Face
External nose
Lips, cheeks, and teeth
The lips and cheeks are composed primarily of muscle and fat. They are covered on the external surface with skin, and lined on the internal surface with mucous membrane. The space that separates the lips and cheeks from the teeth and gums is the vestibule of the mouth. A full set of adult teeth consists of 32 teeth, 8 in each half of the jaw. From before backwards, these are: two incisors, one canine, two premolars, and three molars. There are 20 teeth in the primary dentition, i.e. five in each half of the jaw: two incisors, one canine, and two molars, also called ‘milk’ molars. The oral fissure, the gap or space between the lips, is opposite the biting edge of the upper teeth. The corner or angle of the mouth is opposite the first premolar tooth. The median groove on the external surface of the upper lip is the philtrum. In the midline, the internal surface of each lip is attached to the gum by a fold of mucous membrane—the frenulum of the lip.
Identify the horizontal body of the mandible below the lower lip and cheeks. Follow the lower border of the mandible backwards to its angle. The wide, flat plate of bone which extends superiorly from the posterior part of the body is the ramus of the mandible. The ramus of the mandible is covered laterally by the masseter muscle, so that only its posterior border is felt easily. The condylar process projects upwards from the posterior margin of the ramus and forms the neck and head of the mandible. The neck lies immediately anterior to the lobule of the auricle; the head lies anterior to the tragus. Place your fingertip in front of your own tragus, and open your mouth. The fingertip slips into a shallow depression created when the head of the mandible glides downwards and forwards. Note that the mouth cannot be closed while the finger remains in this fossa. The two halves of the mandible are united in the midline by the symphysis menti. The mental foramen is felt as a slight depression on the anterior surface of the mandible, about 4 cm from the midline, halfway between the edge of the gum and the lower border of the mandible [Fig. 4.2].
Palpate the zygomatic arch which extends over the interval between the ear and the eye. The narrow posterior part is formed by the zygomatic process of the temporal bone, and the anterior part by the zygomatic bone [see Fig. 3.4].
The bony structure of the orbit has been described in part in Chapter 3. Palpate the orbital margins on yourself, and find: (1) the supra-orbital notch on the highest point of the superior margin, about 2.5 cm from the midline; and (2) the frontozygomatic suture at the supero-lateral angle [see Figs. 3.1, 3.4].
The hairy skin above the supra-orbital margin is the eyebrow. Over its medial end is a curved ridge of bone—the superciliary arch. This is well formed only in males and is separated from its fellow on the other side by a smooth median area—the glabella.
The white of the eye is the sclera. The transparent part of the front of the eye is the cornea. The coloured iris (usually black or dark brown) is seen through the cornea and has a dark, circular central aperture—the pupil. The visible part of the sclera is covered with a moist, transparent membrane—the conjunctiva. The conjunctiva passes from the sclera on to the deep surface of the eyelids. The reflection of the conjunctiva on to the eyelids is the fornix of the conjunctiva, and the entire conjunctiva encloses the conjunctival sac. The sac opens anteriorly between the eyelids through the palpebral fissure [Fig. 4.3].
The eyelids or palpebrae are folds which protect the front of the eye. Each time we blink, the eyelids moisten the exposed surface of the eyeball by spreading lacrimal fluid over it. The upper lid is larger and more mobile than the lower one, and the upper conjunctival fornix is much deeper. When the eyes are closed, the palpebral fissure is nearly horizontal and lies opposite the lower margin of the cornea. When the eyes are open, the margins of the eyelids overlap the cornea slightly, the upper eyelid more than the lower.
At the medial angle of the eye is a small, triangular area known as the lacus lacrimalis, with a reddish elevation—the lacrimal caruncle—near its centre. The lacus carries a few fine hairs which filter the lacrimal fluid passing to the lacrimal canaliculi. Just lateral to the lacus is a small, vertical fold of conjunctiva—the plica semilunaris [Fig. 4.3].
