BloodChapter 14

Blood

• Connective tissue with a fluid matrix

• Three main functions:– Transportation– Regulation– Protection

Physical Characteristics of Blood• Heavier, thicker, and 3-4 X more viscous

than water

• 38o C (100.4oF)

• pH : 7.35 – 7.45

• 8% of body weight

• 4-6 liters in an adult

• Varies with electrolyte concentration and amount of adipose tissue

8% of body weight

70 kg person

Total blood weight =

0.08 X 70kg = 5.6 kg

One kilogram of blood ≈ 1 liter

Total blood volume = 5.6 liters

Components of Blood

• Plasma – 55 %• Formed elements – cells and cell

fragments – 45%• Hematocrit (HCT) or Packed Cell Volume

(PCV)• See:

– Plasma– Buffy coat (< 1%)– Red cells - erythrocytes

Formation of blood cells

Before birth blood is formed by the yolk sac, liver, spleen, thymus gland, lymph nodes and red bone marrow.

After birth only by red bone marrow

Stem cells are hemocytoblasts

Process is hematopoiesis

Colony stimulating factors

ErthrocytesBiconcave discs without nuclei

1/3 hemoglobin by volume

Hemoglobin – 4 peptide chains and an iron containing pigment called heme

The iron binds reversibly with oxygen

oxyhemoglobin deoxyhemoglobin

Cyanotic – skin and mucous membranes

appear blue

Also transports 23 % of CO2

bound to globin as carbaminohemoglobin

CO – carbon monoxide binds more tightly to hemoglobin than oxygen

Males = 5.4 million RBCs per cubic mm

Females and children = 4.8 million/ cubic mm

People at high altitudes = 8 million/cubic mm

RBCs live about 120 days

Iron is removed from heme, combines with transferrin and is taken to bone marrow

80% of the iron is stored in the liver in an iron-protein complex called ferritin

The rest of the heme is a greenish pigment called biliverdin which is broken down to a yellow-orange substance called bilirubin

Jaudice

Anemia is the inability of the blood to carry sufficient oxygen to the body.

low #’s of RBCslack of hemoglobin

Pernicious anemia is a lack of RBCs due to lack of vitamin B12

Folic acid also needed for DNA synthesis

Iron deficiency anemia

Sickle cell anemia

Polycythemia is an excess of RBCs – blood gets too thick to flow

LeukocytesGranular leukocytes (granulocytes)

neutrophils

eosinophils

basophils

Agranular leukocytes (agranulocytes)

Lymphocytes

Monocytes

Eosinophils

• Granules stain red with acidic dyes

• Nuclei us. have 2 lobes

• Combat effect of histamine in allergic reactions

• Combat parasitic worms

• 1-3% of leukocytes

Basophils

•Have granules that stain blue with basic dyes

•Release heparin, and histamine

•Increase in allergic reactions that intensify the inflammatory response

•Less than 1% of leukocytes

Neutrophils

•Granules stain pale purple in a combination of acidic and basic dye

•Older cells have many lobed nuclei – gives the name polymorphonuclear leukocytes (PMNs)

•Younger neutrophils are called bands

•Phagocytes

•54 -62 % of the leukocytes

Lymphocytes•May be small or large

•Nuclei stain darkly, very little cytoplasm

•Only 2% of lymphocytes are in blood

•B lymphocytes make antibodies

•T lymphocytes attack invaders directly

•Long lived

•25-33% of leukocytes

Monocytes•Largest leukocyte

•Nuclei horseshoe-shaped

•Cytoplasm blue-gray and foamy

•When leave blood and enter tissues become transformed into macrophages

•3 - 9 % of leukocytes

Normal blood contains 5,000 -10,000/mm3

An increase in the number of wbcs is leukocytosis

A deficiency in wbcs is leukopenia

Differential white blood cell count is useful in diagnosis of disease

Major histocompatibility (MHC) antigens used in tissue typing

Function of leukocytes

Protect against infection

phagocytosis, antibodies, direct attack

Diapedesis

Damaged tissue releases chemicals that attract leukocytes – positive chemotaxis

Platelets, or thrombocytes, are cell fragments

•Formed from megakaryocytes

•130,000 – 360,000/mm3

•Involved in blood clotting

•Release serotonin which contracts smooth muscle in walls of blood vessels – reducing blood flow – and blood loss

