SS - ORAL CAVITY & TONGUE

ORAL CAVITY STRUCTURE & FUNCTION

STUCTURE

• The oral cavity has two parts; oral vestibule and oral cavity proper 

• The teeth and gums separate the two. 

FUNCTION

1. Ingestion

2. Mastication (Chewing)

3. Digestion 

4. Pressurise air (EX: whistling)

5. Vocal tract

   • obstruct/partially obstruct sound

   • Modify resonance of sound by changing shape

BOUNDARIES OF ORAL CAVITY PROPER

Anterior Boundary → Teeth

Lateral Boundary → Teeth (in alveolar ridges)

Posteriorly → Palatoglossal arch (anterior faucial pillar)

Superior → Soft & Hard Palates

Inferior → Tongue 

FUNCTION:

• Intake and digestion of food and water

• Formation of speech

• Respiration

BOUNDARIES OF ORAL VESTIBULE

• Vestibule of mouth is basically sides of mouth inside the cheek (the space in between)

• Space between the lips and cheeks, and the teeth/gingiva

• FUNCTION:

• Containing food during mastication, aided by muscles such as the buccinator which helps keep food between the teeth.

• Houses the opening of the parotid duct opposite the upper second molar, which secretes saliva into this space.

LIPS: STRUCTURE & FUNCTION

Mobile muscle covered by skin and lined by mucous membrane*. **A mucous membrane is a protective, moisture-producing tissue that lines body parts exposed to the external environment Labial glands produce saliva inside the lips & open into the oral cavity  Controlled by orbicularis oris muscles Outer and inner part of lips are covered by different types of epithelial tissue  Upper lip is attached to gums through frenulum of the upper lip

Close against possible exit of food Mediate facial expression Add volume to oral cavity proper Act as a sphincter to produce sounds, EX: “p” via the action of facial muscles Form a “lip reed” to affect expired air (brass musicians)

CHEEKS: STRUCTURE & FUNCTION

Mobile inner component: buccinator Cheek shape is formed by the buccinator muscles Buccinator function = Propels food from vestibule to bring it to centre of oral cavity  Inside of cheeks = mucous membrane  Inside of cheeks = Parotid Duct = duct of the parotid gland Around this opening of the parotid duct, you will find the papilla of the parotid duct = small elevations where the duct opens into the oral vestibule

Changes the volume of the oral cavity Keeps food (or air) in oral cavity proper  Buccinator function = Propels food from vestibule to bring it to centre of oral cavity  Parotid duct??

GUMS: STRUCTURE & FUNCTION

• Gums is a mucous membrane covering the alveolar process of the maxilla and mandible

• They form a place for the teeth to be rooted in 

• Gums are composed of dense fibrous tissue 

• Gingival papillae = projections you see between the neck of the teeth

  

TEETH: STRUCTURE & FUNCTION

Crown of tooth = visible part of tooth  Neck of tooth = between crown & root Covered by the gums  Root of tooth  Fixated inside of the dental alveolus = supported by periodontium In tooth, there’s a cavity, and in cavity = dental pulp is found = (LCT rich in neurovascular structures) Pulp cavity continues downwards as the root canal. This connects to apical foramen which carries blood vessels and nerves from maxilla and mandible Around pulp cavity is the Dentin = makes up the basic substance of the tooth Cement is around the dentin (calcified structure)   Dentin is covered by enamel = mineralised tissue Enamel = 96% mineral Dentin = 66% mineral Cementum = 50% mineral

Provide the mechanism for mastication & the articular surfaces for several speech sounds  No evidence that abnormal teeth arrangement causes articular disorders (but affects mastication)  Tongue can adjust somewhat for teeth defects in speech

TEETH; LIFE CYCLE

PRENATAL GROWTH

• Deciduous & permanent teeth developed in utero (in uterus in the womb)

• Deciduous teeth begin developing at 5-6 weeks

• Perm. teeth develop above deciduous teeth at about 10 weeks 

• Development follows development of the whole skeleton

• Teeth do not “erupt” (emerge from gums) until approx 6 months after birth 

ERRUPTION

• Calcification (when mineralisation occurs): dentin & enamel harden 

1. Interosseus eruption: some bone of the mandible & maxillae above the teeth resorb (breaks down) to make way for the tooth’s movement toward the gum

