Download Ch 18 BS and Ch 8 MT

Chapter 8 Medical Terminology
and
Chapter 18 Body Structures
The Digestive System
Functions of the Digestive
System
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AKA: alimentary canal, GI tract
Intake and digest food
Absorption of nutrients from food
Elimination of solid waste products
Organs
• Main
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Mouth
Pharynx
Esophagus
Stomach
Small intestine
Cecum
Colon
Rectum
Anus
• Accessory
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Teeth
Tongue
Salivary glands
Liver
Gallbladder
Pancreas
Vermiform appendix
Basics
• Digestion – the process of
altering the chemical and
physical composition of
food so that it can be used
by the cells in the body
• The digestive system is a
tube called the alimentary
canal or gastrointestinal
tract (GI tract)
• 29 feet long
• Acts like a hallway inside
the body
• Food must be digested and
then absorbed to be used
by the cells
Process
• Digestion
– Performed by the
organs of the digestive
system
• Absorption
– Performed by the
organs of the digestive
system
• Metabolism
– Performed by all the
cells in the body
Digestion (breakdown of food)
• Mechanical
– Chewing with teeth
– Breakdown in the stomach
• Chemical
– Action of digestive
enzymes
– Large molecules reduced
to smaller molecules that
can be absorbed through
the intestinal wall
Carbohydrate Digestion
• Very little digestion of
carbohydrates occurs before it
reaches the small intestine
• Gastric juices contains no
carbohydrate digesting enzymes
• Amylase from the pancreas
changes starches into sugars
– Maltose (malt sugar)
– Sucrose (cane sugar)
– Lactose (milk sugar)
• Intestinal enzymes (maltase,
sucrase and lactase) change the
sugars into simple sugar or
glucose (dextrose)
Protein Digestion
• Starts in the stomach and is
finished in the small intestine
• Gastric juice
– Rennin (only in infants)
– Pepsin
– Hydrochloric acid
• Every protein molecule is
made up of many amino acids
– Digestive enzymes split the
protein molecule up into single
amino acids (finished protein
digestion)
– Amino acids are referred to as
protein building blocks
Fat Digestion
• Most fats are
undigested until
emulsification by bile
occurs
• Then pancreatic
lipase splits the fat
molecules into fatty
acids and glycerin
(the end product of fat
digestion)
Digestive Tract
• Wall consists of 4 layers
– Mucosa (inside layer)
• Produces mucus that protects the wall from the digestive juices
and lubricates food passing through
– Submucosa
• Connective tissue that lies just below the mucosa
• Contains many blood vessels and nerves
– Muscularis
• Two layers of muscle tissue
• Cause wave like contractions called peristalsis that moves food
through the GI tract
• Also assists in mixing of food with digestive juice to further
breakdown particles
– Serosa
• Outer covering composed of visceral peritoneum
• Anchored to the posterior wall by the mesentary (large double fold
of peritoneal tissue)
Mouth
• Food enters the GI tract through
the mouth
• Digestive process begins
immediately
• Lined with mucous membrane
• Hard palate
– Bony structure in the anterior
formed by maxillary and
palatine bones
• Soft palate
– Above the posterior of the
mouth
– Consists of muscle
– Hanging in the center of the
soft palate is the uvula
Teeth
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Accessory Organ
– Incisors
– Canines (cuspids)
– Premolars (bicuspids)
– Molars (tricuspids)
Crown (exposed and visible portion
of the tooth)
Enamel (hardest tissue in the body)
Dentin (makes up the greatest
proportion of the tooth shell, found
in the root, crown and neck of the
tooth)
Neck (narrow portion surrounded by
gum tissue)
Root (fits into the socket of the
upper or lower jaw)
Chewing – mastication
Bolus – food after it’s been chewed
forms a rounded mass so that it can
be swallowed
Salivary Glands
• Accessory organ
located outside the
digestive tube
• Three pairs
• Saliva contains a
digestive enzyme
called salivary
amylase
– Begins the chemical
digestion of
carbohydrates
Pharynx & Esophagus
• Pharynx is made of muscle and lined with the mucous membrane
• Functions as part of the respiratory and digestive tract
• Esophagus or foodpipe is muscular and mucus lined. It connects the
pharynx to the stomach
• Cardiac sphincter or LES (lower esophageal sphincter) prevents the
food from going back up into the esophagus most of the time.
• GERD
– Gastroesophageal reflux disease
• Backward flow of stomach acid up into the esophagus
• Causes burning and pressure behind the sternum
• Can be stopped by weight loss, avoiding problem foods and
beverages, stopping smoking, use of antacids
• Hiatal hernia
– Common symptom is GERD
– Hernia is an organ being pushed through a wall that normally acts
as a barrier
– The stomach pushes through the hiatus or gap in the diaphragm
that allows the esophagus to pass through
Stomach
• Lies under the diaphragm
• Acts as a pouch for food to enter
after being chewed and swallowed
• Has three divisions
– Fundus (enlarged portion to the
left and above the opening of
the esophagus)
– Body (central part of the
stomach)
– Pylorus (lower narrow section
which joins the first part of the
small intestine
Stomach Cont.
