Anatomy & Physiology
Overview of The Lymphatic System
A. Importance of the lymphatic system:
1. Two most importance functions—maintain fluid balance in
the internal environment & immunity
2. Lymph vessels act as “drains” to collect excess tissue fluid &
return it to the venous blood just before it returns to the heart.
3. Lymphatic System—specialized component of the circulatory
system; is made up of:
Isolated nodules of lymphatic tissue
You’ll need to
be able to ID
Lymph & Interstitial Fluid
1. Clear, water-appearing fluid found in the lymphatic
vessels; closely resembles blood plasma in composition
but has a lower percentage of protein; isotonic.
2. Elevated protein concentration in thoracic duct lymph
due to protein-rich lymph from the liver and small
B. Interstitial fluid-
1. Complex, organized fluid that fills the spaces between
the cells; resembles blood plasma in composition with a
lower percentage of protein.
2. Along with blood plasma, constitutes the extra cellular
A. Distribution of lymphatic vessels-
1. Lymphatic capillaries-microscopic blind-end vessels where
lymphatic vessels originate, wall consists of a single layer of
flattened endothelial cells; networks branch and *anastomose
freely.*Anastomosis is the connection of two structures. It refers to
connections between blood vessels.
2. Lymphatic capillaries merge to form larger lymphatic and eventually
form the main lymphatic trunks the right lymphatic ducts and the
3. Lymph from upper right quadrant empties into right lymphatic duct &
then into right subclavian vein.
4. Lymph from rest of the body empties into the thoracic duct, which then
drains into the left subclavian vein.
We’ll talk about this in a bit…..
Cont of Lymphatic Vessels…
B. Structure of lymphatic vessels-
1. Similar to veins except lymphatic vessels have
thinner walls, have more valves and contain lymph
2. Lymphatic capillary wall is formed by a single layer of
thin, flat endothelial cells
C. Functions of the lymphatic vessels-
1. Remove high-molecular-weight substances and even
particular matter from interstitial spaces.
2. Lacteals absorb fats & other nutrients from the small
Circulation of Lymph
A. The Lymphatic pump
1. Lymph moves through the system in the right
direction due to the large number of valves.
2. Breathing movements & skeletal muscle
contractions establish a lymph pressure
gradient, as they do with venous blood.
3. Lymphokinetic actions—activities that result
in a central flow of lymph.
A. Structure of Lymph nodes
1. Lymph nodes are oval-shaped structures enclosed by a fibrous capsule.
2. Nodes are similar to biological filter
3. Once lymph enters a node, it moves slowly through sinuses to drain in
to efferent exit vessel
B. Location of Lymph nodes
1. Most lymph nodes occur in groups
2. Location of groups with greatest clinical importance are
submental & submaxillary groups & superficial cervical,
superficial cubital, axillary, and inguinal lymph nodes
3. Preauricular lymphs nodes located in front of the ear drain
superficial tissues and skin on the lateral side of the head and face.
THE LYMPH NODE
Cont. of Lymph Nodes
C. Functions of lymph nodes—perform two distinct
1. Defense functions: filtration & phagocytosis—
reticuloendothelial cells remove microorganisms
and other injurious particles from lymph and
phagocytose them; if overwhelmed, the lymph
nodes can become infected or damaged.
2. Hematopoiesis—process of blood cell formation,
lymphatic tissue is the site for the final stages of
maturation of some lymphocytes & monocytes.
Lymphatic drainage of the breast
A. Distribution of lymphatics in the breast
1. Drained by two sets of lymphatic vessels
a. Lymphatics that drain the skin over the breast with the
exception of the areola & nipple
b. Lymphatics that drain the substance of the breast as well
as the skin of the areola & nipple
2. Superficial vessels coverage to form a diffuse, cutaneous
3. Subareolar plexus-this is located under the areola
surrounding the nipple, where communication between
the cutaneous plexus & larger lymphatics that drain the
secretory tissue & ducts of the breast occurs
A. Pectoralis major muscle
B. Axillary lymph nodes:
C. Axillary lymph nodes:
D. Axillary lymph nodes:
E. Subclavicular lymph
F. Internal mammary
A. Location- under the mucous membranes in the
mouth & back of the throat.
1. Palatine tonsils-
located on each side of the throat.
