Download The Digestive System

The Digestive System
I.
General information
A. Gastrointestinal (GI) tract aka alimentary canal
B. Structure
1. 29 foot long tube
2. Open at both ends
3. Located in the ventral cavity
4. Four layers
A. Mucosa – epithelial tissue
B. Submucosa – capillaries
C. Muscularis – muscle; longitudinal and circular
D. Serosa – connective tissue, gives shape to the organ
C. Functions (Digestion)
1. Mechanical and chemical breakdown of food
2. Absorption of nutrients
II.
Mouth (buccal cavity)
1. Salivary glands
A. Three pairs
B. Secrete one liter of saliva per day
2. Tongue
A. Muscles
B. Taste buds
3. Teeth
A. 32 in the young adult, 2 incisors, 1 canine, 2 premolar, s molars (including wisdom teeth)
B. Function: Mechanical breakdown food through mastication
4. Mastication of food (initiates digestion)
A. Breaks food into smaller pieces
B. Increase surface area of food, thus increasing absorption rate
C. Mixes food with saliva
D. Forms a bolus, or ball which is easily swallowed
III.
Throat
1.
2.
3.
4.
IV.
Leads to esophagus and trachea
Passageway for air
Passageway for food
3 divisions:
A. Nasopharynx
B. Oropharunx
C. Laryngopharynx
Esophagus
1. Location:
A. Extends to pharynx to stomach
B. Passes through diaphragm
C. Posterior to trachea
2. Structure:
A. Muscular tube shaped
B. Four layer so f tissue; mucosa, submucosa, muscularis and serosa
3. Function:
Movement of food from pharynx to stomach via peristalsis
V.
Stomach
1.
2.
3.
4.
5.
Muscular pouch which stores and churns food
Very acidic environment (ph of 2)
2 sphincters (muscular rings) keep from entering/exiting while churning
Located under diaphragm in abdomino pelvic cavity
Four layers structure:
• Mucosa
• Submucosa
• Muscularis
• Serosa
6. Functions:
A. Reservoir for food (2-6 hours)
B. Secretion of hormone gastrin to release digestive juices
C. Secretion of digestive juices
D. Mechanical digestion (churning)
E. Absorbs alcohol, drugs, and water (10% of alcohol enters blood immediately)
F. Digestive juices and food create chime, semisolid
VI.
Small intestine
1.
2.
3.
4.
Digestion is completed here
Receives digestive enzymes from pancreas bile, liver and gall bladder
Location: Abdominopelvic cavity
Structure:
A. One inch diameter
B. Approximately 20 feet long
C. Four layers:
• Mucosa
• Submucosa
• Muscularis
• Serosa
D. Protrusion on the villi; called plicae; increase surface area for absorption;
vascularized with blood and lymph vessels
5. Three parts:
A. Duodenum – 10 inches
B. Jejunum – 8 feet long
C. Ileum – 12 feet long
VII.
Large intestine
1. Location: abdominopelvic cavity
2. Two and half inches diameter tube, approximately 5-6 feet long. It has 4 basic layers
3. Three parts:
A. First 2-3 inches – secum with ileoceal valve
B. Colon - regions;
• Ascending
• Transverse
• Descending
• Sigmoid
4. Functions:
A. Absorb water
B. Absorb some nutrients
C. Produces vitamins and B complex
D. Provide environment for friendly bacteria
E. Elimination of wastes
F. Vitamins; fat soluble ADEK
G. Vitamins; water soluble B-15, and C
VIII.
Accessory organs
A. Liver - largest exocrine gland in the body 5-6 pounds, capable of regeneration
1. Functions:
A. Secretes one pint of bile per day
B. Releases bile into gall bladder
C. Metabolizes fats, proteins and carbohydrates
D. Detoxifies blood of drugs and hormones
E. Stores irons, vitamins, A, B-12, D, E, and K
F. Regulates blood sugar level if blood sugar is high, glucose is stored as
glycogen
2. Location: Right upper quadrant
B. Gall bladder – Located under the liver
1. Stores and concentrates bile (up to 10 times)
2. Ejects bile into duodenum of small intestine
3. Bile emulsifies fats, breaks down into smaller pieces
C. Pancreas – Located in the left upper quadrant
1. Produces digestive enzymes
2. Releases digestive enzymes into the small intestine
A. Amylase (carbs)
B. Protease (proteins)
C. Lipase (lipids)
3. Regulates blood sugar by release of insulin and glucagon
*Appendix – Vestigal organ, no real function (lymphatic tissue)
IX. Digestion & Absorption
A. Mechanical - physical breakdown and movement of food
1. Mastification: chewing of food breakdown into smaller pieces
2. Degulution : swallowing
3. Bolus: food and saliva
4. Churning: stomach mixes food and digestive juices
5. Peristalsis: wavelike movement of food through the digestive tract
6. Defecation: elimination of stool
B. Chemical digestion – Process whereby food is broken down by enzymes for
absorption
1. Protein +H2O+protease = amino acids (needed for cell repair and growth)
2. Carbohydrates + amylase+O2= glucose, fructose, ATP (body’s preferred energy
source)
3. Lipids +lipase = glycerol +fatty acids (body’s choice of energy source)
Digestive System – Pathology
X.
