Download Chapter 20-22 Lymphatic System

Chapter 12: Lymphatic System
2 important functions of the Lymphatic System:
1.)
fluid balance – drains the excess tissue fluid & returns proteins & fats & other substances
to venous blood before it reaches the heart – prevents swelling (edema)
2.)
immunity
The Lymphatic System is our “safety net” against disease when our 1 st line of defense is
penetrated (the skin)
- 2 types of defense:
A.)
Nonspecific Defense System – skin, tears, mucus, etc
B.)
Specific Defense System – antibodies
Lymphatic System is a specialized component of circulatory system but its vessels don’t form a
closed ring – begin blindly in intercellular spaces of the soft tissues of organs
Lymph & Interstitial Fluid
- lymph is the clear, watery fluid in lymphatic vessels
- interstitial fluid fills the spaces between the cells
both contain a lower % of proteins than blood plasma
lymph doesn’t clot, so any damage to main lymphatic vessels, lymph flow must be
stopped surgical - if not death occurs
How does interstitial fluid form?
1.)
Formed from blood plasma water & small amounts of proteins & other molecules leaking from
capillaries
How does lymph form?
1.)
Formed by interstitial fluid mixing with protein after entering the lymphatic capillaries
2.)
Made of water, protein, fat & other substances
Lymphatic Vessels
- types:
1.)
Lymphatic Capillaries – microscopic blind-ended tubes distributed in the tissue
spaces to absorb the leaked fluid
- 1 layer thick, porous
- anchored to surrounding cells by tiny filaments
- lie side by side to blood capillaries but are independent of each other
2.)
Larger Lymphatic Vessels – formed by merging lymphatic capillaries & small
lymphatics
- contains:
A.)
Right Lymphatic Duct – drains lymph from the right upper extremity (right
side of the head, neck & upper torso) into right subclavian vein
B.)
Thoracic Duct – largest – drains lymph from right lower quadrant of body
& entire left side of the body into the subclavian vein – originates from
the cisterna chyli in the lumbar region
-
structure – resemble veins except:
 have thinner walls
 contain more valves – like semilunar
 contain lymph nodes at intervals along course
-
functions – one way movement of lymph
 return fluid to blood
 return proteins & large particulate to blood
 fat & other nutrients from small intestine absorbed by lacteals (lymphatic capillaries in the
small intestines) – this milky lymph is chyle
-
circulation of lymph:
- moves slowly
- moves one-way because of the valves in the lymphatic vessels
- movement caused by:
A.)
breathing movements – most rapid at inspiration
B.)
skeletal muscle contractions – “milk” the vessels & move lymph
- increases w/ exercise
- smooth muscle in thoracic vessel helps a little
C.)
arterial pulsations
D.)
postural changes
E.)
massage of soft tissue
-
lymphatic vessel disorders:
1.)
Lymphedema – abnormal condition in which tissues exhibit swelling (edema) as a
result of the accumulation of lymph
- vessels could be blocked – could be congenital, infection (lymphangitis), parasitic
worms (elephantiasis)
2.)
Lymphangitis – characterized by thin, red streaks extending from infected region –
can spread to blood causing septicemia (blood poisoning) & death from septic shock
Lymphatic Organs:
1.)
Lymph Nodes – filters as it moves through the system
- the nodes are located in clusters (very few are singular) along the vessels – they
range in size
- functions are:
A.)
defense – will swell
B.)
some WBC formation
C.)
biological filtration – lymph flows through several afferent lymph vessels &
drains from the nodes by a single efferent lymph vessel
-
Lymph Node Disorders:
A. Lymphoma – lymphatic tissue cancer – painless enlargements of lymph
nodes in the neck, followed by anemia, weight loss, weakness, fever &
spreads to other lymphatic tissues – 2 types:
1.) Hodgkin’s Lymphoma – stays in the lymphatic tissue – contains
particular cancer cells
2.) Non-Hodgkin’s Lymphoma – can spread to other systems
2.)
Thymus – small tissue organ located in the mediastinum overlying the heart, extending
upward in the midline of the neck – plays a vital & central role in immunity by producing
T-lymphocytes – also secretes thymosin to aid in the production
3.)
Tonsils – 3 masses of lymphoid tissue located under a protective ring of mucous
membrane in the pharynx – any enlargement of the masses causes breathing problems –
the 3 masses are:
A.)
Palatine Tonsils – the “tonsils”
B.)
Pharyngeal Tonsils – the “adenoids”
C.)
Lingual Tonsils
4.)
