Anatomy Ch 17 - Blood

What are the very basic steps of erythropoiesis?

1. A hemocytoblast is transformed into a proerythroblast 2. Proerythroblasts develop into early erythroblasts

The fact that hemoglobin is contained in erythrocytes, rather than existing free in plasma, prevents it from what?

1. Breaking into fragments hat would leak out of the bloodstream through porous capillary walls 2. Making blood more viscous and raising osmotic pressure

What are the distribution functions of blood?

1. Delivering a)oxygen from the lungs and b) nutrients from the digestive tract to all body cells 2. Transporting metabolic waste products from cells to elimination sites (to the lungs to eliminate carbon dioxide, and to the kidneys to dispose of nitrogenous wastes in urine) 3. Transporting hormones from the endocrine organs to their target organs

Importance of water in blood plasma

1. Dissolving and suspending medium for solutes of the blood 2. Absorbs heat

What are all functions that blood performs concerned with in one way or another?

1. Distributing substances (DISTRIBUTION) 2. Regulating blood levels of particular substances (REGULATION) 3. Protecting the body (PROTECTION)

What are the regulatory functions of the blood?

1. Maintaining appropriate body temperature by absorbing and distributing heat throughout the body and to the skin surface to encourage heat loss 2. Maintaining normal pH in body tissues (many blood proteins and other bloodborne solutes act as buffers to prevent excessive or abrupt changes in blood pH that could jeopardize normal cell activities; also, blood acts as the reservoir for the body's "alkaline reserve" of bicarbonate ions)

What are the protective functions of the blood?

1. Preventing blood loss (when a blood vessel is damaged, platelets and plasma proteins initiate clot formation, halting blood loss) 2. Preventing infection (drifting along in blood are antibodies, complement proteins, and white blood cells, all of which help defend the body against foreign invaders such as bacteria and viruses)

What are the phases in RBC development?

1. Ribosome synthesis 2. Hemoglobin accumulation 3. Ejection of the nucleus and formation of reticulocytes Reticulocytes then become mature erythrocytes.

Globulins dissolved in the blood plasma

36% of plasma proteins; include alpha, beta, and gamma types

Fibrinogen dissolved in the blood plasma

4% of plasma proteins; produced by liver; forms fibrin threads of blood clot

Albumin dissolved in the blood plasma

60% of plasma proteins; produced by liver; main contributor to osmotic pressure. Albumin acts as a carrier to shuttle certain molecules through the circulation, is an important blood buffer, and is the major blood protein contributing to the plasma osmotic pressure.

Plasma proteins dissolved in the blood plasma

8% (by weight) of plasma; all contribute to osmotic pressure and maintain water balance in blood and tissues; all have other functions as well

What regulates the formation of platelets?

A hormone called thrombopoietin. Megakaryocytes, the ancestral cells of platelets, are also progeny of hematocytoblasts (and the myeloid stem cell, which is also the precursor of eosinophils, basophils, neutrophils, and monocytes - all leukocytes except lymphocytes).

Blood plasma

A straw-colored, sticky fluid that is mostly water (~90%) but also contains over 100 different dissolved solutes including nutrients, gases, hormones, wastes and products of cell activities, proteins, and inorganic ions (electrolytes - VASTLY outnumber the other solutes)

What is leukocytosis?

A white blood cell count of over 11,000 cells per microliter. Whenever white blood cells are mobilized for action, the body speeds up their production and their numbers may double within a few hours. This condition is a normal homeostatic response to an infection in the body.

Functionally, what are all granulocytes?

All granulocytes are functionally phagoccytes to some degree.

What is leukopenia?

An abnormally low WBC count (penia = poverty), commonly induced by drugs, particularly glucocorticoids and anticancer agents.

Gamma globulins dissolved in the blood plasma

Antibodies released by plasma cells during immune response

What is the function of B lymphocytes (B cells)?

B cells give rise to plasma cells, which produce antibodies (immunoglobulins) that are released to the blood.

What are erythrocytes shaped like?

Biconcave discs (flattened discs with depressed centers).

How does the density and viscosity of blood compare to that of water?

Blood is more dense than water and about five times more viscous, largely because of its formed elements (erythrocytes, leukocytes, and platelets).

Which tissue do clinicians examine more often than any other tissue when trying to determine the cause of disease in their patients?

Blood.

What is the only fluid tissue in the body?

