Lesson 6: Organs of the oral cavity

Where are the organs of the oral cavity derived from?

They arived from the first branchial or pharyngeal arch

What is the embryonic origin of the branchial arches and what are they?

The branchial arches are predonderantly mesodermal.

They are cleft-like structures located on both sides of the pharynx that originate during embryonic development

What are examples of first branchial arch syndromes?

Pierre-Robin syndrome Microgathnia

• cleft palate and tongue retraction

• Small mandibule causes the tongue to move backwards and downwards making breathing difficult

What is the oral mucosa and what are its parts?

Moist membrane lining the oral cavity. In the anterior sector it continues with the skin of the lips and in the posterior sector with the GI mucosa (pharynx)

What are the layers of the oral mucosa?

Made up by epithelial tissue and a connective tissue with a basement membrane in between. The are structurally and embryologically different structures

What are the components of the oral mucosa?

• Epithelium

• Basal cell layer

• Basement membrane

• Lamina propria

• Submucosa

What are the groups of oral mucosa?

• Lining mucosa

• masticatory mucosa

• Specialized mucosa

Where does the lining mucosa appear?

• Inner lips

• Ventral side of the tongue

• Mouth floor

• Inner cheeks

• Alveolar and vestibular mucosa

• Soft palate

What are the characteristics of the lining mucosa?

• Non-keratinized epithelium

• Smooth interface

• Elastic fibers in lamina propria and submucosa

Where does the masticatory mucosa appear?

• Marginal or adherent gingiva

• Hard palate

What are the characteristics of the masticatory mucosa?

• Keratinized epithelium

• Intergitated interface

• Thin layer of submucosa (or none)

Where does the specialized mucosa appear?

Only on the dorsal side of the tongue

What are the characteristics of the specialized mucosa?

• Distinct epithelial and connective tissue structures (papillae)

• Contains taste buds in certain areas.

• Some regions are keratinized, depending on function and location

What is the tongue and what are its functions?

The tongue is a very mobile muscular organ, which is covered with mucosa and anchored to the floor of the mouth.

It is an essential structure for the sense of taste, chewing, swallowing, sucking and phonation

What is the tongue and what are its functions?

The tongue is a very mobile muscular organ, which is covered with mucosa and anchored to the floor of the mouth.

It is an essential structure for the sense of taste, chewing, swallowing, sucking and phonation

Specialized mucosa of the tongue?

• Accommodates papilla that contain taste buds

• Epithelium with keratinized zones

• Lamina propria with dense connective tissue

• Submucosa with loose connective tissue

What are the steps of the development of the tongue?

1. On the endodermal side of the first branchial arch, there are two lateral lingual swellings and a tuberculum impar (or odd tubercle) arising from the lower edge of this arch.

2. The lateral lingual swellings move to the center and fuse with each other and in turn with the tuberculum impar, forming the anterior 2/3 of the body of the tongue, or mobile tongue.

When does the development of the tongue begin?

In the 4th week of the intrauterine life

How is the morphology of the tongue?

Anterior 2/3

• Conical shape

• Upper side is covered by specialized mucosa due to presence of numerous lingual papillae

Posterior 1/3 / base of tongue

• Vertical position forming anterior wall of pharynx

• non-keratinized stratified squamous epithelium that invaginates forming crypts

Inferior / ventral side

• thinner mucosa (underlying vesseks can be seen)

• Midline is the frenulum of tongue and the caruncles the sublingual and submandibular glands

How does the posterior 1/3 of the tongue extend?

Extends behind the terminal sulcus, behind the apex of which is located the foramen cecum

What accumulates in the base of the tongue?

Lymoh nodes accumulate and produce prominences that form the lingula tonsil.

What does the lingual tonsils participate in and what is it function?

In the waldeyers lymphatic ring together with the palatine and pharyngeal tonsils.

They act as a first defensive barrier against the entry of antigens via the digestive and respiratpry routes.

What are the lips and what are their characteristics and function?

• outermost soft and movable parts of the oral cavity

• Together with the tongue, it plays an important role in oral anatomy and physiology.

• The blood supply to the lips and tongue originates from the external carotid artery

How is the lining mucosa of the lips?

• Non-keratinized epithelium

• loose or semiloose lamina propria

• Well-developed submucosa with salivary glands, adipose tissue and muscle fibers

What are the topographic zones of the lips?

1. Skin of the outer lip

2. Transition zone

3. Lip mucosa

What structures are on the outer surface of the lips?

