Human Anatomy & Physiology, Sixth Edition
Elaine . !arieb
PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky
23 The i!estive Syste"
Digestive System: Overview
digests and absorbs &ood
stomach, small intestine, and large intestine
'ccessory digesti*e organs ( teeth, tongue,
gallbladder, sali*ary glands, li*er, and pancreas
 
Digestive System: Overview
Digestive Process
 utrients become more a*ailable to the body in
each step
Ingestion, propulsion, and mechanical digestion
Chemical digestion, absorption, and de&ecation
 
Digestive Process
Gastrointestinal Tract Activities
Propulsion ( salloing and peristalsis
Peristalsis ( a*es o& contraction and rela)ation o&
muscles in the organ alls
!echanical digestion ( cheing, mi)ing, and
churning &ood
Peristalsis and Segmentation
Gastrointestinal Tract Activities
'bsorption ( mo*ement o& nutrients &rom the $I
tract to the blood or lymph
3e&ecation ( elimination o& indigestible solid astes
 
GI Tract
egulation o& digestion in*ol*es
!echanical and chemical stimuli ( stretch
receptors, osmolarity, and presence o& substrate in
the lumen
Intrinsic control by local centers
 
ece!tors o" the GI Tract
!echano6 and chemoreceptors respond to
5tretch, osmolarity, and p7
"hey initiate re&le)es that
'cti*ate or inhibit digesti*e glands
!i) lumen contents and mo*e them along
 
#ervous $ontrol o" the GI Tract
Intrinsic controls
re&le)es
 ple)uses #gut brain%
8ong re&le)es arising ithin or outside the $I tract
In*ol*e C5 centers and e)trinsic autonomic
ner*es
#ervous $ontrol o" the GI Tract
+igure 2.4
Peritoneum and Peritoneal $avity
ca*ity
9isceral ( co*ers e)ternal sur&ace o& most digesti*e
organs
Peritoneal ca*ity
 
Peritoneum and Peritoneal $avity
Peritoneum and Peritoneal $avity
 pro*ides
' means to hold digesti*e organs in place and store
&at
 peritoneum
Peritoneum and Peritoneal $avity
%lood Su!!ly: S!lanchnic $irculation
"he hepatic, splenic, and le&t gastric spleen, li*er,
and stomach
intestines
digesti*e *iscera
3eli*ers this blood to the li*er &or metabolic
 processing and storage
Histology o" the Alimentary $anal
+rom esophagus to the anal canal the alls o& the $I
tract ha*e the same &our tunics
+rom the lumen outard they are the mucosa,
submucosa, muscularis e)terna, and serosa
Each tunic has a predominant tissue type and a
speci&ic digesti*e &unction
 
Histology o" the Alimentary $anal
+igure 2.;
ucosa
alimentary canal
5ecretion o& mucus
Protection against in&ectious disease
Consists o& three layers a lining epithelium, lamina
 propria, and muscularis mucosae
ucosa: '!ithelial (ining
Consists o& simple columnar epithelium and mucus6 secreting goblet cells
"he mucus secretions
Ease &ood along the tract
5tomach and small intestine mucosa contain
En<yme6secreting cells
 
8amina Propria
 ourishes the epithelium and absorbs nutrients
Contains lymph nodes #part o& !'8"% important in
de&ense against bacteria
ucosa: (amina Pro!ria and uscularis
ucosae
ucosa: Other Su)layers
elastic &ibers, blood and lymphatic *essels, lymph
nodes, and ner*es
and peristalsis
eplaced by the &ibrous ad*entitia in the esophagus
etroperitoneal organs ha*e both an ad*entitia and
serosa
'nteric #ervous System
5ubmucosal ner*e ple)us ( regulates glands and
smooth muscle in the mucosa
!yenteric ner*e ple)us ( !ajor ner*e supply that
controls $I tract mobility
in*ol*ing local re&le) arcs
 
outh
Is bounded by lips, chee1s, palate, and tongue
7as the oral ori&ice as its anterior opening
Is continuous ith the oropharyn) posteriorly
"o ithstand abrasions
epithelium
"he gums, hard palate, and dorsum o& the tongue are
slightly 1eratini<ed
Anatomy o" the Oral $avity: outh
+igure 2.?a
(i!s and $hee*s
8ips orbicularis oris
e)ternally, and teeth and gums internally
=ral ca*ity proper ( area that lies ithin the teeth
and gums
aspect o& each lip to the gum
 
