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Blood

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The Composition and Functions of Blood

Functions of Blood1. Transport

• Carries oxygen to tissues• Carries carbon dioxide and other wastes away from tissues• Hormones

2. Defense• Defends body against pathogens• Removes dead and dying cells

3. Regulation• Body temperature• Water-salt balance• Body pH

Blood is a fluid tissue (“fluid connective tissue”)

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Composition of Blood• Includes liquid plasma + formed elements:

– Erythrocytes - red blood cells (RBCs)– Leukocytes - white blood cells (WBCs)– Platelets – involved in blood clotting– Plasma – non-living fluid

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Liquid portion of blood~ 92% is water~ 8% is composed various salts and organic molecules:

Plasma

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Erythrocytes, Leukocytes, PlateletsFormed Elements

• Skull• Ribs• Vertebrae• Pelvis• Ends of femurs and humerus’

distribution of red bone marrow (red)

Produced continuously in the red bone marrow of the:

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Erythrocytes (RBCs)

Hemoglobin binds with oxygen on red blood cells

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•Stem cells differentiate (turn into) into “committed cell” (to be a RBC)•Erythropoietin (EPO) stimulates production and maturation of RBCs

Production of Red Blood Cells

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Hemoglobin (Hb) Oxygen loading – occurs in lungsO2 diffuses from lung air sacs to blood, then through RBC to bind w/ HbWhen O2 binds to iron, Hb becomes oxyhemoglobin

changes 3-d shape → becomes ruby redWhen O2 detaches from iron, Hb becomes deoxyhemoglobin

color changes to deep dark red

Which one is Oxygenated? Deoxygenated?

Oxygen Loading StepsOxygen Loading:Step 1: Oxygen moves from the lung air sacs into the bloodStep 2: Oxygen moves through the red blood cells, to the hemoglobin that is on the red blood cellsStep 3: Oxygen binds to hemoglobin and then to iron. Step 4: Blood turn bright red and leaves the heart to go into the body - this is when the hemoglobin becomes oxyhemoglobin.

Unloading: Step 1: Blood arrives where oxygen is needed Step 2: Oxygen detaches from the iron and moves into the body Step 3: Blood is now considered deoxyhemoglobin and turns dark, deep, violet-ish red.

Oxy = Oxygen De= Without Hemo= Blood 9

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Erythrocyte Disorders

Anemia – blood has abnormally low oxygen-carrying capacity• Blood oxygen levels cannot support normal metabolism• Signs/symptoms include fatigue, paleness, shortness of breath, and chills

Polycythemia – excess RBCs that increase blood viscosity

• from cancer, decreased oxygen or excess EPO

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Differ from RBCs:• larger• have a nucleus• do not contain hemoglobin

White Blood Cells (Leukocytes)

• fighting infection• destroying dead or dying body cells• recognizing and killing cancerous cells

• derived from stem cells in the red bone marrow• able to leave the bloodstream

Functions include:

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Platelets

Function in clotting mechanism by forming a temporary plug that helps seal breaks in blood vessels

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Hemostasis

Series of reactions for stoppage of bleeding

Three steps:

1. Vascular spasms – immediate vasoconstriction in response to injury

2. Platelet plug formation

3. Coagulation (blood clotting)

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Hemophilia – inherited clotting disorders caused by lack of plateletsThrombus – stationary blood clotEmbolus – dislodged blood clotIf dislodged clot blocks a blood vessel:

Platelet Homeostasis

Pulmonary embolismCerebrovascular accident or stroke