How do we protect ourselves? Flashcards
What are the functions of the lymphatic system?
Functions of the Lymphatic System
-Fluid balance
o Excess interstitial fluid enters lymphatic capillaries and becomes lymph (30L from capillaries into interstitial fluid, 27L return leaving 3L, called lymph).
-Fat absorption
o Absorption of fat and other substances from digestive tract via lacteals.
-Defence
o Lymphatic system – fights infection. Microorganisms and other foreign substances are filtered from lymph by lymph nodes and from blood by spleen.
Name the anatomy of the lymphatic system
- Lymph
- Lymphatic vessels
- Lymphatic tissue
- Lymphatic nodules
- Lymph nodes
- Tonsils
- Spleen
- Thymus
What is Lymph?
-Water plus solutes from two sources
o Plasma: ions, nutrients, gases, some proteins
o Cells: hormones, enzymes, waste products
-Returns to circulatory system via veins; essential for fluid balance.
What is the function of the lymphatic vessels?
-Carry lymph away from tissues
-Lymphatic capillaries
o More permeable than blood capillaries Epithelium functions as series of one-way valves Found in all parts of the body except nervous system, bone and avascular tissues (without blood vessels - cornea, epidermis).
-Lymphatic capillaries join to form lymphatic vessels
-Lymphatic vessels: have valves that ensure one-way flow (beaded appearance)
-Lymph nodes: distributed along vessels and filter lymph
-Lymphatic trunks: jugular, subclavian, Broncho mediastinal, intestinal, lumbar
-Lymphatic ducts: drain tissues of body and move lymph into major veins
o Right lymphatic duct: drains right side of head, right-upper limb, right thorax
o Thoracic duct: drains remainder of the body
What are the lymphatic tissues & organs?
-Lymphatic organs contain lymphatic tissue (lymphocytes, macrophages, dendritic cells)
o Lymphocytes: B & T cells - white blood cells derived from bone marrow.
o Fine network of reticular fibres. Produced by reticular cells. Act as filter to trap microorganisms and other particles
o May be encapsulated (in a CT capsule)
- Encapsulated- lymph nodes, spleen, thymus
- Nonencapsulated- mucosa-associated lymphoid tissue (MALT). Found beneath epithelium as first line of attack against invaders.
What is diffuse lymphatic tissue & lymphatic nodules?
- Diffuse lymphatic tissue: dispersed lymphocytes, macrophages; blends with other tissues.
- Lymphatic nodules: denser aggregations. Numerous in loose connective tissue of digestive (Peyer’s patches), respiratory, urinary, reproductive systems.
What are lymph nodes, what do they remove and what are they organised into?
-Only structures to filter lymph
-Substances removed by phagocytosis or stimulate lymphocytes to proliferate.
o Cancer cells often migrate to lymph nodes, are trapped there, and proliferate. Can move from lymphatic system to circulatory system spreading cancer through the body.
-Afferent and efferent vessels
-Organized into cortex and medulla with dense connective tissue capsule surrounding.
What are the parts and function of the tonsils?
-Large groups of lymphoid tissue in nasopharynx and oral cavity
-Provide protection against bacteria and other harmful material.
o Palatine (tonsils)
o Pharyngeal (adenoids)
o Lingual
What are the functions of the spleen, what are red pulp associated with & what are white pulp associated with?
-Red pulp associated with veins (75%) – Fibrous network of macrophages and RBCs.
-White pulp associated with arteries (25%) – lymphatic tissue.
Functions
o Monitors blood, detects and responds to foreign antigens.
o Destroys defective red blood cells
o Regulates blood volume
o Limited reserve of RBC
-Can be ruptured in traumatic abdominal injuries.
-Splenectomy.
What is the thymus the site of and what is its location?
- Located in superior mediastinum.
- Cortex (numerous lymphocytes) and medulla (fewer lymphocytes)
- Site of maturation of T cells: many T cells produced here, but most degenerate.
- Those that remain can react to foreign substances.
