Chapter 12 Blood, lymph, and nodes

Neutrophils

40% to 75% of circulating leukocytes and are the most abundant white blood cell type in the blood of dogs, cats, and horses. Neutrophils are larger than red blood cells and smaller than monocytes...spend an average of 10 hours in circulation before it enters the tissue. This circulation time is shorter when there is an increased demand for neutrophils in the tissue. Once a neutrophil enters tissue it doesn't return to the blood, so all circulating neutrophils need to be replaced about two and a half times a day.

Intravascular Hemolysis

About 10% of normal red blood cell destruction ...destruction that takes place within blood vessels. While in circulation, a red blood cell is exposed to many oxidative stresses, which can result in red blood cell fragmentation and/or destruction. When the red blood cell membrane ruptures within a vessel, hemoglobin is released directly into the bloodstream. The unconjugated hemoglobin is quickly picked up by haptoglobin, a transport protein in plasma, to form a haptoglobin-hemoglobin complex. This complex travels to the macrophages in the liver for further breakdown, similar to what happens with extravascular hemolysis.

Agranulocytes

Agranulocytes are mature white blood cells that do not contain specific staining granules in their cytoplasm. They include lymphocytes and monocytes

B lymphocytes

Each B cell is preprogrammed to produce only one specific antibody type against one 311specific antigen. On its cell surface, a B cell has thousands of receptors shaped to fit only one antigen shape.... B cells recognize an antigen, they transform into plasma cells that release antibodies. This is called humoral immunity.

normal life span of a mature red blood cell

In dogs, the average life span is 120 days. In cats it is approximately 68 days. Horse and sheep red blood cells live up to 150 days, and those of cows can live as long as 160 days. On the other end of the scale are mice, whose red blood cells live only 20 to 30 days. As red blood cells wear out, age, and die, they are replaced by young red blood cells from the red bone marrow in the never-ending erythropoiesis cycle

Eosinophils

Inflammatory response. Eosinophils are attracted to and inhibit local allergic and anaphylactic reactions. Their granules contain anti-inflammatory substances that are released at the site of an allergic reaction. • Immunity. Eosinophils can ingest substances associated with the humoral immune response (e.g., antigen-antibody complexes). • Phagocytosis. Eosinophils have minimal phagocytic and bactericidal functions. The contents of eosinophil granules are especially toxic to large pathogenic organisms, such as protozoa and some parasitic worms.

agranulocytes

Lymphopoiesis is the process that produces lymphocytes, some of which develop outside the bone marrow. Monopoiesis is the formation and maturation of monocytes

extravascular hemolysis

Ninety percent of the destruction of senescent red blood cells ...destruction of red blood cells outside the cardiovascular system. The red blood cells are removed from circulation by macrophages located primarily in the spleen. The membranes of the phagocytized cells are ruptured and hemoglobin is released and degraded into amino acids, iron, and heme. The amino acids are returned to the liver where they are used to build more proteins. The iron is transported to the bone marrow where it will be recycled during erythropoiesis to make new red blood cells. The heme will be further broken down into free or unconjugated bilirubin

Basophils

Not much is known about the function of basophils. They are the least phagocytic of the granulocytes. Their granules contain histamine and heparin. Histamine helps initiate inflammation and acute allergic reactions. Eosinophils are attracted to the site of an allergic reaction by 310eosinophilic chemotactic factor released from the basophil or mast cell granules. Heparin acts as a localized anticoagulant to keep blood flowing to an injured or damaged area.

Platelets

Platelets have specific roles in the clotting process, along with endothelial cells in the blood vessel wall and coagulation factors. The two specific functions of platelets in hemostasis are the formation of a platelet plug and stabilization of the plug, making it irreversible

lymphatic system has four primary functions

Removal of excess tissue fluid..Waste material transport..Filtration of lymph...Protein transport

lymphocytes

T, B, plasma cell and natural killer cells

Bursa of Fabricius

The bursa of Fabricius is found only in birds and is similar in structure and function to the thymus. It is a round sac that sits right above the cloaca.

senescence

The process of aging

red and white pulp in spleen

The white pulp is formed of localized areas of lymphoid tissue containing lymphocytes that can clone themselves during an immune response. The red pulp consists of blood vessels, tissue macrophages, and blood cell storage spaces called sinuses. The tissue macrophages filter out antigens and other foreign material from lymph and remove dead, dying, and abnormal red blood cells.

Lymphoid Organs and Tissues

Thymus...Bursa of Fabricius...Peyer's Patches...The secondary lymphoid

RBC function

Transporting oxygen to tissues...Transporting carbon dioxide to the lungs....Maintaining cell shape and deformability

T lymphocytes

cells are processed in the thymus before going to peripheral lymphoid tissue. T cells are responsible for cell-mediated immunity (no antibody production involved) and for activating B cells. Most of the lymphocytes in peripheral blood are T cells.

platelet life span

circulate in the blood for approximately 5 to 7 days. The liver produces thrombopoietin, which regulates the number of platelets circulating in the body. Much like erythrocytes, platelets are removed from the circulation by macrophages because of old age or damage.