The lower eyelid is easily everted by pulling down the skin below it, and the lower fornix is exposed by turning the eyeball upwards. The upper lid is difficult to evert because of the rigid tarsal plate buried in it. Once everted, the upper eyelid tends to remain so. Even with the upper eyelid everted, the deep superior fornix is not exposed.
Eyelashes (cilia) project from the anterior edge of the free margin of the eyelid. On the deep surface of the eyelids are a number of yellowish, parallel streaks produced by the tarsal glands [Fig. 4.3]. The ducts of these glands open near the posterior edge of the free margin of the eyelids. The free margin of the lids is rounded medially and has a small elevation—the lacrimal papilla. Each papilla is surmounted by a tiny aperture—the lacrimal punctum. The puncta lead into the lacrimal canaliculus which drains the lacrimal fluid from the conjunctival sac. Note that the puncta face posteriorly into the conjunctival sac, and that the eyelids move medially when the eye is forcibly closed. This action moves the lacrimal fluid towards the puncta at the medial angle of the eye.
Press a fingertip on the skin between the nose and the medial angle of the eye and feel the rounded, horizontal cord—the medial palpebral ligament. This ligament connects the upper and lower eyelids (and their muscle the orbicularis oculi) to the medial margin of the orbit. If the eyelids are gently pulled laterally, the medial palpebral ligament is more easily felt and may be seen as a small skin ridge.
Nasal Cavity
The term ‘nose’ includes the paired nasal cavities which extend posteriorly from the nostrils to the pharynx. The mobile anterior part of the external nose consists of skin and cartilage. The rigid upper part—the bridge of the nose—is formed by the two nasal bones and the two frontal processes of the maxillae [see Fig. 3.1]. The skin is adherent to the cartilages but is mobile over the bones. The part of the nasal cavity immediately above each nostril is the vestibule of the nose. The vestibule is lined by hairy skin, and its lateral wall is expanded to form the ala of the nose.
The lips and cheeks are composed primarily of muscle and fat. They are covered on the external surface with skin, and lined on the internal surface with mucous membrane. The space that separates the lips and cheeks from the teeth and gums is the vestibule of the mouth. A full set of adult teeth consists of 32 teeth, 8 in each half of the jaw. From before backwards, these are: two incisors, one canine, two premolars, and three molars. There are 20 teeth in the primary dentition, i.e. five in each half of the jaw: two incisors, one canine, and two molars, also called ‘milk’ molars. The oral fissure, the gap or space between the lips, is opposite the biting edge of the upper teeth. The corner or angle of the mouth is opposite the first premolar tooth. The median groove on the external surface of the upper lip is the philtrum. In the midline, the internal surface of each lip is attached to the gum by a fold of mucous membrane—the frenulum of the lip.
Identify the horizontal body of the mandible below the lower lip and cheeks. Follow the lower border of the mandible backwards to its angle. The wide, flat plate of bone which extends superiorly from the posterior part of the body is the ramus of the mandible. The ramus of the mandible is covered laterally by the masseter muscle, so that only its posterior border is felt easily. The condylar process projects upwards from the posterior margin of the ramus and forms the neck and head of the mandible. The neck lies immediately anterior to the lobule of the auricle; the head lies anterior to the tragus. Place your fingertip in front of your own tragus, and open your mouth. The fingertip slips into a shallow depression created when the head of the mandible glides downwards and forwards. Note that the mouth cannot be closed while the finger remains in this fossa. The two halves of the mandible are united in the midline by the symphysis menti. The mental foramen is felt as a slight depression on the anterior surface of the mandible, about 4 cm from the midline, halfway between the edge of the gum and the lower border of the mandible [Fig. 4.2].
Palpate the zygomatic arch which extends over the interval between the ear and the eye. The narrow posterior part is formed by the zygomatic process of the temporal bone, and the anterior part by the zygomatic bone [see Fig. 3.4].
The bony structure of the orbit has been described in part in Chapter 3. Palpate the orbital margins on yourself, and find: (1) the supra-orbital notch on the highest point of the superior margin, about 2.5 cm from the midline; and (2) the frontozygomatic suture at the supero-lateral angle [see Figs. 3.1, 3.4].