- Endocrine functions.
What is tonsillitis, lymphoma & hodgkins disease as disorders?
- Tonsillitis – Inflammation of the tonsils – bacterial infection.
- Lymphoma – cancer (benign or malignant) of the lymphoid tissue or cells, often begins in the lymph nodes, immune system suppressed.
- Hodgkin’s disease – Malignancy in lymphoid tissue (malignant B cells). Chemotherapy /radiation
What is Non-hodgkins lymphoma & Bubonic plague as disorders?
- Non-Hodgkin’s lymphoma – any cancer of lymphoid tissue – except Hodgkin’s. Can affect cells, nodes or organs. Young vs Old.
- Bubonic plague (The Black death) – severe bacterial infection (fleas/rats), enlarged lymph nodes, septicaemia.
What is a pathogen, what do they introduce & what do antigenic receptors recognise?
- Pathogen – foreign agents
- Pathogens introduce foreign (non-self) proteins into the body called antigens
- Antigenic receptors on T cells and B cells recognize these foreign proteins as not being “self” (i.e. as being “foreign”, and aims to remove them from the body
What is immunity, what can it distinguish (internal/external) & what are the categories?
-Ability to resist damage from foreign substances and internal threats
-Can distinguish between “self” and “non-self”
o External – micro-organisms e.g. bacteria, virus, fungi, toxins
o Internal – cancer cells
-Categories
o Innate or nonspecific immunity
o Adaptive or specific immunity
-Innate and adaptive immunity are fully integrated in the body
What is the lymphatic systen?
- Transport system for cells of the immune system and antigens (foreign substances/cells) to move around the body.
- Tissues where cells of the immune system “hang out”
What is the immune system?
-Collection of proteins, cells, tissues and organs widely distributed throughout the body
What is the innate immune system, what does it provide & what this the first and second line of defence?
-Non-specific defence, present at birth
-Each time body is exposed to a substance; response is the same (i.e. has no memory)
-Provides immediate protection from pathogens & antigen
-First line of defence are external features
o Physical barriers
-Second line of defence
o Chemical mediators
o White blood cells (phagocytes)
o Inflammation
o Fever
What are physical barriers?
-Physical barriers - prevent entry or remove microbes
o Skin
o Mucous – esp. respiratory passageways
o Saliva
o Tears
o Acid in stomach, urinary tract, vagina
o Urine flushes urinary passageways
o Cilia in respiratory tract, coughing and sneezing
What are chemical mediators?
-Chemical mediators – promote phagocytosis & inflammation
o Promote inflammation
-E.g. histamine
-Cause vasodilation, increased vascular permeability, attract white blood cells, stimulate phagocytosis
o Cytokines
-Secreted by one cell, and stimulates a neighbouring cell to respond
-Regulate intensity and length of immune response
o Complement – stimulate lysis of invading pathogen cells
o Interferons – anti-viral activity
Where are WBC produced, how are they released, what do they ingest and what do they produce?
-White blood cells produced in bone marrow & lymphatic tissue
-Released into blood & transported around the body
-When a tissue is damaged it releases chemicals that attract white blood cells to a site of injury/invasion
-White blood cells ingest foreign particles – phagocytosis
-Produce chemicals to attract other immune cells to local area
-Neutrophils and macrophages are most important phagocytic cells
o Neutrophils
-First cell to arrive at a site of insult
o Macrophages
-Most effective phagocyte, important in later stages of inflammation & repair
-Help activate cells of the specific immune system
-Basophils, Eosinophils, Natural Killer Cells
In inflammation what do the local tissue respond to, what does it aim to do & what are the features?
-Local tissue response to damage
o Pathogens
o Cuts & abrasions
-Aims to
o Rid body of debris/invader
o Prevent further pathogen entry
-Four features of inflammation
o Redness= increased blood flow to region
o Heat= increased blood flow to region
o Swelling= capillaries become leaky (increased permeability) fluid leaves capillaries – surrounding tissue
o Pain= increased fluid stimulates pain receptors, chemical released by cells can also stimulate pain receptors
What is a fever in response to, what can it cause and what do high temperatures do to the body?
