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The Digestive System: For Discussion: True or False

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Title: The Digestive System: For Discussion: True or False


1
The Digestive System For Discussion True or
False?
1. Of all the organs, the stomach is most
central to the structure and function of the
digestive system.
False
2. The liver is the 2nd-largest organ in the
body.
True
  • The liver is the 2nd-most complicated organ in
    the body.

True
4. The liver is the 3rd-most immediately vital
organ in the body.
True
5. The pancreas is the only organ of the human
body that can regenerate.
False
6. The large intestine is larger than the small
intestine.
False, except that is larger in diameter. It is
much shorter.
7. The digestive system contains the hardest
substance in the human body.
True
8. The human appendix, like the human coccyx, is
a vestigial organ.
True
2
The Digestive System
ALIMENTARY CANAL
ACCESSORY GLANDS
Mouth Mechanical breakdown of food begins
chemical digestion of carbohydrates
Salivary glands Secrete saliva, which contains
enzymes that initiate breakdown of carbohydrates
Pharynx Connects mouth with esphagus
Esophagus Peristalsis pushes food to stomach
Stomach Secretes acid (HCl) and enzymes. Mixes
food with secretions to begin enzymatic digestion
of proteins
Liver Produces bile, which emulsifies fat
Small Intestine Mixes food with bile and
pancreatic juice. Final breakdown of food
molecules main site of nutrient absorption
Gallbladder Stores bile and introduces into small
intestine
Pancreas Produces and secretes pancreatic juice,
containing digestive enzymes and bicarbonate
ions, into small intestine
Large Intestine Absorbs water and electrolytes to
from feces
Rectum Regulates elimination of feces
Anus External sphincter
3
The Digestive System
I. Alimentary Canal
-continuous muscular tube through which food
passes from mouth to anus
A. Mouth
-receives food, food bolus is mixed, positioned,
and swallowed by tongue during mastication,
provides for mechanical digestion with teeth and
jaw muscles
1. Cheeks
-contain muscles for chewing (masseter and
temporalis) and positioning of food in the oral
cavity (buccinator)
2. Lips
-made from skeletal muscle (orbicularis oris)
-thin-skinned, many sensory receptors, important
in sensing temperature and texture of food
-external borders mark boundaries between skin
of face and mucous membranes of alimentary canal
4
2. Lips
Rx Cold Sores
-caused by Herpes Simplex I virus
-infects skin and mucous membranes during lytic
phase, when it is contagious
-infects nerve cell during its latency, making
infection permanent, triggered by stress
-treated with Acyclovir, which mimics the
nitrogenous bases adenine and guanine
3. Tongue
-most powerful skeletal muscles in the body, per
square inch
-mix and position food between teeth during
chewing, push food toward the pharynx during
swallowing
-covered with mucous membranes and rough
papillae, some of which provide friction and
some of which house taste buds
5
A. Mouth
Lingual tonsils
Epiglottis
Lip
Hard palate
Palatine tonsils
Soft palate
Uvula
Palatine tonsils
Papillae
Tongue
Lingual frenulum
Vestibule
Lip
6
A. Mouth
4. Palate
a. Hard palate
-forms the roof of the oral cavity
-formed by the fusion of the palatine processes
of the maxillae in the front and the palatine
bones in the back
b. Soft palate
-muscular arch which extends from the posterior
hard palate to taper back and down into the
cone-shaped uvula
-muscles draw soft palate and uvula to prevent
food from entering the nasal cavity
c. Tonsils
-lymph nodes associated with the mucous
membranes of the respiratory passages
-help protect the body against infection by
harboring macrophages and lymphocytes
7
A. Mouth
4. Palate
c. Tonsils
-lingual, palatine, and pharyngeal (adenoids)
Rx Tonsilitis
-sore throat inflammation of the tonsils caused
by bacterial or viral infection
-can spread to cause infection of the middle
ear otitis media
Pharyngeal tonsils (adenoids)
