digestive tract diagram - Morgan Park High School
ba digptiw vstmn plovidcs thc: bsdy with the nutrihealth, lEc organs of this q s t e t n ingest, dipst, ax! absatb food and tlimlnato the undigested nm&s as focu.
T ~ digestive
g y m con~igtsof a hollow tube exunding
fmm the mouth to thc anus, into which a n m b r of rrcccssory
orgm or g l a d mpty their mmtims (Fiprc 25.1). Fsod
witbin this tub,thC ialimcntary canal, is mhnically otltside
the body b m u c it hns mapct wily with the =Us lining Ihc
tract B e f a ingested food is available to the body ctlls, it
must be broken down phytically (chewing, churning) curd
chnnically ( c n q m t i c hybjysis) into its smaIltr difE~1i~ible
rnolcxules-a p m s called digestion. The digested end
paducts can t h pass b u g h thc epithelial ctlh lining the
a ~ ~ into
c t the b l d w be bedistributed to the body w l l s A
proms temwd mbEarpth3n.
The organs of tbe digestive system an stparaVd inta two
mjur group: the olim~ltarycanal, EW gastrolnt&iml
(GI)tract, and tbo jtamm~ydlpcstfvt orgat%.The alimantasy canal consists of dK. moulfi, pharynx, esophagus, stomach, small and large intestfnes, aMt anus. Thc nccc?ssory m c tm inelude the teeth atld the salivary glaods, gallbladder,
liver, and purcrcatl, which nhe their p d n c t s into the alimtntary canal. Thtot individual organs srt described s W y .
Tht human d m *
gallbladder are ~
d to the right.)
l i ~ u tube
Observing the Histological Structure
of the Alimentary Canal Wall
Go to the Demonstration area where a cross section of the
duodtnum (part of tfu: md intestine) is secured to the microscope stage. Observe the tissue to identify the four basic
tunics of tht intestinal wall-that is, the m u c m (and its
three sublayes), the subrnucosrr (connective tissue layer
deep t~ the mucm), the muscularis externa (composed of
circular md longitudinal smooth muscle layers), and the
s e r m (the outermost layer). Examine the large l&e
which increase the surface area for absorption. Consult Figure 25.2 and Plate 39 in the Histology Atlas as you work.
What type of epithelium do you see here?
Organs of the Alimentary
O b j e c t i v a 2 : Identlfyonamodelorappropriate
diagwn the organs that make up the alimentary canal rmnd indicate the digestive role of each organ.
Figure 25.3 ~ h mouth
( M ~ I~ ~ i t y ) .
(a) Anterior view of the mouth. (b) Sagittal
view of the mouth and pharynx.
Identifying Alimentary Canal Organs
The pathway that food takes as it passes through the alimentary canal organs is described in the next sections. Identify
tach structure in Figure 25.1 and on the torso model as you
Mouth or Oral Cavity
Food enters the digestive tract though the mouth, cir oral
cavity (Figure 25.3). Within this mucous-membrane-lined
cavity are the gums, teeth, and tongue. The lips (labia) protect its anterior opening, the cheeks form its lateral walls, and
the palate, its m f . Thc anterior part of the palate is called the
bard prlrrte Ixcause bone underlies it. The posterior soh
palate is unsupported by bone. The uvula, a f m g d k e projection of the soft palate. extends inferiorly from its posterior
edge. The soft palate rises to close off the oral cavity f m the
nasal and pharyngeal passages during swallowing. The mucuIar tongue occupies the floor of the oral cavity. A mrmb e , the frenulum, secures the tongue to tht floor of the
mwth (Figwe 25.3b). The space between the lips and ch&
and the teeth is the vestibuk; the a m that lies within the
tccth md gums is the oral cavity proper.
On each side of the mouth at its postmior end are masses
of lymphoid tissue, the palatine tonsib (Figure 25.3). Tht
lingual tonsil covers the base of the tmgue, posterior to the
oral cavity proper.T b tonsils, along with other lymphoid tissues, rue p u t of the body's defense system. For histology of
the palatine tonsils see Plate 3 1 in the Histolagy Atlas.
FuhCtlo~lArUltomy of the Dlgcrtivt System
C m m n hepatic duct
'fhrce, p h of salfv~t'[email protected] b
saliva, into the oral cavity. One cmponcnt of saliva, salivary
m y h e , begins the digestion of starchy f d in thl: mouth.
(The salivary glmds art discussed in Inon: &tail on pages
As fsod e n m the mth, it is mixcd with d i v a d
masticated (chewed). Ihc c k k a and lips help hold the fuod
between the teeth during mastication. The mobile tongue
mixes the foal with d i v a dmhg chewing and initiates swarllowing. Thus the mechanical and chemical breakdown of
food begins befm the food has left the mouth. As noted in
Exercise 17, the surface of the tongut irr covered with papillm, many of which con& mte buds.
