PARAORAL TISSUES

LIPS - are a visible organ, at the mouth of humans and many animals. Lips are soft, protruding, movable, and serve as the opening for food intake, as an erogenous organ used in kissing and other acts of intimacy, as a tactile sensory organ, and in the articulation of speech.

ANATOMICAL BASIS OF THE HUMAN LIP

One differentiates between the Upper (Labia superfluos entafada) and lower lip (Labium inferius). The lower lip is usually somewhat larger. The border between the lips and the surrounding skin is referred to as the vermilion border, or simply the vermilion. The vertical groove on the upper lip, is known as the philtrum. The entire skin between the upper lip and the nose is referred to as the "ergotrid".

The skin of the lip, with three to five cellular layers, is very thin compared to typical face skin, which has up to 16 layers. With light skin color, the lip skin contains less melanocytes (cells which produce melanin pigment , which give skin its color). Because of this, the blood vessels appear through the skin of the lips, which leads to their notable red coloring. With darker skin color this effect is less prominent, as in this case the skin of the lips contains more melanin and thus is visually thicker.

The lip skin is not hairy, and does not have sweat glands or sebaceous glands. Therefore it does not have the usual protection layer of sweat and body oils which keep the skin smooth, inhibit pathogens, and regulate warmth. For these reasons, the lips dry out faster and become chapped more easily.

ANATOMY IN DETAIL

The skin of the lips is stratified squamous epithelium. The mucous membrane is represented by a large area in the sensory cortex, and is therefore highly sensitive. The Frenulum Labii Inferioris is the frenulum of the lower lip. The Frenulum Labii Superioris is the frenulum of the upper lip.

Sensory nerve supply

Trigeminal nerve o The infraorbital nerve is a branch of

the maxillary branch. It supplies not only the upper lip, but much of the skin of the face between the upper lip and the lower eyelid, except for the bridge of the nose.

o The mental nerve is a branch of the mandibular branch ( via the inferior alveolar nerve). It supplies the skin and mucous membrane of the lower lip and labial gingiva (gum) anteriorly.

Blood supply

The facial artery is one of the six non-terminal branches of the external carotid artery. It supplies the lips by its

superior and inferior labial branches, each of which bifurcate and anastomose with their companion artery from the other side.

Muscles acting on the lips

The muscles acting on the lips are considered part of the muscles of facial expression. All muscles of facial expression are derived from the mesoderm of the second pharyngeal arch, and are therefore supplied (motor supply) by the nerve of the second pharyngeal arch, the facial nerve (7th cranial nerve). The muscles of facial expression are all specialised members, of the panniculus carnosus, which attach to the dermis and so wrinkle, or dimple the overlying skin. Functionally, the muscles of facial expression are arranged in groups around the orbits, nose and mouth.

The muscles acting on the lips:

sphincters of the oral orifice o buccinator o orbicularis oris

anchor point for several muscles o modiolus

lip elevation o levator labii superioris o levator labii superioris alaeque nasi o levator anguli oris o zygomaticus minor o zygomaticus major

lip depression o risorius o depressor anguli oris o depressor labii inferioris o mentalis

FUNCTIONS OF THE LIP

Food intake

Because they have their own muscles and bordering muscles, the lips are very movable. Lips are used for eating functions, like holding food or to get it in the mouth. In addition, lips serve to close the mouth airtight shut, and to, hold food and drink inside, and to keep out unwanted objects. Through making a narrow funnel with the lips, the suction of the mouth is increased. This suction is essential for babies to breast feed. Lips can also be used to suck in other contexts, such as tactile stimulation of other people.

