The Lymphatic System and Immunity Chapter 21 Lecture Notes

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The Lymphatic System and ImmunityChapter 21
Lecture Notes

• to accompany
• Anatomy and Physiology From Science to Life
• textbook by
• Gail Jenkins, Christopher Kemnitz, Gerard Tortora

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Essential Terms

• pathogen
• disease-producing microbes
• resistance
• ability to defend against damage or disease
• susceptibility
• lack of resistance
• nonspecific resistance/innate defenses
• provide immediate and general protection
• specific resistance/immunity
• develops in response to particular invader

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Introduction

• Lymphatic System and Immunity
• Circulates body fluids and defends against
  disease-causing agents
• Innate defenses and immunity protect against
  general and specific damage or disease
• Lymphatic system is closely related to
  cardiovascular and digestive systems

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Lymphatic System

• Vessels and fluid that transport various
  substances
• Help maintain fluid homeostasis
• Tissues contain stem cells that develop into
  various types of blood cells
• Helps defend body against disease-causing agents
• Lymph
• Located within lymphatic vessels and tissue

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Figure 21.1
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Lymphatic Tissue

• Specialized reticular connective tissue
• Lymphocytes
• B cells
• T cells

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Functions of Lymphatic Tissue

• Drain excess interstitial fluid
• Transport dietary lipids
• Carry out immune responses

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Lymphatic Vessels

• Lymphatic capillaries
• Tiny and located between cells
• Closed at one end
• Lymphatic vessels
• Thinner walls than veins
• More valves than veins
• Lymphatic nodes
• Lymph flows through masses of B and T cells

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Figure 21.2
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Lymphatic capillaries

• Larger diameter than blood capillaries
• Overlapping endothelial cells
• Pressure from interstitial fluid causes cells to
  separate allowing fluid in
• Pressure within vessels causes cells to press
  closer together preventing outflow of lymph
• Anchoring filaments

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Lymph Trunks

• Lymph trunks
• Union of vessels exiting most proximal chain of
  lymph nodes
• Meet at one of two main ducts
• Principal Trunks
• Lumbar
• Intestinal
• Bronchomediastinal
• Subclavian
• Jugular

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Figure 21.3
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Thoracic Duct

• Also left lymphatic duct
• Cisterna chyli
• Receives from intestinal and right and left
  lumbar trunks
• Drains lymph to venous blood at junction of left
  internal jugular and left subclavian veins

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Lymph Flow

• Skeletal muscle pump
• Respiratory pump

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Figure 21.4
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Lymphatic Organs

• Widely distributed
• Two classifications based on function
• Primary lymphatic organs
• Immunocompetent
• Red bone marrow
• Thymus
• Secondary lymphatic organs and tissues
• Immune response
• Lymph nodes
• Spleen
• Lymphatic nodules lack capsule

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Thymus

• Two lobes separated by capsule of connective
  tissue
• Trabeculae separate lobes into lobules
• Cortex
• Types of cells in cortex
• T cells, dendritic, and macrophages
• Epithelial cells
• Produce thymic hormones
• Medulla
• T cells more mature
• Thymic (Hassalls) corpuscles
• Thymus begins to atrophy at puberty
• Populates secondary lymphatic organs and tissues
  with T cells

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Figure 21.5a
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Figure 21.5b
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Figure 21.5c
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Lymph Nodes

• Along lymphatic vessels and scattered throughout
  the body
• Groups near surface regions of
• Cervical area
• Axillary
• Inguinal
• Capsule with trabeculae
• Inner network of reticular fibers and fibroblasts

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Figure 21.6a
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Figure 21.6b
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Figure 21.6c
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Lymph Nodes

• Outer cortex
• Lymphatic nodules of B cells
• Germinal center
• Plasma cells and memory B cell formation
• Memory B cells
• Have memory of specific antigens
• Inner cortex
• T cells and dendritic cells
• Medulla
• B cells, plasma cells, and macrophages
• Reticular fiber and cell network

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Flow Through Lymph Nodes

• Lymph flows one-way through node
• Afferent lymphatic vessels
• Valves direct lymph into node
• Sinuses
• Subcapsular sinus
• Trabecular sinuses
• Medullary sinuses
• Efferent lymphatic vessels
• Valves direct lymph, antibodies, and activated T
  cells out of node
• Hilus

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Spleen

• Largest mass of lymphatic tissue
• Hilus
• Passage for splenic artery, splenic vein and
  efferent lymphatic vessels
• White pulp
• Lymphocytes and macrophages
• Central arteries
• Red pulp
• Venous sinuses
• Splenic cords
• RBCs, macrophages, lymphocytes, plasma cells,
  and granulocytes

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Functions of Spleen

• Macrophage removal of damaged blood cells and
  platelets
• Storage of platelets
• Hemopoiesis of fetus

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Figure 21.7
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Lymphatic Nodules

• Not surrounded by capsule
• MALT (mucosa-associated lymphatic tissue)
• Most solitary but some large aggregates of
  nodules
• Peyers patches
• Tonsils
• Pharyngeal tonsil / adenoid
• Palatine tonsils
• Lingual tonsils
• p body reactions for repair
• T cells mature in thymus
• Antigen receptors
• Able to recognize specific antigens
• CD4 or CD8