BloodUnit 9

Blood is the only fluid tissue in the body Although it appears to be thick and uniform,

it is actually composed of solid and liquid components

Blood cells = formed elements Non-living fluid = plasma Red blood cells = erythrocytes White blood cells = leukocytes

Composition and Function

Erythrocytes make up ~45% of the volume of a blood sample this percentage is called the hematocrit

Leukocytes make up less than 1% = buffy coat

Plasma makes up the remaining ~55% Oxygenated blood looks bright red Deoxygenated blood looks dull red pH between 7.35 and 7.45 ~8% of body weight, 5-6 liters

Composition and Function

90% water Contains over 100 different substances,

including nutrients, metal ions, respiratory gases, hormones, proteins, and other cell metabolism products composition varies continuously

Most abundant solutes are plasma proteins mainly made in liver, serve a variety of functions

Albumin = helps maintain osmotic pressure of blood by keeping water in the bloodstream

Clotting proteins stem blood loss Antibodies protect body from pathogens

Plasma

Plasma composition varies continuously, but is kept relatively constant through homeostatic mechanisms

Acidosis = blood is too acidic Alkalosis = blood is too basic Liver, kidneys, respiratory organs, etc. work

to keep plasma composition stable Plasma helps transport various substances

and distribute body heat evenly throughout the body

Plasma

Red blood cells (RBCs) – carry oxygen to all cells in the body

Don’t have a nucleus, very few organelles Mature RBCs are just sacs of hemoglobin

molecules Hemoglobin (Hb) is a protein that contains iron and

helps transport oxygen and carbon dioxide RBCs don’t have mitochondria make ATP using

anaerobic respiration, so they don’t use the oxygen they are transporting

Shaped like biconcave disks doughnuts Outnumber white blood cells 1000 to 1

Erythrocytes

1 RBC can carry 1 billion molecules of oxygen Increase in number of RBCs is called polycythemia A decrease in the oxygen carrying ability of the blood is

called anemia Anemia can be caused by a decrease in the number of

RBCs or by a lower hemoglobin content in the RBCs Sickle-cell anemia – abnormal hemoglobin causes RBCs

to collapse and lose flexibility “sickle shape” These cells rupture easily and clog up small vessels Causes inhibited oxygen delivery, extreme pain, and

advantage for surviving malaria parasite http://www.youtube.com/watch?v=qRt2auWkcYg&feature

=related

Erythrocytes

White blood cells – WBCs The only “complete” cells in the blood contain nuclei and

organelles Defense against disease Able to slip in and out of blood vessels (diapedesis) Positive chemotaxis – WBCs can detect tissue damage,

infection, etc. by “sniffing out” the chemicals these events release

Leukocytosis – WBC count above average, indicates infection Leukopenia – low WBC count, usually caused by drugs Leukemia – “white blood,” bone marrow becomes cancerous

and starts making huge numbers of WBCs http://video.about.com/pediatrics/Acute-Lymphocytic-L

eukemia.htm

Leukocytes

Two major groups:◦ Granulocytes = contain granules, have lobed nuclei

Neutrophils = phagocytes, short-term or acute infections Eosinophils = kill parasitic worms, increase for allergies Basophils = contain histamine, cause inflammation and

attract other WBCs◦ Agranulocytes = lack visible granules, more

spherical nuclei Lymphocytes = B lymphocytes make antibodies, T

lymphocytes fight tumors and viruses (and reject grafts) and activate B lymphocytes

Monocytes = long-term “clean-up team,” chronic infections

Leukocytes

Leukocytes

Not exactly cells more like fragments of cells called megakaryocytes

Needed for clotting process when blood vessels rupture or are broken

Platelets

Occurs in red bone marrow All blood cells start out as a

hemocytoblast, a common type of stem cell

Becomes either lymphoid or myeloid stem cell

Lymphoid stem cell becomes lymphocyte Myeloid stem cell can become any other

kind of blood cell

Making Blood - Hematopoiesis

Making Blood - Hematopoiesis

RBCs are anucleate = they are unable to synthesize proteins, grow, or divide fall apart in 100 to 120 days

Lost cells are constantly replaced by the division of hemocytoblasts in red bone marrow

Erythropoietin = hormone that controls rate of RBC production, made by liver and kidneys

Colony stimulating factors (CSFs) and interleukins = stimulate WBC production

Thrombopoietin = stimulates platelet formation

Making Blood - Hematopoiesis

Making Blood - Hematopoiesis

Hemostasis = stoppage of blood flow When a blood vessel wall breaks, a series of

reactions is set in motion 1. Platelet plug forms – Platelets (which are

normally repelled by healthy endothelium) stick to the now-exposed “sticky” collagen fibers. They release chemicals that attract more platelets until a platelet plug (white thrombus) is formed.

2. Vascular spasms occur – Platelet plug starts to release serotonin, which causes blood vessel to spasm. This narrows the blood vessel, which reduces blood flow.

Blood Clotting

3. Coagulation events occur – ◦ A. Injured tissues release thromboplastin, which plays

important role in clotting.◦ B. PF3 = phospholipid that coats surfaces of platelets. It

interacts with thromboplastin, other clotting factors, and calcium ions to make an activator that triggers the clotting cascade.

◦ C. The prothrombin activator turns prothrombin to thrombin.

◦ D. Thrombin joins fibrinogen proteins into long, hairlike molecules called fibrin. The fibrin forms a “net” that traps RBCs and forms the clot. After an hour, the clot will start to retract, which squeezes out serum (plasma minus clotting proteins) and pulls the broken edges of the blood vessel closer together.

Blood Clotting

Entire process normally takes 3-6 minutes Applying sterile gauze can speed up the

process because the gauze provides a rough surface for platelets to stick to.

Applying pressure will rupture nearby cells, which increases the release of thromboplastin.

http://www.youtube.com/watch?v=9QVTHDM90io&feature=related

Blood Clotting

Two major problems: too much clotting or not enough

Too much clotting:◦ Thrombus – a clot that develops and persists in

an unbroken blood vessel◦ Embolus – a thrombus that breaks away from the

vessel and floats freely in the blood stream Not enough clotting:

◦ Thrombocytopenia – not enough platelets◦ Hemophilia – hereditary disorder resulting in lack

of any of the factors needed for clotting

Blood Clotting

Plasma membranes of RBCs contain antigens. Antigens = substance the body can recognize as

foreign stimulates release of antibodies to attack them

Antibodies recognize “native” antigens and “foreign” antigens

Antibodies will bind to foreign antigens and cause RBCs to clump together = agglutination

This can cause blocked vessels, kidney blockage and failure, fever, chills, nausea, vomiting, etc.

Over 30 RBC antigens, but the ABO and Rh antigens cause the most severe reactions

Blood Groups

Blood group

RBC antigens

Plasma antibodies

Can receive from

Can donate to

AB A, B None A, B, AB, O(universal recipient)

AB

B B Anti-A B, O B, AB

A A Anti-B A, O A, AB

O None Anti-A, Anti-B

O A, B, AB, O(universal donor)

Blood Groups

Rh factor – originally discovered in Rhesus monkeys

Rh+ = RBCs carry Rh antigen Rh- = RBCs do not carry Rh antigen Anti-Rh antibodies are only formed after Rh

antigens are detected in a Rh- person. If an Rh- woman is pregnant with a Rh+ baby,

she must take RhoGAM right after delivery or she will develop anti-Rh+ antibodies that will attack her next pregnancy.

Blood Groups

Blood Typing