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• AKA- The Gastrointestinal Tract, GI, or Gut!
• Includes the mouth, esophagus, stomach, and small and large intestines, and anus.
• An adults DT is about 30 feet long.

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• The accessory digestive glands produce a variety of secretions that contribute to the breakdown of foodstuffs.

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The digestive tract can be viewed as a “disassembly line” in which food becomes less complex at each step of processing and nutrients then become available to the body.
The six essential activities are:
1.
Ingestion
2.
Propulsion
3.
Mechanical digestion
4.
Chemical digestion
5.
Absorption
6.
Defecation

 Mucous membrane,(aka mucosa), lines most of the alimentary canal from mouth to anus.
 Formed of surface epithelium and a small amount of smooth muscle
 Functions include:
 Protection against infectious disease.
 Secretion of mucus, digestive enzymes, and hormones
 Absorption of end products of digestion into the blood.

 Digestion is the mechanical and chemical breakdown of foods into forms that cell membranes can absorb.
 Mechanical digestion breaks large pieces into smaller ones without altering their chemical composition
 Chemical digestion breaks food into simpler chemicals

 Mouth- a mucosa-lined cavity, is also called the oral cavity, or buccal cavity.
 The mouth receives food and begins digestion by mechanically breaking up the solid particles into smaller pieces. This is called mastication.
 The mouth is also part of the speech and sensory perception.
 The mouth is in all responsible for the following
 To ingest
 Begins mechanical digestion by chewing
 Initiates propulsion by swallowing.

 Tongue- mixes saliva with food and moves it toward pharynx.
 The surface of the tongue has rough projections called papillae. These can provide friction which handles food most other papillae contain most of the taste buds.
 The tongue is connected in the midline to the floor of the mouth by a membranous fold called the frenulum.
 The root of the tongue is anchored to the hyoid bone.

 All Tonsils are lymphatic tissue and are there for associated with fighting infection.
 Alingual Tonsils, Palatine Tonsils, and
Pharyngeal Tonsils- (aka Adenoids).
 We will discuss these in more detail during the Lymphatic System.

 The palate forms the roof of the oral cavity and consists of a hard anterior part and a soft posterior part.
 The soft palate forms a muscular arch, which extends posteriorly and downward as a cone-shaped projection called the uvula.

o
o Cleanses the mouth o Dissolves food chemicals so that they can be tasted o Moistens food and aids in compacting it into a bolus (which is a lump of chewed food) o Contains enzymes that begin the chemical breakdown of starchy foods.

o There are three pairs of major salivary glands: o Parotid (1) is the largest o Submandibular (2) o Sublingual (3) (is the smallest)

o Salivary Glands produce two types of secretory cells: mucous and serous.
o The parotid glands contains only serous cells.
o The sublingual gland contains mostly mucous cells o The submandibular contains both cells
 Serous Cells – they produce a digestive enzyme called amylase.
It begins the chemical digestion of complex carbohydrates , such as sweet potatoes even before it leaves the mouth.
 Mucous Cells- produce mucus which binds food particles and acts as a lubricant.

 Mumps, a common children’s disease, is an inflammation of the parotid glands caused by the mumps virus.
 Saliva is mostly 97 to 99.5% water.

 Teeth- 20 primary,
32 secondary, hardest structures in the body that are not part of the skeletal system
 By age 2..most children have ALL of the primary teeth.

PHARYNX
 Swallowing (deglutition), moves food into the throat or pharynx .
 A passage way for both food and air.
 It connects the nasal and oral cavities with the larynx (where your vocal cords are) and esophagus.
 Over 22 muscles groups must work together during the process of swallowing in order to close of the air passageway and lead food down the esophagus.
 A flexible flap of tissue called epiglottis reflexively closes over the trachea when we swallow to prevent choking.

Esophagus
 ESOPHAGUS is a straight collapsible tube about 25 centimeters long.
 Provides passageway for food from the pharynx to the stomach
 Waves of muscle contractions called
Peristalsis forces food down the esophagus.

