Chapter 10: Blood

Blood

The only fluid tissue in the body Classified as a connective tissue

Notable: collagen & elastin absent from blood Dissolved fibrin proteins become evident during clotting

Components of blood Living cells

Formed elements – RBC & WBC Non-living matrix

Plasma

When Blood is centrifuged

Plasma rises to the top (55%) Erythrocytes sink to the bottom (45%)5

This is known as the hematocritNormal hematocrit:

47% +/- 5%: males42% +/-5%: females

Buffy coat contains leukocytes & platelets (<1%) Thin, whitish layer that is between erythrocytes &

plasma

Physical Characteristics of Blood

Sticky, opaque fluid – metallic taste

More dense than water, 5x more viscous

Colors: Oxygen rich blood – scarlet red (bright) Oxygen poor blood – dull red

pH is between 7.35 – 7.45

Blood temperature is always slightly higher than body temperature – around 100.4F

In a healthy man, blood volume is about 5-6 liters or about 6 quarts Women have less blood, about 3.5 – 5 liters

Blood makes up about 8% of body weight

Functions of Blood

All concerned with: substance distribution regulating blood levels of particularly substances bodily protection

Distribution: Oxygen to lungs Nutrients to digestive system Transporting metabolic wastes from elimination sites

(lungs, kidneys, liver) Hormones from glands to target organs

Functions of Blood

Regulation: Maintain appropriate body temperature by absorbing and

distributing heat through body, encouraging skin for heat loss

Maintain normal pH, blood holds an “alkaline” reserve to raise pH when necessary

Maintain adequate fluid volume in circulation Salts & blood protein – prevent excess fluid loss

Protection Prevents blood loss Prevents infection

Blood Plasma

Straw colored, sticky liquid

Composed of approximately 90% water

Includes over 100 dissolved substances: Nutrients Salts (electrolytes) Respiratory gases (CO2 & O2) Hormones Plasma proteins Waste products

Uric acid, creatinine, lactic acid, ammonium salts

Blood Plasma: Plasma Proteins

Most abundant solutes in plasma

Made mostly by the liver

Proteins include: Albumin: regulates osmotic pressure

The pressure that keeps water in the blood Essentially carries all proteins around the blood High albumin almost always caused by dehydration Low albumin can come from liver disease, kidney disease, & malnutrition

Globulins: Alpha, beta: transport proteins that bind to lipids, metal ions, fat-soluble vitamins Gamma: antibodies released during an immune response

Clotting proteins: help to stop blood loss when a blood vessel is injured Antibodies: help protect the body from pathogens (disease)

Blood Plasma

Acidosis: blood becomes too acidic Liver failure, kidney failure

Alkalosis: blood becomes too basic Main cause: hyperventilation –

resulting in a loss of CO2 Other causes: prolonged

vomiting, Cushing’s syndrome, severe dehydration

In each scenario, the respiratory system & kidneys help restore blood pH to normal

Formed Elements

Erythrocytes Red blood cells (RBCs)

Leukocytes

Lymphocytes Both are white

blood cells (WBCs)

Platelets

Cell fragments

Formed Elements Erythrocytes

AKA Red blood cells (RBCs) 4-6 million (per mm3) Developed in the bone marrow Salmon – colored biconcave discs Anucleate – CAN’T reproduce–produced in the bone marrow Literally, sacs of hemoglobin most organelles have been rejected

Structural protein called spectrin: spectrin net is deformable – allows erthyrocytes to change shape as necessary to move through blood vessels

Each erythrocyte has 250 million hemoglobin sacs Normal blood contains 12-18g per 100ml of blood

Functions: Transport oxygen to lung capillary beds Also transports small amounts of CO2 (about 20%)

Formed Elements Erythrocytes

Women have lower RBC count (4.32 -5, versus 5.1 – 5.8 mm3) As RBCs increase, blood viscosity increases, blood flow slows

Function: Respiratory gas transport Hemoglobin in RBC binds to oxygen

14-20 (g/100ml) – infants 13-18 – adult males 12 – 16 – adult females

Hemoglobin is inside RBCs to prevents the protein molecule from breaking apart and leaking through the bloodstream

Formed Elements Diseases of RBCs

Anemia Decrease in oxygen carrying ability

Sickle cell anemia (SCA) abnormally shaped hemoglobin Genetically caused Painful condition

Polycythemia excessive or abnormal increase in

the number of RBCs

Formed Elements

Formed Elements: Leukocytes Essential for body’s defense against pathogens

Complete cells with a nucleus & organelles

Can move in/out of blood vessels on their own (diapedesis)

Move with ameboid motion

Respond to chemicals released by damaged tissues

4,000 – 11,000 per mm3 of blood

Formed Elements: Types of Leukocytes Granulocytes

Possess lobed nuclei Will show granules in cytoplasm when stained

Include: neutrophils, eosinophils, & basophils

Agranulocytes Lack of visible granules Nuclei are spherical, oval or kidney – shaped Include: lymphocytes & monocytes

