The Lymphatic System
HONORS ANATOMY
CHAPTER 20
Lymphatic System
Parts
Functions
returns fluids that
have leaked out of
blood vessels 
blood vessels
2. provides structural
basis of Immune
System
1.
1.
2.
3.
4.
5.
lymphatic vessels
Lymph: fluid in those
vessels
Lymph Nodes: structures
that cleanse the lymph
that flows through them
Spleen
Thymus
Lymphatic Vessels
 1-way network
 lymph flows:
 LYMPHATIC CAPILLARIES  COLLECTING
VESSELS  TRUNKS & DUCTS  LARGE
BLOOD VEINS  HEART
Lymphatic Capillaries
 very permeable
 pick up fluids, proteins, particulate matter from
interstitial spaces
 edges of adjacent cells overlap on entry point

essentially acts a valve (or swinging door) so fluid flow only
goes in
 from capillaries lymph flows through progressively
larger vessels
Lacteals
 special set of lymphatic capillaries in small
intestines
 transport fat from villi  blood
Collecting Lymphatic Vessels
 travel with
 superficial veins
 deep arteries
 same 3 tunics as veins but have:
 thinner walls
 more internal valves
 anastomose more(junctions with other collecting vessels)
Lymphatic Trunks
 union of larger collecting vessels
 major lymphatic trunks (all paired but #5)
1.
2.
3.
4.
5.
lumbar
bronchomediastinal
subclavian
jugular
intestinal
Lymphatic Ducts
 receive lymph from the lymphatic trunks
 *right lymphatic duct
 right upper limb
 right side of head & thorax
 *left lymphatic duct *aka thoracic duct
 drains
everything else
 Cisterna chyli: beginning portion, an enlarged
sac anterior to L1 – L2
Lymph Transport
 no pump to transport lymph  veins
 flow slow, maintained by
1.
2.
3.
contraction of skeletal muscle
pressure changes in thorax
contractions of lymphatic vessels
Lymphoid Cells
1.
2.
3.
4.
5.
Lymphocytes
Plasma cells
Macrophages
Dendritic cells
Reticular cells: form framework of lymph nodes,
spleen
Lymphoid Tissue
 reticular CT
 houses macrophages, lymphocytes, dendritic cells
 appears:
diffuse
2. Follicles: densely packed
 may have germinal centers: B cell proliferating
1.
Lymph Nodes
 clustered along
lymphatic vessels
 Function:
1. filter lymph
2. involved in
activation of
immune system
Sentinel Node
 1st node that receives lymph drainage from a body
area suspected of being cancerous
 gives best indication of metastasis thru lymphatics
Spleen
 Functions:
1.
2.
3.
4.
5.
site for lymphocyte proliferation
destroys aged or defective RBCs & bloodborne
pathogens
stores & releases breakdown products of Hgb
stores plts
fetal site of hematopoiesis
Splenomegaly
 enlargement of the spleen due to accumulation of
infectious microorganisms
 Causes:
1. Septicemia
2. Mononucleosis
3. Malaria
4. Leukemia
Thymus
 T lymphocyte maturation & development of
immunocompetence
 most active during youth
MALT
 Mucosa-Associated Lymphoid Tissue
 Function: prevent pathogens from penetrating
mucous membranes
 includes:
1. Peyer’s patches in intestinal wall
2. Tonsils
3. lymphoid follicles in appendix, genitourinary
tract, respiratory tract