Skull bones

• 26 bones: 22 bones + hyoid (small bone in neck for swallowing) + 3 auditory ossicles (middle ear: incus, malleus, stapes)
• 21 bones: tightly connected; mandible is freely mobile at temperomandibular joint (synovial)
• connective-tissue interface b/w bones = suture
• bones – mandible = cranium
• cranium
  • neurocranium: covers brain anteriorly, laterally and posteriorly
  • brain supported by bones of basicranium
    • also contributes to interorbital region; b/w eyes and superior to nasal passages
  • viscerocranium/splanchnocranium: bones of face
• sutures
  • coronal: separates frontal from parietals
  • sagittal: separates two parietal bones
  • lambdoidal: separates parietal form occipital
  • squamosal: b/w temporal and parietal; overlapping sutures
  • At birth: 2 frontal bones which eventually fuse; metopic suture disappears

Cranial Cavities: 5 major cavities

            Endocranial, left and right orbits, nasal cavities, oral cavity, middle ear cavities

Endocranial cavity

• contains brain, meninges, cerebrospinal fluid, brain’s vascular supply and most proximal portion of cranial nerves
• enclosed by neurocranium and basicranium
• basicranium: foramina for neurovascular bundles
• foramen magnum: spinal cord exit
• floor of endocranial cavity divide into fossae
  • anterior: frontal lobes of brain
  • middle: pair temporal lobes
  • posterior: cerebellum and brainstem

The Submandibular Glands

• Each of these U-shaped salivary glands is about the size of a thumb and lies along the body of the mandible.
• It is partly superior and partly inferior to the posterior 1/2 of the base of the mandible.
• It is partly superficial and partly deep to the mylohyoid muscle.

• The submandibular duct arises from the portion of the gland that lies between the mylohyoid and hyoglossus muscle.

• The duct passes deep and then superficial to the lingual nerve.
• It opens by one to three orifices on a small sublingual papilla beside the lingual frenulum.

• The submandibular gland is supplied by parasympathetic, secretomotor fibres from the submandibular ganglion (preganglionic fibres from the chorda tympani via the lingual nerve).

•  Provides a rigid support system
• Protects delicate structures (e. g., the protection provided by the bones of the vertebral column to the spinal cord)
• Bones supply calcium to the blood; are involved In the formation of blood cells (hemopoiesis)
• Bones serve as the basis of attachment of muscles; form levers in the joint areas, aIlowing movement

- The forehead is formed by the smooth, broad, convex plate of bone called the frontal squama.
- In foetal skulls, the halves of the frontal squama are divided by a metopic suture.
- In most people, the halves of the frontal bone begin to fuse during infancy and the suture between is usually not visible after 6 years of age.
- The frontal bone forms the thin roof of the orbits (eye sockets).
- Just superior to and parallel with each supraorbital margin is a bony ridge, the superciliary arch, which overlies the frontal sinus. This arch is more pronounced in males.
- Between these arches there is a gently, rounded, medial elevation called the gabella; this term derives from the Latin word glabellus meaning smooth and hairless. In most people, the skin over the gabella is hairless.
-The slight prominences of the forehead on each side, superior to the superciliary arches, are called frontal eminences (tubers).
- The supraorbital foramen (occasionally a notch), which transmits the supraorbital vessels and nerve is located in the medial part of the supraorbital margin.
- The frontal bone articulates with the two parietal bones at the coronal suture.
-It also articulates with the nasal bones at the frontonasal suture. At the point where this suture crosses the internasal suture in the medial plane, there is an anthropological landmark called the nasion . The depression is located at the root of the nose, where it joins the cranium.
- The frontal bone also articulates with the zygomatic, lacrimal, ethmoid, and sphenoid bones.
In about 8% of adult skulls, a remnant of the inferior part of the metopic (interfrontal) suture is visible. It may be mistaken in radiographs for a fracture line by inexperienced observers.
- The superciliary arches are relatively sharp ridges of bone and a blow to them may lacerate the skin and cause bleeding.
- Bruising of the skin over a superciliary arch causes tissue fluid and blood to accumulate in the surrounding connective tissue, which gravitates into the upper eyelid and around the eye. This results in swelling and a "black eye".
- Compression of the supraorbital nerve as it emerges from its foramen causes considerable pain, a fact that may be used by anaesthesiologists and anaesthetists to determine the depth of anaesthesia and by physicians attempting to arouse a moribund patient.

Internal Ear

• Osseous labyrinth: a complex system of cavities in the substance of the petrous bone.
• Membranous labyrinth: filled with endolymph, bathed in perilymph.

Muscles of the Soft Palate

The Levator Veli Palatini (Levator Palati)

• Superior attachment: cartilage of the auditory tube and petrous part of temporal bone.
• Inferior attachment: palatine aponeurosis.
• Innervation: pharyngeal branch of vagus via pharyngeal plexus.
• This cylindrical muscle runs inferoanteriorly, spreading out in the soft palate, where it attaches to the superior surface of the palatine aponeurosis.
• It elevates the soft palate, drawing it superiorly and posteriorly.
• It also opens the auditory tube to equalise air pressure in the middle ear and pharynx.

The Tensor Veli Palatini (Tensor Palati)

• Superior attachment: scaphoid fossa of medial pterygoid plate, spine of sphenoid bone, and cartilage of auditory tube.
• Inferior attachment: palatine aponeurosis.
• Innervation: medial pterygoid nerve (a branch of the mandibular nerve).
• This thin, triangular muscle passes inferiorly, and hooks around the hamulus of the medial pterygoid plate.
• It then inserts into the palatine aponeurosis.
• This muscle tenses the soft palate by using the hamulus as a pulley.
• It also pulls the membranous portion of the auditory tube open to equalise air pressure of the middle ear and pharynx.

The Palatoglossus Muscle

• Superior attachment: palatine aponeurosis.
• Inferior attachment: side of tongue.
• Innervation: cranial part of accessory nerve (CN XI) through the pharyngeal branch of vagus (CN X) via the pharyngeal plexus.
• This muscle, covered by mucous membrane, forms the palatoglossal arch.
• The palatoglossus elevates the posterior part of the tongue and draws the soft palate inferiorly onto the tongue.

The Palatopharyngeus Muscle

• Superior attachment: hard palate and palatine aponeurosis.
• Inferior attachment: lateral wall of pharynx.
• Innervation: cranial part of accessory nerve (CN XI) through the pharyngeal branch of vagus (CN X) via the pharyngeal plexus.
• This thin, flat muscle is covered with mucous membrane to form the palatopharyngeal arch.
• It passes posteroinferiorly in this arch.
• This muscle tenses the soft palate and pulls the walls of the pharynx superiorly, anteriorly and medially during swallowing.

The Musculus Uvulae

• Superior attachment: posterior nasal spine and palatine aponeurosis.
• Inferior attachment: mucosa of uvula.
• Innervation: cranial part of accessory through the pharyngeal branch of vagus, via the pharyngeal plexus.
• It passes posteriorly on each side of the median plane and inserts into the mucosa of the uvula.
• When the muscle contracts, it shortens the uvula and pulls it superiorly.