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ANIMAL NUTRITIONANIMAL NUTRITIONDIGESTION DIGESTION

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Animal Nutrition

Nutrients & Diet Digestive System

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Lesson 1Learning Objectives

1.Identify the different parts of a tooth and their functions.2.Describe that mammals have 2 sets of teeth in its life.3.State the causes of dental decay and describe the proper care of

teeth.

Outline Teeth

– Tooth structure– Types of teeth– Sets of teeth– Dental problems– Dental care

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Teeth

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Tooth Structure

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Types of teeth

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Sets of teeth• Humans have two sets of teeth in a lifetime.• Deciduous teeth– Also known as primary or milk teeth– The first set of teeth– 20 teeth altogether– Start to erupt at the age of 6 months until 3 years of age.

• Permanent teeth– At the age of about 6, they sequentially erupt to replace

the deciduous teeth which become loose and shed.

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Dental Problems

• Dental cariesDental caries is also known as tooth cavity or decay. It is due to bacterial infection.

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Formation of tooth decay

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• TartarTartar is the hard deposit that forms on the tooth due to the hardening of bacterial plaque that is left untreated.

(Plaque is a sticky and colourless film of bacteria that constantly forms on the teeth)

Accumulation of tartar may give rise to gingivitis, an inflammation of the gums.

This condition is usually painless but if bacteria are allowed to spread down to the roots, the tooth may become loose and have to be removed.

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Formation of tartar and its consequences

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Dental Care

• Brush teeth at least 2-3 times a day, preferably after a meal.

• Use a toothpaste that contains fluoride. Fluoride hardens the tooth surface and makes them less easily destroyed by acid produced by bacteria from sugary food.

• Visit a dentist regularly every 6 months.• Eat healthy food containing calcium and vitamin D

and cut down sugary food.• Stop smoking

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Lesson 2Learning Objectives1.Identify the main regions of the alimentary canal and the associated organs2.Describe the main functions of these parts in relation to ingestion, digestion,

absorption, assimilation and egestion of food.3.Distinguish differences between mechanical and physical digestions.4.Describe peristalsis5.Describe digestion in the alimentary canal

Outline Alimentary canal Digestion Digestion in mouth Peristalsis

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Overview of the alimentary canal

Rectum

Small intestine

Stomach

Mouth

Anus

Oesophagus

Large intestine

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Sequence of food1.Ingestion – Taking in food.2.Digestion – Breakdown of large, insoluble, complex

food particles into small, soluble, simple food particles.

3.Absorption – Uptake of soluble molecules into the tissue of animal.

4.Assimilation – Organism making use of absorbed materials.

5.Egestion – Removal of undigested food materials from the body.

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Digestion

Mechanical Chemical

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Digestion

• Mechanical digestion– Breakdown of food particles into smaller

pieces to increase the surface area or the action of enzymes.

• Chemical digestion– Breakdown of food particles involving

enzymatic reactions which digest the food into simpler form.

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Digestion in Mouth

• Teeth– Cut, tear, grind food into smaller pieces

(mastication/chewing) for easy swallowing and fast digestion

• Saliva– Contains amylase.• Breakdown starch into maltose

• Tongue– Mixes food with the saliva and rolls it into balls called

bolus.– Pushes food bolus into the opening of the oesophagus.

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Oesophagus• Oesophagus is a narrow muscular tube.• It consists of a pair of antagonistic muscles– Circular muscle– Longitudinal muscle

• Food bolus travels through the oesophagus to the stomach by peristalsis.

• Peristalsis is the rhythmic wave-like contractions of the walls of the oesophagus. It involves the contraction and relaxation of muscles.

No digestion of food in the oesophagus.

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Peristalsis

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Peristalsis

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Lesson 3

Learning Objectives1.Describe digestion in the alimentary canal.

Outline Digestion in stomach Digestion in duodenum Digestion in ileum

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Digestion in the stomach

• Strong muscular wall• It acts as a mixer. It churns and mashes food bolus with gastric juice to form chyme.• Gastric juice is produced by the stomach.• Gastric juice contains pepsin, rennin and

hydrochloric acid.