Oral $avity and Pharyn+: Anterior iew
+igure 2.?b
Palate
 palatine processes o& the ma)illae
'ssists the tongue in cheing
5lightly corrugated on either side o& the raphe
#midline ridge%
Palate
muscle
@*ula projects donard &rom its &ree edge
Palatoglossal and palatopharyngeal arches &orm the
 borders o& the &auces
Tongue
=ccupies the &loor o& the mouth and &ills the oral
ca*ity hen mouth is closed
+unctions include
!i)ing &ood ith sali*a and &orming the bolus
Initiation o& salloing, and speech
 
Tongue
E)trinsic muscles alter the tongueAs position
8ingual &renulum secures the tongue to the &loor o&
the mouth
Tongue
5uperior sur&ace bears three types o& papillae
+ili&orm ( gi*e the tongue roughness and pro*ide &riction
+ungi&orm ( scattered idely o*er the tongue and gi*e it a reddish hue
Circum*allate ( 96shaped ro in bac1 o& tongue
5ulcus terminalis ( groo*e that separates the tongue into to areas
'nterior 2 residing in the oral ca*ity
Posterior third residing in the oropharyn)
 
Tongue
Salivary Glands
Cleanses the mouth
'ids in bolus &ormation
"hree pairs o& e)trinsic glands ( parotid,
submandibular, and sublingual
throughout the oral mucosa
Salivary Glands
Parotid ( lies anterior to the ear beteen the masseter muscle and s1in
Parotid duct ( opens into the *estibule ne)t to the second upper molar 
5ubmandibular ( lies along the medial aspect o& the mandibular body
Its ducts open at the base o& the lingual &renulum
5ublingual ( lies anterior to the submandibular gland under the tongue
 
Salivary Glands
Saliva: Source and $om!osition
glands
solution containing
 ( 
Proteins ( mucin, lyso<yme, de&ensins, and Ig'
!etabolic astes ( urea and uric acid
 
$ontrol o" Salivation
E)trinsic sali*ary glands secrete serous, en<yme6rich
sali*a in response to
Ingested &ood hich stimulates chemoreceptors and
 pressoreceptors
and results in dry mouth
 
Teeth
Primary and permanent dentitions ha*e &ormed by age 2-
Primary ( 20 deciduous teeth that erupt at inter*als  beteen ; and 24 months
Permanent ( enlarge and de*elop causing the root o& deciduous teeth to be resorbed and &all out beteen the ages o& ; and -2 years
'll but the third molars ha*e erupted by the end o& adolescence
"here are usually 2 permanent teeth
 
Deciduous Teeth
Permanent Teeth
$lassi"ication o" Teeth
"eeth are classi&ied according to their shape and &unction
Incisors ( chisel6shaped teeth adapted &or cutting or nipping
Canines ( conical or &angli1e teeth that tear or  pierce
Premolars #bicuspids% and molars ( ha*e broad crons ith rounded tips and are best suited &or grinding or crushing
 
Dental -ormula: Permanent Teeth
relati*e position o& teeth
Hritten as ratio o& upper to loer teeth &or the
mouth
Permanent 2I, -C, 2P! #premolars%, !
2I -C 2P! !
 
Tooth Structure
"o main regions ( cron and the root
Cron ( e)posed part o& the tooth abo*e the gingi*a
#gum%
calcium salts and hydro)yapatite crystals is the
hardest substance in the body
Encapsules the cron o& the tooth
 
Tooth Structure
together 
Co*ers the root
 
Tooth Structure
Periodontal ligament
'nchors the tooth in the al*eolus o& the ja
+orms the &ibrous joint called a gomaphosis
$ingi*al sulcus ( depression here the gingi*a
 borders the tooth
Tooth Structure
3entin ( boneli1e material deep to the enamel cap that &orms the bul1 o& the tooth
Pulp ca*ity ( ca*ity surrounded by dentin that contains pulp
Pulp ( connecti*e tissue, blood *essels, and ner*es
oot canal ( portion o& the pulp ca*ity that e)tends into the root
'pical &oramen ( pro)imal opening to the root canal
=dontoblasts ( secrete and maintain dentin throughout li&e
 
Tooth Structure
+igure 2.--
Tooth and Gum Disease
and dentin by bacterial action
3ental pla>ue, a &ilm o& sugar, bacteria, and mouth
debris, adheres to teeth
dissol*es calcium salts
 proteolytic en<ymes
remo*ing &orming pla>ue
 
Tooth and Gum Disease: Periodontitis
$ingi*itis ( as pla>ue accumulates, it calci&ies and
&orms calculus, or tartar 
'ccumulation o& calculus
3isrupts the seal beteen the gingi*ae and the teeth
Puts the gums at ris1 &or in&ection
Periodontitis ( serious gum disease resulting &rom an
immune response
dissol*ing bone