Anatomy and Physiology II Unit II

Blood

fluid connective tissue

Hematology

study of blood

Composition of blood

matrix, formed elements, and plasma proteins

Matrix

plasma of blood

Formed elements of blood include

erythrocytes, leukocytes, lymphocytes, and platelets

Erythrocytes

red blood cells

Leukocytes

white blood cells

Lymphocytes

white blood cells that aid the immune system

Platelets

cell fragments responsible for clotting and preventing bleeding

Hematocrit

percentage of blood occupied by formed elements

Plasma proteins

albumins, globulins, fibrinogen, regulatory proteins

Albumins

plasma protein responsible for transport, maintenance of osmolarity by binding solutes

Globulins

plasma protein that is an antibody

Fibrinogen

plasma protein that is responsible for clotting

Regulatory proteins

plasma proteins that are hormones and enzymes

Erythrocytes characteristics

no nucleus

no mitochondria

last about 4 months

contain hemoglobin (Hb)

Hemoglobin consists of

two alpha chains, two beta chains, and heme with iron

Hematopoiesis

making blood cells

Hemocytoblasts

myeloid and lymphoid stem cells

Hemocytoblasts are an example of

multipotent stem cells

Myeloid cells in bone marrow

produce RBCs and most WBCs

Lymphoid cells

produce lymphocytes

Erythropoiesis

making RBCs

Leukopoiesis

making leukocytes

Lymphopoiesis

making lymphocytes

Multipotent stem cells characteristics

after birth and fully committed to a lineage of cells

Pluripotent stem cells characteristics

fetal development and starting to specialize

Stem cells that make megakaryocytes are an example of

pluripotent stem cells

Megakaryocytes make

platelets

Megakaryocytopoiesis

making megakaryocytes

Totipotent stem cells characteristics

zygote and not committed to a lineage, that can make other stem cells

Erythrocytes are stimulated by

EPO

Leukocytes are stimulated by

EPO and cytokines

Lymphocytes are stimulated by

interleukins (kind of cytokine) and possibly IGFs

Megakaryocytes are stimulated by

thrombopoietin and meg-CSF

Thrombopoietin is produced by

the liver and kidney

meg-CSF is produced by

T-cells

Hemolysis

rupture of RBCs and releases hemoglobin for recycling

In hemolysis, macrophages digest

the cell membrane

In hemolysis, hemoglobin is broken down into

heme, iron, and globin

In hemolysis, globin is

broken down into amino acids

In hemolysis, heme is

broken down into bilirubin, which produces bile in the liver

In hemolysis, Fe⁺⁺⁺ is

reused or stored in the liver

Polycythemia

too many RBCs

Polycythemia is caused by

smoking, lung disease, exogenous EPO use (excess EPO)

Dangers of polycythemia

heart attacks and strokes

Anemia

insufficient RBCs or Hb

Anemia is caused by

inadequate erythropoiesis, insufficient Fe⁺⁺⁺ for Hb, sickle-cell disease

Dangers of anemia

weakness, confusion, lethargy

Characteristics of all WBCs are

migration out of blood into tissues, amoeboid movement, chemotaxis, and phagocytosis

Margination

the process in which leukocytes move toward the vessel walls

Diapedesis

the process in which leukocytes move out of the bloodstream and pass through the vessel walls

Amoeboid movement

the process in which leukocytes move using cytoplasmic flow, forming pseudopodia (false feet)

Chemotaxis

the directed movement of leukocytes in response to chemical signals, migrating to sites of infection or inflammation

Phagocytosis

the process by which leukocytes engulf and destroy microorganisms and dead cells

Lysosomal granules/enzymes

destroys viruses or bacteria (cytotoxic)

Granulocytes

appear grainy under microscope

Agranulocytes

do not appear grainy under microscope

Neutrophils

granulocytes that are the first line of defense against infection

Neutrophils are part of the

antibody-antigen complex (phagocytosis of pathogens with an antibody)

