Lymphatic System Slides

1. THE LYMPHATIC SYSTEM
SGO

2. Hematopoiesis
Blood is a fluid consisting of formed elements and plasma. It is produced by bone marrow, and the volume depends on body
weight.

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 Functions of Blood;
 It provides a means of transportation for…
• respiratory gases… oxygen and carbon dioxide
• Chemicals, such as those found in food, hormones, and salts
• Cells that protect the body from foreign substances

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Plasma;
 It is the fluid part of the blood.
 It is clear or straw-colored.
 It comprises 55% of the total blood
volume, and is mostly water and
proteins:
• albumin,
• globulin,
• fibrinogen, and
• prothrombin.
Erythrocytes;
 They are the red blood cells formed in
the red marrow inside bones.
 They carry oxygen and carbon dioxide.
Thrombocytes;
 They are platelets, about half the size
of erythrocytes.
 They play an important role in the
clotting of blood.

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Leukocytes;
 They are white blood cells, the body’s
defense against pathogens (bacteria or
virus).
 They move through cell walls to areas of
infection, ingesting and destroying the
pathogens.
Neutrophils
 They are one of the 5 types of leukocytes.
 A ‘neutrophil count’ identifies the number of
white blood cells that are aren’t busy
elsewhere, and are available to go fight an
infection.

6. THE LYMPHATIC SYSTEM
As blood passes through the capillaries in the tissues, fluid oozes out through the
porous walls of the capillaries,
The fluid then circulates through the tissues themselves, & reach every cell.
This fluid is called tissue or interstitial fluid;
It fills the interstices or the spaces btw the cells to form different tissues.
It is a clear, watery, straw-coloured fluid similar to the plasma of the blood (where it is
derived).
It carries nutrients, oxy & H2O from the blood stream to each individual cells
Also carries away its waste products e.g. CO2, urea & H2O back to the blood

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The escaped fluid from the capillaries into the tissues;
A certain amount returns to the blood stream through the capillary wall, though very
difficultly (due to constant flow of blow against its current).
The remaining & excess fluid which cannot directly make it back into the blood stream is
channeled using the alternative vessels called lymphatic system.
And the fluid in the vessels/ lymphatic system contains is called lymph.

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9. The Components of the Lymphatic System
The lymphatic system comprises 4 types of structure;
Lymphatic capillaries
Lymphatic vessels
Lymphatic nodes
Lymphatic ducts
The lymphatic capillaries;
They arise in the spaces around the tissues as fine hair-like porous wall vessels
They gather up excess fluid from the tissues and unite to form the Lymphatic Vessels.
The wall is permeable to mol. Subt of greater size than blood capillaries

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The Lymphatic Vessels;
They are thin-walled, collapsible tubes similar in structure to the veins (carrying lymph, not
blood).
They are finer and more numerous than the veins
They are provided with valves to prevent lymph moving in the wrong direction.
They are in most tissues, except the CNS (though found in the subcutaneous tissues)
They pass through the lymphatic nodes.
The Lymphatic Nodes;
They are small bodies varying in size from a pin-head to like an almond
They receive from lymphatic vessels at afferent vessels
The afferent vessels run & divide within the node, & release lymph into the lumen
The released lymph gathered at the efferent vessels
The efferent vessels then empty the lymph into the lymphatic ducts

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The lymphatic nodes have similar essential cells like WBC (lymphocytes)
The functions of the lymphatic nodes;
To filter the lymph of bacteria as it passes through
To provide fresh lymphocytes for the blood stream
To produce some antibodies and antitoxin to prevent infection
The lymphatic nodes and the parts it filtered ;
THE NECK & under the CHIN: head, tongue & floor of the mouth
THE AXILLA: upper limb & chest wall
THE GROIN: lower limb & lower abdominal wall
THE THORAX & ABDOMEN: internal organs

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Special areas where lymphatic tissues are found;
The palatine and pharyngeal tonsils
The thymus gland
Mass of lymphatic follicles in the S.I
Appendix and
spleen

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The Lymphatic Ducts;
After filtration by the nodes the lymph is emptied by the lymphatic vessels into the 2
lymphatic ducts; i) the thoracic duct (large/45cm long) ii) the right lymphatic duct
The thoracic duct runs up from the small pouch at the back of the abdomen called cisterna
chyli
Cisterna chyli receive lymph from; the lower limbs, abdominal and pelvic organs
The run up of the thoracic duct through the mediastinum behind the heart & the root of
the neck
 It turns to the left to join lymphatic vessels from the left side of the head, thorax and
left upper limbs
 And finally empties into the left subclavian veins in connection with internal jugular
vein

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The right lymphatic duct (small/ 1cm)
 Joins the lymphatic vessels from the right side of the head, thorax and right
upper limb at the root of the neck
 It runs into the right subclavian vein then into the internal jugular vein
NOTE:
The lymphatic ducts collect all the lymph and return it to the blood stream
for constant renewal of the fluid

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The functions of the lymphatic system are:
It helps in the collection of excessive fluid/lymph from the tissues for constant
stream of fresh fluid to circulate.
It enables excess proteins in the tissues to return into blood stream
It helps in filtering lymph bacterial infection & harmful substances
It enables the production of fresh lymphocytes for the circulation
The lymphatic vessels in the abdominal organs assist in the absorption of
digested food, esp. fat

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The mechanism of the lymphatic circulation;
The lymphatic circulation is maintained partly by suction and partly by pressure
*The suction; as the lymphatics empty into the large veins approaching the heart with
negative pressure (-P) due to suction (as the heart expands & towards the thorax during
inspiration).
The pressure; as pressure is exerted on the lymphatic, as on the veins, by the contraction of
the muscles, and the this outside pressure drives lymph onwards because the valves
prevent a backward flow

22. The Spleen
The spleen is a large nodule of lymphoid tissue.
By function, it belongs to the circulatory system (as in lymphatic nodes).
It is a deep purplish-red color.
It lies high up (left side) posterior to the stomach.
It is enclosed in a capsule of fibrous tissue, & fibrous strands make a supporting
meshwork throughout the gland.
The spaces of the meshwork are filled in with a pulp-like material called the
splenic pulp (contains cells of different types like lymphocytes)

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Others are phagocytes which engulf WBC (break down worn out WBC).
Observing roles of spleen;
A source of fresh lymphocytes for the blood stream
A seat for the destruction of RBCs
Fighting of infection e.g. malaria & typhoid
Helps in manufacturing antibodies to fight infections
NOTE: the spleen is not seriously essential to life , & can be removed by operation
e.g. in haemolytic anaemia