A and P chapter 22

Describe the functions of the lymphatic system.

1. Maintains tissue fluid balance- excess interstital fluid enters lymphatic capillaries and

   becomes lymph.

2. absorbs fat- Transports fats from the small intestine to the veins via lacteals (Specialized lymph capillaries present in the intestinal mucosa., absorb digested fat and deliver chyle (fatty lymph) to blood)

aids in defense- Microorganisms and other foreign substances are filtered from lymph by lymph nodes and from blood by the spleen

List the organs and tissues of the lymphatic system.

network of lymphatic vessels:

Lymphatic capillaries

Lymphatic vessels

Lymphatic trunks

Lymphatic ducts

lymphatic tissues and organs scattered throughout body:

Lymphatic nodules

Lymph nodes

Tonsils

Spleen

Thymus

Describe the location, structure, and function of lymphatic capillaries.

• more permeable than blood capillaries

• Can withstand interstitial pressure (pressure from fluid and cells surrounding) and remain open

• epithelium functions as series of one-way valves

• Found in all parts of the body except:

   Nervous system, bone marrow, and avascular tissues (cartilage,

  cornea, epidermis)

• Lymph flows from capillaries into the larger lymphatic vessels.

Explain how lymph is formed

lymph: Interstitial fluid that leaves the blood capillaries and is taken up by the lymphatic capillaries

Travels through the lymphatic vessels until it returns to the circulatory system via the veins

formed: fluid moves from blood capillaries into tissues. most is returned to the blood capillaries but remainder moves from the tissues into highly permeable lymphatic capillaries to form lymph

• overlap of epithelial cells of lymphatic capillary allows easy entry of intersitial fluid but prevents movement back into tissue. The valves ensure one-way flow of lymph

explain how lymph transported through lymphatic vessels

Contain valves that ensure the one-way flow of lymph:

• Contraction of lymphatic vessel smooth muscle- contraction pushes lymph forward

• skeletal muscle contraction- squeezes nearby lymphatic vessels

• thoracic pressure changes- when we inhale → pressure in chest decreases → pulls lymph towards heart

Lymph in the lymphatic vessels is filtered by the lymph nodes distributed along vessels

lymph in the lymphatic vessels is delivered into one of the lymphatic trunks

-jugular, subclavian, bronchomediastinal, intestinal, lumbar

Distinguish between the thoracic duct and right lymphatic ducts (indicating where lymph from

different regions of the body would drain).

Lymph is delivered from the lymph trunks into one of two large ducts:

 Drain tissues of body and move lymph back into venous system

• right lymphatic duct: drains lymph from the right upper arm and the right side of the head and thorax

• thoracic duct: arises from the cisterna chyli and drains lymph from the rest of the body

Describe the structure and function of tonsils

• Simplest lymphatic organs

• lymphatic nodules in nasopharynx and oral cavity

palatine tonsils: posterior end of oral cavity

lingual tonsils: base of the tounge

pharyngeal tonsils: reffered to as adenoids, posterior eall of nasopharynx, usually the tonsils removed

Epithelial tissue overlying tonsil masses invaginates,

forming blind-ended crypts.

 Crypts trap and destroty bacteria and particulate matter

describe the structure and function of lymph nodes

Embedded in connective tissue and clustered along lymphatic vessels

Aggregations of these nodes occur near the body surface in inguinal, axillary, and cervical regions of body

as lymph moves through sinuses, phagocytic cells remove foreign substances

Consist of afferent (carries in) and efferent (carries out) vessels.

• filtration: only structures that filter lymph, Macrophages destroy microorganisms and debris

• immune system activation: Simulate lymphocytes to proliferate, Monitor for antigens and mount an attack against them

• germinal centers: sites of lymphocyte production

describe the structure and function of the spleen

Located on the left superior side of the abdomen.

Filters the blood.

• white pulp: Associated with arteries, Contains mostly lymphocytes suspended on reticular fibers and is involved in immune function

• red pulp: Associated with veins, Remaining splenic tissue concerned with disposing of worn-out of non-functional RBC’s and blood borne pathogens

describe the structure and function of the thymus

Bilobed organ.

Secretes the hormones thymosin and thymopoietin:

Both cause T lymphocytes to become immunocompetent

size of thymus varies with age- found in inferior neck in infants and extends into mediastinum, stops growing during adolescence and then gradually atropthies

differs from other lymphatic organs in two important ways: Functions strictly in T lymphocyte maturation., Does not fight antigens directly.

stroma of thymus: Consists of star-shaped epithelial cells (not reticular fibers).

thromocytes: Secrete the hormones that stimulate lymphocytes to become immunocompetent

Define the concepts of specificity and memory as they apply to immunity.

The ability to resist the harmful effects of microorganisms and other foreign substances.