A. Diverticulitis: Inflammation of small sacs in the muscle wall of the sigmoid colons
B. Hietal hernia: Protrusion of the stomach into the mediastinal cavity above the
diaphragm
C. Ulcers : Am open sore or lesion of the skin or mucous membrane
D. Colitis: A chronic, non-specific, inflammatory disease (ulcerative) of the colon with
bloody diarrhea
E. Hepatitis: Inflammation of the liver
F. Choleocystitis : Inflammation of the gall bladder
G. Cirrhosis: A chronic disease of the liver characterized by dense formation of
connective tissue, loss of function of liver cells, increased resistance to blood flow.
(high blood pressure)
XI.
Minerals and Metabolism
Definitions:
A. Nutrients: Chemical substances needed by the body for normal functioning for example
muscle contraction and nerve conduction
1. Water
2. Carbohydrates
3. Proteins
4. Lipids
5. Minerals
6. Vitamins
B. Essential nutrients: Nutrients which must be ingested in our diet because they body
cannot produce them
C. Metabolism: What our body does with the nutrients ; anabolism and catabolism =
metabolism
1. Anabolism – Building up larger molecules from smaller ones ; requires energy
2. Catabolism – Breaking down of larger molecules into smaller ones; releases energy
3. Energy value of food is given in kilocalories (kcal) = amounts of heat release when
burned…
D. Functions of Nutrients :
1. Production of energy
2. Build new compounds
3. Assist in chemical reactions
E. Water:
1. Provides medium for chemical reactions
2. Helps maintain fluid balance
3. Transportation
4. Participation in some chemical reactions
5. Intake – normal = ½ oz per 1 pound of body weight; when active it should be ¾ oz.
XII.
Nutrients
A. Carbohydrates
1. Three mains types:
A. Monosaccharides = simple sugars (glucose, fructose, galactose)
B. Disaccharides = 2 simple sugars together
• Sucrose = glucose + fructose
• Lactose = glucose + galactose
• Maltose = glucose + glucose
C. Polysaccharides = 3 types---many sugars
1. Starch = peas, beans, potatoes, pasta
2. Fiber = 2 types
A. Water soluble – oats, beans and fruits
B. Water insoluble – cellulose
3. Glycogen = animal polysaccharides
2. Role in the body:
A. Body’s most preferred energy source – carbohydrates
B. Anaerobic process – Does not need O2=2 ATP molecules produced
C. Aerobic process – Requires 02—approx 36 ATP molecules produced (Both
processes involve the breakdown of sugars into energy)
D. Brain almost exclusively uses glucose as energy source
E. Yields 4 Kcal energy per gram
F. Excess glucose stored in liver as glycogen or converted to fat
B. Lipids
1. Made of glycerol molecule with fatty acid chains attached
• Monoglyceride = Glycerol with one fatty acid
• Diglyceride = Glycerol with two fatty acids
• Triglycerides = Glycerol with three fatty acids—most commonly
ingested form
2. Two types:
A. Saturated fat – no double bonds in fatty acid chain. Found primarily in
animal products and coconut oil (solid @room temperature)
B. Unsaturated fat – 1 or more double bonds in fatty acid chain
• Mono = one double bond
• Poly = more than 1 double bond
*Hydrogenation = process which removes double binds to produce a semisolid
compound. (oil and hydrogen = margarine)
3. Role in the body:
A. Less than 30 % fat in diet from RDA (3 grams per 100 cal)
B. Fat produces 9 Kcal energy per gram (more than carbohydrates)
C. Second preferred source of energy
D. Functions:
1. Energy stores
2. Cushions vital organs
3. Provides insulation
C. Protein
1. Amino acid chains –22 total amino acids. 10 are produced by the body, 12
are essential and need to be ingested
2. 15% of dietary intake is recommended
3. Used for many different structures—hormones, tissues, enzymes etc.
4. Can be used as energy source (not good…)
5. Only need about .8 grams per Kg of body weight
6. “Amino acid supplementation has not been shown to improve strength,
power, and muscle mass or endurance…
D. Vitamins
1. Organic compound needed in trace amounts
2. Serve as chemical regulators and coenzymes
3. Two types:
A. Fat soluble: A,D,E,K
B. Water soluble: C,B complex
4. RDA =20% above amount would need to be deficient
5. “Vitamin supplementation does not improve performance”.
E. Minerals:
Types:
• Zn, Mg, K, Na, Ca
1. Inorganic compounds which serve as regulators and coenzymes
2. Need only trace amounts
3. Become incorporated into structures of the body –hemoglobin, iron,
skeletal /calcium.
F. Water:
1. Important in maintaining homeostasis
2. Intake comes from three sources:
A. Liquids
B. Food
C. Metabolic water produced in chemical reactions
*Body weight
A. Energy output must be greater than energy input to lose weight
B. If energy input is too low, body lowers metabolic rate to conserve stores.