Blood Cells

∞ generated and posted on 2020.03.15 ∞

Blood consists of formed elements, in addition to plasma, as well as multimolecular complexes.

The formed elements of blood include red blood cells (a.k.a., erythrocytes), white blood cells (a.k.a., leukocytes), and platelets (a.k.a., thrombocytes) as well as multimolecular complexes such as HDLs (high-density lipoproteins) and LDLs (low-density lipoproteins).

This page contains the following terms: Formed elements, Red blood cells, Erythrocytes, Hemoglobin, White blood cells, Platelets, Platelet plug, Blood clot, High-density lipoprotein (HDL), Low-density lipoprotein (LDL), Elevated triglyceride levels, ABO blood group system, Rh blood group system Erythroblastosis fetalis, Anemia, Carbon monoxide poisoning, Leukemia, Mononucleosis, Jaundice, Shock

Formed elements

Cells along with cell-like structures found in blood.

Formed elements include the familiar red blood cells (RBCs, a.k.a., erythrocytes), the perhaps less familiar white blood cells (which are involved primarily in immune system functioning and are also known as leukocytes), and also platelets, which are involved in blood clotting.

The platelets, though formed from cells, are technically not cells, and neither are red blood cells, which lack cell nuclei.

Whole blood minus formed elements is plasma and plasma minus fibrinogen more or less is serum.

Links to terms of possible interest: Basophils, Blood, Eosinophils, Formed elements, Lymphocytes, Monocytes, Neutrophils, Platelets, Red blood cells, White blood cells

The above video introduces the formed elements as well as other materials that are found dissolved in blood.

Red blood cells

Oxygen-carrying formed elements that circulate in some abundance within blood.

In mammals, individual red blood cells lack a cell nucleus and thus technically are not cells but rather they are derivatives of cells. Instead, red blood cells – which are otherwise known simply as RBCs or erythrocytes – are mostly "bags" of the protein hemoglobin (where the "bag" itself is the RBC plasma membrane).

Red blood cells are produced within bone marrow, which is the source of formed elements generally.

Interestingly, a lack of nuclei in red blood cells is not inevitable as birds possess red blood cells that retain their nucleus. In addition, animals that possess an open rather than closed circulatory system, their blood equivalent, called hemolymph, lacks even red blood cells, since red blood cells can only circulate within a continuous tube, and only closed circulatory systems consist of continuous tubes.

Blood types, such as the ABO blood types, are based upon what are known as antigens that are associated with the membranes of red blood cells.

Links to terms of possible interest: Basophils, Eosinophils, Erythrocytes, Formed elements, Lymphocytes, Monocytes, Neutrophils, Platelets, Red blood cells, White blood cells

The above video provides an introduction to red blood cells.

The above video mostly gets its biology right, except that only a single molecule of oxygen binds per heme/iron ion, and at most a total of four bind per hemoglobin molecule.

Erythrocytes	Alternative name for red blood cells.
	Meaning "red" "tube" "cells". ☺

The above video is more than a bit redundant, involving the computer-generated passage of red blood cells down a vessel, but it's cool to watch if only for short spans and particularly at 2× speed.

Hemoglobin

Protein found in red blood cells that binds to and then carries oxygen.

The color of red blood cells as well as blood itself is a consequence of hemoglobin, particularly hemoglobin as bound to oxygen. The color comes from the iron ion that is found in association with the hemoglobin protein. In fact, the binding of oxygen is actually to the iron ion that is associated with the hemoglobin protein. The iron ion, further, is actually bound to a compound known as heme which is what the protein portion of hemoglobin is actually bound to.

Thus, oxygen (O₂) is bound to iron (Fe²⁺ without oxygen or Fe³⁺ with) which is bound to heme (which is one of a category of organic compounds known as porphyrins) which in turn is bound to the hemoglobin polypeptides. A total of four polypeptides together make up hemoglobin so there are four hemes and therefore four iron ions per hemoglobin and thus a total of four oxygen molecules (and eight oxygen atoms) that bind to each hemoglobin protein.

The related molecule, myoglobin, serves as the oxygen storage molecule within muscle.

Links to terms of possible interest: Hemoglobin, Oxygen, Pulmonary alveoli, Red blood cell

The above video provides a nice overview of the functioning of hemoglobin.

The above video discusses the structure and properties of hemoglobin.

White blood cells

Formed elements involved in an animal's immune response.

White blood cells, also known as leukocytes, include what are known as both granulocytes and agranulocytes, where granulocytes contain granules within their cytoplasms that represent secretory vesicles, that is, stuff that is awaiting secretion upon immune stimulation. White blood cells also can be phagocytes (or not) or lymphocytes (or not).

