Chapter 4: The blood

Question 1

Blood

Answer 1

Is a fluid connective tissue. It circulates constantly around the body, allowing constant communication between tissues distant from each other. It transports:
-oxygen
-nutrients
-hormones
-heat
-protective substances
-clotting factors
Blood is composed of a clear, straw-colored, watery fluid called plasma in which several different types of blood cell are suspended.

Question 2

Plasma

Answer 2

Plasma is the liquid part of your blood. It is the clear, yellowish liquid portion of blood that remains after the cells and cellular components have been removed which includes the red blood cells, white blood cells and platelets
It carries these blood components throughout the body as the fluid in which they travel.

Question 3

Plasma proteins

Answer 3

Plasma proteins are proteins found in the blood plasma, the clear, protein-rich fluid which is left behind when platelets, red blood cells, and white blood cells are removed from the blood

Question 4

Albumins

Answer 4

These are the most abundant plasma proteins (about 60% of total) and their main function is to maintain normal plasma osmotic pressure.
Albumins also act as carrier molecules for free fatty acids, some drugs, and steroid hormones.

Question 5

Globulins

Answer 5

Globulins is a special group of proteins in the blood include antibodies, enzymes, carrier proteins, and other proteins.
Their main functions are:
- as antibodies (immunoglobulins), which are complex proteins produced by lymphocytes that play an important part in immunity.

Question 6

Clotting factors

Answer 6

These are responsible for coagulation of blood. Serum is plasma from which clotting factors have been removed. The most abundant clotting factor is fibrinogen

Question 7

Electrolytes

Answer 7

These have a range of functions, including muscle contraction, transmission of nerve impulses, and maintenance of acid–base balance

Question 8

Nutrients

Answer 8

The products of digestion, e.g., glucose, amino acids, fatty acids and glycerol, are absorbed from the alimentary tract.
Together with mineral salts and vitamins they are used by body cells for energy, heat, repair and replacement, and for the synthesis of other blood components and body secretions.

Question 9

Waste products

Answer 9

Urea, creatinine, and uric acid are the waste products of protein metabolism. They are formed in the liver and carried in the blood to the kidneys for excretion. Carbon dioxide from tissue metabolism is transported to the lungs for excretion

Question 10

Hormones

Answer 10

These are chemical messengers synthesized by endocrine glands. Hormones pass directly from the endocrine cells into the blood, which transports them to their target tissues and organs elsewhere in the body, where they influence cellular activity.

Question 11

Gases

Answer 11

Oxygen, carbon dioxide and nitrogen are transported round the body dissolved in plasma. Oxygen and carbon dioxide are also transported in combination with hemoglobin in red blood cells. Most oxygen is carried in combination with hemoglobin and most carbon dioxide as bicarbonate ions dissolved in plasma.

Question 12

Cellular content of blood

Answer 12

There are three types of blood cell
-erythrocytes (red cells)
-platelets (thrombocytes)
-leukocytes (white cells)
Blood cells are synthesized mainly in red bone marrow.
In the bone marrow, all blood cells originate from pluripotent (i.e., capable of developing into one of several cell types) stem cells and go through several developmental stages before entering the blood

Question 13

Erythrocytes

Answer 13

Red blood cells are by far the most abundant type of blood cell; 99% of all blood cells are erythrocytes.
Their main function is in gas transport, mainly of oxygen, but they also carry some carbon dioxide.
Their characteristic shape is suited to their purpose; the biconcavity increases their surface area for gas exchange, and the thinness of the central portion allows fast entry and exit of gases

Question 14

Hemoglobin

Answer 14

Hemoglobin is a large, complex molecule containing a globular protein (globin) and a pigmented iron-containing complex called haem.
Each hemoglobin molecule contains four globin chains and four haem units, each with one atom of iron.
Iron is carried in the bloodstream bound to its transport protein, transferrin, and stored in the liver.

Question 15

Oxygen transport

Answer 15

When all four oxygen-binding sites on a hemoglobin molecule are full, it is described as saturated.
As the oxygen content of blood increases, its color changes too. Blood rich in oxygen (usually arterial blood) is bright red because of the high levels of oxyhemoglobin it contains, compared with blood with lower oxygen levels (usually venous blood), which is dark bluish in color because it is not saturated.

Question 16

Low pH

Answer 16

Metabolically active tissues, e.g., exercising muscle, release acid waste products, and so the local pH falls. Under these conditions, oxyhemoglobin readily breaks down, giving up additional oxygen for tissue use

Question 17

Low oxygen levels (hypoxia)

Answer 17

Where oxygen levels are low, oxyhemoglobin breaks down, releasing oxygen. In the tissues, which constantly consume oxygen, oxygen levels are always low. This encourages oxyhemoglobin to release its oxygen to the cells.

Question 18

Temperature

Answer 18

Actively metabolizing tissues, which have higher than normal oxygen needs, are warmer than less active ones, which drive the equation above to the left, increasing oxygen release. This ensures that very active tissues receive a higher oxygen supply than less active ones.