2. Pharyngeal tonsils-
located near the posterior opening of the
3. Lingual tonsils-
located near the base of the tongue
B. Function- Protect against bacteria that may
invade tissues around the openings the
nasal & oral cavities.
A. Location & appearance of the Thymus
1. Primary central organ of lymphatic system
2. Single, unpaired organ located in the
mediastinum, extending upward to the
lower edge of the thyroid & inferiorly as far
as the 4th costal cartilage
3. Thymus is pinkish gray in children and
wish advancing age, becomes yellowish as
lymphatic tissue is replaced by fat.
B. Structure of the Thymus
1. Pryamid-shaped lobes are subdivided into small lobules
Cont. of Structure of the Thymus
2. Each lobule is composed
of a dense cellular cortex
& an inner, less dense,
3. Medullary tissue can be
identified by presence of
C. Function of the Thymus
1. Plays vital role in immunity mechanism
2. Source of lymphocytes before birth
3. Shortly after birth, the thymus secretes
Thymosin, which enables lymphocytes to
develop into T-Cells….
A. Location-in the left
(either one of two
regions of the
the left kidney &
& behind the
fundus (the base of
an organ) of the
Cont of Spleen
B. Structure of the Spleen
1. Ovoid in shape
2. Surrounded by fibrous capsule with inward
extensions that divide the organ into compartments.
3. White pulp-dense masses of developing lymphocytes
4. Red pulp-near outer regions, made up of a network of fine
reticular fibers submerged in blood that comes from nearby
C. Functions of the Spleen
1. Defense-macrophages lining the sunusoids of the spleen remove
microorganisms from the blood & phagocytose them
2. Hematopoiesis-monocytes & lymphocytes complete their development
in the spleen.
3. Red blood cell and platelet destruction-macrophages remove worn-out
RBC’s and imperfect platelets and destroy them by phagocytosis;
also salvage iron and globin from destroyed RBC’s
Don’t confuse Lymphedema with Edema…
We’ll get to this later!
Cycle of Life:
A. Dramatic changes throughout life
B. Organs with lymphocytes appear before birth
and grow until puberty
1. Organs atrophy (shrink in size, degenerate)
through late adulthood and become fatty or fibrous.
2. Spleen-it develops early and remains intact
The Big Picture:
The Lymphatic System & The Whole Body
A. Lymphatic system drains away excess water
from large areas
B. Lymph is conducted through lymphatic
vessels to nodes, where contaminants are
C. Lymphatic system benefits the whole body
by maintaining fluid balance and freedom
What Is Lymphedema?
Lymphedema is an accumulation of lymphatic fluid in the interstitial tissue that causes
swelling, mostly in the arm(s) and/or leg(s), and occasionally in other parts of the body.
Lymphedema can develop when lymphatic vessels are missing or impaired (primary),
or when lymph vessels are damaged or lymph nodes removed (secondary).
When the impairment becomes so great that the lymphatic fluid exceeds the lymphatic
transport capacity, an abnormal amount of protein-rich fluid collects in the tissues of the
Left untreated, this stagnant, protein-rich fluid not only causes tissue channels to
increase in size and number, but also reduces oxygen availability in the transport
system, interferes with wound healing, and provides a culture medium for bacteria that
can result in lymphangitis (infection).
Lymphedema should not be confused with edema resulting from venous insufficiency,
which is not lymph-edema. However, untreated venous insufficiency can progress into
a combined venous/lymphatic disorder which is treated in the same way as
What Causes Lymphedema?
Primary lymphedema, which can affect from one to as many as
four limbs and/or other parts of the body, can be present at birth,
develop at the onset of puberty (praecox) or in adulthood (tarda),
all from unknown causes, or associated with vascular anomolies
such as: Port Wine Stain, and Klippel Trenaury (a rare congenital
medical condition in which blood vessels and/or lymph vessels fail
to form properly).
Secondary lymphedema, or acquired lymphedema, can develop as
a result of surgery, radiation, infection or trauma. Specific
surgeries, such as surgery for melanoma or breast, head and neck,
prostate or testicular, bladder or colon cancer, all of which currently
require removal of lymph nodes, put patients at risk of developing Port Wine Stain
If lymph nodes are removed, there is always a risk of developing
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