04.3B AN U4P1 (PART B) Hematopoiesis & Hemostasis (WITH DISORDERS)

Hematopoiesis

Blood cell formation

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 is initiated when there is a break in a blood vessel that results in the stoppage of blood flow

Hemostasis (Phases)

Vascular spasms
Platelet plug formation
Coagulation

Vascular spasms

Platelets begin to adhere to injured site
Anchored platelets release serotonin
Serotonin causes blood vessel muscles to spasm
Spasms narrow the blood vessel, decreasing blood loss

Platelet plug formation

Collagen fibers are exposed by a break in a blood vessel
Platelets become "sticky" and cling to fibers
Anchored platelets release chemicals to attract more platelets
Platelets pile up to form 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

Embolus

A thrombus that breaks away and floats freely in the bloodstream
Can later clog vessels in critical areas such as the brain

Thrombocytopenia

Platelet deficiency
Even normal movements can cause bleeding from small blood vessels that require platelets for clotting

Hemophilia

Hereditary bleeding disorder
Normal clotting factors are missing

Thromboplastin

Essential tissue factor that aides in the production of thrombin from prothrombin

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 during coagulation

Prothrombin activator

A protein formed by clotting factors from damaged tissue cells and platelets; it 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