Hematopoiesis

Blood cell formation that occurs in the
red bone marrow found in flat bones
(skull, pelvis, ribs, sternum, proximal
epiphyses of the humerus and the femur.
Erythropoietin (EPO)

Hormone that controls rate of erythrocyte
(RBC) production
 Is produced by the kidneys
 Targets the bone marrow
Formed Elements

Accounts for 45% of whole blood
 Erythrocytes
 Leukocytes
 Platelets
Plasma

Liquid portion of the blood – accounts for
55% of whole blood
 Is 90% water
 Helps to distribute body heat evenly
Albumin
Is a plasma protein
 Regulates osmotic pressure of blood
 Helps to keep water in the bloodstream

Megakaryocytes
Fragments of bizarre multinucleate cells
 They rupture and release thousands of
pieces that seal off from surrounding fluids

Platelets
Are needed for the clotting process
Formerly called thrombocytes (platelets)


Thrombus

A clot that develops in an unbroken blood
vessel
Embolus

When a clot (thrombus) breaks away from
a blood vessel and floats freely in the
bloodstream
 Potentially life threatening
Hematocrit

The volume of a blood sample
Leukocytes
White
Cells
Are White Blood Cells (WBC’s)
 Protect, defense, immunity
 Account for less than 1% of total blood
volume
 Are complete blood cells: contain nuclei
and organelles

Diapedesis
Means “leaping across”
WBC’s are able to slip in and out of blood
vessels as needed


Leukocytosis
An increased white blood cell count
Could be indicative of a bacterial or viral
infection


Leukopenia
Abnormally low WBC count
Commonly caused by certain drugs, and
anticancer medications


Granulocytes

Contains granules (appears as grains of
sand)
 Are “philled” with sand
Types: Neutrophils
Eosinophils
Basophils
Neutrophils

Act as avid phagocytes at site of acute
infections
Eosinophils
Kills parasitic worms
Tend to increase during allergies


Basophils
Rarest form of WBC’s
Contains histamines at sites of
inflammation


Agranulocytes
Lack visible organelles
Include: lymphocytes and monocytes
 “are a “cyte” for sore eyes”


Lymphocytes


Part of the immune system
Reside in lymphatic tissues
Monocytes
Are the largest WBC
 Change into macrophages
 Help fight chronic infections

Erythrocytes
Red Blood Cells (RBC’s)
 Are anucleate
 Have few organelles
 No mitochondria
Have biconcave disks for increased surface
area for Oxygen/Carbon Dioxide


Polycythemia



Excessive or abnormal increase in RBC’s
May result from: 1) bone marrow cancer
2) High altitudes
Leads to increase viscosity, sluggish flow
Hemoglobin (Hb)
Is an iron containing protein
 Transports oxygen
 Also binds with CO2
 250 million HB molecules in 1 RBC
 Normal levels 12-18g/100ml of blood
 Males: 13-18g; Females: 12-16g

ABO Blood Groups


2 Antigens (A or B) inherits one or the
other, both or none
 Absence of both antigens = Type O
 Presence of both = Type AB
Either A or B if just one antigen present
 AB type is universal recipient
 O type is universal donor
Agglutination
Binding of the antibodies causing RBC’s to
clump
 Leads to clogging of small blood vessels

Antigens
Is recognized as “foreign”
Stimulates release of antibodies from the
immune system
 Over 30 common RBC antigens


Disorders of the clotting process
Undesirable Clotting


Thrombus
embolus
Bleeding disorders


Thrombocytopenia – is a
platelet deficiency
Hemophilia – lack Pf
factors for clotting
Hemophilia
Hereditary bleeding disorder
 “bleeder’s disease”
 Patients are given fresh plasma or
injections of missing platelet factor (Pf)

Hemostasis
Hem = blood
 Stasis = standing still
Means stoppage of blood flow


Heparin

Body’s natural anticoagulant
Coagulation
To clot
Fibrin
Is converted from fibrinogen to fibrin
Is an insoluble protein formed during blood
clotting process
Process of Blood Clotting
Is a multistep process:
1. Vascular spasms – of the smooth
muscle in the vessel wall producing a
vasoconstriction resulting from serotonin.
 Lasts up to 30 minutes
 Makes the platelets “sticky” as they are
produced
Process of Blood Clotting
2. Platelet plug forms – damaged blood
vessel releases Von Willebrand’s Factor.
 Platelets release ADP causing aggregation
and a plug to form
 An increase in the “stickiness” results
Process of Blood Clotting
3. Coagulation (clotting phase)
Platelet Factor III (PF3) releases
thromboplastin.
 PF3 and Calcium forms an activator
producing a cascade effect.
 Prothrombin (in the plasma) is converted
to Thrombin (an enzyme)
 Formation of Fibrinogen (plasma protein)
to Fibrin to trap platelets “meshwork.”
Process of Blood Clotting
Entire process normally takes 3 – 6 minutes
 A sudden and severe loss of blood leads
first to shock and eventually death
Use direct pressure to help
Elevate body part above the heart to allow
gravity to take effect
3 phases of hemostasis (process of blood clotting):
•Vascular spasms – decreases the flow of blood to the area
•Platelet plug formation – platelets become “sticky” and cause chemical release to form clot
•Coagulation – prothrombin to thrombin and fibrinogen to fibrin
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