DIGESTIVE SYSTEM
I. DIGESTION
A. Breakdown of food particles into molecules small enough to be used by body cells.
1. Organs involved == GI tract – gastrointestinal tract
2. Absorption:passage of these molecules into blood & lymph
B. Figure 17.1
1. Organs of digestion: gastrointestinal tract (GI) tract=alimentary canal –tube from mouth to anus;
2. Accessory structures: teeth, tongue, salivary glands, liver, gallbladder, & pancreas
3. Gastroenterology: deals w struct., funct., diagnosis & treatment of diseases of stomach & intestines
4. Proctology: medical specialty dealing with diagnosis & treatment of disorders of rectum & anus
C. 5 activities of dig. system that prepare food for use by body cells:
1. Ingestion
2. Secretion
3. Mixing & movement
4. Digestion
5. Absorption
II. ANATOMY: Figure 17.2
A. ALIMENTARY CANAL – ______________________________
1. Muscular tube – 9 meters long – 30 feet from mouth to anus – _____________________________
2. Long in the cadaver, shorter in living person (muscle tone)
a. Includes mouth, pharynx, esophagus, stomach, small intestine, large intestine
B. ACCESSORY STRUCTURES:
1. Teeth, tongue, salivary glands, liver, gallbladder, pancreas
2. All but _________________________________________ lie outside tract & produce or store
secretions
C. WALL OF TRACT : 4 COATS OR TUNICS: Figure 17.3
1. Basically the same from mouth to anus—minor differences
a. MUCOSA
b. SUBMUCOSA
c. MUSCULARIS
d. SEROSA
2. MUCOSA – ____________________________
a. A _____________________ membrane attached to thin layer of ______________________
b. Lining epithelium is in contact with contents
c. Smooth muscle - throws mucous membrane into folds & increases dig. & absorptive area
3. SUBMUCOSA
a. Loose ____________________________________ tissue; binds mucosa to muscular layer.
b. Functions
1). ______________________
2). ______________________
3). _______________________________ supply for secretions.
4. MUSCULARIS
a. Provides movement in tube
b. In mouth, pharynx, & upper 1/3 of esophagus layer is _________________________ muscle
c. In rest of tract muscularis = _____________________________________ muscle
1.) Two sheets –inner circular, outer longitudinal: these physically mix & propel the food.
d. MUSCULARIS contains the MAJOR NERVE SUPPLY to the alimentary tract
1.) ________________________________________________ (Plexus of Auerbach)
a.) Fibers from sympathethic & parasympathetic system for control of G I motility
5. SEROSA
a. Outermost layer
b. Protection
c. ____________________________________ of connective tissue & epithelium
1.) The serosa is the VISCERAL PERITONEUM
D. Peritoneum
1. Largest serous membrane of body
2. Contains folds that bind organs to each other & to walls of cavity
a. Contains __________________________________
E. EXTENSIONS OF PERITONEUM
1. Mesentary Fig. 17.33
2. Mesocolon Fig. 17.45
3. Falciform ligament
4. Lesser Omentum
5. Greater Omentum Fig. 17.36
F. Diagram the movements of the tube as it mixes & propels: check diagrams in your text in Figure 17.4
G. STRUCTURE OF MOUTH: Fig. 17.5
1. Cheeks, lips, vestibule, oral cavity, hard palate, soft palate, uvula, palatine tonsil, lingual tonsil,
fauces, tongue, lingual frenulum
2. Tongue Fig. 17.6
a._____________________________ made of both extrinsic muscles that insert on it & move it
b. Intrinsic muscles that originate & insert on it
3. __________________________________________________________
a. Fold of muscous membrane in midline of undersurface; holds tongue in place
b. Upper surface & side of tongue – covered with papillae
1.) _____________________________________________________ papillae
a.) Conical projections in parallel rows over anterior 2/3 of tongue—white, no taste buds
2.) _______________________________________________________ papillae
a.) Mushroom like, among filiform, many near tip; like red dots, contain taste buds
3.) ____________________________ ___________________________papillae
a.) 10-12, in form of inverted V on posterior surface; contains taste buds
4. Tonsils: FIGURE 17.7
a. __________________________________________________________________
1.) At root of tongue anchored to hyoid bone & covered with masses of lymphatic tissue
b. ______________________________________
1.) On either side of tongue, between folds of muscle in pharxynx
c.____________________________________________________________________ (adenoids)
1.) On posterior wall of nasopharynx above soft palate
H. TEETH: develop in sockets of mandible & maxilla; 2 sets during lifetime: FIGURE 17.9
1. Primary or ____________________________________ (to fall off) & secondary or permanent
a. Primary -1/month from 6 month to 2 ½ years == ________ total, 10/jaw
b. Names: central incisor, lateral incisor, cuspid (canine), first molar, second molar (last in order of
appearance)
2. Secondary or permanent – _________________ total, 16/jaw – 6 years to adult—
a. Primary ___________________________ replaced with 1st & 2nd premolars (bicuspids)
1). _________________________________ incisors – chisel shaped for cutting into food;
2). _____________________________ (canines)—pointed surface (cusp) to tear & shred
3).1st & 2nd molars -crush & grind –replaced by 1st & 2nd premolars
4). Permanent molars –do not replace deciduous teeth—erupt as jaw grows;
I. SALIVARY GLANDS FIGURE 17.11
1. Secret saliva that functions to:
a. Moisten food particles
b. Bind them together
c. Begin digestion of carbohydrates,
d. Dissolve food so chemicals can be tasted
e. Cleanse mouth & teeth
1.) Contains bicarbonate: buffers acids
2. TYPES OF SALIVARY GLANDS: FIGURE 17.12a, 17.12b, 17.12c
a. ____________________________________
1.) In mucosa of tongue, palate & cheeks
2.) Secrete constantly to lubricate
b. ______________________________________
1.) Largest
2.) Anterior & inferior to ears
3.) Between skin of cheek & masseter muscle;
a.) Duct—Stensen's Duct from gland through buccinator;
b.) Secretes AMYLASE FOR CARBOHYDRATE DIGESTION.
