A&p Ii: Chapter 23

Front 1

OVERVIEW OF DIGESTIVE SYSTEM

Back 1

A. DIGESTIVE TRACT = ALIMENTARY CANAL = GASTROINTESTINAL (GI) TRACT
1. 9 M. long: Mouth -> Anus
2. Continuous tube: technically outside body

B. ACCESSORY ORGANS TO THE GI TRACT
Mouth: Teeth, Tongue

C. ACCESSORY GLANDS ATTACHED BY DUCTS TO GI TRACT
Salivary Glands, liver, pancreas, gall bladder

Front 2

6 ESSENTIAL ACTIVITIES OF DIGESTIVE TRACT

Back 2

A. INGESTION: intake (mouth)

B. PROPULSION: movement thru tract (mouth thru anal canal)

1. SWALLOWING = DEGLUTITION (mouth, pharynx)
2. PERISTALSIS: alternate waves of contraction & relaxation of muscles of organ walls
a. squeezing movement in one direction
b. Pharynx -> anal canal

C. MECHANICAL DIGESTION: MACERATION
1. MASTICATION: chewing * BOLUS formation: mixing saliva with food
2. CHURNING: stomach
3. SEGMENTATION: non-propulsive intestinal rhythmic contractions in sm./lg. Intest.

Front 3

6 ESSENTIAL ACTIVITIES OF DIGESTIVE TRACT 2

Back 3

D. CHEMICAL DIGESTION (mouth through small intestine)
1. mouth -> small intestine (little in Lg intestine)
2. CATABOLISM: food HYDROLYZED into basic units (simple sugars, amino acids,
fatty acids, monoglycerides) for absorption
ie: starch + water ------> monosaccharides (HYDROLYSIS) with enzyme help

E. ABSORPTION: nutrients mainly in small intestine (minor in mouth and stomach, water and
vitamins only in large intestine)
1. vitamins, minerals, water, basic food units pass thru GI tract wall into blood & lymph
2. movement via passive and active transport

F. DEFECATION: elimination of indigestible substances from LI via anus as FECAL material
(rectum and anal canal)

Front 4

GENERAL HISTOLOGY OF THE ALIMENTARY TRACT WALL

Back 4

*similar for most regions of the tract from esophagus->anus
*4 basic TUNICS (layers) of the GI tract surround a LUMEN

A. MUCOSA: next to the lumen = mucous membrane
mucus secreting epithelium, CNT and smooth muscle, glands

B. SUBMUCOSA: supports, nourishes, absorbs: made of loose cnt, bv, nerves, glands

C. MUSCULARIS EXTERNA: smooth muscle
1. CIRCULAR layer, inner -> SPHINCTERS (valves)
2. LONGITUDINAL layer, outer -> segmentation, peristalsis

D. SEROSA/ ADVENTITIA: furthest from the lumen
1. serosa= visceral peritoneum for organs in peritoneal cavity
2. adventitia = visceral covering esophagus
3. retroperitoneal organs: have part serosa, part adventitia

Front 5

MOUTH = ORAL CAVITY = BUCCAL CAVITY

Back 5

*lined with stratified squamous epithelium - protection

1. LIPS = LABIA, & CHEEKS: skin and muscle
a. ORBICULARIS ORIS M.
b. BUCCINATOR M.
c. ORAL CAVITY PROPER: inside teeth
d. LABIAL FRENULUM: fold attaching lips to gum
e. VESTIBULE: between lips and gums

Front 6

PALATE

Back 6

separates oral and nasal cavities
a. HARD: anterior portion (maxilla, palatine bones)
b. SOFT: posterior portion (skeletal m. and mucosa)
1) UVULA: closes off passage to nose during swallowing
2) PALATOGLOSSAL ARCHES: soft palate to tongue
3) PALATOPHARYNGEAL ARCHES: soft palate- oropharynx
4) FAUCES: space between the two arches, contain palatine tonsils

Front 7

TONGUE

Back 7

bolus formation, speech, swallowing (skeletal m.), taste
a. ROOT: attaches tongue to HYOID bone
b. LINGUAL FRENULUM: ant. tongue to floor of mouth
c. PAPILLAE: bumps on tongue house taste buds
d. LINGUAL TONSIL: post 1/3 of tongue

