The Lymphatic System
and Lymphoid Tissue
Anatomy & Physiology II
Chapter 16
The Lymphatic System

System of tissues and vessels

Scattered throughout the body

Services almost all regions
Functions of the Lymphatic System

Fluid balance
Lymph fluid

Protection from infection

Absorption of fats
lymphatic system in relation to the
cardiovascular system
Lymphatic
vessels pick up
fluid in the
tissues and
return it to the
blood in vessels
near the heart.
Zooming In:
What type of
blood vessel
receives lymph
collected from
the body?
Lymphatic Circulation

One-way system

Begins in tissues

Ends in bloodstream
Lymphatic Capillaries

Capillary walls (endothelium) are flattened
epithelial cells

More permeable than blood capillaries

Overlapping cells form one-way valves

Arise blindly (closed at one end)

Lacteals absorb digested fats
Lymphatic Vessels

Superficial sets

Deep sets

Nodes

Right lymphatic duct

Thoracic duct (left lymphatic duct)
◦ Cisterna chyli
Lymph Vessels and Lymph Nodes
(A) Lymph
nodes and
vessels of the
head.
(B) Drainage
of right
lymphatic duct
and thoracic duct
into subclavian
veins.
Movement of Lymph

Segments of vessels located between the
valves contract rhythmically

Skeletal muscles compress vessels
Lymphoid Tissue

Distributed throughout the body

Makes up specialized organs of lymphatic
system
Lymph Nodes


Structure
◦ Fibrous connective tissue capsule
◦ Afferent lymphatic vessel
◦ Hilum
◦ Sinuses
◦ Cords
◦ Nodules
◦ Medulla
◦ Efferent lymphatic vessel
Grouping
◦ Cervical nodes
◦ Axillary nodes
◦ Mesenteric nodes
◦ Inguinal nodes
Structure of a lymph
node
(A)
(B)
Arrows indicate the
flow of lymph
through the node.
Section of a lymph
node as seen under
the microscope (low
power).
Zooming In: What type of
lymphatic vessel carries
lymph into a node? What
type of lymphatic vessel
carries lymph out of a
node?
The Spleen

Cleanses blood
◦ Filtration
◦ Phagocytosis

Destroys old red blood cells

Produces red blood cells before birth

Is reservoir for blood
The Thymus

Plays key role in early immune system
development

Produces thymosin
◦ Develops T lymphocyte cells
◦ Promotes lymphocyte growth
◦ Promotes lymphoid tissue activity

Shrinks after puberty
The Tonsils
Remove contaminants and trap pathogens

Palatine tonsils

Pharyngeal tonsil (adenoids)

Lingual tonsils

Surgery to treat if recurrent infection or
enlarged tonsils make swallowing/breathing
difficult
Other Lymphoid Tissue

Appendix

Mucosal-associated lymphoid tissue (MALT)
◦ Peyer patches

Gut-associated lymphoid tissue (GALT)
The Reticuloendothelial System
Cells responsible for destroying worn-out
blood cells, bacteria, cancer cells and other
harmful foreign substances
Monocytes
Macrophages
◦ Kupffer cells
◦ Dust cells
Disorders of the Lymphatic System
and Lymphoid Tissue

Lymphangitis

Septicemia

Lymphadenitis
◦ Cervical
◦ Chronic
Lymphedema
Tissue swelling due to obstruction of lymph
flow caused by

Infection of lymphatic vessels

Vessel blockage
◦ Malignant growth
◦ Parasites

Loss of lymphatic vessels from injury or
surgery
Lymphadenopathy
Enlarged lymph nodes accompany certain
diseases and infections
Acquired
immunodeficiency syndrome (AIDS)
Infectious
mononucleosis
Splenomegaly
Enlarged spleen accompanies certain
diseases and infections
Scarlet
fever
Typhus
fever
Typhoid
fever
Syphilis
Tropical
Splenic
parasitic diseases
anemia
Lymphoma
Any tumor in lymphoid tissue

Malignant disease
◦ Hodgkin disease
◦ Non-Hodgkin lymphoma
End of Presentation