Book : Human Biology
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Posted by: CHELSEA
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Writer CHELSEA

Blood

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Introduction

The primary function of blood is to supply nutrients and constitutional elements to tissues and to remove waste products. Blood also enables cells and different substances to be transported between tissues and organs. Problems with blood composition or circulation can lead to downstream tissue malfunction. Blood is also involved in maintaining homeostasis by acting as a medium for transferring heat to the skin and by acting as a buffer system for bodily pH.

Blood Composition

Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). Anatomically, blood is considered a connective tissue, due to its origin in the bones and its function. Blood is the means and transport system of the body used in carrying elements (e.g. nutrition, waste, heat) from one location in the body to another, by way of blood vessels. Blood is made of two parts: 1. Plasma which makes up 45-55% of blood volume. 2. Formed cellular elements (red and white blood cells, and platelets) which combine to make the remaining blood volume.

Red Blood Cells (RBC) Introduction


Red blood cell (erythrocyte) also known as "RBC's". RBC’s are formed in the myeloid tissue or most commonly known as red bone marrow, although when the body is under severe conditions the yellow bone marrow, which is also in the fatty places of the marrow in the body will also make RBC’s. The formation of RBC’s is called erythropoiesis

Shape

RBC'S have a shape of a disk that appears to be “caved in” or almost flattened in the middle; this is called bi- concave. This bi-concave shape allows the RBC to carry oxygen and pass through even the smallest capillaries in the lungs. This shape also allows RBCs to stack like dinner plates and bend as they flow smoothly through the narrow blood vessels in the body.

Main Component

The main component of the RBC is hemoglobin protein which is about 25 million per cell. The word hemoglobin comes from hemo meaning blood and globin meaning protein. This is the protein substance of four different proteins: polypeptide globin chains that contain anywhere from 141 to 146 amino acids. Hemoglobin also is responsible for the cell’s ability to transport oxygen and carbon dioxide. This hemoglobin + iron + oxygen interact with each other forming the RBC's bright red color. You can call this interaction by product oxyhemoglobin. Carbon Monoxide forms with hemoglobin faster that oxygen, and stays formed for several hours making hemoglobin unavailable for oxygen transport right away. Also a red blood cell contains about 200 million hemoglobin molecules. If all this hemoglobin was in the plasma rather than inside the cells, your blood would be so "thick" that the heart would have a difficult time pumping it through. The thickness of blood is called viscosity. The greater the viscosity of blood, the more friction there is and more pressure is needed to force blood through.

Functions

The main function is the transportation of oxygen throughout the body and the ability of the blood to carry out carbon dioxide which is called carbamino – hemoglobin. Maintaining the balance of blood is important. The balance can be measured by the acid and base levels in the blood. This is called pH. Normal pH of blood ranges between 7.35-7.45; this normal blood is called Alkaline then water). A drop in pH is called Acidic. This condition is also called Acidosis. A jump in pH higher then 7.45 is called "Alkalis". To maintain the homeostasis (or balance,) the blood has tiny molecules within the RBC that help prevent drops or increases from happening.

White Blood Cells (WBC) Shape


White blood cells are different from red cells in the fact that they are usually larger in size 10- 14 micrometers in diameter. White blood cells do not contain hemoglobin which in turn makes them translucent. Many times in diagrams or pictures white blood cells are represented in a blue color, mainly because blue is the color of the stain used to see the cells. White blood cells also have nucleii, that are some what segmented and are surrounded by electrons inside the membrane.

Functions

White blood cells (leukocytes) are also known as "WBC's". White blood cells are made in the bone marrow but they also divide in the blood and lymphatic systems. They are commonly amoeboid (cells that move or feed by means of temporary projections, called pseudopods (false feet), and escape the circulatory system through the capillary beds. The different types of WBC's are Basophils, Eosinophils, Eeutrophils, Monocytes, B- and T-cell lymphocytes. Neutrophils, Eosinophils, and Basophils are all granular leukocytes. Lymphocytes and Monocytes are agranular leukocytes. Basophils store and synthesize histamine which is important in allergic reactions. They enter the tissues and become "mass cells" which help blood flow to injured tissues by the release of histamine. Eosinophils are chemotaxic and kill parasites. Neutrophils are the first to act when there is an infection and are also the most abundant white blood cells. Neutrophils fight bacteria and viruses by phagocytosis which mean they engulf pathogens that may cause infection. The life span of a of Neutrophil is only about 12-48 hours. Monocytes are the biggest of the white blood cells and are responsible for rallying the cells to defend the body. Monocytes carry out phagocytosis and are also called macrophages. Lymphocytes help with our immune response. There are two Lymphocytes: the Band T- cell. B-Lymphocytes produce antibodies that find and mark pathogens for destruction. TLymphocytes kill anything that they deem abnormal to the body


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