compendium 10 Flashcards
Functions of the Lymphatic System
Fluid balance
Excess interstitial fluid enters lymphatic capillaries and
becomes lymph (30L from capillaries into interstitial fluid,
27L return into venous circulation in CDVS leaving 3L, called lymph).
Fat absorption
Absorption of fat and other substances from digestive
tract via lacteals. lipids enter lymphatic circulation before they enter digestive.
Defense
Lymphatic system – fights infection. Microorganisms
and other foreign substances are filtered fro
Anatomy of the Lymphatic System
Lymph Lymphatic vessels Lymphatic tissue Lymphatic nodules Lymph nodes Tonsils Spleen Thymus
Lymph
fluid found in lymphatic system
Water plus solutes from two sources
Plasma: ions, nutrients, gases, some proteins
Cells: hormones, enzymes, waste products
Returns to circulatory system via veins; essential for fluid balance.
if that 3L of fluid is left in that interstitial space to accumulate - quite dangerous/ deadly, effect on brain, heart, lungs etc..
Lymphatic Vessels
Carry lymph away from tissues
Lymphatic capillaries
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
very small blind-ended capillaries pick up fluid
Lymphatic vessels: have valves that ensure one-way flow
(beaded appearance)
Lymph nodes: distributed along vessels and filter lymph
Lymphatic trunks: jugular, subclavian, bronchomediastinal,intestinal, lumbar
vessels combine to form trunks
Lymphatic ducts: drain tissues of body and move lymph into
major veins
——- Right lymphatic duct: drains right side of head, right-upper limb, right
thorax
——- Thoracic duct: drains remainder of the body
Lymphatic Tissue and Organs
Lymphatic organs contain lymphatic tissue
(lymphocytes, macrophages, dendritic cells)
Lymphocytes: B & T cells - white blood cells derived frombone marrow. - main role to protect the body form foreign antigens or invading microorganisms. T manage immune response and directly kill lymphocytes and B make antibodies
macrophages
Fine network of reticular fibers. Produced by reticular cells.
Act as filter to trap microorganisms and other particles
lymphoid tissue 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.
lymphoid tissue further charaterised as
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.
Lymph Nodes
Only structures to filter lymph
Substances removed by phagocytosis or stimulate
lymphocytes to proliferate.
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 carries lymph into node and efferent vessels carries lymph out
Organized into cortex and medulla with dense
connective tissue capsule surrounding.
Tonsils
Large groups of lymphoid tissue in nasopharynx and oral cavity Provide protection against bacteria and other harmful material. covered in squamous epithelium and traps Palatine (tonsils) - most commonly affected by tonsilitis Pharyngeal (adenoids) Lingual
spleen - largest lymphoid organ
blood enters the spleen via the splenic artery where it is filtered and then exists out splenic vein
The parenchyma of the spleen is connective tissue (mostly lymphocytes and other blood cells) is divided into white pulp and left pulp.
Red pulp associated with veins (75%) – Fibrous network of
macrophages and RBCs.
White pulp associated with arteries (25%) – lymphatic tissue.
Functions
Monitors blood, detects, and responds to foreign antigens.
Destroys defective red blood cells
Regulates blood volume by transferring excess blood plasma into the circulatory system
– highly vascular
Limited reserve of RBC
Can be ruptured in traumatic abdominal injuries.
Splenectomy - removing it so not too much blood is lost
Thymus
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
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.
Non-hodgkins lymphoma – any cancer of lymphoid tissue –
except Hodgkins’s. Can effect cells, nodes or organs. Young
vs Old.
