11. Unit 2A Digestive System

8/3/2019 11. Unit 2A Digestive System

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Unit 2A

Human Form & Function

Body systems

The digestive system



Study Guide

Read :

• Text

page 87- 98 Complete :

• RQ 5-13

• AYK 1-8



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.



ENZYME Acts on End product

Amylase Carbo-hydrate

Simple sugars(e.g. glucose)

Lipase Lipids Fatty acids

Protease Proteins Amino acids



The anatomy of the digestive system

US Govt NIH

http://upload.wikimedia.org/wikipedia/commons/0/04/Stomach_colon_rectum_diagram.gif



Structure of the alimentary tube

Mucosa

Longitudinal

muscle layer

Circularmuscle layer

Peritoneum

Villus

SubmucosaThin muscle

layer



Chemical digestion in the mouth

Enzyme Product

Salivary

amylase

Polysaccharides

→ Sugars



The salivary glands

Parotidgland

Submandibulargland

Sublingualgland



Section through the head

Nasal cavity

Palate

Tongue

Pharynx

Hyoid bone

Epiglottis

Larynx

Esophagus

Teeth

Vocal cords

The Miles Kelly Art library, Wellcome Images



The tongue

Jari Keinänen



Mechanical processes in themouth

Chewing (mastication)Bolus formation

Swallowing



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


Incisor teeth

Premolar andmolar teeth

Canine tooth



Human dentition

Molars Pre-molarsCanine

Incisors

Gray’s Anatomy



Tooth section

EnamelDentine

Pulp cavity

Cementum

Gum

Root canal

Crown

Neck

Root




Swallowing and peristalsis


Epiglottis closesentrance to windpipe

Tongue pushes bolusinto throat

Peristalsis carriesbolus into stomach





Chemical digestion in thestomach

Enzyme Product

Hydrochloricacid

Activatespepsinogen (→

pepsin)Pepsin Proteins→ peptones



Mechanical processes in thestomach

Muscular churning mixes food

with gastric juices (formschyme)

Rennin (in infants only) curdlesmilk



Absorption in the stomach

Limited absorption of

water, glucose, alcoholand some drugs takes

place in the stomach.



Section through the stomach

EsophagusFundus

Rugae

Pyloric sphinctermuscle

G Meyer ANHB – UWA



Section through the stomach

Esophagus

Rugae

Pyloric sphinctermuscle

Three muscle layers

Duodenum



Chemical digestion in theduodenum

Enzyme Product

Amylases Disaccharides→ glucose

Lipase Fats & oils→ fatty acids

+ glycerol

Trypsin Peptones→

polypeptides



Mechanical processes in the

duodenum

Bile salts emulsify fats

(reduce them to smalldroplets which increases

their surface area).



Inside the duodenum



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



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



Section through smallintestine showing villi

L. Slomianka ANHB-UWA

Secretorycells

Villus

Gland



Section through a villus

Lacteal

Network of bloodcapillaries

Epithelial cells &goblet cells

Lymph vessels

Intestinal gland



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).



The large intestine

Caecum

Appendix

Colon

(ascending branch)

Colon(transverse branch)

Colon(descending branch)

Rectum

LIVER



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.



Wellcome Photo Library

LiverStomach

Pancreas



External features of the liver

Miles Kelly Art Library

Gall bladder

Bile duct

Hepatic artery

Hepatic portal vein

Inferior vena cava



Liver lobule

Artery, vein& bile ductCentral vein

Lobule

L Slomianka ANHB-UWA

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11. Unit 2A Digestive System