List of the WBCs from most to least abundant Neutrophils Never Lymphocytes Let Monocytes Monkeys Eosinophils Eat Basophils Bananas

Hemocytoblaststem cells

Secondary stem cells

Basophils

Eosinophils

NeutrophilsMonocytesLymphocytes

Erythrocytes

Platelets

Lymphoidstem cells

Myeloidstem cells

Formed Elements: Types of Leukocytes Neutrophils

Multilobed nuclei with small granules Acts as phagocyte at active site of

infection “first responder” to inflammatory site

(trauma) – tell tale sign of acute inflammation

Eosinophils Large brick red granules Shown in response to allergies, asthmatic

reactions or parasitic worms May play a role in defense against viruses

Formed Elements: Types of Leukocytes Basophils

Least common granulocytes Contain histamine granules Initiate inflammation Contain heparin

Prevent blood from clotting too quickly May regulate the behavior of T cells

Formed Elements: Types of Agranulocytes Lymphocytes

Nucleus fills most of the cell Plays an important role in the immune

system Types of Lymphocytes:

Killer Cells (Killer T Cells) Defend against tumors and virally infected

cells T Cells (Thymus Cells)

Many subsets of t cells All cell mediated immunity – pathogen

detection B Cells (Bone cells)

Secretion of antibodies Neutralize foreign objects like bacteria &

viruses

Formed Elements: Types of Agranulocytes Monocytes

Largest WBC in size ~50% found in the spleen Function as macrophages

Specific & non-specific defense Act in response to inflammatory situations

to get rid of pathogen/allergic causing antigen

Important in fighting chronic infection

WBC Abnormalities Leukocytosis

WBC count above 11,000 leukocytes/mm3

Generally indicates an infection But not indicative of any specific infection

It’s diagnostically similar to a fever

Leukopenia Abnormally low leukocyte level

Commonly caused by certain drugs such as corticosteroids and anticancer agents An important indicator of infection risk

Leukemia Bone marrow becomes cancerous, turns out excess WBC 4 types: ALL (acute lymphoblastic), CLL, AML (acute myelogenous), & CML

Can be acute or chronic Acute is more common in children, chronic in the elderly

Can be lymphoid or myeloid Lymphoid is more common in children, myeloid is rare in children

http://www.youtube.com/watch?v=tDTLC2swhlQ

Formed Elements: Platelets Aka thrombocytes

Small regular shaped cell fragments, derived from megakaryocytes (bone marrow cell)

Average lifespan of a platelet is 5 to 9 days

Needed for the clotting process

If platelets are too low, excessive bleeding can occur; if too high, wanted/unwanted clotting can occur.

Hematopoiesis Blood cell formation in red bone marrow

All blood cells (red & white) derive from a common stem cell (hemocytoblast)

Differentation: Lymphoid stem cells produce lymphocytes Myeloid stem cell produces all other formed elements

These stem cells are self-renewing I.e. – some never develop into RBCs or WBCs – they stay

stem cells so they can mitotically divide into more stem cells.

Erthyrocyte formation Erthyrocytes are unable to divide, grow & synthesize proteins

Wear out in 100 – 120 days

When they are no longer usable, they will be removed by phagocytosis by the liver or spleen

Lost cells are replaced by hemocytoblasts

Rate of RBC production is controlled by the hormone erthyropoietin

Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood

Homeostasis is maintained by negative feedback from blood oxygen levels

Reduced O2

levels in blood

Stimulus: DecreasedRBC count, decreasedavailability of O2 toblood, or increasedtissue demands for O2

IncreasedO2- carryingability of blood

Erythropoietinstimulates

Kidney releaseserythropoietinEnhanced

erythropoiesis

Red bonemarrow

MoreRBCs

Normal blood oxygen levels

Imbalance

Imbalance

Formation of WBCs and platelets

Controlled by hormones Colony stimulating factors (CSFs) and interleukins prompt bone

marrow to generate leukocytes Thrombopoietin stimulates production of platelets

Hemostasis

Stoppage of bleeding resulting from a break in a blood vessel

Hemostasis involves three phases Vascular spasms

Vasoconstriction causes the blood vessel to spasmSpasms narrow the blood vessel and decreases

overall blood loss

Hemostasis Platelet plug formation

Collagen fibers that make up the blood vessel become exposed by the break

Platelets become sticky & cling to the collagen fibers Those platelets release chemicals (PF3) to attract more platelets

The platelets pile up to form a platelet plug

Coagulation (blood clotting) Injured tissues release TF (tissue factor) PF3 interacts with TF, clotting factors & calcium ions to initiate the

clotting cascade Prothrombin gets converted to thrombin by prothrombin activator. Thrombin joins fibrinogen proteins into hair-like molecules of insoluble

fibrin Fibrin forms a meshwork (the basis for a clot)

Platelets release chemicalsthat attract more platelets tothe site and make nearbyplatelets sticky

PF3 fromplatelets Calcium

and otherclottingfactorsin bloodplasma

Formation ofprothrombinactivator

Prothrombin

Fibrinogen(soluble)

Fibrin(insoluble)

Thrombin

Tissue factorin damagedtissue

Phases ofcoagulation(clottingcascade)

+

Hemostasis

Blood usually clots within 3 to 6 minutes

The clot remains as endothelium regenerates

The clot is broken down after tissue repair

Undesirable Clotting Thrombus

A clot in an unbroken blood vessel – normal during injury but should be disposed of once the risk of excessive bleeding has past.

