Main processes of mammalian nutrition

Ingestion Digestion AbsorptionAssimilationEgestion

Digestion

Absorption

EgestionNextNext BackBack

Main processes of mammalian nutrition

Ingestion Digestion AbsorptionAssimilationEgestion

Digestion

Absorption

EgestionNextNext BackBack

Ingestion

is the intakeintake of food into the alimentary canalrelevant organs:

teeth

relevant processes: swallowing peristalsis

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Ingestion II

is the intakeintake of food into the alimentary canalrelevant organs:

teeth

relevant processes: swallowing peristalsis

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incisorcaninepremolar

molar

Digestion

is the breaking downbreaking down of food into molecules small enough to be absorbed into the body

relevant organs mouth and teeth alimentary canal stomach duodenum

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Absorption

is the movementmovement of digested, soluble and simple molecules from the gut through the wall into the body (Cont’d)

relevant processes diffusion active transport

relevant structures

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Assimilation

is the uptake uptake && utilisation utilisation of absorbed food molecules by all body cells

fate of the absorbed food glucose energy production amino acids building up body materials fats energy reserve

roles of liver in assimilation

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Egestion

is the removalremoval of undigested and unwanted food materials from the alimentary canal

relevant structuresabnormal cases:

diarrhoea constipation

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Egestion II

is the removalremoval of undigested and unwanted food materials from the alimentary canal

relevant structuresabnormal cases:

diarrhoea constipation

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Teeth

structure of a tooth enamel dentine pulp cavity

typedentition

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Enamel

Dentine

Pulp Cavity

Jaw Bone

Cement

Nerve & blood vessel

Crown

Neck

Root

Teeth II

structure of a tooth enamel dentine pulp cavity

typedentition

Crown

Neck

Root

Enamel

Dentine

Pulp Cavity

Jaw Bone

Cement

Nerve & blood vesselNextNext BackBack

Enamel

outermostnon-livinghardest layermade up of

calcium phosphate calcium fluoride organic matter

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Dentine

middle layerhard, bone like

(softer than enamel)

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Pulp Cavity

innermost layerliving cells, blood vessels and nerve

blood vesselsblood vessels: oxygen and nutrient

nerves: sensitive to stimuli temperature pressure

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Type of Teeth

Type Features Functions

Incisor chisel shape sharp edge

biting cutting

Canine sharp & pointededge

biting cutting

Premolar large board tops with

ridges

chewing crushing grinding

Molar large

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Dentition

dental formula of a human type of teeth on one side only upper jaw lower jaw milk teeth: permanent teeth:

21202120

21202120

21232123

21232123

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2020 3232

premolarmolarcanineincisor

Tooth Decay

caused by the chemical actions of bacteria in plaque

plaque is a sticky, invisible film on the teeth surface

bacteria turns sugars into acidsacids dissolve the enamel and dentine

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Tooth Decay

caused by the chemical actions of bacteria in plaque

plaque is a sticky, invisible film on the teeth surface

bacteria turns sugars into acidsacids dissolve the enamel and dentine

irritation on the nerve, cause toothachetoothacheNextNext BackBack

How to prevent tooth decay

good brushing habitsbrushing habitsusing appropriate cleaning materialscleaning materialsavoiding sugarysugary food

having a balanced dietbalanced diethaving regular dental check-updental check-up

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Alimentary Canal

a tubetube from mouth to anus

is modifiedmodified into different structuresdigestive system =

alimentary canal + associated

alimentary alimentary canalcanal

associated glandsassociated glands

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Alimentary Canal

a tubetube from mouth to anus

is modifiedmodified into different structuresdigestive system =

alimentary canal + associated glands

sequencesequence of the structuresoesophagu

sstomachduodenu

mileumcaecumappendixcolonrectumanus Salivary

glandGastric gland

PancreasLiverIntestinal gland

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alimentary alimentary canalcanal

associated glandsassociated glands

Swallowing

tongue raises pushing the bolusbolus to the back

bolus pushes the soft palatesoft palate upwards

epiglottisepiglottis lowers and covers the tracheabolus enters the oesophagus

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Peristalsis

food is moved along the canal by

rhythmic contractionrhythmic contraction and

relaxationrelaxation of two muscles circular muscle longitudinal muscle

demonstration

PeristalsisPeristalsis

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Oesophagus

Digestion II

only small molecules can pass through the wall of intestine

food are usually composed of largelarge moleculesfood should be digested before absorptionphysical methodschemical methods

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Physical Digestion

TeethStomachBile salt

by churning by emulsifying

action in duodenum by cuttingcuttingchewinchewin

gggrindingrindin

ggbitingbitingtearingtearing

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Chemical Digestion

involved the change of the chemical structures of food

e.g.

this involves digestive enzymesdigestive enzymesno digestion on: water, glucose, simple sugars,

minerals, vitamins

StarchStarchmalto

semalto

semaltose

maltose

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amylase

Mouth

saliva is a digestive juice consisting of amylase mucus water

it is slightly alkaline

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Stomach

cardiac sphincteraction of proteases

action of hydrochloric acid provide acidic medium for

proteases

pyloric sphincter

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protease

Duodenum

pancreatic juice amylase, proteases, lipases

bile colour, composition, no enzymatic property

intestinal juice carbohydrases, proteases

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Caecum,Colon & Rectum

no enzyme secretion in omnivores and carnivores

specific function in herbivores micro-organisms cellulase weakness

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Absorption II

take place in ileumstarts at stomach / duodenumvillus

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Villus

finger like projections increase S.A./V

one cell thickmany blood vesselscentral lacteal

villus

lacteal

Blood vessels

epithelium

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Transport of absorbed food

lumen

BackBack

epithelium

blood capillaries

hepatic portal vein

liverhepatic vein

vena cava heart (general circulation)

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Water soluble Water soluble foodfood

Fat soluble foodFat soluble food

lumen

epithelium

lacteal

Lymph vesselvena cava

heart (general circulation)

Assimilation II

fate of absorbed food substances glucose amino acids fats

roles of liver

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Fate of glucose

for releasing energyexcess glucose will be stored as

glycogen fats

storage site liver muscle

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Fate of amino acids

for making new cells and tissuesexcess amino acids will be deaminatedproduct: ureasite of excretion:

kidney

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Fate of fats

for formation of cell membranesexcess fats will be stored

fats

storage site adipose tissue

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Roles of liver

regulating blood glucose levelstoring glycogenstoring iron and vitaminsbreaking down excess amino acids

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Diarrhoea

Causes: (1) bacterial infection (2) eating poisonous substances

Consequences: (1) quick movement of intestine (2) food passes along the canal quickly (3) less water absorbed (4) watery faeces produced

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Constipation

Causes: eating too less dietary fibres eating too less fresh fruit

Consequences: (1) slow movement of intestine (2) food passes along the canal slowly (3) much water absorbed (4) hard, dried faeces produced

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End of the Chapter

By Nicholas Lai(PLKWCC)

Glossary

Active transport: movement of molecules against concentration gradient with the utilizing of energy.

Amylase: an enzyme that convert starch to maltose. Carbohydrases: enzymes digest carbohydrates into simpler mo

lecules. Carnivores: organisms feed on animals only Diffusion: movement of molecules from a region of high conc

entration to a region of low concentration Herbivores: organisms feed on plants only Lipases: enzymes digest fat/oil into simpler molecules

Glossary

Mucus: a sticky substance secreted by epithelial cells of the gut

Omnivores: organisms feed on animals and plants Proteases: enzymes digest protein into simpler molecules