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
- 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
- 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.
- 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.
- 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
- 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.
- 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 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
- 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
- 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
- neutrophils: they wander in connective tissue killing bacteria, they create killing zones. they are responsible for respiratory burst that creates toxic chemicals
- Eosinophils: they stand guard against parasites, allergens and other pathogen
- 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
- 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.
- 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 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
- 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
- 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 :
- loss of function
- 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
- 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.