Transcript ch 15 Day 1 Mouth thru Esophagus

The Digestive System
Day 1
Introduction

 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 anus
 Accessory Organs:
 Salivary glands, liver, gallbladder and pancreas
Covers 186 square meters
Intro Cont.

 Digestion:
 The chemical and mechanical breakdown of foods and
the absorption of the resulting nutrients by cells.
 Mechanical Digestion
 Breaks large pieces into smaller ones without altering
the chemical composition
 Chemical Digestion:
 Breaks food into simpler chemicals
General Characteristics

 Alimentary Canal
 Muscular tube, roughly 8 meters in length
 Structure of the Wall
 4 layers




Mucosa Membrane
Submucosa
Muscular Layer
Serosa
Mucosa Membrane

 Made up of epithelium, connective tissue and small
amounts of smooth muscle
 Contains folds or tiny projections that extend into
the passageway called LUMEN
 Increase absorptive surface are
 Secrete mucus and digestive enzymes
 Protects tissues beneath it and
carries on secretion and absorption
Submucosa Layer

 Made up of loose connective tissue, glands, blood
vessels, lymphatic vessels, and nerves
 Nourishes surrounding tissues and carries away
absorbed materials
Muscular Layer
 Produces movements of the 
tube
 Contains two types of smooth
muscle
 Circular Fibers
 Contraction causes decrease
in tube’s diameter
 Longitudinal Fibers
 Contraction leads to
shortening of tube
Serosa Layer

 Outer covering
 Also called visceral
peritoneum
 Protect underlying tissues
and secrete serous fluid
which moistens and lubricates
tube’s outer surface
 Allows other organs in
abdominal cavity to slide
freely against one another
Movements of the Tube

 Two types of motor movements
 Mixing Movements
 Caused by smooth muscle contracts rhythmically
 Segmentation: alternately contracting and relaxing the
smooth muscle in nonadjacent segments
 Occurs in stomach
 Propelling movements
 Peristalsis: wavelike motion that pushes contents of tube
ahead
 Occurs in esophagus and intestines
Mouth

 Receives food and begins digestion by mechanically
breaking up solid particles and mixing them with
saliva
 Mastication
Cheeks and Lips

 Cheeks
 Form lateral walls of mouth
 Lips
 Contain sensory receptors that judge temp. and
texture of food
Tongue

 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 food
 Lingual Frenulum
 Connects tongue to floor of mouth
 Lingual Tonsils: Posterior portion
 Lymphatic tissue
Palate

 Forms roof of oral cavity
 Anterior portion-hard palate
 Muscular posterior portion-soft palate
 Uvula
 Cone-shaped projection in back of mouth
 Palatine Tonsils and Pharyngeal Tonsils-adenoids
 Masses of lymphatic tissues that protect the body
against infection
 Commonly removed
Teeth
 Two Sets

 Primary Teeth-deciduous
 20
 Erupt though gums in regular
intervals from 6 months-2-4 years
of age
 Usually shed in the same
order they erupted
 Secondary Teeth
 Push primary teeth out of sockets
 32
 Erupt 6 years-17-25 years with wisdom teeth
Teeth Cont.
 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 effectively
 Parts to a tooth
 Crown-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

Salivary Glands

 Secrete saliva that helps moisten and bind food
particles
 Begins chemical digestion by enzyme amylase
 Helps cleanse the mouth and teeth
Salivary Secretions

 Each gland has two types of secretory cells
 Serous
 Produce a watery fluid that includes digestive enzyme
salivary amylase
 Enzyme splits carbohydrates
 Mucous
 Secretes thick liquid called mucus
 Binds food particles and lubricates food during
swallowing
 Saliva is produced just by thinking of good foods
 Saliva stops production in the presence of unpleasant
smells or tastes
Major Salivary Glands

 Three Pairs
 Parotid Glands
 largest
 Lies anterior and somewhat
inferior to ears
 Found between skin, cheeks, and
masseter muscle
 Secretes clear, water fluid that is
rich in amylase
Major Salivary Glands

 Submandibular
Gland
 Located on floor
of mouth
 Secretes both
mucous and
serous fluid
Major Salivary Glands

 Sublingual glands
 Smallest
 On the floor of
mouth inferior
to the tongue
 Secretes
primarily
mucous type
making their
secretions thick
and stringy
Pharynx-The Crossroads

 Cavity posterior to mouth which leads to esophagus
 Do not digest food but functions in swallowing
 Connects nasal and oral cavities with the larynx and
esophagus
Pharynx Cont.

 Three parts:
 Nasopharynx-communicates with nasal cavity and
provides a passageway for air during breathing,
auditory tube connects to nasopharynx
 Oropharynx-posterior to soft palate and inferior to
nasopharynx, allows food and air to pass through
 Laryngopharynx- inferior to oropharynx, passage way
to esophagus
Swallowing Mechanism
 3 Stages

 1. Food is mixed with saliva, tongue rolls mixture into
a mass called bolus, forces bolus into oropharynx
 2. Once food reaches oropharynx, swallowing reflex
kicks in (See steps on Page 409)
 3. Peristalsis transports food into esophagus and on to
the stomach
Esophagus

 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 Sphincter
 Closes the entrance to stomach preventing contents
from regurgitating into esophagus.
 Peristaltic waves allow food to enter stomach.
Review Questions

 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?