Digestive System
A. Processes – Ingestion (food in), Movement, Digestion (chemical and
mechanical), Absorption, Defecation
B. Types
1.
Chemical – breakdown of large carbohydrates, lipids and protein
into simple molecules
2.
Mechanical – chewing, muscular contraction
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ge?id=8039&rendTypeId=4
http://www.nlm.nih.gov/medline
plus/ency/images/ency/fullsize/1
9823.jpg
http://biology.clc.uc.edu/gra
phics/bio104/glucose1.jpg
C. Organization: Gastrointestinal Tract and Accessory Organs
1. GI Tract (Alimentary Canal) – mouth, pharynx, esophagus,
stomach, small intestine, large intestine
2. Accessory Organs – teeth, tongue, salivary glands, liver,
gall bladder, pancreas
http://visual.merriamwebster.com/images/hu
manbeing/anatomy/digestivesystem.jpg
D. Histology
1. mucosa – inner lining – mucous membrane
2. submucosa – areolar connective tissue binds mucosa
to muscle, contains blood and lymphatic tissue
3. muscularis – skeletal – mouth, pharynx, upper
esophagus, (swallowing) smooth muscle – the rest of the tract
4. serosa – outermost layer, serous fluid allows for free
gliding of the mesentery, omentum and falciform ligament
http://cache.eb.com/eb/image?id=74315&rendTypeId=4
E. Digestive Tract: Anatomy and Physiology
1.
Mouth – oral or buccal cavity
a. Tongue – skeletal muscle covered with mucous membrane
Extrinsic muscles – outside and insert in, move tongue side to
side and in and out
Intrinsic muscles – inside, speech and swallowing
b. Salivary glands - 3 pairs – parotid, submandibular,
sublingual
Saliva – 99.5% H2O, .5% solutes – lubrication and
dissolving, Salivary Amylase under nervous control
http://academic.kellogg.cc.mi.us/herbran
dsonc/bio201_McKinley/f264a_salivary_glands_c.jpg
c. Teeth – located in bony sockets of maxilla and mandible - KNOW
TYPES AND FUNCTIONS
http://www.medem.com/MEDEM
/images/AMA/ama_preventive_o
ralhealth_lev20_theteeth_01.jpg
http://whyfiles.org/shorties/1
47tooth/images/teeth.jpg
http://dentistsplans.com/images/health
ytooth.jpg
d. Digestion in the mouth
Mechanical – Mastication (chewing)
Chemical – Salivary Amylase – starts breakdown of starch
2. Esophagus – lies behind the trachea
a.
Function – transports food
b.
Peristalsis – muscular movements (involuntary) to push food
through esophagus
c.
lower esophageal sphincter – prevents backflow of HCl
(heartburn)
http://www.massgeneral.org/cancer/c
rr/types/thoracic/illustrations/images/
esophagus_front.jpg
3. Stomach – J-shaped
a.
Anatomy – cardia – superior opening
Fundus – up and to the left
Body – large central portion
Pyloris – narrow, inferior region
b.
Digestion
MECHANICAL – mixing waves =
Peristaltic movements every
15-20 seconds, forms chyme
CHEMICAL – Pepsin digests
proteins, effective at pH of 2
http://www.nlm.nih.gov/medlineplus/en
cy/images/ency/fullsize/19223.jpg
Gastric Lipase breaks down large lipids (triglycerides)
Controlled by nervous and hormonal mechanisms
c. Regulation of gastric emptying – Stomach empties all of contents into
duodenum within 2-6 hours
Carbohydrates spend less time in stomach, proteins more
Vomiting – forceful expulsion of contents from upper GI tract
4. Pancreas – behind stomach, secrete into duodenum through pancreatic
duct
a.
Anatomy – Islets of Langerhans and Acini cells, 2 types of cells
b.
Pancreatic juices
EXOCRINE
ENDOCRINE
Acini cells
Islets of Langerhans
Produce mixture of digestive
Glucagon (converts
enzymes = pancreatic enzymes
glycogen to glucose)
Multiple enzymes for digestion
Insulin (transports
of carbs, protein, fat
glucose into cells and
Regulated by nervous system
changes glucose into
and hormones
glycogen
http://www.nlm.nih.gov/medlineplus/ency/
images/ency/fullsize/17194.jpg
http://www.nlm.nih.gov/medlineplus/ency
/images/ency/fullsize/17151.jpg
5. Liver – heaviest gland, supported by falciform ligament
a. Functions:
Lobules consist of hepatic cells
which produce bile
Destroys worn out white and red
blood cells, bacteria and other
toxins
http://www.best-vitamin-supplementsguide.com/images/liver.jpg
b. Bile – yellow, brownish or olive
green, pH of 7.6-8.6, aids in
emulsification, conversion of fat
into droplets, helps in absorption
of fat
6. Gall bladder – concentrates
and stores bile until needed by
small intestine
http://www.nlm.nih.gov/medlineplu
s/ency/images/ency/fullsize/1090.j
pg
7. Small intestine – most digestion and absorption (90%) occurs here
a. Anatomy – 21 ft long in cadaver, 10 ft long in living (muscle tone)
Made up of duodenum, jejunum, ileum
b. Adaptations - length, mucosa
and submucosa are modified to
increase digestion and absorption,
villi and microvilli increase surface
area, circular folds
http://www.cudahychamber.com/images
/digestive_system.gif
http://instruct1.cit.cornell.edu/courses/biog105/page
s/demos/105/unit6/media/villus.structure.jpg
c. Digestion and absorption of major nutrients
CARBOHYDRATES – maltase, sucrase and lactase break
disaccharides into monosaccharides, absorbed as such
PROTEINS – pepsin fragments proteins into peptides,
Peptidase completes the task, absorbed as amino acids
LIPIDS – occurs in small intestineby pancreatic lipase,
absorbed as monoglycerides and fatty acids
NUCLEIC ACIDS – done by intestinal and pancreatic
juices
http://images.google.com/i
mages?hl=en&rlz=1T4DMUS
_enUS207US207&resnum=0
&q=nucleic%20acids&um=1
&ie=UTF-8&sa=N&tab=wi
http://images.foodnetwork.com/webfood/ima
ges/gethealthy/nutritionalallstars/LeanProtei
ns_header.jpg
8. Large Intestine – completion of
absorption, makes vitamins, forms
feces
a. Anatomy – 5 feet long, 2.5 in in
diameter, ileocecal sphincter,
appendix, ascending, transverse,
descending and sigmoid colon
b. Digestion, absorption, and feces
formation – MECHANICAL –
following meal chyme is forced into
cecum, food intiates mass
peristalsis – drives colon contents
into the rectum – 3 or 4 times daily
9. Disorders of the digestive system
http://immunesupportonline.co
m/Images/Digestive%20Syste
m%20Anatomy_files/Digestive
%20tract%20annotated.jpg
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umb/c/c5/Digestive_system_diagram_en.svg/300px
-Digestive_system_diagram_en.svg.png