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Bones and muscles

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  1. THE SKELETON AND MUSCLES

 

Muscles and bones work together. The bones make up the skeletal system, which provides structural support, sites for muscle attachment, and organ protection. Osseous tissue, or bone, as it is more often called, consists of cells and collagen fibers interspersed in a matrix of intercellular material containing calcium phosphate and calcium carbonate, which are responsible for hardness. Together, these substances account for two-thirds of the weight of bones, while the collagen fibers, which reinforce the tissue, account for the other third.

In addition to bone, another important connective tissue in most skeletal systems is cartilage, which unlike bone, is both firm and flexible. Bone is usually considerably harder and more brittle. Most sharks and rays have skeletal systems composed of all cartilage and no bone. Some other “primitive” groups of fish have less bone than cartilage in their skeletal systems. In most other vertebrates, however, cartilage is located only where firmness and flexibility are needed, such as in joints, nose, ears, larynx, and trachea. During the development of the skeletal system of these vertebrates, the embryos begin with cartilaginous skeletons. Gradually most of the cartilage is replaced by true bone.

Depending on the construction of the particular bony tissue, it can range in consistency from being completely spongy to being very compact. The spongy bone contains many spaces filled with marrow which is either composed of fat or involved in the production of blood cells. In the case of relatively lighter animals such as birds, the spaces may be filled with air sacs. Compact bony tissue is thicker and usually involved in support. Such bones can resist considerable weight and stress.

Compact bones are penetrated by blood vessels and nerves through small narrow openings, some of which are known as Haversian canals, whose microscopic structure is identified by the characteristic concentric rings of bony tissue surrounding them. These rings are composed of cells that were involved in producing the bony tissue. Spongy bone doesn’t contain Haversian systems, nor does cartilage. Materials are exchanged through the blood vessels and bone cells that penetrate the Haversian canals. This is the only way for materials to move to and from the cells living throughout bony tissue.

The movement of different parts of the body all depend on muscular contraction, on the location of the origins and insertions, and on the type of joint involved. Muscles usually work antagonistically. That is, when one group of muscles contracts, it will pull part of the body one way. Alternately, when the antagonistic group of muscles contracts, it will pull the same body part in the other direction.

 

 

II. POST-READING TASKS.

1. Discuss the following questions:

I. What substances are found in skeletal systems? What are their functions?

II. How do muscles work antagonistically?

2. Write an essay describing the structure of the skeletal system.

 

 

UNIT 7

 

1. PRE-READING AND READING TASKS.

1. Study the vocabulary to avoid difficulties of understanding:

 

affect (v) [q'fekt] воздействовать
clot (v) [klPt] свертываться
invade (v) [In'veId] вторгаться
survive (v) [sq'vaIv] выживать, продолжать существовать
withstand (v) [wID'stxnd] противостоять
clot [klPt] сгусток
germ [dZE:m] микроб, бактерия
liquid ['lIkwId] жидкость
mammal ['mxm(q)l] млекопитающее
means [mi:nz] средство
particle ['pQ:tIk(q)l] частица
platelet ['pleItlIt] тромбоцит
removal [rI'mu:v(q)l] удаление
rupture ['rAptSq] разрыв
scab [skxb] корка
web [web] сеть
pulsatile ['pAlsqtaIl] пульсирующий
sufficient [sq'fIS(q)nt] достаточный

 

2. Try to guess the meaning of the following words and word combinations:

 

pumping action aquatic environment
pathogenic organism self-preservation system
alkalinity to propel
non-aqueous surroundings circulatory system
acidity watery medium
bleeding right ventricle
fibrin carbon dioxide
capillary left atrium

 

3. Read the text carefully to fulfil the tasks that follow.

 

 


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Читайте в этой же книге: ADDITIONAL TEXT | I. PRE-READING AND READING TASKS. | THE CELL | ADDITIONAL TEXT | HOW THE BODY WORKS | ADDITIONAL TEXTS | THE BRAIN | ADDITIONAL TEXT | THE NERVES | THE NERVOUS SYSTEM |
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