE TONGUE, PHARYNX, & ESOPHAGUS

MECHANICAL PHASE: THE PROCESS OF PERISTALSIS

PHARYNX or THROAT – the hallway of food used for both digestive and respiratory system.ESOPHAGUS – canal that connects throat to the stomachEPIGLOTTIS – tissue that closes the opening to the airway during swallowingPERISTALSIS – pushes soft mass of chewed food (bolus) and mixes it with digestive juices in stomach and small intestineANTI-PERISTALSIS – results vomiting which prevents body from harmful substances that are ingested.

PHARYNX AND ESOPHAGUS ON CONDUCTING FOOD

Stomach’s entrance is closed by a ring muscle at the end of the esophagus.

When empty, the stomach is collapsed and shaped almost like a hot dog.

Once food enters, the folds of stomach wall called rugae smooths out and expands to more than a liter.

FOOD’S DIGESTION IN THE STOMACH

THE STRUCTURE OF THE STOMACH

The stomach secretes millions of gastric glands.

1. THE PARIETAL CELLS in the gastric glands secrete hydrochloric acid and intrinsic factor, a substance needed for adequate absorption of vitamin B12.

2. THE CHIEF CELLS secrete pepsinogen (an inactive enzyme precursor). When pepsinogen comes in contact with the acidic gastric juice, it becomes pepsin (the main digestive enzyme of the stomach).

ENZYMATIC DIGESTION IN THE STOMACH

Digestion is completed in the small intestine and nutrients are absorbed through its wall.The small intestine is about 5 to 6 meters (about 17ft.) in length and has three regions.

1. Duodenum2. Jejunum3. Ileum

FOOD’S DIGESTION IN THE SMALL INTESTINE

THE THREE REGIONS OF THE SMALL INTESTINE

Most chemical digestion takes place in the duodenum, the first layer of the small intestine.

THE LAYERS OF THE SMALL INTESTINE (Labelled)

LIVER – the largest internal organ of the body and also one of the

most complex organs which lies in the upper right abdomen just under the diaphragm.

-- the liver secretes BILE

BILE – the fluid secreted by the liver which emulsifies fats

THE LIVER SECRETES BILE

THE LIVER SECRETING BILE

Secretes bile.Helps maintain homeostasis by removing or adding nutrients to the blood.Converts excess glucose to glycogen and stores it.Converts excess amino acids to fatty acids and ureaStores iron and certain vitamins.Detoxifies alcohol and other drugs and poisons.

FUNCTIONS OF A LIVER

PANCREAS – an elongated gland that secretes both

digestive enzymes and hormones that help regulate the level of glucose in the blood

– the enzymes secreted by the pancreas are

called trypsin and chymotrypsin.

THE PANCREAS SECRETES DIGESTIVE ENZYMES

PANCREATIC LIPASE

Degrades fats

PANCREATIC AMYLASE

Breaks down almost all types of carbohydrates except cellulose

disaccharides

RIBONUCLEASE and

DEOXYRIBONUCLEASE

Split RNA and DNA to free nucleotides

Trypsin and Chymotrypsin digest polypeptides to dipeptides resulting to:

THE PANCREAS RELEASING DIGESTIVE ENZYMES

1. Bile from the liver and digestive enzymes from the pancreas released into the duodenum.

2. These two then acted on the chyme (a semi fluid mass of digested food expelled by the stomach into the duodenum.

3. Then enzymes produced by the epithelial cells lining the duodenum catalyze the final steps in the digestion of the major types of nutrients.

SO HOW DOES CHEMICAL DIGESTION IN THE SMALL INTESTINE REALLY DONE?

Chyme moves through the digestive tract by peristalsis, mixing contractions, and motions of the villi. Nutrients in the chyme come into contact with enzymes that digest them.

1. Carbohydrates are digested to monosaccharides or simple sugars2. Proteins are digested to amino acids3. Fats are digested to fatty acids and monoacylglycerols

THE DIGESTED NUTRIENTS

PROTEINS Maltose

FATS fatty acids, glycerol

CARBOHYDRATES Simple sugars

proteases

CHEMICAL DIGESTION OF COMPLEX MOLECULES

lipase

carbohydrases

Secretion of other digestive juices is regulated by nerves and hormones.This called enteric nervous system continues to regulate many motor and and sectory activities of the digestive system even if sympathetic and parasympathetic nerves to these organs are cut.Several hormones including gastrin, secretin, cholecystokinin (CCK), and gastric inhibitory peptide (GIP), help regulate the digestive system.

NERVES AND HORMONES REGULATE DIGESTION

SOME HORMONES THAT REGULATE DIGESTIONHORMONE SOURCE TARGET

TISSUEACTIONS

Gastrin Stomach (mucosa)

Stomach (gastric glands)

Stimulates gastric glands to secrete pepsinogen

Secretin Duodenum (mucosa)

Pancreas L

Liver

Signals secretion of sodium bicarbonateStimulates bile secretion

Cholecystokinin (CCK)

Duodenum (mucosa)

Pancreas

Gallbladder

Stimulates release of digestive enzymesStimulates emptying of bile

Gastric Inhibitoy Peptide (GIP)

Duodenum (mucosa)

Stomach Decreases stomach churning, thus slowing emptying

ABSORPTION is the process by which substances are taken in by cells of the food tube.Absorption takes place mainly

through the villi of the small intestine.Digested food in the form of amino

acids, simple sugars, fatty acids, and glycerol diffuse into the cells of the villi.

