Week 6: Blood

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Blood (specialised liquid connective tissue)

transports oxygen, carbon dioxide, nutrients and waste products (nutrients, end products, hormones)

regulates pH

controls body temp by diverting blood to or away form skin's surface

protects body against blood loss through clotting, infection through antibodies

- consists of

Plasma

90% water

7-8% proteins

albumin: most abundant, maintain osmotic pressure; exchange of fluids over capillaries for nutrients

globulin: contain immunoglobulins (antibodies, iron carrying globulins

fibrinogen: proteins that participate in blood coagulation

2% electrolytes, gases, hormones

Formed elements (cells in blood):

Erythrocytes (RBC)

generated in red blood marrow (erythropoiesis)

have biconcave disc; allows it to change shape for trans

lack nucleus and organelles; made up of selectively permeable plasma membrane, cytosol, hemoglobin

hemoglobin: oxygen, iron carrying protein

phagocytosed by macrophage in spleen, liver and red bone marrow for removal of worn-out blood cells

ANEMIA - deficiency of number and quality of RBC or amount of hemoglobin (e.g. iron deficiency, pernicious anemia due to insufficient vitamin B12, aplastic, sickle cell anemia)

blood groups

genetically assorted groups determined by the presence of antigens of the surface of RBC:

ABO

O- antibody A and antibody B, no antigens

AB- no antibodies, A and B antigens

B -antibody A, B antigen

A- antibody B, A antigen

Rh+/-

Rhesis negative antigen - no antigens

Rhesis positive antigen - antigens present

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Leukocytes (WBC)

Agranular (mononuclear): T and B lymphocytes, natural killer cells, monocytes (rounded or dented nuclei)

monoytes:

largest WBC 8% of leukocytes

indented, horse-shoe shape

contain large portion of cytoplasm

move from bloodstreams to connective tissues

transform into macrophage after moving from , amoeboid motion helps them through connective tissue to digest

monocyte becomes and differentiates into macrophage (extensions for mobility) to phagocytose foreign particles

arrive in large numbers to bacterial site, takes longer and more microbes to attend site

lymphocyte:

comprise 25% of leukocytes

most important in immune system

generally spherical or dented

nucleus takes up majority of space in cell itself

do not function within blood stream but exit through through capillary walls to go to connective tissues to carry function

located in specialised connective tissues called lymphoid/lymph connective tissues

fight infectious organisms, recognise and act against a specific foreign molecule/antigen (code for specific molecule)

any molecule that will induce lymphocyte action: antigen

types of lymphocytes:

T-cells: attack foreign substances directly (fungi, cancer cells)

B-cells: differentiate into plasma cells to produce antibodies which bind to antigen to mark the foreign substance for its destruction by macrophage or enacting toxins

natural killer cells: attack a wide variety of substances

Granular (polymorphonuclear): neutrophils, basophils, eosonophils (multi nuclei), (visible through microscope)

neutrophils:

most common WBC 70% of leukocytes

multilobed, 3-4 in one

responds first to bacterial invasion, injury, inflammation to phagocytose bacteria

granules seen in neutrophils are membrane walled sacs of digestive enzymes

if inflammation is prolonged or severe the neutrophil secretions will cause damage to tissues in the area which forms pus -> dead neutrophils fighting infection

eosinophils

rare 2-4%

bi-lobed nucleus, connected by a "band"

end allergic reactions, phagocytose the allergen once they bind to the antibodies, secrete enzyme that will degrade hystamine and other chemicals in inflammation

respond to parasitic infection, adhere to parasites to release enzymes to digest and destroy parasite

found in gastrointestinal intestine and skin (where parasites are likely found)

basophils

rarest >1%

nucleus bi-lobed, in U or S shape

granules cover the nucleus

leave the blood to enter tissues to partake in inflammatory response and help fight allergic reactions

granules secrete hystamine to mediate inflammation during allergic reaction or parasitic infection

similar to mast cells - secrete histamine, similar to eosinophils

main difference between basophils and eosinophils: dense mass of granules cover nucleus, eosinophils more abundant

function: defense cells

have nucleus and organelles but no hemoglobin

not confined to blood, but can leave blood stream capillary wall to enter loose connective tissues to an infection site, where chemicals are produced to then attract WBC (amaboeboid motion)

white blood cells develop cytoplasmic extensions to become motile to get to site of infection (amoeboid motion)

originate in bone marrow, stores WBC and releases in large quantities in case of serious infection

thrombocytes (platelets)

fragments of cells (megakaryocytes from bone marrow)

no nuclei, small, contain mitochondria, ribosomes and enzyme systems plus 4 granules

platelets help stop blood loss by forming clots through vesicles in granule cells

may promote unwanted coagulation

hematopoiesis: formation of blood cells:

- erythropoiesis, leukopoiesis, megakaryocytopoiesis

- hematopoietic tissues:

myeloid tissue (red bone marrow): erythrocytes, granular leukocytes, thrombocytes;

lymphoid tissue (lymph nodes, spleen, thymus): agranular leukocytes

during embryonic and foetal development: yolk sack, liver, spleen

- pluripotent stem cells give rise to all cell types, under control of cytokines/growth factors

components:

- Red blood cells (hermatocrit) (45%)

- Blood plasma (55%)

- Buffy coat: white blood cells and platelets

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