-treated with antibiotics, or tonsilectomy
Palatine tonsils
Lingual tonsils
5. Teeth
-hardest structures in the body not considered
part of skeletal system
8
A. Mouth
5. Teeth
-two sets form during development
-primary (deciduous) teeth form and erupt
through the gums, or gingiva, between the ages
of 6 months and 4 years
Enamel
-10 primary teeth in each jaw consist of 2
central incisors, 2 lateral incisors, 2 cuspids
(canines), 2 first molars and 2 second molars,
20 total
Dentin
Crown
Pulp cavity
Gingiva
-permanent teeth begin erupting at age 6 and
finish between ages 17-25 with third molars
(wisdom teeth) impacted wisdom teeth result
when third molars become abnormally wedged, fail
to erupt and are surgically removed
Root
Alveolar process
-each tooth consists of 2 major portions the
crown, which projects above the gum line, and
the root, which is anchored to the alveolar
processes in the mandible and the maxillae
Root canal
Cementum
Periodontal ligament
9
A. Mouth
5. Teeth
a. enamel
-made of calcium salts, hardest substance in the
human body, covers the crown of tooth
-wears away with age and abrasive action or
injury and is not replaced
b. dentin
-bone-like material making up most of the tooth,
lies under enamel and surrounds the pulp cavity
Rx Dental Caries
-cavities holes in the enamel and dentin of a
tooth caused by bacteria
-bacteria metabolize sugars left on teeth to
produce acids, which destroy enamel and dentin
-prevented by regular brushing and flossing,
dental sealants, and fluoride, which is
incorporated into the enamel and makes it
stronger
10
A. Mouth
5. Teeth
c. pulp cavity
-contains the blood vessels and nerves which
supply the tooth in tubular root canals, and the
connective tissue pulp
Rx Gingivitis
-inflammation of the gingiva due to the
accumulation of plaque, a sticky film of
bacteria which produce toxins that damage gum
tissue
-gums become red and swollen and bleed easily
-can be reversed by brushing and flossing
Rx Periodontitis
-gum disease plaque builds up and hardens into
calculus (tartar), gums recede, infection spreads
into bone of alveoloar processes and periodontal
ligament
-teeth become loose and may need to be extracted
-leading cause of tooth loss
11
A. Mouth
5. Teeth
-begin mechanical digestion by breaking food
into smaller pieces to increase surface area to
speed up upcoming enzymatic chemical reactions
Central incisor
a. incisors
-chisel-shaped cutting teeth for biting off
large pieces of food
Lateral incisor
Central incisor
Lateral incisor
Central incisor
Lateral incisor
Central incisor
Lateral incisor
12
A. Mouth
5. Teeth
b. cuspids (canines)
-cone-shaped teeth for grasping and tearing food
Central incisor
Lateral incisor
Cuspid
Cuspid
Central incisor
Lateral incisor
Cuspid
Central incisor
Lateral incisor
Cuspid
Lateral incisor
Central incisor
13
A. Mouth
5. Teeth
c. bicuspids and molars
-teeth with flattened surfaces for grinding food
Central incisor
First premolar (bicuspid)
Lateral incisor
Second premolar (bicuspid)
Cuspid
Second premolar (bicuspid)
Cuspid
Central incisor
Lateral incisor
First molar
Second molar
Third molar
Third molar
Second premolar (bicuspid)
Second molar
First molar
Cuspid
First premolar (bicuspid)
First molar
Central incisor
Lateral incisor
Cuspid
First premolar (bicuspid)
Lateral incisor
Central incisor
14
A. Mouth
6. Salivary glands
-secrete saliva to moisten food particles, bind
them together, and begin the chemical digestion
of carbohydrates
-acts as a solvent to dissolve substances in
food so that they can be tasted
-contains bicarbonate (HCO3-) ions, which buffer
the pH of saliva to keep it neutral and
neutralize the pH of acidic foods to protect
teeth
-serous cells produce watery secretions
containing the enzyme salivary amylase which
splits starch and glycogen into disaccharides
-mucous cells produce mucus to bind and
lubricate food for swallowing
15
A. Mouth
6. Salivary glands
-three pairs of major salivary glands
a. Parotid glands
-largest of the salivary glands
-secrete a watery saliva rich in amylase through
