Introduction:
The lymphatic system is a complex network of thin vessels,
valves, ducts, nodes, and organs.
Lymph: It is the fluid, formed from the
interstitial fluid due to the permeability of the lymph capillaries
it flows through the lymphatic system.
Formation:
When blood passes via blood capillaries through tissues, 9/10 of
fluid passes into the venous end of capillaries from the arterial
end.
And remaining 1/10 of the fluid passes into lymph
capillaries.
Composition:
It contains 96% water, 4% solids and some blood cells.
Solids include Protein, Lipids, Urea, creatinine, Amino acids,
Electrolytes, and Lymphocytes.
Functions:
- Return protein from tissue spaces into blood.
- Redistribution of fluid in the body.
- Removal of bacteria, toxins and other foreign bodies/
- Maintenance of structural and functional integrity of the
tissue.
Lymphatic drainage of the right pinky
finger:
- The lymphatic system arises from tissue spaces as a meshwork of
delicate vessels.
- These vessels are called lymph capillaries.
- Lymphatic capillaries are the sites of lymph fluid collection
and are distributed throughout most tissues of the body,
particularly connective tissue.
- Lymphatic capillaries reabsorb excessive tissue fluid and
interstitial fluid from the blood capillaries and transport the
fluid through the lymphatic pathway, and ultimately dispose it into
the blood.
- In the case of the right pinky finger, the capillaries would
arise from the digital branch of the ulnar artery.
- This fluid is mainly water from plasma from the blood capillary
that leaks into the interstitial space in the tissues due to
pressure forces exerted by capillaries (hydrostatic pressure) or
through osmotic forces from proteins (osmotic pressure).
- When the pressure for interstitial fluid in the interstitial
space becomes large enough it leaks into lymph capillaries, which
are the site for lymph fluid collection.
- When pressure is greater in the interstitial fluid than in
lymph, the minivalve cells (present in the lymph capillaries and
acting as a valve) separate slightly and interstitial fluid enters
the lymphatic capillary. When pressure is greater inside the
lymphatic capillary, the cells of the minivalves adhere more
closely, and lymph cannot flow back into the interstitial
fluid.
- The lymph vessels that receive lymph fluid from many
capillaries are called collecting vessels.
- Lymphatic capillaries are slightly larger in diameter and have
greater oncotic pressure than blood capillaries.
- The lymph capillaries feed into larger lymph vessels
- Lymph flows in one direction toward the heart.
- Lymph vessels become larger, with better developed smooth
muscle and valves to keep lymph moving forward despite the low
pressure and adventitia to support the lymph vessels.
- As the fluid increases, the lymph vessels become larger their
function changes from collecting fluid from the tissues to
propelling fluid forward.
- The fluid reaches the nearest lymph node.
- These capillaries form large lymphatic vessels.
- The lymph nodes are present along the course of lymphatic
vessels.
- Lymph nodes work like a biological filtering system of the
lymph.
Filtration of lymph:
In the case of the right pinky finger, the lymph would
be transported to the lateral group of the axillary lymph
nodes.
- Lymph circulates to the lymph node via afferent lymphatic
vessels and drains into the lymph node in the subcapsular
sinus.
- Small glands called lymph glands or lymph nodes are interposed
during the course of lymph vessels.
- When lymph passes through lymph nodes, it is filtered i.e, the
water and electrolytes are removed. But, the proteins and lipids
are retained in the lymph.
- The bacteria and other toxic substances are destroyed by
macrophages.
- Because of this, lymph nodes are called defense barriers.
- Each lymph node is formed by a cortical sinus and a medullary
sinus.
- The cortex contains collections of lymphocytes. These contain
predominantly B-lymphocytes and some T-lymphocytes.
- The medullary sinus is lined by phagocytes.
- The lymph vessel reaching a node is called the afferent
vessel.
- It divides into many small channels, which open through
cortical sinuses.
- The sinuses open into medullary sinuses.
-
When the body is invaded by foreign organisms, the painful
swelling sometimes felt in the neck, armpits, groin, or tonsils
comes from the microorganisms being trapped inside collections of
lymph cells or nodes.
-
Eventually, these organisms are destroyed and eliminated by
cells that line the walls of the lymph nodes and the swelling and
pain subside.
- The nodes contain white blood cells that can attack any
bacteria or viruses they find in the lymph as it flows through the
lymph nodes.
- From medullary sinuses, 1 or 2 efferent vessels arise and leave
the node.
Collecting ducts: Formed by the convergence of
larger lymphatic vessels called lymphatic trunks.
- In the case of the right pinky finger, the efferent vessels
from lateral axillary nodes and form the right lymphatic duct and
it returns lymph to the right subclavian vein which then merges
into the vena cava, the large vein that brings deoxygenated blood
to the heart.
In the case of a pathogen present.
- Lymph contains lymphocytes.
- they recognize the proteins on surface of the pathogens called
antigens.
- Lymphocytes recognize that these are foreign and produce
antibodies.
- The antibodies cause pathogens to stick together and make it
easier for phagocytes to engulf them.
- They can also be drained to the lymph node as explained
above.