Spleen – largest lymphoid organ – located upper left quadrant of the abdomen –
functions in the phagocytosis of bacteria& old RBCs – also a blood reservoir – can be
injured by trauma
5.)
Peyer’s Patches – resemble tonsils but are found in the small intestinal wall – captures &
destroys bacteria
Mechanisms of Disease
If you maintain good health (physical, mental & social well being) then you can prevent disease
(abnormality in body function that threatens well being)
Disease Terminology
a.) pathology – the study of disease – “pathos” = disease
b.) diagnosed – identified by signs & symptoms
c.) signs – objective abnormalities that can be seen or measured by someone other than the patient
d.) symptom – subjective abnormality felt only by the patient
e.) syndrome – collection of different signs & symptoms, usually with a common cause, that presents a
clear picture of a pathological condition
f.) acute – when signs & symptoms appear suddenly, persist for a short time, then disappear
g.) chronic – diseases that develop slowly & last for a long time
h.) subacute – characteristic between acute & chronic
i.) etiology – the study of all factors involved in causing a disease
j.) idiopathic – disease with undetermined causes
k.) communicable – disease that can be transmitted from one person to another
l.) pathogenesis – pattern of a disease’s development
m.) latent – hidden stage – in infectious diseases it is called “incubation”
n.) remission – recovery – if permanent, then it is called “cured”
Patterns of Disease
- epidemiology – the study of the occurrence, distribution & transmission of disease in humans
- if disease is native to a local region – endemic
- if it spreads to many individuals at the same time – epidemic
- epidemics in large geographic regions – pandemics
Tracking A Disease Depends On:
1.) nutrition
3.) Sanitation practices
2.) age
4.) socioeconomic conditions
5.) gender
Strategies for Combating Disease:
1.)
Therapy & Treatment
2.)
Prevention – vaccination & education
Organization of the Immune System:
1.) Nonspecific Immunity – act against anything that is not
recognized as “self” – more general defense
- fast response immunity
- mechanisms are:
a.)
species resistance – our internal envir. is not suitable for certain pathogens – we
can’t get distemper or plant diseases
b.)
mechanical & chemical barriers – skin, mucus (traps pathogens), sebum (contains
pathogen inhibitors), enzymes (hydrolyze pathogens) & HCl (inflicts acid burns) –
1st line of defense
c.)
inflammatory response – isolates pathogens to speed up recovery
d.)
neutrophils (1st to show up at sight – most numerous, form pus when they die),
monocytes & macrophages – phagocytize (engulf) the pathogen
e.)
natural killer (NK) cells – grp of lymphocytes that kill different types of tumor
cells & virus-infected cells
f.)
interferon – protein produced by cells after being infected by virus to prevent
the spread of the virus
g.)
complement – grp of plasma proteins that produce chemical rxns when activated
to cause lysis of foreign cell
Inflammatory Response
- a combination of processes that attempt to minimize injury in order to maintain homeostasis
- responds to tissue injury including cuts, burns, radiation, chemicals, toxins or immune reactions
- 4 primary signs of inflammatory response
A.) redness
B.) swelling
C.) heat
D.) pain
inflammatory response process steps:
1.) irritant enters the tissue
-
2.) tissue damage occurs
3.) inflammation mediators are released
ex.) histamine (inc. capillary permeability & vasodilation), kinins (inc. capillary permeability,
vasodilation, chemotaxin, stimulates complement system), prostaglandins (cause fever, enhance
pain), leukotrienes (released by WBCs to coordinate tissue response)
4.) blood vessels dilate to increase blood flow, blood vessel walls increase permeability, leukocytes
move in response to the chemical attractants (chemotaxis)
5.) increases #s of leukocytes & mediators at damage site
6.) irritant is contained, destroyed & phagocytized
No irritant remains
7.)
Tissue Repair
Irritant remains
Additional mediators
activated & process starts
over
2.) Specific Immunity – recognizes specific agents that are “not-self”
- needs extra time for recognition & rxn
- involves memory
- mechanisms are:
a.)
B cell lymphocytes – antibody-mediated immunity (or humoral immunity)
- produce antibodies
- can attack pathogens directly or direct phagocytes to attack
b.)