Front 8

SALIVARY GLANDS

Back 8

3 pair lg exocrine glands outside oral cavity, activated by:
sight, smell, thought of food, food in mouth, upset stomach, PSNS

a. PAROTIDS: anterior to ear. largest ones: ducts enter near UM2
mumps=viral infection 25% sterility

b. SUBMANDIBULARS: floor of mouth near mandible *ducts enter on sides of
lingual frenulum

c. SUBLINGULALS: mouth floor ant. to submandib.
*many small ducts along lingual frenulum
* SALIVA
1)water, metabolic waste, mucus
2)AMYLASE: breaks down starches -> monosacs
3)LYSOZYME, IMMUNOGLOBULINS: help w immunity
4)GROWTH FACTOR: healing properties

Front 9

TEETH

Back 9

mastication
a. TOOTH STRUCTURE
1) CROWN: visible part covered w ENAMEL, located above the
GINGIVA (gum)

2) ROOT: embedded in ALVEOLI (sockets) in mandible and maxilla.
covered with CEMENTUM

3) NECK: where root meets crown

b. TOOTH COVERINGS:
1) enamel: hard, outer calcified crown covering 2) cementum: calcified outer root covering
3) periodontal ligament: attaches cementum to alveolus forming a joint
4) dentin: Ca-rich, bone-like material under enamel & cementum
5) pulp: bv, nerves in PULP CAVITY of crown and in ROOT CANALS
a) ROOT CANAL: space in center of root
b) APICAL FORAMEN: holes at base of each root

Front 10

TEETH 2

Back 10

c. types of teeth (front to back of mouth)
1) INCISORS: chisel shaped, cut (one root)
2) CANINES (cuspids, "EYE" teeth) conical, tear (one root)
3) PREMOLARS (BICUSPIDS): broad crown, grind (one root)
4) MOLARS: broad crown, grind, crush (top:3-4 roots, lower:2-3 roots)

d. PRIMARY DENTITION = DECIDUOUS TEETH (baby, milk)
1) erupt between 6 mo -> 2.5 yr
2) 20 teeth 8 incisors, 4 canines, 8 molars
3) begin to fall out at 6 yr.

e. PERMANENT DENTITION = SECONDARY TEETH
1) erupt between 6 yr -> 25 yr
2) 32 teeth (including wisdom teeth)
8 incisors, 4 canines, 8 premolars, 12 molars

Front 11

FUNCTIONS OF THE MOUTH

Back 11

a. ingestion
b. chemical digestion of starches (salivary amylase)
c. mechanical digestion - mastication
d. swallowing (deglutition)

Front 12

PHARYNX: THROAT (RESPIRATORY AND DIGESTIVE CROSSROADS

Back 12

*lined with stratified squamous epithelium. Involved in swallowing and peristalsis.
1. OROPHARYNX: posterior to the oral cavity
2. LARYNGOPHARYNX: inferior to the oropharynx
3. NASOPHARYNX: superior to the oropharynx, part of respiratory system.

Front 13

ESOPHAGUS

Back 13

10" long from pharynx to stomach *lined with stratified squamous
epithelium for protection. Involved in peristalsis.
1. CARDIAC ORIFICE: esophagus joins stomach
2. CARDIAC (GASTROESOPHAGEAL) SPHINCTER: valve
3. HEARTBURN: pain of stomach acid entering esophagus

Front 14

STOMACH

Back 14

holds up to 4L (1Gal) food when full, extending into pelvis!

1. FOUR REGIONS OF STOMACH
a. CARDIAC REGION: around opening of esophagus
b. FUNDUS: superiormost part of stomach
c. BODY: main region inferior to cardia and fundus
1)GREATER CURVATURE: convex, inferior curve
a)GREATER OMENTUM: mesentery stomach to int.
2)LESSER CURVATURE: concave, superior curve
b)LESSER OMENTUM: mesentery stomach to liver
d. PYLORIC REGION: tapering end of stomach
1)PYLORIC SPHINCTER: valve to DUODENUM

Front 15

VARIATIONS IN THE TUNICS OF THE STOMACH WALL

Back 15

a. MUSCULARIS EXTERNA has three layers of smooth m.
1. OBLIQUE: innermost
2. CIRCULAR: middle: thickened to form sphincters (pyloric, cardiac)
3. LONGITUDINAL: outermost
*when stomach is empty, these muscles contract & fold stomach lining into
longitudinal folds=RUGAE

b. MUCOSAL LINING OF STOMACH
1) simple columnar epithelium for protection
*lots of tight junctions to prevent gastric juices from digesting stomach