the Stensens duct just opposite the upper
second molar
Parotid gland
Rx Infectious Parotitis
-mumps caused by viral infection of the
parotid salivary glands
Parotid (Stensens) duct
Tongue
-can spread to other ducted glands like the
pancreas or the testicles
Mandible
-vaccinated against with the MMR
16
A. Mouth
6. Salivary glands
a. Submandibular glands
-secrete a saliva that is about half serous and
half mucous through the Whartons duct under
the tongue near the lingual frenulum
Parotid gland
Parotid (Stensens) duct
Tongue
Mandible
Submandibular (Whartons) duct
Submandibular gland
17
A. Mouth
6. Salivary glands
a. Sublingual glands
-secrete a saliva that is mostly mucus through
many small, separate ducts called Rivinuss
ducts
Parotid gland
Parotid (Stensens) duct
Tongue
Mandible
Sublingual gland
Submandibular (Whartons) duct
Submandibular gland
18
B. Pharynx
-throat
1. Nasopharynx
-lies superior to the soft palate
-passageway for air lying between nasal cavity
and oropharyx
-auditory (Eustachian) tube opens through wall
of nasopharynx
Opening of Auditory (Eustachian) tube
Nasopharyx
19
B. Pharynx
2. Oropharynx
-lies inferior to the soft palate and superior
to the epiglottis
-passageway for air lying between the oral
cavity and the larynx passageway for food lying
between oral cavity and laryngopharynx
Opening of Auditory (Eustachian) tube
Nasopharyx
Oropharyx
20
B. Pharynx
3. Laryngopharynx
-lies inferior to the oropharynx from the upper
border of the epiglottis to the lower border of
cricoid cartilage
-passageway for food lying between the
oropharynx and the esophagus
Opening of Auditory (Eustachian) tube
Nasopharyx
Oropharyx
Laryngopharyx
21
Figure 17.14a
B. Pharynx
-swallowing mechanism
1. The tongue forces food into the pharynx.
22
Figure 17.14b
B. Pharynx
-swallowing mechanism
2. The soft palate, hyoid, and larynx are
raised, the tongue is pressed against the
palate, the epiglottis closes, and the inferior
constrictor muscles relax so that the
esophagus opens.
23
Figure 17.14c
B. Pharynx
-swallowing mechanism
3. Superior constrictor muscles contract
and force food into the esophagus.
24
B. Pharynx
-swallowing mechanism
4. Peristaltic waves move food through the
esophagus into the stomach.
25
C. Esophagus
-smooth muscle tube acting as a passageway for
food lying between the laryngopharynx and the
stomach
-passes through the mediastinum between the
lungs and through an opening in the diaphragm
called the esophageal hiatus
-esophageal (cardiac) sphincter normally
constricted to prevent regurgitation of stomach
acid into the esophagus
Esophagus
Esophageal hiatus
Diaphragm
Stomach
26
C. Esophagus
Rx Heartburn
-inflammation of the esophageal mucosa caused by
acid reflux from the stomach into the esophagus
-caused by overeating, eating spicy foods, lying
down right after eating, or eating too quickly
-caffeine stimulates increased acid production
-cigarette smoking and alcohol irritate the
stomach lining and relax the esophageal
sphincter, increasing the likelihood of acid
reflux
-treated with antacids, which buffer acid
2HCl CaCO3 ? CaCl2
H2CO3 ? H2O CO2
HCl NaHCO3 ? NaCl
H2CO3 ? H2O CO2
Rx Hiatal hernia
-protrusion of part of the stomach through the
esophageal hiatus into the thorax
-causes heartburn, difficulty in swallowing,
esophageal ulcer, blood loss, and predisposition
to esophageal cancer
27
D. Stomach
-J-shaped, pouchlike organ with a capacity of
about 1 liter or more
-inner lining marked with thick folds called
rugae, which stretch out flat as stomach is
distended
-food enters the stomach when peristaltic waves
of the esophagus cause the esophageal sphincter
to relax
Esophageal sphincter
-divided into four regions cardiac region,
fundic region, body, and pyloric region
Fundic region
Esophagus
Cardiac region
Body region
Pyloric sphincter
Duodenum
Rugae
Pyloric region
Stomach
28
D. Stomach
-inner lining contains gastric glands, which
produce and secrete gastric juice, a mixture of
hydrochloric acid, mucus, and the enzyme pepsin
-pepsin is activated by hydrochloric acid and
