Make the sentences of your own using the new words (10 sentences). Find the verb to be in the text. Explain why it is used in such a way?

The oral cavity forms in the embryo from an in-pocketing of the skin, stomodeum; it is, thus, lined by ectoderm. Functionally, the mouth forms the first portion of both the digestive and respiratory systems. Various special structures are found in, or associated with, the mouth.

In humans the margins of the lips mark the junction between the outer skin and the inner mucous lining of the oral cavity. The roof of the mouth consists of the hard palate and, behind this, the soft palate which merges into the oropharynx. The lateral walls consist of the distensible cheeks. The floor of the mouth is formed principally by the tongue and the soft tissues that lie between the two sides of the lower jaw, or mandible.

The tongue, a muscular organ in the mouth, provides the sense of taste and assists in chewing, swallowing, and speaking. It is firmly anchored by connective tissues to the front and side walls of the pharynx, or throat, and to the hyoid bone in the neck.

The posterior limit of the oral cavity is marked by the fauces, an ap-perture which leads to the pharynx. On either side of the fauces are two muscular arches covered by mucosa, the glossopalatine and pharyngo-palatine arches; between them lie masses of lymphoid tissue, the tonsils. Hiese are spongy lymphoid tissues composed mainly of lympho-cytic cells held together by fibrous connective tissue. Suspended from the posterior portion of the soft palate is the soft retractable uvula. The palate develops from lateral folds of the primitive upper jaw. The palate of mammals consists of two portions. The hard palate, more anterior in position, underlies the nasal cavity. The soft palate hangs like a curtain between the mouth and nasal pharynx.

The hard palate has an intermediate layer of bone, supplied anteriorly by paired palatine processes of the maxillary bones, and posteriorly by the horizontal part of each palate bone. The oral surface of the hard palate is a mucous membrane covered with a stratified squamous epithelium. Anteriorly in humans there are four to six transverse palatine ridges: these diminish in prominence between fetal life and old age. A submucosal layer contains mucous glands and binds the membrane firmly to the periosteum of the bony component. Above the bone is the mucous membrane that forms the floor of the nasal cavity.

The soft palate is a backward continuation from the hard palate. Its free margin connects on each side with two folds of mucous membrane, the palatine arches, enclosing a palatine tonsil. In the midline the margin extends into a fingerlike projection called uvula. Both the hard and soft palate bear a seam, or raphe, along the midline. The oral side of the soft palate continues as the covering of the hard palate, and the submucosa contains mucous glands. The intermediate layer is a sheet of voluntary muscle.