lymphatic system

Lacteals

• specialized structures of the lymphatic system

  • Dietary fats are transformed in the cells of the lacteals

  • Lymphatic vessels return the fats to the venous circulation

Interstitial fluid (intercellular or tissue fluid)

• Plasma from arterial blood that flows out of the arterioles and into the capillaries

• Delivers nutrients, oxygen, an hormones to the cells

• About 90% of this fluid returns to the bloodstream

Lymph

• clear, watery fluid containing electrolytes and proteins

  • Works in close cooperation with the immune system to protect the body

  • Made up of the remaining 10% of the returning interstitial fluid

Lymphatic Circulation

• Blood circulates throughout the entire body in a loop, pumped by the heart

• The lymphatic system must depend on the pumping motion

• Lymph flows in only one direction

• Lymph is filtered by lymph nodes, which are located along lymphatic
  vessels

Since lymph is a clear fluid, the lymphatic vessels are not readily
visible

Lymphatic Capillaries

• Microscopic, blind-ended tubes

• Sealed on one end 

• Located near the surface of the body

Capillary walls that are only one
cell in thickness

• These cells separate briefly to allow the lymph to enter the capillary

• The action of the cells closing forces the lymph to flow upward and forward

Lymphatic vessels

• Flow from lymphatic capillaries into progressively larger lymphatic vessels

• Prevent the backward flow of lymph

Right lymphatic duct

collects lymph from the right side of the head and neck, the upper right quadrant of the body, and the right arm

Thoracic duct

collects lymph from the left side of the head and neck, the upper left quadrant of the trunk, the left arm, the entire lower portion of the trunk, and both legs

Cervical lymph nodes

located along the sides of the neck

Axillary lymph nodes

located under the arms in the area known as the armpits

Inguinal lymph nodes

located in the inguinal (groin) area of the lower abdomen

Lymphocytes (Lymphoid Cells)

• Leukocytes formed in bone marrow as stem cells

  • Defend the body against antigens (substances that the body regards as being foreign)

Natural killer cells (NK cells)

Play a role in killing cancer cells and cells infected by viruses

B cells (B lymphocytes)

• Specialized lymphocytes that produce antibodies

• Transform into a plasma cells when confronted with an antigen

• After transformation into plasma cells, destroy specific antigens

T cells (T lymphocytes)

• Get the T in their name from their origin in the thymus

• Play a central role in cell-mediated immunity

Cytokines

• Group of proteins such as interferons and interleukins 

• Act as intracellular signals to begin the immune response

Interferons

Activate the immune system, fight viruses, and signal other cells to increase defenses

Interleukins

• Play multiple roles in the immune system

• Direct B and T cells to divide and proliferate

The Tonsils

• Three masses of lymphoid tissue

• Form a protective ring around the back of the nose and upper throat

Adenoids (nasopharyngeal tonsils)

Located in the nasopharynx

Palatine tonsils

Located on the left and right sides of the throat in the area visible at the back of the mouth

Lingual tonsils

• Located at the base of the tongue

• Not readily visible

Thymus Gland

• Mass of lymphoid tissue located above
  the heart

• Reaches its greatest size at puberty

• Becomes smaller with age

• Part of the endocrine system

• Secretes a hormone that stimulates the
  maturation of lymphocytes into T cells

• These T cells leave the thymus through the bloodstream and the lymphatic system

The Vermiform Appendix

• Commonly referred to as the appendix

  • Hangs from the lower portion of the cecum

  • Located in the first section of the large intestine

The Spleen

• Sac-like mass of lymphoid tissue 

• Located in the left upper quadrant of
  the abdomen

• Filters microorganisms and other
  foreign material from the blood

• Forms lymphocytes and monocytes

• Specialized leukocytes (white blood cells)

• Destroys worn-out erythrocytes (red blood cells)

• Stores extra erythrocytes (red blood cells)