Esophagus
 At the end of the esophagus, a muscular ring called the lower esophageal sphincter (aka cardiac sphincter) allows food to enter the stomach and then squeezes shut to keep food or fluid from flowing back up into the esophagus.

Heartburn
 Heartburn is the burning, radiating substernal pain that occurs when the acidic gastric juice regurgitates into the esophagus.
 Common in one who has eaten or drunk to excess, extreme obesity, pregnancy, and running which cause stomach contents to splash upward with each step.

STOMACH
 Stomach- is a temporary storage tank.
 It lies in the upper left quadrant of the peritoneal cavity, nearly hidden by the liver and the diaphragm.
 Though relatively fixed at both ends the stomach is quite movable. Running horizontal in short people and vertical in tall people.

STOMACH
 The stomach is a j-shaped, pouchlike about 25-30 cm.

STOMACH
 StomachThe stomach is a saclike organ.
 It has walls made of layers of muscle, each arranged on a different angle.
 As the food enters the stomach, muscle contractions begin to twist, turn, and churn the food.
 The twisting, turning, and churning of food in the stomach is part of mechanical digestion.

STOMACH
 The stomach produces gastric juice and mixes it with the food. This gastric juice contains
Pepsin which is an important enzymes that begin the digestion of proteins.
 Proteins are the only substances digested in the stomach. Proteins are even then only partially digested in the stomach.
 The food is churned and mixed with stomach fluids until a thick paste called chyme is produced.
 The chyme passes through the stomach into the small intestine

STOMACH
 Glands in the stomach produces about
2.8 liters of gastric juices daily.
 Pepsin is by far the most important digestive juice, it begins the digestion of nearly all types of dietary protein.

STOMACH
 When empty has the volume of 1/5 of a cup, but it can expand to hold 8 cups of food after a large meal.

 A ring of muscle the pyloric sphincter located between the stomach and the duodenum of the small intestines controls food entry.
 It leaves the stomach and enters the small intestines through peristaltic waves.

 As the peristalis muscles contraction move your meal along its digestive path, these contractions also help churn food, liquid and different digestive juices together, rendering them into a gooey mix known as chyme.
 Stomach growling is the result of this process. Moving with those solid and liquid chyme ingredients are gasses and air . As all these ingredients get pushed around and broken down into easy-to-absorb bits, pockets of air and gas also get squeezed and create the noises we hear.

Small Intestines
 Small intestinereceives secretions from the pancreas and liver completes digestion of nutrients, absorbs the products of digestion, and transports the residues to the large intestines.
 Tubular organ with many loops and coils that fills much of abdominal cavity
 5.5-6.0 meters long and 5 cm in diameter

Small Intestines
 Small Intestines is made up of 3 key parts
 The duodenum- The C-shaped first part
 The jejunum- the coiled midsection
 The ileum- the final section that leads to the large intestines.

Small Intestines
 The jejunum and ileum are suspended from the posterior abdominal wall by a double-layered fold of peritoneum called the
Mesentery. The mesentery supports the blood vessels, nerves, and lymphatic vessels that supply the intestinal wall.

Small Intestines
 A filmy, double fold of peritoneal membrane called the Greater
Omentum drapes like an apron from the stomach over the transverse colon and the folds of the small intestine.

Small Intestines
 The inner wall of the small intestines is covered with millions of microscopic, fingerlike projections called villi. Nutrients can be absorbed into the body through this villi.

ABSORPTION OF THE SMALL
INTESTINE
 Most absorbing organ in the alimentary canal
 Its so effective that only very little amounts water and electrolytes reach the large intestine
 Enzymes from the intestinal mucous membrane and the pancreas break down and absorb carbohydrates, proteins, and fat molecules
 Intestinal villi, projections of mucosa, absorb water and electrolytes

Small Intestines
 The Ileocecal sphincter joins the small intestine’s ileum to the large intestine’s cecum.
 Normally remains closed, however eating a meal elicits a gastroileal reflex that increases peristalsis in the ileum and relaxes the sphincter, forcing the contents of the small intestine into the cecum.


