Digestive (GI) System (Gastrointestinal System) Gastro = stomach

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Digestive (GI) System (Gastrointestinal
System)Gastro stomach
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Functions

• INGESTION Taking food in by mouth
• DIGESTION to break food down into simple
  molecules
• Mechanical churning of food in the stomach,
  manipulation of food with tongue, tearing and
  grinding with teeth.
• Chemical breakdown of food with hydrochloric
  acid
• ABSORPTION nutrients enter capillaries
• DEFECATION to eliminate solid waste products

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Digestive Organs
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Regional Terms

• Upper GI
• Stomach and areas superior
• Lower GI
• Areas inferior to the stomach

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Abdominal Quadrants
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Peritoneum and Mesenteries
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Peritoneum and Mesenteries
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OMENTA

• The liver is suspended by a mesentery called the
  OMENTUM.
• There are two omenta greater and lesser.
• GREATER OMENTUM is flat, and is in front of the
  intestines like an apron. Its function is to
  store fat.
• LESSER OMENTUM is smaller. It is just some fat
  above the stomach.

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Mesenteries
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PERITONEAL CAVITY

• Why is this important? The peritoneum divides
  the abdominal cavity into three distinct regions
• PERITONEAL CAVITY digestive organs are here
• INFRAPERITONEAL CAVITY (inferior to peritoneum)
  where the bladder is
• RETROPERITONEAL CAVITY (posterior to it) where
  the kidneys are

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PERITONEAL CAVITY

• This is clinically important because if you tear
  something in the GI tract (ruptured appendix),
  bacteria go out into the peritoneal cavity,
  affects all the organs there, which is the entire
  GI tract.
• Bleeding in the kidney will accumulate in the
  retroperitoneal cavity.
• Infection in the urinary bladder doesnt affect
  the peritoneal cavity.
• Bleeding and infection are confined to one
  compartment.

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Mouth

• Oral Cavity
• Hard and Soft Palate
• Tongue
• Lingual Frenulum
• Salivary Glands
• Parotid, Submandibular, Sublingual
• Teeth

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ORAL CAVITY

• Lined by non-keratinized stratified squamous
  epithelium. The transition between the skin
  (keratinized) and the non-keratinized area is the
  LIPS. You can see what happens when the lips dry
  out becomes cracked because the lips dont have
  as much keratin as the skin.
• PALATE (ROOF of mouth)
• HARD PALATE bone
• SOFT PALATE soft tissue (can feel with tongue on
  roof)

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Mouth
Figure 22.8a
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TONGUE

• Your tongue is the only muscle in your body that
  is attached at only one end.
• The tongue is all muscle, but it is different
  than all other muscles of the body, where the
  fascicles are arranged in a particular order.
• The fibers of the tongue go in all directions,
  and have no fascicles ? good ROM.
• Some people can curl tongue, others cant.
• The LINGUAL FRENULUM is the flap of skin under
  the tongue at the midline. If it is too short,
  it limits mobility, called tongue-tied.
  Treatment is to cut it.

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Figure 22.8b
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Salivary Glands
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SALIVARY GLANDS

• Produce saliva
• Names of some salivary glands
• Parotid (largest). Mumps is a virus that attacks
  here.
• Submandibular
• Sublingual
• Functions of saliva
• To moisten food so you can swallow, especially
  dry food like crackers.
• Saliva is made of mucus and water. The mucus in
  the saliva is what moistens the food.
• To inhibit growth of bacteria (which like dark,
  warm, moist areas). What does this are the
  antibodies, enzymes, and macrophages in the
  saliva.

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Saliva

• Saliva is not used for digestion of food. There
  is an enzyme in saliva that breaks down starch,
  but it takes hours. It is used to break down
  food stuck between the teeth so the bacteria
  cant eat it and cause cavities.
• Saliva contains bactericidal enzymes that
  initiate the digestion of carbohydrates, and
  bicarbonate buffer. However, it does not contain
  enzymes that begin the digestion of proteins
  chemical digestion begins in the stomach.

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TEETH

• How many teeth does the average adult have? 32
• How many DECIDUOUS TEETH (baby teeth that fall
  out)? 20
• How many INCISORS (most anterior)? 8 for cutting
  like scissors
• How many CANINES? 4 for tearing
• How many PRE-MOLARS(BICUSPIDS 2 roots)? 8For
  chewing, some tearing
• How many MOLARS (TRICUSPIDS 3 roots)? They are
  the most posterior 12 For chewing, some
  tearing. The 4 most posterior ones are called
  WISDOM TEETH, which erupt at age 20, but
  sometimes grow crooked, called impacted

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STRUCTURE OF TOOTH

• GINGIVA are the gums
• CROWN is the area above the gingiva
• ROOT is embedded in a socket in the bone. In the
  maxilla, the root can extend into the maxillary
  sinus. Damage to the sinus can be a lot of
  problems.
• ENAMEL is the external layer of the tooth. It is
  stronger than bone, but does wear out. It is
  suppose to be ivory color, not white. Whitening
  procedures scrape away outer oxidized layer, to
  expose the layer underneath, which is white, but
  it will oxidize, too.
• DENTIN is deep to the enamel. It is like bone,
  with living tissues and cells.
• PULP CAVITY with PULP is deep to the dentin. It
  has blood vessels and nerves.
• PERIODONTAL LIGAMENT attaches the tooth to the
  bone. Its like periosteum. Disease of this
  structure is the most common cause of tooth loss
  in adults.