• Hair follicles

• Sebaceous glands (dermis): Fordyce glands (visible) sebum

• Sweat glands

What does sebum contain and what is its function?

Squalene, Cholesterol, Triglycerides

• Lubricate and protect skin surface

What regulates the production and secretion of sebum?

• Age and sex

• Endocrine factors

• Skin temperature

• Diet

• Cardiac variation

• Sweat glands

What is the function of sweat glands?

Body temperature regulation

How do the lips react to increased and decreased temperature?

Decreased:

• Vasoconstriction

• No sweat

• Increased metabolic activity

• Increased muscle tone and/or contraction

• Piloerection: „Hair standing on end“

Increased:

• Vasodilation

• Sweat

• Decreases metabolic activity

• Decreases muscle tone and / or contraction

How is the histology of the transition zone?

• Red in colour because it is composed of a highly vascularized dermis

• Thin and poorly keratinized

• Lacks sweat and sebaceous glands and is lubricated by saliva, preventing dehydration of the lips

How is the Histology of the lip (lining mucosa)?

• Non-keratinized stratified squamous epithelium

• Dense connective tissue lamina propria with numerous elastic and collagen fibers

• Submucosa loose connective tissue (poorly developed):

  • Mixed salivary glands with mucous predominance

  • Lymphoid clusters

Embryonic development of the lips

1. During 6th week of life: Maxillary prominences / processes grow towards a medial direction

2. Nasal fossae appear in the nasal placodes and then divide into two portions: medial nasal process and lateral nasal process.

3. The maxillary processes compress the medial nasal prominences towards the midline

4. During the 7th week: the two nasal processes grow and position themselves medially until they join to form the upper lip. The mandibular prominences converge in the midline forming the lower lip.

What are associated pathologies with the embryonic development of the lips?

Central cleft lip: Middle nasal processes do not fuse properly and a central cleft is formed where the subnasal groove would be

Unilateral cleft lip: When middle and lateral processes do not fuse properly with the maxillary process

Types of cleft lip

What are associated pathophysiologies with the skin and mucosal lesions

• Infections: Herpes virus

• Aphthas and ulcerations

• Tumors (lip cancer)

What is the palate and what is its function?

The palate is the roof of the mouth, which separates the oral cavity from the nasal cavity. It consists of the hard palate and

the soft palate which has no skeletal support and ends in a fleshy and elongated projection called uvula.

How is the masticatory mucosa of the palate?

• Keratinized or parakeratinized epithelium with numerous epithelial ridges (especially in gingivae)

• Semidense lamina propria

• It lacks submucosa in the gingiva but is present in the lateral part of the hard palate together with adipose and glandular tissue.

• It is directly subjected to intense forces of friction and pressure due to masticatory impact.

• Attached to the bone and does not undergo stretching

What are the characteristics of the soft palate?

• 2 Edges: Anterior: hard palate and posterior: uvula

• Skeletal muscle covered by oral lining mucosa

• Also known as Palatal velum.

What are the functions of the hard and soft palate?

Hard palate:

• Food handling and chewing

• support during suctions

• saliva secretion

Soft palate:

• Closure of the pharyngeal velum: prevents the passage of food, liquids and air into the nostrils.

• Phonation

• It acts as a sphincter (mobile and contractile).

Characteristics of the palatine tonsils

• They are bilateral, located at the limits of the oral cavity and oral pharynx, between the palatoglossal and palatopharyngeal folds

• Protect against antigens of airborne and ingested origins

When does the embryonic development of the palate begin?

• It begins in week 6 of intrauterine life and ends in week 13.

• Critical period at the end of the 6th to the beginning of the 9th

• Begins at the same time as the lips

How is the development process of the palate?

1. Primitive palate: Fusion of the nasal processes (also in lip formation) → intermaxillary segment

2. Secondary palate: In the 6th week the oblique palatine ridges begin to move until they fuse above the tongue (7th week). By fusing they separate the oral and nasal cavity. The anterior part of these ridges fuses with the primary palate forming the nasal septum. This septum grows and unites with the cephalic face of the palate (9-12th week)

What are the associated pathologies of the embryonic development of the palate?

What are examples of mucosal lesions of the palate?

• Food irritations or burns

• Aphthous ulcers or canker sores

• Infections

• Leukoplakia

• Tumors (Cancer)

How is the structure of the hard palate?

• 2 bones: palatine process of the upper jaw and the horizontal plate of the palate

• The incisive canal or fossa (N. nasopalatine) is found.

• Covered by salivary glands and masticatory oral mucosa

• Palatine tonsils