Chapter 15 The Digestive System - PowerPoint Presentation

Slide1

Chapter 15

The Digestive SystemDay 1

Slide2

Digestive System:

Made up of the alimentary canal which extends from the mouth to anus

Includes:

Mouth, pharynx, esophagus, stomach, small intestine, large intestine,

recturm, and anusAccessory Organs:Salivary glands, liver, gallbladder and pancreasCovers 186 square meters

Introduction

Slide3

Digestion:The chemical and mechanical breakdown of foods and the absorption of the resulting nutrients by cells.

Mechanical DigestionBreaks large pieces into smaller ones without altering the chemical compositionChemical Digestion:Breaks food into simpler chemicals

Intro Cont.

Slide4

Alimentary CanalMuscular tube, roughly 8 meters in length

Structure of the Wall4 layersMucosa MembraneSubmucosa

Muscular Layer

Serosa

General Characteristics

Slide5

Made up of epithelium, connective tissue and small amounts of smooth muscle

Contains folds or tiny projections that extend into the passageway called LUMENIncrease absorptive surface areSecrete mucus and digestive enzymesProtects tissues beneath it and

carries on secretion and absorption

Mucosa Membrane

Slide6

Made up of loose connective tissue, glands, blood vessels, lymphatic vessels, and nerves

Nourishes surrounding tissues and carries away absorbed materialsSubmucosa

Layer

Slide7

Produces movements of the tube

Contains two types of smooth muscleCircular FibersContraction causes decrease in tube’s diameterLongitudinal FibersContraction leads to shortening of tube

Muscular Layer

Slide8

Outer coveringAlso called visceral peritoneum

Protect underlying tissues and secrete serous fluid which moistens and lubricates tube’s outer surfaceAllows other organs in abdominal cavity to slide freely against one another

Serosa Layer

Slide9

Two types of motor movementsMixing Movements

Caused by smooth muscle contracts rhythmicallySegmentation: alternately contracting and relaxing the smooth muscle in nonadjacent segmentsOccurs in stomachPropelling movements

Peristalsis: wavelike motion that pushes contents of tube ahead

Occurs in esophagus and intestines

Movements of the Tube

Slide10

Receives food and begins digestion by mechanically breaking up solid particles and mixing them with saliva

MasticationMouth

Slide11

CheeksForm lateral walls of mouth

LipsContain sensory receptors that judge temp. and texture of food

Cheeks

and Lips

Slide12

Fills

oral cavity

Responsible for mixing food with saliva and moving food towards pharynx during swallowing

Papillae

Rough projections on tongue that provide friction to help handle foodLingual FrenulumConnects tongue to floor of mouthLingual Tonsils: Posterior portionLymphatic tissue

Tongue

Slide13

Forms roof of oral cavity

Anterior portion-hard palateMuscular posterior portion-soft palateUvulaCone-shaped projection in back of mouthPalatine Tonsils and Pharyngeal Tonsils-adenoids

Masses of lymphatic tissues that protect the body against infection

Commonly removed

Palate

Slide14

Two Sets

Primary Teeth-deciduous20Erupt though gums in regular intervals from 6 months-2-4 years

of age

Usually shed in the same

order they erupted Secondary TeethPush primary teeth out of sockets32Erupt 6 years-17-25 years with wisdom teethTeeth

Slide15

Role in digestion

Begin mechanical digestion by breaking

food into smaller pieces

Increases surface area of food to allow

for digestive enzymes to work more effectivelyParts to a toothCrown-projects beyond gum

Root-

below gums

Neck

-portion where crown and root meet

Enamel

-glossy white, covers crown, consists of calcium salts, hardest substance in body, never replaced when damaged

Dentin

-bulk of tooth beneath enamel

Pulp

-contains blood vessels, nerves, and connective tissue

Root Canals

-area where blood vessels and nerves reach pulp

Cementum

-bonelike material that helps attach tooth to jaw

Periodontal Ligament

-contains blood vessels and helps attached tooth to jaw

Teeth Cont.

Slide16

Secrete saliva that helps moisten and bind food particlesBegins chemical digestion by enzyme amylase

Helps cleanse the mouth and teethSalivary Glands

Slide17

Each gland has two types of secretory cells

SerousProduce a watery fluid that includes digestive enzyme salivary amylaseEnzyme splits carbohydratesMucous

Secretes thick liquid called mucus

Binds food particles and lubricates food during swallowing

Saliva is produced just by thinking of good foodsSaliva stops production in the presence of unpleasant smells or tastesSalivary Secretions

Slide18

Three Pairs

Parotid GlandslargestLies anterior and somewhat inferior to earsFound between skin, cheeks, and masseter muscleSecretes clear, water fluid that is rich in amylase

Major Salivary Glands

Slide19

Submandibular Gland

Located on floor of mouthSecretes both mucous and serous fluid

Major Salivary Glands

Slide20

Sublingual glands

SmallestOn the floor of mouth inferior to the tongueSecretes primarily mucous type making their secretions thick and stringy

Major Salivary Glands

Slide21

Cavity posterior to mouth which leads to esophagus

Do not digest food but functions in swallowingConnects nasal and oral cavities with the larynx and esophagusPharynx-The Crossroads

Slide22

Three parts:Nasopharynx

-communicates with nasal cavity and provides a passageway for air during breathing, auditory tube connects to nasopharynxOropharynx-posterior to soft palate and inferior to nasopharynx

, allows food and air to pass through

Laryngopharynx- inferior to oropharynx, passage way to esophagus

Pharynx Cont.

Slide23

3 Stages

1. Food is mixed with saliva, tongue rolls mixture into a mass called bolus, forces bolus into oropharynx2. Once food reaches oropharynx, swallowing reflex kicks in (See steps on Page 409)3. Peristalsis transports food into esophagus and on to the stomach

Swallowing Mechanism

Slide24

Straight, collapsible tube about 25 cm long that allows food to pass from mouth to stomach

Mucous glands are scattered throughout Lower Esophageal Sphincter/Cardiac SphincterCloses the entrance to stomach preventing contents from regurgitating into esophagus.Peristaltic waves allow food to enter stomach.

Esophagus

Slide25

Which organs constitute the digestive system?

Describe the wall of the alimentary canal.Name the two basic types of movements in the alimentary canal.How does the tongue function as part of the digestive system?Where are the tonsils located?

How do primary teeth differ from secondary teeth?

Describe the structure of a tooth.

Explain how a tooth is attached to the bone of the jaw.What is the function of saliva?What stimulates salivary glands to secrete saliva?Where are the major salivary glands?Describe the regions of the pharynx.List the major events of swallowing.What is the function of the esophagus?

Review Questions