Question 19

Control of Erythropoiesis

Answer 19

Red cell numbers remain constant, because the bone marrow produces erythrocytes at the rate at which they are destroyed. This is due to a homeostatic negative feedback mechanism. The hormone that regulates red blood cell production is erythropoietin, produced mainly by the kidney.

Question 20

Destruction of erythrocytes

Answer 20

he life span of erythrocytes is about 120 days and their breakdown, or hemolysis, is carried out by phagocytic reticuloendothelial cells.
• These cells are found in many tissues, but the main sites of hemolysis are the spleen, bone marrow and liver. As erythrocytes age, their cell membranes become more fragile and so more susceptible to hemolysis.

Question 21

Blood groups

Answer 21

There are four major blood groups determined by the presence or absence of two antigens – A and B – on the surface of red blood cells. In addition to the A and B antigens, there is a protein called the Rh factor, which can be either present (+) or absent (–), creating the 8 most common blood types (A+, A-, B+, B-, O+, O-, AB+, AB-).

Question 22

The ABO system

Answer 22

A system of four basic types (A, AB, B, and O) into which human blood may be classified, based on the presence or absence of certain inherited antigens.

Question 23

The rhesus system

Answer 23

System for classifying blood groups according to the presence or absence of the Rh antigen, often called the Rh factor, on the cell membranes of the red blood cells (erythrocytes). About 85% of people have this antigen; they are Rhesus positive (Rh+) and do not therefore make anti-Rhesus antibodies. The remaining 15% have no Rhesus antigen (they are Rhesus negative.

Question 24

Leukocytes (White blood cells)

Answer 24

a colorless cell that circulates in the blood and body fluids and is involved in counteracting foreign substances and disease

Question 25

Granulocytes

Answer 25

Granulocytes are a category of white blood cells in the innate immune system characterized by the presence of specific granules in their cytoplasm.

Question 26

Neutrophils

Answer 26

Neutrophils are a type of white blood cell. In fact, most of the white blood cells that lead the immune system’s response are neutrophils.
They are our “ first responders “ playing the role of the first line of defense against infectious organisms that enter our bodies.

Question 27

Eosinophils

Answer 27

Eosinophils are a type of disease-fighting white blood cell.

Question 28

Basophils

Answer 28

Basophils are a type of white blood cell. Although they are produced in the bone marrow, they are found in many tissues throughout your body.
They are part of your immune system and play a role in its proper function.

Question 29

Agranulocytes

Answer 29

The monocytes and lymphocytes make up 25 to 50% of the total leukocyte count. They have a large nucleus and no cytoplasmic granules.

Question 30

Monocytes

Answer 30

The Front Lines of Your Immunity. Monocytes are the largest type of white blood cell.
Monocytes are important in the immune system’s ability to destroy invaders, but also in facilitating healing and repair. Monocytes are formed in the bone marrow and are released into peripheral blood, where they circulate for several days.

Question 31

The monocyte- Macrophage system

Answer 31

Consists of the body’s complement of monocytes and macrophages. Some macrophages are mobile, whereas others are fixed, providing effective defense at key body locations.

Question 32

Lymphocytes

Answer 32

A type of immune cell that is made in the bone marrow and is found in the blood and in lymph tissue. The two main types of lymphocytes are B lymphocytes and T lymphocytes

Question 33

Platelets

Answer 33

small colorless disk-shaped cell fragment without a nucleus, found in large numbers in blood and involved in clotting

Question 34

Hemostasis

Answer 34

When a blood vessel is damaged, loss of blood is stopped and healing occurs in a series of overlapping processes, in which platelets play a vital part. The more badly damaged the vessel wall is, the faster coagulation begins, sometimes as quickly as 15 seconds after injury.

Question 35

vasoconstriction

Answer 35

When platelets meet a damaged blood vessel, their surface becomes sticky, and they adhere to the damaged wall. They then release serotonin, which constricts (narrows) the vessel, reducing or stopping blood flow through it.

Question 36

Platelets plug formation

Answer 36

Platelets plug formation is considered a positive feedback process because ADP and VWF levels are successively increased as more and more platelets activate to form the plug.

Question 37

Coagulation

Answer 37

This is a complex process that also involves a positive feedback system and only a few stages are included here.

Question 38

Fibrinolysis

Answer 38

The enzymatic breakdown of the fibrin in the blood clots.
Plasmin breaks down fibrin to soluble products that are treated as waste material and removed by phagocytosis. As the clot is removed, the healing process restores the integrity of the blood vessel wall.

Question 39

Control of coagulation

Answer 39

The process of blood clotting relies heavily on several self-perpetuating processes – that is, once started, a positive feedback mechanism promotes their continuation.
The main controls are:
-the perfect smoothness of normal blood vessel lining prevents platelet adhesion in healthy, undamaged blood vessels

Question 40

Anemias

Answer 40

Anemia is the inability of the blood to carry enough oxygen to meet body needs.
Usually this is because there are low levels of hemoglobin in the blood, but sometimes it is due to production of faulty hemoglobin.
Anemia is classified depending on the cause:
-production of insufficient or defective erythrocytes.
-blood loss or excessive erythrocyte breakdown (hemolysis)