The Circulatory System - Blood

Part 4: Regulation & Maintenance

Circulatory System

Circulatory System aka Cardiovascular System: Responsible for transportation!Blood transports nutrients & oxygen through

the vessels, powered by the heart muscle.

Blood Elements

Formed Elements: Solid elements that make up 45% of blood volume. Red Blood CellsWhite Blood CellsPlatelets

Plasma: Clear fluid in which formed elements are suspended, make up 55% of blood volume.

Blood Properties

Two important properties of blood: Viscous: Nearly 5 times more viscous (thick)

than water. Osmolarity: The concentration of osmotic

solution helps regulate the passage of materials into and out of the blood.

Plasma

Plasma Components: 90% water 7% enzymes, nutrients, wastes, hormones, gases, & proteins 3% miscellaneous, including amino acids, nitrogenous wastes,

and some carbon dioxide & oxygen. Albumins: Proteins produced by the liver, responsible

for maintaining osmolarity; influence blood pressure, flow, and fluid balances. Also act as transport proteins for hormones & fatty acids.

Globulins: Produced by plasma cells that help with transport (Alpha & Beta Globulins) and immunity (gamma globulins).

Fibrinogen: Produced by the liver & is the essential element for blood clotting.

Sodium: Important for blood pressure & volume.

Formed Elements

Red Blood Cells (RBCs) aka Erythrocytes: Primary mode of transport for oxygen & carbon dioxide; make up the majority of formed elements.

White Blood Cells (WBCs): Immune cells – will be discussed later!

Platelets: Cell fragments that help in blood clotting.

Buffy Layer: Layer of WBCs, platelets, & RBCs in the bottom of a tube of blood fresh from the centrifuge.

Red Blood Cells

Erythrocytes aka Red Blood Cells (RBCs): Blood element responsible for transporting oxygen shaped like biconcave discs. Shape allows for rapid diffusion throughout the cell due to

increased surface area. Hemoglobin: Protein within the RBCs that allows for gas

transportation. Iron: Metal critical for hemoglobin production & oxygen

transportation. Life Cycle:

2,500,000 produced per second. Just over 100 day life cycle – when worn out they lyse and are

cleaned up by microphages in the spleen, liver, & bone marrow.

Red Blood Cells

Red Blood Cell Count varies based on altitude & is measured in cells per microliter: Males: 4.7 to 6.1 million cells per microliter.Females: 4.2 to 5.4 million cells per microliter.

RBCs outnumber WBCs 700 to 1.

Hemopoiesis

Hemopoiesis aka Hematopoeisis: The process through which formed elements are produced. Starts with stem cells colonizing bone marrow,

spleen, thymus, & liver tissue in the embryo. Myeloid Hemopoiesis: Cell production

occurring in the red bone marrow after infancy.

Hemopoiesis

Proginator Cells develop into hemocytoblasts.

Hemocytoblasts form the different cells of the formed elements.

Erythropoietin (EPO) hormone increases the number of blasts that will turn into RBCs.

Thrombopoietin (TPO) increases the formation of platelets.

White Blood Cells

Leukolcytes aka White Blood Cells (WBCs): Blood elements responsible for immune responses. Less than 1% of blood volume. 2 categories: GranulocytesAgranulocytes

White Blood Cells

Granulocytes: Contain cytoplasmic ganules (vesicles). Three types: Neutrophils aka Polymorphonuclear Leukocytes

(PMN’s): Multilobed nuclei with antimicrobial agents; Gather at infection sites to destroy bacteria through phagocytosis.

Eosinophils: Bilobed nuclei; destroy antigen-antibody complexes, allergens, and inflammatory chemicals by phagocytosis; release enzymes that destroy parasitic worms.

Basophils: Release histamine to dilate blood vessels and heparin to act as an anticoagulant. These allow WBCs to reach inflamed areas faster.

White Blood Cells

Agranulocytes: White blood cells with no granules. Two varieties: Lymphocytes: Rounded nuclei –

B Cells: Antibodies secreted by lymphocytes T Cells: Destroy foreign bodies or cancerous cells. Helper T Cells: Enhance the abilities of other immune cells.

Natural Killer (NK) Cells: White blood cells that kill tumors and virus-infected cells as part of the immune response.

Monocytes: Largest cells that form macrophages (to phagocytize foreign particles). Also activate other immune cells.

White Blood Cells

Differential White Blood Cell Count (Differential WBC Count): A calculation of the total number of each kind of WBC in the blood stream.

Average adult has a WBC of 5,000-10,000 cells per cubic millimeter.

Leukopoiesis

Leukopoiesis: The production of white blood cells. Hemocytoblasts differentiated into either…

B progenitors: T progenitors: Granulocyte macrophage colony-forming units

Granulocytes & monocytes are stored in red bone marrow until needed.

Lymphocytes are stored in lymphoid tissue until mature & needed.

Platelets

Platelets: Cell fragments!Cell membranes Pseudopods that allow for motionVesiclesNo nucleusPhagocytic!10 day life-cycle

Hemostasis

Hemostasis: The process of stopping bleeding & preventing blood loss from wounds. Mainly occurs through platelets!

