Blood Physiology

This article or area is currently under construction and may only be partially complete. Please come back soon to see the finished work! (5/07/2020)

Original Editor - User Name

Top Contributors - Lucinda hampton, Mandy Roscher, Kim Jackson, Tony Lowe, Tarina van der Stockt, Vidya Acharya, Rucha Gadgil, Jess Bell, Olajumoke Ogunleye and Stacy Schiurring  

Introduction

Blood is a fluid connective tissue critical for:

• Transportation of nutrients, gases, and wastes throughout the body;
• Defence for the body against infection and other threats eg seek out and destroy internal threats, such as cells with mutated DNA that could multiply to become cancerous.
• Homeostatic regulation of pH, temperature, and other internal conditions.

Blood is composed of:

1. Formed elements—erythrocytes, leukocytes, and cell fragments called platelets
2. Fluid extracellular matrix called plasma. More than 90 percent of plasma is water, the remainder is mostly plasma proteins (mainly albumin, globulins, and fibrinogen) and other dissolved solutes such as glucose, lipids, electrolytes, and dissolved gases.

Because of the formed elements and the plasma proteins and other solutes, blood is sticky and more viscous than water. It is also slightly alkaline, and its temperature is slightly higher than normal body temperature.

Formed Elements

Erythrocytes (red blood cells) - function primarily to ferry oxygen in blood to all cells of the body.

Salient Points

• Anucleate. RBCs differ from other blood cells because they are anucleate, that is, they lack a nucleus; they also contain a very few organelles.
• Hemoglobin (an iron bearing protein), transports the bulk of oxygen that is carried in the blood.
• Microscopic appearance - Erythrocytes are small, flexible cells shaped like biconcave discs- flattened discs with depressed centers on both sides; they look like miniature doughnuts when viewed with a microscope.
• Number of RBCs - normally about 5 million cells per cubic millimeter of blood; RBCs outnumber WBCs by approx. 1000 to 1, major factor contributing to blood viscosity.
• Normal blood - Clinically, normal blood contains 12-18 grams of hemoglobin per 100 milliliters (ml); the hemoglobin content is slightly higher in men (13-18 g/dl) than in women (12-16 g/dl).

Leukocytes

Salient Points

• Far less numerous than red blood cells and are crucial to body defense against disease.
• Number of WBCs. On average, there are 4,000 to 11,000 WBC/mm3 , and they account for less than 1 percent of total body volume.
• Body defense - form a protective, movable army that helps defend the body against damage by bacteria, viruses, parasites, and tumor cells.
• Diapedesis - a name for the process were white blood cells are able to slip into and out of the blood vessels.
• Positive chemotaxis - WBCs can locate areas of tissue damage and infection in the body by responding to certain chemicals that diffuse from the damaged cells (this capability is called positive chemotaxis).
• Ameboid motion. Once they have “caught the scent”, the WBCs move through the tissue spaces by ameboid motion (they form flowing cytoplasmic extensions that help move them along).
• Leukocytosis. A total WBC count above 11, 000 cells/mm3 is referred to as leukocytosis.
• Leukopenia. The opposite condition, leukopenia, is an abnormally low WBC count.

Many types of WBC's

• Granulocytes.
• Neutrophils.
• Eosinophils.
• Basophils.
• Agranulocytes. .
• Lymphocytes.
• Monocytes.
• Platelets. Platelets are not cells in the strict sense; they are fragments of bizarre multinucleate cells called megakaryocytes, which pinch off thousands of anucleate platelet “pieces” that quickly seal themselves off from surrounding fluids; platelets are needed for the clotting process that occurs in plasma when blood vessels are ruptured or broken.

Resources

• bulleted list
• x

or

1. numbered list
2. x