04.3B AN U4P1 (PART B) Hematopoiesis & Hemostasis

Hematopoiesis

A process in which new blood cells are formed.

Site of blood cell formation

Bone marrow

Hemocytoblast

A stem cell found in bone marrow that give rise to all the formed elements of the blood

Lymphoid stem cell

A stem cell derived from a hemocytoblast that gives rise to lymphocytes

Myeloid stem cell

A stem cell derived from a hemocytoblast that gives rise to red blood cells, monocytes, neutrophils, eosinophils, basophils, and platelets

Erythropoietin

A hormone produced and released by the kidney that stimulates the production of red blood cells by the bone marrow

Hemostasis

A process that results in the formation of a blood clot

Hemostasis (Phases)

Vascular spasms
Platelet plug formation
Coagulation

Vascular spasms

Immediate response to blood vessel injury

Platelet plug formation

Anchored platelets release chemicals to attract more platelets forming a platelet plug

Coagulation

Process in which a clot forms

Blot clot

Occurs within 3 to 6 minutes
Remains as endothelium regenerates
Broken down after tissue repair

Thrombus

A clot in an unbroken blood vessel
Can be deadly in areas like the heart

Thromboplastin

A complex phospholipid enzyme that works with tissue factor to initiate the clotting process by converting prothrombin into thrombin in the presence of calcium ion

Thrombin

An enzyme that converts fibrinogen to fibrin during coagulation

Prothrombin

A protein present in blood plasma that is converted into active thrombin during coagulation.

PF3 (platelet factor 3)

A phospholipid that coats the surfaces of the platelets that interacts with tissue factor when tissues are injured to produce thromboplastin.

Prothrombin activator

A protein formed by clotting factors from damaged tissue cells and platelets that converts prothrombin into thrombin, a step essential to forming a blood clot.

Vitamin K

Vitamin that helps to regulate blood clotting

Fibrinogen

A soluble plasma protein that is converted to fibrin in the clotting process

Fibrin

An insoluble protein formed from fibrinogen during the clotting of blood. It forms a fibrous mesh that stops the flow of blood.

Calcium ions

Ions that participate in many reactions that help produce fibrin

Site of Hematopoiesis (Embryo)

Yolk Sac / Liver

Site of Hematopoiesis (3-7 months gestation)

Spleen

Site of Hematopoiesis (Birth)

Mostly Bone Marrow / Liver & Spleen as needed

Site of Hematopoiesis (Adult)

Bone marrow of skull, ribs, sternum, vertebral column, pelvis, proximal ends of femurs

Kidney

Organ that produces most erythropoietin as a response to reduced oxygen levels in the blood

Platelet adhesion

Process during hemostasis in which platelets become sticky and begin to adhere to injured site

Serotonin

Substance released by activated platelets that causes blood vessel muscles constrict and enhances the formation of the platelet plug

Tissue factor

A membrane protein found in tissues that initiates clotting when tissues are damaged