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Digestion in the stomach

• Pepsin– Breakdown proteins into peptides

• Rennin– Curdles/coagulates milk

• Hydrochloric acid– Maintains optimum pH for pepsin to work– Kills bacteria

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Digestion in the stomach

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Small Intestine

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Digestion in the duodenumMost digestion takes place here with the help of liver,

gall bladder and pancreas.

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Digestion in the duodenum

• Pancreas releases pancreatic juice.– Lipase• Breakdown fats into fatty acids and glycerol

– Amylase• Breakdown starch into maltose

– Trypsin• Breakdown proteins and peptides into amino acids

–Sodium hydrogen carbonate• Neutralises the acidic chyme

• Liver produces bile• Gall bladder stores bile

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Emulsification

• Bile– Not an enzyme– Yellowish-green– Alkali• Neutralises the acidic chyme

– Emulsifies fats (most important function!)

• Emulsification is the breakdown large droplets of fats into smaller droplets of fats to increase surface area for faster lipase action.

Bile does not digest food but it helps in digestion of fats.

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Digestion in the ileum

• The final digestion occurs in the ileum.• The intestinal wall produces 6 enzymes

– Sucrase– Maltase– Erepsin– Lipase– Lactase– Enterokinase

SMELL E

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Digestion in the ileumAt the end of digestion, carbohydrates, proteins and fats have been broken down

into smaller particles.

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Lesson 4Learning Objectives1.Describe absorption of digested food.2.Describe the structure of villus including the roles of

lacteal and capillaries.3.Describe the transport of digested food.

Outline Absorption in ileum

– Adaptations of ileum

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What happen next?

After digestion, the final products (glucose, amino acids, fatty acids and glycerol) are

absorbed in the ileum.

Absorption in ileum

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Structure of ileum

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Structure of ileum

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Structure of ileum

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Group Discussion

1. Brainstorm the characteristics of ileum.

2. How can they help in absorbing digested food efficiently?

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Adaptation of ileum to absorb digested food

• The ileum is very long (4m)– Food stays longer in ileum. More time for digestion

and absorption to be completed.• The internal wall is folded.– Surface area is increased. Rate of absorption is

faster.• Tiny finger-like projections called villi are

present on the internal wall surface.– Surface area is further increased. Rate of

absorption is faster.

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• Microvilli are present on the epithelium of villi.– Surface area is further increased. Rate of absorption is

faster.

• The epithelium is thin.– Diffusion or active transport of digested food particles is

faster.

• Each villus has capillaries and lacteal.– Glucose and amino acids are absorbed by the capillaries

directly into the bloodstream. They are then transported to the liver.

– Fatty acids and glycerol are recombined into fats by the epithelium and then absorbed by the lacteal (part of the lymphatic system). Fats are eventually emptied into the bloodstream. They are then transported to the liver.

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Lesson 5Learning Objectives1.Describe the assimilation of food.2.State the roles of liver

Outline Assimilation of food Other roles of liver Large intestine (colon)

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Assimilation in liverWhat happen to glucose, amino acids, fatty

acids and glycerol in the liver?

ASSIMILATION!Assimilation is the process

where digested food isconverted into living tissue

by anabolic reaction.

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• Glucose– Use in respiration to produce energy.– Excess glucose is converted to glycogen by hormone,

insulin. Glycogen is stored in the liver.• Amino acids– Use to synthesise new cells and repair damaged cells.– Use to make enzymes and hormones.– Excess amino acids are broken down to urea in a

process called deamination.• Fats– Use to synthesise cell membranes.– Excess fats are stored in adipose tissues to be used

as source of energy when glucose supply is insufficient (e.g. fasting)

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Other roles of liver

D2RIP2

• Detoxification– Breakdown harmful alcohol into harmless

carbon dioxide and water• Deamination of amino acid• Regulation of blood glucose concentration

– Insulin converts glucose to glycogen– Glycogen/adrenaline converts glycogen to

glucose

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• Iron storage– Haemoglobin from old red blood cells are

broken down in liver. Iron in haemoglobin is stored.

• Protein synthesis– Liver synthesises proteins in blood

plasma e.g. albumin, fibrinogen.• Production of bile

Other roles of liver

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Large Intestine

• ABSORPTION of water, mineral salts, and vitamins takes place in colon.

• The undigested food/waste (faeces) is stored in the rectum and passes out through the anus (Egestion).