Unit 3: Animal Anatomy & Physiology

The Digestive System

Digestive System• responsible for 4 major functions:

1. ingestion• intake of nutrients (eating)

2. digestion• the breakdown of food into small soluble molecules

a) physical digestion: (ex.) chewing– mechanical digestion that cuts food into small pieces– smaller pieces increase surface area for enzymes to work on

Digestive System

4 major functions (continued):

b) chemical digestion: ex. digestive secretions (saliva)

• enzymes in digestive juices chemically breakdown food molecules into their monomers (soluble)

monomersfood

Digestive System

b) chemical digestion: (continued)

i) carbohydrates

i.e. polysaccharides

&

disaccharides

monosaccharides

Digestive System

b) chemical digestion (continued):

ii) proteins

amino acids

Digestive System

b) chemical digestion (continued):

iii) lipids

Digestive System

4 major functions (continued):3. absorption

• the uptake of nutrient molecules, first into the cells of the small intestine

• then into the blood stream

4. Egestion: • removal of solid undigested material (feces)

from anus eating cellulose (fiber) helps

** Excretion (part of the excretory system)• removal of liquid soluble waste (urine) from

the bladder via urethra

Components of the Digestive System

Mouth

Esophagus

Stomach

Small Intestine

Large Intestine

Rectum

Anus

Liver

PancreasGall Bladder

digestive tract (alimentary canal) really just a very long tube (~ 9 m long)takes food ~ 24 - 33 hours to go through digestive tract

Components of the Digestive System

Organ Comments Function

1. Mouth opening to digestive system

a) Teeth different shapes for tearing & grinding

ingestion

physical digestion

Mouth (Oral Cavity)

Components of the Digestive System

Teeth:

Molars (12)

Premolars or bicuspids(8)Canines (4)

Incisors (8)

Anatomy of the Mouth

Components of the Digestive SystemOrgan Comments Function

b) saliva made by 3 pairs of salivary glandssecrete saliva into oral cavity

contains:1.water:

2.mucus:

3.salivary amylase:

lubricates food (makes it slippery)

help to dissolve food

enzyme which digests starch

i.e. into mono & disaccharides

Parotid gland

Submandibular gland

Sublingual gland

Salivary GlandsSublingual glandParotid gland

Submandibular gland

Tongue

Mouth (oral cavity)

Components of the Digestive SystemOrgan Comments Function

c) tongue very strong musclecontains large numbers of taste budsbolus:

2. physical digestion: chewing & mixing food with saliva

1.sensory: taste & temperature control

3. swallowing: a. pushes bolus up &

to the back of the throat

nerve endings

.

ball of chewed food

b.causes epiglottis to block windpipe

4. speech

Components of the Digestive System

Tongue:• Different parts of the

tongue are able to taste one of four basic tastes.

sour

bitter

salty

sweet

NOT IN YOUR NOTESComponents of the Digestive System

Organ Comments Functiond) epiglottis

2) pharynx

flap of tissue at the base of the tongue above the trachea

back of the throat

prevents food from going into lungs (down trachea) to avoid choking

.

common passageway for food & air

Components of the Digestive SystemOrgan Comments Function

3) esophagus narrow tube about 24 cm long connecting pharynx to stomachcontains 2 muscle layers which relax and contract rhythmically for peristalsis

.

1. leads food into stomach

2. ensures that food (bolus) is pushed into stomach (mucus glands help lubricate the bolus)wave-like contractions

Esophagus (24 cm long, carries food)

• Lined with circular and longitudinal muscle• Lower end of esophagus is thickened just

before stomach (sphincter) (ie: heartburn)• Regurgitation – movement of food from the

stomach up the esophagus and out the mouth

SWALLOWING

StomachEsophagus Pharynx

Stomach

Stomach

• Glands:– Located in lining of stomach – Produce gastric juices which contain:

• (i) HCl – Chemical breakdown of fibrous tissue Kills bacteria

• (ii) Pepsin – Enzyme which breaks down proteins

• (iii) Mucus –Thick layer which protects stomach wall from acid and pepsin

Sphincters:

Small ring like muscles located at either end of the stomach• (i) Cardiac Sphincter – • Controls entry of food into stomach from esophagus• Closed during digestion to avoid re-entry into esophagus

(heart burn)• (ii) Pyloric Sphincter – • Controls entry of chyme (partially digested food & gastric

juices) into the small intestine

Components of the Digestive System

cardiac sphincter

pyloric sphincter

duodenum

circular muscles

oblique muscles

longitudinal muscles

Components of the Digestive Systemglands in stomach lining ulcer in stomach lining

ENDOSCOPE

ACID REFLUX

GASTRIC FOLDS STOMACH LINING & GASTRIC JUICE

ENDOSCOPE

STOMACH ULCER

MULTIPLE STOMACH ULCERS

Before food enters the small intestine:

• It must pass through the PYLORIC SPHINCTER which is a valve that contracts and relaxes to control the flow of food leaving the stomach and going to the small intestine.

Extra info in the next slides!

Components of the Digestive System

Kinds of Teeth Description Function

long & pointy sharp

rip/tear very developed in predators

wide, but very thin bumps on bottom edges

cut like knives for biting

flat & broad have 2 bumps on surfaces called cusps (bicuspids)

grinding & mashing

flat & broad have 4 cusps

grinding & mashing

Canines

Incisors

Premolars

Molars

Components of the Digestive System

periodontalmembrane

enamel

pulp (cavity)

root canal

nerve

arteryvein

dentin

crown(above gums) gingiva (gums)

root (under gums)

nerve endings

Salivary Glands

• Parotid Gland (below/ in front of ears, largest)

• Sublingual Gland (floor of mouth, smallest)

• Submandibular Gland (below and behind sublingual)

Ducts and Saliva

• Ducts – tubular canals for carrying glandular secretions from one part of the body to another.

• Saliva – Moisten and lubricate food– First step in chemical digestion