Anatomy Relevant to Dentistry 2

Anatomy relevant to dentistry 2

Suprahyoid muscle

·  Responsible for opening mandible

·  Attached to the body of the mandible which connects to the hyoid bone (just above the larynx)

Muscles of mastication

·  Four main groups. Each group is a pair

·  This group is responsible for closing the mandible and aids in chewing

·  Trismus is a condition caused by spasm of the muscles of mastication

·  Each muscle has an origin and an insertion

·  The origin is where the muscle is attached to the skull

·  The insertion is where the muscle extends to the mandible

Masseter muscle

·  A square shaped muscle that pulls mandible upwards and forwards.

·  Important in chewing, clenching and grinding.

Temporal Muscle

·  A fan shaped muscle that retrudes and protrudes mandible.

Medial Pterygoid

·  A square shaped muscle that pulls the mandible forward and upwards.

·  Important when chewing, clenching and grinding

Lateral Pterygoid

·  A cone shaped muscle with 2 origins.

·  Moves mandible form side to side, opens and protrudes.

G ms anat rel to dentistry 2 student notes Page 12 of 12

Muscles of facial expression

·  muscles beneath the skin and face

·  produce a variety of movements and expressions

G ms anat rel to dentistry 2 student notes Page 12 of 12

Saliva

·  Saliva assists in cleansing, digestion, speech and lubrication of the soft tissues.

·  Aids in ejecting or spitting out injurious or distasteful substances

·  Maintain the natural balance of bacteria in the mouth

·  Made up of 99.5% water and 0.5% dissolved substances

0.5% dissolved substances include:

·  calcium and phosphate which are buffering agents and control PH. These minerals assist in the remineralisation of enamel and are also responsible for calculus formation

·  Ptyalin which is an enzyme that breaks down carbohydrates. This is the initial stage of digestion

·  Immunoglobulins which are antibodies and are part of the immune system. These defend against infection

·  Leucocytes which are defences to infection.

Reduced saliva flow

·  Correct term for dry mouth is xerostomia

·  Can be caused by drugs such as diuretics, anti depressants, beta blockers and radiotherapy.

·  Xerostomia can cause halitosis, caries, periodontal disease.

·  Can affect taste and retention of dentures may be difficult.

Increased saliva flow

·  Correct term is ptyalism

·  Can increase calculus formation.

·  Pregnancy and diseases such as Parkinson’s disease may produce this problem

Salivary glands

·  Glands are organs consisting of specialised cells that produce and distribute a substance.

·  Salivary glands produce 2-3 pints of saliva per day.

·  The glands are outside the oral cavity and are connected with the mouth through ducts (canal).

·  These ducts pass the saliva from the gland through to the oral cavity.

·  Saliva secretions are controlled by stimuli such as smell, sight and the thought of food and touch

Parotid Gland

·  Largest of the salivary glands

·  Located between the angle of the mandible and the external ear

·  The duct that carries the saliva from the gland to the oral cavity is the parotid duct (also called Stensens)

·  The duct opens into the oral cavity opposite the buccal surface of the upper first molars where it secretes clear and watery serum

·  Parotid Gland involved in the virus, Mumps

Submandibular Gland

·  Lies beneath the lower jaw

·  The duct that carries the saliva from the gland to the oral cavity is the submandibular duct ( also called the wharton’s duct)

·  The duct opens into the oral cavity below the tongue where it secretes slimy, sticky clear liquid

·  This duct is prone to stones

Sublingual Gland

·  The smallest gland

·  Lies just below the tissue in the floor of the mouth

·  This is further forward than submandibular gland

·  The ducts that carry the saliva from the gland to the oral cavity are the Rivinus ducts. There are 10-20 of these.

·  The ducts enters the oral cavity behind the submandibular duct under the tongue where it secretes mucous saliva

Tongue (Lingua – Latin. Glosso – Greek prefix)

·  Flexible group of muscles that are arranged to change shape, size and position quickly

·  Functions are to assist in swallowing, speech, taste and cleansing

·  Attached to the floor of the mouth by the lingual frenum

·  The tongue has a thick layer of mucous membrane on the top (dorsum) and thinner layer on the bottom.

·  Thick layer has rough surface made by tiny projections called papillae. This enables cleaning.

·  Taste buds are situated on these projections. There are approximately 3000 of them.

·  Thin layer allows the rapid absorption of drugs

·  The tongue is highly vascular which means it has a rich blood supply

·  A sore tongue can indicate anaemia or hormonal disturbances.

Functions of tongue

·  Assists in speech. This is helped along by rugae. The tongue hits off the rugae on the palate to make certain sounds

·  Assists in taste. The taste buds on the tongue identify sweet, sour, salt and bitter

·  Assists in mastication by creating a bolus

·  Assists in swallowing. The voluntary action that propels the bolus to back of the pharynx

·  Assists in cleansing as it dislodges food particles and distributes saliva

Nerve and blood supply

Blood supply to head and neck

·  Main artery which supplies the face and oral tissues is the carotid artery.

·  Blood is drained and returns to the heart from the head and neck by the jugular vein

Nerve supply to oral cavity

·  Nerve - microscopic, cord like structure of fibres that send messages between the central nervous system, body organs, tissues or systems.

Cranial Nerves

·  There are 12 cranial nerves, 4 of which are concerned with the oral cavity

VII cranial nerve (7th)

·  Called the facial nerve

·  Serves part of the tongue, soft palate, the submandibular and sublingual salivary glands and the muscles of facial expression.

·  Bells palsy is a dysfunction of this nerve.

IX cranial nerve (9th)

·  Called the glossopharyngeal nerve.

·  This serves the throat, part of the tongue and the parotid gland

XII cranial nerve (12th)

·  Called the Hypoglossal nerve

·  supplies the muscles of the tongue and floor of mouth

Trigeminal nerve (5th)

·  V Cranial nerve

·  Supplies the teeth

·  Starts as the trigeminal ganglion, then splits into 3: opthalmic, maxillary & mandibular branch

·  Opthalmic branch serves the eyes

·  Maxillary branch has 5 sub branches that serve the upper teeth:

1.  Anterior superior alveolar nerve – labial 1-3

2.  Middle superior alveolar nerve – buccal 4 – 6mb

3.  Posterior superior alveolar nerve – buccal 6db – 8

4.  Naso palatine nerve – serves associated tissues surrounding palatal 1-3

5.  Greater palatine nerve – serves associated tissues surrounding palatal 4-8

·  Mandibular branch sub-divides into 3:

1.  Lingual branch – serves the front of one side of the tongue

2.  Buccal branch serves the buccal soft tissues and stops opposite the premolars

3.  Inferior alveolar nerve. Enters the mandible through the mandibular foramen. Runs through a canal in the mandible to serve the teeth. As it approaches the mental foramen, the nerve splits into 2: incisive nerve carries on through the canal to serve the anterior teeth. The mental nerve exits through the mental foramen and run along the front to serve the chin.

Blood supply

Artery

·  Vessel through which blood passes from the heart to the body.

·  Main artery which supplies the face and oral tissues is the carotid artery.

Veins

·  Drains blood from the head and neck

·  Blood returns to the heart from the head and neck by the jugular vein

G ms anat rel to dentistry 2 student notes Page 12 of 12