The Lymphatic and Immune System bulleted.

The lymphatic and Immune System

  • maintains fluid balance and protect the body from infectious diseases.
  • it continously filters from the blood capillaries into the tissue spaces
  • for our protection (immunity) it picks up excess fluid, it picks up foreign cells and it picks up Chemicals from the tissues
  • the lacteals in the small intestine absorb dietary lipids that are not absorbed by the blood capillaries

The Lymph: appearance: clear, colorless fluid

  • lymphatic vessessls: transport the lymph
  • lymphatic tissues: composed of aggregates of lymphocytes and macrophages that populate many organs in the body
  • lymphatic organs: defense cells are especially concentrated in these organs: separated from surrounding organs by connective tissue capsules.

lymph and the lymphatic vessels

  • cells tethered to surrounding tissue by protein in filaments
  • gaps between cells are large enough to allow bacteria and cells to enter lymphatic capillary

lymphatic vessels

    Two collecting ducts:

  • The right lymphatic Duct: receives lymph from right arm, right side of head and thorax: empties into right subclavian vein
  • thoracic duct: larger, longer, it begins at a prominent sac in the abdomen called the cisterns chyli. It receives lymph from the left side, below the diaphragm: left arm, left side of head, neck and thorax and empties in the left subclavian vein.
  • the subclavian vein: is the collecting point for the thoracic duct

What make the lymph flow

  • the lymph flows under similar forces to those that governs venous return, except no pump (the heart is the pump (not involved )).
  • flow aided by skeletal muscle
  • arterial pulsation rhythmically squeezes lymphatic vessels
  • valves prevents back flow

Lymphatic vessels

  • the natural killer (NK) cells: they are the surveillance department
  • the T lymphocytes (T Cells) take their time to mature in the thymus
  • the B lymphocytes (B Cells), these are plasma cells that produces antibodies
  • the Macrophages: develop from monocytes, they phagocytize (ingest) tissue debris, dead neutrophils, bacteria, and other foreign matter

the dendritic cells

  • mobile antigen presenting cells (APCs) found in the epidermis, mucous membranes and lymphatic organs

the lymphatic tissues

  • the lymphatic (lymphoid) tissue-aggregations of lymphocytes in the connective tissues of mucous membranes and various organs
  • diffuse liymphatic tissu : prévalent in body passages open to the exterior: these are the respiratory tracts, the digestive tracts, urinary tracts, and the reproductive tracts
  • in the ileum the distal portion of the small intestine, you will find a dense cluster called Peyer Patches another lymphatic tissue.

Lymphatic Organs

  • primary lymphatic organs these are the red bone marrow and the thymus.
  • at these sites the T and B cells become immunocompetent:meaning, they are able to recognize and respond to antigens
  • the secondary lymphatic organs are the lymph nodes, tonsils and spleen

the red bone marrow, the yellow bone marrow

  • the red bone marrow is involved in hemopoiesis (blood formation) and immunity, because it produces blood it contains hematopoietic tissues.
  • the yellow bone marrow is mainly made up of fat cells but, if the body needs more red marrow, this yellow marrow can be transformed.

the thymus

  • thymus is a member of the endocrine, lymphatic and immune systems: it degenerates with age
  • it has it own system, the reticular epithelial cells seal off the cortex from the medulla forming the blood-thymus barrier

lymph nodes

  • these are the most numerous lymphatic organs, very large in numbers but, they have two functions
  • Function 1: cleanse the lymph
  • Function 2: act as a site for T and B cells activation.

the lymph nodes names and location

  • Cervical lymph nodes they receive lymph coming from the head and neck
  • axillary lymph nodes they receive lymph coming from the upper lymph and female’s breast
  • thoracic lymph nodes they receive lymph from the mediastinum, lungs and airway
  • inguinal lymph nodes receive lymph coming form the groin and the the entire lower limb
    If your lymph nodes becomes swollen, painful from to foreign matter, this called lymphadenitis.
    If you are interested in studying the lymph node diseases the collective term for all lymph node diseases is called, Lymphadenopathy

the lymph nodes and metastatic cancer

  • metastasis is a phenomenon in which cancerous cells break free form the original, primary tumor, travel to other sites in the body and establish new tumors
  • tend to lodge in the first lymph node they encounter
  • then multiply and eventually destroy the lymph node
  • upon destruction, the lymph node will appear swollen, firm and they are usually painless
  • after each encounter is destroyed by metastasis the spread continues
    If diagnosed with breast cancer, treatment include lumpectomy/mastectomy along with removal of nearby axillary nodes.

the tonsils

  • these are patches of lymphatic tissues located a the entrance to the pharynx
  • they guard against ingested or inhaled pathogens
  • palatine tonsils a pair found at posterior margin of oral cavity, these are most often infected.
  • lingual tonsils found a the root of the tongue
  • pharyngeal tonsils-adenoids: single tonsils on wall of nasopharynx

the spleen

  • the spleen is the body’s largest lymphatic organ, it contains the:
  • Red pulp: these are sinuses filled with erythrocytes.
  • White pulp: these are lymphocytes, macrophages surrounding small branches of splenic artery: monitor blood for foreign antigen
  • other than those amazing functions it does something even better, it produces blood in the fetus, it also serves a blood reservoir and a graveyard for red blood cells disposal)
  • the spleen is high vascular and vulnerable to trauma and infection, removal of the spleen is called splenectomy

