Read the text. Be ready to answer the questions.

The bones of the skull.

The skeleton is the bones of the body when fastened in their usual relative position to each other. The skeleton is composed of bones. The bones of the skull consist of cranial and facial parts. The bones, together with cartilages, joints and muscles make up the musculoskeletal system. The system is held together by bands of fibrous tissue called ligaments and tendons.

There are approximately 206 bones, nearly 700 muscles, and about 250 joints in human body. Except for tooth enamel, bone is the hardest tissue in the body. The densest part of a bone is one the outside; the inner portion is more spongy. Most of the mineral substance of the body, notably calcium and phosphorus, is deposited in the bones and gives them their hardness. Bones are living tissue. Even the hardest is traversed by microscopically small channels (Haversian canals), through which blood, lymph fluid, and nerves enter the bone. Bones have an outer lining called the periosteum, which contains many blood vessels, nerves and lymphatic spaces. In the hollow interior part of the bones is found bone marrow which is the principal blood forming organ.

Bones are classified as long (e.g. femur bone), short (e.g. wrist bone), flat (e.g. skull bones) and irregular (e.g. spinal vertebrae). Most bones are laid down in softer connective tissue, cartilage, before they accumulate minerals and become harder.

The skull is the sturdy bones that make up the head (cranium) and the face. There are eight bones in the cranium (not counting the little bones of the ear) and fourteen to shape the face.

The bones of the skull are slightly movable at birth. However they soon become fused with one another and form a solid structure. The bones of the skull are connected together so firmly that it is difficult to separate them.

The bones of the skull form one large cavity and some smaller cavities. The large cavity is called the cranial cavity. The brain is in the cranial cavity. One of the smaller cavities is the oral cavity and the other is the cavity of the nose. The other two cavities are the orbits.

The large bones of the skull are the frontal bone, the occipital bone at the back part of the head, the two temporal and parietal bones forming the temples of the head, the sphenoid bone at the top of the base of the skull and the ethmoid bone at the top of the root of the nose through which the olfactory nerves pass.

5. Answer the following questions:

1) What parts do the bones of the skull consist of?

2) How many bones (muscles, joints) are there in the skull?

3) What structures does the musculoskeletal system consist of?

4) What gives bones their hardness?

5) Are the bones a living tissue?

6) What is periosteum?

7) What does periosteum contain?

8) What is found in the hollow interior of the bones?

9) How are the bones classified?

10) Why is it difficult to separate the bones of the skull?

11) What is there in the cranial cavity?

12) What are the largest bones of the skull?

Grammar

Find the adjective in the text and explain how the degrees of comparison are formed.

State whether the predicate is used in Passive or Active Voice. Translate the sentences.

1) Cranial and facial bones form the skull. 2) Each rib is composed of a head, neck and body. 3) The main part of the head is called the skull. 4) The skull is composed of twenty six bones. 5) The bones of the skull consist of cranial and facial parts. 6) The bones of the skull are connected with the cervical vertebrae.

3. Find in the text the sentences in the Present Simple Passive and translate them.

Summary

Read the text and make the summary according to the plan:

1. The structures of the skull.

2. The structure and the role of the mandible.

3. The maxilla as a frame for the teeth and cavities.

Skull

A skull, or cranium, is a bony structure which serves as the general framework for a head. The skull protects the brain, acting as a form of natural helmet.

In humans, the skull is the uppermost portion of the human skeleton. It is made up of a number of bony parts - 8 in the skull proper (neurocranium) and 14 in the facial area (splanchnocranium). There are five main skull sections - one occipital, two frontal, two parietal. The sections are fused together in adults along sutures. At birth these sutures are fibrous and moveable, necessary for birth and later growth. The skull also contains the sinus cavities. The meninges are the membranes that separate the brain from the skull.

The mandible (inferior maxillary bone) is the largest and strongest bone of the face. It forms the lower jaw and holds the lower teeth in place. The mandible consists of a curved, horizontal portion, the body, and two perpendicular portions, the rami, which unite with the ends of the body nearly at right angles. The mandible, which is the bony structure bearing the dental arch, generates masticatory movement and brings the arch to a more effective point for mastication. The size and shape of the dental arch, consisting of teeth, are influenced by tooth size and shape of the mandible. However, the relationship between the morphologies of the teeth and the mandible, is not yet fully understood. As teeth develop in the alveolar bone, which is part of the mandible, their growth partly depends on that of the mandible. Thus, these structures influence each other at the developmental stage.

The maxillae are large bones of the face and form, by their union, the whole of the upper jaw. They hold the upper teeth, and connect on the left and right to the zygomatic bones (cheek bones). Each assists in forming the boundaries of three cavities, namely, the roof of the mouth, the floor and lateral wall of the nose and the floor of the orbit. The maxilla also forms a small part of the orbit of the eye, and extends upwards to the topmost part of the nose. Inside the mouth, the palatine bone lies behind the maxilla on the mouth's roof. Each bone consists of a body and four processes - zygomatic, frontal, alveolar, and palatine.

It is generally accepted that environmental factors have more influence on bony structures because of the attachment of musculature, and that consequently, bone shape is more changeable than tooth form. On the other hand, teeth do not change their shape after the completion of development, so that genetic factors are a better determinant of their shapes.

Translation