Blood. It appears to be a thick, homogeneous liquid, but the microscope reveals that it has both cellular and liquid components.

How do carbon dioxide and wastes move from the tissues to the bloodstream?

By diffusing across the capillary walls.

How do oxygen and nutrients leave the blood and enter the body tissues?

By diffusing across the capillary walls.

Nonprotein nitrogenous substances dissolved in the blood plasma

By-products of cellular metabolism, such as urea, uric acid, creatinine, and ammonium salts

What are the signals that prompt WBCs to leave the bloodstream at specific locations?

Cell adhesion molecules displayed by endothelial cells forming the capillary walls at sites of inflammation,

What happens if we spin a sample of blood in a centrifuge?

Centrifugal force packs down the heavier formed elements (the living blood cells) and the less dense plasma remains at the top. Most of the reddish mass at the bottom of the tube is erythrocytes, the red blood cells that transport oxygen. A thin, whitish layer called the buffy coat is present at the erythrocyte-plasma junction. This layer contains leukocytes, the white blood cells that act in various ways to protect the body, and platelets, cell fragments that help stop bleeding.

Like erythropoiesis, what stimulates leukopoiesis (the production of WBCs)?

Chemical messengers. These chemical messengers, which can act either as paracrines or hormones, are glycoproteins that fall into two families of hematopoietic factors, interleukins and colony-stimulating factors (CSFs). The interleukins are numbered (e.g. IL-3 and IL-5) but most CSFs are named for the leukocyte population they stimulate (e.g. granulocyte-CSF or G-CSF stimulates granulocyte production).

What are platelets?

Cytoplasmic fragments of extraordinarily large cells called megakaryocytes.

What color is blood?

Depending on the amount of oxygen it is carrying, the color of blood varies from scarlet (oxygen-rich) to dark red (oxygen-poor).

What are the recognizable characteristics of eosinophils?

Eosinophils are approximately the size of neutrophils. Their nucleus has two lobes connected by a broad band of nuclear material, resembling an old-fashioned telephone receiver. Large, coarse granules that stain from brick red to crimson with acid (eosin) dyes pack the cytoplasm. These granules are lysosome-like and filled with a unique variety of digestive enzymes. BUT, unlike typical lysosomes, they lack enzymes that specifically digest bacteria.

How do erythrocytes exhibit the complementarity of structure and function?

Erythrocytes pick up oxygen in the capillaries of the lungs and release it to tissue cells across other capillaries throughout the body. They also transport ~20% of the carbon dioxide released by tissue cells back to the lungs. Three structural characteristics allow for erythrocytes to successfully transport gas: 1. Its small size and biconcave shape provide a huge surface area relative to volume - the biconcave disc shape is ideally suited for gas exchange because no point within the cytoplasm is far from the surface. 2. Discounting water content, an erythrocyte is over 97% hemoglobin, the molecule that binds to and transports respiratory gases. 3. Because erythrocytes lack mitochondria and generate ATP by anaerobic mechanisms, they do not consume any of the oxygen they carry, making them very efficient oxygen transporters.

Which of the formed elements vastly outnumbers the other types?

Erythrocytes vastly outnumber the other types of formed elements.

What are the formed elements of blood?

Erythrocytes, leukocytes, and platelets.

What are the major factor contributing to blood viscosity?

Erythrocytes. When the number of RBCs increases beyond the normal range, blood becomes more viscous and flows more slowly. Similarly, as the number of RBCs drops below the lower end of the range, the blood thins and flows more rapidly.

What is erythrocyte production called?

Erythropoiesis

What are the other body cells similar to basophils?

Granulated cells called mast cells found in connected tissues. Mast cell nuclei tend to be more oval than lobed, but the cells are microscopically similar and both bind to immunoglobulin E, which causes them to release histamine.

What are the two major categories that leukocytes are grouped into on the basis of structural and chemical characteristics?

Granulocytes (contain obvious membrane-bound cytoplasmic granules) and agranulocytes (lack obvious granules).

Where does hematopoiesis occur?

Hematopoiesis occurs in the red bone marrow, which is composed largely of a soft network of reticular connective tissue bordering on wide blood capillaries called blood sinusoids. Within this network are immature blood cells, macrophages, fat cells, and reticular cells (which secrete the connective tissue fibers). In adults, red marrow is found chiefly in the bones of the axial skeleton and girdles, and in the proximal epiphyses of the humerus and femur.

