blood-plasma and formed elements

what is blood

• the circulating portion of extracellular fluid

• type of connective tissue

• composed of plasma and formed elements

what are the types of extracellular fluid

• plasma

• interstitial fluid

• cerebrospinal fluid

• lymph

what percent of extracellular is made up of plasma

25% of all extracellular fluid

what are the formed elements in blood

• erythrocytes (RBCs)

• leukocytes (WBCs)

• platelets

what is the total blood volume in a 155 lb person and what is the ratio of this total volume of plasma to formed elements

• total blood volume is equal to 5 liters of blood or about 7% of total body weight

• three liters is plasma and two liters is formed elements

what is plasma composed of

• fluid portion of the blood

• formed elements are suspended in plasma

• it is 92% water

• 7% proteins

• 1% dissolved organic molecules (amino acids, glucose, lipids, and nitrogenous waste), ions (sodium, potassium, chloride, hydrogen, calcium, and hydrogen carbonate), trace elements, vitamins, dissolved oxygen and carbon dioxide

how does plasma compare to interstitial fluid

• plasma is identical to interstitial fluid except for the presence of plasma proteins

• examples - albumins, globulins, and fibrinogen (clotting protein)

what organ produces most of the plasma proteins

the liver makes most of the plasma proteins and secretes them into the blood

what do proteins in the plasma do to the osmotic pressure of blood

• proteins in the plasma make the osmotic pressure of blood higher (more concentrated) than that of interstitial fluid

• this gradient pulls water from the interstitial fluid into the capillaries via absorption

what is the source and function of albumins

• the liver is the source

• they function as major contributors to colloid osmotic pressure of plasma and as carriers for various substances

what is the source and function of globulins

• the source is the liver and lymphoid tissue

• they function as clotting factors, enzymes, antibodies, and carriers for various substances

what is the source and function of fibrinogen

• the source is the liver

• functions to form fibrin threads essential to blood clotting

what is the source and function of transferrin

• the source is the liver and other tissues

• its function is iron transport

what is capillary filtration caused by

• it is caused by the lateral pressure of blood on capillary walls

• this pressure pushes plasma-like fluid out through intercellular clefts and filtration pores

what is capillary absorption caused by

• it is caused by colloid osmotic pressure

• plasma is always more concentrated than interstitial fluid due to the presence of its blood cells and plasma proteins

• absorption of plasma-like fluid back into the capillaries occurs because water always moves down its concentration gradient

• in this case, it moves from the less concentrated interstitial fluid to the more concentrated blood plasma

what is the function of erythrocytes

they function to transport oxygen and carbon dioxide between the lungs and tissues

what are platelets and what is their function

• they are cell fragments that have split off a parent cell known as a megakaryocyte

• they function in coagulation which is a process by which blood clots to prevent blood loss in damaged vessels

what are leukocytes and what is their function

• they are the only one of the formed elements with a nucleus

• they circulate in the blood but their work is carried out in the tissues

• they function to defend the body against parasites, bacteria, and viruses

what are the five types of mature leukocytes

• basophils

• neutrophils

• eosinophils

• monocytes

• lymphocytes

what are the granulocytes and why are they categorized as such

• basophils, neutrophils, and eosinophils are granulocytes

• they are called this because they contain cytoplasmic inclusions that give them a granular appearance

what are the phagocytic leukocytes and why are they categorized as such

• neutrophils, eosinophils, and monocytes/macrophages are phagocytic

• this means that they engulf and ingest foreign particles such as bacteria

which leukocytes are cytotoxic

eosinophils and some lymphocytes are cytotoxic

which leukocytes are antigen-presenting cells

monocytes and macrophages, lymphocytes, and dendritic cells are antigen-presenting cells

what are mast cells

they are basophils in the tissue

what are macrophages

they are monocytes that have left the circulation, entered the tissues, and developed into macrophages

what are lymphocytes responsible for

lymphocytes (B cells, T cells, natural killer cells) are responsible for specific immune responses directed against invaders

what is the most abundant cell type in blood

erythrocytes

what is the primary function of erythrocytes

their primary function is to facilitate oxygen and carbon dioxide transport between the lungs and cells

what is hematocrit

it is the ratio of erythrocytes to plasma, expressed as a percentage of the total blood volume

how is hematocrit determined

• it is determined by using a centrifuge to spin a blood sample so that the heavier red blood cells go to the bottom of the tube

