Anatomy Essentials: Bones, Muscles, and Sensory Organs

1. Vomer Bone

Shape: Part of the postero-inferior nasal septum. Anatomical Features: Alae (wings), ridge, and furrow for choanal articulation with the vomer.

2. Sutures and Fontanelles

The bones of the cranial vault are joined by synfibrosis. We distinguish:

• Coronal suture
• Sagittal suture
• Squamous sutures
• Metopic suture
• Lambdoid suture

Schindylesis: Vomer and sphenoid crest articulation.

In newborns, skull bones are not yet firmly united at the sutures, leaving spaces called fontanelles. There are six:

• Bregmatic: Diamond-shaped, between the parietal and frontal bones.
• Lambdoid: Triangle-shaped, between the sagittal and lambdoid sutures.
• Pterygoid: Located at the junction of the frontal, parietal, temporal, and sphenoid bones.
• Asteroid: Star-shaped, between the parietal, occipital, and temporal bones.

3. Temporomandibular Joint (TMJ)

Type: Condylar joint.

Articular Surfaces:

• Maxilla: Condyle.
• Temporal: Mandibular fossa and articular tubercle.

Movements Allowed: Elevation and depression of the jaw, laterality (side-to-side movement), protraction and retraction.

4. Masticatory Muscles

• Muscles that close the mouth:
  • Temporalis: Originates from the temporal fossa and inserts on the coronoid process of the mandible.
  • Masseter: A powerful muscle that elevates the mandible.
• Muscles that allow lateral movement:
  • Medial Pterygoid: Located at the angle and ramus of the mandible.
  • Lateral Pterygoid: Inserts on the condyle of the mandible.

5. Orbits

Pyramid-shaped structures with a base anteriorly and an apex posteriorly.

• Roof: Frontal bone.
• Floor: Maxilla, zygomatic, and palatine bones.
• Medial Wall: Maxilla, lacrimal, ethmoid, and sphenoid bones.
• Lateral Wall: Sphenoid (greater wing) and zygomatic bones.

6. Nasal Cavity

• Anterior Openings (Nares): Nostrils with hairs to filter air.
• Posterior Openings (Choanae): Communicate with the nasopharynx.
• Roof: Frontal, ethmoid, and sphenoid bones.
• Floor: Maxilla and palatine bones.
• Lateral Wall: Maxilla, ethmoid, and palatine bones (inferior nasal concha) to warm and humidify air.
• Septum: Ethmoid, vomer, and cartilage.

Draining the Nasal Sinuses

Air cavities that act as resonators and are lined with mucosa containing mucus-producing epithelium, continuous with the nasal cavity (can be complicated by sinusitis).

Sinuses: Frontal, maxillary, ethmoid, and sphenoid.

Nasolacrimal Duct: Drains into the nasal cavity.

7. Oral Cavity (Mouth)

Dilated upper part of the digestive tract.

• Parts: Vestibule (between lips/cheeks and teeth) and oral cavity proper (separated by teeth).
• Roof: Hard palate (maxilla and palatine bones).
• Soft Palate: Anterior and posterior pillars.
• Floor: Tongue (muscle + taste buds), mucous membrane covering various muscles.

Ducts of salivary glands empty into the oral cavity.

Functions: Mastication, digestion (saliva), breathing, and phonation.

8. Teeth

Types and Functions:

• Incisors: Cutting.
• Canines: Tearing.
• Premolars and Molars: Grinding.

Parts: Crown, neck, and root.

• Deciduous (Milk) Teeth: 20 teeth (erupt starting at 6 months). Each jaw has 4 incisors, 2 canines, and 4 molars.
• Permanent Teeth: 32 teeth (erupt starting at 5 or 6 years). Each jaw has 4 incisors, 2 canines, 4 premolars, and 6 molars.

9. Salivary Glands

Accessory glands of the digestive tract, located outside it, that secrete saliva through ducts.

Saliva Production: Mucus moistens food for easier passage through the digestive tract, and salivary amylase begins carbohydrate digestion.

Major Salivary Glands:

• Parotid: Located in front of and below the ear; the Stensen's duct opens near the second upper molar.
• Submandibular: Located inside the angle of the jaw; Wharton's duct opens next to the frenulum of the tongue.
• Sublingual: Multiple small ducts open into the floor of the mouth, posterior to the chin.

10. Sense of Sight

Essential Organs: Eyeball, optic nerve, and visual centers in the brain.