What is the process of blood cell formation called?

Hematopoiesis.

What cells to leukocytes arise from?

Hematopoietic stems cells (hemocytoblasts) - the same ancestral cells of RBCs.

What is hemoglobin made up of?

Hemoglobin is made up of the red heme pigment bound to the protein globin. Globin consists of four polypeptide chains - two alpha and two beta - each binding a ringlike heme group. Each heme group bears an atom of iron in its center. A hemoglobin molecule can transport four molecules of oxygen because each iron atom can combine reversibly with one molecule of oxygen.

What protein makes RBCs red?

Hemoglobin.

What is histamine?

Histamine is an inflammatory chemical that acts as a vasodilator and attracts other white blood cells to the inflamed site.

Most plasma proteins are produced by the liver. Which ones are NOT?

Hormones and gamma globulins.

Which antibody do basophils bind, and what is the result?

Immunoglobulin E, which causes the cell to release histamine.

What is the hallmark of infectious mononucleosis?

It is caused by the Epstein-Barr virus, and its hallmark is excessive numbers of agranulocytes, many of which are atypical. There is no cure, but with rest the condition typically runs its course.

What is the pH of blood?

It is slightly alkaline, with a pH between 7.35 and 7.45.

What is the most important role of eosinophils?

Leading the counter-attack against parasitic worms, such as flatworms (tapeworms and flukes) and roundworms (pinworms and hookworms) that are TOO LARGE TO BE PHAGOCYTIZED. These worms are ingested in food (especially raw fish) or invade the body via the skin and then typically burrow into the intestinal or respiratory mucosae. Eosinophils reside in the loose connective tissues at the same body sites, and when they encounter a parasitic worm "prey", they gather around and release the enzymes from their cytoplasmic granules onto the parasite's surface, digesting it away.

Which of the formed elements are the only complete cells?

Leukocytes (WBCs).

Which WBCs are agranulocytes?

Lymphocytes and monocytes (Lack Masses). These WBCs are similar structurally but are functionally distinct. Their nuclei are spherical or kidney shaped.

Nutrients (organic) dissolved in the blood plasma

Materials absorbed from digestive tract and transported for use throughout body; include glucose and other simple carbs, amino acids, fatty acids, glycerol and triglycerides, cholesterol, and vitamins

Describe mature erythrocytes.

Mature erythrocytes are bound by a plasma membrane, but lack a nucleus and have essentially no organelles. They are basically "bags" of hemoglobin (Hb), the RBC protein that functions in gas transport. Other proteins are present, such as antioxidant enzymes that rid the body of harmful oxygen radicals, but most function as structural proteins, allowing the RBC to deform yet spring back into shape. For example, a network of proteins, especially one called spectrin, attached to the cytoplasmic face of RBC plasma membranes maintains the biconcave shape of an erythrocyte. The spectrin net is deformable, allowing erythrocytes to change shape as necessary as they are carried passively through capillaries with diameters smaller than themselves and then to resume their biconcave shape.

Electrolytes dissolved in the blood plasma

Most abundant solutes by number; cations include sodium, potassium, calcium, magnesium; anions include chloride, phosphate, sulfate, and bicarbonate. They help to maintain plasma osmotic pressure and normal blood pH.

Where are most lymphocytes found?

Most are closely associated with lymphoid tissues (lymph nodes, spleen, etc.) where they play a crucial role in immunity. Relatively few are found in the blood stream.

What is the status of most oxygen carried in blood?

Most oxygen carried in blood is bound to hemoglobin.

What are the recognizable characteristics of neutrophils?

Neutrophil nuclei consist of three to six lobes. The neutrophil cytoplasm contains very fine granules (of two varieties) that are often difficult to see. Their granules take up both basic (blue) and acidic (red) dyes. Together, the two types of granules give the cytoplasm a lilac color. Some of these granules contain hydrolytic enzymes, and are regarded as lysosomes. Others, especially the smaller granules, contain a potent "brew" of antimicrobial proteins, called defensins. Neutrophils are about twice as large as RBCs.

What do neutrophils do?

Neutrophils are our body's bacteria slayers, and their nnumbers increase explosively during acute bacterial infections such as meningitis and appendicitis. Neutrophils are chemically attracted to sights of inflammation and are active phagocytes.