• the results look like a thick layer of red blood cells at the bottom, a thin layer of light leukocytes and platelets in the middle, and a thick layer of plasma on top

• the column of packed red cells is measured and compared to the total sample volume

what is the normal hematocrit levels for males and females

• a normal hematocrit for males is 40-54%

• a normal hematocrit for females is 37-47%

what cells are erythrocytes descendants of

they are descendants of pluripotent hematopoietic stem cells (single precursor cell type)

what are the steps of the development from pluripotent hematopoietic stem cells to erythrocytes

1. in the red bone marrow, committed stem cells differentiate into large nucleated erythroblasts

2. as the erythroblasts mature, the nucleus condenses and the cell shrinks in diameter

3. in the last stage before maturation, the nucleus is pinched off and phagocytized by marrow and macrophages; mitochondria break down and disappear

4. immature cell then leaves the red bone marrow, enters the circulation, and matures into an erythrocyte in 24 hours

what is the structure of mature erythrocytes

they are biconcave disks that lack a nucleus and other organelles

what functions are erythrocytes unable to carry out due to their lack of a nucleus and endoplasmic reticulum

• without a nucleus and endoplasmic reticulum to carry out protein synthesis, the erythrocyte is unable to make new enzymes or renew its membrane components

• this leads to an increasing loss of membrane flexibility, making older cells more fragile and likely to rupture

what functions are erythrocytes unable to carry out due to their lack of mitochondria

• since erythrocytes do not have mitochondria, they cannot carry out aerobic metabolism

• glycolysis is their primary source of ATP

what is the biconcave disc shape of an erythrocyte determined by

• it is determined by its flexible cytoskeleton

• it allows erythrocytes to change shape as they squeeze through the narrow capillaries of circulation like a partially filled water ballon that can compress into various shapes

• they are basically membranous bags filled with enzymes and hemoglobin

what is hemoglobin

• it is the oxygen carrying pigment of erythrocytes

• it is a quaternary structure with four globular protein chains, each wrapped around an iron containing heme group

• the four common forms of the globin protein chain are alpha, beta, gamma, and delta

what is hemoglobin synthesized by

it is synthesized by developing erythrocytes in the red bone marrow

what does hemoglobin synthesis require

it requires an adequate supply of iron in the diet

what is the process of the developing erythrocytes’ synthesis of hemoglobin

• iron is absorbed in the small intestine by active transport

• it is transported in the blood to the bone marrow

• developing erythrocytes use iron to make the heme portion of hemoglobin

• excess iron in the body is stored mostly in the liver

how long do erythrocytes in circulation live

erythrocytes in circulation live approximately 120 days

what risks increase for erythrocytes as they age

increasingly fragile older erythrocytes may rupture as they try to squeeze through narrow capillaries or they may be captured by macrophages as they pass through the spleen

in what ways is hemoglobin recycled once an erythrocyte ruptures or is captured by a macrophage

• amino acids from the globin chains become new proteins

• some iron from old heme groups is reused in new heme groups

• remainder of the old heme is converted by cells of the spleen and liver to a colored pigment called bilirubin

what is the cycle of bilirubin

1. bilirubin is carried by plasma albumin to the liver

2. metabolized and incorporated into a secretion called bile

3. bile is secreted into the digestive tract

4. bilirubin metabolites exit the body in feces

5. small amounts of other bilirubin metabolites are filtered from the blood into the kidneys

6. these other bilirubin metabolites then contribute to the yellow color of urine

what does the biconcave disk structure of erythrocytes allow it to do

the disc structure allows erythrocytes to modify their shape in response to osmotic changes in the blood

what happens to erythrocytes placed in hypotonic fluid

• they will increase in size and form a sphere with (or without) disruption of its membrane

• called hemolysis if the membrane is disrupted

what happens to erythrocytes placed in hypertonic fluid

• they will decrease in size and develop a spiky surface when the membrane pulls tight against the cytoskeleton

