Unit 17. Skeleton and muscles.

WARM-UP: Could you explain the following: Babies are born with 300 bones, but by adulthood we have only 206 in our bodies.

VOCABULARY: Learn the following words and word combinations.

Trunk limb skull chest abdomen forearm wrist finger toe thorax to anchor spinal cord jaw spinal column breast bone collarbone shoulder elbow periosteum compact bone pelvis spongy bone bone marrow birth canal smooth muscles

Guess the meaning of the following words.

Leg; arm; skeleton; muscles; to protect; brain; lung; rib; blood vessel; blood cell; blood; nerves; calcium; phosphorus; cardiac muscles; skeletal muscles; digestive tract; involuntary; fiber; heart; internal organs.

Practice the following for pronunciation.

forearm [ˈfɔː.rɑːm]

wrist [rɪst]

thorax [ˈθɔː.ræks]

spinal cord [ˈspaɪ.nl kɔːd]

spinal column [ˈspaɪ.nl ˈkɒl.əm]

breast [brest]

collarbone [ˈkɒl.ə.bəʊn]

shoulder [ˈʃəʊl.də]

elbow [ˈel.bəʊ]

periosteum [per′i·os′tē·əm]

pelvis [ˈpel.vɪs]

spongy bone [ˈspʌn.dʒi bəʊn]

READING: Read the text and do the tasks that follow.

The human body is separable into the head, the trunk and the limbs. In the head the skull is distinguishable from the face. The trunk includes the chest (thorax) and the abdomen. Of the limbs there are two pairs - the upper (arms), consisting of the upper arm, the forearm, the wrist and the fingers, and the lower limbs (legs), including the thigh, the leg and the toes.

The human skeleton is made up of more than 200 bones. It gives our muscles a firm place to anchor themselves and also protects our body’s more fragile organs. For example, the brain is protected by the skull and the lungs are protected by the ribs.

The bones form the skeleton of the body. They vary in shape and size to fit their function. The spine has 33 separate bones. It is shaped to protect the spinal cord, which travels through it, while also giving the spinal muscles a place for attachment. The most important part of the skeleton is the backbone. The bones which form the skeleton or bony framework of the body include the bones of the head, the bones of the trunk, the bones of the lower and upper limbs. The bones of the head include the bones which make up the skull and freely movable bone which forms our lower jaw. The bones of the trunk include the spinal column, the ribs and the breastbone. The arms join the body at the shoulder, which consists of two bones - the collar-bone in front, and the shoulder-blade behind. Between the shoulder and the elbow there is only one bone in the arm (humerus), but between the elbow and the wrist there are two (ulna, radius). In the wrist there are eight small bones. Next come the bones of the hand itself. We have twenty-seven bones in the framework of the hand and wrist alone.

All bones have an outer layer called the periosteum. This contains nerves and blood vessels. Underneath lies the toughest part – compact bone. This part is hollow and is lined with spongy bone, which makes it strong but not too heavy. Cells in the bone take calcium and phosphorus from the blood to keep the bony substance hard. Bone marrow lies at the center of bone. The bone marrow at the end of long bones is responsible for making new blood cells.

The male skeleton is different to the female skeleton. For example, the female pelvis is specially designed to allow a baby’s safe journey down the birth canal.

We know that the muscles constitute approximately fifty per cent of the total body weight. There are three main types of muscular tissue that we identify and classify on the basis of structure and function: smooth muscle, skeletal muscle, cardiac muscle.

Smooth muscles can contract slowly. They make up the walls of the internal organs such as those of the blood vessels and the digestive tract. The walls of the blood vessels are contracting and expanding when they respond to certain chemicals in the blood or in response to the effect of temperature, but we can’t cause them to lift our arm or to open our mouth (involuntary muscles). Striated muscles are most necessary for manipulation of the bones of the skeleton. Those are the muscles necessary for walking, running, turning the head and so on. That’s why they are sometimes called the skeletal muscles. This type includes all those muscles which must react quickly to changes in the environment, i.e. those that become active through an effort of will (voluntary muscles). A characteristic feature of cardiac muscle is that fibers have neither a beginning nor an end. In other words, the heart is simply a huge net of muscles in which all elements are continuous with each other.