Blood

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Blood

Main function of blood - carry oxygen and nutrients to tissues

- remove co2 and waste products

-Transports of hormones

- contributes to homeostasis

Composed of red cells, white cells and platelets in plasma

Red cell (Erythrocytes)

White cells ( Leukocytes)

Cell fragments (Platelets)

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Erythrocytes and Leukocytes

Erythrocytes - anuclear,biconcave,flexible discs, transport oxygen, lose nucleus, life span of 120 days - sourced from stem cells in bones

Leukocytes - granulocytes (65%) - motilie nucleated cells

Lysosomes - Neutrophils (95%), Eosinphils (4%)

Lymphocytes (30%)

Monocytes (5%)

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Defense mechanism

products of cell destruction release chemotactic substances

Chemotactic substances attract Granulocytes and Monocytes

Leukocytes reach foreign agents and Phagocytosis occurs

Foreign agents destroyed by enzymes

from oxygen derived free radicals

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Lymphocytes and Platelets

Lymphocytes - B lymphocytes - confer humoral immunity

when stimulated by an antigen, they are transformed into plasma cells

these cells synthesize and secrete Antibodies

T Lymphocytes -confer cell inediated immunity

main T lymphocytes are cytotonic

Platelets - small, anuclear cell, fragments of megakaryocytes, resides in bone marrow, break up into platelets at maturation

platelets enter circulation

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Aneamia

reduction of Heamoglobin

majority are women affected

acquired disease or inherited enzymatic function

genetic disease

Acquired - Dietary deficiencies, bone marrow deficiencies, excessive loss of blood

Inherited - abnormal heamoglobin, defects in heame synthesis, abnormalities in cell membrane

Heamorrhagic Anaemias - excessive blood loss

Dyshaemopoetic anemia - defective production of erythrocytes

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Blood Groups

 O, A, B, AB

Antibodies - O has antibodies to A + B

A has antibodies to B

B has antibodies to A

AB has antibodies to ABO

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Blood tranfusions and Agglutination

Cross matching necessary, Group O are universal donors

Group AB are universal recipients

Agglutination - Antigen system on the erythrocytes is activated so red blood cells Agglutinate - block circulation - break up to release haemoglobin

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Rhesus Factor

In addition to ABO there are also Rh- groups and Rh+ groups

Antigens are C, D and E

type D (+) most common

Rh- does not have D

if Rh- patient has Rh+ blood, immune system will attack itself!!

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Haemostasis

Vasoconstriction - Physical Injury of blood vessel

Contractile response by nerves - vessel narrows

Platelet Aggregation - damage to endothelium of vessel

platelet adherence at injury site

Platelets release ADP and thromboxane A2 - produce adherence of more platelets

small vessel become blocked by platelet mass

Prostacyclin released from normal endothethial cells at uninjured part of vessel

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