• called crenation

what is anemia

this occurs when the hemoglobin count is too low and blood cannot transport enough oxygen to the tissues

what are the symptoms of anemia

weakness and fatigue, especially during exercise

what is hemolytic anemia

• when the rate of erythrocyte destruction exceeds the rate of red blood cell production (cells rupture at an abnormally high rate)

• this is one of the two things that can happen to cause the condition of anemia

what are the hereditary causes of hemolytic anemia

• membrane defects (such as hereditary spherocytosis)

• enzyme defects

• abnormal hemoglobin (such as sickle cell anemia)

what are the acquired causes of hemolytic anemia

• parasitic infections (such as malaria)

• drugs

• autoimmune reactions

other than accelerated red blood cell loss (hemolytic anemia), what is the other thing that can cause anemia

• decreased red blood cell production

• this includes defective red blood cell or hemoglobin synthesis in the bone marrow as well as inadequate production of erythropoietin

• under the category of defective RBC or hemoglobin synthesis in the bone marrow is aplastic anemia and inadequate dietary intake of essential nutrients

what causes aplastic anemia

can be caused by certain drugs or radiation

which essential nutrients can cause anemia if their intake is too low

• iron deficiency (iron is required for heme production)

• folic acid deficiency (folic acid is required for DNA synthesis)

• Vitamin B12 deficiency (B12 is required for DNA synthesis); may be due to a lack of intrinsic factor for B12 absorption

what is the most common type of anemia

• the most common type is iron deficiency anemia

• if iron loss exceeds iron intake, the marrow does not have adequate iron to make heme groups and hemoglobin synthesis slows

what is sickle cell disease

• genetic defect where the hemoglobin is anatomically abnormal

• crystallizes when it gives up its oxygen and pulls the erythrocytes into a sickle shape

which cells are responsible for the immune response of the body

leukocytes

how do luekocytes compared to erythrocytes in regards to number and size

• fewer in number than erythrocytes

• microliter of whole blood contains about 5 million erythrocytes and only about 7000 leukocytes

• larger in size than erythrocytes

where do leukocytes perform their main function

• although most leukocytes circulate in the blood, they usually leave the capillaries and function outside the vessels

• some types can live in the tissue for several months while others live only hours or days

what are the six types of leukocytes

• basophils in the blood, and mast cells in the tissues

• neutrophils

• eosinophils

• monocytes and their derivative macrophages

• lymphocytes and their derivative plasma cells

• dendritic cells (not usually found in blood)

how are the different types of leukocytes distinguished from one another

• by shape and size of the nucleus

• by staining characteristics of the cytoplasm and cytoplasmic inclusions

• by the regularity of the cell border

where do the names of each of the granulocytes come from

• names come from the staining properties of the granules

• basophil granules stain dark blue with basic (alkaline) dye

• eosinophil granules stain dark pink with the acidic dye eosin

• neutrophil granules do not stain darkly with standard blood stains so are considered neutral

how are the granule contents of the granulocytes released from the cell

in all three types of granulocytes, the granule contents are released from the cell via exocytosis in a process called degranulation

what is a cytotoxic cell

a cell that is capable of killing the cells it attacks

what is meant by the name antigen-presenting cells (APCs)

they are cells that display fragments of foreign proteins on their cell surface

what is a differential white blood cell count

systematically counting and identifying 100 leukocytes in a blood smear sample, and expressing the number of each type of leukocyte as a percent of the total counted

what are the expected ranges of different leukocyte percentages in a differential white blood cell count

• 50-70% neutrophils

• 20-30% lymphocytes

• 2-6% monocytes

• 1-5% eosinophils

• <1% basophils

what can a differential white blood cell count be used to clinically

used clinically to identify pathologies associated with changes in the percentages of particular leukocytes

what does a high number of neutrophils in a differential WBC count indicate

a high number of neutrophils indicates an acute bacterial infection such as appendicitis or strep throat

what does a high number of eosinophils in a differential WBC count indicate

a high number of eosinophils is related to intestinal parasites or allergic conditions

what does a high number of lymphocytes in a differential WBC count indicate

a high number of lymphocytes may signal the presence of infectious mononucleosis

what are the defining characteristics of basophils/mast cells

• they are rare in circulation

• they are easily recognized by the large dark blue granules in their cytoplasm

what is the function of basophils/mast cells

• they release mediators that contribute to inflammation

• granules contain histamine, heparin, cytokines, and other chemicals involved in allergic and immune responses

where are mast cells concentrated and why

• mast cells are concentrated in the connective tissue of skin, lungs, and the GI tract

