Download NAME: ____________ DATE: BLOCK: ___ GASTROINTESTINAL

NAME: _____________________________________________________ DATE: _______________ BLOCK: ___
GASTROINTESTINAL (GI) TRACT
• GI or alimentary canal – continuous, coiled, hollow tube that winds through ventral body cavity from
mouth to anus
– Entire GI is ~30 feet in cadaver, but shorter in living person due to muscle contractions
– Includes mouth, pharynx, esophagus, stomach, small intestine, large intestine, and ends at the
anus
– Other accessory organs include salivary glands, pancreas, liver, gall bladder
FUNCTIONS OF DIGESTIVE SYSTEM
1. Ingestion – putting food into mouth
2. Propulsion – moving food from one organ to the next
3. Mechanical digestion – breaks down food _______________________ into smaller pieces
4. Chemical digestion – large _________________ are broken down into their building blocks by
____________________
5. Absorption – transport of digested end products from the GI tract to the blood or lymph
6. Defecation – elimination of indigestible food that leaves through the anus in the form of feces
ACTIVITIES OF MOUTH, PHARYNX, AND ESOPHAGUS
• Mouth
– Chewing begins mechanical breakdown of food
• Pharynx
– Propels food into esophagus by _____________________ (involuntary smooth muscle
contractions)
• Epiglottis covers windpipe (trachea) to prevent food from moving down into lungs
• Esophagus
– ____________________ food into stomach via peristalsis
ACTIVITIES OF STOMACH
• Stomach – a storage tank
– C-shaped sac with sphincters at each end
• __________________________ or esophageal sphincter prevents food from going back
into esophagus
• _______________________________ opens to allow food to move into the small
intestine
– Physical digestion occurs as stomach grinds and churns food
– Chyme - partially digested food that leaves the stomach
– Chemical digestion occurs with enzymes
• Gastric glands – in stomach lining; release ________________________
– Gastric juice – includes digestive enzymes, intrinsic factor, hydrochloric acid
(HCl), and mucus
» Intrinsic factor helps absorb vitamin B12
• ____________________ – enzyme that breaks down protein (activated by HCl)
ACTIVITIES OF THE SMALL INTESTINE
• A tube that is 8 – 18 feet long and twisted into coils
• The major digestive organ
• Three subdivisions
– ____________________________ (5% of total length)
– ____________________________(40% of total length)
– ____________________________ (almost 60% of total length)
• Nearly all food absorption occurs in the small intestine!
• Duodenum
– Pancreatic ducts dump _____________________________________ into duodenum
– Bile duct (joins with pancreatic ducts) dumps bile from liver into duodenum
• Jejunum and ileum - primary function is absorption
– Intestinal ___________________ tiny projections of inner wall of small intestine; greatly
increase surface area for absorption
– Each villus contains blood capillaries and a lacteal into which foodstuffs are absorbed
• _____________________________ – opens to let chyme pass into large intestine
ACTIVITIES OF THE LARGE INTESTINE
• Larger in diameter than the small intestine, but not nearly as long (~5 feet)
• Major function is to dry out indigestible food residues by absorbing water and then eliminate them as
feces
• Subdivisions: cecum, appendix, colon, rectum, and anal canal
• ______________________ – first part of large intestine; sac-like with worm-like appendage called
appendix
• Colon – parts in order are: ______________________ (travels up), ______________________ (travels
across), descending (travels down), and then ______________________ (S-shaped)
• Rectum – stores feces and leads to anal canal
• Anus – ending of GI; voluntary sphincter opens to release feces
ACTIVITIES OF ACCESSORY ORGANS
• Teeth – breakdown, grind, and tear food into smaller pieces
• Salivary glands release saliva; contain mucus to soften food and salivary amylase, which begins
carbohydrate digestion
– ______________________– largest, lie anterior and somewhat inferior to each ear
– Sublingual gland – smallest; lie on floor of mouth inferior to tongue
– ______________________– lie in floor of mouth on inside surface of lower jaw
• Pancreas – soft, pink, triangular gland; secretes pancreatic juice
– Pancreatic duct – tube that carries pancreatic juice to duodenum
– Pancreatic juice contains the following:
• ______________________ - neutralizes acidic chyme coming from stomach
• amylase - enzyme that breaks down carbohydrates
• lipase - enzyme that breaks down ______________________
• trypsin, chymotrypsin, and carboxypeptidase - enzymes that breakdown proteins
• ______________________ – enzyme that breaks down nucleic acids
• Liver – largest gland in the body; digestive function is to produce bile
•
– ___________________ – leaves liver through the hepatic duct and enters duodenum through
bile duct
• Yellowish-green liquid containing bile salts, bile pigments (bilirubin), cholesterol,
electrolytes, and lipids (no enzymes)
• Only the bile salts and lipids help with digestion
• ______________________emulsify fats by physically breaking large fat globules into
smaller ones
______________________– small, green sac under liver that stores bile
HOMEOSTATIC IMBALANCES
• Gall stones – if bile is stored in gall bladder too long or too much water is removed, the cholesterol in it
crystallizes forming gall stones
– Can cause blockage of hepatic or bile ducts and bile begins is released into bloodstream instead
• Bile in blood and eventually tissues causes jaundice
• ______________________ – inflammation of liver; often cause by virus (also called hepatitis)
• Cirrhosis – chronic inflammation of liver; can be from drinking too much alcohol
• Heartburn – when cardiac sphincter does not close tightly and allows acidic stomach juices to enter
esophagus
– Hiatal hernia – superior part of stomach protrudes slightly above the diaphragm; which
weakens cardiac sphincter
• Peptic ulcers – erosion of stomach lining (open sore in membrane), which exposes the lining to acid;
often caused by some bacteria (Helicobacteri pylori)
• ______________________ – inflammation of pancreas caused by pancreatic enzymes breaking down
the pancreatic tissue itself
• Diverticulitis – diverticula are formed by the inner layer of the intestine protruding through the large
intestine wall; causes inflammation and pain
– Caused by not eating enough bulk (fiber); colon narrows and puts more pressure on walls
• ______________________ – large intestine does not absorb enough water from feces; loss of
electrolytes and fluids can cause severe dehydration
• Constipation – too much water is removed from feces; can be caused by low fiber diets
• Impacted teeth – teeth that remain embedded in jawbone; can cause pressure and pain; often occurs
with wisdom teeth
• ______________________ – infected appendix; bacteria can accumulate because its twisted
• Hemorrhoids – enlarged and inflamed branches of the rectal vein in the anal canal that cause itching,
pain, and sometimes bright red bleeding
• Vomiting – complex reflex that empties stomach through esophagus, pharynx, and mouth (vomiting
center in medulla oblongata)