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Blood also helps to maintain the chemical balance of the body. Proteins and other compounds in blood act as buffers, which thereby help to regulate the pH of body tissues. Blood also helps to regulate the water content of body cells.

Composition of blood

You have probably had blood drawn from a superficial vein in your arm, which was then sent to a lab for analysis. Some of the most common blood tests—for instance, those measuring lipid or glucose levels in plasma—determine which substances are present within blood and in what quantities. Other blood tests check for the composition of the blood itself, including the quantities and types of formed elements.

One such test, called a hematocrit    , measures the percentage of RBCs, clinically known as erythrocytes, in a blood sample. It is performed by spinning the blood sample in a specialized centrifuge, a process that causes the heavier elements suspended within the blood sample to separate from the lightweight, liquid plasma ( [link] ). Because the heaviest elements in blood are the erythrocytes, these settle at the very bottom of the hematocrit tube. Located above the erythrocytes is a pale, thin layer composed of the remaining formed elements of blood. These are the WBCs, clinically known as leukocytes, and the platelets, cell fragments also called thrombocytes. This layer is referred to as the buffy coat    because of its color; it normally constitutes less than 1 percent of a blood sample. Above the buffy coat is the blood plasma, normally a pale, straw-colored fluid, which constitutes the remainder of the sample.

In normal blood, about 45 percent of a sample is erythrocytes. The hematocrit of any one sample can vary significantly, however, about 36–50 percent, according to gender and other factors. Normal hematocrit values for females range from 37 to 47, with a mean value of 41; for males, hematocrit ranges from 42 to 52, with a mean of 47. The percentage of other formed elements, the WBCs and platelets, is extremely small so it is not normally considered with the hematocrit. So the mean plasma percentage is the percent of blood that is not erythrocytes: for females, it is approximately 59 (or 100 minus 41), and for males, it is approximately 53 (or 100 minus 47).

Composition of blood

This figure shows three test tubes with a red and yellow liquid in them. The left panel shows normal blood, the center panel shows anemic blood and the right panel shows polycythemic blood.
The cellular elements of blood include a vast number of erythrocytes and comparatively fewer leukocytes and platelets. Plasma is the fluid in which the formed elements are suspended. A sample of blood spun in a centrifuge reveals that plasma is the lightest component. It floats at the top of the tube separated from the heaviest elements, the erythrocytes, by a buffy coat of leukocytes and platelets. Hematocrit is the percentage of the total sample that is comprised of erythrocytes. Depressed and elevated hematocrit levels are shown for comparison.

Characteristics of blood

When you think about blood, the first characteristic that probably comes to mind is its color. Blood that has just taken up oxygen in the lungs is bright red, and blood that has released oxygen in the tissues is a more dusky (i.e bluish) red. This is because hemoglobin is a pigment that changes color, depending upon the degree of oxygen saturation.

Questions & Answers

what is the source of the homologous chromosomes and the importance of its event?
Tani Reply
chemical, cellular, tissue, organ, organ system, organisms
Saleema Reply
chemical, tissue, cellular, organ, organism, organ system
Saleema
yes, both parts are apart of the reproductive and endocrine system because they function in both
Saleema
du antigen
gambo
what is antigenic
gambo
how many bones are there in a human
Tih Reply
206
Shivani
206 when they fused together
gambo
206 bones
Kate
206bones
R0se
206
Mahmmad
define ornithology
Aniowo
ornithology is the study of birds in every aspect.
Hemamalene
chemical which makes a person to lose appetite
milton Reply
name the matrix from which bone is made?
Vaibhav Reply
hydroxyapatite
Tani
whats the nuclear pore ?
Tani Reply
tell me about the nuclear pore or nuclear membrane I don't quite understanding
Tani
The nuclear pore is a protein-lined channel in the nuclear membrane that regulates the transportation of molecules between thenucleus and the cytoplasm.
Jack
The nuclear pore is a protein lined channel in the nuclear membrane (nuclear envelope) that regulates the transportation of molecules between the nucleus and the cytoplasm.
Jack
Thank you...
Tani
what is cell?
Shashi Reply
cell is a small building block that make everything in the body. Other words known as the smallest unit of life
Cheryl
cell is the basics unit of life, in words it's enablement of life process
Dumbari
what is diffusion
kambani
diffusion is the net movement of a particles from an area of high concentration to an area of low concentration down a concentration gradient
linadora
What is the meaning of the word cell?
hafsa Reply
unit
Samiullah
who discovered cell and in what year.
Jonathan
Robert hook discovered cell in 1665.
Alisohai
what is biology
gambo
bioLoGy is tHe bRanCH oF SCIENce, anD iTs dEals witH tHe stUdy oF liFe ..
Alisohai
what happened when the hand accidentally touches a hot abject
Tumbu Reply
quickly removes its hand
hafsa
a stimuli is sent to the central nervous system by neurons which in turn send back a response which makes that person to quickly remove his hand from the hot object.
Ofang
what is cell
Ernest Reply
cell can be defined as the smallest unit of life
alhassan
what is a hormone
Michael Reply
hormones are the body's chemical messengers and are part of the endocrine system,.
Nisa
hormone are the chemical messanger that are produce by ductless gland to act on a target organ.
Luqman
why are the pictures showing
Anasili Reply
I don't get your question well
Prophet
The Cowper's gland, prostate gland and the seminar vesicle are involved in the secretion of seminal fluid which consist of enzyme,protein in form of amino acid and a very important hormone called what?
ANGEL Reply
testosterone
Prophet
what is reflex action
vanya
what is the specialize functions of the organs
Donieta Reply
what organs?
Maureen
what is the faction of photo receptors in the eye
Mutangana Reply
transduction of light to nervous impulses occurr it is located in the retina
Maureen

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Source:  OpenStax, Human biology. OpenStax CNX. Dec 01, 2015 Download for free at http://legacy.cnx.org/content/col11903/1.3
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