• When empty not much bigger than a large sausage but has many folds
(rugae) that can expand quite a bit after a large meal
• Contractions of the stomach’s muscular walls mix the food with the
gastric juices and breaks it down into a semisolid called chyme
• Chyme is a continuation of the mechanical digestive process
• Peristalsis occurs and moves the food into the small intestine
• Disorders
– Gastritis
– Anorexia
– Nausea
– Emesis
– Ulcer –
• crater like wound or sore in the membrane of the stomach
caused by tissue destruction
• Can cause a burning pain
• Most cause by H-pylori bacteria
Small Intestine
• About 20 feet long
• Smaller in diameter than the large
intestine
– Duodenum
– Jejunum
– Ileum
• Mucous lining contains thousands of
microscopic glands that secrete
digestive juice
• Disorders
– Enteritis
– Gastroenteritis
– Malabsorption syndrome
• Failure of the small intestine to
absorb nutrients properly
• Caused by enzyme deficiencies
– Genetic conditions (CF)
Liver
• Secretes bile into ducts so it is classified as an endocrine gland
(largest gland in the body)
• Accessory organ
• Fats form large globules and must be broken down by bile into smaller
particles (emulsification)
• The common bile duct drains bile into the small intestine
• Disorders
– Jaundice (excessive amounts of bile absorbed into the blood when
bile can’t be drained from the liver)
• Causes yellowing of the skin
– Hepatitis
• Characterized by jaundice, liver enlargement, anorexia,
abdominal discomfort, gray-white feces, dark urine
• Caused by alcohol, drugs, toxins, bacterial or viral infections
– Cirrhosis
• Degenerative liver condition
• Caused by hepatitis, chronic alcohol abuse, malnutrition or
infection
Gallbladder
• Located on the
undersurface of the liver
• Concentrates and stores
bile produced in the liver
• When chyme that contains
lipids (fat) enters the
duodenum (first section of
the small intestine) it starts
the gallbladder contracting
by stimulating the secretion
of cholecystokinin from the
mucosa of the duodenum.
The contractions then force
bile into the small intestine
• Disorders
– Cholelithiasis (gallstones)
– Cholecystitis (caused from
gallstones)
Pancreas
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Accessory organ
Lies behind the stomach
An exocrine gland
Pancreatic juice is the most
important digestive juice
– Contains enzymes that
digest all three major kinds
of food
– Also neutralizes
hydrochloric acid
– Enters the duodenum the
same place bile enters
• Disorders
– Diabetes mellitus
– Pancreatitis
Large Intestine
• About 5 feet long
• Forms the lower portion of the
digestive tract
• Cecum – pouch-like area
• Ascending colon – food flows
upward on the right side of the
body
• Transverse colon – extends
across the front of the abdomen
from right to left
• Descending colon – runs
downward on the left side
• Sigmoid colon – S-shaped
segment that attaches to the
rectum
• Rectum – storage pouch
• Anal canal – end portion of the
rectum that ends at the external
opening
Large Intestine
• Undigested & unabsorbed food enters the large
intestine after passing through the ileocecal
valve
• Chyme found in the small intestine becomes
fecal matter in the large intestine as water and
salts are reabsorbed
• Bacteria in the large intestine release other
nutrients and are responsible for the synthesis of
vitamin K and the production of some
B-complex vitamins
• Passage of food through the large intestine
takes 3 to 5 hours
Disorders of the Large Intestine
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Diarrhea
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Constipation
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Any inflammatory condition of the large intestine
Symptoms are diarrhea, abdominal cramps or constipation, bleeding and intestinal ulcers
Can be caused by emotional stress, (IBS), autoimmune disease
May be corrected by surgically removing the affected portions of the colon
Crohn’s Disease
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Inflammation of abnormal saclike outpouchings of the intestinal wall
Often found in adults over 50 who eat a low fiber diet
Colitis
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Decreased intestinal motility
Feces lose volume as water is absorbed which reduces the stimulation of the bowel
emptying reflex resulting in more fecal retention
Diverticulitis
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When contents move quickly and fluids can’t be reabsorbed
Often caused by bacteria or parasites
Because of the water loss involved untreated diarrhea may quickly lead to dehydration and
possible death
Autoimmune colitis that also affects the small intestine
Colorectal cancer
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Occurs most frequently in adults after age 50 and more common in men
Second leading cause of death from cancer in the US and 4th most common type of cancer
after prostate, breast, and lung
Diagnosed during a visual exam during a sigmoidoscopy or colonoscopy
Appendix
• Vermiform appendix
– Vermis (worm shape)
– Contains lymphatic tissue
and may play a minor role in
immunologic defense
mechanisms
– Directly attaches to the
cecum
– Inflammation is appendicitis
and can be evaluated by a
digital rectal exam because
it’s very close to the rectal
wall
– If infection persists the
appendix may rupture and
release infection into the
abdominal cavity causing
infection of the peritoneum
and other internal organs
which can cause death
Peritoneum
• Sheet of serous membrane that lines the abdominal
cavity and covers the organs located in it including most
of the digestive organs
• The parietal layer of the peritoneum lines the abdominal
cavity
• The visceral layer covers the abdominal organs
• Peritonitis
– Usually a result from bacterial infection, often from a ruptured
appendix
– Characterized by abdominal distension, pain, nausea, vomiting,
tachycardia, fever, dehydration
– Circulatory shock and heart failure may result
colonoscopy
Laparoscopic
cholecystectomy
appendectomy
hepatectomy