*made mostly of GOBLET CELLS that secrete mucus to protect
stomach wall

Front 16

VARIATIONS IN THE TUNICS OF THE STOMACH WALL 2

Back 16

2) GASTRIC GLANDS produce GASTRIC JUICE, open to stomach
lining via GASTRIC PITS. Juice =

a) alkaline mucus to protect stomach wall

b) HCl: kills bacteria, denatures prot., stimulates hormone release

c) INTRINSIC FACTOR: LIFE ESSENTIAL
-aids in absorption of VIT B12 for RBC production (no IF –
>PERNICIOUS ANEMIA)

d) PEPSINOGEN: inactive form of protease: PEPSIN. Activated
and functional at pH 2, prevents digestion of stomach wall

Gastric juice when mixed with bolus-> CHYME which has a fluid consistency

Front 17

VARIATIONS IN THE TUNICS OF THE STOMACH WALL 3

Back 17

ENTEROENDOCRINE CELLS: release hormones into blood stream
(not a part of gastric juice)
a) GASTRIN = hormone
fn: increase gastric gland secretion and gastric motility
target: gastric glands, stomach muscles
control: stomach acidity (basic env. increases release),
PSNS, caffeine

Front 18

FUNCTIONS OF THE STOMACH

Back 18

a. MECHANICAL DIGESTION: CHURNING
-mixing waves stimulated by food in stomach
-macerates bolus into small bits
-mixes food with GASTRIC JUICE to form CHYME
b. PERISTALSIS: pushes chyme to pyloric sphincter
c. CHEMICAL DIGESTION OF PROTEINS - pepsin enzyme
d. ABSORPTION: water, aspirin, alcohol, electrolytes
e. SECRETION of gastric juice and hormones (gastrin)

Front 19

SMALL INTESTINE (SI)

Back 19

1. 6M long from pyloric sphincter to ileocecal sphincter
2. completion of chemical digestion here
3. Most absorption occurs here in first 2/3
4. passes remains onto large intestine
5. accessory organs: a. liver b. gall bladder c. pancreas
6. (3)regions of the SI: mostly suspended from dorsal abdominal wall via mesentery
a. DUODENUM: shortest segment, retroperitoneal
1) pyloric sphincter to jejunum: curves around pancreas
2) receives: chyme from stomach, secretions from liver, GB and pancreas
b. JEJUNUM: mid section (upper left quadrant), completion of most absorption
c. ILEUM: last segment (upper and lower right quadrants): empties into cecum
of lg. Intestine at ileocecal sphincter

Front 20

7. VARIATIONS IN SMALL INTESTINE WALL

Back 20

7. VARIATIONS IN SMALL INTESTINE WALL
a. MUCOSA
1) highly folded to increase surface area (SA) for absorption
a) PLICA CIRCULARES: circular folds ^SA, slow passage of
chyme (speed bumps)

b) VILLI: finger-like extensions of tissue into LUMEN, on top of
plica circulares
i. surrounds bv, lacteal for absorption
ii. PITS: found between villi lead to crypts of Lieberkuhn:
groups of int. glands secreting int. juice (1-2L/day, increase
secretion with increased chyme in duodenum - watery, alkaline
mucus with lysozyme from Paneth cells)

c) MICROVILLI: hair-like projections of each surface cell of the
villi = brush border
i. ^ SA
ii. brush border enzymes complete carbo, lipid, & prot. Dig.

Front 21

7. VARIATIONS IN SMALL INTESTINE WALL 2

Back 21

2) CELLS IN THE MUCOSA
a) SIMPLE COLUMNAR EPITHELIUM: produces brush border
enzymes (replaced every 3-6 days)
b) GOBLET: mucus
c) ENTEROENDOCRINE: secrete hormones:
i. CCK: decreases stomach motility, increases release of
digestive juices from pancreas, liver, gall bladder by
contraction of sm muscle

ii. SECRETIN: inhibits release of gastric juice & gastrin
stimulates release of bicarbonate from pancreas

d) PANETH CELLS: in CRYPTS OF LIEBERKUHN
secrete lysozyme break down bacteria

Front 22

SUBMUCOSA

Back 22

areolar cnt
1) PYER'S PATCHES: lymph nodules located in the ILEUM
2) BRUNNER'S GLANDS: secrete neutralizing fluid to ^ pH of chyme.
Found in Duodenum.

