Download lymphatic organs - Appoquinimink High School

Think, think, think…
What is a lymphocyte? Where does it
come from? Where does it go?
The Lymphatic System
• consists of organs, ducts, and nodes
• transports a watery clear fluid called lymph
• distributes immune cells and other factors
throughout the body
• interacts with the blood circulatory system to
drain fluid from cells and tissues
The Lymphatic System
• contains immune cells called lymphocytes
which protect the body against antigens
(viruses, bacteria, etc.) that invade the body.
Main functions
• to collect and return interstitial fluid, including
plasma protein to the blood, and thus help
maintain fluid balance
• to defend the body against disease by
producing lymphocytes
• to absorb lipids from the intestine and
transport them to the blood.
Lymph organs
• include the bone marrow, lymph nodes,
spleen, and thymus.
• Precursor cells in the bone marrow produce
lymphocytes.
• B-lymphocytes (B-cells) mature in the bone
marrow.
• T-lymphocytes (T-cells) mature in the thymus
gland.
Lymph organs
• Besides providing a home for lymphocytes (Bcells and T-cells), the ducts of the lymphatic
system provide transportation for proteins,
fats, and other substances in a medium called
lymph.
BONE MARROW
• site of maturation of B lymphocytes
• Many pre-B cells die in the bone marrow
• B cells that survive this selection process leave
the bone marrow through efferent blood
vessels.
THYMUS
• Flat, bilobed organ situated above the heart
and below the thyroid gland
• Each lobe is surrounded by a capsule and is
divided into lobules
• Each lobule is organized into two
compartments: the cortex (outer
compartment) the medulla (inner
compartment)
THYMUS
• In the cortex, the network is densely packed with
thymocytes (developing T cells)
• In the cortex, the network is densely packed with
thymocytes. Cells are less dense in medulla.
• largest relative size at birth
• largest actual size is at puberty
• Following puberty the thymus begins to shrink. In
elderly individuals it is usually less than 3 grams
in weight.
• The site of T-cell maturation
Spleen
• Creates lymphocytes for the
destruction and recycling of old
red-blood cells. The spleen is
also a blood reservoir.
• It supplies the body with blood
in emergencies such as a bad
cut. The spleen is also the
location where white blood
cells trap organisms.
Spleen
• The spleen is shaped like a loose fist and is
tucked under the left side of the diaphragm.
• The average weight of an adult spleen is 0.44
lbs. During and after digestion, the size of the
spleen increases. Infection of malaria or mono
can also cause the spleen to increase in size.
Lymph nodes
• Human lymph nodes are bean-shaped and
range in size from a few millimeters to
about 1-2 cm in their normal state.
• They may become enlarged due to a tumor
or infection. White blood cells are located
within honeycomb structures of the lymph
nodes.
• Lymph nodes are enlarged when the body
is infected due to enhanced production of
some cells and division of activated T and B
cells.
• In some cases they may feel enlarged due
to past infections; although one may be
healthy, one may still feel them residually
enlarged.
Tonsils
• Tonsils are clusters of lymphatic tissue just
under the mucous membranes that line the
nose, mouth, and throat (pharynx).
• Lymphocytes and macrophages in the tonsils
provide protection against harmful substances
and pathogens that may enter the body
through the nose or mouth.
Lymph
• means clear water and it is basically the fluid
and protein that has been squeezed out of the
blood (i.e. blood plasma).
• The lymph is drained from the tissue in
microscopic blind-ended vessels called lymph
capillaries.
Lymph
• These lymph capillaries are very permeable,
and because they are not pressurized the
lymph fluid can drain easily from the tissue
into the lymph capillaries.
• As with the blood network the lymph vessels
form a network throughout the body, unlike
the blood the lymph system is a one-way
street draining lymph from the tissue and
returning it to the blood.
Lymphatic Capillaries
• begin in the tissue spaces as blindended sacs. Lymph capillaries are
found in all regions of the body
except the bone marrow, central
nervous system, and tissues, such as
the epidermis, that lack blood
vessels
• The wall of the lymph capillary is
composed of endothelium in which
the simple squamous cells overlap
to form a simple one-way valve.
This arrangement permits fluid to
enter the capillary but prevents
lymph from leaving the vessel.
Lymph Vessels
• lymph capillaries merge to form lymphatic
vessels. Small lymphatic vessels join to form
larger tributaries, called lymphatic trunks,
which drain large regions. Lymphatic trunks
merge until the lymph enters the two
lymphatic ducts. The right lymphatic duct
drains lymph from the upper right quadrant of
the body. The thoracic duct drains all the rest.
Lymph Vessels
• Like veins, the lymphatic tributaries have thin
walls and have valves to prevent backflow of
blood. There is no pump in the lymphatic
system like the heart in the cardiovascular
system. The pressure gradients to move lymph
through the vessels come from the skeletal
muscle action, respiratory movement, and
contraction of smooth muscle in vessel walls.
Your assignment
• Chapter 14 sections 1-6
–Check your recall pp. 369, 370,
371, 373
–Review exercises p 389
• Q. 1, 3, 4, 5, 6, 7
This will be checked for a grade.