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

Date: 2016-06-12; view: 12