Lymphatic System and Immunity

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Chapter 20

• Lymphatic System and Immunity

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Lymphatic System

• Lymph Fluid
• Lymphatic vessels also referred to as lymphatics
• Lymphatic tissue
• Lymphatic nodules
• Lymph nodes
• Tonsils
• Spleen
• Thymus

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Functions of the Lymphatic System

• Fluid balance
• Fat absorption
• Defense

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Lymphatic Vessels

• Lymphatic capillaries join to form
• Lymphatic vessels
• Lymph nodes Distributed along vessels and filter
  lymph
• Lymphatic trunks Jugular, subclavian,
  bronchomediastinal, intestinal, lumbar
• Lymphatic ducts Right and thoracic which connect
  to large veins

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Lymphatic Capillaries

• Lymphatic Capillaries
• Remarkably permeable
• Proteins in interstitial space are unable to
  enter blood capillaries but enter lymphatic
  capillaries easily.
• When tissues are inflammed lymphatic capillaries
  take in cell debris, pathogens, and cancer cells.

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Lymphatic Capillaries

• Lymphatic Capillaries
• Lacteals
• Chyle

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Lymphatic Vessels

• Vessels
• Collecting vessels
• Lymphatic trunks
• Lymphatic ducts

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Lymphatic Vessels

• Vessels
• Collecting vessels
• Lymphatic trunks
• Lymphatic ducts

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Lymph Transport

• Lack pumping organ
• They are low pressure vessels
• Depend on
• Milking action of active skeletal muscles
• Pressure changes in thorax during breathing
• Valves to prevent backflow
• Pulsations of nearby arteries
• Smooth muscle in the walls of lymphatic ducts and
  thoracic duct

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Lymphoid Cells

• Lymphocytes
• T cells
• Manage immune response
• Cell mediated immunity
• Attack and destroy
• B cells
• Plasma cells
• Secrete antibodies
• Humoral immunity

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Lymphoid Cells

• Lymphocytes
• Lymphoid macrophages
• Dendritic cells
• Reticular cells

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Lymphatic Tissue

• Lymphatic tissue
• Houses and provides a proliferation site for
  lymphocytes
• Surveillance vantage point
• Reticular connective tissue
• Types
• Diffuse lymphatic tissue
• Lymphoid follicles
• Germinal centers

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Lymph Nodes

• Principal lymphoid organs
• Functions
• Lymph filters
• Help activate the immune system.

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Lymph Nodes

• Structure
• Cortex
• Medulla

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Lymph Nodes

• Circulation
• Afferent lymphatic vessels
• Subcapsular sinus
• Hilus
• Efferent lymphatic vessels

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Lymphatic Organs

• Tonsils
• Spleen
• Thymus
• Lymphoid Follicles

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Tonsils

• Large groups of lymphatic nodules in nasopharynx
  and oral cavity
• Provide protection against bacteria and other
  harmful material
• Groups
• Palatine
• Pharyngeal
• Lingual

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Spleen

• Located in left superior side of abdomen
• Blood flows through at 3 different rates
• Fast (most), slow, intermediate
• Functions
• Destroys defective RBCs
• Salvages iron and other breakdown products
• RBC production in fetus
• Detects and responds to foreign substances
• Stores blood platelets and RBCs.

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Spleen

• Types of tissue
• White pulp
• Red pulp

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Spleen
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Thymus

• Located in superior mediastinum
• Divisions Cortex and medulla
• Site of maturation of T cells

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Thymus

• Located in superior mediastinum
• Divisions Cortex and medulla
• Site of maturation of T cells
• Differs from other lymphoid organs
• Functions strictly in T cell maturation
• Stroma consists of epithelial cells rather than
  reticular fibers.