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Tooth Structure
Figure 22.11
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Tooth Problems

• When bacteria eat away at the enamel, whats it
  called? CARY (CAVITY)
• The dentist removes a larger area than where the
  bacteria destroyed, and fills it in.
• If the cavity extends into the pulp cavity, there
  is no way to clean it up. The treatment is to
  make a big hole, scrape out the pulp, and fill up
  the whole thing ROOT CANAL. This is a dead
  tooth, but still there.
• Bacteria between the gingiva and tooth causes
  inflammation of the gingiva GINGIVITIS.
• When it gets worse, the gingiva pulls away from
  the tooth and the bacteria extends down to the
  periodontal ligament PERIODONTITIS. This is
  the major cause of tooth loss. The tooth loosens
  and falls out. Thats why you need to floss.

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Cavity (called a cary)
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Plaque on Tooth
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X-ray of Teeth
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X-ray of Teeth
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Fun Facts

• The enamel in your teeth is the hardest substance
  in your body.
• Your teeth start growing 6 months before you are
  born.
• If you are right handed, you will tend to chew
  your food on the right side of your mouth. If you
  are left handed, you will tend to chew your food
  on the left side of your mouth.

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Fun Facts

• Termites chew up dirt and dung and make massive
  homes. If they were the size of a human, they
  could make a home taller than the Empire State
  Building. They also put in air conditioning
  systems, covered walkways, stairs and gardens.
• Every person has a unique tongue print.
• A giraffes tongue is 22 inches long
• What animal bite causes the most human deaths?
  Snakes take their toll, but Mosquitoes cause
  millions of deaths a year. The Komodo dragon has
  saliva so toxic with bacteria, it just bites it's
  prey and waits for it to die of infection a few
  days later.
• The average human produces enough spit to fill
  two swimming pools in their lifetime.

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VIDEOS

• How Dentures are made VIDEO

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GI Tract

• This is a tube through the body, forming the
  esophagus, stomach, small and large intestine.
  The GI tract functions to digest and absorb.
• Esophagus
• Stomach
• Small Intestine
• Large Intestine

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NOTE

• When you are referring to a structure that has a
  cavity (stomach, esophagus, uterus, eye, etc),
  the layer that touches the lumen is considered
  the superficial layer, even though from the
  outside of the body it would be considered
  deeper.

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Layers of GI Tube

• There are four layers
• 1. MUCOSA (inner layer). The lining varies from
  region to region.
• Epithelium
• Lamina Propria Loose connective tissue
• Muscularis mucosae very thin smooth muscle,
  causes little twitches within the mucosa.
• 2. SUBMUCOSA (moderate dense connective tissue).
  Lots of elastic fibers, blood vessels, and
  lymphatic vessels.
• 3. MUSCULARIS EXTERNA (smooth muscle layer with
  two parts
• Circular Layer (inner)
• Longitudinal layer (outer)
• 4. Serosa

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Serosa
Mucosa
Muscularis Externa
Submucosa
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3. Muscularis Externa

• Muscularis Externa is extremely important for
  digestion.
• It allows for 2 types of actions
• a. PERISTALSIS a rhythmic contraction to
  push something along. This pushes food down by
  smooth muscle contraction.
• b. SEGMENTATION A back-and-forth squeezing
  of the muscle to grind up food. Food moves
  forward then backward a little, then forward
  again. Function is to churn up the food inside.
  
• Some areas have thicker smooth muscle
  SPHINCTER. Circular muscles open and closes an
  opening.
• Controls the flow of food from one region to
  another.

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Layers of GI Tube

• 4. SEROSA is not in all regions (none in
  esophagus).
• Simple squamous epithelium
• Loose connective tissue
• From internal to external, the layers of this
  tube are the mucosa, submucosa, muscularis,
  serosa.

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Esophagus

• Extends from the oropharynx (back of the throat)
  to the stomach, about 25 cm long. The things
  that are specialized in the esophagus are
• 1. MUCOSAL EPITHELIUM (non-keratinized
  stratified squamous epithelium).
• Why do we want stratified squamous here?
  Because that is the thickest type of epithelium.
  It protects against things you swallow pointy
  potato chips, etc. Cuboidal would slough.
• 2. MUSCULARIS EXTERNUM in upper half skeletal
  muscle, is under voluntary control. Lower half
  smooth muscle, not voluntary. Food gets caught
  in the lower half because it hasnt started
  peristalsis.

