16 Lymphatic

Lymphatic System and Immunity

• network of vessels that assist in circulating fluids• transports excess fluid away from interstitial spaces• transports fluid to the bloodstream• transports fats to bloodstream• help defend the body against diseases

Lymphatic Vessels

Lymphatic Pathways

Lymphatic Capillaries

• microscopic• closed-ended tubes• in interstitial spaces of most tissues

Lymphatic DuctsThoracic Duct• Right Lymphatic Duct

Tissue Fluid and Lymph

Lymph• tissue fluid that has entered a lymphatic capillary

Lymph Movement

• action of skeletal muscles• respiratory movements*•Inhale (low pressure)•Exhale (diaphragm increases pressure)

• smooth muscle in larger lymphatic vessels• valves in lymphatic vessels

Lymph Nodes

Lymph Nodes

• cervical region• axillary region• inguinal region• pelvic cavity• abdominal cavity• thoracic cavity• supratrochlear region

Functions of Lymph Nodes

• filter potentially harmful particles from lymph• immune surveillance by macrophages and lymphocytes• areas of lymphocyte production

Thymus

• small in an adult• superior to the heart • site of T lymphocyte production

Spleen

• largest lymphatic organ• upper left abdominal cavity

•Inferior to the diaphragm• resembles a large lymph node •sinuses filled with blood• white pulp

• lymphocytes• red pulp

• red blood cells• lymphocytes• macrophages

Body Defenses Against Infection

• pathogen• disease causing agent• bacteria, viruses, etc

• innate defenses • general defenses• protects against many pathogens

• adaptive defenses• immunity• more specific • carried out by lymphocytes

Innate Defenses

• Species Resistance• resistance to certain diseases to which other species are susceptible

• Mechanical Barriers• skin• mucous membranes

•Chemical Barriers• enzymes in various body fluids• pH extremes in stomach• high salt concentrations• interferons• defensins• collectins

Innate Defenses

• Fever • inhibits microbial growth• increases phagocytic activity

• Natural Killer Cells• type of lymphocyte• defend the body against various viruses and cancer by secreting perforins

Innate Defenses

• Inflammation• tissue response to injury

• red, swollen, warm & painful• white blood cells attracted to area

• pus• clot forms• fibroblasts arrive

• enclose the area• helps prevent spread of pathogen

• phagocytes are active• cell division replaces lost cells

• Phagocytosis• neutrophils

• small particles• monocytes

• larger particles• macrophages• destruction of foreign particles

Lymphocyte Origins

Lymphocyte Origins

• Undifferentiated lymphocytes released •T cells• thymus• 70-80% of lymphocytes• lymph nodes, thoracic duct & white pulp of spleen

Lymphocyte Origins

• Undifferentiated lymphocytes released • B cells• remain in red bone marrow• 20-30% of lymphocytes• lymph nodes, spleen, bone marrow & intestinal lining

Lymphocyte Functions

• T cells•interact directly with foreign invaders•cellular immune response

• B cells•interact indirectly•produce antibodies to destroy specific antigens•humoral immune response

T Cells

• requires antigen-presenting cell• requires MHC antigens• helps T cells recognize that an antigen is foreign

• types of T cells• helper T cell • stimulate B cells to make antibodies

• cytotoxic T cell• aka killer T cells• destroy cells by cutting openings in them

• memory T cell• future response w/o delay

T Cell and B Cell Activation

B Cell Proliferation

Graft Types

• Isograft – identical twin• Autograft - self• Allograft – same species• Xenograft – different species