BLOOD

COMPONENTS, PHYSICAL CHARACTERISTICS, AND VOLUME

Blood transports everything (nutrients, wastes, and body heat)

Blood is a complex fluid connective tissue with both solid and liquid components. Solid – living blood cells (formed elements)

Erythrocytes (red blood cells –RBCS) Leukocytes (white blood cells –WBCS) Platelets (function in the blood-clotting process)

Liquid – nonliving fluid matrix (plasma)

An average blood sample (hematocrit) contains (by volume): 55% plasma 45% RBCs Less than 1% WBCs Less than 1% platelets

Blood color varies from scarlet (oxygen-rich) to a dull red (oxygen-poor)

Whole blood is slightly alkaline (pH 7.35 – 7.45)

8% of body weight Total adult blood volume is about 6 quarts

PLASMA

Straw-colored fluid 90% water Helps to distribute body heat evenly

throughout the body Over 100 different solutes

(plasma proteins, nutrients, respiratory gases, hormones, wastes, and products of cell metabolism)

Plasma proteins are most abundant solutes Most are made by the liver Not used for cellular metabolism Composition varies continuously as cells remove

or add substances to the blood Body organs make dozens of adjustments daily

to maintain solutes at life-sustaining levels.

FORMED ELEMENTS

Erythrocytes Ferries oxygen in blood to all cells Anucleate Contain very few organelles Contains iron-containing hemoglobin (Hb) protein

to transport oxygen Lack mitochondria and make ATP by anaerobic

mechanisms Small biconcave cells that provide a large

surface area relative to volume Outnumber WBCs by about 1000 to 1

About 5 million RBC/mm³ (as the RBC volume increases, blood viscosity increases)

The more Hb a RBC contains, the more oxygen it will carry

Average of 12-18 hemoglobin per 100 ml blood A single RBC contains about 250 million Hb

molecules Each Hb can carry 4 molecules of oxygen So each RBC carry about 1 billion molecules of oxygen

Leukocytes Far less numerous than RBCs 4,000 – 11,000 WBC/mm³ The only complete cells in blood (contain nuclei

and usual organelles) Helps defend the body against damage by

bacteria, viruses, parasites, and tumor cells Able to slip into and out of the blood vessels

(diapedesis) to cause inflammatory or immune responses

Leukopenia is an abnormally low WBC count

Can locate areas of tissue damage and infection in the body Respond to certain chemicals that diffuse from the

damaged cells (positive chemotaxis) Following the diffusion gradient to pinpoint areas of

tissue damage Gather in large numbers to destroy foreign substances

or dead cells The body speeds up their production

Total WBC count above 11,000 cells/mm³is referred to as leukocytosis Indicates the presence of a bacterial or viral infection

in the body

Platelets Not cells in the strict sense Fragments of very large multinucleate cells

called megakaryocytes that rupture Normal platelet count in blood is about

300,000/mm³ Needed for the clotting process

Write a paragraph/overview of what we learned about blood.

Draw a picture and thoroughly describe each of the solid/cellular components of blood (RBC, WBC and platelets)

THIS IS DUE AT THE END OF THE PERIOD!!!

BLOOD CELL FORMATION

Occurs is red bone marrow Flat bones of the skull and pelvis, ribs, sternum,

and proximal epiphysis of the humerus and femur. Each type of blood cell is produced in different

numbers in response to body needs and stimuli All formed elements arise from a common type

of stem cell ( hemocytoblast) in the red bone marrow Two types of descendents1. Lymphoid stem cell – produces lymphocytes2. Myeloid stem cell – produces all other classes of

formed elements

RBCs are unable to divide (anucleate) and have a limited life span of 100 to 120 days

They begin to fragment and their remains are eliminated by the phagocytes in the spleen and liver

Lost cells are replaced more or less continuously

Developing RBCs divide many times and then begin synthesizing huge amounts of hemoglobin

When hemoglobin has been accumulated, nucleus and most organelles are ejected and the cell collapses

The young RBC (reticulocyte) still contains some rough ER but begins transporting oxygen

Within two days they have ejected the remaining ER and have become fully functional erythrocytes

The process from hemocytoblast to mature RBC takes 3 to 5 days

Platelet production is accelerated by thrombopoietin

Rate of erythrocyte production is controlled by a hormone called erythropoietin from liver and kidneys When blood levels of oxygen begin to decline, the

kidneys increase release of erythropoietin Bone marrow is targeted and is stimulated to

make more RBCs Excessive amount of oxygen in the bloodstream

depresses erythropoietin release and RBC production

Colony stimulating factors (a hormone) trigger formation of leukocytes and platelets and also enhance the ability of mature leukocytes to protect the body

HEMOSTASIS

Stoppage of blood flow is fast and localized Blood loss at the site is permanently

prevented when fibrous tissue grows into the clot and seals the hole in the blood vessel.

