Circulatory system and Blood

Functions of the Circulatory System

• The cardiovascular system consists of the heart and blood vessels.
• The circulatory system includes the heart, blood vessels, and blood.

Functions of the Circulatory System

• Transportation of O2, CO2, nutrients, wastes, hormones, and stem cells from bone marrow.
• The circulatory system protects the body via the immune system and clotting.
• The circulatory system regulates fluid balance, pH, and temperature control.

General Properties of Blood

• Adults typically have 4 to 6 liters of blood.
• Blood is composed of plasma and formed elements.
• Blood is slightly warmer than the body's core temperature (100.4°F).
• The color of blood is dark red when oxygen is absent and bright red when bound to RBCs.
• The normal pH range of blood is 7.35-7.45.
• Blood is denser, or heavier, than water.

Components of Blood: Liquid vs Solid

• Liquid (Plasma) contains Water, Proteins, Nutrients, electrolytes and Wastes
• Solid (formed elements) contains white blood cells or leukocytes, red blood cells or erythrocytes and platelets

Effects of Centrifugation

• Centrifugation causes the heaviest blood components to settle at the bottom of the tube
• Plasma appears as a clear, yellow fluid at the top of the tube
• Buffy coat is a narrow band of white blood cells and platelets
• Erythrocytes or RBCs are heaviest and settle to the bottom
• Hematocrit is a packed cell value that is the percentage of whole blood occupied by RBCs.

Blood Plasma Components

• Plasma is the liquid portion of blood.
• Albumin is a protein found in blood that transports substances and influences blood viscosity and osmolarity.
• Globulins (antibodies) are proteins found in blood that combat pathogens in specialized immune responses.
• Fibrinogen is a component of blood clots.
• Nitrogenous wastes (urea) found in blood.
• The Nutrients found in blood include sugars, fats, amino acids, vitamins, and minerals.
• The Gases found in blood include dissolved O2, CO2, and nitrogen.
• The Electrolytes found in blood include K+, Cl-, Mg+, Ca2+Na+.
• Serum is the remaining fluid when blood is allowed to coagulate (clot) and solids are removed.
• Serum is identical to plasma except for the absence of fibrinogen (clotting proteins).

Hematopoiesis: Blood Cell Formation

• Hematopoiesis is the production of blood including plasma and formed elements.
• Billions of platelets, RBCs, and WBCs must be made each day.
• All other formed elements are produced in bone marrow.
• Hematopoietic stem cells (HSCs) are multipotent stem cells in bone marrow that give rise to all formed elements.
• HSCs continue creating new cells throughout the lifetime of an organism

Erythrocytes (Red Blood Cells)

• Erythrocytes carry oxygen from the lungs to tissues.
• Erythrocytes carry CO2 from tissues to lungs.
• Erythrocytes are designed to maximize gas exchange and transport.
• Erythrocytes lose nearly all organelles during development.
• Erythrocytes have no mitochondria and use oxygen for energy.
• Erythrocytes primarily consist of hemoglobin to carry gases.

Hemoglobin Composition

• Each hemoglobin (Hb) protein consists of:
• Four protein subunits (globins)
• Four heme groups
• Heme is a respiratory pigment that turns red when it binds to O2.
• The iron atom (Fe) at the core binds to O2.
• There are four O2 binding sites per Hb.

Erythropoiesis: RBC production

• Erythropoiesis occurs in bone marrow
• Erythropoiesis produces 1 million RBCs per second.
• RBCs have an average life span of about 120 days.
• Erythropoietin (EPO), produced mainly by the kidneys, stimulates erythropoiesis.
• Sufficient iron (Fe) from diet, Vitamin B12, folic acid, Vitamin C, and copper are needed for erythropoiesis.
• Erythropoiesis is Controlled by a negative feedback loop.

Erythrocyte Disorders

• Polycythemia is an excess of RBCs.
• Primary polycythemia is due to cancer in the erythropoietic cell line in bone marrow.
• Secondary polycythemia is caused by dehydration, smoking, air pollution, and excessive aerobic exercise.
• Anemia is a deficiency of RBCs or hemoglobin.
• Hemorrhagic anemias are caused by excessive bleeding.
• Hemolytic anemias are caused by excessive RBC destruction.
• Inadequate erythropoiesis

Anemia: Deficiency of RBCs

• Pernicious anemia is caused by inadequate vitamin B12 absorption.
• Reduced production of the intrinsic factor in the stomach leads to Pernicious Anemia
• Iron deficiency can lead to a type of Anemia
• Aplastic and Sickle-Cell Anemia are other forms of anemia

Blood Types

• Blood types depend on the interaction between antigens and antibodies.
• Antigens are genetically unique molecules on the surface of all cells.
• Antigens enable the body to distinguish its own cells (self) from foreign materials (non-self).
• Antibodies are proteins secreted as part of a specific immune response, binding to the antigens and marking them for destruction.

ABO Blood types

• ABO blood groups are determined by the presence or absence of antigens on RBCs.
• RBCs can have A antigen, B antigen, both A and B, or neither.
• Type A blood indicates the presence of A antigen.
• Type B blood indicates the presence of B antigen.
• Type AB blood indicates the presence of both A and B antigens.
• Type O blood presents with no antigens.
• Blood plasma contains antibodies opposite of the antigens.

ABO Blood typing: Hemagglutination

• Hemagglutination assay is an experiment to determine the presense of a positive reaction
• Clumping of red blood cells is a positive reaction
• Blood to be tested is added separately to serum containing anti-A and anti-B antibodies
• Type A blood reacts with anti-A serum
• Type B blood will react with anti-B serum
• Type O blood will not react with either anti-A or anti-B serum

Transfusion Reactions for Blood Types

• Type O- is known as the "universal donor" because it contains no antigen A or antigen B, and therefore does not react with antibodies from the donor blood
• Type AB+ is known as the "universal recipient" because it contains no anti-A or anti-B antibodies in plasma, and therefore does not attack other blood types

Leukocytes: White Blood Cells

• Leukocytes travel in blood to tissues to combat pathogens and foreign substances.
• Leukocytes play a role in responding to tissue damage.
• Granulocytes: include Neutrophils, Eosinophils, and Basophils
• Agranulocytes: include Lymphocytes and Monocytes

Types of Granulocytes

• Neutrophils are the most abundant granulocytes at 60-70% of WBCs
• Neutrophils present with a 3-5 lobed nucleus and granules present in the cytoplasm
• Neutrophils aggressively phagocytize bacteria
• Eosinophils are 2-4% of WBCs and present with red/orange granules in the cytoplasm
• Eosinophils respond to parasitic infections and dispose of allergens
• Basophils are the least abundant of granulocytes and present with many dark violet granules in cytoplasm
• Basophils release histamine, a vasodilator, and heparin.