Erogenous zone

Because of their high amounts of nerve endings, the lips are an erogenous zone. The lips therefore play a crucial role in kissing and other acts of intimacy. As the mouth, lips, and tongue are among a woman's most erogenous zones, stimulating a woman's mouth and lips during acts of intimacy has been shown to elicit pleasure and to have a direct stimulatory effect on arousing her genital organs. [1]

A woman's lips are also a visible expression of her fertility. In studies performed on the science of human attraction, psychologists have concluded that a woman's facial and sexual attractiveness is closely linked to the makeup of her hormones during puberty and development. Contrary to the effects of testosterone on a man's facial structure, the effects of a woman's estrogen levels serve to maintain a relatively "childlike" and youthful facial structure during puberty and during final maturation. It has been shown that the more estrogen a woman has, the larger her eyes and the fuller her lips. Surveys performed by sexual psychologists have also found that universally, men find a woman's full lips to be more sexually attractive than lips that are less so.[2] A woman's lips are therefore sexually attractive to males because they serve as a biological indicator of a woman's health and fertility. As such, a woman's lipstick (or collagen lip enhancement) takes advantage by "tricking" men into thinking that a women has more estrogen than she actually has, and thus that she is more fertile and attractive.[3]

Tactile organ

The lip has many nerve endings and reacts as part of the tactile (touch) senses. Lips are very sensitive to touch, warmth, and, cold. It is therefore an important aide for exploring unknown objects for babies and toddlers.

Articulation

The lips serve for creating different sounds - mainly the labial, bilabial, and labiodental consonant sounds - and thus create an important part of the speech apparatus. The lips enable whistling and the performing of wind instruments such as the trumpet, clarinet, and flute.

Facial expressions

TONGUE - is the large bundle of skeletal muscles on the floor of the mouth that manipulates food for chewing and swallowing (deglutition). It is the primary organ of taste. Much of the surface of the tongue is covered in taste buds. The tongue, with its wide variety of possible movements, assists in forming the sounds of speech. It is sensitive and kept moist by saliva, and is richly supplied with nerves and blood vessels to help it move.

Structure

The tongue is made mainly of skeletal muscle. The tongue extends much further than is commonly perceived, past the posterior border of the mouth and into the oropharynx.

The dorsum (upper surface) of the tongue can be divided into two parts:

an oral part (anterior two-thirds of the tongue) that lies mostly in the mouth

a pharyngeal part (posterior third of the tongue), which faces backward to the oropharynx

The two parts are separated by a V-shaped groove, which marks the sulcus terminalis (or terminal sulcus).

Since the tongue contains no bony supports for the muscles, the tongue is an example of a muscular hydrostat, similar in concept to an octopus arm. Instead of bony attachments, the extrinsic muscles of the tongue anchor the tongue firmly to surrounding bones and prevent the mythical possibility of 'swallowing' the tongue.

Muscles of the Tongue

Extrinsic muscles

Extrinsic muscles of the tongue by definition originate from structures outside the tongue and insert into the tongue. The four paired extrinsic muscles protrude, retract, depress, and elevate the tongue:

Muscle From Nerve Function

Genioglossus muscle mandible hypoglossal

nerve

protrudes the tongue as well as depressing its center.

Hyoglossus muscle hyoid bone hypoglossal

nervedepresses the tongue.

Styloglossus muscle

styloid process

hypoglossal nerve

elevates and retracts the tongue.

Palatoglossus muscle

palatine aponeurosis

pharyngeal branch of vagus nerve

depresses the soft palate, moves the palatoglossal fold towards the midline, and elevates the back of the tongue.

Intrinsic muscles

Coronal section of tongue, showing intrinsic muscles

Four paired intrinsic muscles of the tongue originate and insert within the tongue, running along its length. These muscles alter the shape of the tongue by: lengthening and shortening it, curling and uncurling its apex and edges, and flattening and rounding its surface.[2]

The superior longitudinal muscle runs along the superior surface of the tongue under the mucous membrane, and elevates, assists in retraction of, or deviates the tip of the tongue. It originates near the epiglottis, the hyoid bone, from the median fibrous septum.

The inferior longitudinal muscle lines the sides of the tongue, and is joined to the styloglossus muscle.

The verticalis muscle is located in the middle of the tongue, and joins the superior and inferior longitudinal muscles.

The transversus muscle divides the tongue at the middle, and is attached to the mucous membranes that run along the sides.

The tongue is often cited as the "strongest muscle in the body," a claim that does not correspond to any conventional definition of strength.

Papillae and taste buds

The oral part of the tongue is covered with small bumpy projections called papillae. There are four types of papillae:

filiform (thread-shape) fungiform (mushroom-shape) circumvallate (ringed-circle) foliate (leaf-shape)

All papillae except the filiform have taste buds on their surface.

