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), or mechanical.

Chemical digestion the breaking down of the nutrients we eat into simpler organic compounds that can be absorbed by the body.

Mechanical digestion is the breaking down of large sized food to smaller sized 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

Structure of the alimentary tube

Mucosa

Longitudinal muscle layer

Circular muscle layer

Peritoneum

Villus

SubmucosaThin muscle

layer

Chemical digestion in the mouth

Enzyme Product

Salivary amylase

Polysaccharides → Sugars

The salivary glands

Parotid gland

Submandibular glandSublingual gland

Section through the head

Nasal cavity

Palate

TonguePharynx

Hyoid bone

Epiglottis

Larynx

Esophagus

Teeth

Vocal cords

The Miles Kelly Art library, Wellcome Images

The tongue

Jari Keinänen

Mechanical processes in the mouth

Chewing (mastication)Bolus formationSwallowing

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

The Miles Kelly Art library, Wellcome Images

Incisor teeth

Premolar and molar teeth

Canine tooth

Human dentition

Molars Pre-molarsCanine

IncisorsGray’s Anatomy

Tooth section

EnamelDentine

Pulp cavity

Cementum

Gum

Root canal

Crown

Neck

Root

The Miles Kelly Art library, Wellcome Images

Swallowing and peristalsis

The Miles Kelly Art library, Wellcome Images

Epiglottis closes entrance to windpipe

Tongue pushes bolus into throat

Peristalsis carries bolus into stomach

Peristalsis

Wave-like contraction of the muscular wall travels along the gut

BOLUS

Chemical digestion in the stomach

Enzyme Product

Hydrochloric acid

Activates pepsinogen (→ pepsin)

Pepsin Proteins → peptones

Mechanical processes in the stomach

Muscular churning mixes food with gastric juices (forms chyme)

Rennin (in infants only) curdles milk

Absorption in the stomach

Limited absorption of water, glucose, alcohol and some drugs takes place in the stomach.

Section through the stomach

EsophagusFundus

Rugae

Pyloric sphincter muscle

G Meyer ANHB – UWA

Section through the stomach

Esophagus

Rugae

Pyloric sphincter muscle

Three muscle layers

Duodenum

Chemical digestion in the duodenum

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 small droplets which increases their surface area).

Inside the duodenum

Chemical digestion in the small intestine

Enzyme Product

MaltaseLactase Sucrase

Maltose → glucoseLactose → glucoseSucrose → glucose

Lipase Fats & oils → fatty acids & glycerol

Peptidases

Polypeptides → amino acids

Absorption in the small intestine

• Glucose, amino acids, water and minerals are absorbed into the blood capillaries.

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

Section through small intestine showing villi

L. Slomianka ANHB-UWA

Secretory cells

Villus

Gland

Section through a villus

Lacteal

Network of blood capillaries

Epithelial cells & goblet cells

Lymph vessels

Intestinal gland

Functions of the large intestine

• Further absorption of water and some salts.

• Bacterial activity – there are trillions of resident bacteria in the large intestine. They are believed to have several important roles in addition to digesting cellulose in plant foods and 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 the liver

Deaminates amino acidsConverts glucose to glycogenProduces bileStores iron, and vitamins A, B12, D, E & K

Synthesises vitamin A & plasma proteinsDetoxifies drugs (including alcohol) and

other toxins.

Wellcome Photo Library

LiverStomachPancreas

External features of the liver

Miles Kelly Art Library

Gall bladderBile duct

Hepatic artery

Hepatic portal vein

Inferior vena cava

Liver lobuleArtery, vein & bile duct

Central vein

Lobule

L. Slomianka ANHB-UWA