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Digestive SystemDigestive System
AnnouncementsAnnouncements
Exams
Lab notes will be on reserve in library and on the web
Goals of the Digestive SystemGoals of the Digestive System
1. Extract nutrients from food
2. Transform nutrients into useful forms
Ex- oreo= glucose
3. Absorb nutrients and distribute them where they are needed
Functions of the Digestive Functions of the Digestive SystemSystem
Ingestion: intake of nutrients
Digestion: breakdown of large particles into smaller ones
Absorption: uptake of nutrient molecules
Defecation: elimination of undigested residues
Actions of the Digestive Actions of the Digestive SystemSystem
1. Motility- Breaks up food- Moves food through the GI tract (Peristalsis)- Mixes with digestive enzymes
2. Secretion- Release of enzymes and hormones for chemical
digestion and regulation
3. Membrane Transport- Absorption of nutrients from the tissues by the
blood and lymph for transport
Stages of DigestionStages of Digestion
Mechanical: physical breakdown of food
Chemical: digestive enzymes hydrolyze food particles to break larger molecules into smaller ones
Some nutrients are absorbed with out digestion– Vitamins, minerals, cholesterol, water
Anatomy of the Digestive Anatomy of the Digestive SystemSystem
Oral Cavity Pharynx Esophagus Stomach Pyloric Sphincter Small Intestine Large Intestine
Accessory OrgansAccessory Organs
Teeth Tongue Salivary Glands
Liver Gall Bladder Pancreas
Oral CavityOral CavityFunctions:
– A. Ingestion: cheeks lips and tongue mobilize food
– B. Digestion: Mechanical
– Mastication Chemical
– 3 salivary glands
– Digests some starches and fat
PharynxPharynx
Motility: pharyngeal constrictors force food down during swallowing
EsophagusEsophagus
Straight muscular tube about 1 foot long
Motility: muscular contraction moves food towards stomach
www.mywebmd.ca.com
Heartburn and the EsophagusHeartburn and the EsophagusHeartburn, “ acid reflux”, is caused by acid and food
going from the stomach into the esophagus
The diaphragm normally prevents acid reflux, in conjunction with the lower esophageal sphincter.
When this fails, the burning sensation felt is known as “heartburn”
May be linked to a rare type of cancer, adenocarcinoma
StomachStomach Muscular sac on the left
side of the peritoneal cavity
Functions: – Food storage – Mechanical digestion– Chemical digestion
Rugae in the StomachRugae in the Stomach
Rugae- folds in the stomach lining that allow it to expand with more food
How do we vomit?
http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion
Pyloric SphincterPyloric Sphincter
Ring of smooth muscle
Regulates the passage of material from the stomach into the duodenum
http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion
Digestion in the StomachDigestion in the Stomach
Mechanical Digestion:– Muscular contraction
Chemical Digestion:– Secretes digestive enzymes and HCl
Small IntestineSmall Intestine http://www.afns.ualberta.ca/bbo/1/ANATOMY/SI1.asp 2 meters long, 1 inch
in diameter, 5-6 meters in cadaver
Functions: – Chemical Digestion– Nutrient Absorption– Motility
Anatomy of the Small Anatomy of the Small IntestineIntestine
Duodenum (25 cm): 1. Receives stomach
contents, pancreatic juice and bile
2. Neutralizes stomach acid and pepsin
3. Pancreatic enzymes and bile take over chemical digestion
Fig 25.22
Anatomy of the Small Anatomy of the Small IntestineIntestine
Jejunum (2.5m)
Ileum (3.6 m)– Reabsorbs bile acids
Functions of the Small Functions of the Small IntestineIntestine
Motility: smooth muscle contract
Digestion: chemical enzymes received from the pancreas, liver and gall bladder
Nutrient reabsorption:microvilli increase surface area
Microvilli
Dynamic Human: MicrovilliDynamic Human: Microvilli
Large IntestineLarge Intestine
Functions– Motility
– Reabsorbtion of Water and Electrolytes
Symbiotic bacteria– Synthesis Vitamins B & K
Anatomy of the Large Anatomy of the Large IntestineIntestine
Transverse Colon: right to left
Ascending Colon: Descending Colon:
up the right side down the left side
Cecum: sac on Sigmoid Colon:
lower right side S-shaped
Anatomy of the Large Anatomy of the Large IntestineIntestine
Rectum: straight down Anal Canal: out the
body Appendix: hangs off
cecum– Important in Immunity
Enzymes Involved in Enzymes Involved in Chemical DigestionChemical Digestion
Saliva:– Amylase: breaks down starch– Lipase: breaks down fats when it enters the
stomach Low pH of the stomach activates the enzyme
Enzymes Involved in Enzymes Involved in Chemical DigestionChemical Digestion
• Stomach:• Digestive chemicals-
• HCL: activates enzymes, breaks up foods• Pepsin: digests proteins• Renin: digests milk
Pepsin FormationPepsin Formation
• Interactions between Cells• Chief Cells make pepsinogen• Parietal Cells make HCl• Pepsinogen is cleaved by HCl into Pepsin
Dynamic Human: Pepsin Dynamic Human: Pepsin FormationFormation
Enzymes Involved in Enzymes Involved in Chemical DigestionChemical Digestion
• Small Intestine• Two sources of
enzymes
• Liver and Gall bladder• Pancreas
Enzymes Involved in Enzymes Involved in Chemical Digestion in the Chemical Digestion in the
Small IntestineSmall Intestine• Liver secretes bile that is active in the small
intestine• Bile: aids in fat digestion and absorption
•Activates pancreatic enzymes
•Synthesized from cholesterol
•Bacteria in the small intestine use bilirubin to make your feces brown
• Gall bladder stores and concentrates bile
Gall StonesGall Stones
What is a gall stone?
How do they treat gall stones?
How is the gall bladder removed?
Enzymes Involved in Enzymes Involved in Chemical Digestion in the Chemical Digestion in the
Small IntestineSmall Intestine Pancreas: secretes pancreatic juice
1. Amylase: breaks down starch
2. Lipase: breaks down fats
3. Ribonuclease (RNAase): breaks down RNA
4. Deoxyribonuclease (DNAase): breaks down DNA
5. Zymogens: inactive enzymes that activate in the small intestine
Mechanism of AbsorptionMechanism of Absorption
Membrane Transport:– Nutrients pass through membrane surface– The greater the membrane surface area, the
greater the amount of nutrients that can be transported
Surface Area– Rugae– Microvilli
Final Destinations of Digestion Final Destinations of Digestion ProductsProducts
Starches bloodstream
Fats lymph vessels (lacteals)
Proteins bloodstream
Dynamic Human: Dynamic Human: VisualizationVisualization
Cat DissectionCat Dissection
Be able to locate and identify– Esophagus– Stomach– Small Intestine– Large Intestine
Ascending colon Transverse colon Descending colon
Also know accessory organs– Tongue– Teeth– Gall Bladder– Liver
ConclusionConclusion