A&P II: GI Quiz

Digestive System

Two main components:

1. gastrointestinal tract (alimentary canal)

   • tube running from mouth to anus

   • mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus - know the order

2. Accessory organs

   • teeth, tongue, salivary glands, liver, gallbladder, & pancreas

Process of Digestive System**

1. Ingestion-process involves taking foods and liquids into the mouth

2. Digestion- (2 types)

   • Mechanical-breaking food into smaller pieces (bolus)

   • Chemical-digestive enzymes to break food into smaller pieces

3. Mixing and propulsion-contractions and relaxations of the GI tract mix food and propel them onward (motility) - peristalsis

4. Secretion-release of digestive juices & hormones to regulate digestion or metabolism of nutrients.

5. Absorption-movement of digested nutrients through the GI mucosa and into internal environment (blood & lymph)

6. Defecation-wastes, indigestible substances, bacteria, and cells from lining of GI tract leave the body (as feces or stool)

Stages of Digestion

1. Ingestion: the intake of food through the mouth

2. Mechanical digestion: mastication breaks down food into smaller particles

3. Chemical digestion (stomach): food travels of the stomach where gastric juice containing enzymes break particles down further. 

4. Chyme formation: partially digested food moves from stomach to small intestine

5. Chemical digestion (small intestines): Enzymes from the pancreas and bile from the liver break down fats, proteins, carbohydrates into absorbable nutrients

6. Nutrient absorption: Amino acids, fatty acids and sugars are absorbed through the walls of the small intestines into the bloodstream

7. Water and electrolyte absorption: the remaining material moves to the large intestines where water and electrolytes are absorbed

8. Feces formation: the indigestible material forms feces, which is stored in the rectum

9. Elimination: feces are expelled from the body through the anus during the process of defecation

Two Ways to Digest Food**

Mechanical: breaking food down into smaller pieces

• mastication - increases surface area of food and allows food to be broken down to smaller pieces to be swallowed safely

• deglutition - three phases: oropharyngeal, esophageal, and gastroesophageal (swallowing)

• peristalsis - contractions and relaxations of the GI tract to mix food and propel them onward

Chemical: enzymatic breakdown of large molecules into small ones; requires secretion of digestive enzymes & bile into the lumen of GI tract

Order of Digestion

1. mouth

2. pharynx

3. deglutition (swallowing) - oropharyngeal, esophageal, and gastroesophageal

4. stomach

5. small intestine

6. large intestine

7. anus

8. defecation

Structural layers of the alimentary tube

• Mucosa - inner layer

• Submucosa - Meissner’s Plexus is located in the submucosa (nerve network)

• Muscularis

• Serosa - outer layer

Lumen - inside of the tube

3 Pairs of Salivary Glands

• Parotid gland

• Submandibular gland

• Sublingual gland

Esophagus

• posterior to the trachea

Gastric Juices

• hydrochloric acid - really strong gastric juice in the stomach

Emulsification

Bile breaks down fat into smaller droplets so that digestive enzymes can work on them; fats - emulsified

What 2 ducts meet in the common bile duct?

• hepatic duct

• cystic duct

Glycolysis

process of carbohydrate catabolism (break down of carbohydrates

Basal Metabolic Rate (BMR)

• pregnancy & lactation can increase BMR

Bile

• liver secretes bile

• gallbladder stores bile

Pancreas

• endocrine & exocrine glands

• secretes insulin & pancreatic juices

  • pancreatic enzymes: amylase, lipase, trypsinogen

Bicarbonates

• neutralizes hydrochloric acid

Emulsification

bile salts needed to breakdown fats

Small Intestine

Don’t Judge Ice Cream

Duodenum

jejunum

ileum

What is the process called when contracting and relaxing occurs and propelling food through the system

peristalsis

cardiac sphincter or lower esophageal sphincter (LES)

 a muscular ring that controls the flow of food and stomach acid between the esophagus and stomach