The neutrophils and monocytes either are or give rise to phagocytic cells, that is, cells that are capable of engulfing small chunks of foreign material. The latter, monocytes, form into the phagocytic cells called macrophages.

Also among white blood cells are the non-phagocytic, non-lymphocyte eosinophils and basophils. Included among the lymphocytes are B cells, T cells, and natural killer cells. Needless to say, immunology, for which the white blood cells are only a component, is kind of complex.

Links to terms of possible interest: B lymphocyte, Basophil, Common lymphoid progenitor, Common myeloid progenitor, Eosinophil, Erythrocyte, Hemocytoblast, Hematopoietic stem cell, Leukocytes, Macrophage, Mast cell, Megakaryocyte, Monocyte, Multipotent, Myoblast, Natural killer cell, Neutrophil, Plasma cells, Stem cell, T lymphocyte, Thrombocyte, White blood cells

The above video is a little slow paced but is fairly comprehensive and has nice graphics; note, though, that as with anything immunological, the overview can be a bit overwhelming.

Platelets

Formed elements involved in blood clotting.

Platelets are also known as thrombocytes and like red blood cells they lack cell nuclei. In addition, platelets also are fragments of the cells that form them, that is, in the course of development those cells go through multiple rounds of what essentially is cytokinesis such that the cytoplasm is divided into multiple, membrane enclosed "sub cells". The platelet progenitor cells are known as megakaryocytes and the resulting fragments are present within blood at extremely high numbers, measuring in the millions per ml.

The role of platelets is to help effect what is technically known as hemostasis, which results in blood clotting, specifically in the formation of thrombi or platelet plugs. Platelets also are responsible for the release of what are known as growth factors, which play roles in the maintenance and repair of tissues.

Links to terms of possible interest: Activated platelet, Bone marrow, Hematopoietic stem cell, Megakaryocyte, Platelet, Promegakaryocyte

The above video provides a nice introduction to platelets and their function.

The above video is a fairly comprehensive overview of platelets especially as viewed from the perspective of how medically one can address a problem of low platelet counts; there is no video component to the "video", however.

Platelet plug	Sticky aggregations of formed elements that serve to seal small holes that can form as injuries to blood vessels.
	While platelet plugs are sufficient to plug up small holes in blood vessels, the blocking of larger holes requires a greater elaboration of phenomena which collectively give rise to a blood clot. Particularly, platelet plugs are primarily platelet driven whereas blood clots are formed particularly via the conversion of precursor protein fibrinogen to fibrin.

Links to terms of possible interest: Coagulation reaction, Platelet, Platelet plug, Thrombin

The above video provides a very quick though not very detailed illustration of platelet plug formation in response to endothelial injury.

The above video is overwhelming in its level of detail but nonetheless provides a good if highly detailed introduction to the process of platelet plug formation.

Blood clot

Aggregations of the protein fibrin to seal larger holes that can form in blood vessels due to injury.

The conversion of the protein fibrinogen to fibrin is tightly regulated since blood clot formation within healthy vessels can be disastrous to normal body functioning (since blood clots serve to block blood movement, hence use of the term hemostasis to describe blood clotting).

The actual process of blood clotting is quite complex, involving multiple molecules know as clotting factors, but basically it involves the regulated conversion of fibrinogen to fibrin, which then serves as a trap for whatever cells are present within the vicinity of the forming clot.

The trapped platelets with time contract (that is, become smaller), which serves to further seal the wound by drawing the edges of the breach more closely together.

The purpose of the clot, of course, is to stem excessive blood loss, though also to limit the ability of pathogens to gain access to the bloodstream following injury. Blood clots additionally can be viewed as the first step towards the healing of such a wound.

The overall process of blood clotting is termed coagulation, and also thrombogenesis, and a blood clot is also known as a thrombus.

Links to terms of possible interest: Blood clot, Coagulation, Platelet, Platelet plug, Smooth muscle, Vasoconstriction

The above video presents hemostasis in some detail

High-density lipoprotein (HDL)

Complexes found in blood that carry cholesterol to the liver.

Lipoproteins, here, are complexes of globulin blood proteins and the lipid molecules that they both associate with as well as transport within the blood. These lipoproteins come in a variety of types with a variety of functions and the high-density lipoproteins, or HDLs, are a type that is often described as the "good" cholesterol, which is shorthand for cholesterol circulating in the blood that is associated with greater cardiovascular health.

The latter, greater cardiovascular health, is particularly so since HDLs carry cholesterol away from circumstances where they are deposited on arterial walls rather than towards such circumstances. Contrast particularly with low-density lipoproteins though note that there are additional types of blood-associated lipoproteins other than HDLs vs. LDLs.

