powerpoint presentation - union high...

3/17/2014

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The Lymphatic System

• Lymphatic System Overview

• Lymphatic Vessels and Flow of Lymph

• Lymphoid Cells, Tissues, and Organs

(7th edition)

Overview of the Lymphatic System – Slide 2

• Major Components of the Lymphatic System (fig. 20.1)

LYMPH - an extracellular fluid (ECF) similar to plasma; ECF is found in

several places in the body: body tissues (ECF = interstitial fluid), blood

(ECF = plasma), and lymphatic vessels (ECF = lymph)

LYMPHATIC VESSELS - a network of vessels that carry lymph

throughout the body, and eventually to the venous blood system

LYMPHATIC TISSUE - protective tissue scattered throughout the body;

lymphatic tissue is a specialized connective tissue containing large

numbers of lymphocytes

LYMPHATIC ORGANS - e.g. the spleen and thymus

LYMPHOCYTES - white blood cells involved with immunity

• The Lymphatic System and Cardiovascular System are collectively called the

Circulatory System; the lymphatic system circulates lymph and the

cardiovascular system circulates blood

(7th edition)

3/17/2014

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Overview of the Lymphatic System – Slide 4

Major Functions of the Lymphatic System:

• fluid balance - excess interstitial fluid from tissue spaces (interstitial spaces) is returned to the blood by the

lymphatic capillaries; once interstitial fluid enters a lymphatic capillary it is called “lymph”

every day, about 30 liters of fluid leave your blood capillaries and enter the interstitial fluid of the body

tissues

approximately 27 of those liters are reabsorbed back into the blood capillaries

the remaining 3 liters move into the lymphatic capillaries, so that they are removed from the tissue

• distribution - of hormones, nutrients, and waste products from the site of origin to general circulation

the lymphatic system absorbs fats from the small intestines, and lymphatic vessels carry the fats to the

bloodstream

transport of lipid-soluble vitamins (A, D, E, and K) from the gastrointestinal tract to the blood

• defense - microorganisms and antigens are destroyed by WBCs

(7th edition)

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Lymphatic Vessels and Lymph Flow – SLIDE 6

• LYMPHATIC CAPILLARIES (fig. 20.1) - are found in most tissues of the body;

they differ from blood capillaries in several ways:

they originate as blind pockets; each of the lymphatic capillaries has one

closed end; extracellular fluid enters the lymphatic capillary through a

flap-like minivalve

they are larger in diameter than blood capillaries

they have thinner walls than blood capillaries

there are gaps between the endothelial cells that comprise the wall of the

lymphatic capillary making them more porous; fluids can enter the

lymphatic capillary but cannot leave

• Lymphatic vessels - resemble veins in structure; from the capillaries, lymph

moves into lymphatic vessels; they contain valves which keep the lymph

moving in one direction through these low pressure vessels

(7th edition)

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Lymphatic Vessels and Lymph Flow = Slide 7

• In general a tissue will contain many more lymphatic vessels than veins but

they will be much smaller

• Lymph moves in response to:

contraction of surrounding skeletal muscles (remember that veins return

blood to the heart using a similar mechanism); like veins, lymph vessels

have valves to keep the fluid moving in one direction

contraction of smooth muscle in wall of the lymphatic vessel

pressure changes in the thoracic cavity during respiration

• Major lymph-collecting vessels: (fig. 20.2)

THORACIC DUCT - largest lymph vessel; drains into the left subclavian

vein; drains the entire body except the upper right quarter

CYSTERNA CHYLI - expanded abdominal portion of the thoracic duct;

this is where fat-filled vessels from the digestive tract enter the lymphatic

system

RIGHT LYMPHATIC DUCT - drains lymph from the upper right quarter of

the body; drains into the right subclavian vein

(7th edition)

Drainage of different regions of the

body by lymph nodes

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Lymphoid Cells, Tissues, and Organs – Slide 9

• Types of Lymphocytes:

T CELLS (T lymphocytes) - attack foreign cells or body cells infected by viruses; T cells mature and divide

in the thymus; T cells are responsible for cell-mediated immunity (meaning that the protection is directly

from living cells)

B CELLS (B lymphocytes) - responsible for antibody-mediated immunity (=humoral immunity); a

percentage of circulating B lymphocytes mature into PLASMA CELLS; plasma cells produce and secrete

antibodies which destroy antigens

NK CELLS (natural killer cells) - attack foreign cells and cells infected with viruses and cancer cells

• LYMPHOID NODULES - lymphocytes densely packed into an area of areolar tissue

occur in the connective tissue deep to the epithelia that line the respiratory, digestive, and urinary tracts

have a central zone called a germinal center which contains dividing lymphocytes

the boundaries of the nodule are not distinct because they have no fibrous capsule surrounding them

(7th edition)

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• LYMPH NODES (fig. 20.4)

small oval lymphoid organs distributed along the lymphatic vessels; each

lymph node is covered by a capsule of dense fibrous connective tissue;

connective tissue strands call trabeculae extend inward to divide the node

into compartments

they filter the lymph, removing bacteria and antigens

lymphocytes congregate, function, and proliferate in the lymph nodes

lymph nodes are found throughout the body: superficial aggregations of lymph

nodes are found in the inguinal, axillary, and cervical regions

afferent lymphatic vessel - lymph vessel that carries lymph to the lymph

node; as lymph flows through the lymph node it is exposed to B and T cells

and macrophages; at least 99% of the pathogens in the lymph are removed

efferent lymphatic vessel - lymph vessel that carries lymph away from the

lymph node

(7th edition)