c. ____________________________________________________
1.) On floor of mouth on inside surface of mandible
2.) Serous cells, some mucous cells;
3.) Duct – Wharton's Duct—open under tongue
d. ________________________________________________
1.) Smallest—on floor of mouth under tongue
2.) Mucous cells secret thick mucus
J. Two types of secretory cells in salivary glands:
1. ______________________________________________________
a.) Watery fluid containing amylase—splits starch & glycogen into disaccharides
b.) Amylase continues to act on starches for 30 minutes more in fundus of stomach
2. _______________________ cells—secrete thick mucus
3. Nervous control of secretion from these
a.) Sympathetic stimulation—small amount of thick saliva
b.) Parasympathetic stimulation: large amt watery saliva - reflex when smell, taste, think, see food
K. PHARYNX & ESOPHAGUS: FIGURE 17.13
1. Pharynx—muscular passage –skeletal muscle, under involuntary reflex;
a. ___________________________ pharynx—above soft palate—eustachian tubes open here
b. ____________________________ pharynx –behind mouth—tube for food & air
c. ____________________________ pharynx—from upper border of epiglottis to lower border of
cricoid cartilage
d. Muscles of pharynx=superior, middle, inferior constrictors
1.) Some inferiors contract a little all the time; this prevents us from swallowing air
2. Esophagus Figure 17.15
a. Straight, _______________________________________ tube behind trachea
b. Through mediastinum
c. Penetrates diaphragm
d. Point of esophageal hiatus & is continuous with stomach. (hital hernia, heartburn)
3. ___________________________ --act of swallowing
a. Deglutition center --in __________________
b. Muscles of esophagus --upper 1/3 are skeletal, middle 1/3 skeletal & smooth, lower 1/3 --smooth
Fig. 17.16
c. Elevation of larynx in swallowing causes esophageal sphincter to relax.
d. List steps of deglutition Figure 17.14, 17.14b
4. Function of esophagus
a. Secretes _________________________
b. ___________________________(peristalsis); controlled by medulla;
c. Circular muscles contract & longitudinal muscles contract to shorten tube & relax portion below bolus
d.______________________________________________ (LA ZE A) --without relaxation
1.) Caused by malfunction of myenteric plexus
2.) Prevents normal relaxation of lower esophageal sphincter, impeding entrance of food into
stomach.
L. STOMACH FIGURE 17.17a, 17.17b
1. J shape, inferior to diaphragm; in upper left abdominal cavity; holds ONE LITER;
2. Inner lining of thick folds called _______________________________ (ruje) that increase surface
area.
3. Stomach functions to:
a. Mix food with gastric juice
b. Begin ________________________________________________ of proteins
c. _____________________________________________________ absorption
d. _______________________ food into small intestine
4.Muscles of stomach--inner circular, inner oblique (esp. near esophagus & in body), outer longitudinal
5. Parts of stomach
a. _____________________________________
b. _____________________________________ (note air in fundus; )
c. _____________________________________
d. ______________________________________
6. Adaptations:
a. Rugae --muscular folds;
b. Gastric glands --produce mucus, hydrochloric acid, pepsin (for protein digestion),
intrinsic factor (for B12 absorption), stomach gastrin, gastric lipase, rennin
7. WHAT does the stomach do? Fig. 17.19 and Table 17.5
a. Mixes --three layers of _______________________ Figure 17.22
b. Kills microbes & denatures protein--_________
c. Converts proteins into peptides by _________________ (enzyme that works well in -pH 2)
d. Secretes ___________________ -- protects stomach wall
e. Splits short chain triglycerides (molecules of butterfat in milk) gastric ______________________
f. Stimulates secretion of _______________________________________________ that promotes
flow of bile & pancreatic juice
g. Starch is dig. in fundus by amylase from mouth; butterfat is dig. by lingual lipase (under tongue)
h. Produces CHYME
M. Regulation of gastric secretion & motility:nervous & hormonal mechanisms FIGURE 17.21
1. THREE PHASES: cephalic (reflex), gastric, & intestinal
a. Cephalic & gastric phases -- stimulate peristalsis
b. Intestinal phase --------------- inhibits motility
2. Sight, smell, taste, thoughts of food stimulates submucosal plexus
a. _______________________________________________
3. Stretch receptors, chemoreceptors ( incr. in pH) stimulates submucosal plexus
a. __________________________
4. Distention of duodenum, fatty acid & glucose in duodenum
5. Food in small intestine stimulates the enterogastric reflex: Fig. 17.23 Result is INHIBITION
6. Stomach emptying:
a. Stimulated by distention of stomach; nerves & gastrin (hormone prod. in response to partially dig. protein & caffeine)
b. Food leaves ___________________- hours after ingestion:
1.) ____________________________________ 1st
2.) Then ________________________________
3.) Then ________________________________
4.) Inhibited by: enterogastric reflex, CCK & GIP (cholecystokinin & gastric inhibitory peptide)