Bubonic plague (The Black death) – severe bacterial infection
(fleas/rats), enlarged lymph nodes, septicemia.
pathogens and antigens
Pathogen – foreign agents
- protozoa, worms, toxins, viruses, fungi, prions, bacteria
- antigens are on pathogens
• 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
Immunity
- Ability to resist damage from foreign substances and internal threats
- Can distinguish between “self” and “non-self”
- External – micro-organisms e.g. bacteria, virus, fungi, toxins
- Internal – cancer cells that starts expressing proteins that it shouldn’t normally express
- Categories
- Innate or nonspecific immunity - doesn’t recognise the particular pathogen that its fighting just that its a pathogen and it shouldn’t be there
- Adaptive or specific immunity - recognises specific pathogen and mounts a specific response
- Innate and adaptive immunity are fully integrated in the body
Immune system vs. lymphatic system
Lymphatic system
• 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”
Immune system
• Collection of proteins, cells, tissues and organs widely distributed
throughout the body
Immune system vs. lymphatic system
Lymphatic system
• 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”
Immune system
• Collection of proteins, cells, tissues and organs widely distributed
throughout the body
Innate immune system
• Non-specific defense, 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 defense are external features
• Physical barriers
• Second line of defense
• Chemical mediators
• White blood cells (phagocytes)
• Inflammation
• Fever
Innate Immunity:
1. Physical Physical barriers - prevent entry or remove microbes • Skin • Mucous – esp. respiratory passageways • Saliva • Tears • Acid in stomach, urinary tract, vagina • Urine flushes urinary passageways • Cilia in respiratory tract, coughing and sneezing
- Chemical mediators
Chemical mediators – promote phagocytosis & inflammation
• Promote inflammation
• E.g. histamine
• Cause vasodilation, increased vascular permeability, attract white blood
cells, stimulate phagocytosis
• Cytokines
• Secreted by one cell, and stimulates a neighbouring cell to respond
• Regulate intensity and length of immune response
• Complement – stimulate lysis of invading pathogen cells
• Interferons – anti-viral activity - white blood cells
• 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
• Neutrophils
• First cell to arrive at a site of insult
• Macrophages
• Most effective phagocyte, important in later stages of inflammation & repair
• Help activate cells of the specific immune system
• Basophils, Eosinophils, Natural Killer Cells - Inflammation
• Local tissue response to damage
• Pathogens
• Cuts & abrasions
• Aims to
• rid body of debris/invader
• Prevent further pathogen entry
• Four features of inflammation
• Redness - increased blood flow to region
• Heat - increased blood flow to region
• Swelling - capillaries become leaky (increased permeability) fluid present
fluid leaves capillaries – surrounding tissue
• Pain - increased fluid stimulates pain receptors, chemical
released by cells can also stimulate pain receptors - Fever
• 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
• Increase some antimicrobial substances
• Decrease microbial growth
• Increase body reactions that help tissue repair
Adaptive Immunity
• 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
• Lymphocytes (clone of lymphocytes) must recognize antigen
• After recognition, lymphocytes must increase in number to destroy
antigen
• Helper T cells
• Effector (cytotoxic/killer) T cells
• B cells
Cell-mediated Immunity
• T lymphocytes • Helper T cells • 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
- Causes cells to explode
Form memory cells - if the same antigen re-appears, the
response will be faster (memory)
Most effective against intracellular pathogens
antibody-mediate 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 • Plasma cells – make antibodies • Memory B cells – if the same pathogen(antigen) is encountered again, the response is much faster
antibody production
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.
Immune system dysfunction - 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 impairs 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
• Long incubation period, and initially low incidence rate
• Initially reported mainly the gay community, IV drug users, people who received blood
transfusions
HIV - AIDS
• Body is vulnerable to microbial invaders
• Ordinarily harmless microorganisms can cause lethal infections
• Pneumocystis pneumonia
• TB, syphilis
• candidiasis
• Increased risk of cancer – Karposi’s sarcoma
• Infection due to intimate contact with body fluids of infected people
Treatment
When first described no treatment available
• HIV pretty much considered a “death sentence” (see Grim Reaper ad, Australia, 1987)
1. control HIV replication
• Highly active anti-retroviral therapy (HAART)
• Can live for many years
• Chronic disease rather than death sentence
2. manage secondary infections/malignancies