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Cardiac Sphincter

• The esophagus goes through the thoracic cavity.
• It needs to go through the diaphragms opening
  (esophageal hiatus).
• It empties to the stomach through a CARDIAC
  SPHINCTER a thickening of the muscularis
  externa. This is NOT A TRUE SPHINCTER.

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Stomach Anatomy
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Stomach Functions

• Store Food
• Mechanically churns food into a paste called
  CHYME
• Kill bacteria
• Some digestion of proteins
• Some absorption of water, alcohol
• Gastric emptying is the release of food from the
  stomach into the duodenum the process is tightly
  controlled with liquids being emptied much more
  quickly than solids.

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STOMACH FUNCTIONS

• 1. Store Food, so it can be slowly released into
  a small intestine. Your whole Thanksgiving
  dinner can take your stomach diameter from 2 to
  8 diameter.
• 2. Mechanically Churns food. Secretions from
  the stomach are added, turns everything into a
  gooey paste. When you throw up, you can see the
  enzyme secretions CHYME.
• 3. Kill bacteria. The stomach is very acidic
  (pH 1) like battery acid. Chyme will even eat
  through clothing.
• 4. Some digestion of proteins.
• 5. Some absorption of water, alcohol (alcohol
  is absorbed in the mouth, too!)
• Food takes four hours to completely leave the
  stomach.

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FUN FACTSBody measurements for food portions

• 1 oz a handful
• 3 oz palm size (meat)
• cup fist
• teaspoon tip of thumb

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REGIONS OF THE STOMACH

• 1. Cardiac region (near heart)
• 2. Fundus (above the cardiac sphincter)
• 3. Body
• 4. Pyloric region
• 5. PYLORIC SPHINCTER (a true sphincter)
• The lining of the stomach is folded over into
  RUGAE, to allow for expansion of the stomach.
• When the stomach is full, the rugae flatten
  out.

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The Stomach
Figure 22.14a
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The Stomach
Figure 22.14b
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HISTOLOGY OF THE STOMACH

• Epithelium simple columnar epithelium.
• Its function is for secretion and absorption.
• Lamina Propria contains gastric pits.

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The Stomach
Figure 22.15a-c
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Stomach Cells

• CHIEF CELLS secrete an enzyme called pepsinogen.
  When pepsinogen is exposed to hydrochloric acid
  (HCl), it is cleaved into pepsin, its active
  form. Pepsin digests proteins.
• PARIETAL CELLS in the stomach secrete
  hydrochloric acid.
• They also secrete intrinsic factor, which is
  needed to absorb vitamin B12, which is needed to
  make red blood cells.

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Intrinsic Factor

• A person who lacks intrinsic factor (such as
  those who have a stomach stapling procedure or
  gastric bypass) will not be able to absorb
  vitamin B12 and they will get a type of anemia
  called pernicious anemia.
• Treatment is injectable B12 shots monthly for the
  rest of their lives. They also have a new
  dissolvable oral form of vitamin B12 that enters
  the bloodstream directly from the mouth.

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Gastric gland
Figure 22.15a-c
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PARTICULARS OF STOMACH

• Has a third layer of the muscularis externum an
  OBLIQUE LAYER to churn food.

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The Stomach
Figure 22.14b
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Problems with the stomach

• There are lots of goblet cells in the stomach
  which make mucus to prevent the stomach from
  digesting itself. Bacterial infection can erode
  this area GASTRIC (or Peptic) ULCER.
• Acid Reflux
• The acid in your stomach is strong enough to
  dissolve razor blades. The acid can creep up the
  esophagus and erode the lining there, causing
  heartburn.
• The acid can stay in the stomach and cause an
  ulcer. In severe cases, the ulcers are so deep,
  they bleed, and the person might even vomit
  blood.
• Tends to occur more when a person is under a lot
  of stress because more acid is produced.

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Two major causes of Peptic (stomach and
duodenum) Ulcers

• 1) 60 of gastric and up to 90 of duodenal
  ulcers are due to a bacterium called Helicobacter
  pylori.
• The body responds by increasing gastrin
  secretion, which is a hormone that causes HCl to
  be secreted, which erodes the stomach lining.
• 2) NSAIDs (non-steroidal anti-inflammatory drugs,
  such as aspirin) block prostaglandin synthesis.
• Prostaglandins promote the inflammatory reaction.
  They also are found in the stomach, protecting it
  from erosion.

