Transcript The Lymphatic System - Leaving Cert Biology

Chapter 32: The human
lymphatic system
Leaving Certificate Biology
Higher Level
The Lymphatic System
• Involves a one-way system of vessels that returns
excess tissue fluid to the bloodstream
• Tissue fluid is the extremely thin layer of fluid
(plasma) that surrounds all cells and comes from
diffusion of plasma through capillary walls
• Diffusion occurs through the capillary wall due to
blood pressure
• Lymph vessels, like capillaries, are present
throughout all tissues and collect this excess tissue
fluid which is then called lymph
• After entering the lymph vessel it travels back to the
blood through the subclavian veins (3L/d)
Lymphatic System
Flow of Lymph
• Lymph flows along the lymph vessels by
rhythmic contraction of the muscular walls
of the lymph vessels and by contraction of
the skeletal muscles
• Lymph vessels (like veins) have valves to
prevent backflow of lymph
• The lymphatic drainage system is absent
from the teeth, bone, bone marrow, and
the central nervous tissue
Lymph Nodes
• Lymph nodes are small bean-shaped structures
that have dense masses of lymphocytes and
monocytes
• They are widely distributed throughout the body
along the lymphatic pathways where they filter the
lymph before it is returned to the blood
• Lymph nodes are not present in the central
nervous system
• There are three superficial regions on each side of
the body where lymph nodes tend to cluster:
– Groin
– Armpit
– Neck
The Lymphatic System
• There are two general roles of the
lymphatic system:
– Circulatory role
– Defence role
The Lymphatic System
• Circulatory role:
– Returns the proteins lost from capillaries
– Returns fluid lost from capillaries – maintains
blood pressure and volume
– Removes excess tissue fluid – prevents
swelling (oedema)
– Collection of lipids from the small intestine
and transfer to the blood via the subclavian
veins
The Lymphatic System
• Defence role:
– Bacteria, viruses, cancer cells, cell debris and
toxins are removed from the lymph by lymph
nodes
– Lymph nodes continually monitor lymph for
infections and cancer
– Lymphocytes and monocytes multiply in
lymph nodes during an infection