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Emigration

This figure shows how leukocytes respond to chemical signals from injured cells. The top panel shows chemical signals sent out by the injured cells. The middle panel shows leukocytes migrating to the injured cells. The bottom panel shows macrophages phagocytosing the pathogens.
Leukocytes exit the blood vessel and then move through the connective tissue of the dermis toward the site of a wound. Some leukocytes, such as the eosinophil and neutrophil, are characterized as granular leukocytes. They release chemicals from their granules that destroy pathogens; they are also capable of phagocytosis. The monocyte, an agranular leukocyte, differentiates into a macrophage that then phagocytizes the pathogens.

Classification of leukocytes

When scientists first began to observe stained blood slides, it quickly became evident that leukocytes could be divided into two groups, according to whether their cytoplasm contained highly visible granules:

  • Granular leukocytes contain abundant granules within the cytoplasm. They include neutrophils, eosinophils, and basophils (you can view their lineage from myeloid stem cells in [link] ).
  • While granules are not totally lacking in agranular leukocytes    , they are far fewer and less obvious. Agranular leukocytes include monocytes, which mature into macrophages that are phagocytic, and lymphocytes, which arise from the lymphoid stem cell line.

Granular leukocytes

We will consider the granular leukocytes in order from most common to least common. All of these are produced in the red bone marrow and have a short lifespan of hours to days. They typically have a lobed nucleus and are classified according to which type of stain best highlights their granules ( [link] ).

Granular leukocytes

The  left image shows a neutrophil, the middle image shows an eosinophil, and the right image shows a basophil.
A neutrophil has small granules that stain light lilac and a nucleus with two to five lobes. An eosinophil’s granules are slightly larger and stain reddish-orange, and its nucleus has two to three lobes. A basophil has large granules that stain dark blue to purple and a two-lobed nucleus.

The most common of all the leukocytes, neutrophils    will normally comprise 50–70 percent of total leukocyte count. They are 10–12 µ m in diameter, significantly larger than erythrocytes. They are called neutrophils because their granules show up most clearly with stains that are chemically neutral (neither acidic nor basic). The granules are numerous but quite fine and normally appear light lilac. The nucleus has a distinct lobed appearance and may have two to five lobes, the number increasing with the age of the cell. Older neutrophils have increasing numbers of lobes and are often referred to as polymorphonuclear    (a nucleus with many forms), or simply “polys.” Younger and immature neutrophils begin to develop lobes and are known as “bands.”

Neutrophils are rapid responders to the site of infection and are efficient phagocytes with a preference for bacteria. Their granules include lysozyme    , an enzyme capable of lysing, or breaking down, bacterial cell walls; oxidants such as hydrogen peroxide; and defensins    , proteins that bind to and puncture bacterial and fungal plasma membranes, so that the cell contents leak out. Abnormally high counts of neutrophils indicate infection and/or inflammation, particularly triggered by bacteria, but are also found in burn patients and others experiencing unusual stress. A burn injury increases the proliferation of neutrophils in order to fight off infection that can result from the destruction of the barrier of the skin. Low counts may be caused by drug toxicity and other disorders, and may increase an individual’s susceptibility to infection.

Questions & Answers

what is thymus?
Jakia Reply
The thymus is a specialized primary lymphoid organ of the immune system.  thymus is located in the upper front part of the chest, in the anterior superior mediastinum, behind the sternum, and in front of the heart.
Analyn
if you are shot with a bullet and it penetrate your lung, which thoracic body cavity will be affected, and which layer of serous membrane would damage first?
Mnm Reply
hello
Abila
heart and cell membrane
Romantic
Anterior thoracic body cavity will be affected and parietal layer of serous membrane will he damaged.
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Romantic
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Ishwar
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Romantic
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Francis Reply
I think it is related to the digestive system. if it is then it is a way of saying that every task is done in a systematic way.
Mitali
hi
Samuel
yes it is related to desigestive system it is the system that breakdown c you eat,release their nutrients and absorb the nutrients into the body.
Charles
how many bones does a baby has
Rita Reply
206
Hussain
300
Mitali
300
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Vineeta
300
irshad
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Vineeta
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abul Reply
What's the pathophysiology of Coronary heart disease
Yemzzy Reply
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AYOMIDE Reply
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Peace
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Suzy
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Virgilio
hi rajib hemophilia is a bleeding disorder that shows down the blood clotting process
Sabika
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Ateeq
the protrusion of a loop or knuckle of an organ or tissue through an abnormal opening
Hussein
hernia mean 👆
Hussein
the lower part of the rectum that cannot develop hence mutated
Fibi Reply
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Luba
femur
John
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Fatima Reply
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Johna
the study of the human body structure and how the parts are organised.
Charles Reply
Anatomy
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Josefs
Structure of human body?
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levels of organization of the human body
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ATIM
the smallest cell in body
what is the function of stomach?
Bilal
the sperm is smallest cell in body
asma
anatomical description of human heart
Luceno Reply
what is human heart in anatomical perspective?
Luceno
Heart is a hollow muscular organ situated in the between the lungs in a space called mediastinum
Rukayya
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Esther
How many cells are there in the body?
Esther
different between primary and secondary healing
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what are the components of e cell
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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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