From thc mouth, food
terioriy iato the pharynx, a
uid, and air ( F i p 25.3).
Tho pharyax hns three parts-the nasopharym (behind the
nasal cavity), the ompharynx (extends from the soft palm
la the epiglottis), and the larynebp-m
(entends from tfiE
e ~ i
?XMof the larynx), which is continuaus with
of dxr phmynx umta5-1two lym of skclctal
musck: an kux?r l c l n @ M layer and an outer laya of circular constrictor mwlds. Thtse muscles
The esophmgm, or gullet, extends from the pharynx through
the diaphnrgm to the stomach. It is approximately 10 inches
long in humans iand is basically a fwd pssapwtty that conductis fcud to the stomach by prisrals~.At its superior
muscle in the m a nearing rht ~tomrtch. The cardtoesophageal sphlacter, a thickening of the smooth muscle
layer at dte esophagus-stomach jamion, conmls food pas
sage into the starnwh (setFigum 25.4).
25.1 mi 25.4) is on the left side of thr
abdominal cavity and is hiddm by the livm ilnd dLpimqm
Different mgiona of rht saclike sromwh art the cardiac region (the area ~urroundingthd opening though which f&
en&= the stomach), the hlllCl~
(the expanded portion of the
stomach, lateral to the cardiac regian), tht Boay (midpart of
thd stomach), and tfte pylor~g(the tCrminal put of the stomach, which is c m t i n u ~ l with
s ffK; small intestine through the
The concave medial surface of the stomach is tfit laset
m t u r e ; its convex lateral surface is the greater cumhue, Extending from these curvatures m two meSQntCfies,
call& omem. The leser omenturn extend8 from the liver tn
the lesser curraturt. TIw g r a t e r omenturn extends from the
p t m curvahue of the stomch, drtapta downward o v a thc
abdominal contents to cover tkem in an apronlike fashion,
and tha attaches ta the posterior body wall. Figure 25.7
( p g e 220) illustrakca the omcnta as well a8 ths othtr peritoneal attachments of the abdominal organs.
The stomach is a tempomy storage ngion for food as
well as a site foi food breakdown. It contains a third oblique&
oriented Iayer of m w t h muscle in its muscularis axtnna thrrf
a l l ~ w sit to churn, mix, and pummel the food, physicdally
breaking it down to smaller
ts. Gasm't gl&
m u m a sitcma hydrochloric acid md hydrulytk wymeo.
intwtIna, A &on
M the c w m k r e m o d to rhaw the ilcoctul ah.
cal caUections of lymphaid srsdulcs found in the submueossl
called PFJW'S patdws increase along the length of the small
intestine (so*Plate 41 in th?e Mstalogy Atlas).
A c t i v i t y 3:
Examining the Villus Model
lf r villus llwQl is available, identify the following ceh or
regions kfm cantinuing: epithelium, goblet cclle, l d n n
propria, slips of the muscald mu-,
capillmy W, and
Thd: fPlrpe intestine (see Figure 25.6)b abut 1.3 m (3 fmt)
long and extends fran dr+ ilescaeal vdve to the mur;.It cone
sba d tfit fallawing sutxiivioians: the wyw, appmdlr,
ncrum, snd anal caw
The colon has severel regions. "Phe ascending colon
trawls up the right side of the ahdomind cavity and makes a
right-angle turn u the ri&t ~ d (b~potlc)
ntmm to w
the iBdaminal cavity are the tsirnsrctec colon. It then wna pt
the left colk (splenic) llcrmn atld centinws downward as
the descending colan, w h it becomes Ulc S-&aped stp
d d ah.Ttks signadd wIm, m m , Bnd tht sural @anal
lie in the pelvis bnd thus an nor ctvnaidcrod kWominal cavity
body cxtcrim T k anus, which has an t x d spbincttr d
skeletal muscle (the voluntary sphincter) and an internal
s p h b c r of m t h muscle (the hvolunmy sphincter), is
normally cia& c x q t during daft~ationwkn fbeer m
olimlaaesd fram thc M y ,
In thr, large inteathe, the l o n muscle
~ of thc
mascdatis cxtcrnn is reducod to thra muscle bands.T k e
b a n d s a n ~ c r t h a n h r r a t e the
f wdloftblargeinrtstine, so they ctww tho wall to pucker into s m d . ~ W - @ .
sack cdL1ed Eurrzstra,
Tha major function of the large intestine i8 to c
aad ptopel the fecal intow& tht anus mi to tliminata
it from the body. While it docs that chon, it (1) providts a
site far intcstid bacteria to rnsnuf8caue m e vitamins (a,
and K),which it thon &%arbinto 'the bloodstnm; and (2)
~ e @ l a hm
a a t of the remaining w m r ( a d stme of the elm+ ?
trolytes) from undigested faod, thus m w m h g body wattr.