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Stomach (gastric) ulcer
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Risk and Transmission

• The lifetime risk for developing a peptic ulcer
  is approximately 10.
• In Western countries the prevalence of
  Helicobacter pylori infections roughly matches
  age (i.e., 20 at age 20, 30 at age 30, 80 at
  age 80 etc.).
• Prevalence is higher in third world countries.
• Transmission is by food, contaminated
  groundwater, and through human saliva (such as
  from kissing or sharing toothbrushes or food
  utensils)

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Problems With the Stomach

• The cardiac sphincter doesnt close well, since
  it is not a true sphincter consequences
• You can throw up (reverse peristalsis). Rats do
  have a true cardiac sphincter, and cant vomit!
• Thats why rat poison wont kill people or dogs
  they can throw it up.
• Another consequence hiatal hernia.

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HIATAL HERNIA

• Part of the stomach, protrudes through esophageal
  hiatus, causing pain and difficulty swallowing.
• It is the most common of all hernias.
• There is a great amount of acid reflux erodes
  walls of esophagus, causing ulcerations of
  esophagus.
• Treatment is surgical pull down the stomach, and
  tighten the hernia in a laparoscopic procedure.

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Fun Fact

• Astronauts can't belch - there is no gravity to
  separate liquid from gas in their stomachs.

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SMALL INTESTINE (Small bowels)

• These are the longest part of the GI tract (9-15
  feet long, 1 diameter)
• In a cadaver, they are even longer, because the
  muscles relax.
• The small intestine is the most important region
  of the GI tract because almost all of the
  digestion and absorption takes place here.

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Small Intestine Structure

• The small intestine needs a lot of surface area
  200 square meters, which is the floor space of a
  typical house.
• How do you get such a lot of surface area?
• There are lots of folds called PLICAE CIRCULARIS.
  
• Each of these folds also has folds, called VILLI.
  If you take velvet and fold it, the fold is the
  plicae, and the velvet hairs are villi.
• Each of the villi has epithelial cells called
  MICROVILLI, which make a BRUSH BORDER.

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The Small Intestine
Crypt of Lieberkuhn
Figure 22.17a-c
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Small Intestine Regions

• Duodenum 12 finger widths long
• Jejunum hungry when empty
• Ileum twisted

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DUODENUM

• This is the shortest region, only one foot long.
  
• It receives chyme from the stomach. This is where
  digestion begins. There are two ducts at the
  beginning of the duodenum from the pancreas and
  gallbladder. It is the site of action of liver
  and pancreas secretions.

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The Duodenum
Figure 22.16
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Pancreas

• PANCREAS is an endocrine gland, and also
  participates in digestion (exocrine). Most of
  the digestive enzymes are made here. They go out
  the PANCREATIC DUCT to enter the small intestine.
  
• It also produces BICARBONATE (from a hormone
  called SECRETIN) to increase the pH (decrease the
  acidity) of the chyme coming from the stomach.
  If there is too much acid there, get a DUODENAL
  ULCER.

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PANCREAS

• ACINAR CELLS secretes digestive enzymes
• ISLETS OF LANGERHANS secretes insulin

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Pancreas Histology
Figure 22.25a
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Pancreas
Acinar cells (secrete enzymes)
Islet of Langerhans (secretes insulin)
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Gall Bladder

• GALL BLADDER stores and concentrates bile, which
  emulsifies fat It breaks down the fat into
  microscopic droplets which can be broken down by
  pancreatic enzymes.
• Fat doesnt dissolve in water, so when you go to
  McDonalds and order the Big Mac, fries, and
  shake, you get 200 grams of fat (one week
  supply), which globs together in the intestine,
  and that much more bile is needed to break it
  down.

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What Ronald McDonald is doing to your arteries
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GALL BLADDER

• This is located inferior to the liver, and its
  function is to store and concentrate bile.
• Bile is a detergent/soap (not an enzyme) which
  emulsifies fat It breaks down the fat into
  microscopic droplets which can be broken down by
  pancreatic enzymes.
• It does NOT make or secrete bile that is done by
  the liver.
• Bile is made in the liver from Hemoglobin (Hgb),
  and also contains cholesterol and other things.
• The function of bile is to break down lipids
  (fats) so they can be digested.

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Gallbladder and Pancreas
Figure 22.16
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Gall Bladder

• As the liver produces bile, if there is no food
  in the duodenum, the sphincter closes and bile
  backs up into the gall bladder. When there is
  food, the sphincter releases the bile.
• The gall bladder is similar to the stomach. It
  is lined with RUGAE (allows organ expansion).
  Has muscles around it to push bile out.

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Gall Stones

• One function of the gall bladder is to
  concentrate the BILE, but if the bile salts
  crystallize, GALL STONES can form.
• The stones block the cystic duct, and causes a
  lot of pain as the bile backs up.
• Treatment is to cut the cystic duct and remove
  the gall bladder.
• Now that person can only eat small amounts of
  fats at a time.

