Lymphatic system Introduction: Components:

 

 	


–       Lymph is the fluid
–       Lymphatics nodes
–       Structures & organs


 	
Functions:

–       Return tissue fluid to the bloodstream.
–       Transport fats from the digestive tract to the bloodstream.
–       Surveillance & defense.
Lymphatics:


 	
Originate as lymph capillaries
 	
Capillaries unite to form larger vessels

–       Resemble veins in structure
–       Connect to lymph nodes at various intervals


 	
Lymphatics ultimately deliver lymph into 2 main channels:

–       Right lymphatic duct:


 	
Drains the right side of head & neck, right arm, right thorax
 	
Empties into the right subclavian vein

–       Thoracic duct:


 	
Drains the rest of the body
 	
Empties into the left subclavian vein.

Main channels of lymphatics:
Lymphatic tissues:


 	
3 types:

–        Diffuse lymphatic tissue:


 	
No capsule present.
 	
Found in the connective tissue of almost all organs.

–        Lymphatic nodules:


 	
No capsule presents.
 	
Oval-shaped masses.
 	
Found singly or in clusters.

–        Lymphatic organs:


 	
Capsule present.
 	
Lymph nodes, spleen, thymus gland.

Lymph nodes:


 	
Oval structures located along lymphatics.
 	
Enclosed by a fibrous capsule.
 	
Cortex: outer portion

–       Germinal centers produce lymphocytes


 	
Medulla: the inner portion

Medullary cords:


 	
Lymph enters nodes through afferent lymphatics, flows through sinuses, exits through efferent lymphatic.

Tonsils:


 	
Multiple groups of large lymphatic nodules.
 	
Location: mucous membrane of the oral and pharyngeal cavities
 	
Palatine tonsils:

–       Posterior-lateral walls of the oropharynx


 	
Pharyngeal tonsil:

–       The posterior wall of the nasopharynx


 	
Lingual tonsils:

–       Base of tongue
Spleen:


 	
Largest lymphatic organ
 	
Located between the stomach & diaphragm
 	
A structure like a node:

–       Capsule present
–       But no afferent vessels or sinuses


 	
Histology:

–       The red pulp contains all the components of circulating blood
–       White pulp is like lymphatic nodules


 	
Functions:

–       Filters blood
–       Stores blood
Thymus gland:


 	
Location: behind the sternum in the mediastinum
 	
The capsule divides it into 2 lobes
 	
Development

–       Infant: conspicuous
–       Puberty: the maximum size
–       Maturity:  decreases in size


 	
Function

–       Differentiation and maturation of t cells
The function of the lymphatic system:


 	
Defense against harmful organisms and chemicals
 	
2 types of defense:

–       Nonspecific
–       Specific


 	
Specific defense: immunity:

–       Humoral immunity involves b cells that become plasma cells that produce antibodies that bind with specific antigens.