Which WBCs are granulocytes?

Neutrophils, eosinophils, and basophils (Never Eat Bananas). They are larger and much shorter lived (usually) than erythrocytes. They characteristically have lobed nuclei (rounded nuclear masses connected by thinner strands of nuclear material), and their membrane-bound cytoplasmic granules stain quite specifically with Wright's stain.

List the leukocytes in order from most abundant to least abundant.

Never Let Monkeys Eat Bananas (neutrophils, lymphocytes, monocytes, eosinophils, basophils).

Is the composition of plasma consistent?

No, the composition of plasma varies continuously as cells remove or add substances to the blood. HOWEVER, assuming a healthy diet, plasma composition is kept relatively constant by various homeostatic mechanisms. For example, when blood protein levels drop undesirably, the liver makes more proteins. When the blood starts to become too acidic (acidosis), both the lungs and the kidneys are called into action to restore plasma's normal, slightly alkaline pH. Body organs make dozens of adjustments to maintain the many plasma solutes at life-sustaining levels.

Do the two types of agranulocytes have the same lineage?

No. Despite their similar appearance, the two types of agranulocytes (lymphocytes and monocytes) have very different lineages. Monocytes are derived from myeloid stem cells, as are neutrophils, eosinophils, and basophils. T and B cells are derived from the lymphoid stem cell.

Are all of the formed elements true cells?

No. Erythrocytes have no nuclei or organelles, and platelets are cell fragments. Only leukocytes are complete cells.

Do most blood cells divide?

No. Instead, stem cells divide continuously in red bone marrow to replace them.

Do T and B cells mature in the same location?

No. T lymphocyte precursors leave the bone marrow and travel to the thymus, where their further differentiation occurs. B lymphocyte precursors remain and mature in the bone marrow.

Are WBCs confined to the blood stream?

No. WBCs are able to slip out of the capillary blood vessels (a process called diapedesis - "leaping across") and the circulatory system is simply their means of transport to areas of the body (mostly loose connective tissues or lymphoid tissues) where they mount inflammatory or immune responses.

What occurs in leukemia and infectious mononucleosis?

Overproduction of abnormal leukocytes.

What occurs in all leukemias?

Overproduction of abnormal white blood cells. As a rule, the renegade leukocytes are members of a single clone (descendants of a single cell) that remain unspecialized and proliferate out of control, impairing normal red bone marrow function. Cancerous leukocytes fill the red bone marrow and immature WBCs flood into the bloodstream. The other blood cell lines are crowded out, so severe anemia and bleeding problems result. Although tremendous numbers of leukocytes are produced, they are nonfunctional and cannot defend the body.

Respiratory gases dissolved in blood plasma

Oxygen and carbon dioxide; oxygen mostly bound to hemoglobin inside RBCs; carbon dioxide transported dissolved as bicarbonite ion or CO2, or bound to hemoglobin in RBCs

What is the basic function of a monocyte?

Phagocytosis (develop into macrophages in the tissues).

What is the difference between plasma proteins and most other organic solutes, such as glucose, fatty acids, and amino acids?

Plasma proteins are NOT taken up by cells to be used as fuels or metabolic nutrients as are most other organic solutes.

What are platelets required for?

Platelets are essential for the clotting process that occurs in plasma when blood vessels are ruptured or their lining is injured. By sticking to the damaged sitem platelets form a temporary plug that helps seal the break.

Alpha and beta globulins dissolved in the blood plasma

Produced by the liver; most are transport proteins that bind to lipids, metal ions, and fat-soluble vitamins

What process performed by neutrophils promotes bacterial killing?

Respiratory burst - the cells metabolize oxygen to produce potent germ-killer oxidizing substances such as bleach and hydrogen peroxide. In addition, defensin-mediated lysis occurs when the granules containing defensins merge with a microbe-containing phagosome.

What kind of tissue is blood?

Specialized connective tissue. Blood lacks the collagen and elastic fibers typical of other connective tissues, but dissolved fibrous proteins become visible as fibrin strands during blood clotting.

Hormones dissolved in blood plasma

Steroid and thyroid hormones carried by plasma proteins

What is the function of T lymphocytes (T cells)?

T cells function in the immune response by ACTING DIRECTLY AGAINST VIRUS-INFECTED CELLS AND TUMOR CELLS.

What do all formed elements arise from?

