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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 the difference between anatomy and psychology
milika Reply
nothing
Sohil
hahaha Anatomy vs. Physiology. Students of anatomy learn about the structure of body parts, while those enrolled in physiologystudy the functions and relationships of body parts. While these two fields are often paired together in the same class or program title, they may also be offered separately.
Sohil
what is gross anatomy?
Vasco Reply
is the macroscopic form of anatomy where organs will be seen without the use of microscope
Kofi
yes
Aaliyah
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Memory
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godfrey
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Maddy
what is anatomy
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is the structure of the part of the body
Kofi
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Kabiru Reply
when is pregnancy expected after ovulation
Kabiru
Minimum blood pressure
Hasnain Reply
120/80
AmirHameed
90/60
baila
120/80
Sri
were can anatomy work
capella Reply
in hospitality
Sri
what is normal flora
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it's one kind of bacteria
Tariq
the smallest blood vessel is capillary
Richard Reply
How does deoxygenated blood become oxygenated during blood circulation?
Richard
plzzz explain cardiac cycle
Piya Reply
what is anatomy
Gifty Reply
is the study of body structure
Amos
how types of tissue in body
mwiya
What are some of first questions are expected in anatomy and physiology course
Milner Reply
what is pacemaker
mekfira
its a device that is put into the heart to make sure it beats properly
Michelle
SA node produces impulse is called pacemaker
Piya
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Khubaib
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Hayat
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Hong
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hlo
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IDDRISU
which of the following is the epithelial tissue that lines the interior of blood vessels?
Firomsa Reply
endothelial tissues
Osaki
Endothelial tissue
mabast
why are the questions only 3
Chisom Reply
you too can ask
Addo
what is the function of the skeletal system?
Cris
what is the treatment of herpes simplex virus?
riad Reply
the long bone with two primary center's of ossification for shaft is ________
Aarambam
medulla
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Ravi
ha moj ha
Hani
doctor and nurse
Ravi
y 're the questions only 3
Chisom
women are much likely to be pregnant at which stage?
Fatoumatta Reply
There are only six days during any cycle when a woman can get pregnant - the five days leading up to ovulation and the 24 hours after ovulation. This is because sperm can live for up to 5 days in a woman's body, and the ovum lives for only 12-24 hours.
THE
right
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does this apply to women close to menopose
Kuria
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when after they have intercourse
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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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