Chapter 17: The Digestive System

CHAPTER 17: THE DIGESTIVE SYSTEM

VERY Basic

But first… A video http://

www.youtube.com/watch?v=bfOyLuknD_4

Alimentary Canal Extends from the mouth to the anus

MouthPharynxEsophagusStomachSmall and large intestineRectumAnus

Accessory organs Salivary glandsLiverGall bladderPancreas

Layers of the Wall Mucosa (mucous membrane)

Epithelium, connective tissue and smooth muscle Secretion and absorption

Submucosa Loose connective tissue, blood vessels, lymphatic vessels,

nerves Nourishment, transport absorbed materials

Muscular layer Smooth muscle in circular and longitudinal groups Movement of the tube and its contents

Serosa Epithelium, connective tissue Protection

Movements of the Alimentary Canal Mixing Segmentation Peristalsis

Mouth Site of both mechanical

and chemical digestionTeeth and chewing

(mastication)

Mouth Tongue: root, body

Lingual frenulum Uvula – extension of

soft palateDivision between the

pharynx and the nasal cavity

Tonsils (lymphatic tissue)PalatineLingual Pharyngeal

Teeth Incisor Canine Premolar Molar

Adult has 32 teeth (permanent) Children have 20 teeth (deciduous)

Pharynx and Esophagus Neither are involved in digestion Epiglottis

Pharynx Connects the nasal and oral cavities

with the larynx and esophagus

Skeletal muscles control swallowingUnder voluntary control

Swallowing 3 stages:

1. Food is chewed and mixed with saliva○ Formation of a bolus

2. Food is pushed to the pharynx to enter the esophagus

○ Triggers a swallowing reflex3. Peristalsis transports food from

esophagus to stomach

Esophagus Connects mouth to stomach

Lined with mucous glands

Cardiac sphincter (Lower esophageal sphincter)

Recap Food enters the mouth…then what?

What types of digestion takes place?

What organs/structures are involved?

Is it voluntary or involuntary?

Stomach Receives food from the esophagus Digestion

Muscle fibers run in all directionsCircularLongitudinalOblique

Very minimal absorption

Stomach Inner lining: rugae – thick folds Greater curvature Lesser curvature Regions of the stomach:

Cardia FundusBodyPylorus

Pyloric sphincter

Stomach As the food is

digested, it changes from a bolus (from the mouth and esophagus) to chymeChyme

○ Semifluid paste ○ Food mixed with

digestive enzymes

Accessory Organs Pancreas Liver Gall Bladder

Pancreas Secretion of pancreas juice Aids in digestion of

CarbohydratesFatsProteinNucleic acid

Liver Multi lobed

Makes bileDigestion of fats

Liver

Gall Bladder

Connected to the liver Storage and release of bile into small

intestine

Small Intestine Fills most of the abdominal cavity 5.5 – 6 meters long Receives secretions from pancreas, liver Absorption

Small Intestine Duodenum Jejunum

VascularThicker wall

Ileum High number of

lymph nodes (Peyer’s patches)

Small Intestine Mesentary

Connective tissue around the small intestine Greater omentum

Membrane drapes over lower digestive tractIf infection occurs, omentum will seal off

portion of digestive systemPrevents spread of infection to abdominal

cavity

Greater Omentum

Small Intestine Villi

Projections to increase surface area

Large Intestine Joins small intestine at the ileum

Water and electrolyte absorption Formation of feces

Large Intestine Cecum

Appendix – projection from cecum Colon:

AscendingTransverseDescendingSigmoid

Rectum Anus

Digestive Enzyme Table

Digestive System Dissection