The hairy skin above the supra-orbital margin is the eyebrow. Over its medial end is a curved ridge of bone—the superciliary arch. This is well formed only in males and is separated from its fellow on the other side by a smooth median area—the glabella.
The white of the eye is the sclera. The transparent part of the front of the eye is the cornea. The coloured iris (usually black or dark brown) is seen through the cornea and has a dark, circular central aperture—the pupil. The visible part of the sclera is covered with a moist, transparent membrane—the conjunctiva. The conjunctiva passes from the sclera on to the deep surface of the eyelids. The reflection of the conjunctiva on to the eyelids is the fornix of the conjunctiva, and the entire conjunctiva encloses the conjunctival sac. The sac opens anteriorly between the eyelids through the palpebral fissure [Fig. 4.3].
The eyelids or palpebrae are folds which protect the front of the eye. Each time we blink, the eyelids moisten the exposed surface of the eyeball by spreading lacrimal fluid over it. The upper lid is larger and more mobile than the lower one, and the upper conjunctival fornix is much deeper. When the eyes are closed, the palpebral fissure is nearly horizontal and lies opposite the lower margin of the cornea. When the eyes are open, the margins of the eyelids overlap the cornea slightly, the upper eyelid more than the lower.
At the medial angle of the eye is a small, triangular area known as the lacus lacrimalis, with a reddish elevation—the lacrimal caruncle—near its centre. The lacus carries a few fine hairs which filter the lacrimal fluid passing to the lacrimal canaliculi. Just lateral to the lacus is a small, vertical fold of conjunctiva—the plica semilunaris [Fig. 4.3].
The lower eyelid is easily everted by pulling down the skin below it, and the lower fornix is exposed by turning the eyeball upwards. The upper lid is difficult to evert because of the rigid tarsal plate buried in it. Once everted, the upper eyelid tends to remain so. Even with the upper eyelid everted, the deep superior fornix is not exposed.
Eyelashes (cilia) project from the anterior edge of the free margin of the eyelid. On the deep surface of the eyelids are a number of yellowish, parallel streaks produced by the tarsal glands [Fig. 4.3]. The ducts of these glands open near the posterior edge of the free margin of the eyelids. The free margin of the lids is rounded medially and has a small elevation—the lacrimal papilla. Each papilla is surmounted by a tiny aperture—the lacrimal punctum. The puncta lead into the lacrimal canaliculus which drains the lacrimal fluid from the conjunctival sac. Note that the puncta face posteriorly into the conjunctival sac, and that the eyelids move medially when the eye is forcibly closed. This action moves the lacrimal fluid towards the puncta at the medial angle of the eye.
Press a fingertip on the skin between the nose and the medial angle of the eye and feel the rounded, horizontal cord—the medial palpebral ligament. This ligament connects the upper and lower eyelids (and their muscle the orbicularis oculi) to the medial margin of the orbit. If the eyelids are gently pulled laterally, the medial palpebral ligament is more easily felt and may be seen as a small skin ridge.
The auricle is that part of the ear which is seen on either side of the head [Fig. 4.1]. It consists of a thin plate of elastic cartilage covered with skin. (The lobule is devoid of cartilage.)
The cartilage of the auricle is continuous with the cartilage of the external acoustic meatus. The tubular meatal cartilage is incomplete above and in front, and its wall is completed by dense fibrous tissue which is continuous with tissue between the tragus and the beginning of the helix.
The muscles of the auricle are supplied by the facial nerve. The skin of the lower part of the auricle is supplied by the great auricular nerve. The upper part of the lateral surface is supplied by the auriculotemporal nerve, and the upper part of the medial surface by the lesser occipital nerve.
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Reference
(2018). The scalp and face. Koshi D(Ed.), Cunningham's Manual of Practical Anatomy, Volume 3: Head, Neck and Brain, 16th Edition. Oxford University Press. https://accessmedicine.mhmedical.com/content.aspx?bookid=3477§ionid=286586059