Good day everyone, Today we are going to discuss about the mouth:
learning outcomes
After studying this section, you should be able to:
- List the principal structures associated with the mouth
- describe the structure of the mouth
- describe the structure and the functions of the tongue
- describe the structure and functions of the teeth
- outline the arrangement of normal primary and secondary dentition
The mouth or oral cavity is bounded by muscles and bones :
Anteriorly -by lips
posteriorly -it is continuous with the oropharynx
Laterally -by the muscles of the cheeks
superiorly -by the bony hard palate and muscular soft palate
Inferiorly -by the muscular tongue and the soft tissues of the floor of the mouth.
The oral cavity is lined throughout with mucous membrane, consisting of stratified squamous epithelium containing small mucus-secreting glands.
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The part of the mouth between the gums and the cheeks is the vestibule and the remainder of its interior is the oral cavity. The mucous membrane lining of the cheeks and the lips is reflected onto the gums or alveolar ridges and is continuous with the skin of the face.
The palate forms the roof of the mouth and it’s divided into the anterior hard palate and the posterior soft palate and the posterior soft palate. The hard palate is formed by the maxilla and the palatine bones. The soft palate, which is muscular, curves downwards from the posterior end of the hard palate and blends with the walls of the pharynx at the sides.
The uvula is a curved fold of muscle covered with mucous membrane, hanging down from the middle of the free border of the soft palate. Originating from the upper end of the uvula are four folds of mucous membrane, two passing downwards at each side to form membranous arches. The posterior folds, one on each side, are the palatopharyngeal arches and the two anterior folds are the palatoglossal arches. On each sides, between the arches, is a collection of lymphoid tissue called the palatine tonsil.
Read more on: 1. Exercise
Tongue (a part of the mouth)
The tongue is composed of voluntary muscle. It is attached by its base to the hyoid bone and by a fold of its mucous membrane covering, called the frenulum, to the floor of the mouth . The superior surface consists of stratified squamous epithelium, with numerous papillae (little projections). Many of these contain sensory receptors (specialized nerve endings) for the sense of taste in the taste buds.
Blood supply
The main arterial blood supply to the tongue is by the lingual branch of the external carotid artery. Venous drainage is by the lingual vein, which joins the internal jugular vein.
Nerve supply
The nerve involved are:
- the hypoglossal nerve, which supply the voluntary muscle
- the lingual branch of the mandibular nerves, which arise from the 5th cranial nerves, are the nerves of somatic (ordinary) sensation,i.e. pain, temperature and touch
- the facial and glossopharyngeal nerves, the nerves of the taste.
Functions of the tongue
The tongue plays an important part in:
- chewing (mastication)
- swallowing(deglutition)
- speech
- taste
Nerve endings of the sense of taste are presented in the papillae and widely distributed in the epithelium of the tongue.
Teeth
The teeth are embedded in the alveoli or sockets of the alveolar ridges of the mandible and the maxilla. Babies are born with two sets, or dentitions, the temporary or deciduous teeth and the permanent teeth. At birth teeth of both dentitions are present, in immature form, in the mandible and maxilla.
There are 20 temporary teeth, 10 in each jaw. They begin to erupt at about 6 months of age, and should all be present by 24 months.
The permanent teeth begin to replace the deciduous teeth in the 6th year of age and this dentition, consisting of 32 teeth, is usually complete by the 21st year.
Functions of the teeth
Teeth have different shapes depending on their functions. Incisors and canine teeth are the cutting teeth and are used for biting off pieces of food, whereas the premolar and molar teeth, with broad, flat surfaces, are used for grinding or chewing food.
Structure of a tooth
Although the shapes of the different teeth vary, the structure is the same and consists of:
- The crown – the part that protrudes from the gum
- the root – the part embedded in the bone
- the neck – the slightly narrowed region where the crown merges with the root.
Blood supply
Most of the arterial blood supply to the teeth is by branches of maxillary arteries. The venous drainage is by a number of veins which empty into the internal jugular veins.
Nerve supply
The nerve supply to the upper teeth is by branches of the maxillary nerves and to the lower teeth by branches of the mandibular nerves. These are both branches of the trigeminal nerves (5th cranial nerves).
