Unit 4 - Circulatory System Part II

Blood, Blood Cells, Clotting Cascade, Blood Vessels, Blood Pressure,

Plasma and Blood Cells

Two main components of the blood

Plasma

55% of the blood, liquid portion, composed of 90% water, ions, proteins, nutrients, wastes, and gases

Blood Cells

45% of the blood, made up of RBCs, platelets, and white blood cells

Buffy Coat

1% of the blood, includes platelets and white blood cells

Formed Elements (cells)

General term for parts of the blood that includes the buffy coat and red blood cells

Albumin

Protein in plasma that maintains osmotic pressure; prevents water from leaking out of blood vessels

Gamma Globulins

Protein in plasma that is antibodies

Clotting Factors

Proteins in the plasma that include enzymes and hormones, essential to the clotting cascade

Urea

Nitrogen containing cellular metabolic waste, found in blood plasma

Bilirubin

Waste material formed as a result of RBC recycling in the liver, found in blood plasma

Hematopoiesis

Formation, development, and differentiation of blood cells; Differentiation occurs in bone marrow, some blood cell differentiation/maturation is completed in lymphoid tissue

Hematopoietic Stem Cell

Multipotent, unspecialized cells found in bone marrow/lymphatic structures (spleen), mature into various types of blood cells found in circulation

Red Blood Cells (RBCs)

Erythrocytes, lack nucleus and organelles (lost during maturation), continually dying and being replaced, contain hemoglobin

Hemoglobin

Iron containing protein found in RBCs, binds to oxygen for transport

Erythropoietin (EPO)

Hormone produced by the kidneys that stimulates increased rates of RBC production from bone marrow

Erythropoeisis

The production of RBCs; Development begins in the bone marrow and completes final stages in bloodstream

Hemolysis

Equal to rate of erythropoiesis. Destruction/recycling of old/worn out RBCs, RBC lifespan of 120 days, old/worn RBCs are phagocytized by macrophages (WBCs)

Hypoxia

Cellular oxygen deficiency; not enough oxygen in the blood results in increased rates of erythropoiesis. Caused by high altitude, anemia, circulatory problems. Stimulates kidney to release erythropoietin

Hematology

Study of blood and its disorders

Hematocrit

Diagnostic test of blood volume occupied by red blood cells; used as a tool to determine anemias. Normal male 40-54%. Normal female 38-46%.

Anemia

Abnormally low RBC hematocrit/amount

Polycythemia

Abnormally high RBC hematocrit/amount

White Blood Cells

Leukocytes, leave bloodstream and collect at points of pathogenic invasion or tissue damage, combat pathogens through phagocytosis or production of antibodies

Pathogens

Disease causing/infectious agent (i.e. bacteria or viruses)

Phagocytosis

Ingesting/engulfing pathogens

Antibodies

Proteins that attach to specific pathogens and destroy them

Leukocytosis

Increase in number of WBCs; normal response to microbes/infection

Leukopenia

Abnormally low number of WBCs

Adaptive/Acquired Immunity

Recognition and immune response to specific antigens, “memory”, slow response the first time

Major Histocompatibility Complex (MHC)

Molecule attached to APC with protein complexes that display fragments (antigens) to activate T cells to start immune response. Found on dendritic cells, macrophages, and B cells

Antigen Presenting Cell (APC)

Type of immune cell that boosts immune responses by processing and presenting antigens on its surface to other immune cells, primarily T cells. Includes dendritic cells, macrophages, and B cells

Antigen Presentation

The process where APCs break down antigens and present fragments bound to their MHC to be recognized by T cells

Innate Immunity

General/nonspecific immunity, fast responding

Antigen

A toxin or other foreign substance that causes an immune response, usually for production of antibodies. Foreign protein(s) containing fragment. 

Diapedesis

“squeezing” of WBC’s through capillary walls

Chemotaxis

Directional movement of a cell to follow the chemical signals to where they are the most concentrated

Cytotoxins

Chemicals that break apart pathogens, damage or kill cells

Platelets

Thrombocytes/cell fragments. Aid, along with specific blood proteins, in blood clotting when blood vessels have been damaged

Hemostasis

Stoppage of bleeding

Vascular Spasm

Smooth muscle in the wall of the blood vessel immediately contracts when damaged; causes vasoconstriction that reduces blood loss

Platelet plug

Formed by platelets aggregating and sticking to each other at the point of the injury; adhere to walls of the blood vessels where the break has occurred

Platelet Adhesion

The process by which platelets stick to the exposed collagen fibers at the damaged edge of the vessel; platelets have specific receptors for collagen on their plasma membrane

Platelet release reaction

Reaction where as a result of adhesion, platelets become activated and release chemicals found in their granules

Platelet Aggregation

The process of platelets sticking together to form a mass at the point of damage (platelet plug); regulated by platelet chemicals that cause nearby platelets to become activated

Platelet adhesion, release reaction, aggregation

3 steps of the formation of a platelet plug

Release of clotting factors

The release of Ca²⁺ and various proteins by platelets

Clot

Occur locally, at point of injury; blood contains anticoagulants to prevent blood from clotting spontaneously. After injury, biochemicals that trigger coagulation increase in concentration to cause a clot