• Innate immunity (nonspecific resistance)- does not show specificity or memory, Recognizes general foreign substances and launches a general attack

• adaptive immunity (specefic)- Exhibits specificity and memory, Recognizes specific foreign substances and produces long-term protection

Distinguish between the general characteristics of innate immunity and adaptive immunity

innate:

• provides immediate defense against infection but does not confer long-lasting immunity to host

• function: recruits immune cells to sites of infection and inflammation

• activation of the complement cascade

• activation of the adaptive immune system

• consists of physical barriers: skin and mucosa prevent entry of microorganims, tears saliva, cilia, and mucus remove microorganisms

adaptive:

• recognizes specefic foreign substances

• acts to immobilize, neutralize, or destroy foreign substances

• amplifies inflammatory response

• antigen-specefic, systemic, and has memory

• includes two overlapping but seperate arms: antibody-mediated immunity and cell-mediated immunity

Describe the components of innate immunity (cells, chemical mediators)

chemical mediators: promote phagocytosis and inflammation

cells:

• white blood cells: must be able to move into infected tissues and destroy infection

• chemotaxis: ability of white blood cells to move to tissues that release certain chemicals, attract other cells

• phagocytosis: ingestion and destruction of materials by endocytosis

• neutrophils: small phagocytic cells, first to enter infected tissue and last only a few hours

• macrophages: large phagocytic cells, monocytes that leave blood and enter tissues

• eosinophils: release enzymes that reduce inflammation

• natural killer cells (T lymphocytes): lyse tumor cells and virus infected cells

• basophils and mast cells: promote inflammation when activated by immune system when first get an infection, attracts other cells with inflammation response, basophils are motile, mast cells are non-motile

Describe the components of innate immunity (complment cascade)

• the innate immune system activates the complement cascade to remove foreign microorganisms

• Each complement pathway involves a cascade in which compliment proteins are activated in an orderly sequence resulting in cell lysis, phagocytosis, and inflammation

• Main functions:

  • amplifies all aspects of the inflammatory response

  • promotes phagocytosis

• both innate and adaptive immunity can activate complement cascade by either the classical or alternative pathways

List the events of the inflammatory response

• tissue injury regardless of type can cause inflammation

• response is initiated by chemical mediators:

  • cause vasodilation and increased vascular permeability → easier for fluid to leave which causes swelling in the body

  • chemotaxis → WBC’s attract more WBC’s, chemical mediators attract phagocytes

  • chemical mediators and phagocytes increase in numbers until the cause of the inflammation is destroyed

  • the tissue then undergoes repair

distinguish between local and systemic inflammation

local inflammation:

• confined to a specific area

  • redness

  • heat (^ and heat both due to vasodilation → increases blood flow)

  • swelling (increased permeability in vessels → fluid leaving vessels)

  • pain

  • loss of function

systemic inflammation

• occurs in many parts of body

• same symptoms as local as well as:

  • increased neutrophils

  • fever

  • shock

Describe the purpose of the complement cascade.

• amplifies all aspects of the inflammatory response

• promotes phagocytosis

• both innate and adaptive can activate complement cascade

Define antigen and describe the two groups of antigens.

• antigen: large molecules that stimulate a response (antibody formation) from the adaptive immune system

• foreign antigens (non-self antigens): antigens not produces by the body (self-antigens), bacteria, viruses, other microorganisms

• self- antigens: These are normal molecules from your own body cells, immune system does not attack them

Describe the location of the origin and maturation of B and T lymphocytes.

B lymphocytes:

• responsible for antibody-mediated immunity

T lymphocytes:

• involved with cell-mediated immunity

origin and development of lymphocytes:

• B cells and T cells originate in red bone marrow from hemocytoblasts and then move to primary lymphatic organs

  • B cells are processed in red bone marrow

  • T cells are processed in the thymus

• B and T cells then move to secondary lymphatic tissues and organs from their processing sites

  • continually circulate from one lymphatic tissue to another

positive and negative selection lymphocytes

• positive:

  • ensures survival of lymphocytes that can react against foreign antigens

  • proliferate and form clones

• negative selection

  • eliminates lymphocytes that react against self-antigens → get rid of ones that attack self

Define antibody-mediated immunity and cell-mediated immunity and name the cells responsible for each

antibody- mediated:

• B cells

• Effective against extracellular antigens including bacteria, viruses, protozoans, fungi, parasites, and toxins when they are outside cells

• antibody production: primary response and secondary response

cell-mediated:

• t cells: Most effective against intracellular microorganisms: viruses, fungi, intracellular bacteria, parasites

• cytotoxic T cells function in two ways:

  • lyse (burst cell on contact) virus-infected cells, tumor cells, and tissue transplants

  • produce cytokines: promote phagocytosis and inflammation

• memory cells produced

Recognize the mechanisms antibodies utilize to neutralize antigens

• antibodies can:

• - bind to antigen and interfere with activity

• bind antigens together,

• activate complement cascade

• facilitate phagocytosis

• initiate release inflammatory chemicals

Discuss the primary and secondary responses to an antigen and explain the basis for long-lasting

immunity.

• antibody production:

  • primary response: results from the first exposure to an antigen. (B cells proliferate to produce plasma cells (which produce antibodies) and memory B cells

  • secondary response: results from later exposure to same antigen (memory B cells divide rapidly to form plasma cells and additional memory B cells), faster, amplified response

Explain the four ways that adaptive immunity can be acquired.

• immunization: deliberate exposure to antigen or antibody

active immunity: immunity provided by the individuals own immune system

• active natural immunity: natural exposure to an antigen (others have flu, we get flu)

• active artificial immunity: deliberate exposure to an antigen through a vaccine

passive immunity: immunity transferred from another person or an animal

• passive natural immunity: transfer of antibodies from mother to her fetus

• passive artificial immunity: transfer of antibodies from an immune animal to a non immune one (ex: covid)