The lymphatic system consists of lymphatic vessels, lymph nodes, and lymphoid organs that work together to drain fluid from tissues, absorb fats, and fight infection. Lymphatic vessels carry lymph fluid and drain into lymph nodes which filter the lymph before returning it to the bloodstream. Major lymphoid organs include the spleen, thymus and tonsils, which help produce immune cells and filter blood and lymph respectively. The lymphatic system is essential for fluid balance, fat absorption, and immune defense.

1. Lymphatic system

2. Consists of
• Lymphatic vessels
• Lymphoid tissues and organs

3. • Lymphatic vessels
–Return excess fluid from the tissue
back to the blood stream, about three
liters per day
–One way flow towards the heart
–Proteins and bacteria, cell debris too
big to enter the capillaries return by
lymphatic vessels
–Lymph flow to lymph nodes first

4. Lacteals
• are specialized lymph capillaries in the villi of
the small intestine; they absorb the fat-soluble
end products of digestion, such as fatty acids
and vitamins A, D, E, and K.

5.  The lymph vessels from the lower body unite in front of the
lumbar vertebrae to form a vessel called the cisterna
chyli, which continues upward in front of the backbone as
the thoracic duct.
 Lymph vessels from the upper left quadrant of the body join
the thoracic duct, which empties lymph into the left
subclavian vein. Lymph vessels from the upper right
quadrant of the body unite to form the right lymphatic duct,
which empties lymph into the right subclavian vein.
 Flaps in both subclavian veins permit the entry of lymph but
prevent blood from flowing into the lymph vessels.

7. LYMPHATIC CAPILLARIES
• Lymphatic capillaries spider web between tissue
cells ,and blood capillaries in loose CT
• Lymphatic capillaries are very permeable,
forming flap like minivalves
• They are anchored to surrounding structures by
fine collagen fibers
• Gape open when pressure is high in interstitial
fluid side, and close by opposite

9. • The large lymphatic vessels are:
– Right lymphatic duct: drain the Rt side
of head and neck and Rt upper limb
– Thoracic duct: drain rest of the body
– Both ducts enter the subclavian vein of
its side

11. –Lymphatic vessels are thin walled
–Lymph vessels have one way valve
towards the heart
–Respiratory movements and muscle
contraction act like a pump helps in
lymph return
–Smooth muscle contraction in their
wall help in its return

12. Lymph nodes
Produce lymphocytes which remove bacteria and
tumor cells from body
Thousands of LN are scattered through
lymphatic vessels, filtering lymph before it is
returned to venous blood
•

13. Structure of lymph node
• LN vary in size and shape ,usually kidney
shaped, less than 1 inch long ,buried in
surrounding CT.
• Each node is surrounded by fibrous capsule
• Trabeculae extend inward from cortex dividing
node into compartments.
• Outer part of the LN is cortex, containing
collection of lymphocytes called follicles

14. • Germinal center are dark stained when B
lymphocytes are forming plasma cells which
release antibodies
• Rest of cortical cells are lymphocytes in transit
forming surveillance role, between blood,
lymph Nodes and lymphatic stream.
• Phagocytic macrophages are located in central
medulla.

15. • Lymph enter the convex
side of LN,by afferent
lymphatic vessels
• It run through number of
sinuses
• Exit the lymph node
through efferent lymphatic
vessels at hilus
• Less efferents than
afferents lymph flow is
slow, for lymphocytes and
macrophages to do their
protective function

16. Groups of lymph nodes
• Cervical group: neck
• Axillary group: axilla
• Inguinal group: upper thigh
• Thoracic group: around lung hilum
• Aortic group: around abdominal aorta

17. Other lymphoid organ
Spleen
• Is reddish and largest single mass of lymphoid
tissue
• Blood rich organ that filter the blood
• Fist size,4 inches long, protected by rib cage
• 150 Gm in weight
• Lie in left hypochondrium, look like a shoe
• Between fundus of stomach and diaphragm
• Lie behind 9th,10th,11th rib.

19. SPLEEN
• It has anterior end reach the midclavicular
line, passes downward and forward
• Posterior end is rounded rest on the upper pole
of left kidney
• Spleen has two borders superior is notched
near its anterior end
• Has two surfaces diaphragmatic is smooth and
convex,visceral surface is irregular and concave

21. spleen

22. Relation of spleen
• Gastric impression for fundus of stomach
• Renal impression for left kidney
• Colic impression for splenic flexure of colon
• Pancreatic impression for the tail of pancreas
between hilum and colic impression
• Hilum is found in inferior medial part of
gastric impression
• Hilum transmit splenic vessels and provide
attachments for ligaments

24. Function of spleen
• Immune resopnces,B,T lymphocytes
• Phagocytosis
• Hematopoiesis,RBCS in fetal life ,lymphopoiesis
through adult life
• Storage of red blood cells,8% of RBCs are stored in
spleen

25. Thymus
 Formed of two identical lobes
 Lymphoid mass in the thorax,
overlying the heart, behind
sternum
 Large in children, atrophy in
old age
 Important in immune system
 Produce hormone thymosin

27. Tonsils
• Tonsils are collection of lymphoid tissue lying the aero
digestive tract
• Remove bacteria, and other pathogens entering the
throat
• The reach big size at pubertiy,and gradual atrophy
after that
• The sit of lymphoid tissue is called Waldeyer's
Tonsillar ring include
 Adenoid tonsil nasopharyngeal tonsil
 Two palatine tonsils
 Two tubal tonsils near Eustachian tube
 Lingual tonsil under base of tongue

28. Peyer's patches: found in the wall of small
intestine
MALT: mucosa associated lymphatic tissue
Collection of small lymphoid tissues Protect the
upper respiratory and digestive system,
• Include tonsils and the patches

30. Lymph nodes in the neck
• Horizontal group level I
• Submental tip of tongue floor of mouth, incisor
teeth,gum,central part of lower lip
• Submandibular front of scalp,upper,lower
lip,sinuses,upper,lower teeth, anterior two thirds of
tongue, floor of mouth,vestibule,gum.
• Parotid scalp,ear,eyelid
• Pre auricular ear
• Post auricular scalp, ear
• Occipital back of scalp

31. Cervical lymph nodes
• Vertical group
• Anterior cervical,skin,superficial tissue of front of neck
• Superficial cervical skin of mandible,parotid,ear lobule
• Posterior cervical posterior triangle
• Laryngeal, and tracheal nodes, larynx pre,para
tracheal nodes from trachea, thyroid
• Deep cervical from skull, root of neck Upper, middle
lower jugular
• Jugulodigastric tonsil,tongue,jugulo-omohyoid tongue
• trachea nasopharynx, tongue

33. Levels of lymph nodes in the neck
I,II,III,IV V VI VII

37. LN and area drained