begins the digestion of nearly all types of
dietary protein
-large amounts of alkaline mucus in gastric
juice coat and protect the lining of the stomach
to prevent pepsin from digesting the stomach
itself
While both carbohydrates and proteins have begun
to chemically digest and move through the stomach
quickly, fatty foods may take from 3-6 hours to
move out of the stomach, so after eating fatty
foods it may take longer to feel hungry
-peristaltic waves of contractions mix food with
gastric juice to produce chyme, which is moved
on to the small intestine after about 1 hour on
average
-absorbs water and water-soluble substances,
including alcohol
29
D. Stomach
Rx Peptic ulcers
-gastritis, or inflammation of the lining of the
stomach leading the development of open sores
(ulcers)
-caused by overproduction of hydrochloric acid
brought on by poor diet and stress, treated with
acid- lowering drugs
-many caused by infection of bacteria
Helicobacter pylori, treated with antibiotics
and acid-lowering drugs
E. Pancreas
-has both endocrine (ductless) gland functions
and and exocrine (ducted) gland functions
1. Endocrine functions
-secretes 3 hormones from Islets of Langerhans,
or pancreatic islets, which are groups of cells
clustered around blood vessels lying between
the ducts of the pancreas
30
E. Pancreas
1. Endocrine functions
a. alpha cells
-secrete glucagon, which stimulates the liver to
break down glycogen into glucose
(glycogenolysis), to convert noncarbohydrates
like amino acids into glucose (glyconeogenesis),
and to break down fats into fatty acids and
glycerol
b. beta cells
-secrete insulin, which stimulates the liver to
form glycogen from glucose and inhibits glucose
formation from non- carbohydrates, promotes
facilitated diffusion of glucose into adipose
cells and cardiac and skeletal muscle cells,
promotes transport of amino acids into cells to
increase protein synthesis, and stimulates
adipose cells to synthesize and store fat
31
E. Pancreas
1. Endocrine functions
b. beta cells
Rx Diabetes
Type I
-insulin-dependent diabetes mellitus, also has
been called juvenile onset diabetes, onset is
usually before age 20
-makes up 15 of all diabetes cases
-an autoimmune disease in which a virus attacks
the beta cells of the Islets of Langerhans,
destroying them and halting insulin production
-without insulin, glucose is not taken up by
adipose and muscle cells, glycogen formation is
inhibited, and glucose accumulates in the blood
(hyperglycemia) until excreted by kidneys,
forming new concentration gradient for water,
and water follows glucose into urine, causing
increased frequency of urination and dehydration
and thirst
32
E. Pancreas
1. Endocrine functions
b. beta cells
Rx Diabetes
Type I
-without insulin, protein synthesis decreases and
tissues waste away as cells use protein for
energy
-without insulin, fat is not synthesized or
stored and fatty acids build up in the blood,
along with ketones from fat metabolism, which
are excreted from the kidneys and the lungs as
sodium salts (fruity-smelling breath), causing
acidosis
-left untreated, results in coma and death from
dehydration and acidosis
-treated with daily injections of human insulin
manufactured by genetically-engineered bacteria,
or harvested from the slaughter of cattle or
swine, potential for a patients own stem cells
to be grown in culture and infused into body later
33
E. Pancreas
1. Endocrine functions
b. beta cells
Rx Diabetes
Type II
-noninsulin-dependent diabetes mellitus
-usually begins gradually, in people over age 40
-cells progressively lose insulin receptors and
become less able to respond to normal insulin
levels
-genetic tendency, compounded by a lifestyle of
overeating and underexercising
-endemic in the U.S., second fastest-growing
health risk in America, after obesity
-treated by weight loss and exercise,
modification of diet to avoid foods that
stimulate insulin production (sugars and
starches)
34
E. Pancreas
1. Endocrine functions
b. beta cells
Rx Hypoglycemia
-low blood glucose levels due to overproduction
