Lymphatic System

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Chapter 17

• Lymphatic System

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Overview

• Lymph and lymphatic vessels
• Formation of lymph
• Circulation and drainage
• Structure and function of lymphoid organs
• Lymph nodes
• Tonsils
• Thymus gland
• Spleen

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• The Lymphatic System
• System of tissues and vessels
• Scattered throughout the body
• Services almost all regions

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• Functions of the Lymphatic System
• Fluid balance
• Lymph fluid
• Protection from infection
• Absorption of fats

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The 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 u What
type of blood vessel receives lymph collected
from the body?
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Checkpoint 17-1 What are the three functions of
the lymphatic system?
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• Lymphatic Circulation
• One-way system
• Begins in tissues
• Ends in bloodstream

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• 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)

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Checkpoint 17-2 What are two differences between
blood capillaries and lymphatic capillaries?
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• Lymphatic Vessels
• Superficial sets
• Deep sets
• Nodes
• Right lymphatic duct
• Thoracic duct (left lymphatic duct)

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Vessels and nodes of the lymphatic system. (A)
Lymph nodes and vessels of the head. (B) Drainage
of right lymphatic duct and thoracic duct into
subclavian veins.
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Checkpoint 17-3 What are the two main lymphatic
vessels?
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• Movement of Lymph
• Segments of vessels located between the valves
  contract rhythmically
• Skeletal muscles compress vessels

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• Lymphoid Tissue
• Distributed throughout the body
• Makes up specialized organs of lymphatic system

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Lymphoid tissue
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• Lymph Nodes
• Structure
• Fibrous connective tissue capsule
• Afferent lymphatic vessel
• Sinuses
• Cords
• Nodules
• Medulla
• Efferent lymphatic vessel
• Grouping
• Cervical nodes
• Axillary nodes
• Mesenteric nodes
• Inguinal nodes

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Structure of a lymph node. (A) Arrows indicate
the flow of lymph through the node. (B) Section
of a lymph node as seen under the microscope (low
power). (B, Reprinted with permission from
Cormack DH. Essential Histology. 2nd ed.
Philadelphia Lippincott Williams Wilkins,
2001.)   Zooming In u What type of lymphatic
vessel carries lymph into a node? What type of
lymphatic vessel carries lymph out of a node?
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Checkpoint 17-4 What is the function of the
lymph nodes?
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• The Tonsils
• Remove contaminants and trap pathogens
• Palatine tonsils
• Pharyngeal tonsil (adenoids)
• Lingual tonsils

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Checkpoint 17-5 Tonsils filter tissue fluid.
What is the general location of the tonsils?
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• 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

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Checkpoint 17-6 What kind of immune system cells
develop in the thymus?
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• The Spleen
• Cleanses blood
• Filtration
• Phagocytosis
• Destroys old red blood cells
• Produces red blood cells before birth
• Is reservoir for blood

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Checkpoint 17-7 What is filtered by the spleen?