Plasma

• 92 % water

• 8% solutes – ions, nutrients, enzymes, gases, wastes, hormones, but mostly proteins

•These proteins are mostly made by the liver

Serum

Plasma without the clotting factors

Still contains :

ions, nutrients, enzymes, gases, wastes, hormones, and some proteins – including antibodies

Hemostasis

• Means stoppage of bleeding

1. Vascular spasm

2. Platelet plug formation

3. Blood coagulation - clotting

Vasospasm

• Smooth muscle in vessel wall contracts

• Decreased diameter of vessel decreases blood flow

• Lasts several minutes to several hours

Platelet plug formation

1. Platelets contact damaged vessel –platelet adhesion

2. Platelets become activated, dump granules – platelet release reaction

3. Platelets become sticky and accumulate – platelet aggregation

Blood coagulation

• Clotting in an unbroken vessel – thrombosis

• Clot is a thrombus

• If it breaks free and travels in the blood stream it is an embolus

• If it lodges elsewhere in the body, it is an embolism

Blood clotting can be divided into 3 stages:

1. formation of prothrombinase

2.Conversion of prothrombin to thrombin

3.Conversion of soluble fibrinogen to insoluble fibrin

Stage 1 formation of prothrombinase (prothrombin activator) can be started one of two ways:

Extrinsic pathway (clotting mechanism):tissue factor leaks into the blood from

outside the vessels

Intrinsic pathway –more complex, slower, by roughened endothelium of exposure to foreign substances – Hageman factor

Stage 2 – Prothrombinase + calcium

Convert prothrombin to thrombin

Stage 3 – Thrombin + calcium

convert fibrinogen to fibrin

Threads of fibrin form a net and trap blood cells, forming a clot.

Clot retraction

Platelet-derived growth factor → repair

Hemophila

• Due to a deficiency of one of the clotting factors

• Hereditary trait

Role of vitamin K

• Normal clotting requires vitamin K, but it is not a clotting factor

• It is required for the synthesis of four of the clotting factors by the liver.

• Normally made by bacteria in large intestine

• Sometimes given before surgery

Fibrolytic system

• Plasminogen, an inactive enzyme, is incorporated into a clot

• Plasminogen can be activated to plasmin, (or fibrinolysin) which digests fibrin and inactivates other clotting factors

Thrombolytic agents

• Streptokinase

• Tissue plasminogen activator – t-PA

Anticoagulants

• Prostaglandins

• Heparin

• Warfarin or coumadin – antagonists to vitamin K

• Chelating agents tie up calcium

• Aspirin inhibits vasoconstriction and platelet aggregation

Blood Groups and Blood Types• Erythrocytes have surface antigens, called

isoantigens or agglutinogens• Most common are the ABO and Rh groups• A and B are isoantigens, O is absence of

antigen• Antibodies activate complement which

causes hemolysis• Typing outside the body uses

agglutination, NOT clotting !

Persons with type A blood make antibodies against B

Persons with type B blood make antibodies against A

Persons with type O blood make antibodies against A and B

Persons with type AB do not make antibodies.

Rh factor

• First discovered in the rhesus monkey

• Either have the antigen = positive

• Or don’t have the antigen = negative

• Do not automatically make antibodies – must first encounter the antigen

• Hemolytic disease of the newborn – or- erythroblastosis fetalis

• Give RhoGAM – anti Rh antibodies

Remember:

Rh factor is only a problem if the mother is negative and the father is positive.