Large Intestines
 1.5 meters long vs/ the small intestines which is 6 meters long.
 It is located in the lower abdominal region, posterior to the stomach…
 It begins on the lower right side of the abdominal cavity…crosses obliquely to the left and then descends into the pelvis



Large Intestines
 By the time the food reaches the large intestines most of the work of absorbing nutrients is nearly finished.
 The large intestine’s main function is to remove water from the undigested matter and form solid waste that can be excreted
 Bacteria in the colon help to digest the remaining food particles.

Large Intestines
 Large intestineconsist of the cecum, the colon, the rectum, and the anal canal.
 Cecum - a pouch at the beginning of the large intestine that joins that small intestine to the large intestines.
 The colon is divided into four portions…the ascending, transverse, descending and sigmoid.

Large Intestines
 The colon extends from the cecum up the right side of the abdomen
(ascending), across the upper abdomen (transverse), and then down the left side of the abdomen
(descending), then it makes an Sshaped curve called the (sigmoid) finally connecting to the rectum.

Large Intestines
 The rectum is where feces are stored until they leave the digestive system.
 The anal canal connects the rectum to the anus.
 The anal canal opens to the outside as the anus.
 Guarded by two sphincters. Internal anal sphincter
(involuntary controlled) External anal sphincter
(voluntarily controlled)

ABSORPTION OF THE LARGE
INTESTINE
 The large intestine has very little digestive function
 It absorbs the left over water and electrolytes
 90% of the water that enters the large intestine is absorbed so that very little sodium and water is loss

Large Intestines

Appendix
 The appendix- a small hollow, fingerlike pouch.
 Hangs at the end of the cecum.
 Scientist think it is left over from a previous time in human evolution…it is no longer necessary to the DT

ESSENTIAL ORGANS THAT ARE NOT
PART OF THE DT
 The Liver (located under the rib cage in the right upper part of the abdomen).
 The Gallbladder (hidden just below the liver)
 The pancreas (beneath the stomach).
 These are NOT part of the alimentary canal, but these are essential to digestion.

Liver
 Liver- largest internal organ
 Shaped like a wedge
 Lies almost entirely within the rib cage.
 Has 4 lobes
 Is a very vital organ with many important roles. Its digestive function is to produce bile for export to the duodenum.

Liver
 Bile- is a fat emulsifier, it breaks up fats into tiny particles so that they are more accessible to digestive enzymes.

Gallbladder
 The gallbladder is a thin-walled green muscular sac about 10 cm (4 inches) long.
 It stores bile that is not immediately needed.
 Bile is often 10 times more concentrated when it leaves the gallbladder than when it entered.
 These enzymes and bile travel through special channels called the bile ducts which lead directly into the duodenum of the small intestine.

Pancreas
 Pancreas is a soft tad-pole shaped gland.
 It is an endocrine gland but also plays a role in digestion.
 It secretes a digestive juice called pancreatic juice
 Produces enzymes that help digest proteins, fats, and carbs.
 Also makes a substance that neutralizes stomach acid.

Pancreas
 The cells that produce pancreatic juices release them into the pancreatic duct that extends the length of the pancreas and joins with the bile ducts from the liver and gallbladder and empty into the duodenum of small intestines.

MAJOR MINERALS
 Calcium- helps in the structure of bones, essential for nerve impulse conduction, muscle fiber contraction, and blood coagulation, increases permeability of cell membranes and activates certain enzymes.
 Calcium is found in milk, cheese, leafy green products.
 An excess can cause kidney stones.
 Not enough calcium can cause stunted growth, misshapen bones, and fragile bones.

MAJOR MINERALS
 Phosphorus- helps in structures of bones and teeth, component in nearly all metabolic reactions, constituent of nucleic acids, many proteins, some enzymes and some vitamins, it also occurs in the cell membrane,
ATP, and phosphates of body fluids.
 Phosphorus is found in meats, cheese, nuts, whole grain cereals, milk, legumes
 Not enough phosphorus can cause stunted growth

MAJOR MINERALS
 Potassium- helps maintain intracellular osmotic pressure and regulate pH; promotes metabolism; needed for nerve impulse conduction and muscle fiber contraction.
 Potassium is found in avocados, dried apricots, meats, nuts, potatoes, and bananas.
 A lack of potassium can cause muscular weakness, cardiac abnormalities, and edema.