Low-density lipoprotein (LDL)

Complexes found in blood that carry cholesterol away from the liver.

Low-density lipoproteins, or LDLs, are often described as the "bad" cholesterol because rather than carrying cholesterol towards the liver, instead LDLs carry cholesterol away from the liver, which can then be deposited on arterial walls. Keep in mind that though LDLs are described as "bad", they nonetheless are necessary for body functioning. It is just that excess body production and circulation of LDLs is thought to result in poor health outcomes.

Elevated triglyceride levels

(alt link)

Blood condition associated with predisposition to cardiovascular disease even independent of cholesterol levels.

Also known as hypertriglyceridemia, elevated levels of triglycerides in blood is simply that: excess levels of fats carried with the blood (where a fat is a triglyceride, that is, a combination of the molecule or moiety glycerol and three fatty acid molecules or moieties, a.k.a., triacylglycerols). Specifically, tendencies towards atherosclerosis, or hardening of the arteries, has been found to be associated with elevated triglyceride levels in the blood.

ABO blood group system

Means by which the blood of different individuals can be distinguished in terms of its interaction with immune systems, as employed towards matching blood donors with recipients.

The ABO blood system, at a minimum, consists of two molecules that can be found on the surface of red blood cells, termed A versus B. An individual carries a gene for the A molecule (or A antigen as it is described), the B antigen, both A antigens and B antigens, or neither A nor B.

If a person does not display the A antigen then they can produce antibodies to that antigen (A). Similarly, if a person does not display the B antigen then they can produce antibodies to that antigen (B).

The result is that a person who does not carry the A antigen and therefore carries anti-A antibodies, cannot receive blood from a person who does carry the A antigen and similarly a person who carries the B antigen, and therefore carries anti-B antibodies, cannot receive blood from a person who carries the B antigen.

People with type O blood lack both antigens so can receive blood only from type O individuals (since they produce antibodies against both the A antigens and B antigens) but can donate blood to all individuals (since they lack both the A antigens and B antigens).

People with AB blood type possess both A antigens and B antigens and therefore lack antibodies against both antigens so can receive blood from all individuals but can donate blood only to other AB individuals.

Links to terms of possible interest: ABO blood group, Antibody, Antigen, Blood transfusion, Plasma, Red blood cell, Type A blood, Type AB blood, Type B blood, Type O blood, Universal donor, Universal recipient

The above video provides a basic discussion of what blood types are all about, their underlying alleles, and the genetics of ABO blood types.

The above video provides a nice discussion of the biochemistry underlying ABO blood types.

Rh blood group system

Means by which the blood of different individuals can be distinguished in terms of its interaction with immune systems, as important particularly in terms of blood transfusion as well as carriage of fetuses by mothers who are lacking in the associated antigen.

Though there are numerous blood antigens as associated with red blood cells that fall into the category of Rh positive, it is the lack or relative lack of such antigens that defines an Rh negative individual.

The problems associated with these Rh types occur when Rh-negative individuals are exposed to Rh-positive blood. This exposure can occur either in the course of transfusion with improperly matched blood or instead, and crucially, given the carriage and subsequent birthing of an Rh-positive fetus by an Rh-negative mother.

In both cases, exposure of the Rh-negative individual to Rh-positive blood can result in the development of antibodies that target the Rh-positive antigen. This can result in disruption of red blood cells, severe anemia in so-affected fetuses, and thereby a disease known as erythroblastosis fetalis. Rh, btw, stands for rhesus as in rhesus monkeys.

The above video is a quick overview of Rh factor as well as its potential impact on children during pregnancy; note though that generally the Rh factor does not cross the placenta but instead the mother is exposed over the course of giving birth.

Erythroblastosis fetalis

Disease of newborns associated with Rh blood type incompatibilities.

Erythroblastosis fetalis, also known as hemolytic disease of the newborn, is a consequence of an Rh-negative mother, an Rh-positive father, and multiple pregnancies involving an Rh-positive child. The problems arise as the mother has opportunity to produce antibodies to the Rh-positive antigen. This generally does not occur until following the birth of the first Rh-positive child.

These antibodies, so produced, however can then attack the red blood cells of Rh-positive fetuses during subsequent pregnancies, resulting in lysis and loss of red blood cells. It is possible to block the occurrence of erythroblastosis fetalis by treating the mother with anti-Rh immunoglobulin (antibodies) to prevent her from ever mounting an immune response of her own against the Rh factor.

The above video does a fairly good job of quickly walking through how it is that erythroblastosis fetalis comes to occur.