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Types of Gall Stones

• Stones made out of cholesterol (most common
  type). It has nothing to do with the cholesterol
  levels in the blood.
• Stones made from too much bilirubin in the bile.
• Gallstones are more common in women, Native
  Americans and other ethnic groups, and people
  over age 40. Gallstones may also run in families.

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Jejunum

• JEJUNUM (empty)
• This is the part of the small intestine where
  most absorption occurs.
• It is 3 feet long.

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Ileum

• ILEUM (twisted) is 5-10 feet long. It is the
  terminal portion of the small intestine.
• The rest of the absorption takes place here.

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Histology of Small Intestine

• The intestines are lined with simple columnar
  epithelium with lots of goblet cells that make
  mucus for protection.
• However, the pancreatic enzymes can digest the
  mucus and the epithelial cells, so the lining of
  the small intestine is replaced every day.
• The basic functions of this epithelium are
  secretion and absorption.
• Absorption is a digestive process in which
  nutrients enter the capillaries.

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Crypt of Lieberkuhn

• The INTESTINAL CRYPT (CRYPT OF LIEBERKUHN) is
  where the new epithelial cells come from, and
  they are pushed upwards into the villi to replace
  the digested cells.
• Also in this crypt are cells that produce enzymes
  and hormones.

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Crypt of Lieberkuhn
Lacteal
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Crypt of Lieberkuhn
Figure 22.17a-c
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Absorption in Small Intestine

• In the villis is a fenestrated capillary bed (has
  holes in the walls of the blood vessels), which
  needs to absorb a lot of material.
• The small intestine absorbs carbohydrates, fats,
  and proteins (although protein enzymes have
  already begun working earlier in the digestive
  tract in the stomach).

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Intestinal Villi
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Lymphatics of Small Intestine

• There are also large lymphatic capillaries in
  each villis called LACTEALS, whose function is to
  absorb breakdown products of fat. The vessel is
  large so it wont get clogged up.
• Under all this are the MUSCULARIS MUCOSA muscles
  which can twitch to move the villa so food does
  not get stuck.

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Inguinal Hernia

• The inguinal canal is open in the male to allow
  for passage of the spermatic cord. In the female,
  the area is closed, but weak.
• When there is abdominal pressure (lifting a
  weight), a piece of small intestine can push out
  of this canal, causing pain.
• Symptoms and warning signs
• http//www.symptomfind.com/diseases-conditions/her
  nia-symptoms-warning-signs/

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Problem with Small Intestine

• Crohns Disease
• Autoimmune disease of the GI tract
• Most common area affected is small intestine
• Inflammation causes pain and diarrhea (may be
  bloody)
• Genetic cause (high risk if siblings have it)
• Usually occurs in males in their 20s
• No cure just treatment of symptoms

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Celiac disease (Sprue gluten intolerance)

• Genetic autoimmune disorder of the small
  intestine, causing chronic diarrhea. The person
  is allergic to gluten. Causes destruction of
  microvilli and villi.
• It is characterized by having pale, loose and
  greasy stools (steatorrhoea) which are voluminous
  and malodorous.
• It often presents with abdominal pain and
  cramping, abdominal distension, and sometimes
  mouth ulcers.
• Without adjusting the diet, coeliac disease leads
  to an increased risk of adenocarcinoma (small
  intestine cancer).

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Celiac disease (Sprue gluten intolerance)

• They may develop ulcerative jejunitis and
  stricturing (narrowing as a result of scarring
  with obstruction of the bowel).
• The changes in the bowel make it less able to
  absorb carbohydrates, fats, minerals (calcium and
  iron), and the fat-soluble vitamins A, D, E, and
  K.
• Anemia may develop in several ways iron
  malabsorption may cause iron deficiency anemia,
  and folic acid and vitamin B12 malabsorption may
  give rise to megaloblastic anemia.
• Calcium and vitamin D malabsorption may cause
  osteopenia (decreased mineral content of the
  bone) or osteoporosis (bone weakening and risk of
  fragility fractures).
• A small proportion have abnormal coagulation due
  to vitamin K deficiency and are slightly at risk
  for abnormal bleeding.
• Coeliac disease is also associated with bacterial
  overgrowth of the small intestine, which can
  worsen malabsorption or cause malabsorption
  despite adherence to treatment.

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Celiac disease (Sprue gluten intolerance)

• Celiac disease is caused by an allergy to gluten.
• Gluten is present in Wheat subspecies (such as
  spelt, semolina and durum) and related species
  such as barley, rye, triticale and Kamut. A small
  minority of coeliac patients also react to oats.
  It is most probable that oats produce symptoms
  due to cross contamination with other grains in
  the fields or in the distribution channels.
  Generally, oats are therefore not recommended.
• Other cereals such as maize (corn), millet,
  sorghum, teff, rice, and wild rice are safe for
  patients to consume, as well as non cereals such
  as amaranth, quinoa or buckwheat. Non-cereal
  carbohydrate-rich foods such as potatoes and
  bananas do not contain gluten and do not trigger
  symptoms.

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Gluten-free diet

• Gluten is used in foods in some unexpected ways,
  for example as a stabilizing agent or thickener
  in products like ice-cream and ketchup.
• People wishing to follow a completely gluten free
  diet must also take into consideration the
  ingredients of any over-the-counter or
  prescription medications and vitamins. Also,
  cosmetics such as lipstick, lip balms, and lip
  gloss may contain gluten and need to be
  investigated before use. Glues used on envelopes
  may also contain gluten.
• Most products manufactured for Passover are
  gluten free. Exceptions are foods that list
  matzah as an ingredient, usually in the form of
  cake meal.
• A blood test for IgA antiendomysial antibodies
  can detect coeliac disease.

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Large Intestine (Colon, or large bowel)

• This is about 5 feet long, diameter of 4.
• Absorbs a LOT of water
• Absorbs salts and electrolytes (Na, K, etc)
• Stores feces for defecation (terminal portion)
• Contains abundant bacteria (E. coli)
• Make vitamins (B5, K, biotin)
• Allow material to move through large intestine
  easier
• Keep out harmful bacteria
• They eat things you cant digest
• Fiber
• Some sugars that we dont have enzymes for

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Intestinal Gas

• When these bacteria are happy and dividing, they
  produce gas. If you are lactose intolerant, your
  are missing the enzyme for lactose so the
  bacteria gets more sugar and you get more gas!
  Beans also have these sugars, so they give you
  gas.
• Mexico has different strains of E. coli in their
  water the two strains battle it out and you get
  diarrhea.
• Diarrhea is when the large intestine does not
  absorb water ? dehydration and electrolyte
  imbalance.
• Cholera is a disease which attacks the large
  intestine, preventing water absorption, and can
  be fatal in 24-48 hours.
• The difference between diarrhea and constipation
  is the amount of water absorbed from the large
  intestine.

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He also has FUNNY greeting cards and BEAUTIFUL
paintings for sale as well. You can also get
reprints suitable for framing, or originals. Here
is more info about his work and a YOUTUBE
video. https//nccnews.expressions.syr.edu/?p1151
5
101
Regions of the Large Intestine

• Cecum
• Ascending colon
• Transverse colon
• Descending colon
• Sigmoid colon
• Rectum
• Anus

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Large Intestine
Figure 22.18a
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Gross Anatomy of the Large Intestine

• The large intestine is divided into regions, but
  they function the same.
• The ileum enters into the first region of the
  large intestine called the CECUM.
• The ileo-cecal valve separates these and controls
  the amount of chyme that enters into the large
  intestine.
• It also prevents the E. coli from leaving the
  large intestine and getting into the small
  intestine, where they would cause disease.

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Appendix

• Below the cecum is the APPENDIX, which is a lymph
  node, but it contains E. coli as well.
• It might become inflamed, which closes off the
  opening APPENDICITIS
• This is dangerous because It can rupture. Need
  antibiotics and surgery or can be fatal.
• Most common age for this is late teens to early
  20s because a child has a larger opening which
  shrinks with age. When youre done growing, its
  done shrinking, so if you havent had a problem
  by then, you might be ok.

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Large Intestine

• Up from the cecum is the ASCENDING COLON,
  TRANSVERSE COLON, and DESCENDING COLON.
• Then there is an S shaped section called the
  SIGMOID COLON, which leads to the RECTUM, and out
  the ANUS.

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SIGMOID COLON

• This area allows for the passage of gas without
  passage of feces. The LEVATOR ANI MUSCLE, when
  relaxed, allows only gas to pas. When contracted,
  the feces can pass.
• Therefore, this muscle controls defecation by
  lifting the anal canal superiorly around the
  feces.
• Another thing that controls defecation is the
  INTERNAL and EXTERNAL ANAL SPHINCTER. The
  internal one is smooth muscle, and the external
  is skeletal muscle (voluntary control).
• The smooth muscles which line the large intestine
  work in coordinated fashion to move the feces
  out.
• It takes about 24 hours for food to be processed
  through the entire digestive tract.

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Sigmoid Colon
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Problems with Large Intestine

• DIVERTICULITITS
• INFLAMMATORY BOWEL DISEASE
• Crohns Disease
• Ulcerative colitis
• IRRITABLE BOWEL SYNDROME
• COLON CANCER
• HEMORRHOIDS

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DIVERTICULITITS

• DIVERTICULUM (singular) DIVERTICUA (plural) can
  form, which are small pouches in the large
  intestine.
• They can become inflamed, usually from a small,
  hard piece of feces, causes the condition known
  as DIVERTICULITITS.
• These are painful and often need to be surgically
  removed.
• May be caused by lack of fiber, causing increased
  pressure in the colon.

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Inflammatory Bowel Disease (IBD)

• IBD is a group of inflammatory conditions of the
  colon and small intestine.
• The major types of IBD are Crohn's disease and
  ulcerative colitis

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Ulcerative Colitis

• The main symptom is constant diarrhea mixed with
  blood, of gradual onset.
• An intermittent disease, with periods of
  exacerbated symptoms, and periods that are
  relatively symptom-free
• No known cause, but may be genetic
• May be triggered by environmental factors
• Dietary modification may reduce the discomfort
• It is treated as though it were an autoimmune
  disease (anti-inflammatory drugs,
  immunosuppression)
• Colectomy (partial or total removal of the large
  bowel through surgery) is occasionally necessary,
  and is considered to be a cure for the disease.

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Ulcerative Colitis
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IRRITABLE BOWEL SYNDROME (IBS)

• IBS is a diagnosis of exclusion.
• Symptoms are chronic abdominal pain, bloating,
  and alteration of bowel habits in the absence of
  any detectable organic cause.
• May manifest as diarrhea or constipation or may
  alternate between the two.
• May be caused by infection, stress, or onset of
  maturity
• No cure treatments attempt to relieve symptoms,
  including dietary adjustments, medication and
  psychological interventions.

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COLON CANCER

• This is the 1 most deadly cancer (kills more
  people) because it metastasizes and there are no
  symptoms. It can be suspected by seeing blood in
  the stool this is an easy test, but not very
  accurate.
• A more accurate test is a SIGMOIDOSCOPY. A tube
  is inserted into the sigmoid colon, done in the
  doctors office. The tube has a light, and they
  look for growths on the walls of the intestine
  POLYPS, which are pre-cancerous growths.
• A COLONOSCOPY is done under general anesthesia
  since the tube has to go through the entire
  colon, but its more effective.

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Colonoscopy Photos
Ileo-cecal valve
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HEMORRHOIDS

• HEMORRHOIDS are varicose veins in the rectum.
• There are large veins along the rectum, with
  nothing constricting them.
• They are common in pregnant women and in fighter
  pilots from the g-forces they pull.
• They can be surgically removed.

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FUN FACTS ABOUT THE RECTUM

• A healthy individual releases 3.5 oz. of gas in a
  single flatulent emission, or about 17 oz. in a
  day.
•  The bombardier beetle combines chemicals in his
  rear end and can squirt out boiling hot acidic
  liquid which quickly neutralizes any attack.
• All land spiders breathe through a hole on the
  rear part of their bodies.
• The Fitzroy river turtle absorbs two-thirds of
  the oxygen it needs through its rectum.

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FUN FACTS

• HOW LONG DOES IT TAKE TO DIGEST A MEAL? Should be
  about one day.
• Because plant cells are made of cellulose and we
  cannot digest that, you can swallow a few kernels
  of corn (whole, without chewing), and youll be
  able to easily see them in your stools and find
  out how long it takes to go all the way through
  your digestive tract.

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Hepatic Portal System

• Almost all of the blood coming from the digestive
  system drains into a special venous circulation
  called the portal circulation.
• This is because it contains all the nutrients and
  toxins that have been absorbed along the
  digestive tract from ingested food.
• Before these absorbed substances can go into the
  systemic circulation (the main blood circulation
  in the body), it must be filtered first to remove
  or detoxify toxic substances first.
• This filtering and detoxification is one of the
  500 functions of the liver.

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Hepatic Portal System

• Many drugs that are absorbed through the GI tract
  are substantially metabolized by the liver before
  reaching general circulation. As a consequence,
  certain drugs can only be taken via certain
  routes.
• For example, nitroglycerin cannot be swallowed
  because the liver would inactivate the
  medication, but it can be taken under the tongue
  or transdermal (through the skin) and thus is
  absorbed in a way that bypasses the portal venous
  system.

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• A portal system is one that has two separate
  capillary beds between the arterial supply and
  the final venous drainage.

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LIVER

• This is the largest internal organ of the body,
  located on the right side, below the diaphragm,
  and extends below the costal margin (can
  palpate).
• It has many functions and is the most complex
  organ except the brain.
• The liver has 500 known functions.

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Liver

• Makes blood clotting factors
• Makes blood proteins (albumin)
• Makes bile
• Regulates glucose levels
• Processes fats
• Makes cholesterol
• Processes amino acids
• Detoxifies chemicals

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Liver

• It is also the only organ that can regenerate.
• As much as 80 of your liver could be cut away
  and it would grow back to a full size in
  approximately three months.
• With only 1/6th of your liver present your body
  could continue to function.
• It is usually hard to determine if the liver is
  damaged until the damage is quite advanced.

