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By the end of this section, you will be able to:
  • List the basic components of the blood
  • Compare red and white blood cells
  • Describe blood plasma and serum

Hemoglobin is responsible for distributing oxygen, and to a lesser extent, carbon dioxide, throughout the circulatory systems of humans, vertebrates, and many invertebrates. The blood is more than the proteins, though. Blood is actually a term used to describe the liquid that moves through the vessels and includes plasma    (the liquid portion, which contains water, proteins, salts, lipids, and glucose) and the cells (red and white cells) and cell fragments called platelets . Blood plasma is actually the dominant component of blood and contains the water, proteins, electrolytes, lipids, and glucose. The cells are responsible for carrying the gases (red cells) and immune the response (white). The platelets are responsible for blood clotting. Interstitial fluid that surrounds cells is separate from the blood, but in hemolymph, they are combined. In humans, cellular components make up approximately 45 percent of the blood and the liquid plasma 55 percent. Blood is 20 percent of a person’s extracellular fluid and eight percent of weight.

The role of blood in the body

Blood, like the human blood illustrated in [link] is important for regulation of the body’s systems and homeostasis. Blood helps maintain homeostasis by stabilizing pH, temperature, osmotic pressure, and by eliminating excess heat. Blood supports growth by distributing nutrients and hormones, and by removing waste. Blood plays a protective role by transporting clotting factors and platelets to prevent blood loss and transporting the disease-fighting agents or white blood cells to sites of infection.

Illustration shows different types of blood cells and cellular components. Red blood cells are disc-shaped and puckered in the middle. Platelets are long and thin, and about half the length red blood cells. Neutrophils, monocytes, lymphocytes, eosinophils, and basophils are about twice the diameter of red blood cells and spherical. Monocytes and eosinophils have U-shaped nuclei. Eosinophils contain granules, but monocytes do not. Basophils and neutrophils both have irregularly shaped, multi-lobed nuclei and granules.
The cells and cellular components of human blood are shown. Red blood cells deliver oxygen to the cells and remove carbon dioxide. White blood cells—including neutrophils, monocytes, lymphocytes, eosinophils, and basophils—are involved in the immune response. Platelets form clots that prevent blood loss after injury.

Red blood cells

Red blood cells , or erythrocytes (erythro- = “red”; -cyte = “cell”), are specialized cells that circulate through the body delivering oxygen to cells; they are formed from stem cells in the bone marrow. In mammals, red blood cells are small biconcave cells that at maturity do not contain a nucleus or mitochondria and are only 7–8 µm in size. In birds and non-avian reptiles, a nucleus is still maintained in red blood cells.

The red coloring of blood comes from the iron-containing protein hemoglobin, illustrated in [link] a . The principal job of this protein is to carry oxygen, but it also transports carbon dioxide as well. Hemoglobin is packed into red blood cells at a rate of about 250 million molecules of hemoglobin per cell. Each hemoglobin molecule binds four oxygen molecules so that each red blood cell carries one billion molecules of oxygen. There are approximately 25 trillion red blood cells in the five liters of blood in the human body, which could carry up to 25 sextillion (25 × 10 21 ) molecules of oxygen in the body at any time. In mammals, the lack of organelles in erythrocytes leaves more room for the hemoglobin molecules, and the lack of mitochondria also prevents use of the oxygen for metabolic respiration. Only mammals have anucleated red blood cells, and some mammals (camels, for instance) even have nucleated red blood cells. The advantage of nucleated red blood cells is that these cells can undergo mitosis. Anucleated red blood cells metabolize anaerobically (without oxygen), making use of a primitive metabolic pathway to produce ATP and increase the efficiency of oxygen transport.

Questions & Answers

hetreothalism in fungi
Lekhram Reply
there are 3 trimester in human pregnancy
I don't know answer of this question can u help me
what is a cell
Fatima Reply
A cell is functional and structural unit of life.
what is genetic
Janet Reply
I join
what are the branchas of biology
Prisca Reply
zoology, ecology
genetics, microbiology,botany and embryology
what is a cell
Kulunbawi Reply
cell is smallest unit of life. cells are often cell the building blocks of life...
the first twenty element
Orapinega Reply
what are the characteristics of living things?
growth,respiration,nutrition,sensitivity, movement,irritability, excretion,death.
What is the difference between adaptation and competition in animals
Adeyemi Reply
What is biology
it is a natural science stadey about living things
Biology is the bronch of science which deals with the study of life is called biology
what is the x in 300 stands for?
Ogbudu Reply
the properties of life
Clarinda Reply
response to the environment, reproduction, homeostasis, growth,energy processing etc.....
what is reproduction
Reproduction is a fundamental feature of all known life,each individual organism exist as a result of re production.....or else Multiplying...
a complete virus particle known as
Darlington Reply
These are formed from identical protein subunitscalled capsomeres.
fabace family plant name
Pushpam Reply
in eukaryotes ...protein channel name which transport protein ...
Pushpam Reply
in bacteria ...chromosomal dna duplicate structure called
what is a prokaryotic cell and a eukaryotic cell
Matilda Reply
There are two types of cells. Eukaryotic and Prokaryotic cells. Prokaryotic cells don't have a nucleus or membrane enclosed organelles (little organs within that cell). They do however carry genetic material but it's not maintained in the nucleus. Prokaryotic cells are also one celled.
Prokaryotic cells are one celled (single celled).
Prokaryotic cells are Bacteria and Archea
Prokaryotic cells are smaller than Eukaryotic cells.
Eukaryotic cells are more complex. They are much bigger than Prokaryotic cells.
Eukaryotic cells have a nucleus and membrane bound organelles.
Eukaryotic cells are animals cells which also includes us.
Eukaryotic cells are also multicellular.
nice explaination
eukaryotic cells are individual cells .. but eukaryotes are multicellular organisms which consist of many different types of eukaryotic cells
also eukaryotic cells have mitochondria. prokaryotic cells do not
in prokaryotes only ribosomes are present... in eukaryotes mitochondria ...glogi bodies ..epidermis .....prokaryotes one envelop but eukaryotes compartment envelop....envelop mean membrane bound organelles......
prokaryotic cell are cells dat have no true nuclei i.e no cell membrane while eukaryotic cell are cell dat have true nuclei i.e have cell membrane
we have 46 pair of somatic cell and 23 pair of chromosomes in our body, pls can someone explain it to me. pls
Matilda Reply
we have 22 pairs of somatic chromosomes and one pair of sex chromosome
we have 23 pairs of chromosomes,22 pairs of somatic and one pair of sex chromosomes
23 chromosomes from dad & 23 chromosomes from mom 23 +23=46 total chromosomes
X & Y chromosomes are called sex cells, the very presence of a Y chromosome means the person is Male.
XX Female XY Male
If a Karyotype has more than 46 Chromosomes then nondisjunction occured. For example, having an extra chromosome 21 will cause Down Syndrome.

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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