Download Digestive System

Digestive System
-breaking down of food through enzymatic activity
-elongated tube beginning at mouth &
terminating at anus
Functions:
• ingest food
• break down food
• extract & absorb nutrients
• eliminate wastes
• Breakdown polymers to monomers
1) Lipids
-glycerol & fatty acids
2) Carbohydrates
-monosaccharides (glucose)
3) Protein
-amino acids
Bozeman Digestive System
Digestion in the mouth
-mastication (chewing)
-mixed w/salivary amylase (breaks down carbohydrates)
-lubrication
•
Control of digestive secretions:
-only when food is present
-under neurological control
-touch receptors on tongue
Salivary glands
Digestive glands & enzymes:
1) Salivary glands
-3 pairs of salivary glands… secrete saliva
-1 pair secrete salivary amylase (breaks
down starches)-parotid
-2 pairs secrete mucin (lubricates mouth &
causes adhesion of food particles)submandibular and sublingual
-food leaving mouth is known as a bolus
Salivary glands
(a) The stomach wall has three layers of smooth
muscle, each oriented in a different direction,
that allow the stomach to churn and mix food
with digestive secretions.
2)
Esophagus
Sphincter
Longitudinal
layer of muscle
Sphincte r
Digestive Organs
Circular layer
of muscle
Oblique layer
of muscle
Stomach
-mixes & stores food
-digestion of protein
-gastric glands secrete hydrochloric acid (HCI),
pepsin, gastric lipase
-HCI lowers pH to kill any bacteria
-pepsin breaks down proteins
- gastric lipase breaks down lipids
-food leaving stomach is known as chime
Khan Academy: Stomach
Digestion in the stomach:
• Mucus (Mucus)
-protects stomach walls
• HCL (Parietal)
-soften proteins
-lowers pH (0.8-2) Pepsin
-protein to proteases (peptone & polypeptides)
• Gastric lipase (Chief)
-breaks down milk-cream, & egg yolk
• Rennin (Chief)
-breaks down milk (child stomach)
Digestive Organs (cont.)
The liver produces
bile, which is stored in
the gallbladder before
being released into
the small intestine.
3) Liver
-2nd largest organ in body
-secretes bile & sends it to gallbladder for storage
-bile salts emulsify lipids
-gatekeeper of blood
-removal of toxins & keeps blood constituents
constant
Liver
Gallbladder
Pancreas
(behind
stomach)
Small intestine
The pancreas produces
several digestive
enzymes that act in the
small intestine
4) Pancreas
-pancreatic juices (alkaline) containing enzymes
to break down carbohydrates, protein, & fats
5) Small intenstine
-receives enzymes from pancreas & bile from
gallbladder
Digestion in the small intestine:
-alkaline environment
-pancreatic juices
-villi & microvilli: absorption
-bile component (cystic duct)
-bile pigments, cholesterol, water, & bile
salts
Absorption in the S.I.
Digestion in the large intestine:
• Function
-removes water, salts, & storage of
non-digestible food
-bacteria
-help digest indigestible food
-provide some vitamins
What substances gets absorbed
in the mouth and large intestine?
In the mouth:
-no food (only sugars)
-some drugs and some alcohol
-some glucose (most absorption)
In the large intestine
-water absorption
Absorption mechanisms
-osmosis
-diffusion
-active transport
Routes of absorption
-circulatory & lymphatic
systems
Passage of food
-peristalsis
-rhythmic contractions of smooth muscle tissue
Peristalysis (LI)