MAJOR MINERALS
 Sulfur- essential part of various amino acids, thiamine, insulin, biotin, and mucopolysaccharides.
 Water soluble sulfur is an oil in it's pure water soluble form, it is the flexible bond that holds your cells together making your skin look good without wrinkles.
 Sulfur is found in meats, milk, eggs, legumes
 A deficiency of water soluble sulfur can lead to a variety of conditions ranging from skin irritations and rashes to total breakdown of cellular regeneration.
 For instance have you ever wondered why your pets like to go out and chew on the grass, or scratch consistently yet don't have fleas, these are signs that your pets are deficient in water soluble sulfur. The consistent scratching is an attempt to relieve the pain caused by a loss of nutritional sulfur which provided the flexible bond in the skin tissue and has now resulted in dry, brittle skin.

MAJOR MINERALS
 Sodium- helps maintain osmotic pressure of extracellular fluids and regulate water movement; needed for conduction of nerve impulses and contraction of muscle fibers; aids in regulation of pH and in transport of substances across cell membrane
 Sodium is found in table salt, cured ham, sauerkraut, cheese, graham crackers.
 An excess of sodium can cause hypertension and edema.
 A lack of sodium can cause nausea, muscle cramps, and convulsions.

MAJOR MINERALS
 Chlorine – maintain osmotic pressure of extracellular fluids, regulate pH, and maintain electrolyte balance
 Chlorine can be obtained in table salt, cured ham, sauerkraut, cheese, graham crackers
 Too much chlorine causes vomiting
 A deficiency of it causes muscles cramps

MAJOR MINERALS
 Magnesium – is needed in metabolic processes (ATP production in mitochondria)
 If you consume too much magnesium it will cause diarrhea
 Found in dairy products, legumes, nuts, leafy green vegetables
 A lack of it will cause neuromuscular disturbances

VITAMINS
 Thiamine (B1) needed for oxidation of carbs
 It is found in lean meats, liver ,eggs, whole-grain cereals, green vegetables
 A deficiency of vitamin
B1 enlarges the heart, causes muscular weakness, and beriberi.
 Beriberi is a nervous system ailment.
Symptoms include severe lethargy and fatigue , together with complications affecting the cardiovascular , nervous , muscular , and gastrointestinal systems.

VITAMINS
Riboflavin (B2) needed in the oxidation of glucose and and fatty acids
Found in meats, dairy products, whole grain cereal, and leafy green veggies
 If you do not get enough B2 you get blurred vision and dermatitis

VITAMINS
Pantothenic acid– o Also a B vitamin o Needed for oxidation of carbs and fats o Found in meats, milk, fruits, vegetables, legumes, whole-grain cereal
 A shortage of this vitamin is rare, but it causes mental depression, loss of appetite, and muscle spasms

VITAMINS
 Cyanocobalamin
(B12) – needed for synthesis of nucleic acids and for metabolism
 A loss of B12 causes pernicious anemia
 In liver, meat, and cheese, eggs

VITAMINS
 Folacin- (Folic Acid) Folic acid is a B vitamin. It helps the body make healthy new cells.
Everyone needs folic acid.
 For women who may get pregnant, it is really important. When a woman has enough folic acid in her body before and during pregnancy, it can prevent major birth defects of her baby's brain or spine.
 Metabolism of certain amino acids and for synthesis of DNA
 Found in leafy green vegetables, legumes, whole grain cereals

VITAMINS
 Ascorbic acid (C) – needed for production of collagen and metabolism of some amino acids
 Found in citrus fruits, tomatoes, potatoes, leafy green vegetables
 An excess of vitamin C exacerbates gout and kidney stone formation
 A shortage of it causes scurvy, lowered resistance to infection, and wounds heal slower