Pathogens

disease-producing microorganisms

Allergens

substances that produce allergic reactions

Toxins

poisonous or harmful substances

Malignant cells

potentially life-threatening cancer cells

Immune system

• First attempts to prevent the entry of these harmful substances into the body

• Uses chemical signaling between specialized cells to identify, attack, and remember antigens

• Creates “memory” of the invader; enables the body to mount a more efficient future defense against that antigen

Intact skin

• Wraps the body in a physical barrier to prevent invading organisms from entering

• Covered with acid mantle that makes an inhospitable environment for most bacteria

The Antigen–Antibody Reaction

• Involves binding antigens to antibodies

• This reaction labels a potentially
  dangerous antigen

Immediately responds to the
presence of any antigen

Tolerance

• Refers to an acquired unresponsiveness to a specific antigen

• Also used to describe a decline in the effective response to a drug, usually due to repeated use

Antibodies

Disease-fighting proteins

Phagocytes

• Specialized leukocytes that act as part of the antigen–antibody reaction

• Destroy substances in a process called phagocytosis

Monocytes

• Leukocytes that provide immunological defenses

• Become macrophages and dendritic cells

Macrophages

Leukocyte that surround and kill invading cells

Dendritic cells

• Patrol the body searching for antigens

• Grab an antigen, swallow it, and alert B and T cells to act against the specific antigen

The complement system

• Group of proteins that normally circulate in the blood in an inactive form

• When needed, ward off pathogens by combining with them to dissolve and remove pathogenic bacteria and other foreign cells

Immunity

state of being resistant to a specific disease

Natural immunity (passive immunity)

resistance to a disease present without the administration of an antigen or exposure to a disease

Acquired immunity

obtained by having had a contagious disease

Vaccination

provides protection against the disease; however, for some conditions a periodic booster is required

Allergist

Specialist in diagnosing and treating conditions of altered immunologic reactivity, such as allergic reactions

Infectious disease specialist

Specialist in diagnosing and treating diseases caused by microorganisms

Immunologist

Specialist in diagnosing and treating disorders of the immune system

Lymphologist

Specialist in diagnosing and treating disorders of the lymphatic system

Oncologist

Specialist in diagnosing and treating malignant disorders, such as tumors and cancer

Lymphadenitis (swollen glands)

inflammation of the lymph nodes

Lymphadenopathy

any disease process affecting a lymph node or nodes

Lymphangioma

• benign tumor

  • Formed by an abnormal collection of lymphatic vessels

Ruptured spleen

torn covering of the spleen

Splenomegaly

abnormal enlargement of the spleen

Lymphoscintigraphy

• diagnostic test

  • Detects damage or malformations of the lymphatic vessels

  • A radioactive substance is injected into lymph ducts, and a scanner or probe is used to follow the movement of the substance on a computer screen

Lymphedema

Swelling of the tissues due to an abnormal accumulation of lymph fluid within the tissues

Primary lymphedema

• Hereditary condition

• Develops with swelling beginning in the feet and progressing into the ankles and in an upward direction along the legs

Secondary lymphedema

• Caused by damage to lymphatic vessels

• Most frequently due to cancer treatment, surgery, trauma, or burns

Bioimpedance spectroscopy

• Noninvasive method of diagnosing lymphedema

• Measures the resistance to an electrical current passed through the affected limb, with abnormally low results showing a buildup of lymph

Allergy (hypersensitivity)

Overreaction to a particular antigen

Localized allergic response

Cellular response

Systemic reaction

• Anaphylaxis or anaphylactic shock

• Severe response to an allergen

Scratch test

Identifies common allergens

Antihistamines

• medications

• Relieve or prevent allergy symptoms

Autoimmune Disorders

• Large group of diseases characterized by the immune system producing antibodies against its own tissues

  • Abnormal functioning of the immune system 

  • Appears to be genetically transmitted

• Estimated that 3% of Americans have an autoimmune disorder

  • Women affected 2.7 times more often than men

• Autoimmune disorders affect most body systems

Immunodeficiency Disorders

Occur when the immune response is compromised

Severe combined immunodeficiency (SCID)