2. Clinical eruption: teeth emerge through gums

TEETH; TOOTH WEAR

1. Attrition = physiological wearing away of enamel as a result of tooth to tooth contact (EX: grinding) 

2. Abrasion = physical wear via abnormal mechanical process (EX: violent brushing) 

3. Erosion = loss of tooth surface via chemical process (not bacterial (EX: diet related acids, like coke) 

   

TEETH STRUCTURE

• Deciduous teeth = 5 in each quadrant = 20 total

• Perm teeth = 7 in each quadrant = 28 total 

• Third molars = wisdom teeth = thus 32 total 

• Children have two molars, but when they get perm. teeth they get 2 premolars and then 2 molars, then wisdom teeth

TEETH; DENTAL SUCCESSION DECIDUOUS TEETH

• Erupts from 6 mo. - 2yrs

• Sheds from 6 yrs - 15 yrs

TOOTH APPEAR	SHED (full eruption)
Central Incisors (6-8 mo.)	6-8 yrs
Lateral Incisors (8-20 mo.)	6.5 - 8.5 years
1st Molar & Canines (15-20 mo.)	9.5 - 12 yrs
2nd Molar (20-24 mo.)	10 - 11.5 yrs

TEETH; DENTAL SUCCESSION PERMANENT TEETH

TOOTH	SHED (full eruption)
Central & Lateral Incisors, 1st Molars	6-9 yrs
1st & 2nd Premolars & Canines	9 - 12 years
2nd Molars	11 - 13 yrs
3rd Molars	17 - 25 yrs

GENERAL STRUCTURE & FUNCTION OF SALIVARY GLANDS

All exocrine glands have ducts. 

FUNCTION:

• Initiate digestion

• Soften bolus

• Allows for frictionless movement for speech

STRUCTURE:

• Saliva is made up of two components 

1. Serous Component = contains enzymes that helps break down & digest food we eat

2. Mucous component - lubricates the inner surfaces of our mouth & lubricates the food we eat so it passes easily (Mainly produces mucin that absorbs water to create a lubricator called mucus) 

PAROTID GLANDS

• Opens into the buccal cavity above the upper second molar tooth (via the parotid duct) 

• Largest salivary gland humans have 

• Purely serous gland (helps break down food) 

• Function = produce watery secretion containing enzymes 

• Located on the lateral surface of the head, anterior to the auricle 

• When the parotid gland produces its serous secretion, it's going to send them through a duct called the parotid duct

• This opens up at the upper side of the cheeks. The opening of the parotid duct has a papilla round it, called the papilla of the parotid duct. 

SUBMANDIBULAR GLANDS

• OPENS IN THE FLOOR OF THE MOUTH

• Contains seromucous glands = produce digestive enzymes & mucin that goes together with water to produce mucous (function)

• Lies in submandibular space

• Lies mainly under mylohyoid muscle 

Submandibular duct = opens up in the middle of the floor of the oral cavity in an elevation called the sublingual caruncle

SUBLINGUAL GLANDS

• OPENS UNDER THE TONGUE

• Located in the sublingual space

• The anterior part of the gland is seromucous 

• The posterior part of gland is purely mucous 

• Sublingual gland has two types of ducts 

1) Major sublingual duct function = joins with submandibular duct to open into sublingual caruncle 

2) Minor sublingual ducts function = open as small holes within the sublingual folds 

LABIAL GLANDS (LIPS) & MINOR GLANDS

• Between the orbicularis oris & the mucous membrane of the lips

• Saliva is secreted by salivary glands which is situated around the oral cavity

TONGUE: BRIEF STRUCTURE & FUNCTION

8 main muscles 4 intrinsic (super longitudinal, inferior longitudinal, vertical, transverse)  4 extrinsic (styloglossus, genioglossus, hyoglossus, palatoglossus)	Mastication  Swallowing Taste Articulation

TONGUE STRUCTURE - GENERAL

• Tongue is a muscle organ, made up by the apex, body & root

• Body

  • Median sulcus: A line running down the middle of the tongue.

  • Sulcus Terminals: A V-shaped groove separating the body from the root.

  • Foramen caecum: A small pit at the tip of the terminal sulcus, a remnant of the thyroglossal duct from fetal development.

  • Lingual tonsil: Lymphatic tissue at the root of the tongue, forming bumps on its surface.

  • Glossoepiglottic folds: Two folds of tissue connecting the tongue to the epiglottis, keeping it in place.

  • Frenulum: A thin band attaching the tongue to the floor of the mouth.

