The Mouth (Anatomy)

The regions of the mouth we'll be covering in this post are:

1. labia
2. cheeks
3. oral vestibule/cavity proper
4. palates (soft and hard)
5. uvula
6. Palatine arches
7. tonsils
8. salivary glands, saliva composition
9. tongue

So, let's get started!

Food, drink and other questionable substances are "ingested" via the oral vestibule into the oral cavity proper.  They reach the fauces, pass into the oropharynx and down into the oesophagus.  The journey from this point will lead to the digestive organs: the stomach and intestines, and finally to defecation as faeces via the anal sphincter.   Oh and along the way, some food is retained for the body! 

Labia

Effectively a posh name for your lips, it has a three layer structure: 

1. Skin on the outer surface
2. Orbicularis oris muscle within
3. And a mucous membrane of stratified squamous epithelia as the innermost layer. 

The labia, along with the cheeks, mark the outer region of the oral vestibule. 

Cheeks

These compose of another, very similar, three layer structure: 

1. Outermost skin
2. Middle layer of buccinator muscle
3. Innermost layer of mucosal membrane that is stratified squamous epithelia. 

Oral vestibule/cavity

The vestibule is merely the space bordered internally by the teeth and gums (gingiva) and externally by the labia and cheeks. 

The cavity runs from the vestibule (gums and teeth) to the fauces at the order of the cavity and the oropharynx. 

Palates and Uvula

There are 2 palates: soft and hard.  

The hard is composed of maxillary and palatine bone, the soft of muscle.  At the free border of the soft palate is a projection of tissue called the "uvula".   During swallowing, the uvula rises superiorly with the soft palate to prevent ingested matter from passing into the nasopharynx. 

The uvula means "little grape" for obvious reasons!

Palatine arches

These arches are found projecting laterally from the uvula.  There is the "palatopharyngeal" arch with moves laterally to the base sides of the pharynx, and the "palatoglossal" arch which moves to the side/base of the tongue. 

In between the arches are the palatine tonsils, the others are the lingual tonsils (found at the base of the tongue). 

Salivary Glands (Minor)

The minor glands are composed of 2 camps: 

1. Mouth: buccal, palatine and labial.
2. Tongue: lingual.  

Major glands: 

1. Parotid: lies anteriorly and inferiorly to the ear bilaterally. The parotid duct runs through the buccinator muscle and drains into the oral cavity proper opposite to the second molar.   The parotid salivary gland secretes amylase. 
2. Submandibular: lies on the floor of the mouth, inferomedial to the mandible.  The ducts drain laterally into the oral cavity proper on either side of the lingual frenulum. 
3. Sublingual:  lies superior to the submandibular gland but inferior to the tongue.   The lesser sublingular duct opens into the floor of the buccal cavity. 

Salivary composition

99.5% water ; 0.5% solutes ; 

Why so much water?   Because it is needed for effective a) use of gustation receptors and b) for digestive reactions to occur. 

What solutes are present?  Sodium, potassium, chloride, urea, uric acid, mucous, IgA, lysozymes, amylase, lipase, bicarbonates and phosphates etc. 

Urea and uric acid are excreted.  Mucous lubricates the GI tract layers and thickens the secretions (of the submandibular salivary gland).  IgA prevents microbial invasion of the epithelia of the GI.  Lysozymes digest the peptidoglycan cell walls of bacteria.  Amylase (activated by Cl-) converts starch into maltose, maltotriose and alpha dextrin.  Lipase (secreted by the lingual minor gland) converts lipids and triglycerides into simpler lipids and diglycerides respectively.   Bicarbonates and phosphates are responsible for buffering the saliva and maintaining the pH at "slightly acidic" levels of 6.35-85.

The tongue notes may follow, time depending.