Download Why a Digestive System ?

Why a
Digestive System ?
 Kingdom Animalia
 Heterotrophism
Digestive System
General Function
 The digestive system is responsible for the …
 Intake and breakdown of complex foods into two
categories:


Useable materials (nutrients)
Non-useable materials (wastes)
Six Major Digestive Processes
1.
2.
3.
4.
5.
6.
INGESTION
PROPULSION
MECHANICAL DIGESTION
CHEMICAL DIGESTION
ABSORPTION (of nutrients)
DEFECATION (of wastes)
GI
Tract
 Oral Cavity
 Esophagus
 Stomach
 Small Intestine
 Large Intestine
 Anus
Accessory
Organs
 Teeth
 Tongue
 Gall Bladder
 Glands
 Liver
 Pancreas
 Salivary
GI Tract and
Accessory Organs
Digestive Processes of the Oral
Cavity
 INGESTION
 MECHANICAL DIGESTION
 CHEMICAL DIGESTION
Oral Cavity
 Borders:
Anterior  Lips
***
Lateral  Cheeks
Superior  Palate (Hard/soft)
Inferior  Tongue
 Tongue:
Accessory Organ for:
mixing, taste buds
THE ESOPHAGUS
 carries bolus from oral cavity to
stomach.
PERISTALSIS
the automatic, involuntary,
continuous propulsion of food
through the GI tract.
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Functional Anatomy cont
 PART II
 The STOMACH
Digestive Processes of the Stomach
 Storage tank
 Chemical digestion of proteins
 Mechanical digestion
 Bolus  Chyme
 Volume— 50 ml  4 liters
 Rugae allow for expansion
 Enervated by ANS
Gastric Sphincters
 Cardiac Sphincter
 Pyloric Sphincter
 Functions:
 Regulates/controls propulsion of food into/out of the
stomach
Cardiac
sphincter
Pyloric sphincter
PART III
 SMALL INTESTINE
 ACCESSORY
STRUCTURES
 LIVER
 GALL BLADDER
 PANCREAS
Small Intestine
Three Regions:
 Duodenum
 ~1 ft
 Jejunum
 ~8 ft
 Ileum
 ~12 ft
Digestive Processes
of the Small Intestine
 CHEMICAL DIGESTION OF…
 CARBOHYDRATES
 PROTEINS
 LIPIDS
 NUTRIENT ABSORPTION!!
Microscopic Anatomy of the Small
Intestine
 Mucosa
 Circular folds (“plicae circulares”)

Slow propulsion of chyme
 Villi
 Finger-like projections w/ capillaries in center
 Microvilli
 Small projections of cells that absorb nutrients (aka
absorptive cells)
Before Nutrient Absorption
occurs…
CHEMICAL DIGESTION MUST
BE COMPLETED IN THE SMALL
INTESTINE
THROUGH ENZYMATIC
ACTIVITY!
But There’s a Problem…
THE SMALL
INTESTINE LACKS
CELLS THAT
PRODUCE/SECRET
E DIGESTIVE
ENZYMES!
Accessory Structures to the Rescue
LIVER
Largest internal organ of the body
 Over 500 metabolic functions
 Digestive Function:
 Produces BILE for chemical digestion of
LIPIDS

GALL BLADDER
 Small sac embedded in liver
 Stores bile produced by liver
PANCREAS
 Embedded within outer duodenum
 Produces PANCREATIC JUICE containing:
 Secretes PJ into duodenum via common bile duct
 amylases
 proteases
 lipases
 Nucleases
 PART IV
 THE LARGE INTESTINE (aka COLON)
Digestive Processes of the Large
Intestine
 ABSORPTION OF:
 WATER
 VITAMINS
 PRODUCTION OF VITAMIN K
 E. coli; bacterial flora
 PROPULSION OF FECES FOR DEFECATION