IV. Supplement

1. Match the following English word combinations with the Ukrainian ones:

1) bone marrow a) кровообіг

2) nutrients b) процес згортання крові

3) life span c) кістковий мозок

4) cancer cells d) поживні речовини

5) blood stream e) ракові клітини

6) clotting process f) тривалість життя

2. Read and translate the following text. Be ready to discuss the informa­tion obtained.

3. Find 7—10 sentences characterizing the structure of the blood. Trans­late them in written form.

TYPES OF BLOOD CELLS

Humans can't live without blood. Without blood, the body's organs couldn't get the oxygen and nutrients they need to survive, we couldn't keep warm or cool off, fight infections, or get rid of our own waste products. Without enough blood, we'd weaken and die.

The average adult has between 5 to 6 liters of blood or blood volume. The blood carries oxygen and essential nutrients to all of the living cells in the body, and also carries waste products to systems that eliminate them. Most of the blood is made up of plasma. A little less than half of this blood volume is composed of red and white blood cells, and other solid elements called platelets. So, the blood contains three types of blood cells:

l) red blood cells (RBCs);

2) white blood cells (WBCs);

3) platelets.

In babies and young children, blood cells are made within the bone marrow (the soft tissue inside our bones) of lots of bones throughout the body. But, as kids get older, blood cells are made mostly in the bone marrow of the vertebrae (the bones of the spine), ribs, pelvis, skull, sternum (the breastbone), and parts of the humerus (the upper arm bone) and femur (the thigh bone).

The cells travel through the circulatory system suspended in a yellowish fluid called plasma. Plasma is 90 % water and contains nutrients, proteins, hormones, and waste products. Whole blood is a mixture of blood cells and plasma.

Red blood cells (also called erythrocytes) are shaped like slightly indented, flattened disks. RBCs contain the iron-rich protein hemoglobin. Blood gets its bright red color when hemoglobin picks up oxygen in the lungs. As the blood trav­els through the body, the hemoglobin releases oxygen to the tissues. The body contains more RBCs than any other type of cells, and each has a life span of about 4 months. Each day, the body produces new red blood cells to replace those that die or are lost from the body.

White blood cells (also called leukocytes) are a key part of the body's system for defending itself against infection. They can move in and out of the bloodstream to reach affected tissues. The blood contains far fewer WBCs than red cells, al­though the body can increase production of WBCs to fight infection. There are several types of WBCs, and their life spans vary from a few days to months. New cells are constantly being formed in the bone marrow.

Several different parts of blood are involved in fighting infection. White blood cells called granulocytes and lymphocytes travel along the walls of blood vessels. They fight germs¹ such as bacteria and viruses and may also attempt to destroy cells that have become infected or have changed into cancer cells.

Certain types of WBCs produce antibodies, special proteins that recognize foreign materials and help the body destroy or neutralize them. The white cell count (the number of cells in a given amount of blood) in someone with an infection often is higher than usual because more WBCs are being produced or are entering the bloodstream to battle the infection. After the body has been challenged by some infections, lymphocytes "remember" how to make the specific antibodies that will quickly attack the same germ if it enters the body again.

Platelets (also called thrombocytes) are tiny oval-shaped cells made in the bone marrow. They help in the clotting process. When a blood vessel breaks, plate­lets gather in the area and help to seal off the leak. Platelets survive only about 9 days in the bloodstream and are constantly being replaced by new cells.

Important proteins called clotting factors are critical to the clotting process. Although platelets alone can plug small blood vessel leaks and temporarily stop or slow bleeding, the action of clotting factors is needed to produce a strong, stable clot. Platelets and clotting factors work together to form solid lumps to seal² leaks, wounds, cuts, and scratches and to prevent bleeding³ inside and on the surfaces of our bodies.

When large blood vessels are severed (or cut) the body may not be able to repair itself through clotting alone. In these cases, dressings⁴ or stitches are used to help control bleeding.

Blood contains other important substances, such as nutrients from food that has been processed by the digestive system. Blood also carries hormones released by the endocrine glands and carries them to the body parts that need them. Blood also carries carbon dioxide and other waste materials to the lungs, kidneys, and digestive system to be removed from the body.

Notes:

¹germ — мікроб, бактерія

²to seal — щільно закривати, блокувати

³bleeding — кровотеча

⁴dressing — перев'язування (рани)

Date: 2015-09-18; view: 644; Нарушение авторских прав