Three phases occur in rapid sequence

1. Platelet plug formation Membrane is broken so endothelium and

collagen fibers are exposed to oxygen Platelets become “sticky” and cling to the

damaged site Platelets release chemicals that attract more

platelets Platelet plug is formed

2. Vascular spasms Platelets release serotonin that causes the

blood vessel to go into spasms Blood loss decreases until clotting can occur

3. Coagulation Injured tissues release thromboplastin (helps

the clotting process) A platelet phospholipid interacts with

thromboplastin and Ca⁺ to form a prothrombin activator

The activator converts prothrombin in the plasma into the enzyme thrombin

Thrombin joins soluble fibrinogen proteins into long hair-like molecules of insoluble webbing

Coagulation continued Forms a meshwork that traps the RBCs and

forms the basis of the clot Within the hour, the clot begins to retract,

squeezing serum (plasma minus the clotting proteins) from the mass and pulling the ruptured edges of the blood vessel closer together

Normally, blood clots within 3 to 6 minutes Once the clotting cascade has started,

triggering factors are rapidly inactivated to prevent widespread clotting

Eventually the endothelium regenerates and the clot is broken down

Create a comic strip of hemostasis including pictures and thoroughly descriptive captions.

DISORDERS OF HEMOSTASIS

Undesirable Clotting Usually occurs in the legs Clot that develops and persists in an unbroken

blood vessel is a thrombosis May prevent blood flow if large enough

A thrombosis that breaks away from the vessel wall and floats freely in the bloodstream is an embolus Usually no problem unless/until it lodges in a blood

vessel Caused by anything that roughens the blood

vessel endothelium and encourages clinging of platelets

Slowly flowing blood or blood pooling is another risk factor (especially in immobilized patients)

Bleeding disorders Common causes are platelet deficiency, deficits

of clotting factors and genetic conditions Thrombocytopenia results from an insufficient

number of circulating platelets Normal movement causes spontaneous bleeding from

small blood vessels (petechia) Hemophilia is a hereditary bleeding disorder

Lack of the factors needed for clotting Minor tissue trauma results in prolonged bleeding and

can be life-threatening

HUMAN BLOOD GROUPS

Plasma membranes of RBCs have genetically determined proteins (antigens)

Each of us tolerates our own cellular (self) antigens

RBC proteins will be recognized as foreign if transfused into another person with different RBC antigens

Antibodies present in the plasma attach to “foreign” RBCs causing RBCs to clump (agglutination)

This leads to the clogging of small blood vessels throughout the body

Foreign RBCs are lysed and Hb is unable to deliver oxygen

Clogged vessels affect kidney tubules to cause kidney failure, fever, chills, nausea, and vomiting may occur.

Over 30 common RBC antigens ABO blood groups are based on which of the

two antigens (type A or B) a person inherits Absence of both antigens results in blood type O Presence of both antigens results in blood type

AB Possession of either A or B antigen yields type A

or B blood, respectively

Rh blood groups are based on agglutinogen D (originally identified in Rhesus monkeys)

Most Americans are Rh⁺ (RBCs carry the Rh antigen)

If an Rh⁺ person receives Rh⁺ blood their immune system begins producing anti- Rh⁺ antibodies Hemolysis does not occur with the first

transfusion It takes time for the body to react and start

making antibodies

In subsequent transfusions, a typical reaction occurs (patient’s antibodies attack/rupture donor RBCs)

First time pregnant Rh⁺ women who carry Rh⁺ babies usually results in the delivery of a healthy baby Mother is sensitized by Rh⁺ antigens and forms

anti- Rh⁺ antibodies If she becomes pregnant again with an Rh⁺

baby, her antibodies will cross the placenta and destroy the baby’s RBCs

DEVELOPMENTAL ASPECTS OF BLOOD

Embryonic development of the entire circulatory system occurs within 28 days

Embryonic blood cells are circulating in the newly formed blood vessels around day 28

Fetal Hb has a greater ability to pick up oxygen (fetal blood is less oxygen-rich than that of the mother)

Fetal blood cells are gradually replaced by RBCs that contain the more typical Hb

Fetal RBCs are destroyed and the products are released in the bile

If this happens at a rate faster that the immature liver can handle, the infant becomes jaundiced

Write a journal entry as if you are a person suffering from a hemostatic disorder. You must explain your disorder and how you feel about having that disorder. You may also portray a doctor explain what to expect while telling a patient that they have that disorder, are pregnant with a child who has the disorder. This is due at the end of the period!