66. Find in the text English equivalents for these words and word combinations:

Кровеносные сосуды и нервы, кости плода, имеет сходство с костной тканью, процесс отложения солей кальция, постепенное замещение, через слизистую тонкого кишечника, в кровоток, находятся, широкие на концах, прикрепление мышц, сесамовидные кости, губчатый слой кости, продукты распада, желтый костный мозг, жировая ткань, так же как.

67. Read the text once again. Put the questions in the order they are answered in the text, then answer the questions.

• What are bones composed of?

• Why is vitamin D necessary for us?

• Where are short bones found?

• When is cartilage tissue replaced by osseous tissue?

• What is ossification?

• What is the periosteum?

• What bones have broad ends?

• Where are sesamoid bones found?

• What does the formation of bone depend on?

• What are the bones of the fetus composed of?

• What bones are soft body parts covered by?

• What do haversian canals contain?

• Where can we find red bone marrow / yellow bone marrow?

• What’s the difference between red bone marrow and yellow bone marrow?

• What is osseous tissue?

• What types of bones are there?

• What’s the difference between cartilage and osseous tissue?

• What is the diaphysis? / epiphysis?

• What is the function of articular cartilage?

• What is compact bone?

68. Read the text. The Systems of the Body

The highest level of body organization is the organ system. The body includes nine major organ systems, each composed of various organs and tissues that work together as a functional unit. They are skeletal, muscular, cardiovascular, respiratory, digestive, urinary, reproductive, endocrine, and nervous systems.

The skeleton of the body is composed of 223 bones of various sizes and shapes, which give firm but flexible support to the soft tissues, muscles and organs. The bones of the skeleton are connected together by the joints or by the cartilages and ligaments.

The musculature is usually divided into three types: striated (or skeletal), cardiac, and smooth muscles. Skeletal muscles are responsible for movements of the body such as running and jumping. Smooth muscles are found within the organs and blood vessels. They are responsible for many body functions such as movement of the organs of the digestive tract, blood vessels, secretory ducts. Cardiac muscle is found only in the heart. Smooth and cardiac muscle are under the control of the involuntary, or autonomic, nervous system. Striated muscle, on the other hand, is mainly under the control of the voluntary, or central, nervous system.

The cardiovascular (or circulatory) system is the system of blood circulation. It is composed of the heart, blood, and blood vessels. The heart is the main organ of the cardiovascular system. It consists of two separate chambers divided by the septum. Each of the chambers has two connected parts: the atrium and the ventricle. There are three types of blood vessels: arteries, veins and capillaries. Arteries carry blood away from the heart to other organs and tissues of the body. Arteries divide into smaller and smaller vessels which finally divide into capillaries. Capillaries are microscopic vessels; their walls are only one epithelial cell in thickness. The exchange between the blood and body cells occurs through the walls of the capillaries: the cells are supplied with oxygen and nutrients, waste products are carried away. Then the blood is collected from the capillaries and carried back to the heart by veins.

The respiratory system obtains from the air the oxygen necessary for cellular metabolism; it also returns to the air the carbon dioxide, a waste product of such metabolism. The system consists of the breathing passages and two lungs. The breathing passages are the nasal cavity, the pharynx, the larynx, the trachea and two bronchi. They conduct air to the lungs. The lungs are located in the lateral cavities of the chest. The left lung is smaller than the right one; it is divided into two lobes. The right lung has three lobes. Each lung is covered with the pleura (or pleural membrane).

The digestive system breaks down food into nutrients, which are then absorbed from the blood or lymph; this system also eliminates the waste materials which cannot be absorbed. The system consists of the digestive tract and digestive glands. The digestive tract is 8 - 10 meters long. It is divided into the mouth, pharynx, esophagus, stomach, small intestine and large intestine. The digestive glands secrete juices which take part in the chemical process of digestion. The largest glands are the liver with gallbladder and pancreas.