Aging functions
I – Introduction:
Aging is a decrease in the functional capacities of the organism. This
alteration is evident in situations that involve functional reserves
(stress, effort, acute illnesses). The decrease in functional reserves induces a
reduction in the adaptability of the organism. Similarly, the systems regulating physiological parameters prove less effective.
II – Salivation function
Elderly subjects frequently complain of dry mouth. This is accompanied by
difficulties in chewing, swallowing and speaking.
II.1 – Physiology of salivary senescence:
Salivary sclerosis: Salivary sclerosis manifests itself mainly in the submandibular glands, producing a picture of dystrophic sclerosing submandibulitis. This pathology is found in most cases in postmenopausal women.
Adipose: Adipose mainly affects the parotid glands (sialadenosis and nutritional parotidomegaly responsible for parotid swelling). This alteration is favored by nutritional and dietary disorders.
Dedifferentiation of acini: This alteration is constantly present during senescence but is not specific to it.
Oncocytic metaplasia: Here, the glandular cells are characterized by their large size, the presence of a small dense nucleus and by a very eosinophilic cytoplasm rich in mitochondria. Their presence alone indicates a process of senescence.
Canalicular microcrystallizations: These aggregates can be the cause of salivary calcinosis. They are not specific to senescence but are observed more frequently in the elderly and women.
II.2 – Impact on salivation:
On salivary composition: Its composition changes constantly, depending on the
chronobiology of the glands as well as the salivary flow.
On salivary flow: It varies from one individual to another and depends on many factors, psychological or medicinal among others. This individual variation in salivary flow could explain the differences in taste perception between individuals.
On pH and salivary buffer capacity: An alteration of salivary flow therefore results in a decrease in pH. This lowering is common in the elderly, even in good health.
III – Taste perception
Senescence results in a significant decrease in the number of taste receptors, which go from approximately 10,000 to less than 1,000, whether at the lingual or extralingual level. This deficit can cause different types of disorders.
The oral cavity is constantly lined with saliva generated by the major and minor salivary glands. Saliva-flavor interactions are very varied, with each molecule able to act and interact specifically with saliva. Saliva contributes to taste by three types of actions:
- as a food solvent;
- as a transporter of flavor molecules;
- through its composition.
A reduction in salivary flow therefore results in
an alteration of taste perception.
IV – Manducation (articular function):
The bony surfaces present (condylar process of the mandible, mandibular fossa and
articular tubercle of the temporal bone) are most often subject to diffuse demineralization and thinning of the bony cortices. The articular disc is generally marked by thinning without perforation. Edentulism, particularly molar, increases the mechanical constraints exerted on this joint.
V – Mastication:
the masticatory musculature: Newton et al. showed a decrease in the surface area and density of the masseter and medial pterygoid muscles with age.
Receptors: The oral cavity contains gingival, periodontal, lingual, palatal and jugal mechanoreceptors. The main role of these receptors is to signal the position of the food bolus and the texture of food during chewing. Periodontal receptors also participate in the control of bite force through sensory feedback. Tooth loss and mucosal alterations result in a disruption of this sensory feedback.
Nervous control:
Chewing is a semi-automatic activity. A rhythm -generating center , located in the brainstem, appears to modulate masticatory rhythms. It would be activated either by information from higher centers such as the cortex, or by peripheral information collected by receptors in the oral cavity. Sensory feedback, carried out by intraoral mechanoreceptors, plays a very important role in the coordination of the tongue, lips, and jaws.
Aging functions
VI – Neurosensory aging:
Visual aging
It is essentially marked by the opacification of the lens, by the reduction in pupil diameter which promotes the narrowing of the visual field, age-related macular degeneration and the accumulation of hyaline material in the retina.
Cochleovestibular aging
The hair cells of the inner ear contract less well, and age-related presbycusis is observed. Older subjects use their vestibular system less, which can cause balance disorders.
phonation:
Phonation is often altered by tooth loss, wearing prostheses, etc., as well as by aging of the tongue muscles.
Neurological pathologies complicate the picture by the repercussions on phonation that they cause.
Aging functions
VII – CONCLUSION
The impact of aging on the oral-facial tissues has a direct effect on the various functions. The disruption of a function such as salivation has a driving effect on the rest of the functions.