of insulin
-causes episodes of weakness, shakiness, and
anxiety
-treated by small frequent meals low in
carbohydrates and high in protein
c. delta cells
-secrete somatostatin, which helps regulate
glucose metabolism by inhibiting secretion of
glucagon and insulin
2. Exocrine functions
-secretes pancreatic juice through pancreatic
duct into duodenum of small intestine
35
E. Pancreas
2. Exocrine functions
-pancreatic juice contains pancreatic amylase to
split molecules of starch and glycogen into
disaccharides, pancreatic lipase to break down
triglycerides fatty acids and mono- glycerides,
trypsin, chymotrypsin, and carboxypeptidase to
break down proteins into amino acids, and
nuclease to break down nucleic acids into
nucleotides
Pyloric sphincter
Pancreatic Islets
Pancreas
-pancreatic juice contains high concentrations
of bicarbonate ions to neutralize acidic chyme
arriving from stomach and prevent pepsin from
digesting the duodenal wall
Pancreatic duct
Duodenum
36
E. Pancreas
Rx Cystic fibrosis
-an autosomal recessive disease, most common in
Caucasians
-recessive gene codes for faulty carrier protein
for the chloride ion in certain cells, causing
the chloride ion to be retained in certain
cells, which creates a concentration gradient
that draws water into the cells
-mucus secretions of the lungs and pancreas dry
out and become sticky, plugging up the organs,
encouraging infection, and causing malnutrition
-treated with digestive enzyme supplements
?
If Cybill, who does not have cystic fibrosis but
her father does, and Cyrus, who is heterozygous
for the cystic fibrosis gene, have 7 children,
how many, according to the odds, should have
cystic fibrosis?
C
c
?
Cc
CC
C
1 4
x
7

2
c
cc
Cc
37
F. Liver
-largest internal organ
-helps maintain normal concentration of blood
glucose by responding to glucagon and insulin
-breaks down fats into fatty acids and glycerol,
then oxidizes them to release energy, or
converts one type of fatty acid to another,
synthesizes phospholipids, lipoproteins (fat
transport complexes), and cholesterol
-converts portions of excess carbohydrates and
proteins into fat for storage in adipose tissue
Liver anterior view
Liver inferior view
Quadrate lobe
Inferior vena cava
Gallbladder
Hepatic duct
Right lobe
Left lobe
Right lobe
Cystic duct
Hepatic artery
Left lobe
Hepatic Portal vein
Common bile duct
Caudate lobe
Gallbladder
Inferior vena cava
38
F. Liver
-deaminates amino acids so that they can be used
for energy
H O H I II I
HNCNH
Deamination
To Urine
2
Urea
Glycine
H I HNH
Ammonia
-converts ammonia produced by bacteria in the
intestine to urea, which is excreted as waste in
the urine
-converts one type of amino acid to another
-synthesizes plasma proteins like clotting factors
-stores glycogen, iron, Vitamins A, D, and B12
-liver macrophages phagocytize old or damaged
red and white blood cells
39
F. Liver
The extraordinary ability of the liver to
regenerate following injury or resection has long
fascinated physicians, scientists and lay people.
The earliest allusion to the livers regenerative
capacity is described in Hesiod's Theogony
(750-700 B.C.). Prometheus, a Titan, angered
Zeus by stealing fire and giving it to the
primitive humans. As his punishment, Prometheus
was chained to a rock in the Caucasus Mountains
where Zeus tormented him by sending an eagle each
day to devour his liver. Nightly,his damaged
liver regenerated leaving him fit for the next
days torture. Scientific documentation of the
ability of the human liver to regenerate was not
made until 1890, however. Normally, only
0.01-0.001 of hepatocytes undergo mitosis at any
given time. This low cell turnover in healthy
liver tissue, however, can be altered by toxic
liver injury or surgical resection, which results
in sudden, massive hepatocyte proliferation,
producing recovery of functional liver mass
within two weeks after the loss of up to
two-thirds of the liver. Current thinking
suggests that a special gene or special growth
factors or cytokines trigger regeneration of the
liver.
