Circulating Blood Flashcards
plasma vs. serum
plasma clots, serum does not clot
serum lacks the protein fibrinogen and some clotting factors
RBC energy
Very few or no mitochondria , resulting in anaerobic glycolysis and pentose phosphate pathways being important for energy production.
Granulocytes/polymorphonuclear
a. have specific granules in the cytoplasm
b. non-mitotic cells in the blood stream and after leaving the vascular system
c. three types:
i. neutrophils
ii. eosinophils
iii. basophils
Agranulocytes/mononuclear
a. lack specific granules in the cytoplasm
b. differ from granulocytes in that they can reproduce by mitosis after leaving the
vascular system
c. two types:
i. lymphocytes
ii. monocytes
Neutrophils (Polymorphonuclear neutrophils, polys, PMNs, polymorphs)
Characterized by having a many lobed nucleus and specific granules in the cytoplasm
Comprise 50-70% of differential count
young or immature cells are non-segmented
(band or stab); may comprise 1% of cells
very little RER, Golgi, free ribosomes, and few mitochondria
contains NADPH oxidase bound to the extracellular surface
(1) faces lumen of phagosome after phagocytosis of bacteri
(2) catalyzes formation of reactive oxygen compounds (superoxide; hydrogen peroxide; hypochlorous acid) within the phagosomes of neutrophils
Functions
1. Neutrophils serve as a first line of cellular defense against invasion of microorganisms. PMNs are chemotactically attracted by devitalized tissue, bacteria, and other foreign bodies and factors produced by antigen-antibody interactions with certain blood proteins (complement) and they migrate to the site of infection
2. Killing of bacteria is thus accomplished via two different mechanisms:
a. enzymatic (via fusion of specific and azurophilic granule contents with the
phagosome) which involves:
(1) phagocytosis of the foreign material, thus forming a phagosome,
(2) the specific granules fusing with the phagosome, inactivating the material,
(3) the azurophilic granules fusing with the phagosome, digesting the material,
and
(4) finally the digested material expelled from the cell.
b. via formation of reactive oxygen compounds within the phagosome
3. Neutrophils die and become the pus of an abscess.
- Not all bacteria destroyed by neutrophils. For example, the tubercle bacillus survives phagocytosis by the PMN, and must be contained by the macrophage which is derived from the monocyte
Eosinophil
- Characterized by its large eosinophilic granules in the cytoplasm
- Comprise 1-4% of the differential count
a. generally consists of two lobes held together
by a strand of chromatin
b. more than two lobes is not common
c. specific granules
i. specific granules very large (0.5 to 1.5 um wide)
ii. granules eosinophilic due to the large amount of arginine in the protein
iii. crystalline structure in granule core seen with TEM (contains major basic
protein, eosinophilic cationic protein, and eosinophil-derived neurotoxin):
major basic protein and eosinophilic cationic protein are very effective agents in combating parasites
d. azurophilic granules
i. these are lysosomes and contain hydrolytic enzymes and peroxidase
ii. contents help in the destruction of parasitic worms and in the hydrolysis of
antigen-antibody complexes internalized by the eosinophils
Functions 1. Eosinophils leave the vascular system by diapedesis, and locate especially in the connective tissue beneath the epithelium of the respiratory and gastro-intestinal tract. a. binding of histamine, leukotrienes, and eosinophil chemotactic factor (released by mast cells, basophils, and neutrophils) to eosinophil plasma membrane receptors results in the migration of the eosinophils to the site of the allergic reaction, inflammatory reaction, or parasitic worm invasion
- The differential count of eosinophils increases with parasitic infections (trichinosis,
schistosomiasis, ascaris)
a. major basic protein and eosinophil cationic protein bore holes in the pellicles of
parasitic worms, facilitating access of reactive oxygen compounds (e.g.
superoxides; hydrogen peroxide) to the parasite - Differential count increases in allergic conditions such as hay fever and asthma.
- Cells play a role in the phagocytosis and hydrolysis of antigen-antibody complexes.
- Eosinophils degrade chemical mediators such as leukotrienes and histamine released by mast cells and basophils, thus regulating local inflammatory responses
Basophil
Comprise about 0.5% of differential count
Nucleus
a. irregular shape
b. does not appear to be lobated
Functions
1. Increase in number along with other leukocytes with leukemia.
2. Increase in number in smallpox, chicken pox, and sinus inflammations.
3. Functions are appear to be involved in mediating allergic and inflammatory reactions (functions are similar to mast cells)
a. antigens can bind to IgE molecules whose Fc portion is bound to Fc receptors on
the basophil surface; this may cause the basophils to release the specific granule
contents into the extracellular spaces
(1) release of histamine causes smooth muscle contraction (in the bronchial tree), vasodilation of microcirculation, and leaking of blood vessels
b. begin to produce and release leukotrienes
(1) similar effects to histamine, but actions are slower and more persistent
Lymphocytes
- Produced in lymphatic nodules, lymph nodes, spleen, thymus, tonsils, and bone
marrow, and endow the body with its immunological defense. - Comprise 20-40% of differential count
Nucleus
a. spherical or slightly indented on one side
b. chromatin is densely packed with a hill and valley pattern
c. nucleolus present but not seen because of clumped chromatin
3. Cytoplasm
a. frequently appears as a thin rim
b. many free ribosomes and polysomes, some azurophilic granules, Golgi, RER, and mitochondria
B-lymphocytes
a. compose about 15% of circulating lymphocytes
b. called B-cells because in chick develop in bursa of Fabricius
c. in humans develop in bursa equivalent (gut) or bone marrow
d. cells may leave the circulation and enter lymphatic tissue where by the process of mitosis they give rise to clones of B-cells
e. function or fate of B-lymphocytes:
(1) Plasma cells - produce antigen-specific circulating immunoglobins (humoral
antibody response)
(2) Memory cells - found in lymphatic tissue and stimulated by re-exposure to antigen; reaction termed the secondary response
T-lymphocytes
a. compose 80-90% of circulating lymphocytes
b. originate embryological from the yolk sac and seed the thymus by way of the
liver and bone marrow
c. multiply and differentiate into T-lymphocytes in the thymus - each developing
lymphocyte develops an individual antigenic specificity.
d. activation of T-cells (needed for activation)
(1) appropriate antigen
(2) macrophages must process the antigen for presentation
e. subsets of T-lymphocytes
(1) Cytotoxic T cells
(2) T helper cells
(3) T suppressor cells
f. function (s) of T-lymphocytes
(1) cell mediated immunity; assist in humoral immunity
Null cells
a. neither B- nor T-lymphocytes
b. example: NK (natural killer) cells
Monocyte
- Characterized partly by its large size
- Comprise 2-8% of the differential count
- 300/mm3
- Cells originate in the bone marrow
Functions - Monocytes exhibit diapedesis (continually extend and withdraw pseudopodia) and
reach full development outside the blood stream where they are known as
macrophages. Macrophages fuse to form foreign body giant cells and osteoclasts; In the CNS the macrophages form microglia; in the liver, Kupffer cells; and in the lungs, alveolar macrophages. - Serve as the second line of defense against invading organisms. Found in areas of
chronic inflammation. - After leaving the vascular system, the macrophage (monocyte) plays a role along with the T-lymphocyte in the differentiation of the B-lymphocyte into the plasma cell, which produces immunoglobulins.
- Some macrophages are particularly good at processing and presenting antigen and are called antigen presenting cells
- Monocytosis - increased monocyte count due to infectious and inflammatory diseases, tuberculosis, and leukemia.