• they are there to intercept pathogens that are inhaled or ingested or that enter through breaks in the epidermis

what is the identifying characteristic of a neutrophil

• they are most easily identified by a segmented nucleus of 3-5 lobes connected by thin strands of nuclear material

• they are called polymorphonuclear leukocytes because of their segmented nuclei

what does the typical lifespan of a neutrophil look like

they ingest and kill about 5-20 bacteria during their short programmed life span of 1-2 days

what is the function of neutrophils

they release a variety of cytokines including fever-causing pyrogens and chemical mediators of the inflammatory response

where are neutrophils formed and where do they stay

• they are formed in the bone marrow and released into circulation

• most remain in the blood but can leave the circulation if attracted to an extravascular site of damage or infection

• immature neutrophils (called bands, stabs) are sometimes found in circulation and can be identified by their horseshoe-shaped nucleus

how are eosinophils identified

they are easily recognizable by the bright pink staining granules in their cytoplasm

how long is the life span of an eosinophil

about 6-12 hours

where are eosinophils found

they are found in the GI tract, lungs, urinary and genital epithelia, and connective tissue of the skin

what is the function of eosinophils

• they function to defend against parasitic invaders

• they are known to attach to large antibody-coated parasites (i.e. blood fluke) and release substances from their granules that damage or kill the parasite

• they function in allergic reactions where they contribute to inflammation and tissue damage by releasing toxic enzymes, oxidative substances, and eosinophil-derived neurotoxin

how long does it take for monocytes to differentiate into macrophages

they spend only 8 hours in the blood, going from red bone marrow to their permanent positions as macrophages in the tissues

what do monocytes do once they reach the tissues they are headed for

• once in the tissues, monocytes enlarge and differentiate into phagocytic macrophages

• some macrophages patrol the tissues, creeping along the amoeboid motion; others find a location and remain fixed in place

which leukocytes are the primary scavengers in the tissues

macrophages

how do macrophages compare to neutrophils

• they are larger and more effective than neutrophils, ingesting up to 100 bacteria in their lifetime

• macrophages also remove larger particles like old erythrocytes and dead neutrophils

what is the function of macrophages

• they play an important role in developing acquired immunity because they are antigen-presenting cells

• after a macrophage ingests and digests molecular or cellular antigens, it can insert fragments of processed antigen into its membrane so that the antigen fragment becomes part of its surface protein complexes

what is the function of lymphocytes

lymphocytes (B cells, T cells, and natural killer cells) mediate the immune response of the body

where are lymphocytes found in the body

• out of 1 trillion lymphocytes in the body, only 5% are found in circulation

• most lymphocytes are in lymphatic tissue where they are most likely to encounter invaders

what are the three subtypes of lymphocytes

• B lymphocytes

• T lymphocytes

• Natural Killer cells

what do B lymphocytes do

B lymphocytes and their derivative are responsible for antibody production and antigen presentation

what do T lymphocytes do

T lymphocytes play an important role in defense against intracellular pathogens such as viruses

what do Natural Killer cells do

NK cells patrol the tissues, capable of killing cancer cells as well as cells infected with viruses

how are dendritic cells classified

they are classified as antigen-presenting cells (APCs)

what can an APC do when it has bits of antigens on its surface

an APC can bind to and activate other types of immune cells

what are the steps of stopping blood loss

1. pressure in the vessel must be decreased long enough to create a secure mechanical seal in the form of a blood clot

2. once the clot is in place and blood loss has been stopped, the body’s repair mechanisms must take over

3. as the wound heals, enzymes gradually dissolve the clot while scavenger leukocytes ingest and destroy the debris

what creates platelets

they are cell fragments produced in the red bone marrow from large cells called megakaryocytes

how do platelets compare to erythrocytes

they are smaller than erythrocytes, colorless, and have no nucleus