Lymphatic System

Lymphatic Organs

Thymus gland:

• Bilobed gland
• Located on sternum
• Stops growing at age 1
• Age 60 decreases in size
• Produces and matures lymphocytes

• Tonsils:
• Palatine tonsils on each side of oral cavity
• Pharyngeal tonsils near internal opening of nasal cavity (adenoid)
• Lingual tonsils posterior surface of tongue
• Form a protective ring of lymphatic tissue around nasal and oral cavities

Components

• Lymphatic vessels:
• Resemble small veins
• Where lymphatic capillaries join
• One way valves

Lymphatic System

Lymphatic Capillaries and Vessels

• Carries fluid in one direction from tissues to circulatory system
• Fluid moves from blood capillaries into tissue spaces

• Lymph: fluid that enters lymphatic capillaries composed of water and some solutes
• Lymphocytes
• Lymphatic vessels
• Lymph nodes
• Tonsils
• Spleen
• Thymus gland

• Lymphatic capillaries:
• Tiny, closed-ended vessels
• Fluid moves easily into
• In most tissues
• Join to form lymphatic vessels

• Right lymphatic duct:
• Where lymphatic vessels from right upper limb and right head, neck, chest empty
• Empties into right subclavian vein

Lymph nodes:

• Rounded structures that vary in size
• Located near lymphatic vessels
• Groin, armpit, neck
• Lymph passes through lymph nodes before entering blood
• Lymph moves through and immune system is activated (lymphocytes produced) if foreign substances are detected
• Removal of microbes by macrophages

• Thoracic duct:
• Rest of body empties from lymphatic vessels
• Empties into left subclavian vein

Spleen:

• Size of clenched fist
• Located in abdomen
• Filters blood
• Detect and respond to foreign substances
• Destroy old red blood cells
• Blood reservoir
• White pulp: lymphatic tissue surrounding arteries
• Red pulp: contains macrophages and red blood cells that connect to veins