Coagulation

Formation of a blood clot as the blood turns from liquid to gel, causes hemostasis

Blood Clot Formation Cascade

Release of thromboplastin which triggers reactions that produce prothrombin activator (Prothrombinase) + Ca²⁺→Converts prothrombin into thrombin→Thrombin catalyzes a reaction to convert fibrinogen into fibrin

Thromboplastin

Tissue factor, released by damaged cells, starts the blood clot formation cascade

Prothrombin

Plasma protein produced by the liver, catalyzed by prothrombinase and Ca²⁺ to produce thrombin

Thrombin

Catalyzes a reaction that converts fibrinogen (soluble) into fibrin (insoluble)

Fibrin

Forms the thread of the clot; formed elements of the blood are trapped

Fibrinogen

Protein in plasma that forms mesh around blood clots. Soluble plasma protein that is produced by the liver, reacted to form fibrin

Fibroblasts

Cell that forms connective tissue at the rupture of a blood vessel to repair it and replace the temporary blood clot

Tissue Plasminogen Activator

Released by repaired tissues, begins the dissolution of blood clot, catalyzes the reaction that converts plasminogen to plasmin

Plasminogen

Plasma protein found in blood clots, broken down in dissolution of blood clot to form plasmin

Plasmin (fibrolysin)

Enzyme that breaks down fibrin and dissolves blood clot, result of breakdown of plasminogen

Fibrinolysis

Breakdown of clot as vessel is repaired. During clot formation the plasma protein plasminogen is incorporated into the clot. New, healthy endothelial tissue secretes tissue plasminogen activator converts plasminogen→plasmin (fibrinolysin). Plasmin breaks down fibrin → dissolution of clot.

Causes of clot formation

Damaged blood vessel. May be inadvertently caused by roughened endothelial surface of blood vessels caused by atherosclerosis (buildup of plaque deposits) or infection

Thrombus

Clot attached to a vessel wall

Embolus

Free-floating clot; may lead to heart attack or stroke

Anticoagulants

Group of substances used as blood thinners, inhibit blood clotting. eg Heparin

Closed system of tubes

Function of the blood vessels that transports blood/materials away from the heart, through tissues, and back to the heart

Exchange of Materials

Characteristic of blood that allows for the diffusion of nutrients and wastes between blood and body tissues (O₂ and CO₂)

Arteries

Blood vessels with thick muscular walls, highly elastic. Carry blood away from heart under high pressure, normally carry oxygenated blood

Arterioles

Small branch of an artery, leading into capillaries

Veins

Blood vessels with thinner walls; may contain valves which prevent the backflow of blood with low pressure.

Venules

Very small veins, collect blood from capillaries before merging into veins

Capillaries

Microscopic vessels, permit exchange of nutrients and wastes between blood vessels and tissues

Coronary

Blood supply to muscles of the heart itself

Cerebral

Blood supply to the brain

Hepatic Portal

Venous blood from GI organs/spleen feed into the vein and liver. Materials in blood are modified/processed by the liver before continuing onto general circulation.

Renal

Vessels into/out of kidneys where blood is filtered; nitrogenous wastes removed

Venous Return

Volume of blood flowing back to the heart through systemic veins

Heart, Skeletal Pump, Respiration Pump

Three factors impacting venous return

Heart

Factor of venous return where LV pushes blood through the systemic vessels by contracting, least impact of return

Skeletal Pump

Factor of venous return due to contraction of leg muscles that causes blood to be pushed through valves closer to the heart and back against valves further from the heart

Respiration Pump

Factor of venous return due to inhalation→thoracic cavity pressure below pressure of abdominal cavity; abdominal vessels compressed → greater volume of blood moves into the decompressed thoracic veins/RV. When pressure reverses (exhalation) valves prevent backflow of blood

Sphygmomanometer

Blood Pressure cuff

Vasoconstriction

Smooth muscles contract narrowing vessels; increases BP

Vasodilation

Smooth muscles relax and enlarge diameter of blood vessels; decreases BP

Systolic Blood Pressure

Force exerted by blood on walls of arteries during periods of ventricular contraction

Diastolic Blood Pressure

Force exerted by blood on walls of arteries during periods of ventricular relaxation

120/80

Normal blood pressure, systolic/diastolic

Hypertension

Chronic high blood pressure, caused by poor diet, sedentary lifestyle, family history, overweight, age, stress. Causes damage to vessels, heart, brain (vessels rupture = stroke), kidneys. Heart works harder→weakens walls→heart failure

Factors Impacting Blood Pressure

Heart rate/stroke volume, blood volume, blood viscosity, and diameter of blood vessels

Heart Rate/Stroke Volume

Factor impacting blood pressure, revolves around amount of blood per contraction and the number of contractions. Increase causes BP to go up

Blood Viscosity

Factor impacting blood pressure relating to how thick the blood is. Thicker blood = increased resistance = BP increases. Related to amount of blood cells/plasma proteins

Blood Volume

Factor impacting blood pressure relating to how much blood there is. 5L for normal adult. Amount decreases (dehydration/hemorrhage) BP decreases. Amount increases (water retention) BP increases.

Diameter of Blood Vessels

Factor impacting blood pressure relating to vasoconstriction and vasodilation