Anemia

Lower than adequate densities of normal hemoglobin in blood.

Anemia can be a consequence either of too few red blood cells or instead of insufficient quantities of hemoglobin per red blood cell. It also can result from a lack of proper functioning of hemoglobin molecules. Given the variety of ways in which anemia can be manifest, there also are numerous causes including, particularly, iron deficiency.

The result regardless is a reduction in the ability of blood to carry oxygen and therefore a relative lack of oxygen within our tissues. This in turn results in an impairment of body functions that we perceive as lethargy, along with additional symptoms. These symptoms in turn can vary with the severity of anemia which can range from mild deficiencies in blood carrying capacity of oxygen to severe deficiencies.

Links to terms of possible interest: Anemia, Angina, Enlarged spleen, Fatigue, Heart attack, Heart palpitations

Carbon monoxide poisoning

Disease characterized by chemical binding to hemoglobin that blocks oxygen binding.

Carbon monoxide or C O (contrasting carbon dioxide or C O₂) has a higher affinity for hemoglobin than does oxygen (or O₂). The result is a displacement of oxygen from hemoglobin that has the effect of lowering the blood's ability to carry oxygen. If the oxygen carrying capacity of blood is reduced sufficiently then this can result in death.

Treatment involves patient exposure to elevated levels of oxygen to displace carbon monoxide and allow carbon monoxide's removal from the body via exhaling. Carbon monoxide itself is a consequence of incomplete combustion of carbon-based fuels, e.g., as associated with a poorly vented furnace.

The above video does a good job of walking through the symptoms of carbon monoxide poisoning and also illustrates what the problem is, with carbon monoxide displacing oxygen on hemoglobin.

The above video is basically a public safety message on the dangers of carbon monoxide (here is a link to the mentioned Vitas Gerulaitis).

Leukemia

Malignancy characterized by excessive blood counts of white blood cells.

The actual malignancy, that is, the cancer, can be centered either in the blood itself or instead the white blood cell progenitor organ, the bone marrow. The disease is associated with a large number of symptoms that tend to be a result of dysfunction of one or more of the additional cell types (more broadly, formed elements) that are produced by bone marrow. Various treatments exist with also varying success rates depending on patient age as well as leukemia type.

Links to terms of possible interest: Enlarged spleen, Fatigue, Leukemia, Night sweats, Swollen lymph nodes

Mononucleosis

Virus-caused disease often associated during teen years with fatigue and other symptoms.

Mononucleosis, less formally "mono" and more formally "infectious mononucleosis", is usually caused by Epstein-Barr virus, which is a type of herpes virus. Mononucleosis is transmitted via direct contact between individuals, particularly via saliva and thus is known colloquially as the "kissing disease".

As with any viral infection, mononucleosis cannot be treated using antibiotics and indeed cannot be treated except to allow rest as needed, provide plenty of fluids, treat symptoms, and to otherwise take precautions to avoid transmission to others. In addition, infectious mononucleosis can result in temporary enlargement of the spleen which can increase the potential for spleen rupture such as given participation in contact sports.

The association with "blood" is that the cells that are targeted by the virus during later stages of infection are B cells, a kind of white blood cell.

Links to terms of possible interest: Enlarged spleen, Fatigue, Fever, Infectious mononucleosis, Mononucleosis, Photophobia, Swollen lymph nodes, Swollen tonsils

The above video provides a nice medical overview of mononucleosis.

The above video is a nicely presented and indeed fun overview of mononucleosis.

Jaundice

Yellowing of the skin and other portions of the body associated with buildup of the pigment bilirubin in the blood.

Jaundice often is a sign of insufficient liver functioning. Bilirubin is a breakdown product of heme that occurs in the course of normal red blood cell turnover (red blood cells on average normally last only approximately 120 days). A consequence of this red blood cell destruction is the breakdown of the heme associated with hemoglobin. The role of the liver is to remove the bilirubin and then excrete it within bile and it is particularly a failure of bilirubin removal from the blood that gives rise to jaundice.

Shock

Acutely poor delivery of oxygen to tissues such as due to pathologically low blood pressure.

Generally shock occurs when normal compensatory mechanisms ‐ as would normally result in homeostasis – give rise to compensatory mechanisms that instead have the effect of reducing the efficiency of blood circulation in a positive feedback manner.

More precisely, shock is referred to as circulatory shock. See also septic shock.

There are a number of causes of circulatory shock. Septic shock, for instance, is associated with systemic increases in arterial diameters (vasodilation) that has the effect of reducing blood volume as a function of blood vessel capacity, resulting in reduction in blood pressure.