The Digestive System

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The Digestive System

• Made up of two separate groups
• The Alimentary Canal
• Accessory Organs

Performs 6 basic processes
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6 Functions of the Digestive System

• Ingestion- taking in food and liquids
• Secretion- water, acid, buffers and enzymes added
  to system
• Mixing and Propulsion
• Digestion- chemical and physical
• Absorption- nutrients delivered to blood
• Defecation-elimination of waste

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Digestion

• Mechanical- Teeth, tongue and cheeks cut and
  grind food into smaller portions before
  swallowing and the stomach and sm intestine churn
  the food
• Chemical- Digestive enzymes and acids break large
  molecules like carbohydrates into simpler sugars

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Alimentary CanalGI Tract

• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine

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Mouth

• Mechanical and chemical digestion both occur in
  the mouth. The teeth and salivary glands combine
  to begin the digestive processes.
• Swallowing- (deglutition) is the process of
  moving food into the pharynx and esophagus.

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Pharynx

• During swallowing, the epiglottis closes off the
  respiratory passage.
• The soft palate and uvula close off the
  nasopharynx
• The food bolus will spend less than 2 seconds in
  the pharynx

Sorry, I have a frog in my Throat.
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Esophagus

• A muscular, collapsible tube about 10 inches
  long.
• Transports food to the stomach
• No digestion occurs here
• Peristalsis consists of progressive, wavelike
  contractions

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Stomach

• A mixing chamber and holding reservoir.
• Some mechanical digestion as the food is churned
  and mixed.
• Chemical digestion occurs through the action of
  gastric juice
• Food is now called Chyme
• Chyme will spend approx. 4 hours in the stomach.

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Stomach

• Have 2 sphincters
• Lower esophageal
• Pyloric
• 3 layers of muscles
• Longitudinal
• Circular
• Oblilque
• 4 Regions
• Cardia
• Fundus
• Body
• Pylorus

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Gastric Juice Contains

• Pepsin- which breaks down proteins
• Gastric lipase- acts on fats
• Hydrochloric acid- kills microbes and assists in
  other chemical digestion
• Mucus- protects stomach wall

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Small Intestine

• Most digestion and absorption occurs in the small
  intestine
• Its length of 10 feet allows time for nutrients
  to be properly absorbed
• Diameter of about 1 inch
• Internally, the intestine is lined with folds,
  villi and microvilli to further support
  absorption.

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Small Intestine

• Divided into 3 regions
• Duodenum (10 inches)
• Receives chemicals from pancreas, liver and
  gallbladder
• Jejunum (3 feet)
• Ileum (6 feet)

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Villi in the Small Intestine

• Work to increase the surface area of so more
  substances can be absorbed.

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Villi in the Small Intestine
Contain Blood vessels and Lymphatic vessels to
absorb nutrients.
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Large Intestine

• 5 Feet long, and 2.5 inches in diameter
• Functions
• Completion of absorption
• Production of certain vitamins
• Formation of feces
• Expulsion of feces from body

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Regions of the Large Intestine

• Cecum
• Colon
• Rectum
• Anal canal

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Cecum

• The Cecum is a large pouch-like sac.
• A sphincter acts as a doorway between the small
  intestine and cecum.
• The appendix hangs off the cecum, it is about 3
  inches long and its function is a mystery.

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The Colon

• The walls of the colon are much more muscular
  than those of the small intestine.
• The Colon is divided into the following regions
• Ascending
• Transverse
• Descending
• Sigmoid

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Accessory Organs
These organs assist in the process of digestion,
but do not come in direct contact with food.
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Accessory Organs Include

• Salivary Glands-
• 3 major pairs Parotid, Submandibular and
  Sublingual
• Water helps to lubricate dry foods
• Salivary amylase begins working on starches

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Accessory Organs Include

• Teeth- cut tear and pulverize food
• Adults have 32
• Classified as
• Molars
• Incisors
• Canine
• Tongue- swallowing, maneuvers food
• Contains taste buds

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Pancreas

• Found just under the stomach
• Delivers pancreatic juice thru a duct into the
  duodenum
• Pancreatic juice buffers the acid in gastric juice

Enzymes work on proteins, fats and nucleic acids.
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Liver

• The second largest organ in the body.
• In addition to many complex functions, the liver
  creates bile.
• Bile breaks down fats thru emulsification.

The liver also removes toxic substances from the
blood and stores nutrients for a more even
release into the blood stream.
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Gallbladder

• The gallbladder stores the bile made by the
  liver.
• It senses when fats are present in the duodenum
  and then squirts bile when needed thru ducts.

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Common Disorders of the Digestive System

• Ulcers- created when acid production overwhelms
  mucus in the stomach and the stomach lining is
  damaged
• Gallstones- occur when bile stored in gallbladder
  crystallizes to form stones.
• Appendicitis- occurs when the appendix gets
  twisted, cutting off its blood supply. Infection
  and sepsis can result.
• Heartburn- occurs when stomach acid leaks back up
  into the esophagus

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Food- 6 types

• Carbohydrates- (starches) broken into simple
  sugars
• Proteins-broken down into amino acids
• Fats- triglycerides and lipids
• Water-directly absorbed
• Vitamins-directly absorbed
• Nucleotides-broken into components

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Chemical Digestion

• Mouth- Saliva
• Salivary amylase- starch
• Lingual lipase- triglycerides
• Stomach-Gastric Juice
• Pepsin-proteins
• HCL-bacteria
• Gastric lipase- triglycerides

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Chemical Digestion

• Pancreas
• Pancreatic amylase- starches
• Trypsin-proteins
• Pancreatic lipase- triglycerides
• Liver/Gallbladder
• Bile- emulsification of lipids
• Small Intestine
• Sugars to simple sugars
• Dipeptides to amino acids
• Nucleotides to simpler components