•  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 Tongue

• The tongue (L. lingua; G. glossa) is a highly mobile muscular organ that can vary greatly in shape.
• It consists of three parts, a root, body, and tip.

• The tongue is concerned with mastication, taste, deglutition (swallowing), articulation (speech), and oral cleansing.
• Its main functions are squeezing food into the pharynx when swallowing, and forming words during speech.

Gross Features of the Tongue

• The dorsum of the tongue is divided by a V-shaped sulcus terminalis into anterior oral (presulcal) and posterior pharyngeal (postsulcal) parts.
• The apex of the V is posterior and the two limbs diverge anteriorly.
• The oral part forms about 2/3 of the tongue and the pharyngeal part forms about 1/3.

Oral Part of the Tongue

• This part is freely movable, but it is loosely attached to the floor of the mouth by the lingual frenulum.

• On each side of the frenulum is a deep lingual vein, visible as a blue line.
• It begins at the tip of the tongue and runs posteriorly.
• All the veins on one side of the tongue unite at the posterior border of the hyoglossus muscle to form the lingual vein, which joins the facial vein or the internal jugular vein.

• On the dorsum of the oral part of the tongue is a median groove.
• This groove represents the site of fusion of the distal tongue buds during embryonic development.

The Lingual Papillae and Taste Buds

• The filiform papillae (L. filum, thread) are numerous, rough, and thread-like.
• They are arranged in rows parallel to the sulcus terminalis.

• The fungiform papillae are small and mushroom-shaped.
• They usually appear are pink or red spots.

• The vallate (circumvallate) papillae are surrounded by a deep, circular trench (trough), the walls of which are studded with taste buds.

• The foliate papillae are small lateral folds of lingual mucosa that are poorly formed in humans.

• The vallate, foliate and most of the fungiform papillae contain taste receptors, which are located in the taste buds.

The Pharyngeal Part of the Tongue

• This part lies posterior to the sulcus terminalis and palatoglossal arches.
• Its mucous membrane has no papillae.

• The underlying nodules of lymphoid tissue give this part of the tongue a cobblestone appearance.
• The lymphoid nodules (lingual follicles) are collectively known as the lingual tonsil.

The Inferior Wall of the Orbit

• The thin inferior wall of the orbit or the floor is formed mainly by the orbital surface of the maxilla and partly by the zygomatic bone, and orbital process of the palatine bone.

• The floor of the orbit forms the roof of the maxillary sinus.

• The floor is partly separated from the lateral wall of the orbit by the inferior orbital fissure.

->The two parietal bones (L. paries, wall) form large parts of the walls of the calvaria.
->On the outside of these smooth convex bones, there are slight elevations near the centre called parietal eminences.
->The middle of the lateral surfaces of the parietal bones is crossed by two curved lines, the superior and inferior temporal lines.
->The superior temporal line indicates an attachment of the temporal fascia; the inferior temporal line marks the superior limit of the temporalis muscle.
->The parietal bones articulate with each other in the median plane at the sagittal suture. The medial plane of the body passes through the sagittal suture.
->The inverted V-shaped suture between the parietal bones and the occipital bones is called the lambdoid suture because of its resemblance to the letter lambda in the Greek alphabet.
->The point where the parietal and occipital bones join is a useful reference point called the lambda. It can be felt as a depression in some people.
->In addition to articulation with each other and the frontal and occipital bones, the parietal bones articulate with the temporal bones and the greater wings of the sphenoid bone.
->In foetal and infant skulls, the bones of the calvaria are separated by dense connective tissue membranes at sutures.
->The large fibrous area where several sutures meet are called fonticuli or fontanelles.
->The softness of these bones and looseness of their connections at these sutures enable the calvaria to undergo changes of shape during birth called molding. Within a day or so after birth, the shape of the infant’s calvaria returns to normal.
->The loose construction of the new-born calvaria also allows the skull to enlarge and undergo remodelling during infancy and childhood.

->Relationships between the various bones are constantly changing during the active growth period.
->The increase in the size of the cranium is greatest during the first 2 years, the period of most rapid postnatal growth of the brain.
->The cranium normally increases in capacity until about 15 or 16 years of age; thereafter the cranium usually increases only slightly in size as its bones thicken for 3 to 4 years.