2. THE DIGESTIVE SYSTEM IS A COMPLEX SET OF ORGANS, GLANDS, AND DUCTS
THAT WORK TOGETHER TO TRANSFORM FOOD INTO NUTRIENTS FOR CELLS.
FOOD IS TAKEN INTO THE DIGESTIVE SYSTEM, WHERE IT IS BROKEN DOWN
INTO SMALLER AND SMALLER PARTICLES.
ENZYMES BREAK THE PARTICLES DOWN INTO SMALL MOLECULES, WHICH ARE
ABSORBED INTO THE BLOOD AND TRANSPORTED ALL OVER THE BODY.
FUNCTIONS OF THE DIGESTIVE SYSTEM
JERIC
3. 01
02
03
04
05
INGESTION AND MASTICATION – INGESTION IS THE CONSUMPTION OF SOLID OR LIQUID FOOD.
MASTICATION IS CHEWING.
PROPULSION AND MIXING - PROPULSION IS THE MOVEMENT OF FOOD FROM ONE END OF THE DIGESTIVE
TRACT TO THE OTHER. MIXING IS THE MOVEMENT OF FOOD BACK AND FORTH IN THE DIGESTIVE TRACT TO
MIX IT WITH ENZYMES AND FACILITATE ABSORPTION.
DIGESTION AND SECRETION - DIGESTION IS THE MECHANICAL AND CHEMICAL BREAKDOWN OF LARGE
MOLECULES INTO SMALLER MOLECULES THAT CAN BE ABSORBED. SECRETION IS THE ADDITION OF LIQUIDS,
ENZYMES, AND MUCUS TO THE INGESTED FOOD.
ABSORPTION - THE MOVEMENT OF MOLECULES OUT OF THE DIGESTIVE TRACT AND INTO THE BLOOD OR
LYMPHATIC SYSTEM.
ELIMINATION - ELIMINATION IS THE REMOVAL OF UNDIGESTED MATERIAL, SUCH AS FIBER FROM FOOD,
PLUS OTHER WASTE PRODUCTS FROM THE BODY AS FECES.
CONTINUATION
4. ANATOMY OF THE
DIGESTIVE SYSTEM
·The digestive system consists of
the digestive tract, plus specific
associated organs.
·The digestive tract is also
referred to as the GIT
(gastrointestinal tract)
The tract is one long tube from
the mouth to the anus.
The digestive tract consists of the:
· oral cavity (mouth)
· pharynx
· esophagus
· stomach
· small intestines
· large intestines
· anus
5. The layers of the tract wall are also termed tunics.
1. Mucosa:
o innermost layer
o secretes mucus
2. Submucosa:
o above mucosa
o contains blood vessels, nerves, small glands
3. Muscularis:
o above submucosa
o longitudinal, circular, and oblique muscles
4. Serosa/adventitia:
o outermost layer
o If peritoneum is present called serosa
o If no peritoneum then called adventitia
LAYERS OF DIGESTIVE TRACT WALL
7. Lips - muscular structures, formed
by the orbicularis oris muscle and
covered by skin.
Cheeks - lateral walls of the oral
cavity, within the cheeks are the
buccinator muscles which flatten
the cheeks against the teeth.
Tongue - large, muscular organ
that occupies most of the oral
cavity.
The tongue moves food in the mouth
and, in cooperation with the lips
and cheeks, holds the food in
place during mastication.
ORAL CAVITY
8. 32 teeth in normal adult
Incisors, canine, premolars, molars, wisdom
Each tooth has crown, cusp, neck, root
The bulk of the tooth is formed by a cellular tissue called dentin
In the crown of the tooth, the dentin is covered by an extremely hard,
acellular enamel
· 20 primary (deciduous) teeth
Produce saliva which is a mixture of serous (watery) and mucous fluids
· Dissolves food particles so they can be tasted
· Protects against bacteria and neutralizes pH
· Begins the process of digestion
Serous portion of saliva contains enzymes
· Amylase - Digestive enzyme that breaks down carbohydrates
· Lysozyme - Enzymes that are active against bacteria
Mucous portion contains mucin for lubrication
TEETH
SALIVARY GLANDS JERIC
KREDENCE
9. nasopharynx
oropharynx
laryngopharynx
Connects the mouth to the esophagus
It has three parts:
PHARYX
THROAT
ESOPHAGUS
Tube that connects the pharynx to
the stomach
Transports food to the stomach
Joins stomach at cardiac opening
10. occurs when gastric juices regurgitate into esophagus
caused by caffeine, smoking, or eating or drinking in excess
HEART BURN
Voluntary phase:
· bolus (mass of food) formed in mouth and pushed into oropharynx
Pharyngeal phase:
· swallowing reflex initiated when bolus stimulates receptors in
oropharynx
Esophageal phase:
· moves food from pharynx to stomach
SWALLOWING
11. wave-like contractions move food through digestive tract
PERISTALSIS:
Located in abdomen
Storage tank for food
Can hold up to 2 liters of food
Produces mucus, hydrochloric acid, protein digesting enzymes
Contains a thick mucus layer that lubricates and protects
epithelial cells on stomach wall from acidic pH (3)
STOMACH
12. SECRETIONS OF THE STOMACH
Hydrochloric acid- Kills microorganisms, activates pepsin.
