Download Immune system

Disorders in the immune system can cause disease.
Immunodeficiency diseases occur when the immune
system is less active than normal, resulting in recurring
and life-threatening infections. Immunodeficiency can
either be the result of a genetic disease, such as severe
combined immunodeficiency, or be produced by
pharmaceuticals or an infection, such as the acquired
immune deficiency syndrome (AIDS) that is caused by
the retrovirus HIV. In contrast, autoimmune diseases
result from a hyperactive immune system attacking
normal tissues as if they were foreign organisms. Common
autoimmune diseases include rheumatoid arthritis,
diabetes mellitus type 1 and lupus erythematosus. These
critical roles of immunology in human health and disease
are areas of intense scientific study
The immune system protects organisms
from infection with layered defenses of increasing
specificity. Most simply, physical barriers prevent
pathogens such as bacteria and viruses from entering the
body. If a pathogen breaches these barriers, the innate
immune system provides an immediate, but non-specific
response. Innate immune systems are found in
all plants and animals. However, if pathogens
successfully evade the innate response, vertebrates
possess a third layer of protection, the adaptive immune
system. Here, the immune system adapts its response
during an infection to improve its recognition of the
pathogen. This improved response is then retained after
the pathogen has been eliminated, in the form of
an immunological memory, and allows the adaptive
immune system to mount faster and stronger attacks each
time this pathogen is encountered.
Immune system unites organs and
tissues, which provide defense from
genetically foreign cells or matters,
that got from out or are generated
inside the organism, providing
constancy of internal organism
environment. Organs of immune
system may be divided into central
and peripheral part.
Thymus
gland
 Red marrow.


organs are not enveloped in capsule
(tonsils, lymphoid follicles,
lymphocytes);
capsulated organs (lymphatic
nodes and spleen).
THYMUS GLAND
Thymus, or thymus
gland, located in
superioanterior
part of the thoracic
cavity behind the
manubrium of
the sternum. It
consists of two
lobes, lobus dexter
et sinister, connected
to
each other by means
of loose connective t
issue.
The upper, narrower ends of lobes is usually
beyond
the
the
edge
top
thoracic
above
cavity,
the
overhang
manubrium
of
sternum and sometimes reaching the thyroid
gland.
Extending
downward,
the
thymus
gland lies in front of large vessels of the
heart and part of the pericardium. The value
of the gland varies with age.
At newborn it weighs about 12 grams,
and continues to grow after
birth until puberty, when it reaches
a weight of 35-40 g, then (14-15
years) begins the process of involution,
which resulted in it weight around the age
of 25 once again falls to 25 g, the age of
60 it less than 15 g to 70 - about 6 g.
Atrophy are mainly
in lateral gland sites and the
lower part, so that
the gland, because it persists in the
adult, takes a
more elongated shape. During the
involution elements of the gland are
largely replaced by fatty tissue while
preserving the general outlines
of thymus.
Topography
skeletotopy of the gland:
in children it projected to top 1.5 cm above the manubrium
of the sternum, the
bottom reaches III,
IV, and sometimes V ribs.
In adults, as a rule, cervical part of the
gland is absent and the upper edge is
located behind the manubrium
of sternum at different distances
from its incisure down. The
lower edge corresponds to the
second intercostal space or III rib.
Syntopy of the gland is
different in children
and adults. Thus, in children
under 3 years old cervical part
of gland is behind the
sternothyroid and
sternohyoid muscles. The
posterior surface adjacent to
the trachea.
Anterior surface of thoracic
part of thymus adjacent to
the posterior surface of the
sternum. The lower surface
of the gland adjoins against
the pericardium.
The posterior surface adjacent to
the major vessels.
Anterioexternal surface to the right
and left covered with pleura. In adults, after the
removing of manubrium of sternum become
visible tissue, where are
located in varyingquantities glandular remnants.
The front of the gland is covered with sheets
of connective tissue, which, as a continuation of
cervical fascia, combined with the pericardium.
Structure.
Thin connective tissue
capsule, giving of inside
the gland septa, which
divide it into lobule, which
consist of cortex (darker) and
medulla.
Both substances consist of
adenoid tissue in the; in the
loops of the
network (reticulum)
occur lymphoid elements. In
the cortex,
they form clusters, similar to
the follicles of lymph nodes,
and in
the medulla scattered nests of
concentric structures cells
called Hassall corpuscles.
Function.
Functioning as an organ of formation of lymphocytes, the
thymus probably produce a hormone that influences the
growth and deposition in the bones lime.
Gland involution during puberty indicates a
close connection with its function of sexual glands. At an
early castration thymus is not subject to the changes
that it undergoes an adult. This
suggests that gonadal hormones lead to involution of the
thymus gland. Sometimes it persists into adulthood,
while increasing the lymphatic system, genital
hypoplasia and reduced physical and mental resistance
(status-thymico-lymphaticus), which can cause sudden
death in the operating anesthesia.
Thymus is placed in front part of superior mediastinum
and consists of lobes, more frequent two. Outside this
gland is tunicate by fibrous capsule that gives off septa,
which split up lobes on lobules. They comprise reticular cells
with lymphocytes between them (called as ‘thymocytes’).
The lobules of gland have a cortex and medulla thymi. Can
be accessories lobules of thymus. Basic function of thymus
maturation and supporting of effector cells (killer) and
regulatory cells (helper and supressor) Т-lymphocytes
populations. Also thymus takes part into regulation of
neuro-muscular transmission, phosphoric-calcium
metabolism, carbohydrate and peptide metabolism,
interaction with other endocrine glands (that's why one
can be consider thymus gland as a endocrine organ).
Red marrow
is sole haemopoetic organ in adult and central organ
of immune system. Stem cells are generated in it, they
are like lymphocytes because their morphology and
during cell-fission give beginning to all formal blood
elements, also including cells providing immunity - to
leukocytes and lymphocytes. Red marrow in adult is
situated in cells of spongy matter of flat and short
bones, in epiphysis of long tubular bones. Yellow
marrow is situated in diaphysis of long tubular bones.
Largest amount of red marrow is situated into
epiphysis of femoral and tibiae bones.