AP 2 4.2: Anatomy of the Blood

Question 1

Blood

Answer 1

Blood is classified as a connective tissue. Blood (Figure 4.12) has two main portions: the liquid portion, called plasma, and the cell portion, called formed elements.

Question 2

plasma

Answer 2

two main portions: the liquid portion, called plasma

Question 3

formed elements

Answer 3

Blood has two main portions: the liquid portion, called plasma, and the cell portion, called formed elements.

Formed elements consist of red blood cells, white blood cells, and platelets.

Question 4

Serum

Answer 4

Serum is identical to plasma, except that the clotting proteins have been removed. This is accomplished by letting blood sit in a tube until it clots and then centrifuging the sample to separate the solid and liquid portions of the blood. Serum is used in many laboratory tests.

Question 5

Plasma, the liquid portion, has several important functions

Answer 5

First, it helps to buffer the pH of the blood, keeping the pH near 7.4. Plasma also assists in transporting large organic molecules in blood and aids in blood clotting. Finally, plasma maintains the blood’s osmotic pressure because of the presence of proteins in the plasma.

Question 6

Osmotic pressure

Answer 6

is the net pressure in the blood that moves fluid from the tissues into the circulatory system. Osmotic pressure is driven by proteins in the plasma that remain in the capillaries. In the case of blood at the capillaries, water has an automatic tendency to flow towards the proteins, pulling fluids back into the circulatory system.

Question 7

hydrostatic pressure

Answer 7

Osmotic pressure opposes the hydrostatic pressure of the blood, which pushes fluid into the tissues by the pressure of blood pumping from the heart. It is important for the body’s homeostasis to have an ongoing balance between osmotic and hydrostatic pressures so that fluids flow into the tissues and then return to the circulatory system.

Question 8

Red blood cells (erythrocytes)

Answer 8

Red blood cells (erythrocytes) are small biconcave disks that carry oxygen (Figure 4.13). They are the most abundant cell in the blood. There are 4 million to 6 million red blood cells per 1.0 mm3 of whole blood. Each red blood cells contains about 250 million hemoglobin molecules.

Question 9

Hemoglobin

Answer 9

Hemoglobin contains iron that combines loosely with oxygen, helping to carry oxygen in the blood. Red blood cells are manufactured continuously in the red bone marrow of the skull, ribs, vertebrae, and the ends of the long bones.

Question 10

anucleate

Answer 10

Mature red blood cells are anucleate, or without a nucleus. Red blood cells must lose their nucleus and synthesize hemoglobin before they are released into blood. Red blood cells live for about 120 days and then are destroyed in the liver and spleen. When red blood cells are destroyed, the hemoglobin is released so that the iron can be recycled and returned to the red bone marrow for reuse. The heme portions of the molecules undergo chemical degradation and are excreted by the liver as bile pigments.

Question 11

White blood cells

Answer 11

White blood cells are also called leukocytes. White blood cells differ from red blood cells in several ways: They are larger, have a relatively large nucleus, and lack hemoglobin.

Question 12

inflammatory response

Answer 12

When microorganisms enter the body due to an injury, the body responds through the inflammatory response because there is swelling and reddening at the injured site. The swelling and redness is due to an increase in blood flow to the injured site, which helps to deliver the immune defense cells. The white blood cells squeeze through the capillary walls and enter the tissue fluid, where they destroy any foreign material. The thick, yellowish fluid called pus contains a large proportion of dead white blood cells that have fought the infection and then undergo cell death.

Question 13

several different types of white blood

Answer 13

There are several different types of white blood cells. White blood cells are divided into three groups: granulocytes, agranulocytes, and lymphocytes.

Question 14

Granulocytes

Answer 14

Granulocytes have granules in the cytoplasm while agranulocytes do not. Granulocytes include neutrophils, eosinophils, and basophils.

Question 15

lymphocytes

Answer 15

The two main types of lymphocytes include T-cells and B-cells. The functions of all white blood cells will be discussed in more detail with the lymphatic system.

Question 16

Blood Platelets

Answer 16

Platelets (thrombocytes) are involved in the process of blood clotting, or coagulation. Platelets are not true “cells,” rather they are fragments of a large bone marrow predecessor called a megakaryocyte. When a blood vessel is broken, platelets help stop bleeding by sticking to the edges of the wound and begin to clot the opening.

Question 17

coagulation cascade

Answer 17

When a blood vessel in the body is damaged, platelets clump at the site of the puncture and begin to partially seal the leak. Once they begin to stick to the tear in the blood vessel, platelets release chemicals to help signal the coagulation cascade, or a series of events to start the blood clotting mechanism.

Question 18

prothrombin activator

Answer 18

The platelets and the injured tissues release a clotting factor called prothrombin activator that converts prothrombin to thrombin.

Question 19

fibrinogen

Answer 19

Blood clotting also needs the involvement of fibrinogen, a protein manufactured by the liver that freely floats in the blood. Thrombin helps to convert fibrinogen to activated fibrin. Fibrin threads wind around the platelet plug in the damaged area of the blood vessel and provide the framework for the clot. Red blood cells also become trapped within the fibrin threads, which make the clot appear red.

Question 20

platelet plug

Answer 20

The network of fibrin and platelets work together to form a platelet plug to stop the bleeding but is present only temporarily.