The circumvallate are the largest of the papillae. There are 8 to 14 circumvallate papillae arranged in a V-shape in front of the sulcus terminalis, creating a border between the oral and pharyngeal parts of the tongue.

There are no lingual papillae on the underside of the tongue. It is covered with a smooth mucous membrane, with a fold (the lingual frenulum) in the center. If the lingual frenulum is too taut or too far forward, it can impede motion of the tongue, a condition called Tongue-tie (Ankyloglossia).

The upper side of the posterior tongue (pharyngeal part) has no visible taste buds, but it is bumpy because of the lymphatic nodules lying underneath. These follicles are known as the lingual tonsil.

The human tongue can detect five basic taste components: sweet, sour, salty, bitter and savory[citation

needed]. The sense of taste is referred to as a gustatory sense. Contrary to the popular myth and generations of schoolbooks, there are no distinct regions for tasting different tastes. This myth arose because Edwin G.

Boring replotted data from one of Wundt's students (Hanig) without labeling the axes, leading some to misinterpret the graph as all or nothing response.[3] The common conception of taste has a significant contribution from olfaction.

Innervation of the tongue

Motor innervation of the tongue is complex and involves several cranial nerves. All the muscles of the tongue are innervated by the hypoglossal nerve (cranial nerve XII) with one exception: the palatoglossal muscle is innervated by the pharyngeal branch of vagus nerve (cranial nerve X).

Sensory innervation of the tongue is different for taste sensation and general sensation.

For the anterior two-thirds of the tongue, general sensations and taste sensations are carried via different nerves.

o Somatic sensations travel from the tongue via the lingual nerve, a major branch of the mandibular nerve (itself a branch of the trigeminal nerve). This nerve also carries general sensation from areas of the oral mucosa and gingiva of the lower teeth.

o Taste sensation is carried to the facial nerve via the chorda tympani. The chorda tympani also carries parasympathetic fibers from the facial nerve to the submandibular ganglion.

The posterior one-third of the tounge has a more simple innervation, as both taste and general sensations are carried by the glossopharyngeal nerve.

Vasculature of the tongue

The tongue receives its blood supply primarily from the lingual artery, a branch of the external carotid artery. The floor of the mouth also receives its blood supply from the lingual artery.

There is also secondary blood supply to the tongue from the tonsillar branch of the facial artery and the ascending pharyngeal artery.

CHEEKS - constitute the area of the face below the eyes and between the nose and the left or right ear.

It is fleshy in humans and other mammals, the skin being suspended by the chin and the jaws, and forming the lateral wall of the human mouth, visibly touching the cheekbone below the eye.

In vertebrates, markings on the cheek area (malar stripes/spots/...), particularly immediately beneath the eye, often serve as important distinguishing features between species or individuals.

SALIVARY GLANDS - are exocrine glands that produce saliva. In other organisms such as insects, salivary glands are often used to produce biologically important proteins like silk or glues, and fly salivary glands contain polytene chromosomes that have been useful in genetic research.

Cells

There are 3 main types of cells that are found in the major salivary glands:

1. Serous cells, which are pyramidal in shape and are joined to usually form a spherical mass of cells called acinus, with a small lumen in the centre. Serous demilunes are found in the submandibular gland.

2. Mucous cells are usually cuboid in shape and organised as tubules, consisting of cylindrical arrays of secretory cells surrounding a lumen. These cells produce glycoproteins that are used for the moistening and lubricating functions of saliva.

3. Myoepithelial cells surround each secretory portion and are able to contract to accelerate secretion of the saliva.

Ducts

In the duct system, the lumens formed by steph intercalated ducts, which in turn join to form striated ducts. These drain into ducts situated between the lobes of the gland (called interlobar ducts or excretory ducts).

The main duct of the salivary glands ultimately empties into the mouth. Salivary glands release saliva that dilutes the acid found in the stomach.

Parotid Glands

The parotid glands are a pair of glands located in the subcutaneous tissues of the face overlying the mandibular ramus and anterior and inferior to the external ear. The secretion produced by the parotid glands is serous in nature, and enters the oral cavity through the Stensen's duct after passing through the intercalated ducts which are prominent in the gland. Despite being the largest pair of glands, only approximately 25% of saliva is produced by the glands.

