The oral cavity or mouth is that part of the digestive tract bounded by the lips anteriorly, the fauces throat; opening into the pharynx posteriorly, cheeks laterally, the palate superiorly, and a muscular floor inferiorly.

Is lined throughout with mucus membrane consisting of stratified squamous epithelium containing small mucus secreting glands.

The oral cavity is divided into two regions

The Vestibule; part of the mouth between Gums and Cheeks

The oral cavity proper; which lies medial to the alveolar processes (gums)

Lips

Cheeks

Hard and soft palates

Floor (mylohyoid muscle)

Lips

Are muscular structure formed mostly by the orbicularis oris muscles

They are covered externally by skin and internally by mucous membrane

Cheeks

Formed in large part by buccinator muscles covered by adipose tissue

They form the lateral boundaries of the oral cavity

They contain mucus secreting glands

Hard and soft palates;

forms the roof of mouth

consists of two parts

The hard palate: The anterior bony part, consists of portions of two maxillae and two palatine bones

The soft palate: The posterior non bony part, forms partition between the mouth and nasopharynx and is made of muscles arranged in an arch

The uvula

Suspended from midpoint of the posterior border of the arch

Are hard conical structures set in the dental alveoli (tooth sockets) of the upper and lower jaws and are used in mastication (chewing) and assisting in articulation

These are organs of mastication

Humans have two generations of teeth

The deciduous (primary) dentition

The permanent (secondary) dentition

Is a fibromuscular tube, approximately 25cm in length and 2cm in diameter, that transports food from the pharynx to the stomach.

Ends at the cardiac orifice of the stomach.

Food is transported through the esophagus by peristalsis- rhythmic contractions of muscles which propagate down the esophagus.

Hardening of these muscular layers can interfere with peristalsis and cause difficulty in swallowing (dysphagia)

STRUCTURE

It has four layers; from outside

Adventitia

Muscle layer

Submucosa

Mucosa

Outer layer of connective tissue, elastic fibrous tissue.

NB: The very distal and intraperitoneal portion of the esophagus has an outer covering of serosa, instead of adventitia.

There are two layers

The inner is circular

The outer is longitudinal

The external layer is composed of different muscle type in each third

Superior third – voluntary striated muscle

Middle third – voluntary striated and smooth muscle

Inferior third – smooth muscle

Made up of non-keratinized stratified squamous epithelium

There are two sphincter

Upper esophageal sphincter

Lower esophageal sphincter

This is an anatomical, striated muscle sphincter at the junction between the pharynx and esophagus

It is produced by the cricopharyngeus muscle

Normally, it is constricted to prevent the entrance of air into the esophagus

Is located at the gastro-esophageal junction

This sphincter is classified as a physiological (or functional) sphincter.

VASCULATURE

Arterial blood supply is through oesophageal arteries, branches of thoracic aorta, inferior phrenic arteries and the left gastric branch of the coeliac artery

Venous drainage is through the azygos and hemiazygos veins, and left gastric vein

Home work

Innervation

Lymphatic drainage of esophagus