Increased susceptibility to infection and failure to thrive as a result of infections

Human immunodeficiency virus (HIV)

• Damages or kills the T cells of the immune system, causing it to progressively fail

Opportunistic infection

Caused by a pathogen that does not normally produce an illness in healthy humans

Acquired immunodeficiency syndrome (AIDS)

advanced and fatal stage of HIV

Kaposi’s sarcoma

opportunistic infection associated with HIV; cancer

ELISA (enzyme-linked immunosorbent assay)

• used to screen for HIV

  • HIV differentiation assay: used to confirm positive ELISA test

Immunotherapy

• Biological therapy

  • Involves either stimulating or repressing the immune response

Treatment of cancers

Immunotherapy stimulates the immune response to fight the malignancy

Treatment of allergies

• Immunotherapy represses the body’s sensitivity to a particular allergen

• Treatment known as allergy desensitization or allergen immunotherapy

Synthetic immunoglobulins (immune serum)

Used as a post-exposure preventive measure against certain viruses

Synthetic interferon

Used in the treatment of multiple sclerosis, hepatitis C, and some cancers

Monoclonal antibodies

• Antibodies produced in the laboratory by identical offspring of a clone of specific cells

• Used to enhance a patient’s immune response to certain malignancies, including non-Hodgkin’s lymphoma, melanoma, breast cancer, and colon cancer

Antiretroviral therapy (ART)

• Sometimes referred to as a treatment
  regimen

• Often more than one drug must be taken in combination with each other

Medications to prevent HIV transmission

• Pre-exposure prophylaxis (PrEP): daily preventative drug for people at high risk

• Post-exposure prophylaxis (PEP): for people with suspected or confirmed HIV exposure

Immunosuppression

Represses or interferes with the ability of the immune system to respond to stimulation by antigens

Immunosuppressant

• Prevents or reduces the body’s normal immune response

• Administered to prevent rejection of donor tissue and to depress autoimmune disorders

Corticosteroid drug

Synthetic hormone that closely resembles the cortisol secreted by the adrenal glands

Cytotoxic drug

• Medication that kills or damages cells

• Used as immunosuppressants or as antineoplastics

Pathogen

Microorganism that causes disease in humans

Bacteria

• One-celled microscopic organisms

• Most are not harmful to humans

Antibiotic-Resistant Bacteria

• Occur when antibiotics fail to kill all of the bacteria they target

• Surviving bacteria become resistant to this particular drug

  • Originally nosocomial (hospital or clinic acquired)

  • Now increasingly common in the general population

Methicillin-resistant Staphylococcus aureus (MRSA)

• Resistant to most antibiotics 

• Infections are serious, difficult to treat; can be fatal

• Often occur repeatedly as breaks in the skin allow the bacteria entry

Fungus

simple parasitic organism

Tinea pedis (athlete’s foot)

fungal infection

Aspergillosis

rare infection caused by mold (a type of fungus) inhaled into the lungs

Yeast

type of fungus

Candidiasis

yeast infection on the skin or mucous membranes in warm, moist areas

Candida albicans (oral thrush)

yeast infection that occurs in the mouth

Parasites

Plants or animals living on or within a living organism at the expense of that organism

Giardiasis

• Diarrheal disease caused by the parasite Giardia

• Most common method of transmission: water that has been contaminated with feces

Malaria

• Caused by a parasite that lives in certain mosquitoes

• Transferred to humans by the bite of an infected mosquito

Toxoplasmosis

Caused by a parasite; most commonly transmitted by contaminated animal feces

Trichomoniasis

Sexually transmitted disease caused by the parasite Trichomonas vaginalis

Viruses

• Very small infectious agents that live only by invading other cells

• Invade a cell, reproduce, break the wall of the cell, release newly formed viruses

• Spread to other cells and repeat the process