The hematopoietic stem cell. These undifferentiated precursor cells reside in the red bone marrow. However, the maturation pathways of the various formed elements differ, and once a cell is committed to a specific blood cell pathway, it cannot change. This commitment is signaled by the appearance of membrane surface receptors that respond to specific hormones or growth factors, which in turn "push" the cell toward further specialization.

Hematocrit

The percentage of the total volume of a blood sample that is made up of erythrocytes. In healthy males the norm is 47%. In healthy females the norm is 42%. Leukocytes and platelets contribute less than 1% of blood volume. Plasma makes up most of the remaining 55% of whole blood.

Plasma osmotic pressure

The pressure that helps to keep water in the bloodstream.

What initiates blood circulation?

The pumping action of the heart.

What is the rate of new red blood cell production controlled by? What does it depend on?

The rate of new RBC production is controlled hormonally and depends on adequate supplies of iron, amino acids, and certain B vitamins.

What are the recognizable characteristics of basophils?

Their cytoplasm contains large, coarse, histamine-containing granules that have an affinity for the basic dyes (basophil=base loving) and stain purplish-black. The deep purple nucleus is generally U or S shaped with one or two conspicuous constrictions.

What are the recognizable characteristics of platelets?

They are about one-fourth the diameter of lymphocytes. In blood smears, each platelet exhibits a blue-staining outer region and an inner area containing granules that stain purple. The granules contain an impressive array of chemicals that act in the clotting process,, including SERATONIN, Ca2+, a variety of enzymes, ADP, and platelet-derived growth factor (PDGF). Because they are anucleate, they age quickly and degenerate in about 10 days if they are not involved in clotting.

What are the recognizable characteristics of monocytes?

They are the largest leukocytes. They have abundant pale blue cytoplasm and a darkly staining purple nucleus, which is distinctively U or kidney shaped.

What do platelets do when they are not involved in clotting?

They circulate freely, kept mobile but inactive by molecules (nitric oxide and prostacyclin) secreted by endothelial cells lining the blood vessels.

What happens when circulating monocytes leave the bloodstream and enter the tissues (undergo diapedesis)?

They differentiate into highly mobile macrophages. Macrophages are actively phagocytic, and they are crucial in the body's defense against VIRUSES, CERTAIN INTRACELLULAR BACTERIAL PARASITES, AND CHRONIC INFECTIONS (such as tuberculosis). Macrophages are also important in activating lymphocytes to mount the immune response.

What is the basic function of an eosinophil?

To kill parasitic worms. They also play a complex role in allergy and asthma.

What is the basic function of a lymphocyte?

To mount the immune response by a)direct cell attack or b)via antibodies.

What is the basic function of a neutrophil?

To phagocytize bacteria.

What is the basic function of a basophil?

To release histamine and other mediators of inflammation. They also contain heparin, an anticoagulant.

What is the basic function of platelets?

To seal small tears in blood vessels. They are instrumental in blood clotting.

What is the basic function of an erythrocyte?

To transport oxygen and carbon dioxide.

Once out of the blood stream, how do leukocytes move through the tissue spaces?

Via amoeboid motion (they form flowing cytoplasmic extensions that move them along). By following the chemical trail of molecules released by damaged cells or other leukocytes, a phenomenon called positive chemotaxis, they pinpoint areas of tissue damage and infection and gather there in large numbers to destroy foreign substances and dead cells.

What are the recognizable characteristics of lymphocytes?

When stained, a typical lymphocyte has a large, dark-purple nucleus that occupies most of the cell volume. The nucleus is usually spherical but may be slightly indented, and it is surrounded by a thin rim of pale-blue cytoplasm.

Do granulocytes have a shorter life span than RBCs?

Yes, granulocytes have a much shorter life span (usually 0.25 to 9 days) than RBCs. Most die combating invading microbes. This ratio is reflected by the normal ratio of granulocytes to erythrocytes produced, which is about 3:1.

Is the number of circulating erythrocytes in a given individual constant?

Yes, the number of circulating erythrocytes in a given individual is remarkably constant and reflects a balance between red blood cell production and destruction. This balance is important because having too few erythrocytes leads to tissue hypoxia (oxygen deprivation), whereas having too many makes the blood undesirably viscous.

Are RBCs confined to the blood stream?

Yes.

Does the bone marrow store mature granulocytes?

Yes.