Nonspecific resistance

  • the environmental agents capable of producing diseases are called pathogen
  • the first line of defense is: your external barrier, your skin and mucous membrane
  • second line of defense is: several nonspecific defense mechanisms: leukocytes and macrophages, antimicrobial proteins, immune surveillance, inflammation and fever. these are effective against a broad range of pathogens.
  • third line of defense: the immune system

external barriers

    the skin

  • Defensins found in the skin are defensive peptides that kills microbes by creating holes in the membranes
  • An acid mantle found on the skin. this is a thin film of lactic acid from sweat which inhibits bacterial growth: mucous membrane
  • it also secretes lysozyme an enzyme that destroys :bacterial cells walls.

leukocytes and macrophages

    There are 5 types of leukocytes
  1. neutrophils: they wander in connective tissue killing bacteria, they create killing zones. they are responsible for respiratory burst that creates toxic chemicals
  2. Eosinophils: they stand guard against parasites, allergens and other pathogen
  3. basophils: they secretes chemicals that aid mobility and action of other leukocytes. the leukotrienes: activates and attract neutrophils and eosinophils: the histamine is a vasodilator, which increases blood flow, speed of delivery of leukocytes to the area and: heparin: inhibits clot formation which would impede leukocyte mobility
  4. monocytes: they migrate from the blood into the connective tissue and transform into macrophages. the wandering macrophages actively seek pathogens. they are widely distributed in the loose connective tissue.
  5. lymphocytes: they circulate the blood continuously.


  • interferons are secreted by certain cells infected by viruses: no benefit to the cell: they alert neighboring cells and protect them from becoming infected: binds to surface receptors on neighboring cells.

complement system

    • complement system synthesized mainly by the liver
    • circulate in the blood in inactive form
    • activated by presence of the pathogen

route of complement activation.

  • classical pathway: requires antibody molecule to get started
  • alternative pathway: nonspecific, does not require antibody

immune surveillance

  • natural killer (NK) cells continually patrol the body on the look out for pathogens and disease host cells to attack and destroy.
  • NK attack and destroy bacteria, cells of transplanted organs, cells infected with viruses and cancer cells
  • NK recognizes enemy cells: binds to it: release proteins call performs: polymerize a ring and create a hole in its plasma membrane: secretes a group of protein-degrading enzymes-granzymes: enters through the pores and degrade cellular enzymes and induce apoptosis


  • an abnormal elevation of body temp (pyrexia, febrile)
  • it is an adaptive mechanism that, in moderation does more good than harm
  • antipyretics: fever reducing medication

Reye syndrome

  • Serious disorder in children younger that 15 following an acute viral infection such as chicken pox or influenza
  • can be triggered by the use of aspirin to control fever
  • never give aspirin to children with chickenpox or flulike symptoms


  • 5 cardinal signs of inflammation :
  1. redness
  2. swelling
  3. heat
  4. pain
  5. loss of function

mobilizing defenses

  • hyperemia: increasing blood flow beyond normal rate is a way to do this: it washes toxins and metabolic wastes from the site more rapidly
  • heat: results form hyperemia
  • redness: due to hyperemia and extravasated RBC in the tissue
  • Swelling (edema): due to increased fluid filtration from the capillaries
  • pain: from direct injury to the nerves, pressure on the nerves from edema stimulation of pain receptors by prostaglandins, bacterial toxins and a kinin call bradykinin.


    The chief enemy of bacteria

  • neutrophilia: increase in neutrophils:
  • neutropenia: decrease in neutrophils
  • eosinophilia: increase in eosinophils

Forms of immunity

  • natural active immunity: production of one’s own antibodies or T cells as a result of infection or natural exposure to antigen
  • artificial active immunity: production of immunity from vaccination against diseases (vaccines/booster shots)
  • natural passive immunity: temporary immunity that results from antibodies produced by another person (mother to child)
  • artificial passive immunity: temporary immunity that results from the injection of immune serum (antibodies) form another person or animals (snake bites)


  • are, any molecule that triggers an immune response
  • epitopes: antigenic determinants: stimulate immune response
  • happens: too small to be antigenic in themselves, must combine with host macromolecule


    Three Categories

  • Natural Killer Cells (NK): immune surveillance
  • T lymphocytes (T Cells): born in the red blood marrow, mature in the thymus: has to recognize RE cells and react to the self antigen not attach their own tissues: 2% that reaches the thymus are immunocompetent: 98% are destroyed and recycled
  • b lymphocytes (B cells): attached to antibodies

Cellular Immunity

  • cytotoxic T cells (Tc cells): killer T cells: carries out attack on enemy cells
  • Helper T cells (Th cells): promote Tc cells and B cell action and nonspecific resistance
  • Regulatory T (Tr) cells. T-regs: inhibit multiplication and cytokine secretion by other T cells: limit immune response
  • Memory T (Tm) Cells: response from memory in cellular immunity.


  • IgA: provides passive immunity to newborns
  • IgE: stimulates release of histamine: produces immediate hypersensitivity reactions
  • IgG : cross placenta to fetus
  • IgM: secreted in primary immune response


  • primary immune respons: IgM response first, peaks about 10 days, then soon decline
  • IgG levels rise as IgM declines, but IgG titer Drops to a low level within a Month.


There are four kinds of hypersensitivity:

  • type 1: acute: immediate hypersensitivity: very rapid: includes most common allergies: IgE mediated reaction that begins with second exposure
  • type 2 and 3: sub-acute hypersensitivity: slower: onset: (2) antibody dependent cytotoxic. (2)blood transfusion reaction. (3)auto-immune complex
  • type 4: delayed cell mediated response: cells mediated reaction in which signs appear 12-72 hours after exposure
      Anaphylactic shock-antihistamines are inadequate, epinephrine receives the symptoms.


      Asthma : most common chronic illness in Children.

that concluded the overview for Lymphatic and Immune system, taken from Anatomy and Physiology seventh edition by Saladin.

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