  • Sublingual fold: A ridge on the lower border of the tongue with openings for sublingual gland ducts.

TONGUE STRUCTURE - PAPILLAE

• You have something called lingual papillae. These are rough sensory structures that contains taste buds to sense taste 

1) Filiform papilla - gives the tongue its roughness as it contains a thick layer of epithelial tissue = touch

2) Fungiform papilla = small elevation that carries taste receptor buds

3) Vallate papilla = contains taste buds & located near terminal sulcus 

4) Foliate papilla = contains taste buds & located on lateral regions of tongue

TONGUE STRUCTURE - SENSORY INNERVATION (TASTE & GENERAL)

• Taste sensation for anterior 2/3 of tongue are innervated by VII (facial nerve) 

• General sensation for anterior 2/3 of tongue are innervated by V (Trigeminal) 

• Taste sensation for posterior 1/3 of tongue are innervated by IX (Glossopharyngeal)

• General sensation for the posterior 1/3 of tongue are innervated by IX (Glossopharyngeal)

TONGUE STRUCTURE - EXTRINSIC MUSCLE - GENIOGLOSSUS

Genioglossus

Originates from the superior mental spine of inner mandible

Protrusion (pushes tongue forward) Depresses centre of tongue (all) Retract (anterior fibres) Protrude (posterior fibres)

Cranial Nerve XII (12) = Hypoglossal

TONGUE STRUCTURE - EXTRINSIC MUSCLE - STYLOGLOSSUS

Styloglossus

Originates from styloid process

Retraction (pulls tongue back) Elevates sides of tongue (helps with swallowing)

Cranial Nerve XII (12) = Hypoglossal

TONGUE STRUCTURE - EXTRINSIC MUSCLE - HYOGLOSSUS

Hyoglossus

Hyoid Bone

Depression Pulls sides of tongue down = flattens tongue

Cranial Nerve XII (12) = Hypoglossal

TONGUE STRUCTURE - EXTRINSIC MUSCLE - PALATOGLOSSUS

Palatoglossus

Palatine aponeurosis of soft palate

Elevates posterior tongue Depresses soft palate  Both help to narrow the opening of the pharynx & anterior faucial pillar

Cranial Nerve X (10) = Vagus

TONGUE STRUCTURE - INTRINSIC MUSCLE - SUPER LONGITUDINAL

Super Longitudinal

Run from apex of tongue to root of tongue “t”  “d”

Retracts the tongue Turns the tip up  Forms a trough  Shortens tongue

Cranial Nerve XII (12) = Hypoglossal

TONGUE STRUCTURE - INTRINSIC MUSCLE - INFERIOR LONGITUDINAL

Inferior Longitudinal

Run from apex of tongue to root of tongue “k” “ng”

Retracts tongue Turns tip down Shortens tongue

Cranial Nerve XII (12) = Hypoglossal

TONGUE STRUCTURE - INTRINSIC MUSCLE - TRANSVERSE

Transverse

Arise from median fibrous septum & runs laterally to sides of tongue

Narrows tongue Elongates tongue

Cranial Nerve XII (12) = Hypoglossal

TONGUE STRUCTURE - INTRINSIC MUSCLE - VERTICAL

Vertical

Connects upper with lower surface

Flattens tongue Depresses tongue

Cranial Nerve XII (12) = Hypoglossal

TONGUE DIAGRAMS

FLOOR OF ORAL CAVITY - MYLOHYOID

Floor of the oral cavity consists of 3 main muscles that primarily go from the inner surface of the mandible, to the hyoid bone.

MYLOHYOID MUSCLE (under the geniohyoid) Innervated by Vmand

Partition between oral cavity & rest of neck Action: Raises floor of mouth (elevation)

FLOOR OF ORAL CAVITY - ANTERIOR BELLY OF DIGASTRIC

ANTERIOR BELLY OF DIGASTRIC MUSCLE Innervated by Vmand

Action: Elevates hyoid & depresses mandible

*****SUBLINGUAL GLAND IS ABOVE THESE MUSCLES 

****SUBMANDIBULAR GLAND IS BELOW THESE MUSCLES

FLOOR OF ORAL CAVITY - GENIOHYOID

GENIOHYOID MUSCLE (above mylohyoid) Innervated by hypoglossal

2 genial tubercles behind mandible Action: Draws hyoid anteriorly & posteriorly