Blood

Chapter 12

Bio160

Blood Composition

• Red blood cells

• White blood cells

• Platelets

• Plasma

Red Blood Cells

Biconcave disks that contain oxygen-carrying hemoglobin

• Red blood cells (Erythrocytes)

When oxygen combines with hemoglobin bright red oxyhemoglobin results whereas deoxygenated blood (deoxyhemoglobin) is darker.

Red blood cells discard their nuclei during development and so cannot reproduce or produce proteins.

Red Blood Cells

The number of red blood cells is a measure of the blood's oxygen-carrying capacity.

Red Blood Cells

In the embryo and fetus, red blood cell production occurs in the yolk sac, liver, and spleen; after birth, it occurs in the red bone marrow.

• Red blood cell production

The average life span of a red blood cell is 120 days.

The total number of red blood cells remains relatively constant due to a negative feedback mechanism utilizing the hormone erythropoietin, which is released from the kidneys and liver in response to the detection of low oxygen levels.

Red Blood Cells

Vitamins B12, folic acid and iron are needed for red blood cell production

Red Blood Cells

A deficiency in red blood cells or quantity of hemoglobin results in anemia.

Red Blood Cells

With age, red blood cells become increasingly fragile and are damaged by passing through narrow capillaries.

• Red blood cell destruction

Macrophages in the liver and spleen phagocytize damaged red blood cells.

Hemoglobin from the decomposed red blood cells is converted into heme and globin.

Red Blood Cells

Heme is decomposed into iron, which is stored or recycled, and biliverdin and bilirubin, which are excreted in bile.

White Blood Cells

Defend the body from disease.

• White blood cells (Leukocytes)

They are formed from hemocytoblasts.

Leukocytes can squeeze between cells lining walls of blood vessels by diapedesis and attack bacteria and debris.

White Blood Cells

Have red-staining fine cytoplasmic granules and a multilobed nucleus; they comprise 54-62% of leukocytes.

• Neutrophils

They are phagocytic.

White Blood Cells

Have coarse granules that stain deep red, a bilobed nucleus, and make up only 1-3% of circulating leukocytes.

• Eosinophils

Eosinophils moderate allergic reactions as well as defend against parasitic infections.

White Blood Cells

Have fewer granules that stain blue; they account for fewer than 1% of leukocytes.

• Basophils

Basophils migrate to damaged tissues and release histamine to promote inflammation and heparin to inhibit blood clotting.

White Blood Cells

The largest blood cells, have variably shaped nuclei, and make up 3-9% of circulating leukocytes.

• Monocytes

They are phagocytic, engulfing large particles.

White Blood Cells

Long-lived, have a large, round nucleus, and account for 25-33% of circulating leukocytes.

• Lymphocytes

The major players in specific immune reactions and some produce antibodies.

Platelets

Blood platelets are fragments of megakaryocytes.

• Blood platelets

Platelets help repair damaged blood vessels by adhering to their broken edges.

Blood Plasma• Blood Plasma

Plasma is the clear, straw-colored fluid portion of the blood.

– Plasma is mostly water but contains a variety of substances.

– Plasma functions to transport nutrients and gases, regulate fluid and electrolyte balance, and maintain a favorable pH.

Blood PlasmaPlasma proteins

– The albumins help maintain the osmotic pressure of the blood and account for 60% of the plasma proteins.

– The globulins, comprising 36% of the plasma proteins, are designated as alpha, beta, and gamma globulins.

Action Potentials

Alpha and beta globulins function in transporting lipids and fat-soluble vitamins.

Gamma globulins are a type of antibody.

– Fibrinogen (4%) plays a primary role in blood coagulation.

Blood PlasmaGases and nutrients

– The most important blood gases are oxygen and carbon dioxide.

– The plasma nutrients include amino acids, monosaccharides, nucleotides, and lipids.

Blood PlasmaNonprotein Nitrogenous Substances

– Nonprotein nitrogenous substances generally include amino acids, urea, and uric acid.

Blood PlasmaPlasma Electrolytes

– They include sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, and sulfate ions.

– Some of these ions are important in maintaining osmotic pressure and pH of the plasma.

Hemostasis• Hemostasis

Hemostasis refers to the stoppage of bleeding.

– Blood vessel spasm - muscles in vessel wall contract

– Platelet plug formation - platelets stick to the exposed edges of damaged blood vessels, forming a net with spiny processes protruding from their membranes.

Hemostasis

– Blood coagulation – complex series of steps that leads to blood clot formation by conversion of fibrinogen into net-like fibrin, which catches blood cells before they can leave the body.