T cell lymphocytes – cell-mediated immunity
- attack pathogens directly
-
surface markers – proteins on the surface of lymphocytes that distinguishes them from
other cells – how they are named
-
most lymphocytes are located:
1.) bone marrow
3.) lymph nodes
2.) thymus
4.) spleen
-
Specific immunity terminology
a.)
antigen – large molec. that induces immune response
b.)
antigenic determinants (epitopes) – portion of the antigen that the lymphocyte
recognizes as foreign
c.)
antibodies – large protein molec. that interlock w/ & destroy antigens
d.)
combining sites – antigen receptor sites on antibodies – are specific shapes
e.)
antigen-antibody complex – antibody antigen receptor attached to the antigen
determinant
f.)
clone – a grp (family) of cells from one original cell
g.)
complement – grp of plasma proteins that work together to destroy foreign cells
B-Cell Development – stands for “bursae”
1st stage:
 inactive B cells are dvlpd by the time you are several mths old
 inactive B cells produce antibodies & insert them on the cells surface – surface antibody
combining sites become antigen receptors
 once released by bone marrow, inactive B cells circulate to lymph nodes & spleen
2nd stage:
 inactive B cells become activated by its specific antigen – producing antigen-antibody
complex of the B cell plasma membrane
 rapid B cell division is triggered producing clones of this cell
 some of the new cells become plasma cells that secrete antibodies
 others become memory B cells – if exposed again will become plasma cells
Antibody Structure: belong to family called immunoglobulins
- each is made of 4 polypeptides - 2 heavy chains & 2 light chains
- forms a “Y” shape
- has 2 variable regions formed by 2 branches of the “Y” – the antigen-binding sites
- has a constant region formed by the base of the “Y” – the complement-binding site
Antibody Diversity: produced:
1.) somatic recombination hypothesis – states that the genetic code is a set of separate sequences
that are assembled into whole genes as B cells dvlps – so the code for a specific antibody is
produced by a combination of genes
2.) gene mutation – slight changes in the DNA code result in slight differences in the variable
region of antibodies
3.) elimination of “anti-self” B cells early in dvlpt so we don’t have autoimmune disease
Classes of Antibodies: - named immunoglobulin _?_ (Ig)
1.) IgM – produced by immature B cells & inserted into plasma membrane, also produced by
activated B cells after contact w/ antigen
2.) IgG – makes up 75% of the circulating antibodies – produced by 2° antibody response
3.) IgA – produced in mucous membrane, saliva & tears
4.) IgE – associated w/ allergies
5.) IgD – found on surface of B cells – probably function as antigen receptors that help initiate
differentiation of B cells into plasma cells & memory B cells
Functions of Antibodies:
1.) Antigen-antibody reactions – effects are:
A.)
Neutralization – deactivates the toxins making the antigen harmless
B.)
Agglutination – sticks to antigens & clumps them together
C.)
Changes the shape of the antigen molec. surface to expose the complement-binding
site
2.) Complement – series of 20 plasma enzymes
- are activated when they contact the antigen’s complement-binding site
- complement activations occur in which a hole is drilled into the antigen’s cell surface
- ions & H2O rush into the antigen, it swells & burst (cytolysis)
- the complement cascades could also occur by nonspecific immune mechanisms – “alternate
pathway”
3.) Clonal Selection theory – the body contains diverse # of clones of cells,
each committed to make a certain antibody
- by selecting the lymphocytes w/ the complementary receptors, each antigen provokes its
own destruction
T-Cell Development:
- dvlp & multiply in the thymus (thymocytes)
- leave thymus & migrate to T-dependent zones in lymph nodes & spleen
Activation of T-Cells – steps are:
1. antigen binds to T-cell antigen receptors
2. macrophage processes the antigen and then presents the antigen to antigen receptors on the T-cell
3. T-cell is activated (sensitized T-cells)
4. T-cell divides repeatedly forming a clone of identical sensitized T-cells – they may form into:
a.) cytotoxic T-cells – cause contact killing of a target cell
b.) T memory cells – produce antibodies
5. the sensitized T-cells migrate to site of antigen
6. bind to processed antigen presented by macrophage
7. releases cytokinins into inflamed tissues – these chemical messengers are:
a.)
chemotactic factors – attracts macrophages
b.)
migration inhibition factor – halts macrophage migration
c.)
macrophage-activating factor – increases phagocytosis
d.)
lymphotoxin (including perforin) – kills the cell
Functions of T-Cells:
1.) Cytotoxic T-cells (Killer T-cells) release lymphotoxin (powerful poison)
2.) Helper T-cells help B-cells differentiate into antibody-secreting plasma cells by secreting
interleukin-2 & interleukin-4 (B cell differentiating factor)
3.) Suppressor T-cells suppress B-cell differentiation into plasma cells (fine tunes humoral immunity)
Types of Specific Immunity:
1.) Inherited (Inborn) Immunity – immunity is inherited
2.) Acquired Immunity – after birth – classified as:
A.)