Pepsin- breaks covalent bonds of proteins to form smaller peptide chains
Mucus- A thick layer,which lubricates the mucosa of the stomach
· Protects mucosa from acidic chyme and pepsin
Intrinsic factor- Binds with vitamin B12 making it more readily absorbed by
small intestine and Vitamin B12 is important in DNA synthesis and red blood
cell production
14. Measures 6 meters in length
Major absorptive organ of the gastrointestinal tract
Chyme takes 3 to 5 hours to pass through
Contains enzymes to further breakdown food
Contains secretions for protection against the acidity of chyme
BILE
SMALL INTESTINE
LIVER
·Tube that connects the pharynx to the stomach
Transports food to the stomach
Joins stomach at cardiac opening
dilutes and neutralizes stomach acid and breaks down fats
15. A glandular organ located in the abdomen.
It makes pancreatic juices, which contain enzymes that aid in digestion,
and it produces several hormones, including insulin.
The pancreas is surrounded by the stomach, intestines, and other organs.
APPENDIX
PANCREAS
LARGE INTESTINE
The large intestine is the terminal segment of the human
gastrointestinal (GI) tract, which is a continuous
Tube-like channel via which food passes along the human digestive
system.
It runs from the small intestine to the anal canal, wherein food waste
is eliminated.
In simpler terms, the large intestine is involved in faeces production.
9 cm structure that is often removed
KREDENCE
MARY
16. · joins small intestine at ileocecal junction
· has appendix attached
RECTUM
CECUM
COLON
1.5 meters long
contains ascending, transverse, descending, sigmoid regions
· straight tube that begins at sigmoid colon and ends at anal canal
ANAL CANAL
last 2 to 3 cm of digestive tract
Food takes 18 to 24 hours to pass through large intestine
Feces are product of water, indigestible food, and microbes
Microbes synthesize vitamin K.
17. Polysaccharides split into disaccharides by salivary and pancreatic amylases
Disaccharides are broken down into monosaccharides by disaccharidases on the
surface of intestinal epithelium
Glucose is absorbed by cotransport with Na+ into the intestinal epithelium
Glucose is carried by the hepatic portal vein to the liver and enters most cells
by facilitated diffusion
CARBOHYDRATE DIGESTION
MARY
Lipase breaks down triglycerides into fatty acids and monoglycerides.
Bile salts surround fatty acids and monoglycerides to form micelles.
Micelles attach to the plasma membranes of intestinal epithelial cells, and the
fatty acids and monoglycerides pass by simple diffusion into the intestinal
epithelial cells
Within the intestinal epithelial cell, the fatty acids and monoglycerides are
converted to triglycerides.
Proteins coat the triglycerides to form chylomicrons, which move out of the
intestinal epithelial cells by exocytosis.
The chylomicrons enter the lacteals of the intestinal villi and are carried
through the lymphatic system to the blood.
18. Lipids are packaged into lipoproteins to allow transport in the lymph and blood.
Lipoproteins are molecules that are part water soluble and part lipid soluble.
Since lymph and blood contain water and lipids are not water soluble, lipoproteins
are necessary for transport.
Lipoproteins include chylomicrons, low-density lipoproteins (LDL), and high-density
lipoproteins (HDL).
Pepsin is a protein-digesting enzyme secreted by the stomach.
The pancreas secretes the protein digesting enzymes trypsin, chymotrypsin, and
carboxypeptidase into the small intestine in an inactive state.
In the small intestine, other enzymes termed peptidases, bound to the
microvilli of the intestinal epithelium further break down small peptides into
tripeptides.
Absorption of tripeptides, dipeptides, or individual amino acids occurs through
the intestinal epithelial cells by various cotransport mechanisms.
· In the small intestines these enzymes are activated
LIPOPROTEINS
PROTEIN DIGESTION
19. WATER AND MINERALS
Water can move across the
intestinal wall in either
direction
The movement depends on osmotic
pressures
99% of water entering intestine
is absorbed
Minerals are actively
transported across wall of
small intestin
FLUID VOLUMES IN THE
DIGESTIVE TRACT
