Week 1: Blood Composition and Hematopoiesis

This set of vocabulary flashcards covers the key terms and concepts related to blood composition, plasma proteins, hematocrit, hematopoiesis, and the regulatory hormones involved in blood cell production.

Blood

A liquid connective tissue whose main function is to transport substances throughout the body; composed of plasma (55%) and formed elements (45%).

Plasma

The clear, light-yellow fluid matrix of blood containing water, nutrients, hormones, electrolytes, gases, wastes, and plasma proteins.

Formed Elements

The cellular components of blood—erythrocytes, leukocytes, and platelets—suspended in plasma.

Erythrocyte (Red Blood Cell)

A formed element that transports oxygen from the lungs to tissues and carries carbon dioxide back to the lungs.

Leukocyte (White Blood Cell)

A formed element responsible for immunologic protection by combating pathogens and coordinating responses to tissue damage.

Thrombocyte (Platelet)

A cell fragment derived from megakaryocytes that plays a central role in blood clotting (hemostasis).

Hematology

The study of blood, blood-forming organs, and blood diseases.

Cardiovascular System

The heart and blood vessels considered together; when blood is included, it forms the circulatory system.

Circulatory System

The heart, blood vessels, and blood, functioning to transport substances throughout the body.

Hematocrit

The percentage of whole blood volume occupied by red blood cells; also called packed cell volume.

Buffy Coat

The thin, cream-colored layer of leukocytes and platelets that forms between plasma and erythrocytes after centrifugation, about 1% of blood volume.

Blood Serum

Plasma from which clotting proteins (notably fibrinogen) have been removed.

Albumin

The most abundant plasma protein (≈60%) that transports solutes and buffers pH; major determinant of blood viscosity and osmolarity.

Globulins

A class of plasma proteins (≈36%) subdivided into α, β, and γ; functions include transport of lipids, hormones, minerals, and immunity (γ-globulins = antibodies).

Fibrinogen

A soluble plasma protein (≈4%) that is converted to fibrin to form the framework of a blood clot.

Viscosity (of Blood)

The thickness or resistance to flow of blood, largely influenced by plasma proteins such as albumin and fibrinogen.

Osmolarity (of Blood)

The concentration of dissolved particles in blood; determines water movement between bloodstream and tissues.

Hyperalbuminemia

Excessive albumin concentration leading to high blood viscosity and osmolarity, increased blood volume, and higher blood pressure.

Hypoalbuminemia

Deficient albumin concentration resulting in low blood viscosity and osmolarity, reduced blood volume, hypotension, and tissue edema.

Hematopoiesis

The continuous process of producing formed elements of blood; occurs mainly in red bone marrow after birth.

Hematopoietic Stem Cell (HSC)

A pluripotent stem cell in red bone marrow that gives rise to all formed elements of blood.

Myeloid Stem Cell

A descendant of an HSC that differentiates into erythrocytes, platelets, and most leukocytes (neutrophils, eosinophils, basophils, monocytes).

Lymphoid Stem Cell

A descendant of an HSC that differentiates into lymphocytes (T cells, B cells, NK cells).

Erythropoiesis

The production of red blood cells, stimulated by the hormone erythropoietin.

Leukopoiesis

The production of white blood cells, regulated by colony-stimulating factors (CSFs).

Thrombopoiesis

The production of platelets; megakaryocytes shed platelet fragments under stimulation by thrombopoietin.

Erythropoietin (EPO)

A hormone (85% kidney, 15% liver) that stimulates erythropoiesis.

Thrombopoietin (TPO)

A hormone produced by liver and kidneys that promotes platelet formation from megakaryocytes.

Colony-Stimulating Factors (CSFs)

Hormones that stimulate the proliferation and differentiation of specific white blood cell lines during leukopoiesis.

Megakaryocyte

A giant bone-marrow cell that fragments to produce platelets during thrombopoiesis.

Red Bone Marrow

Primary hematopoietic tissue in adults, located in the sternum, ribs, skull, pelvis, vertebrae, and epiphyses of long bones.

Yellow Bone Marrow

Adipose-rich marrow that stores fat; not hematopoietic.

Blood Fractionation

The process of centrifuging blood to separate plasma, buffy coat, and erythrocytes by density.

Functions of Blood – Transport

Carries O₂, CO₂, nutrients, hormones, heat, and metabolic wastes throughout the body.

Functions of Blood – Regulation

Maintains pH, body temperature, and fluid volume distribution.

Functions of Blood – Protection

Provides immunity via leukocytes and antibodies, initiates clotting to prevent blood loss.

Gamma Globulins

Immunoglobulins (antibodies) that provide specific immune defense against pathogens.

Fibrin

Insoluble protein formed from fibrinogen during clotting; creates the meshwork of a blood clot.