Natural Immunity – exposure to causative agent is not deliberate
1.) Active – own immune system will respond
2.) Passive – passed from mother to fetus by placenta or milk
B.)
Artificial Immunity – exposure is deliberate
1.) Active - vaccination
2.) Passive – injection of antibodies from another individual’s immune system
Immune System Disorders:
1.) Hypersensitivity – an inappropriate or excessive response of the immune
system – 3 types:
A.)
Allergy – hypersensitivity to relatively harmless environmental antigens (or allergens)
- causes an immediate antigen-antibody rxn that will trigger the release of histamine,
kinins & other inflammatory substances
- this release causes runny nose, conjunctivitis, hives, sneezing, etc.
- some actions are delayed such as those w/ contact dermatitis from poison ivy, soaps,
cosmetics, etc.
- severe problems could lead to anaphylactic shock resulting in death if not treated
B.)
Autoimmunity – inappropriate & excessive response to self antigens
- disorders lead to autoimmune diseases – body turns on itself
- examples are:
1.) arthritis – affects joints
2.) multiple sclerosis – affects myelin of nervous system
3.) lupus – chronic inflammatory diseases that affects the joints,
blood vessels, kidneys, nervous system & skin
C.)
Isoimmunity – excessive rxn to antigens from a different indiv. of the same species
- important during pregnancy { (-) mother & (+) baby} & tissue transplants (tissue &
organ rejection)
2.) Immunodeficiency – failure of the lymphatic system mechanisms in defending against pathogens –
disruption of lymphocyte function
- chief characteristic is the dvlpt of unusual or recurring severe infections or cancer - 2 broad
categories:
A.)
Congenital Immune Deficiency – improper lymphocyte dvlpt before birth – severe
combined immune deficiency in which the stem cell dvlpt is disrupted
B.)
Acquired Immune Deficiency – dvlps after birth – could be caused by nutritional
deficiencies, immunosuppressive drugs, stress, viral infections, etc.
- Acquired Immune Deficiency Syndrome (AIDS) – caused by HIV infection of T-cells
Stress
- excessive & long-term stress can cause disease – results in:
a.) elevated adrenaline levels
c.) increased heart rate
b.) elevated Blood Pressure
d.) changed breathing patterns
Seyle’s Concept of Stress –
A. Dvlpt of the concept – noted the stress triad or stress syndrome – characteristics were:
1.) enlarged adrenals
2.) shrunken lymphatic organs
3.) bleeding gastrointestinal ulcers
B. Stress = a state of the body produced by diverse nocuous agents & manifested by a syndrome of changes
C. Stressors – anything that produces stress - varies from indiv. to indiv.
D. General Adaptation Syndrome:
- stages are:
1.) alarm rxn – consists of the stress triad, adrenocortical hypertrophy, increased
sympathetic activity & adrenal medulla secretion
2.) stage of resistance or adaptation – consists of the adrenocortex & medulla return to
normal secretion rates
3.) stage of exhaustion – occurs only w/ extremely high stress over long period of time –
results in death
E. Mechanism – stressors produce the state of stress which activates series of responses (general
adaptation syndrome)
Current Concepts of Stress
- their definition is stress is any stimulus that stimulates the hypothalamus to release corticotrophinreleasing hormone (CRH) which triggers stress response
- stress syndrome or stress response – can be:
 caused by physiological, emotional or cognitive stimuli
- indirect stimulation – through cerebral cortex or limbic system
- direct through the release of CRH which causes the
a.) release of cortisol to cause:
- increase protein catabolism
- decreased eosinophils
- hyperglycemia
- decreased immune response
b.) release of aldosterone to increase Na+ & H2O reabsorption
c.) fight-or-flight rxn
d.) increased ADH secretion
Indicators of Stress:
- increase in heart rate & force of contraction
- increase in systolic blood pressure
- sweating of hands
- dilation of pupils
- increased urinary adrenocorticoids
Stress-related Diseases & Conditions – every system responds to stress
- heart – coronary disease, hypertension, stroke
- muscles – tension headaches, backaches
- connective tissues – rheumatoid arthritis
- pulmonary – asthma
- immune system – deficiency or suppression
- gastrointestinal system – ulcers, diarrhea. Nausea
- genitourinary system – impotence, frigidity
- skin – eczema, acne
- endocrine system – diabetes mellitus, amenorrhea
- central nervous system – fatigue, overeating, depression, insomnia