Digestive System (Gastrointestinal)

Functions of the Digestive system:

1. Intake and digestion of food2. Absorption of nutrients from digested food3. Elimination of solid waste products

Accessory Organs of Digestion:Include the liver, gallbladder, and pancreas

Anatomy

Structures are divided into two sections:1. Upper GI tract – mouth, esophagus, stomach2. Lower GI tract – small intestine, large

intestine, rectum, anus

Oral Cavity (mouth)1. Lips – form opening to the mouth2. Hard palate – anterior portion of roof of mouth3. Soft palate – posterior portion of roof of mouth,

closes off nasal passage during swallowing4. Uvula – helps in producing sound and speech

Upper GI tract Cont’d.

Tongue – strong and flexible, aids in speech and moves food during chewing and swallowing, contains papillae which are also known as taste buds.

Teeth – 20 baby teeth, 32 permanent teeth; four kinds:1. Incisors2. Canines3. Premolars (bicuspids)4. Molars

Upper GI tract Cont’d.

Parts of a tooth1. Crown – the part of the tooth that is

visible, covered with enamel

2. Root – holds the tooth securely in the dental arch

3. Dentin – makes up the bulk of the tooth

Gingiva (gums) – surrounds teeth, covers the bone of the dental arches, forms the lining of cheeks

Salivary Glands – secretes saliva to moisten food, begins digestive process, cleanses the mouth

Upper GI tract Cont’d.

Pharynx (also known as the throat)• common passageway for food and air • during swallowing, food is prevented from moving from the pharynx into the lungs by the epiglottis.

Esophagus• collapsible tube that leads from the

pharynx to the stomach• the lower esophageal sphincter is a muscle that controls the flow between the esophagus and the stomach.

Upper GI tract Cont’d.

Stomach• has 3 sections: fundus, body, and the antrum• the pyloric sphincter controls flow from stomach into

the duodenum of the small intestine.

Lower GI tract

Small Intestine – extends from pyloric sphincter to the large intestine; in the small intestine is where nutrients are absorbed into bloodstream; 20 feet in length; has three sections:

1. Duodenum – first section, closest to the stomach2. Jejunum – middle section, between duodenum and

ileum3. Ileum – last section, closest

to the large intestine

Lower GI tract Cont’d.

Large Intestine – waste products of digestion are processed in the large intestine and excreted through the anus; has 6 sections :

1. Cecum – pouch that pouch that extends from the ileum to the beginning of the colon

2. Ascending colon – travels upward from cecum3. Transverse colon – passes right to left toward the spleen4. Descending colon – travels down

the left side of abdominal cavity5. Sigmoid colon – joins descending

colon with the rectum6. Rectum – last division of the large intestine

Anus – solid waste is passed out of the body through the anus

Accessory Organs of Digestion

Liver (located in the right upper quadrant)• removes excess glucose from the bloodstream • destroys old red blood cells• removes poisons from blood • makes some blood proteins• secretes bile to break down fat

Gallbladder • stores and concentrates bile for later use

Pancreas• located posterior to the stomach, creates pancreatic

juices to neutralize stomach acids and digestive enzymes to process protein, carbohydrates, and fat.

Definitions

Digestion – process by which complex foods are broken down into nutrients that the body can use

Metabolism – all of the processes involved in the body’s use of these nutrients(building up and breaking down of body cells)

Absorption – process where digested nutrients are taken into the circulatory system

Definitions Cont’d

Mastication – also known as chewing, breaks down food into smaller pieces

Peristalsis – series of wavelike contractions of smooth muscles in a single direction.

Chyme – semi-fluid mass of partially digested food that passes from stomach into small intestine

Defecation – evacuation or emptying of the large intestine

Flow through the Digestive System

The Language of Medicine, 7th Edition; Chabner, Davi-Ellen; Saunders, 2004

You will need to know the order of flow

for food moving

through the digestive

system on your next test.

ACTIVITY

How The Stomach

Works