N. PANCREAS Fig. 17.24 and Fig. 17.25
1.Connected to duodenum via pancreatic duct & accessory duct
2. Pancreatic islets secret __________________________
3. Pancreatic ____________________________________-- secretes fluids & digestive enzymes
known PANCREATIC JUICE
4. Pancreatic juice contains _______________________ that that digest starch, proteins, fats, & nucleic acids.
5. Contains sodium bicarbonate--makes chyme slightly alkaline; promotes enzyme activity; under
nervous & hormonal control.
O. LIVER Fig. 17.26 & 17.28
1.Left & right lobes separated by falciform ligament;
2. Liver receives a double supply of blood from hepatic _________________________ & hepatic portal ____________________________________;
3. All blood leaves liver via the hepatic vein
4. Produces bile
a. An excretory product (pig. from old RBC) & a digestive secretion
b. - BILE-- emulsifies triglycerides
5. Note functions of the liver in book **********************
P.- GALLBLADDER Fig. 17.32
1. Sac in visceral surface of liver; stores & conc. ________________;
2. Ejects bile into common bile duct via the cystic duct
3. Under influence of ______________________________________________
Q. SMALL INTESTINE Fig. 17.33, 17.37, 17.38, & 17.40
1. From pyloric sphincter to ileocecal sphincter
a. _______________________________________________________
2. Highly adapted for digestion & absorption; glands produce enzymes & mucus
3. Microvilli, villi & circular folds of its wall provide large __________________________________ for dig. & absorption
4. Intestinal juice --a vehicle for absorption from chyme as chemicals come in contact with villi
5. Digestion occurs in _______________________________________________ & on the surface of _________________________ of epithelial cells of villi
R. DIGESTION IN SMALL INTESTINE: segmentation & peristalsis Fig. 17.41, 17.42, & 17.43
1. Carbohydrates are broken down into _____________________________, fructose, & galactose
2. Proteins are broken down into peptides _______________________________________
3. Triglycerides are broken down into _______________________________ & monoglycerides
4. Nucleotides are broken down into pentoses & __________________________ bases
S. - REGULATION OF INTESTINAL SECRETION
- HORMONES & MOTILITY
1. Local reflexes in response to _____________________
2. - Hormone--vasoactive intestinal polypeptide ==VIP--stim. prod. of __________________________
3. Parasympathetic impulses ______ motility; sympathetic impulses ___________ motility
T. ABSORPTION: 90% occurs in small intestine Table 17.10
1.___________________saccharides
2. ___________________ acids
3. ___________________________ acids pass into blood capillaries
4. Long-chain fatty acids & monoglycerides Fig. 17.44
a. Absorbed as part of _____________________________________, resynthesized to
___________________________
b. Formed into protein-coated spherical masses = CHYLOMICRONS.
c. CHYLOMICRONS are taken up by the ____________________ of a villusà
lymphatic
systemà
heart-à
adipose tissue or liver.
5. Water, electrolytes, & vitamins
6. Plasma lipids (fatty acids, triglycerides, & cholesterol) are insoluble in water: in order to be transported in blood they must combine with protein: lipid + protein transporter (apoprotein)
===LIPOPROTEIN
a. Types of lipoproteins: REFER TO LIPOPROTEIN HANDOUT
1.) Chylomicrons
2.) High-density lipoproteins (healthy lipoprotein) HDL;
3.) Low-density lipoproteins (lowly) VLDL;
4.) VLDL
U. LARGE INTESTINE: Fig 17.45
1. Extends from ileocecal sphincter to ___________________;
2. Includes cecum, colon, rectum, & anal canal
3. Mucosa has no villi or permanent circular folds; simple ________________________ epithelium with goblet cells;
4. Locate taeniae coli & haustra
V. PHYSIOLOGY OF DIGESTION IN LARGE INTESTINE Try this too!!
1. Mechanical movements --______________________________________________________
a.Churning
b. Peristalsis
c. Mass peristalsis
2. Last stages of chemical digestion occur via ___________________________________ ; vitamins
produced; absorbed
3. Water absorbed; electrolytes absorbed
W. FECES:water, inorganic salts, sloughed-off epithelial cells, bacteria, products of bacterial
decomposition, undigested food
X. DISORDERS: