The Digestive System

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The Digestive System
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Digestion

• Processing of food
• Types
• Mechanical (physical)
• Chew
• Tear
• Grind
• Mash
• Mix
• Chemical
• Catabolic reactions
• Enzymatic hydrolysis
• Carbohydrate
• Protein
• Lipid

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Digestion

• Phases
• Ingestion
• Movement
• Digestion
• Absorption
• Further digestion

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Digestive System Organization

• Gastrointestinal (Gl) tract (Alimentary canal)
• Tube within a tube
• Direct link/path between organs
• Structures
• Mouth
• Oral Cavity
• Pharynx
• Esophagus
• Stomach
• Duedenum
• Jejenum
• Ileum
• Cecum
• Ascending colon
• Transverse colon

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Digestive System Organization

• Descending colon
• Sigmoid colon
• Rectum
• Anus
• Accessory structures
• Not in tube path
• Organs
• Teeth
• Tongue
• Salivary glands
• Liver
• Gall bladder
• Pancreas

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Anatomy of the Mouth and Throat
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Human Deciduous and Permanent Teeth

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Dorsal Surface of the Tongue
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The Major Salivary Glands
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Deglutition (swallowing)

• Sequence
• Voluntary stage
• Push food to back of mouth
• Pharyngeal stage
• Raise
• Soft palate
• Larynx hyoid
• Tongue to soft palate
• Esophageal stage
• Contract pharyngeal muscles
• Open esophagus
• Start peristalsis

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Deglutition (swallowing)

• Control
• Nerves
• Glossopharyngeal
• Vagus
• Accessory
• Brain stem
• Deglutition center
• Medulla oblongata
• Pons
• Disorders
• Dysphagia (difficulty swallowing)
• Aphagia (inability to swallow may be
  psychological or physical)

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Esophagus

• Usually collapsed (closed)
• Functions
• Secrete mucous
• Transport food

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Peristalsis and Segmentation
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Esophagus

• Sphincters
• Upper
• Lower
• Abnormalities
• Achalasia- difficulty swallowing, backflow
• Atresia- esophagus does not connect to stomach
  properly
• Hernia
• Barrets esophagus- lining damaged by stomach
  acid
• Esophageal varices- bleeding in esophagus

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Stomach

• Usually J shaped
• Left side, anterior to the spleen
• Mucous membrane
• G cells make gastrin
• Goblet cells make mucous
• Gastric pit Oxyntic gland Parietal cells
  Make HCl
• Chief cells Zymogenic cells
• Pepsin
• Gastric lipase

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Anatomy of the Stomach
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Stomach

• 3 muscle layers
• Oblique
• Circular
• Longitudinal
• Regions
• Cardiac sphincter
• Fundus
• Antrum (pylorus)
• Pyloric sphincter
• Vascular
• Inner surface thrown into folds Rugae
• Contains enzymes that work best at pH 1-2

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Stomach

• Functions
• Mix food
• Reservoir
• Start digestion of
• Protein
• Nucleic acids
• Fats
• Activates some enzymes
• Destroy some bacteria

• Absorbs
• Alcohol
• Water
• Lipophilic acid
• B 12

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Small Intestine

• Extends from pyloric sphincter ? ileocecal valve
• Regions
• Duodenum
• Jejenum
• Ileum
• Movements
• Segmentation
• Peristalsis

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Small Intestine

• Chemical digestion of nutrients and absorption of
  nutrients is completed in the small intestines
• Three divisions of the small intestines
• Duodenum first portion of the small intestine
  where the majority of chemical digestion occurs.
• Jejunum middle portion of the small intestine
  where the majority of absorption of nutrients
  occurs.
• Ileum final portion of the small intestine
  where absorption occurs.

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Large Intestines

• The large intestines are the last part of the
  digestive system.
• Absorption of water, vitamins, electrolytes,
  production of vitamin K, and formation of feces
  occurs in the large intestines
• Ascending, Transverse, Descending, Sigmoid colons

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Anatomy of the Large Intestine
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Large Intestine

• Functions
• Mechanical digestion
• Haustral churning
• Peristalsis
• Reflexes
• Gastroileal
• Gastrocolic
• Chemical digestion Bacterial digestion
• Ferment carbohydrates
• Protein/amino acid breakdown

• Absorbs
• More water
• Vitamins
• B
• K
• Concentrate/eliminate wastes

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Feces Formation and Defecation

• Chyme dehydrated to form feces
• Feces composition
• Water
• Inorganic salts
• Epithelial cells
• Bacteria
• Byproducts of digestion
• Defecation
• Peristalsis pushes feces into rectum
• Rectal walls stretch

• Control
• Parasympathetic
• Voluntary

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Rectum

• The last portion of the large intestine which
  functions as a temporary storage of solid wastes
  before excretion

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Anus

• The final portion of the rectum where solid waste
  is excreted from the body

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Liver

• Location
• R. Hypochondrium
• Epigastric region
• Functions
• Makes bile
• Detergent emulsifies fats

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Liver

• Detoxifies/removes
• Drugs
• Alcohol
• Stores
• Glycogen
• Vitamins (A, D, E, K)
• Fe and other minerals
• Cholesterol
• Activates vitamin D
• Fetal RBC production
• Metabolizes absorbed food molecules
• Carbohydrates
• Proteins
• Lipids

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Liver

• Dual blood supply
• Hepatic portal vein
• Direct input from small intestine
• Hepatic artery/vein
• Direct links to heart

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The Duodenum and Related Organs
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The Organs and Positions in the Abdominal Cavity
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Diseases and Disorders of the Digestive System
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Colon Cancer

• Most of the cancers of the large intestine are
  believed to have developed from polyps (benign
  tumors).
• Cancer of the colon and rectum, also called
  colorectal cancer can invade and damage adjacent
  tissues and organs.
• Symptoms include fatigue, weakness, shortness of
  breath, change in bowel habits including diarrhea
  or constipation, red or dark blood in stool,
  weight loss, abdominal pain, cramps, or bloating.
  
• Surgery is the most common treatment for colon
  cancer.
• Quick Write Who is more likely to get colon
  cancer, men or women?

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From Donna Myers, former About.com
GuideUpdated July 8, 2007About.com Health's
Disease and Condition content is reviewed by the
Medical Review Board

• Research has shown that in general, men are more
  likely to have colon polyps and colon tumors than
  women.
• Female smokers were more likely to get colorectal
  cancer than male smokers. So, all other things
  being equal, if a man and a woman smoke, the
  woman is more likely to get colorectal cancer.
• Men tend to get rectal cancer and left-sided
  colon cancers more often than women, and women
  tend to get right-sided colon cancer more often
  than men.

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Chrons Disease

• Chrons disease is an ongoing disorder that
  causes inflammation of the digestive tract.
• The disease can affect any area of the GI tract,
  from the mouth to the anus, but it most commonly
  affects the lower part of the small intestine,
  the ileum.
• The swelling extends deep into the lining of the
  affected organ.
• The swelling can cause pain and can make the
  intestines empty frequently, resulting in
  diarrhea.
• Chrons disease may be caused by an abnormally
  functioning immune system.
• Treatment includes prescription medications,
  nutritional supplements, surgery, or a
  combination of these.
• There is no cure.

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from ehealthmd.com/chrons disease

• Compromised nutrition, even malnutrition, is a
  constant threat to an individual with Crohn's
  disease. This is because the disease creates a
  vicious cycle
• Fever and diarrhea cause a loss of appetite.
• Fever, by raising the body's metabolic rate, adds
  to the need for caloric energy.
• Diarrhea can lead to dehydration and temporary
  lactose intolerance (the inability to digest milk
  sugars).
• Lactose intolerance causes milk sugars to ferment
  in the colon, leading to cramps and more
  diarrhea.
• Lactose intolerance can also indirectly lead to
  calcium deficiency, which in turn can lead to the
  loss of bone density called osteoporosis. This
  side effect can be especially prevalent among
  those being treated with corticosteroids such as
  prednisone.

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Celiac Disease

• Celiac disease is a digestive disease that
  damages the small intestine and interferes with
  absorption of nutrients from food.
• People who have celiac disease cannot tolerate a
  protein called gluten, found in wheat, rye, and
  barley.
• When people with celiac disease eat foods or use
  products that contain gluten, their immune system
  responds by damaging the small intestine.
• Celiac disease is an autoimmune disease that is
  genetic.
• The most common symptoms include pain in the
  digestive system or other parts of the body.
• The only know treatment is a gluten-free diet.

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Appendicitis

• Appendicitis, inflammation of the appendix, is
  the most common surgical disease.
• It results from the obstruction of the opening to
  the appendix by a mass, structure or infection.
• Symptoms of appendicitis include generalized
  abdominal pain, pain localized in the lower right
  abdomen, nausea, vomiting, possibly fever, and an
  elevated white blood cell count.
• Treatment involves the removal of the appendix
  and antibiotics.

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Hernia

• hernias occur when a part of the intestine
  protrudes through a weak point or tear in the
  abdominal wall.
• This protrusion creates a bulge which can be
  painful.
• Some hernias occur at birth when the abdominal
  lining does not close properly.
• Other hernias occur later in life when muscles
  weaken or deteriorate.
• The most common treatment is surgery.