Anatomy of Hard and Soft Palate

The hard and soft palate is composed of bone and soft tissue. This article details structures, neuromuscular supply and abnormal anatomy.

Hard Palate

Bones

The primary and secondary hard palate is created by 2 bones: maxilla and palatine.

• Primary palate is anterior to the incisive foramen and is formed by the lip, nostril sill, alveolus, premaxillary portion of the maxilla.
• Secondary palate is posterior to the incisive foramen and is formed by the palatal processes of maxilla (anterior), palatine bone (posterior) and soft palate.

These hard palate bones are visualised in the image below.

Mucosa

A mucoperiosteal layer covers the hard palate in 3 zones

1. Central Zone: thin palatal mucosa on the horizontal palate that grows the shelves before they rotate horizontally.
2. Middle Zone: thick maxillary mucosa on the curved aspect of the palate that assists with maxillary growth.
3. Outer Zone: gingival mucosa adjacent to the teeth

These mucosal zones of the palate are visualised in the image below.

Foramina/Canals

There are three main portals into the hard palate:

1. Incisive foramen: course of the nasopalatine nerve.
2. Greater palatine foramen: located medial to 3rd molar tooth, location of greater palatine nerve and vessels
3. Lesser palatine foramen: located in the pyramidal process of the palatine bone and is the course of the lesser palatine nerve.

Soft Palate

The soft palate is a muscular structure that separates the nasopharynx from the oropharynx. There are 5 paired soft palate muscles. They are all innervated by the pharyngeal plexus (IX, X and cranial part of XI), except for tensor veli palitini (trigeminal) and muscular uvulae (lesser palatine nerve).

Tensor Veli Palitini (TVP)

• Origin: membranous wall of the Eustachian tube and sphenoid bone
• Insertion: posterior hard palate
• Function: form palatal aponeurosis, eustachian tube opening

Levator Veli Palitini

This is the main functional muscle of the soft palate.

• Origin: temporal bone and eustachian tube
• Insertion: posterior palatine aponeurosis
• Function: forms muscle sling for posterior elevation of the soft palate, which closes the space between the nasopharynx and oropharynx.

Muscularis uvulae

This muscle may be absent in patients with a submucous cleft.

• Origin + Insertion: found within the uvulae (tip, it's in the name!)
• Function: elevates and shorterns the uvulae

Palatopharyngeus

• Origin: posterior pharynx (superior thyroid cartilage, superior pharyngeal constrictor).
• Insertion: anterior velum (oral side of levator)
• Function: depresses the soft palate, elevates and constricts the oropharnyx.

Palatoglossus

• Origin: tongue (tip, it's in the name!)
• Insertion: velum (more specifically, the LVP)
• Function: depresses the soft palate and pulls anteriorly.

Other muscles involved in the pharyngeal movement include:

• Superior Pharyngeal Constrictor: movement of lateral pharyngeal wall.
• Salpingopharyngeus: does not contribute to velopharyngeal closure
• Stylopharyngeus: does not contribute to velopharyngeal closure

Neurovascular Supply

The palate receives arterial supply primarily from the greater palatine artery and the lesser palatine artery through the greater and lesser palatine foramen.

Collateral supply is received from other arteries, as detailed below. Venous drainage is into the pterygoid venous plexus.

Hard Palate

Greater Palatine Nerve and Artery

• Origin: Trigeminal nerve & Maxillary Artery (via descending palatine artery)
• Function: hard palate sensation and vascular supply
• Location: travels through the greater palatine foramen

Nasopalatine Nerve and Artery

• Origin: Trigeminal Nerve and Maxillary artery via the sphenopalatine artery
• Location: joins greater palatine artery and nerve at the incisive foramen
• Function: sensation and vascular supply to the premaxilla

Anterior and Posterior Superior alveolar arteries

• Origin: anterior via maxillary and infraorbital, posterior via maxillary artery
• Function: Supplies anterior and posterior alveoli

Soft Palate

Lesser Palatine

• Origin: maxillary artery via desceding palatine artery and trigeminal nerve
• Function: soft palate sensation and vascular supply
• Location: travel through the lesser palatine formen

Soft palate also receives a major blood supply from the asecending pharygngeal (from external carotid artery) and ascending palatine arteries (from facial artery).

Embryology

The palate begins to grow intrauterine at weeks 7-10 of gestation

1. Head and mandible grows.
2. Tongue descends downwards.
3. Palatal shelves rotate upwards from a vertical to a horizontal position.
4. Vomer and palatal shelves fuse at incisive foramen via epithelial apoptosis.
5. Primary and secondary palate fuse proximally and distally away from incisive foramen, respectively.

Males and right-sided palatal shelves become horizontal before females and left-sided palate shelves. This can explain the increased incidence of females and left-sided clefts.

Cleft Palate Anatomy

Cleft palate is a spectrum from mild bifid uvula's to bilateral clefts. Generally speaking, there are abnormal insertions of the tensor and levator veli palitini:

• TVP: inserts into bony margins of the cleft instead of the posterior border of the hard palate.
• LVP: inserts into TVP aponeurosis

These muscles run parallel to the cleft margin and do not join in the middle to form a sling. As a result, there is dysfunction of the velopharyngeal and eustachian tubes.