Unit 9: Blood

Blood

Blood

transports everything that must be carried from one place to another through blood vessels such as nutrients, wastes, hormones, and body heat

Components of blood

only fluid tissue, a type of connective tissue, in the human body and made up of formed elements (living cells) and plasma (nonliving fluid matrix); when separated, plasma rises to top (55%), erythrocytes also called hematocrit sink to bottom (45%), with thin buffy coat in between two layers

Buffy coat

contains leukocytes or white blood cells and platelets and makes up less than 1% of blood

Blood characteristics

sticky, opaque fluid thats heavier and thicker than water; color range (oxygen-rich is scarlet red, oxygen-poor is dull red or purple); metallic, salty taste; blood pH is slightly alkaline (between 7.35-7.45); temp slightly higher than body temp (38 degrees C or 100.4 F)

Blood volume

about 5-6 liters or about 6 quarts in healthy adult; makes up 8% of body weight

Plasma

90% water, straw colored fluid, and includes many dissolved substances such as nutrients, salts (electrolytes), respiratory gases, hormones, plasma proteins, and waste products

Plasma proteins

most abundant solutes in plasma and most made by liver; include Albumin, clotting proteins, and antibiotics

Albumin

important blood buffer and contributes to osmotic pressure

Clotting proteins

help to stem blood loss when a blood vessel is injured

Antibodies

help protect body from pathogens

Blood composition

varies as cells exchange substances with the blood; liver makes more proteins when levels drop; respiratory and urinary systems restore blood pH to normal when blood becomes too acidic (acidosis) or alkaline (alkalosis); plasma helps distribute body heat

Formed elements

include erythrocytes, leukocytes, and platelets

Erythrocytes

(red blood cells) main function is to carry oxygen, differ from other blood cells by being anucleate, containing few organelles (lack mitochondria), making ATP by anaerobic means, “bags” of hemoglobin, and shaped like biconcave discs; 5 million RBCs per cubic mm of blood

Hemoglobin

iron-bearing protein that bind oxygen; each bind 4 oxygen, each erythrocyte has 250 million hemoglobin, 12-18g per 100ml of blood

Anemia

decrease in oxygen carrying ability of blood due to lower than normal number of RBCs and abnormal or deficient hemoglobin content in RBCs

Sickle cell anemia

results from abnormally shaped hemoglobin

Polycythemia

disorder resulting from excessive or abnormal increase of RBCs due to bone marrow cancer (polycythemia vera) and life at higher altitudes (secondary polycythemia); increased slows blood flow and increases viscosity

Leukocytes

(white blood cells) crucial in body’s defense against disease; complete cell with nucleus and organelles; able to move into and out of blood vessels (diapedesis), respond to chemicals released by damaged tissues (chemotaxis), moved by amoeboid motion by forming cytoplasmic extensions to help them move

Granulocytes

type of leukocyte; granulates in their cytoplasm can be stained, possess lobed nuclei; includes neutrophils, eosinophils, and basophils

Agranulocytes

type of leukocyte that lacks visible cytoplasmic granules; nuclei are spherical, oval, or kidney shaped; include lymphocytes and monocytes

Neutrophils

granulocyte and most numerous WBC with a multilobed nucleus, cytoplasm that stains pink, and contains fine granules; function as phagocytes at active sites of infection; numbers increase during infection; 3000-7000 per mm3

Lymphocytes

Agranulocytes; large, dark purple nucleus, slightly larger than RBCs, reside in lymphatic tissues, play role in immune response; 1500-3000 per mm3

Monocytes

Agranulocytes and largest of WBCs; distinctive U or kidney shaped dark purple nucleus, function as macrophages when migrate into tissues; important in fighting chronic infection; 100-700 per mm3

Eosinophils

Granulocytes; nucleus stains blue-red, brick red cytoplasmic granules; function to kill parasitic worms and play role in allergy attacks; 100-400 per mm3

Basophils

Granulocytes and rarest of WBCs; large histamine-containing granules that stain dark blue to purple; contain heparin (anticoagulant); 20-50 per mm3

Leukocytosis

Leukopenia

abnormally low WBC count, commonly caused by certain drugs such as corticosteroids and anticancer agents

Leukemia

bone marrow becomes cancerous, numerous immature WBCs are produced

Platelets

fragments of megakaryocytes (multinucleate cells), needed for clotting process; normal count is 300,000 per mm3 of blood

Antigens

blood contains genetically determined proteins; substances body recognizes as foreign and the immune system may attack; most are foreign proteins and we tolerate our own

Antibodies

“recognizers” that bind foreign antigens; blood is typed using these that will cause blood with certain proteins to clump (agglutination) and lyse; over 30 common RBC

