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DIGESTIVE SYSTEM (STRUCTURE (Chemical digestion (Add chemicals (enzymes)
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DIGESTIVE SYSTEM
GENERAL FUNCTION
- Break down food into small pieces to be absorbed.
- Eliminate what can't be broken down.
SMALL INTESTINE
Function
- Mechanical digestion - segmentation
- Chemical digestion - enzymes
- Absorption
Structure
-
Villi & Microvilli
- Increase intestinal absorptive surface
-
Circular fold
- Slow down movement of chyme.
- Increase area --> increase absorption
-
OTHER ORGANS
Rectum
- Storage well developed muscle to expel feces
Anal canal
- Mucus gland - lubrication
- Internal + external sphincters
Large intestine
- Water + electrolytes absorption.
STRUCTURE
Chemical digestion
- Add chemicals (enzymes)
- Mouth - saliva
- Stomach
- Small intestine - chemicals from pancreas
Peristalsis
- Adjacent segments of alimentary tract organs.
- Alternately contract or relax.
- Moving food along the tract distally.
Mechanical digestion
- Cut food up - small
- Teeth
- Stomach
- Small intestine (segmentation)
Pathway of food
Food --> Oral cavity --> Pharynx --> Esophagus --> Stomach --> Small intestine --> Large intestine --> Rectum --> Anus
Main organs
- Oral cavity
- Pharynx
- Esophagus
- Stomach
- Small intestine
- Large intestine
- Rectum
- Anus canal
- Anus
STOMACH
Function
- Store food
- Mechanical digestion - churning --> chyme
- Chemical digestion
Structure
Cardiac sphincter
- Prevent reflux of acid to esophagus
Pyloric sphincter
- Regulating amount of chyme moving on to small intestine
Chief glands
- Secrete pepsinogen + acid
- Become pepsin - enzyme breaks down protein
Gastric fold (rugae)
- Increase storage capacity of stomach
Parietal glands
- Hydrochloric acid + intrinsic factor.
- Needed to absorb vitamin B12 - needed to produce erythrocytes
MESENTERIES
Structure
- Double layer peritoneum from body wall to digestive organs
Intraperitoneal organs
- Liver, stomach, transverse colon, jejunum, ileum, sigmoid colon
Types
Mesocolon
- Associated with transverse + sigmoid colon
- Connected to posterior wall
-
Mesentery proper
- Associated with jejunum + ileum
Greater omentum
- Wrap around / enclose inflamed organ
- Fat storage
Retroperitoneal organs
- Duodenum, pancreas, ascending & descending colon, rectum
Function
- Hold organs in place.
- Store fat
- Provide place for blood vessels + nerves to "hang out"
ACCESSORY ORGANS
Gallbaldder
- Stores bile & concentrates bile to emulsify fat
Pancreatic acini
- Produce & secrete 22 or more enzymes - enter duodenum.
- Produce duct cells - produce bicarbonate alkaline substance
--> neutralize stomach acid.
Liver
- Make bile - emulsify fat
- Filters toxins out of blood
- Stores glucose as glycogen
- Stores some vitamins
- Processes fat & amino acids
- Make blood protein