ABSORPTION IN ACTION

THE STRUCTURE OF THE VILLUS (Plural VILLI)

THE PROCESS OF ABSORPTION

1. Most of the digested food diffuse into capillaries and reach the blood, while fatty acids and glycerol diffuse into the lacteals and reach another circulating fluid called lymph.

2. Through diffusion, digested food reaches the blood and lymph and undergoes a process called circulation.

3. The circulating fluids distribute the digested food to all the cells of the body.

Undigested food passes through the large intestine.Although shorter in length than the

small intestine, it is called “large” because its diameter is greater than that of the small intestine.The large intestine is 1.3m (about

4ft.) in length.

THE LARGE INTESTINE ELIMINATES WASTE

THE STRUCTURE OF THE LARGE INTESTINE

ELIMINATION – the process of getting rid of digestive wastes – materials that have not been absorbed from the digestive tract and did not participate in metabolic activities.EXCRETION – the process of getting rid of metabolic wastes, which in mammals is mainly the function of the kidneys and lungs.NOTE: However, the large intestine excrete bile pigments.

DESTINCTION BETWEEN ELIMINATION & EXCRETION

DIARRHEA – This happens when chyme passes too rapidly (defecation). This may be caused by anxiety, certain foods, or disease organisms that irritate the intestinal lining.CONSTIPATION – This is the result of the too slowly passing of chyme through the intestine.COLORECTAL CANCER– This is commonly known as the cancer of the colon and rectum.

SOME ILLNESS INVOLVING ELIMINATION OF WASTES

IMPORTANCE OF FOOD-GETTING AND DIGESTION

Food in this topic will include not only the organic nutrients but also water, minerals, and vitamins.Be reminded that three building materials of body tissues consists largely of 67% water, 15% proteins, and 13% fats.Mineral solids like calcium, phosphorus, iron, etc. Are also used as building materials of the body.

FUNCTIONS OF FOOD IN THE BODY

Carbohydrates provide energyLipids provide energy and are used to make biological moleculesProteins serves as enzymes and as structural components of cells.Vitamins are organic compounds essential for normal metabolism.Minerals are inorganic nutrients.Antioxidants protect against oxidantsPhytochemicals play important roles in maintaining health.

THE WHYs TO TAKE FOOD

CARBOHYDRATES PROVIDING BODY ENERGY

LIPIDS OR FATS FOR OUR BODY

PROTEINS – WE NEED IT, WE DON’T!

SOME VITAMINS THAT OUR BODY NEEDS

MINERALS THAT OUR BODY NEEDS

ANTIOXIDANTS IN ACTION

PHYTOCHEMICALS FOR MAINTAINING HEALTH

ENERGY SPENT IN SOME DAILY CHORES

ACTIVITY AMOUNT OF ENERGY USEDIn calories per kilogram of body weight

per hour

DRESSING UP 0.7

EATING 0.4

WALKING MODERATELY 2.0

WALKING FAST 3.5

RUNNING 7.0

SWIMMING 7.9

WRITING 0.4

WASHING DISHES 1.0

WASHING LAUNDRY 1.5

SWEEPING THE FLOOR 1.4

Millions of people do not have enough to eat, or do not eat a balance diet.Malnourished individuals are weak, easily fatigued, and highly susceptible to infections.In young children, severe protein malnutrition results to a condition called kwashiorkor (first-second). This is the situation in which a first child is displaced from its mother’s breast because a younger sibling is born.

UNDERNUTRITION IS A SERIOUS PROBLEM

MALNUTRITION: KWASHIORKOR AND MARASMUS

THE IMPACT OF MALNUTRITION

Obesity is the excess of accumulation of body fats.The World Health Organization

(WHO) considers obesity among the top 19 global health problems.Obesity is a major risk factor for heart

disease, diabetes mellitus, osteoarthritis, and certain types of cancer, including breast and colon cancers.

OBESITY IS A SERIOUS PROBLEM

OBESITY

THE IMPACT OF OBESITY

Have a balance diet.Watch the amount you eat.Chew your food well and eat

slowly to facilitate digestion.Drink plenty of water.Balance your food with

activities such as exercise.

TIPS FOR A HEALTHY BODY

Vegetables and fruitsMilk and milk productsMeat including fishCereals such as riceOther healthy foods

Always Remember: The greatest wealth

is your HEALTH!

YOUR BALANCE DIET SHOULD INCLUDE:

Biology (Thomson Asian Edition) by Solomon, Berg, MartinIntegrated Science II (Biology) by L.

M. Rabago, et.alFunctional Biology (Modular

Approach) by Lilia M. RabagoScience and Technology for the

future II by Lourdes F. Lozano, et. al

Topic References:

THE END :)

Prepared by: Mr. Ranulfo T. Bacus