Transfusion reactions

lysed RBCs release hemoglobin into blood stream; freed hemoglobin may block kidney tubules causing kidney failure and death; fever, chills, nausea, and vomiting can result; most vigorous caused by ABO and Rh antigens

ABO blood groups

blood types based on presence or absence of two antigens (found on RBC surface); presence of both antigens A and B is type AB; presence of antigen A is type A; presence of antigen B is Type B; lack of both is type O

Rh blood group

named for 1/8 Rh antigens (agglutination D) identified in Rhesus monkeys; most Americans positive (carry antigen); anti-Rh antibodies are not automatically formed in blood of Rh negative individuals (unlike antibodies of ABO system)

What happens when Rh- person receives Rh+ blood?

immune system becomes sensitized and begins producing antibodies; hemolysis doesn’t occur because it takes time to produce antibodies; 2nd and subsequent transfusions involve antibodies attacking donor’s Rh+ RBCs and hemolysis occurs (RBC rupture)

Rh related problem during pregnancy

danger occurs during when mother is Rh- and father Rh+ and child inherits Rh+ factor; RhOGAM shot can prevent buildup of anti-Rh+ antibodies in mother’s blood; mismatch of Rh- mother carrying Rh+ baby can cause problems for child; 1st pregnancy no problems but immune system sensitized; 2nd pregnancy, mother’s immune system produces antibodies to attack Rh+ blood (hemolytic disease in newborn)

Blood typing

blood samples mixed with anti A and anti B serum; agglutination or lack of agglutination leads to identification; typing for ABO and Rh factors is done in same manner; cross-matching

Cross-matching

testing for agglutination of donor RBCs by recipient’s serum and vice versa

Hematopoeisis

process of blood cell formation that occurs in red bone marrow (myeloid tissue); all blood cells derived from a common stem cell (hemocytoblast); form two types of descendants (lymphoid stem cell and myeloid stem cell)

Lymphoid stem cell

produces lymphocytes

Myeloid stem cell

produces all other formed elements

Formation of RBCs

since RBCs are anucleate, they are unable to divide, grow, or synthesize proteins; RBCs wear out in 100–120 days; after worn out, eliminated by phagocytes in spleen and liver; lost cells replaced by division of hemocytoblasts in red bone marrow; homeostasis maintained by negative feedback from blood oxygen levels

Reticulocytes

young RBCs which enter blood to become oxygen-transporting erythrocytes

Erythropoietin

hormone that controls rate of RBC production; mostly produced by kidneys as a response to reduced oxygen levels in blood

Formation of WBCs and platelets

controlled by hormones; colony stimulating factors (CSFs) and interleukins prompt bone marrow to generate leukocytes; thrombopoictin stimulates production of platelets from megakaryocytes

Hemostasis

process of stopping bleeding that results from break in a blood vessel; 3 phases: vascular spasms, platelet plug formation, and coagulation

Vascular spasms

immediate response to blood vessel injury; vasoconstriction causes blood vessels to spasm which narrow blood vessel, decreasing blood loss

Platelet plug formation

collagen fibers are exposed by break in blood vessel, platelets become sticky and cling to fibers; anchored platelets release chemicals to attract more platelets; platelets pick up to form platelet plug

Coagulation

injured tissues release tissue factor (TF); then PF3 (phospholipid) interacts with TF, blood protein clotting factors and calcium ions to trigger a clotting cascade; prothrombin activator converts prothrombin to thrombin (enzyme); thrombin joins fibrinogen proteins into hairlike molecules of insoluble fibrin which forms a mesh work (basis for a clot); within hour, serum squeezed from clot as it restricts to pull edges of blood vessel together; serum is plasma minus clotting proteins

Thrombus

a clot that develops and persists in an unbroken blood vessel; can be deadly in areas such as lungs

Embolus

thrombus that breaks away and floats freely in the bloodstream; can later clog vessels in critical areas such as the brain

Thrombocytopenia

insufficient number of circulating platelets; arises from any condition that suppresses bone marrow; even normal movements can cause bleeding from small blood vessels that require platelets for clotting; evidence by petechiae (small purplish blotches on skin)

Hemophilia

hereditary bleeding disorder; normal clotting factors missing; minor tissue damage can cause life-threatening prolonged bleeding

Sites of blood cell formation

fetal liver and spleen are early sites of blood cell formation; bone marrow takes over hematopoiesis by the seventh month

Developmental aspects of blood

Congenital blood defects include various types of hemolytic anemias and hemophilia; incompatibility between maternal and fetal blood can result in fetal cyanosis, resulting from destruction of fetal blood cells; fetal hemoglobin differs from hemoglobin produced after birth; physiologic jaundice occurs in infants when the liver cannot rid the body of hemoglobin breakdown products fast enough; leukemias are most common in very young and old; older adults at risk for anemia and clotting disorders