Front 23

FUNCTIONS OF THE SI

Back 23

a. mechanical digestion: SEGMENTATION
b. propulsion: PERISTALSIS
c. completion of chemical digestion: of carbohydrates, protein, fats by brush
border enzymes with help from pancreatic juice and bile
d. ABSORPTION (occurs w/ aid of digestive juices from liver, GB & pancreas)
1) mainly thru villus mucosa to submucosa -> blood cap. -> hep. portal v.
a) monosaccharides
b) amino acids
c) fats are EMULSIFIED (separated) by BILE SALTS =>
MICELLES and the short chained fatty acids may be absorbed

2) some absorption occurs into lymphatic system
a) long FA's and monoglycerides + bile salts -> MICELLES: little
fat droplets
b) MICELLES are absorbed into villi
c) bile salts separate-> recycled to liver
d) fat + phospholipids + protein -> CHYLOMICRON
e) chylomicrons enter lacteal of lymph system
f) lymph dumps into blood in L. subclavian v. near heart
g) when blood gets to liver, fats are filtered & stored in adipose

Front 24

LIVER

Back 24

: in upper rt quadrant of abdomen. largest GLAND

1. ANATOMY:
a. FOUR LOBES:
1&2) L and R. separated by the FALCIFORM LIG.

3) QUADRATE LOBE (anterior, inferior)
-between gall bladder and round ligament (ligamentum teres)
-round ligament runs to umbilicus

4) CAUDATE LOBE (posterior, inferior)
-between inf. vena cava & lesser omentum fissure (lig. Venosum)

b. GALL BLADDER: organ located on the inferior side of right lobe of liver

Front 25

LIVER 2

Back 25

BLOOD SUPPLY TO LIVER
a. BLOOD ENTERING LIVER
1) HEPATIC A. oxygenated blood from heart (comes off aorta)
2) HEPATIC PORTAL V. nutrient rich blood from digestive tract
b. BLOOD EXITING LIVER: CENTRAL VEINS->larger vv. ->HEPATIC V.
dumps into ->INF. VENA CAVA-> HEART

Front 26

LIVER 3

Back 26

. MICROSCOPIC ANATOMY:
a. LOBULES: functional unit of the liver, hexagonal
1) CENTRAL VEIN: in center of each lobule.
2) HEPATOCYTES: liver cells in plates that radiate out from central v.
3) PORTAL TRIAD: at each corner of the lobule contains: branch of
hepatic a., branch of hepatic portal v. and bile duct
4) BILE CANALICULI: small channels between hepatocytes, carry bile


5) SINUSOIDS: blood entering liver is filtered thru these blood channels
between hepatocytes LINED WITH KUPFFER CELLS (filter out
foreign matter, dead RBC's & toxins). Sinusoids dump into central v.

* blood leaving liver is cleaner & clear of nutrients due to actions of Kupffer &
hepatocyte cells

Front 27

LIVER 4

Back 27

4. HEPATOCYTE FUNCTIONS
a. remove O2, nutrients, wastes & toxins
b. stores: GLYCOGEN, Fe, Cu, VIT A, B12, D, E, K, TG
c. activates VIT D (for Ca absorption)
d. catabolizes: fatty acids
e. anabolizes: cholesterol, lipoprotiens, phospholipids and fats, plasma proteins,
new amino acids from old amino acids, ammonia (converted into urea),
glucose, glycogen, bile and bile salts

Front 28

LIVER 5

Back 28

5. BILE
a. produce 1L/day by liver, stored in GALL BLADDER
b. yellow-green, alkaline, neutralizes chyme, aids fat digestion
c. water, bile salts, bile pigments, cholesterol, fats, electrolytes & phospholipids
(2 with dig. fns)
d. BILE SALTS: help EMULSIFY fats: break into small droplets so that fats can
be absorbed
e. BILE PIGMENTS: from breakdown of hemoglobin. Waste product that gives
color to urine, feces BILIRUBIN = primary bile pigment
f. production stimulated by:
1) SECRETIN from intestine - neutralize chyme
2) increased blood to liver
3) increase in bile salts in blood
4) increased fat in chyme

Front 29

GALL BLADDER

Back 29

1. 7-10 cm pear-shaped, green bag
2. concentrates and stores bile produced by liver
3. liver produces bile, flowing thru the bile canaliculi to larger bile ducts-->
r & l hepatic ducts (drain each lobe)--> common hepatic duct
(drains liver)-> (common) bile duct (drains liver & gb)->joins up with
secretions from pancreas at the ampulla of Vater (hepatopancreatic
ampulla) -> sphincter of Oddi (hepatopancreatic sphincter) regulates
flow of fluids from liver & pancreas through the major duodenal papilla
4. if sphincter of Oddi is closed, bile backs up into the common bile duct, then back
into the cystic duct which leads to the gall bladder

