8A FOOD & DIGESTION (1)

8/7/2019 8A FOOD & DIGESTION (1)

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8A FOOD &

DIGESTION

Tuesday, August 24, 2010


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Objectives :

Students should be able to :

1. understand the importance of food to

our body.2. Know the classes of food and thefunctions of the nutrients.

3. Understand the process of digestion,absorption and defecation.



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8A.1 WHY WE NEED FOOD



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8A.2 EATING FOR ENERGY,

EATING FOR HEALTHHumans need to consume a balanced diet which contains

a variety of different types of food.

The main nutrients the body needs are:

carbohydratesfor energy; proteinsfor growth and repair;

fatsto store energy;

vitaminsandmineralsto keep the body healthy.

fibrefor facilitate bowel movement

Waterfor solvent and maintain body temperature.

The amount of each food type needed is related to the

proportions in the food pyramid.



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KWASHIORKOR

MARASMUS

ANAEMIA -Lack of blood /

paleTuesday, August 24, 2010


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Food for health:

tissues



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from



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VITAMINB5



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MINERALS


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RICKET

MINERALS



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Magnesium

SODIUM

TUNA

PHOSPHORUS

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IODINE


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ZINC

IRON



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WATER



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FIBRE



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IRRITABLE BOWEL SYNDROME :

A disorder of the intestine that affects motility and causesabdominal pain, bloating and irregular bowel movements(constipation and / or diarrhea). Used to be known in the

past as spastic colon or colitis and irritable colon

HEMORRHOIDS :

Inflammation of the veins surrounding theanus.

CONSTIPATION :

A condition in which the contentsof the large intestines (bowels) aredischarged at long intervals or with

difficulty.


8A 3 A HEALTHY DIET


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8A.3 A HEALTHY DIET


8A 5 DIGESTION


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8A.5 DIGESTION1. DIGESTION : Process of

breaking down food intosoluble and diffusiblemolecules.

2. Digestive system is made ofdigestive tract (a series ofhollow organ joined in a long,twisting tube from the mouthto the anus that helps thebody break down and absorbthe food).

3. Inside these hollow organ is alining called MUCOSA.

4. Mucosa in the mouth,stomach and small intestineproduce juice and enzymes todigest the food.


ENZYMES


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ENZYMES

1. Enzyme is special proteins produced by the body to speed up chemicalreactions in the body.

2. Enzymes work best at the normal body temperature (37 C) andcertain medium (alkaline, neutral or acidic)

3. Enzyme that helps in digestion of carbohydrates AMYLASE

Enzyme that helps in digestion of protein PROTEASE

Enzyme that helps in digestion of fat - LIPASE

ORGAN MEDIUM

Mouth Neutral

Stomach Acidic

Small intestine &pancreas

Alkaline



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HOW ENZYME WORKS IN DIGESTION?


PROCESS OF DIGESTION


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PROCESS OF DIGESTION

1. MOUTH

The teeth chew and grind food into smaller

particles.

Salivary glands secrete saliva whichcontains enzyme amylase to digest starch

to maltose.

Saliva also contains mucin to moisten thefood so that it can pass easily through the

digestive canal.

The breaking down of large food molecules into small soluble moleculesinvolves 2 processes :

1. PHYSICAL DIGESTION (mechanical process of breaking down largepieces of food into smaller particles using the teeth and the churningmovement of the alimentary canal)

2. CHEMICAL DIGESTION (involves the action of various enzymes inbreaking down complex food molecules)


2 ESOPHAGUS


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2. ESOPHAGUS

The digested food is shaped into a bolus by the tongue and swallowed.

The bolus is pushed to the stomach by the contraction and relaxation of the

walls of the esophagus.Contraction and relaxation movement of the muscles are knownPERISTALSIS to move food along the alimentary canal.

Each mouthful of food takes about six seconds to reach stomach onceswallowed.


3 STOMACH


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3. STOMACH

The stomach is a sack made of muscle.

When it is empty, it has volume of 50ml but this

can expand to hold up to 1.5L or more after meal. The walls of stomach are made of three differentlayers of muscle to churn the food and mixed withthe digestive juices.

Gastric juices are secreted by the

gastric glands (in the stomach walls)

Gastric juices contain :

1. Hydrochloric acid

to stop the action of the enzymeamylase in saliva

- to kill bacteria in the food- to provide acidic medium for the actionof enzymes in the stomach

2. Proteases breakdown proteins intopolypeptides.

3. Casein to solidify milk

The partially digested food called chyme

(creamy mixture) is then released intoduodenum.Tuesday, August 24, 2010

4 SMALL INTESTINE


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4. SMALL INTESTINE When the food has been churned into chyme,

pyloric sphincter opens and chyme passes toduodenum.

Sphincteris to stop large particles food to enterduodenum and the food is kept for furtherchurning.

Duodenum is the first part of small intestine thatjoined to liver and pancreas.

Juices that flow to the duodenum for digestion :

1. BILE : - greenish liquid produced by the liver thatstored in gall bladder.

- Bile IS NOT enzyme. It is alkaline.

- Functions :

(a) to neutralise the acid produced by the stomach(b) to provide alkaline medium for the actions ofenzyme in the pancreatic juice.

(c) to emulsify fats & oil into small globules toincrease the surface area for the action ofenzymes.


Juices that flow into duodenum for digestion :


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Juices that flow into duodenum for digestion :

2. PANCREATIC JUICE ( contains enzymes that digest starch, protein andfats)

(a) Amylase to breakdown starch into maltose

(b) Protease to breakdown polypeptides into peptides

(c) Lipase to breakdown fats into fatty acids & glycerol

Food that is digested in the duodenum enters ileum (lower part of the

small intestine). The food is mixed with the intestinal juice secreted by intestinal glands 9in

the walls of the small intestine).

The intestinal juice is alkaline and contains enzymes which complete thedigestion of proteins, fats and starch.

The end products of digestion are ready for absorption :

STARCH GLUCOSE

PROTEIN AMINO ACID


ABSORPTION SMALL


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ABSORPTION SMALLINTESTINE After digestion, food consists of smaller molecules that are soluble &easily absorbed.

End products : Glucose, amino acids, fatty acid and glycerol enter thecirculatory system by diffusion.

Absorption of these end product takes place in the small intestine.

Absorption facilitated by the feature of intestinal walls :

(a) The wall has many folds which covered with millions of finger-likeprojections called VILLI. The villi increase the surface area for absorption.

(b) The walls have many blood capillaries to facilitate absorption.

(c) The ability of the intestinal muscles to move in peristalsis.

(d) The wall is very thin to let small molecules enter the blood capillaries.

(e) The moist lining of the wall enables small molecules to dissolveeasily.



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EGESTATION (WASTE ELIMINATION)


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EGESTATION (WASTE ELIMINATION)

large intestine The undigested food is sent to the large

intestine and kept for temporarily.

As the residue passes through the largeintestine, a lot ofwater, dissolvedminerals and vitamins are absorbed intoblood.

Residue from the small intestineundergoes decay and becomes faeces.

The faeces are passed on to the rectumwhere the faeces are stored before being

pushed through the anus. The process of removing faeces fromthe body : DEFECATION / EGESTATION.



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8A FOOD & DIGESTION (1)

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