Chapter 14, Digestive System, Part B

Chapter 14: Digestive System & Nutrition: Part B
1. Accessory organs
a. Teeth
b. Salivary glands
c. Pancreas
d. Liver
e. Gall bladder
2. Teeth classification
a. Incisors - cutting
b. Canines – tearing or piercing
c. Premolars - grinding
d. Molars - grinding
3. Salivary glands – three pairs of salivary glands empty secretions into the mouth:
a. Parotid glands – largest, near ear
b. Submandibular glands – under jaw
c. Sublingual glands – under tongue
d. Saliva
i. Mixture of mucus and serous fluids
1. Mucus
2. Serous
ii. Helps to form a food bolus
iii. Contains salivary amylases to begin starch digestion
iv. Dissolves chemicals so they can be tasted
4. Deglutition = swallowing
a. Buccal phase
i. Voluntary
ii. Occurs in the mouth
iii. Food is formed into a bolus
iv. The bolus is forced into the pharynx by the tongue
b. Pharyngeal-esophageal phase
i. Involuntary transport of the bolus
ii. Passageways blocked (except to the stomach)
iii. Tongue blocks off the mouth
iv. Soft palate (uvula) blocks the nasopharynx
v. Epiglottis blocks the larynx
vi. Peristalsis moves the bolus towards the stomach
vii. Cardio-esophageal sphincter
5. Pancreas
a. Posterior to the parietal peritoneum
b. Extends across the abdomen from the spleen to the duodenum
c. Produces a wide spectrum of digestive enzymes that break down all categories of food
d. Enzymes are secreted into the duodenum
e. Alkaline fluid (basic) introduced with enzymes neutralizes acidic chime coming from stomach
f. Hormones produced by the pancreas:
i. Insulin – lower blood sugar; sugar into cells
ii. Glucagon – raises blood sugar; liver; glycogen
6. Liver
a. Size – largest gland in the body
b. Location – located on the right side of the body under the diaphragm
c. Consists of four lobes suspended from the diaphragm and abdominal wall
d. Connected to the gallbladder via the common hepatic duct
e. Produces bile
i. Salts
ii. Pigments
iii. Function
7. Gall bladder
a. Structure & location
i. Sac found in hollow fossa of liver
b. When no digestion is occurring, bile backs up the cystic duct for storage in the gallbladder.
c. When digestion of fatty food is occurring, bile is introduced into the duodenum from the gallbladder
d. Gallstones are crystallized cholesterol which can cause blockages
8. Functions to accomplish digestion
a. Ingestion—getting food into the mouth
b. Propulsion—moving foods from one region of the digestive system to another
c. Peristalsis—alternating waves of contraction and relaxation that squeezes food along the GI (gastro intestinal) tract
d. Segmentation—moving materials back and forth to aid with mixing in the small intestine
e. Food breakdown as Mechanical digestion
i. Examples:
1. Mixing food in the mouth by the tongue
2. Churning food in the stomach
3. Segmentation in the small intestine
4. Mechanical digestion exposes surface area of food for further breakdown by enzymes
f. Chemical digestion
i. Enzymes break down food molecules into their building blocks
ii. Each major food group uses different enzymes:
1. Carbohydrates are broken to simple sugars
2. Proteins are broken to amino acids
3. Lipids are broken to fatty acids and alcohols
g. Absorption
i. End products of digestion are absorbed in the blood or lymph capillaries (thin walls)
h. Defecation
i. Elimination of indigestible substances from the GI tract in the form of feces
ii. Also: bacteria, bile pigments
9. Nutrition
a. Nutrients (food)—substance used by the body for growth, maintenance, and repair
i. Major nutrients
1. Carbohydrates: sugars, starches: energy
2. Lipids: fats, oils, waxes: energy, structure
3. Proteins: energy, structure, enzymes
4. Water : no energy, body solvent
ii. Minor nutrients
1. Vitamins: coenzymes, metaabolism
2. Minerals: inorganic, assist physiology, anatomy
b. USDA food guide pyramid