Download Digestive System - Northwest ISD Moodle

5/6/16
 Oral Cavity
 Ingestion
 Mechanical breakdown
 Chemical breakdown
 Propulsion (swallowing)
 Oral Cavity
 Salivary glands
 1st Accessory Organ
 Parotid
 Sublingual
 Submandibular
 Oral cavity -> Pharynx -> Esophagus
-> Stomach
 Stomach
 Mechanical breakdown
 Chemical breakdown
 Rugae: folds on the inside of the
wall of the stomach
 Allows the stomach to stretch
 Empty stomach: approx 50ml
 Full stomach: approx 2 liters
 Stomach
 3 layers
 pH of 1.5 – 2.5
 Small Intestine
 3 segments
 Duodenum: first and shortest
 Jejunum
 Ileum
 Duodenum
 Where liver, gallbladder and pancreas secretions enter
 Jejunum:
 Follows duodenum, about 8 feet long
 Small intestine lining
 Villi
 Microvilli : “brush border”
 Ileum
 3-5 feet long
 Small intestine:
 Major site for absorption for the end products of
digestion
 A few more notes about enzymes and hormones.
 The gallbladder releases bile into the small intestine.
The hormone that stimulates this release is called
cholecystokinin-pancreozymin.
 The pancreas can release a bicarbonate into the small
intestine, in addition to its digestive enzymes. The
hormone that stimulates the release of bicarbonate is
secretin.
 Proteins are broken down by enzymes in gastric and
intestinal juices.
 Fats are broken down by lipase enzyme in the small
intestine.
 Carbohydrates are broken down by enzymes in the
mouth and small intestine.
 The major final product that results from the digestion
of carbohydrates is glucose.
 A chemical digestion process called
enzymatic hydrolysis can break the bonds holding the
molecular ‘building blocks’ within the food together.
 Water splits larger compounds into smaller ones.
 Hydrochloric acid converts pepsinogen into pepsin.
 Enzymes are very specific, they fit their substrates like
a “key-in-a-lock.”
 Enzymes are pH sensitive because changes in
hydrogen ion concentrations can affect the shape of
the protein molecule.
 A wavelike muscle contraction that moves food along
the digestive system is called perstalsis