5 steps: Platelets secrete growth factors to stimulate

fibroblast cell division & close the wound. Platelets secrete chemicals to attract white blood

cells. Platelets dissolve blood clots that are no longer

needed. Platelets secrete vasoconstrictors which cause

vascular spasms to prevent bleeding. Platelets form a platelet plug with their pseudopods

adhering to the vessel walls & drawing them together.

Hemostasis

Coagulation: The conversion of a soluble fibrinogen into an insoluble fibrin. Fibrin net formed which stops the blood loss. Procoagulants: Clotting factors produced by the liver

that trigger coagulation. HIGHLY dependent on Vitamin K for clot formation.

3 Steps of Coagulation: Clotting factors go through enzyme reactions via

intrinsic or extrinsic pathways to form prothrombinase (enzyme).

Prothrombin activator causes prothrombinase to turn prothrombin into thrombin.

Thrombin converts fibrinogen to fibrin & forms a clot.

Hemostasis

Clot Retraction: Tightening of the fibrin clot that pulls the edges of the blood vessel together so that the tissue may repair.

Fibrinolysis: The process of clot removal after vessel repair.

Blood Types

Agglutinogens: Antigens on the surface of the red blood cells that can react when placed with blood of a different “type”.

Two Groups of Blood Types based on Agglutinogens: ABO GroupRh Group

Blood Types

ABO Group: Based on Antigens A & B. Type A Blood: Antigen A present, Anti-B antibodies present Type B Blood: Antigen B present, Anti-A antibodies present Type O Blood: Neither antigen present, both antibodies

present. Most common blood type. Universal Donor

Type AB Blood: Both antigens present, neither antibodies present.

Least common blood type. Universal Receiver

Agglutinins: Antibodies that create an antigen/antibody reaction (clotting) if blood types are mixed.

Blood Types

Rh Group: Group based on one particular agglutinogen (named after rhesus monkey). Rh-Positive: Rh agglutinogens present on red blood

cells. Approximately 90% of population

Rh-Negative: Rh agglutinogens not present.

Anti-Rh Antibodies: Formed during an initial infusion of Rh+ blood into Rh- patient; leads to hemolytic (anti-clotting) effect during future encounters with Rh+.

Red Blood Cell Disorders

Polycythemia: Excessive levels of RBCs. Causes…HypertensionThrombosisHemhorrage

Primary Polycythemia: Typically caused by cancerous tissue.

Secondary Polycythemia: Typically caused by hypoxia (lack of oxygen).

Red Blood Cell Disorders

Anemia: Reduction of blood’s capacity to carry oxygen. Iron-deficiency Anemia: Caused by a low level of iron, which is

necessary for oxygen bonding. More common in women than men; most common type.

Pernicious Anemia: Insufficient hemopoeisis caused by lack of intrinsic factor.

Hemorrhagic Anemia: Caused by excessive RBC loss – typically trauma or ulcers.

Hemolytic Anemia: Caused by RBCs rupturing prematurely. Thalassemia: Deficiency in hemoglobin production. Aplastic Anemia: Due to destruction of red boon marrow

caused by toxins, Gamma radiation, or medications needed for hemopoises.

Red Blood Cell Disorders

Sickle-Cell Disease: Occurs when RBCs are sickle-shaped due to presence of Hb-S hemoglobin. Sickle shape causes blocking of blood

vessels which causes pain & fatigue./ Primarily found in Asia & AfricaGenetically linked

White Blood Cell Disorders

Leukocytosis: High WBC count.Can be a sign of allergy, infection, or

dehydration. Leukopenia: Low WBC count.

Can be a sign of toxic chemicals, drug use, or certain diseases.

White Blood Cell Disorders

Leukemia: Cancer of the blood-forming tissues. Death typically occurs from infection or excessive bleeding. Acute Leukemia: Uncontrolled production of

immature leukocytes occurs. Chronic Leukemia: Accumulation of mature

leukoctyes due to leukocytes not dying at the end of the normal cycle.

Platelet Disorders

Hemophilia: Clotting deficiency – typically X-linked inherited. Hemophilia A: Caused by a lack of factor VIII

that is necessary for coagulation. Most common type.

Hemophilia B: Caused by a lack of factor IX.

Platelet Disorders

Thrombus: An unwanted blood clot. Embolus: An unwanted blood clot that is

wandering throughout the blood vessels. Pulmonary Embolism: Blood clot in the

lungs. Anticoagulants: Thrombolytic agents that

can be used to reduce the possibility of clotting. Ex. Asprin, Willow bark, heparin, etc.

Blood Type Disorders

Hemolytic Disease of the Newborn (HDN): Occurs when Rh negative mother is exposed to blood from an Rh positive fetus, causing severe anemia in the infant.

Anti-Rh Gamma Globulin (RhoGAM): Injected antibodies that can be given to prevent HDN.

Anti-Rh Gamma Globulin