The Articular Capsule

• The capsule of this joint is loose.
• The thin fibrous capsule is attached to the margins of the articular area on the temporal bone and around the neck of the mandible.

Gross anatomy-study of structures that can be identified with the naked eye; usually involves the use of cadavers

• Microscopic anatomy (histology)-study of cells that compose tissues and organs; involves the use of a microscope to study the details of the species
• Developmental anatomy (embryology)-study of an individual from beginning as a single cell to birth
• Comparative anatomy -comparative study of the animal structure in regard to similar organs or regions

Muscles Around the Mouth

• The sphincter of the mouth is orbicularis oris and the dilator muscles radiate outward from the lips like the spokes of a wheel.

Orbicularis Oris Muscle

• This muscle encircles the mouth and is the sphincter of the oral aperture
• This muscle (1) closes the lips, (2) protrudes them and (3) compresses them against the teeth.
• It plays an important role in articulation and mastication. Together with the buccinator muscle, it helps to hold the food between the teeth during mastication.

Zygomaticus Major Muscle

• It extends from the zygomatic bone to the angle of the mouth.
• It draws the corner of the moth superolaterally during smiling and laughing.

Zygomaticus Minor Muscle

• This is a narrow slip of muscle, and passes obliquely from the zygomatic bone to the orbicularis oris.
• It helps raise the upper lip when showing contempt or to deepen the nasolabial sulcus when showing sadness.

The Buccinator Muscle

• This is a thin, flat, rectangular muscle.
• It is attached laterally to the alveolar processes of the maxilla and mandible, opposite the molar teeth and the pterygomandibular raphe.
• Medially, its fibres mingle with those of orbicularis oris.Innervation: the buccal branch of facial.

• It aids mastication and swallowing by pushing the cheeks against the molar teeth during chewing.

The Medial Wall of the Orbit 

• This wall is paper-thin and is formed by the orbital lamina or lamina papyracea of the ethmoid bone, along with contributions from the frontal, lacrimal, and sphenoid bones (L. papyraceus, "made of papyrus" or parchment paper).

• There is a vertical lacrimal groove in the medial wall, which is formed anteriorly by the maxilla and posteriorly by the lacrimal bone.
• It forms a fossa for the lacrimal sac and the adjacent part of the nasolacrimal duct.

• Along the suture between the ethmoid and frontal bones are two small foramina; the anterior and posterior ethmoidal foramina.
• These transmit nerves and vessels of the same name.

The Scalp

• The scalp consists of five layers of soft tissue.
• It extends from the superior nuchal line on the posterior aspect of the skull of the supraorbital margins.
• Laterally, the scalp extends into the temporal fossa to the level of the zygomatic arches.

Layers of the Scalp

• The scalp proper is composed of three fused layers. It is separated from the pericranium by loose connective tissue.
• Because of this potential areolar cleavage plane, the scalp is fairly mobile.
• Each letter of the word "S C A L P" serves as a memory key for one of the layers of the scalp: Skin, Connective Tissue, Aponeurosis Epicranialis, Loose Areolar Tissue and Pericranium.

Layer 1: Skin

• Hair covers the scalp in most people.
• The skin of the scalp is thin, especially in elderly people, except in the occipital region.
• The skin contains many sweat and sebaceous glands and hair follicles.
• The skin of the scalp has an abundant arterial supply and good venous and lymphatic drainage systems.

Layer 2: Connective Tissue

• This is a thick, subcutaneous layer of connective tissue and is richly vascularised and innervated.
• It attaches the skin to the third layer of the scalp.
• Fat is enclosed in lobules between the connective fibres.

Layer 3: Aponeurosis Epicranialis

• This is a strong membranous sheet that covers the superior aspect of the cranium.
• This aponeurosis is the membranous tendon of the fleshy bellies of the epicranius muscle.

• The epicranius muscle consists of four parts: two occipital bellies, occipitalis and two frontal bellies, frontalis that are connected by the epicranial aponeurosis. 

Layer 4: Loose Areolar Tissue

• This is a subaponeurotic layer or areolar or loose connective tissue.
• It is somewhat like a sponge because it contains innumerable potential spaces that are capable of being distended by fluid.
• It is this layer that allows free movement of the scalp proper, composed of layers 1-3.

Layer 5: Pericranium

• This is a dense layer of specialised connective tissue.
• The pericranium is firmly attached to the bones by connective tissue fibres called Sharpey’s fibres, however, they can be fairly easily stripped from the cranial bones of living persons, except where they are continuous with the fibrous tissues of the cranial sutures.

Initially, four clefts exist; however, only one gives rise to a definite structure in adults.