Submandibular Glands

The submandibular glands are a pair of glands located beneath the floor of the mouth, superior to the digastric muscles. The secretion produced is a mixture of both serous and mucous and enters the oral cavity via Wharton's ducts. Approximately 70% of saliva in the oral cavity is produced by the submandibular glands, even though they are much smaller than the parotid glands.

Sublingual Gland

The sublingual glands are a pair of glands located beneath the floor of the mouth anterior to the submandibular glands. The secretion produced is mainly mucous in nature, however it is categorized as a mixed gland. Unlike the other two major glands, the ductal system of the subligual glands do not have striated ducts, and exit from 8-20 excretory ducts. Approximately 5% of saliva entering the oral cavity come from these glands.

Minor Salivary Glands

There are over 600 minor salivary glands located throughout the oral cavity within the lamina propria of the oral mucosa. They are 1-2mm in diameter and unlike the other glands, they are not encapsulated by connective tissue only surrounded by it. The gland is usually a number of acini connected in a tiny lobule. A minor salivary gland may have a common excretory duct with another gland, or may have its own excretory duct. Their secretion is mainly mucous in nature (except for Von Ebner's glands) and have many functions such as coating the oral cavity with saliva. Problems with dentures are usually associated with minor salivary glands.

Von Ebner's Glands

Von Ebner's glands are glands found in circumvallate papillae of the tongue. They secrete a serous fluid that begin lipid hydrolysis. They are an essential component of taste.

Innervation

Salivary glands are innervated, either directly or indirectly, by the parasympathetic and sympathetic arms of the autonomic nervous system.

Parasympathetic innervation to the salivary glands is carried via cranial nerves. The parotid gland receives its parasympathetic input from the glossopharyngeal nerve (CN IX) via the otic ganglion, while the submandibular and sublingual glands receive their parasympathetic input from the facial nerve (CN VII) via the submandibular ganglion.

Direct sympathetic innervation of the salivary glands takes place via preganglionic nerves in the thoracic segments T1-T3 which synapse in the superior cervical ganglion with postganglionic neurons that release norepinephrine, which is then received by β-adrenergic receptors on the acinar and ductal cells of the salivary glands, leading to an increase in cyclic adenosine monophosphate (cAMP) levels and the corresponding increase of saliva secretion. Note that in this regard both parasympathetic and sympathetic stimuli result in an increase in salivary gland secretions. The sympathetic

nervous system also affects salivary gland secretions indirectly by innervating the blood vessels that supply the glands.

PARANASAL SINUSES - are air-filled spaces, communicating with the nasal cavity, within the bones of the skull and face.

Types in humans

Humans possess a number of paranasal sinuses, divided into subgroups that are named according to the bones within which the sinuses lie:

the maxillary sinuses, also called the maxillary antra and the largest of the paranasal sinuses, are under the eyes, in the maxillary bones (cheek bones).

the frontal sinuses, over the eyes, in the frontal bone, which forms the hard part of the forehead.

the ethmoid sinuses, which are formed from several discrete air cells within the ethmoid bone between the nose and the eyes.

the sphenoid sinuses, in the sphenoid bone at the center of the skull base under the pituitary gland.

Development

Paranasal sinuses form developmentally through excavation of bone by air-filled sacs (pneumatic diverticula) from the nasal cavity. This process begins prenatally, and it continues through the course of an organism's lifetime.

Sinuses in animals

Paranasal sinuses occur in a variety of animals (including most mammals, birds, non-avian dinosaurs, and crocodilians). In non-humans, the bones occupied by sinuses are quite variable.

Biological function

The biological role of the sinuses is debated, but a number of possible functions have been proposed:

Decreasing the relative weight of the front of the skull, and especially the bones of the face. The shape of the facial bones is important, as a point of origin and insertion for the muscles of facial expression.

Increasing resonance of the voice. Providing a buffer against blows to the face. Insulating sensitive structures like dental

roots and eyes from rapid temperature fluctuations in the nasal cavity.

Humidifying and heating of inhaled air because of slow air turnover in this region