40
F. Liver
-detoxifies alcohols and formaldehyde to
Hydrogen peroxide
-produces bile, a mixture of water, bile salts,
bile pigments, cholesterol, and electrolytes
-bile pigments include breakdown products of
hemoglobin bilirubin and biliverdin
Rx Jaundice
-yellowish hue of the skin, sclerae (eyeballs),
and mucous membranes due to deposition of bile
pigments
1. Obstructive jaundice
-bile ducts are blocked with gallstones or tumors
2. Hepatocellular jaundice
-the liver architecture is disrupted by the
inflammation due to a Hepatitis infection or the
scarring resulting from cirrhosis
3. Hemolytic jaundice
-red blood cells are destroyed too rapidly
because of a cross-matched blood transfusion or
a blood infection like malaria
41
F. Liver
Rx Hepatitis
-inflammation of the liver due most often to
infection by the hepatitis viruses, but also
alcoholism or autoimmunity
1. Hepatitis A
-most severe form
-early symptoms include mild headache, low
fever, fatigue, lack of appetite, nausea,
vomiting, and stiff joints
-after a week symptoms progress to rash, pain in
upper right quadrant of abdomen, dark foamy
urine, pale feces, swollen axillary lymph nodes,
jaundice
2. Hepatitis B
-sexually transmitted disease, 300 million
carriers worldwide, asymptomatic but can infect
others
-chronic symptoms that can last up to six months
-5 develop liver cancer
3. Hepatitis C
-transmitted mainly by intravenous drug use
-treated with ribavirin, which mimics guanine in
the genetic code
42
F. Liver
Rx Hepatitis
-inflammation of the liver due to infection by
the hepatitis viruses
4. Hepatitis D
-occurs in people already infected with Hepatitis
B
-kills 20 of the people it infects
5. Hepatitis E
-more common in developing nations due to fecal
contamination of drinking water
-affects pregnant women
6. Hepatitis F
-can pass through fecal contamination to other
primates
-causes fulminant hepatitis, which, if left
untreated, causes kidney or liver failure and
coma
7. Hepatitis G
43
Rx Liver Cancer
-cancer of the liver most often got there by
spreading (metastasizing) from somewhere else,
like the lungs
-about 75 of all actual liver cancers are
hepatocellular carcinomas, because most of the
livers cells are hepatocytes
-about twice as common in men that women, and
much more common in the developing countries of
Africa and East Asia, where it often is the most
common type of cancer
-causes about 17,000 deaths each year in the U.S.
Rx Cirrhosis
-disruption of the liver architecture by the
deposition of scar tissue in the liver in its
attempt to wall off and isolate areas of tissue
damaged by infection or toxins
-leads to hardening of liver tissue, interferes
with blood flow and impedes liver functioning
-causes 25,000 deaths annually in the U.S., over
half of which are related to alcoholism
44
G. Gallbladder
-muscular sac which stores bile produced by the
liver
-contracts to inject bile through the cystic
duct, then through the hepatic duct, and finally
the common bile duct into the duodenum
-bile salts break fat globules into droplets by
emulsification, much like a soap does, mixing
the fats with water and increasing the surface
area for lipase to act upon
-bile salts aid in the absorption of fatty
acids, cholesterol, and the fat-soluble vitamins
A, D, E, and K
-bile salts are absorbed along with the fatty
acids into the bloodstream by the small
intestine, where they are returned to the liver
and largely resecreted back into the bile ducts
45
G. Gallbladder
Rx Gallstones
-cholelithiasis
-precipitation and crystallization of cholesterol
from bile due to overproduction of cholesterol,
overabsorption of water from bile, or
inflammation of the gallbladder (cholecystitis)
-gallstones block bile duct, causing obstructive
jaundice and upper right abdominal pain
-often treated with cholecystectomy, or surgical
excision of the gallbladder
H. Small Intestine
-tubular organ extending from the pyloric
sphincter to the large intestine, can be up to
20 feet in length, receives secretions of liver
and pancreas, acts as site of completion of
digestion of all classes of nutrients, absorbs
