The Frontalis Muscle

• The frontalis muscle is part of the scalp muscle called the occipitalfrontalis.
• The frontalis elevates the forehead, giving the face a surprised look, and produces transverse wrinkles in the forehead when one frowns.

The Sublingual Glands

• These are the smallest of the three paired salivary glands and the most deeply situated.
• They are almond-shaped and lie in the floor of the mouth between the mandible and the genioglossus muscle.
• The paired glands unite to form a horseshoe-shaped glandular mass around the lingual frenulum.

• Numerous small ducts (10 to 12) open into the floor of the mouth.
• Sometimes one of the ducts opens into the submandibular duct.

• The nerves the accompany the submandibular and sublingual glands are derived from the lingual and chorda tympani nerves and from the sympathetic nerves.
• The parasympathetic secretomotor fibres are from the submandibular ganglion.

The Masseter Muscle

• This is a quadrangular muscle that covers the lateral aspect of the ramus and the coronoid process of the mandible.

• Origin: inferior border and medial surface of zygomatic arch.
• Insertion: lateral surface of ramus of mandible and its coronoid process.
• Innervation: mandibular nerve via masseteric nerve that enters its deep surface.

• It elevates and protrudes the mandible, closes the jaws and the deep fibres retrude it.

BONE

 A rigid form of CT, Consists of matrix and cells

 Matrix contains:

 organic component 35% collagen fibres

 inorganic salts 65% calcium phosphate (58,5%),  calcium carbonate (6,5%)

2 types of bone - spongy (concellous)

 compact (dense)

 Microscopic elements are the same

 Spongy bone consists of bars (trabeculae) which branch and unite to form a meshwork

 Spaces are filled with bone marrow

 Compact bone appears solid but has microscopic spaces

 In long bones the shaft is compact bone

 And the ends (epiphysis) consists of spongy bone covered with compact bone

Flat bones consists of 2 plates of compact bone with spongy bone in-between

 Periosteum covers the bone

 Endosteum lines marrow cavity and spaces

 These 2 layers play a role in the nutrition of bone tissue

 They constantly supply the bone with new osteoblasts for the repair and growth of bone

Microscopically

 The basic structural unit of bone is the Haversian system or osteon

 An osteon consists of a central Haversian canal

- In which lies vessels nerves and loose CT

- Around the central canal lies rings of lacunae

- A lacuna is a space in the matrix in which lies the osteocyte

- The lacunae are connected through canaliculi which radiate from the lacunae

- In the canaliculi are the processes of the osteocytes

- The canaliculi link up with one another and also with the Haversian canal

- The processes communicate with one another in the canaliculi through gap junctions

- Between two adjacent rows of lacunae lie the lamellae, 5-7µm thick

- In three dimensions the Haversian systems are cylindrical

- The collagen fibres lie in a spiral in the lamellae

- Perpendicular to the Haversian canals are the Volkman's canals

- They link up with the marrow cavity and the Haversian canals

- Some lamellae do not form part of a Haversian system

- They are the:

- Inner circumferential lamellae - around the marrow cavity

- Outer circumferential lamellae - underneath the outer surface of the bone

- Interstitial lamellae - between the osteons

Endosteum

Lines all cavities like marrow spaces, Haversian- and Volkman's canals

Consists of a single layer of squamous osteoprogenitor cells with a thin reticular CT layer underneath it

Continuous with the inner layer of periosteum

Covers the trabeculae of spongy bone

Cells differentiate into osteoblasts (like the cells of the periosteum)

Periosteum

 Formed by tough CT

 2 layers

Outer fibrous layer:  Thickest, Contains collagen fibres,

Some fibres enter the bone - called Sharpey's fibres

Contains blood vessels.

Also fibrocytes and the other cells found in common CT

Inner cellular layer

Flattened cells (continuous with the endosteum)

Can divide and differentiate into osteoprogenitor cells

spindle shaped

little amount of rough EPR

poorly developed Golgi complex

play a prominent role in bone growth and repair

Osteoblasts

Oval in shape, Have thin processes, Rough EPR in one part of the cell (basophilic)

On the other side is the nucleus, Golgi and the centrioles in the middle, Form matrix

Become trapped in the matrix

Osteocytes

Mature cells, Less basophilic than the osteoblasts, Lie trapped in the lacunae, Their processes lie in the canaliculi, Processes communicate with one another through gap junctions, Substances (nutrients, waste products) are passed on from cell to cell

Osteoclasts

 Very large,  Multinucleate (up to 50),  On inner and outer surface of bone,  Lie in depressions on the surface called Howships lacunae,  The cell surface facing the bone has short irregular processes

Acidophylic

 Has many lysosomes, polyribosomes and rough EPR

 Lysosomal enzymes are secreted to digest the bone

 Resorbs the organic part of bone

Histogenesis

Two types of bone development.

- intramembranous ossification

- endochondral ossification

In both these types of bone development temporary primary bone is deposited which is soon replaced by secondary bone. Primary bone has more osteocytes and the mineral content is lower.

The Palate

• The palate forms the arched roof of the mouth and the floor of the nasal cavities.
• The palate consists of two regions: the anterior 2/3 or bony part, called the hard palate, and the mobile posterior 1/3 or fibromuscular part, known as the soft palate.

The Hard Palate

• The anterior bony part of the palate is formed by the palatine process of the maxillae and the horizontal plates of the palatine bones.

• Anteriorly and laterally, the hard palate is bounded by the alveolar processes and the gingivae.
• Posteriorly, the hard palate is continuous with the soft palate.

• The incisive foramen is the mouth of the incisive canal.
• This foramen is located posterior to the maxillary central incisor teeth.
• This foramen is the common opening for the right and left incisive canals.
• The incisive canal and foramen transmit the nasopalatine nerve and the terminal branches of the sphenopalatine artery.

• Medial to the third molar tooth, the greater palatine foramen pierces the lateral border of the bony palate.
• The greater palatine vessels and nerve emerge from this foramen and run anteriorly into two grooves on the palate.

• The lesser palatine foramen transmits the lesser palatine nerve and vessels.
• This runs to the soft palate and adjacent structures.

The Soft Palate

• This is the posterior curtain-like part, and has no bony support. It does, however, contain a membranous aponeurosis.
• The soft palate, or velum palatinum (L. velum, veil), is a movable, fibromuscular fold that is attached to the posterior edge of the hard palate.
• It extends posteroinferiorly to a curved free margin from which hangs a conical process, the uvula (L. uva, grape).

• The soft palate separates the nasopharynx superiorly and the oropharynx inferiorly.

• During swallowing the soft palate moves posteriorly against the wall of the pharynx, preventing the regurgitation of food into the nasal cavity.

• Laterally, the soft palate is continuous with the wall of the pharynx and is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal folds.

• The soft palate is strengthened by the palatine aponeurosis, formed by the expanded tendon of the tensor veli palatini muscle.
• This aponeurosis attaches to the posterior margin of the hard palate.