5. CCK stimulates contraction of the GB and relaxation of the SPHINCTER of ODDI
releasing bile into the duodenum

6. gall stones (bilary calculi): cholesterol crystals w/sharp edges can block cystic duct

Front 30

PANCREAS

Back 30

posterior/inferior to stomach
1. HEAD -near beginning of duodenum
2. TAIL - near spleen
3. MAIN PANCREATIC DUCT: runs length of panc. joins common bile duct at
hepatopancreatic ampulla. Regulated by the main pancreatic sphincter.
4. ACCESSORY PANCREATIC DUCT: short, dumps into duodenum
5. HORMONE PRODUCTION: endocrine gland
* ISLETS OF LANGERHANS
a. cell clusters scattered thru pancreas
b. secrete many things including: INSULIN and GLUCAGON

Front 31

PANCREAS 2

Back 31

6. PANCREATIC JUICE PRODUCTION: exocrine gland (dig. fn)
* ACINAR CELLS: produce juice 1.5 L/day

a. PANCREATIC JUICE contains
1)water
2)bicarbonate pH = 8 (neutralize chyme)
3)inactive precursors to enzymes aiding in protein digestion. Precursors
activated in SI to prevent digestion of the pancreas. In SI precursors are
converted into: trypsin, chymotrypsin, carboxypeptidase
4)active digestive enzymes:
a)PANCREATIC AMYLASE: active starch/carbo breakdown
aided by ions in BILE
b)PANCREATIC LIPASE: active fatty acid break down aided by
BILE SALTS

Front 32

LARGE INTESTINE (COLON

Back 32

1. ANATOMY (GROSS)
a. cont. with ileum of SI at ILEOCECAL SPHINCTER
b. CECUM blind downward projection of LI at ileocecal sphincter.
* VERMIFORM APPENDIX: Immune fns. attached to cecum
c. ASCENDING, TRANSVERSE, DESCENDING, SIGMOID COLON
d. RECTUM and ANAL CANAL
e. ANUS with
1) INTERNAL ANAL SPHINCTER: thickening of circular layer of
muscularis externa
2) EXTERNAL ANAL SPHINCTER: ring of skeletal m. surrounds anus.
Voluntary control over defecation
f. EPIPLOIC APPENDAGES: fat filled pouches on LI

Front 33

VARIATIONS IN THE WALL OF THE LARGE INTESTINE

Back 33

a. MUCOSA

1) no villi, no circular folds as in SI

2) lots of GOBLET cells in simple columnar epith. designed for water
absorption, easing of feces

b. MUSCULARIS EXTERNA: incomplete longitudinal m. layer

1) TAENIAE COLI = 3 bands of longitudinal fibers

2) HAUSTRA = pouches in LI wall due to contraction of taeniae coli

Front 34

MOVEMENTS OF LI

Back 34

a. HAUSTRAL CHURNING: haustra fill, contract & slowly push contents to
next pouch

b. MASS PERISTALSIS: during and after eating

c. GASTROCOLIC REFLEX ("eat and go" reflex): food in stomach -> mass
peristalsis in mid transverse colon -> contents pushed to rectum -> defecation

Front 35

BACTERIAL DIGESTION OF UNABSORBED CHYME IN LI

Back 35

a. BACTERIA IN LUMEN: from diet and anus
1) ferment remaining carbohydrates (flatulus)
2) breakdown remaining proteins -> aa -> products give feces odor
3) breakdown bilirubin from bile -> products give feces brown color
4) production of vit b and vit k

b. ABSORPTION
1) Vit B, K produced by bacteria in LI
2) WATER needed to maintain fluid balance
-longer feces in LI more water absorbed

c. FECES PRODUCTION
1) after 3-10hr of chyme in LI => feces
2) contains: water, bacterial waste, salts,undigested food, dead cells,
bacteria
3) DIARRHEA: feces not in LI for long, little absorption

Front 36

DEFECATION

Back 36

b. STRETCH OF RECTAL WALL sends reflex signal to descending colon,
rectum, and anus to increase contraction to expel feces

c. VALSALVA'S MANEUVER: voluntary contraction of abdominal muscle,
diaphragm, holding of breath used to help empty rectum, bladder

d. PARASYMPATHETIC STIMULUS: relaxes internal anal sphincter

e. voluntary relaxation of external sphincter of anus necessary

Front 37

Functions of Large Intestine: summary

Back 37

a. propulsion: haustral churning, mass peristalsis

b. absorption: vit K and B from bacteria, water

c. feces production

d. defecation