Chapter 8 - The Digestive System

Accessory organs

“aid with digestion, but are not part of the digestive system.” More accurate to say they are not DIRECTLY part of the digestive system because food does not pass through these structures.

• liver

• galllbladder

• pancreas

gastrointestinal tract or GI tract

structures of the digestive system are also described as the

upper GI tract

consists of the mouth, esophagus, and stomach.

lower GI tract

made up of the small and large intestines (bowels), plus the rectum, and anus.

Major structure of the oral cavity (mouth)

• lips

• hard and soft palates

• salivary glands

• tongue

• teeth

• periodontium

lips (labia)

form the opening to the oral cavity (singular, labium). The same term also refers to parts of the female genitalia

during eating, the lips hold food in the mouth and aid the tongue and cheeks in guiding food between the teeth for chewing

also important roles in breathing, speaking, and the expression of emotions

Upper and lower labial frenum

are narrow bands of tissue that attach the lips to the jaws

Hard palate

the bony anterior portion of the palate that is covered with a specialized mucous membrane

Rugae

irregular ridges or folds in this mucous membrane (singular, ruga)

Soft palate

the flexible posterior portion of the palate.

it has the important role of closing off the nasal passage during swallowing to prevent food and liquid from moving upward into the nasal cavity.

Uvula

hangs from the free edge of the soft palate. During swallowing, it moves upward with the soft palate. Also plays and important role in snoring and the formation of some speech sounds.

Tongue

• very strong flexible, and muscular

• aids in speech

• moves food during chewing and swallowing

Dorsum

Upper surface of the tongue.

This surface has a protective covering and, in some areas, small bumps known as papillae (singular, papilla).

Sublingual surface

of the tongue and the tissues that lie under the tongue are covered with delicate, highly vascular tissues

Sublingual

under the tongue

Highly vascular

containing many blood vessels

Lingual frenum

attaches the tongue to the floor of the mouth and limits its motion

Periodontium

consists of the bone and soft tissues that surround and support the teeth

odonti

teeth

Gingiva (gums)

the specialized mucous membrane that surrounds the teeth, covers the bone of the dental arches, and lines the cheeks.

Dental Arches

• The boney structures of the oral cavity consist of the maxillary and mandibular arches

• Commonly referred to as the upper and lower jaws

• Firmly hold teeth in position to facilitate chewing and speaking

Temporomandibular joint (TMJ)

• is formed at the back of the mouth where the maxillary and mandibular arches come together

• The maxilllary arch, which is part of the skull, does not move

• The mandibular arch, whcih is a seperate bone, is the moveable component of this joint

Dentition

the natural teeth arranged in the upper and lower jaws

incisors

biting and tearing

canines (cuspids)

Biting and tearing

premolars (bicuspids)

chewing and grinding

molars

chewing and grinding

Primary dentition (deciduous dentition/baby teeth)

• consists of 20 teeth that are normally lost during childhood and are replaced by the permanent teeth.

• These teeth include:

  • 8 incisors

  • 4 canines

  • 8 molars

  • No premolars

Permanent dentition

• 32 teeth that are designed to last a lifetime

• These teeth include:

  • 8 incisors

  • 4 canines

  • 8 premolars

  • 12 molars

Edentulous

means without teeth

Occlusion

describes any contact between the chewing surfaces of the upper and lower teeth

Malocclusion

any deviation from the normal positioning of the upper teeth against the lower teeth

Crown

The portion of a tooth that is visible in the mouth

Enamel

covers the crown. It is the hardest substance in the body

Roots

hold the tooth securely in place within the dental arch.

Cementum

protects the roots. This is strong but not as hard as enamel.

Cervix

neck of the tooth is where the crown and root meet

dentin

makes up the bulk of the tooth structure and is protected on the outer surfaces by the enamel and cementum

pulp

consists of a rich supply of blood vessels and nerves that provide nutrients and innervation to the tooth. In the crown, the pulp is located in the pulp cavity. In the roots, the pulp continues through the root canals

Saliva

colorless liquid that moistens the mouth, begins the digestive process. and lubricates food during chewing a swallowing.

parotid glands

located on the face in front of and lsightly lower than each ear. The ducts for these glands are on the inside of the cheek near the upper molars

Sublingual glands and their ducts

located on the floor of the mouth under the tongue

submandibular glands and their ducts

located on the floor of the mouth near the mandible

Pharynx

common passageway for both respiration and digestion,commonly known as the throat, allows food, liquids, and air to pass through it

Epiglottis

a lid like structure that closes off the entrance to the trachea (windpipe) to prevent food and liquids from moving into the laryngopharynx during swallowing

Esophagus

muscular tube through which ingested food passes from pharynx to stomach

lower esophagea, sphincter (cardiac sphincter or gastroesophageal sphincter)

a muscular ring that controls the flow between the esophagus and stomach. Normally opens to allow the flow of food into the stomach and closes to prevent stomach contents from regurgiating into the esophagus

regurgitating

means to flow backward

stomach

a sac like organ composed of the fundus (upper, rounded part), body (main portion), and antrum (lower part).

Rugae

the folds in the mucosa lining the stomach. Glands located within these folds produce gastric juices that aid in digestion and mucus to create a protective coating on teh lining of the stomach.

Pylorus

the narrow passage that connects the stomach with the small intestine

Pyloric sphincter

the ring like muscle that controls the flow from the stomach to the duodenum of the small intestine