Download Small Intestine

Digestive System Unit Review Packet
*You should study your digestive system notes, this packet, warm-ups and
homework*
1) Explain the difference between digestion and metabolism:
i. Digestion:
1. Breakdown of ingested food
2. Absorption of nutrients into the blood
ii. Metabolism:
1. Production of cellular energy (ATP)
2. Constructive cellular activities
2) What makes up the digestive system:
a. Alimentary canal:
i. Mouth, Pharynx, Esophagus, Stomach, Small
intestine, Large intestine, Rectum, and Anus
b. Accessory organs:
i. Gallbladder, Pancreas, Liver, and Salivary glands
3) Digestive Activities of the Mouth
a. What is the function of saliva?
i. - Mixture of mucus and serous fluids
ii. Helps to form a food bolus
iii. Contains salivary amylase to begin starch digestion
iv. Dissolves chemicals so they can be tasted
b. Mastication: (chewing) of food & Mixing with saliva
c. Mechanical breakdown - Food is physically broken down
by chewing
d. Chemical digestion :
i. Food is mixed with saliva
ii. Breaking down of starch into simple sugars by
salivary amylase
4) Digestive Activities of the Esophagus (FOOD TUBE)
a. Runs from pharynx to stomach through the diaphragm
b. Passageway for food only
c. Peristalsis: (slow rhythmic squeezing)
i. Moves the bolus toward the stomach. The
cardioesophageal sphincter is opened when food
presses against it.
1. Bolus: Mass of food and saliva
5) Digestive Activities of the Stomach
a. Food enters at the Cardioesophageal Sphincter
i. Acid Reflux: Malfunction of Cardioesophageal
Sphincter. Chyme splashes back into esophagus.
b. Chyme: processed food mixed with stomach acid and
enzymes
c. Chemical Digestion: Chemical breakdown of proteins
begins
d. Mechanical Digestion: Churning (peristalsis) of food
breaks into smaller piece
e. Internal anatomy of the stomach:
i. Rugae : internal folds of the mucosa
ii. Mucous neck cells – produce a sticky alkaline (basic)
mucus (prevents stomach from digesting itself.
iii. Gastric glands – secrete gastric juice (regulated by
Gastrin)
iv. Chief cells – produce protein-digesting enzymes
(pepsinogens)
v. Parietal cells – produce hydrochloric acid (pH=2)
which activates the release of pepsinogens (turns
into pepsin) and creates a hostile environment for
microorganisms.
vi. Endocrine cells – produces Gastrin which activates
the release of hydrochloric acid.
1. Gastrin: Presence of food or falling pH causes the
release of gastrin which causes stomach glands to
produce protein-digesting enzymes (Pepsin).
**The only absorption that occurs in the stomach is of alcohol and
aspirin**
f. Gastric (stomach) Ulcer: Can be caused by excessive stress,
alcohol use, or bacteria. Stress and alcohol cause a greater
amount of hydrochloric acid to be released from the Parietal
cells and less mucus to be secreted from the Mucous neck
cells.
i. Symptoms: Abdominal pain, dark stools, burning.
g. Pyloric Sphincter: Connects stomach to small intestine
6) Digestion and Absorption in the Small Intestine: (Digestion of
food ends here)
a. Small Intestine: Muscular tube extending from the
pyloric sphincter to the ileocecal valve.
b. Three sections of the Small Intestine: (D.J. Ileum)
i. Duodenum - Attached to the stomach at the Pyloric
Sphincter. Area where enzymes are added to small
intestine from gallbladder and pancreas.
ii. Jejunum- middle section
iii. Ileum- from jejunum to large intestine
c. Villi: Fingerlike structures formed by the mucosa
i. Function: Give the small intestine more surface area
in order to increase absorption of nutrients and water.
1. Substances are transported directly to the liver by
the hepatic portal vein.
7) Digestive Activities of the Accessory Organs:
a. Liver: Produces bile which is sent to the gallbladder via the
common hepatic duct.
i. What is Bile: Emulsifier that breaks fat
(mechanically) into smaller droplets.
b. Gallbladder: Stores and concentrates bile. Releases bile in
the presence of fat into the Duodenum.
i. Gallstones: Hard masses made from cholesterol and
other things found in the bile.
1. Complications/Symptoms: Can cause a blockage
in the bile duct. Bile can back up causing
Jaundice (yellowing of the skin and eyes).
2. Can a person live without their Gallbladder?
Explain:
c. Pancreas: Produces many digestive enzymes that break
down all categories of food (Lipase-break down fats,
Amylase-break down starch, Trypsin and Pepsin-break
down proteins).
i. Enzymes are secreted into the duodenum of the small
intestine.
ii. Also produces an alkaline (basic) fluid to neutralize
the acidic chyme.
8) Digestive Activities of the Large Intestine:
a. Function: Absorption of water (slow peristalsis)
i. Eliminates indigestible food from the body as feces
b. Function of resident bacteria in the large intestine:
i. Produce some vitamin K and B
ii. Release gases
c. Sections of the Large Intestine:
i. Ascending colon
ii. Transverse colon
iii. Descending colon
iv. Sigmoid colon
v. Rectum
vi. Anus
d. Presence of feces in the rectum causes a defecation reflex
i. Internal anal sphincter is relaxed
ii. Defecation occurs with relaxation of the voluntary
(external) anal sphincter
1. How is this important when “potty training”
children? The child has to learn to recognize the
signal from the defecation reflex that relaxes the
internal anal sphincter. They then have to learn to
control the external anal sphincter until they are at
the proper place to release feces.