Plasma cells

derived from B cells in response to an antigenic stimulus. The B cells that are activated by their unique antigen multiply by mitosis in a process called blastic transformation to become plasma cells. Plasma cells produce, store, and release antibodies that are also known as immunoglobulins. Plasma cells can be found in any tissue in the body, but are most numerous in tissues engaged in antibody formation (e.g., lymph nodes, spleen). Plasma cells are rarely found in peripheral blood

Secondary Lymphoid Organs

developed later in fetal development and persist in adult animals. They include the spleen, lymph nodes, and tonsils. Their main function is to trap and process antigens and mature lymphocytes that mediate immune responses. Unlike the primary lymphoid organs these organs will enlarge in response to antigenic stimulation

specific mature cells through their individual maturation process

erythropoiesis, leukopoiesis, or thrombopoiesis

Leukopoiesis

formation of white blood cells

Tonsils.

found in epithelial surfaces all over the body, but we are most familiar with the ones in the pharyngeal (throat) region. Here, they function to prevent the spread of infection into the respiratory and digestive systems. Tonsils are classified as secondary lymphoid tissue where mature lymphocytes live. They are most prominent in young animals as they are developing their immune systems. Tonsils differ from lymph nodes in three significant ways: (1) tonsils are found close to moist epithelial (mucosal) surfaces, (2) tonsils don't have a capsule, (3) tonsils are found at the beginning of the lymph drainage system, not along the lymph vessels like lymph nodes. Other tonsils are found in the larynx, intestine, prepuce, and vagina.

Natural killer

found in the blood and lymph...identify and kill virus-infected cells, stressed cells, and tumor cells. They differ from phagocytes in that they do not ingest the target cell. Instead, they bind to the cell and induce cellular changes that lead to apoptosis (programmed cell death) or lysis of the cell...KAR AND KIR

neutrophil function

involved in the early stages of the inflammatory response. Some neutrophils can always be found in tissues that are constantly exposed to microorganism invasion, such as the lungs and gastrointestinal tract. When microorganisms try to enter the body, the skin and mucous membranes mount the first attack. Next, neutrophils quickly respond by traveling in the blood to the site of inflamed tissue to mount a second attack. Neutrophils leave the blood vessel by squeezing between the cells of the endothelium in a process called diapedesis. They are attracted to a site of infection by chemotaxis, a process by which neutrophils and other cells are attracted by inflammatory chemicals produced by the interaction between microorganisms and the tissues they are invading. This allows the neutrophil to recognize what to ingest

Lymph Nodes. (secondary organs)

kidney bean-shaped filters located at various points along lymphatic vessels. They trap antigens and other foreign material carried in lymph. A lymph node is divided into a cortex and a medulla, which have lymphatic sinuses running through them

Peyer's Patches

located in the wall of the small intestine. They have various structures and functions depending on 314the species. However, their common function is the activation of B cells to produce antibodies against antigens in the small intestines. Peyer's patches are just one type of gut-associated lymphoid tissue (GALT) located throughout various areas of intestinal mucosa and submucosa.

Monocytes

participate in inflammatory responses. They do not spend much time in bone marrow or the circulation before they enter into tissues where they can live for up to 100 days. When monocytes enter tissues, they become macrophages. Collectively, the tissue macrophages and monocytes are known as the mononuclear phagocyte system (MPS). Both macrophages and monocytes clean up cellular debris that remains after an infection/inflammation clears up

Granulopoiesis

process by which a pluripotential stem cell differentiates into one of three types of granulocyte: neutrophils, eosinophils, or basophils. Early granulocytes are difficult to distinguish from one another because they all appear as large cells with lots of cytoplasm, large round nuclei, and a first set of nonspecific granules

Thrombopoiesis

production of platelets, begins when a specific stimulant acts on the unipotential stem cell in the red bone marrow, causing it to differentiate into a megakaryocyte. The megakaryocyte is a large multinucleated cell that never leaves the bone marrow.

Coagulation Cascade

series of reactions that result in inactive enzymes being activated by the preceding enzyme in the cascade. There are 13 different factors that have been identified as necessary for clotting to take place

spleen (secondary organ)

spleen is a tongue-shaped organ located on the left side of the abdomen. It is near the stomach in simple-stomached animals and near the rumen in ruminants. Not only does the spleen store red blood cells and produce red blood cells during fetal development, but it also filters the blood and lymph

Lymph Formation

starts out as excess tissue fluid that is picked up by small lymph capillaries found in the interstitial spaces of soft tissue. The excess tissue fluid accumulates when more fluid leaves blood capillaries than re-enters them. If it were not for the lymph vessels, the tissues of the body would all swell with the excess fluid

thymus

thymus is responsible for most of the production of mature T cells ...located in the cranial thorax

Mature red blood cells

utilize glucose from plasma for energy

packed cell volume (PCV), or hematocrit

volume of packed erythrocytes measured and expressed as a percentage of a total volume of blood

Peripheral blood

whole blood circulating in blood vessels carrying oxygen, nutrients, and waste materials