Antigen-antibody complexes

viruses have membrane proteins that stick out, some of which are receptors

antigens are name tags and membrane proteins and have a non-specific area

have epitope or antigenic determinant (specific part of antigen)

leukocytes recognize the epitope, while lymphocytes mirror the epitope (paratope)

B-cells release antibodies that also have a paratope for a specific virus

Eosinophils are responsible for

phagocytizing antigen-antibody complexes and exocytozing toxins to kill larger pathogens (parasites)

Eosinophilic granuloma

autoimmune disorder that manifests mainly in the dermis

Basophils are responsible for

secreting histamine and heparin (for vasodilation and anticoagulation (inflammation)

Agranulocytes

no lysosomal granules in cytoplasm

Types of agranulocytes

monocytes and lymphocytes

Monocytes

agranulocytes called macrophages after diapedesis into tissues

Monocytes are responsible for

antigen presentation to activate B-cells and secretion of cytokines

Types of lymphocytes

T-cells, B-cells, and NK cells

T-cells

cell mediated specific immunity

• B-cells – antibody mediated specific immunity

Natural Killer (NK) cells – nonspecific immunity, secrete perforins to break pathogen cell membranes (allows cytotoxic enzymes into pathogen)

Leukopenia

lower than normal WBC count

Causes of leukopenia

AIDS, heavy metal poisoning, immunosuppresant drugs

Leukocytosis

greater than normal WBC count

Causes of leukocytosis

infection, allergies, hypercytokinemia (excessive levels of cytokines in the bloodstream)

Leukemia

cancer of hematopoietic stem cells

Leukemia can cause

leukocytosis

Types of leukemia

myeloid leukemia and lymphoid leukemia

Myeloid leukemia

uncontrolled production of monocytes, neutrophils, eosinophils, and basophils

Lymphoid leukemia

uncontrolled production of lymphocytes

Phases of hemostasis

Vascular phase, platelet phase, coagulation phase

Vascular phase of hemostasis

When endothelial cells contract, they reveal the basement membrane, which contains proteins that trigger clotting by activating clotting factors and initiating platelet aggregation. The endothelial cells release paracrine factors that help activate clotting and initiate vasoconstriction.

Platelet aggregation

platelets clump together to form a clot, which stops bleeding

Paracrine factors

proteins that cells produce to signal and influence nearby cells in the same tissue

Platelet phase of hemostasis

When a blood vessel is damaged, platelets attach to the exposed endothelial cells at the injury site and then secrete platelet-activating factor to attract more platelets, causing them to aggregate and form a plug. Platelets also secrete thromboxane, which constricts the blood vessel. Negative feedback mechanisms like histamine and heparin are released from basophils to prevent excessive clotting.

Platelet activation

secretion of platelet-activating factor to attract more platelets

Coagulation phase

Fibrin activation occurs because of a cascade of chemical reactions, which consists of the extrinsic pathway, intrinsic pathway, and common pathway. Pathways involve many chemical reactions and factors, and an absence of one of these factors leads to an inability to clot (hemophilia). All three pathways produce thrombin which converts fibrinogen into fibrin, essentially a net to capture more platelets.

Fibrinolysis

breakdown of the clot

Fibrinolysis process

Plasminogen, a liver protein, attracts to fibrin and incorporates into the clot. Endothelial cells slowly secrete tissue plasminogen activator (t-PA) which converts plasminogen into plasmin, which breaks down fibrin, eventually breaking down the clot.

Lymphatic system includes

lymph nodes, spleen, lymphatic vessels, and thymus

Lymph nodes

to filter lymph

Spleen

to filter blood

Lymphatic vessels function

to carry interstitial fluid to be filtered before returning to the blood

Thymus function

to direct` lymphocyte development

Antigens

membrane proteins on cells

Antigens are used to identify

pathogens, foreign cells, and self cells

Pathogens

viruses and bacteria

Foreign cells

transplanted tissue

Antigen characteristics

specific regions called epitopes