products of digestion into bloodstream, and
transports waste on to large intestine
46
H. Small Intestine
-consists of three sections the duodenum, the
jejunum, and the ileum
1. Duodenum
-shortest (25 cm), largest in diameter, (5 cm),
and least movable segment
2. Jejunum
-lies between the duodenum and ileum, makes up
the next 40 of length, larger in diameter,
thicker-walled, more vascular, and more active
than the ileum
Duodenum
Stomach
Jejunum
Small Intestine
Ileum
47
H. Small Intestine
3. Ileum
-most distal segment, with more lymph nodules
(Peyers patches) and a higher bacterial
population
4. Mesentery
-double-layered fold of peritoneum which houses
nerves, blood vessels, and lymphatic vessels
which supply intestine, and from which the
jejunum and the ileum are suspended
Duodenum
Stomach
Jejunum
Mesentery
Small Intestine
Ileum
48
H. Small Intestine
-lined on the inside with intestinal villi,
which are especially numerous in the duodenum
and the proximal jejunum, and increase the
surface area for absorption
Intestinal Villus
-blood capillaries and lacteals (lymphatic
capillary) carry away nutrients
-intestinal glands (Crypts of Lieberkühn)
secrete a watery fluid which is absorbed by the
villi, along with digestive products
-digestive enzymes embedded in the cell
membranes of the intestinal mucosa break down
food molecules just before absorption
peptidases break down peptides into amino acids,
sucrase, maltase, and lactase break down the
disaccharides sucrose, maltose, and lactose into
monosaccharides glucose, fructose, and galactose
49
H. Small Intestine
Rx Lactose Intolerance
-many adults do not produce enough lactase to
digest dairy products
-undigested lactose increases osmotic pressure
of the intestinal contents and draws water into
the intestines, resulting in diarrhea
-intestinal bacteria digest lactose, producing
acids and gas which result in intestinal
cramping and bloating
-adults treated with lactase pills before eating
dairy, infants drink soy-based formula
-genetic evidence suggests that lactose
intolerance in adults is normal, and the ability
to digest dairy as adults is a mutation which
occurred only in recent genetic history that
persisted as agriculture introduced dairy
products into the human diet in the past 10,000
years
50
H. Small Intestine
-intestinal lipase breaks down fats into fatty
acids and glycerol
5. Digestion in the Small Intestine
a. disaccharides
-from carbohydrate digestion
Hydrolysis
b. peptides
-from protein digestion
Hydrolysis
51
H. Small Intestine
5. Digestion in the Small Intestine
b. peptides
-break down into amino acids
Dipeptide
Hydrolysis

Amino acid
Amino acid
52
H. Small Intestine
5. Digestion in the Small Intestine
b. peptides
Cysteine
Phenylalanine
Amino acid
53
H. Small Intestine
5. Digestion in the Small Intestine
c. fats
-break down into fatty acids and glycerol
Hydrolysis
54
H. Small Intestine
5. Digestion in the Small Intestine
c. fats
Triglyceride (fat)
Fatty acids
55
H. Small Intestine
-finally, electrolytes like sodium, potassium,
chloride, nitrate, bicarbonate, calcium,
magnesium, and sulfate ions are absorbed through
intestinal villi, and water follows
Rx Diarrhea
-an increased volume and wateriness of feces and
an increased frequency of bowel movements due to
irritation of the lining of the intestine
1. Secretory diarrhea
-bacterial or viral toxins interfere with active
transport of electrolyte ions into cells
resulting in loss of electrolytes, creating
hypertonic conditions in the lumen of the
intestine, and water follows
-symptom of intestinal flu or cholera
2. Invasive diarrhea
-bacterial or viral toxins destroy intestinal
mucosa and blood vessels lining intestine,
resulting in water and electrolyte loss and
blood loss
-symptom of typhoid fever or salmonella
56
H. Small Intestine
Rx Diarrhea
-symptom of disease responsible for more deaths
that any other symptom
-leads to death from hypotension and circulatory
shock leading to anoxia of the brain
-treated with rehydration, electrolyte
replacement, and antibiotics in the case of
bacterial infection
6. Greater omentum
-double fold of peritoneal membrane which drapes