-Generalized response of the body to tissue damage & infection
-Common in inflammation and infection
-Can cause macrophages to release chemicals
-Body temperature abnormally high
-High temperatures
o Increase some antimicrobial substances
o Decrease microbial growth
o Increase body reactions that help tissue repair
What is adaptive (specificity & memory) immunity, what does it fight, what is it mediated by & what must lymphocytes recognise?
-Specificity - ability to recognize a particular substance
-Memory - ability to remember previous encounters with a particular substance and respond rapidly
-Acquired during lifetime, depending on exposure
-Fights invaders once innate system is over-run
-Mediated by lymphocytes (special type of white blood cell) – B & T cells
-Activation of lymphocytes
o Lymphocytes (clone of lymphocytes) must recognize antigen
o After recognition, lymphocytes must increase in number to destroy antigen
-Helper T cells
-Effector (cytotoxic/killer) T cells
-B cells
What is cell mediated immunity?
-T lymphocytes
o Helper T cells
o Cytotoxic T cells
-Activated by specific antigen
-Specific “clones” bind to antigen
-Co-stimulation required (Helper T cells)
-Activated cytotoxic T cells divide
-Eliminate antigen (pathogen)= Make holes in cell wall which causes cells to explode
-Form memory cells= if the same antigen re-appears, the response will be faster (memory)
-Most effective against intracellular pathogens
What is antibody mediated immunity?
-B cells
-Phagocytosis of an extracellular pathogen that matches the specific B cell receptor on that B cell
-Require co-stimulation by a Helper T cell that also recognizes the same pathogen (antigen)
-B cell divides to form
o Plasma cells – make antibodies
o Memory B cells – if the same pathogen(antigen) is encountered again, the response is much faster
What are the effects of antibodies?
- Inactivate the Antigen= An antibody binds to an antigen & inactivates it.
- Bind Antigens Together= Antibodies bind several antigens together.
- Facilitate Phagocytosis= An antibody binds to an antigen & then to a macrophage, which phagocytises the antibody and antigen.
In antibody production, what is the primary & secondary response?
Primary response
-When a B cell is first activated by an antigen.
-B cell proliferates to produce plasma cells (antibody production) and memory cells.
Secondary response
-Occurs during later exposure to same antigen.
-Memory cells divide rapidly to form plasma cells and additional memory cells. Faster and greater response
What happens to a cell when it has HIV?
-HIV = human immunodeficiency virus
-Virus binds to CD4 protein and infects Helper T cells
-Cells infected with HIV are ultimately destroyed by the virus or by immune response
-Gradual destruction of Helper T cells impair cell mediated and antibody mediated immunity
-Normal amounts of Helper T’s = 1200 cells/mm3
-When Helper T’s get below 200 cells/mm3
-Acquired immune deficiency syndrome (AIDS)
-Antibody levels decline, and cell mediated immunity reduced
-Believed to have spread from The Congo to Haiti to US in late 1960’s/70s
-First described by the CDC in the US in 1981
o Long incubation period, and initially low incidence rate
-Initially reported mainly the gay community, IV drug users, people who received blood transfusions
Describe the affect of HIV/AIDS
-Body is vulnerable to microbial invaders
-Ordinarily harmless microorganisms can cause lethal infections
o Pneumocystis pneumonia
o TB, syphilis
o Candidiasis
-Increased risk of cancer – Karposi’s sarcoma
-Infection due to intimate contact with body fluids of infected people
What is the treatment for AIDS?
Treatment
-When first described no treatment available
o HIV pretty much considered a “death sentence” (see Grim Reaper ad, Australia, 1987)
1. Control HIV replication
o Highly active anti-retroviral therapy (HAART)
o Can live for many years
o Chronic disease rather than death sentence
2. Manage secondary infections/malignancies
