Ch 11 Lymphatic System

Lymphatic vessels

-Open-ended capillaries

-Contain one-way valves

-Merge to form lymphatic trunks

Lymph

-Recycled blood plasma

-Interstitial fluid once it has entered the lymphatic system

Lymphedema

When interstitial fluid accumulates in tissues

Lymphatic capillaries

-Also called terminal lymphatics

-Empty into larger lymphatic vessels

-Where interstitial fluid enters the lymphatic system to become lymph

Lymphatic trunks

Vessels that carry lymph and empty it into the blood via lymphatic ducts

Right lymphatic duct

-Drains lymph into the right subclavian vein

-Right sides of the head, thorax and right upper limb

Thoracic duct

-Drains into the left subclavian vein

-Starts under the diaphragm in the cisterna chyli

Primary lymphoid organs

-Where lymphocytes mature

-Bone marrow and thymus gland

Thymic involution

Shrinking of thymus gland due to age

Immunoenescence

The loss of immune function with age

Secondary Lymphoid Organs

-Where lymphocytes mount immune responses

-Lymph nodes, spleen and lymphoid nodules

Lymph Nodes

• “Filters of the lymph”

• Remove debris and pathogens from lymph

• Contains dendritic cells and macrophages

• The site of adaptive immune responses mediated by T cells, B cells and accessory cells

Spleen

• “Filter of the blood”

• Vascular organ found in the left side of the abdominal cavity under the diaphragm

• Contains dendritic cells and macrophages

Lymphoid nodules

Dense clusters of lymphocytes found in the respiratory and digestive tracts

Tonsils

• Lymphoid nodules along the inside of the pharynx

• Develop immunity to oral pathogens

Pharyngeal tonsil

• Located at the back of the throat

• Referred to as the adenoid when swollen

Phagocytic cells of the innate immune response

Macrophages and Neutrophils

Macrophages

• First line of defense to pathogens

• Involved in both innate and adaptive immune responses

Neutrophil

• Attracted via chemotaxis to infected tissues

• Contains cytoplasmic granules with vasoactive mediators such as histamine

Apoptosis

Programmed cell death

Cytokine

Signaling molecule that allows cells to communicate over short distances

Chemokine

Attracts cells (chemotaxis) from longer distances

Interferons

-Proteins secreted by cells infected with viruses

-Travels to adjacent cells, inducing them to make antiviral proteins

Dendritic cells

Attracted to areas of infection

Monocyte

Differentiates into a macrophage or dendritic cell

Inflammatory response

-The hallmark of the innate response

-Injured cells stimulate mast cells to release substances such as histamine

IgM

Antibody that is effective against bacteria

Opsonization

When an antibody binds to a pathogen to mark it as a target for phagocytes

IgG

Antibody that crosses the placenta to protect fetus from disease

IgE

Associated with allergies and annaphylaxis

IgA

-Protects body surfaces

-Found in breast milk

Cytotoxic T cell (Tc)

Kills target cells by inducing apoptosis

Helper T Cell (Th)

Releases cytokines to regulate other immune system cells

Suppressor T Cell

• Also known as regulatory T cell

• Controls T cell response, preventing excess T cell formation during an immune response

Kaposi’s sarcoma

Caused by the human herpes virus

Liver cancer

Caused by hepatitis B virus

Cervical cancer

Caused by human papilloma virus

Cancer vaccines

Directed against the cells of one’s own body

Severe combined immunodeficiency disease (SCID)

Genetic defects result in impaired B and T cells of the adaptive immune response

Human immunodeficiency virus (HIV)

• Can lead to full-blown AIDS

• Wipes out the immune system completely

• Flu-like symptoms 1-2 weeks after infection

Type 1 hypersensitivty

-Allergies

-Rapid response

-Antihistamines treat mild allergies

-Epinephrine treats severe allergies

Type II hypersensitivty

Occurs during mismatched blood transfusions and blood compatibility diseases like erythroblastosis fetalis

Type III hypersensitivty

Occurs with diseases like systemic lupus erythematosus  

Type IV hypersensitivty

Delayed hypersensitivty

Sensitization

First exposure to an antigen

Celiac disease

Damage to small intestine

Diabetes mellitus type I

-Targets beta cells of pancreas

-Low insulin production

Graves’ disease

Targets thyroid-stimulating hormone receptor, causing hyperthyroidism

Hashimoto’s thyroiditis

Targets thyroid-stimulating hormone receptor, causing hypothyroidism

Myasthenia gravis

Targets acetylcholine receptor, causing debilitating muscle weakness

Rheumatoid arthritis

• Targets joint capsule antigens

• Chronic inflammation of joints

Afferent lymphatic vessels

Those that lead into a lymph node

Allergen

Substance capable of producing allergic reaction

Autoimmune disease

• Caused by the inability of the body to distinguish its own cells from foreign substances

• Produces antibodies that attack its own tissues

Chyle

• Lipid-rich lymph

• Found inside lymphatic capillaries of small intestine

Efferent lymphatic vessels

Those that lead out of a lymph node

Histamine

Primary cause of allergies and anaphylactic shock