like an apron over the intestines
Liver
-fat clinging to omentum cushions intestines
against blunt trauma
Stomach
Gallbladder
-in the case of infections of the alimentary
canal wall, the omentum adheres to the site of
inflammation to prevent spread of infection into
the peritoneal cavity (appendicitis)
Transverse colon
Greater omentum
57
I. Large Intestine
-larger in diameter than small intestine, about
5 feet long
-reabsorbs water left over from digestion, along
with any dissolved electrolytes, forms and
stores feces, acts as the main site for enteric
digestion
Ileum
-food enters from small intestine through the
ileocecal sphincter, which normally remains
constricted, but opens in response to increased
peristalsis of the ileum after a meal
Ileocecal sphincter
Cecum
1. Cecum
-pouch at the beginning of the large intestine
Vermiform appendix
2. Vermiform appendix
-vestigial cecum, the main site of enteric
digestion in other animals like horses and pigs
-performs no useful function, but contains
lymphatic tissue which make it a target for
infection, like the tonsils
58
I. Large Intestine
2. Vermiform appendix
Rx Appendicitis
-inflammation of the appendix usually caused by
a bacterial infection
-treated with antibiotics or appendectomy, risk
of appendix bursting and creating massive
infection of the peritoneum called peritonitis
Transverse colon
3. Colon
-divided into ascending, transverse,
descending, and sigmoid colons
Descending colon
Ascending colon
Sigmoid colon
Rectum
59
I. Large Intestine
4. Rectum
-as walls become distended with feces, triggers
defecation reflex in descending colon and the
internal anal sphincter to relax
Rx Hemorrhoids
-inflammation caused by prolonged pressure on
branches of the rectal vein
-pressure due to pregnancy, obesity,
constipation, diarrhea, and liver disease
-itching, sharp pain, and sometimes bleeding,
veins may bulge out of anus when distended
-may require surgery to correct
5. Anus
-inferior external opening of alimentary canal
-constricted by the internal anal sphincter,
which is made of smooth muscle and under
involuntary control, and the external anal
sphincter, which is made of skeletal muscle and
under voluntary control
60
I. Large Intestine
-secretes an alkaline mucus to bind feces
together, protect the intestinal wall against
abrasion, and neutralize acids produces by
bacteria
-absorbs about 90 of the water entering in chyme
Rx Constipation
-condition of feces becoming overly dehydrated,
making defecation difficult
-more common in the aged, whose peristaltic
contractions become weaker with age and whose
mucus secretions decrease with age
61
I. Large Intestine
-home to intestinal flora, which break down
cellulose (fiber) as an energy source and
synthesize Vitamin K, B12, thiamine, and
riboflavin
-bacterial species include Escherichia coli,and
Clostridium difficile,and yeast species Candida
albicans
Rx Yeast infection
-overpopulation of yeast in colon increase
likelihood of yeast causing opportunistic
infection outside of colon, especially as yeast
are easily transferred mechanically from anus to
vagina
-common in women, and children still in diapers
-due to diet poor in fiber and rich in sugar,
which suppresses bacterial flora while
triggering growth of yeast population, or
overuse of antibiotics, which suppresses helpful
bacterial population, eliminating competition
for resources for yeast
62
I. Large Intestine
Rx Inflammatory Bowel Disease
-ulcerative colitis and Crohn disease
-inflammation and ulceration of the lining of
the intestine
-cramps, bloody diarrhea, weight loss,
electrolyte imbalance, and predisposition to
colon cancer
-cause unknown, suspected to be due to genetic
predisposition, bacterial infection, or
autoimmunity
Rx Colorectal Cancer
-fourth most common cancer in the U.S. and
second-most common cause of cancer death
causing 56,000 death each year in the U.S.
-symptom include change in frequency or
consistency of bowel movements, blood in feces,
abdominal pain, weight loss, fatigue, vomiting
-treated by surgical excision, possible colostomy
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