11. unit 2a digestive system

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Unit 2A

Human Form & Function

Body systems

The digestive system

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Study Guide

Read :

• Text

page 87- 98 Complete :

• RQ 5-13

• AYK 1-8

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Digestion

Digestive processes can be chemical(involving digestive enzymes), ormechanical.

Chemical digestion the breaking downof the nutrients we eat into simplerorganic compounds that can beabsorbed by the body.

Mechanical digestion is the breakingdown of large sized food to smallersized food.

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ENZYME Acts on End product

Amylase Carbo-hydrate

Simple sugars(e.g. glucose)

Lipase Lipids Fatty acids

Protease Proteins Amino acids

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The anatomy of the digestive system

US Govt NIH

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Structure of the alimentary tube

Mucosa

Longitudinal

muscle layer

Circularmuscle layer

Peritoneum

Villus

SubmucosaThin muscle

layer

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Chemical digestion in the mouth

Enzyme Product

Salivary

amylase

Polysaccharides

→ Sugars

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The salivary glands

Parotidgland

Submandibulargland

Sublingualgland

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Section through the head

Nasal cavity

Palate

Tongue

Pharynx

Hyoid bone

Epiglottis

Larynx

Esophagus

Teeth

Vocal cords

The Miles Kelly Art library, Wellcome Images

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The tongue

Jari Keinänen

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Mechanical processes in themouth

Chewing (mastication)Bolus formation

Swallowing

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Human teeth are generalised – they canprocess both meat and fibrous plant foods

The Miles Kelly Art library, Wellcome Images

Incisor teeth

Premolar andmolar teeth

Canine tooth

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Human dentition

Molars Pre-molarsCanine

Incisors

Gray’s Anatomy 

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Tooth section

EnamelDentine

Pulp cavity

Cementum

Gum

Root canal

Crown

Neck

Root

The Miles Kelly Art library, Wellcome Images

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Swallowing and peristalsis

The Miles Kelly Art library, Wellcome Images

Epiglottis closesentrance to windpipe

Tongue pushes bolusinto throat

Peristalsis carriesbolus into stomach

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Chemical digestion in thestomach

Enzyme Product

Hydrochloricacid

Activatespepsinogen (→

pepsin)Pepsin Proteins→ peptones

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Mechanical processes in thestomach

Muscular churning mixes food

with gastric juices (formschyme)

Rennin (in infants only) curdlesmilk

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Absorption in the stomach

Limited absorption of

water, glucose, alcoholand some drugs takes

place in the stomach.

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Section through the stomach

EsophagusFundus

Rugae

Pyloric sphinctermuscle

G Meyer ANHB – UWA

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Section through the stomach

Esophagus

Rugae

Pyloric sphinctermuscle

Three muscle layers

Duodenum

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Chemical digestion in theduodenum

Enzyme Product

Amylases Disaccharides→ glucose

Lipase Fats & oils→ fatty acids

+ glycerol

Trypsin Peptones→ 

polypeptides

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Mechanical processes in the

duodenum

Bile salts emulsify fats

(reduce them to smalldroplets which increases

their surface area).

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Inside the duodenum

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Chemical digestion in the smallintestine

Enzyme Product

Maltase LactaseSucrase

Maltose→ glucose Lactose→ glucose Sucrose→ glucose

Lipase Fats & oils→ fatty acids& glycerol

Peptidases Polypeptides→ amino

acids

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Absorption in the small intestine

• Glucose, amino acids, waterand minerals are absorbed into

the blood capillaries.

• Fatty acids and glycerol areabsorbed into the lacteals(forming chyle).

Section through small

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Section through smallintestine showing villi

L. Slomianka ANHB-UWA

Secretorycells

Villus

Gland

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Section through a villus

Lacteal

Network of bloodcapillaries

Epithelial cells &goblet cells

Lymph vessels

Intestinal gland

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Functions of the largeintestine

• Further absorption of water andsome salts.

• Bacterial activity – there are trillionsof resident bacteria in the largeintestine. They are believed to have

several important roles in additionto digesting cellulose in plant foodsand synthesising some vitamins(e.g. folic acid).

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The large intestine

Caecum

Appendix

Colon

(ascending branch)

Colon(transverse branch)

Colon(descending branch)

Rectum

LIVER

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Some major functions of theliver

Deaminates amino acids

Converts glucose to glycogen

Produces bile

Stores iron, and vitamins A, B12, D, E & K

Synthesises vitamin A & plasma proteins

Detoxifies drugs (including alcohol) andother toxins.

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Wellcome Photo Library

LiverStomach

Pancreas

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External features of the liver

Miles Kelly Art Library

Gall bladder

Bile duct

Hepatic artery

Hepatic portal vein

Inferior vena cava

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Liver lobule

Artery, vein& bile ductCentral vein

Lobule

L Slomianka ANHB-UWA