Blood

Anatomy and Physiology II

BIO 232

Composition of Blood

• 5 liters of blood - average adult (8 % of body weight)

• pH 7.35 - 7.45

• Temperature 38° C - higher than normal body temp

• Formed elements of blood

• RBCs, WBCs & platelets

• 45 % of total volume (hematocrit)

• Plasma - fluid portion

Composition of Blood

Blood Plasma

• 90% water

• Over 100 dissolved solutes

• Plasma Proteins - 8%

• Albumins - 60-80% from liver - help regulate osmotic pressure

• Globulins - a, b - liver - transport lipids & fat soluble proteins - g globulins - antibodies

• Fibrinogen - liver - 4% - clotting

Formed Elements of Blood

• Erythrocytes - Red Blood Cells - RBCs

• Small biconcave discs

• Network of proteins responsible for the shape - especially spectrin

• 7.6 mm diameter

• 2 mm thick

• Packed full of Hemoglobin

Formed Elements of Blood

• Erythrocytes

• No nucleus when mature

• 4-6 million / mm3 of whole blood

• Survive 120 days - broken down in liver & spleen

• 250 million hemoglobin molecules /RBC

Hemoglobin

• Respiratory pigment- carries oxygen

• 4 polypeptide chains

• 2a & 2 b chains

• Each associated with heme - complex iron containing group

• Plasma carries - 0.3ml of O₂ /100ml

• Whole blood carries - 20 ml O₂ /100ml

Hemoglobin

• Oxyhemoglobin - oxygen bound to the iron in hemoglobin

• New 3d shape & is bright red

• Deoxyhemoglobin (reduced hemoglobin) - when oxygen detaches

• Dark red color

• Carbaminohemoglobin - CO₂ bound to hemoglobin (20% of the CO₂ is bound to hemoglobin)

Erythropoiesis

• The production of RBCs from a hemocytoblast desendant in bone marrow of the bones of the axial skeleton & proximal epiphyses of the femur & humerus

• Regulated by erythropoietin, a glycoprotein hormone mainly produced in the kidney

Formed Elements of Blood

• Leukocytes - White Blood Cells - WBCs

• Larger than RBCs

• Have nucleus

• 5000 - 11,000 per mm³ of blood

• Fight Infection

• Can move out through capillary walls - diapedesis

Types of Leukocytes

• Granular Leukocytes

• Neutrophils (PMNs) - most abundant type - phagocytic

• Eosinophils - act against parasitic worms - destroy antigen-antibody complexes - inactivate some inflammatory chemicals of allergy

• Basophils - Mast cells in tissues - inflammation & allergy release histamine

Leukocytes

• Agranular Leukocytes

• Monocytes - largest - become macrophages in tissues - phagocytic

• Lymphocytes

• B cells

• T cells

Formation of Leukocytes

Formation of Leukocytes

Platelets

• Thrombocytes - actually broken pieces of cells (megakaryocytes)

• 250,000 - 500,000 / mm³ of whole blood

• Survive 5-9 days

• Plug up leaks in vessels

• Also secretes several chemicals involved in clot formation

Hemostasis

• Stoppage of bleeding

• Three phases

• 1. Vascular spasm

• 2. Platelet plug formation

• 3. Coagulation or blood clotting

Platelet Plug Formation

• Platelets from a plug that temporarily seals the break in the vessel wall

• Platelets also orchestrate clot formation

• When a vessel is broken the collagen below the endothelium is exposed

• The platelets swell & form spike processes & now stick to the exposed collagen

• Next the platelets degranulate - release several chemicals

Platelet Plug Formation

• Serotonin is released - enhances vascular spasm

• ADP is also released - attracts other platelets

• Thromboxane A₂ - short lived prostaglandin derivative

• Triggers aggregation and degranulation

• PGI₂ (prostacyclin) from endothelial cells limits plug formation to the local injury site

Coagulation

• Blood clotting

• Over 30 factors involved

• Eventually prothrombin activator is formed

• Prothrombin activator converts the plasma protein prothrombin to thrombin (an enzyme)

• Thrombin catalyzes the joining of fibrinogen in the plasma into a fibrin mesh

• This fibrin mesh traps blood cells & seals off the hole in the vessel

Blood Type

• Antigens - protein cell surface markers

• Antibodies - immune system proteins which act to neutralize all foreign antigens

• ABO Typing

• Type A blood - has A type antigens on the surface of the RBCs

• Type B blood - has B type antigens

• Type AB blood - has both A & B antigens

• Type O blood - has neither A or B antigens

Antigen and Blood Type

• Type A blood - has B antibodies

• Type B blood - has A antibodies

• Type AB blood - has neither A or B antibodies

• Type O blood - has both A and B antibodies

Rh Blood Typing

• Another cell surface marker

• Rh⁺ - blood cells have the Rh antigen

• Rh^- - blood cells do not have the Rh antigen

• However and Rh - person generally does not have antibodies to the Rh antigen