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Transcript of The Digestive System - Leyden...
The Digestive System
Chapter 19
Purpose of Digestive System
Humans are heterotrophic
Hetero = other
Trophic = to feed
Cellular materials are needed for metabolism, growth, and repair of cells
Body accomplishes this by taking in food particles and breaking them down for cell functions
Functions of the Digestive System
Digestion: breakdown of food particles into nutrient components
Absorption: transfer of nutrients into circulation
Elimination: waste products unused or unneeded by the body excreted
Anatomy of Digestive System
Digestive Tract: passageway nutrient intake will follow in which particles will be broken down and absorbed
Accessory Organs: organs necessary for digestion, but not components of the digestive tract (ex. liver, gallbladder, pancreas,
salivary glands)
Anatomy of Digestive System: Oral Cavity
Anatomy of Digestive System: Oral Cavity
Teeth: mastication
Full adult set = 32 teeth
Salivary glands: lubricates food, secretes salivary amylase (breakdown of starch)
Tongue: deglutition (swallowing)
Movement of food particles into pharynx & esophagus
Anatomy of Digestive System: Pharynx (throat)
Oropharynx:
post. region of oral cavity
Nasopharynx:
swallowing pushes soft palate superior preventing food from entering this cavity
Anatomy of Digestive System: Pharynx (throat)
Laryngeal pharynx:
Food moved into esophagus by epiglottis preventing food particles from entering trachea
Anatomy of Digestive System:Esophagus
Food is lubricated by mucus
Food moved into stomach via peristalsis
(smooth muscle)
Separated from stomach by gastroesophageal sphincter
GERD
Anatomy of Digestive System:Stomach
Upper-left quadrant
Greater curvature
Lesser curvature
Rugae
Pyloric sphincter
Anatomy of Digestive System: Stomach
Cells in stomach lining secrete substances that combine to form “gastric juice”
HCl
Pepsin
Mucus
Chyme (food + gastric juice) enters S.I.
Anatomy of Digestive Sytem:Small Intestine
Longest portion of digestive tract
Smaller in diameter than L.I.
Smooth muscle moves chyme via peristalsis
3 regions:
duodenum
jejunum
ilium
Anatomy of Digestive System:Small Intestine
Large amt. of mucus produced to protect lining of S.I.
Majority of digestion occurs here w/ help from liver & pancreatic enzymes
Majority of absorption occurs here as well
Anatomy of Digestive System:Small Intestine
Villi: small, finger-like projections in S.I.
Increase S.A.
Linked to circulatory system through blood vessels allowing absorbed nutrients to enter blood stream
Anatomy of Digestive System:Large Intestine
3 regions:
Ascending colon
Transverse colon
Descending colon
Hepatic flexure
Splenic flexure
sigmoid colon empties into rectum
Rectum anus
Anatomy of Digestive System:Large Intestine
No digestion occurs in L.I.
Some H20 absorbed
Undigested food stored & formed into solid waste material - feces
Anatomy of Digestive System: Accessory Organs
Salivary Glands: secretes saliva which contains salivary amylase (facilitates breakdown of starch)
parotid glands
submandibular glands
sublingual glands
Anatomy of Digestive System: Accessory Organs
Liver:
Located in upper right quadrant
Blood supply – hepatic artery/portal vein
MAJOR FUNCTIONS:
Produces bile (fat breakdown)
Stores glycogen (reg. blood sugar)
Breakdown of RBC’s (by-product is bilirubin)
Detoxification (filtration of poisons)
Anatomy of Digestive System: Accessory Organs
Gallbladder:
Bile storage
Chyme enters duodenum, gallbladder contracts, bile moves from cystic duct into S.I.
Anatomy of Digestive System: Accessory Organs
Pancreas:
Produces enzymes that digest organic molecules (proteins, fats, carbs, nucleic acids)
Produces alkaline (basic) substance used to neutralize chyme in digestive tract
Pancreatic duct joins common bile duct
Abdominal Quadrants
Common Digestive System Injuries/Illnesses
Appendicitis
Liver cirrhosis: replacement of liver tissue with fibrous/scar tissue
Intestinal rupture
Pancreatic cancer
Colon cancer
Gallstones
(cholesterol 80%/bilirubin 20%)
(Veriform) Appendix
Physiology of Digestive Process
Enzymes: proteins that initiate or speed up the rate of chemical reactions
Required in every phase of digestion
Very specific for the job they carry out
Hydrolysis: breakdown of particles by water
Digestive juices
Dilute food
Chemical process
Digestion: MOUTH (1) food enters oral cavity
Mastication breaks down food
Saliva moistens food
ENZYME: salivary amylase initiates breakdown of starches into simple sugars
Digestion: ESOPHAGUS
HA! TRICK QUESTION!
There is NO digestion that occurs in the esophagus
(2) Food is moved through the esophagus via peristalsis
Digestion: STOMACH
(3) Food reaches stomach and gastric juice secreted by stomach cells
RUGAE increases SURFACE AREA for digestion
ENZYME: pepsin is activated by HCl
breaks down all protein in the diet
end product is CHYME moved into small
intestine
Digestion: SMALL INTESTINE
Majority of digestion occurs in small intestine
(4) Duodenum: chyme mixed with bile
Break down fats so pancreatic enzymes work
ENZYME: PANCREATIC ENZYMES
lipase, amylase, trypsin, nucleases
Absorption
Villi located in small intestine
Contain significant blood supply
(5) Nutrients absorbed through villi into blood vessels and transmitted throughout bloodstream
Excretion
(6) Waste products accumulated in LARGE INTESTINE or transmitted to Urinary System