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Liver

• It has a right and left lobe, separated by the
  FALCIFORM LIGAMENT.
• The liver gets blood from 2 sources
• Artery Hepatic artery
• Vein Hepatic portal system Blood from the
  spleen, stomach, pancreas, small and large
  intestines which all go through the liver. The
  nutrients that are absorbed by the GI tract go to
  the liver first for processing, then to the rest
  of the body.

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Liver
Figure 22.22
129
INTERNAL STRUCTURE OF LIVER

• The liver is made of hundreds of thousands of
  LIVER LOBULES each one is the size of a sesame
  seed, giving the liver a grainy texture when you
  eat it.
• Each lobule carries out all of the functions of
  the liver.

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LIVER LOBULE

• It has a hexagonal shape, at each corner are some
  vessels HEPATIC TRIAD
• ARTERIOLE from the hepatic artery
• VENUOLE from the hepatic portal vein
• BILE DUCT, which goes to the gall bladder.

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(Kupffer cells)
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Liver
Hepatic Triad Vein, Artery, Bile Duct

Figure 22.23a, c, d
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Liver Lobules
134
Liver Central vein and sinusoids
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Sinusoids

• LIVER SINUSOIDS are channels that blood can flow
  through. Cells that line the sinusoids are called
  HEPATOCYTES, and each one faces the sinusoid and
  is in contact with blood.
• The hepatocytes are what carry out all of the
  functions of the liver.
• If you made a machine to do the work of the
  liver, it would have to be the size of a large
  oil refinery.

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Liver sinusoids and hepatocytes
137
Function of Hepatocytes

• Detoxification of poisons
• Picking up and processing of nutrients from the
  portal blood
• This includes picking up glucose from the
  nutrient-rich blood coming from the small
  intestine and stores it as glycogen (the storage
  form of glucose) for when the body needs it
  later.
• Storage of the fat soluble vitamins

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Kupffer Cells

• Within the sinusoids are KUPFFER CELLS, which are
  macrophages. As blood flows through the
  sinusoids, they phagocytize old erythrocytes.
  The released Hgb is given to the hepatocytes,
  which convert it to bilirubin, one of the main
  components of BILE.
• Bile flows through a series of channels called
  the BILE CANNICULI to the bile duct.

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The Liver Destroys Old Red Blood Cells

• By the way, when you have dark circles under your
  eyes, it is from hemoglobin and iron deposits
  from broken RBCs that leaked out of the delicate
  capillaries under the thin skin there.
• Will skin creams remove this?

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Problems with the Liver

• HEPATITIS
• CIRRHOSIS
• JAUNDICE

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Liver Problems

• Infection of the liver HEPATITIS (can be
  deadly)
• CIRRHOSIS is when the hepatocytes die and are
  replaced by connective tissue. This is often
  from alcoholism, which kills the hepatocytes.

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Jaundice

• One of the symptoms from any liver disorder is a
  connection of the bile canaliculi and the
  sinusoid so some bilirubin can enter the blood.
• Bilirubin is yellow-green (later in its
  degradation it will turn brown and that is what
  gives the feces its color).
• The yellow color of bilirubin in the skin is
  known as JAUNDICE.

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Jaundice

• Jaundice is not a disease it is a symptom of
  liver disorder.
• It first shows up in the sclera because it is
  white there. The skin has other pigments, so
  yellow doesnt show up as well.
• Newborns get jaundice from a lot of erythrocytes
  being broken down, and the liver gets overloaded,
  but its harmless.
• The treatment is UV light or sunlight, goes away
  in a few days.

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Liver Transplant

• Adult-to-adult liver transplantation has been
  done using the donor's right hepatic lobe which
  amounts to 60 of the liver.
• Due to the ability of the liver to regenerate,
  both the donor and recipient end up with normal
  liver function if all goes well.

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Situs Inversus

• Congenital condition in which the major visceral
  organs in the thorax and abdomen are reversed or
  mirrored from their normal positions.
• The heart is located on the right side of the
  thorax, the stomach and spleen on the right side
  of the abdomen and the liver and gall bladder on
  the left side.
• The left lung is trilobed and the right lung
  bilobed, and blood vessels, nerves, lymphatics
  and the intestines are also transposed.
• Situs inversus is generally an autosomal
  recessive genetic condition, although it can be
  X-linked or found in identical "mirror" twins.

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Situs Inversus

• As long as there are no heart defects, the person
  has no health issues.
• However, donating an organ is more complicated,
  since the connecting blood vessels are not in the
  same place!
• People are not aware of their condition until an
  unrelated health issue arises, such as
  appendicitis, presenting on the left side instead
  of the right side. The doctor cannot find the
  heart sounds in the proper location, either.

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40 lb Abdominal Tumor
152
Warning!

• The Government has issued a health warning not to
  swallow chewing gum. The following is a photo of
  what can happen

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