Can be deadly in areas like the heart More likely to occur when there are problems in the heart (arrhythmia,

heart valve replacement and/or recent heart attack

Embolus A thrombus that breaks away and floats freely in the bloodstream

In general, an embolus is ANY detached, itinerant intravascular mass – they can be solid, liquid or gas

Can later clog vessels in critical areas such as the brain

Bleeding Disorders Thrombocytopenia

Platelet deficiency = below 50,000 per microliter

Normal platelet counts are between 150,000 – 450,000 per microliter of blood (that’s a lot)

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

Symptoms include frequent bruising, purpura, & petechiae

Bleeding Disorders Haemophilia

Hereditary bleeding disorder Normal clotting factors are missing

When bleeding occurs, a scab does form, but it is temporary The clotting factor prevents the fibrin

from reattaching and healing the blood vessel

Blood Typing & Transfusions

Large losses of blood have serious consequences Loss of 15–30% causes weakness Loss of over 30% causes shock, which can be fatal

Transfusions are the only way to replace blood quickly

Transfused blood must be of the same blood group

Blood is tested for a large number of diseases before giving to the patient who needs blood Tested for:

All forms of HIV, All forms of hepatitis, syphillis, CMV, and West Nile virus – just to name a few Complications:

Hemolytic reactions: you have antibodies again the donor’s RBCs – symptoms include fever, chills, increased heart rate, shortness of breath, rapid drop in blood pressure. Transfusion must be stopped immediately before kidney damage occurs

Allergic reactions: while blood banks look at the complete chemical make up of donor blood, if a patient is unaware of allergies and these chemicals are in blood – an allergic reaction can occur If severe, Usually easily fixed by dosing epinephrine to stop anaphylaxis

Human Blood Groups

Blood contains genetically determined proteins

Antigens (a substance the body recognizes as foreign) may be attacked by the immune system

Antibodies are the “recognizers”

Blood is “typed” by using antibodies that will cause blood with certain proteins to clump (agglutination)

There are over 30 common red blood cell antigens

The most vigorous transfusion reactions are caused by ABO and Rh blood group antigens

ABO Blood Groups

Based on the presence or absence of two antigens Type A: The presence of

antigen A, has anti-B antibodies

Type B: The presence of antigen B, has anti-A antibodies

Type O: lacks the presence of any antigens, has anti-A & anti-B antibodies

Type AB: the presence of antigen A & antigen B, has no antibodies

ABO Blood Groups

Blood type AB can receive A, B, AB, and O blood Universal recipient

Blood type B can receive B and O blood

Blood type A can receive A and O blood

Blood type O can receive O blood Universal donor

Rh Blood Groups

Named because of the presence or absence of one of eight Rh antigens (agglutinogen D) that was originally defined in Rhesus monkeys

Most Americans are Rh+ (Rh positive)

Problems can occur in mixing Rh+ blood into a body with Rh– (Rh negative) blood

Dangers of an Rh mismatch

Danger occurs only when the mother is Rh– and the father is Rh+, and the child inherits the Rh+ factor

RhoGAM shot can prevent buildup of anti-Rh+ antibodies in mother’s blood

The mismatch of an Rh– mother carrying an Rh+ baby can cause problems for the unborn child The first pregnancy usually proceeds without problems The immune system is sensitized after the first pregnancy In a second pregnancy, the mother’s immune system produces

antibodies to attack the Rh+ blood (hemolytic disease of the newborn)

Blood typing

Blood samples are mixed with anti-A and anti-B serum

Agglutination or no agglutination leads to determining blood type

Typing for ABO and Rh factors is done in the same manner

Cross matching—testing for agglutination of donor RBCs by the recipient’s serum, and vice versa

Developmental Aspects of Blood

Sites of blood cell formation The fetal liver and spleen are early sites of blood cell formation Bone marrow takes over hematopoiesis by the seventh month

Fetal hemoglobin differs from hemoglobin produced after birth It can carry much more oxygen than adult hemoglobin By 12 weeks of life, fetal hemoglobin is replaced by adult hemoglobin

Physiologic jaundice results in infants in which the liver cannot rid the body of hemoglobin breakdown products fast enough