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Lymphoid Cells, Tissues, and Organs-Slide 13

SPLEEN

• located in the superior, posterior, left abdominal cavity (fig. 20.5)

• contains the largest collection of lymphoid tissue in the body

• performs the same function for blood that lymph nodes perform for lymph; the spleen filters

the blood and is involved with:

removal of abnormal blood cells and other blood components by phagocytosis

storage of iron from recycled RBCs

initiation of immune responses by B cells and T cells in response to antigens in

circulating blood

the spleen also acts as a blood reservoir

• RED PULP vs. WHITE PULP:

red pulp - area of the spleen that contains large numbers of RBCs; the structural

framework of the red pulp consists of a network of reticular fibers; it is rich in

macrophages; red pulp is mainly concerned with disposing of worn-out red blood cells

and bloodborne pathogens

white pulp - area of the spleen that resembles lymphoid nodules; it is composed

mostly of lymphocytes suspended on reticular fibers, and is involved with the immune

functions of the spleen

(7th edition)

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• TONSILS

Large lymphoid nodules in the walls of the pharynx and oral cavity (fig. 20.5)

pharyngeal tonsil - also called the “adenoids” is located in the posterior superior wall

of the nasopharynx

palatine tonsils - a pair of tonsils located at the posterior margin of the oral cavity

along the border along its boundary with the oropharynx

lingual tonsil - located under the attached base of the tongue

• PEYER’S PATCHES

Peyer's patches are clusters of lymphoid nodules deep to the epithelial lining of the

small intestine (fig. 20.5)

contain lymphocytes and macrophages which remove microorganisms, debris, and

antigens from the digestive tract

• APPENDIX - large concentrations of lymphoid tissue are located in the wall of the appendix;

thus, the appendix has some lymphatic function (fig. 20.5)

(7th edition)

Innate Host Defenses; innate defenses are present at birth and are

genetically determined = Slide 16

• Innate External Defense System - first line of defense

surface barriers include the skin and mucous membranes of the respiratory, digestive, urinary, and

reproductive tracts

characteristics of skin that help it to resist invasion:

water-resistant and tough keratin outer layer

intercellular junctions hold skin cells tightly together

skin secrections are acidic and have chemicals that make the skin inhospitable to pathogens; e.g.

lysozyme destroys cell walls of certain bacteria

mucous membranes not only provide a barrier, but also produce a variety of protective chemicals (e.g.

lysozyme) and acidic secretions

the stomach secretes digestive enzymes and has a very low pH

the digestive and respiratory pathways are lined with sticky mucous that traps pathogens

(7th edition)

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Innate Host Defenses = Slide 17

• Innate Internal Defense System - second line of defense; attempts to limit the spread of pathogens; this system

is fast-acting and nonspecific

the internal defense system has 5 components:

phagocytic cells (e.g. neutrophils and monocytes/macrophages)

NK cells (natural killer cells)

antimicrobial proteins (complement and interferon)

inflammation

fever

(7th edition)


• Innate Internal Defense System - second line of defense; attempts to limit the

spread of pathogens; this system is fast-acting and nonspecific

phagocytes (fig. 21.2)

neutrophils are the first cells to leave the blood and enter tissues at

the sites of infection or trauma; these cells are short-lived

monocytes follow the influx of neutrophils into the affected tissue;

once in the tissue, they transform into macrophages; they

phagocytize many more pathogens than neutrophils

phagocytes use special membrane receptors to recognize and bind

molecules that are found on pathogens, but not on normal body cells

when a phagocyte recognizes a pathogen it:

- ingests the pathogen

- releases chemical alarm signals that mobilize other cells of

innate and adaptive immunity

OPSONIZATION - some bacteria have capsules that make it difficult

for phagocytes to grab them; the immune system makes molecules

that “coat” the bacteria and enhance phagocytosis; this is called

opsonization; both complement and antibodies can act as

opsonins

(7th edition)

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Innate Host Defenses – Slide = 19

• Innate Internal Defense System - second line of defense; attempts to limit the

spread of pathogens; this system is fast-acting and nonspecific

NK cells (natural killer cells)

type of lymphocyte involved in innate immunity

attack body cells that have been invaded by pathogens (e.g. viruses)

or cancer; they will also attack the cells of transplanted tissues

NK cells are larger than B and T cells, and unlike B and T cells, do

not have antigen receptors

both NK cells and T cells are involved in IMMUNE SURVEILLANCE

(they continually scan our cells for abnormalities)

(7th edition)


• Innate Internal Defense System - second line of defense; attempts to limit

the spread of pathogens; this system is fast-acting and nonspecific

antimicrobial proteins

interferons (fig. 21.5)- interfere with viral replication and activate

immune cells; cells that have been attacked by a virus release

interferon to help protect neighboring cells that have not yet been

affected

complement (complement system) (fig. 21.6) - it

“complements” or enhances other components of both innate

and adaptive defenses; it can mark cells for phagocytosis,

promote inflammation, and kill some bacteria

(7th edition)

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inflammation

when the body is injured (e.g. a cut, abrasion, or bruise) a sequence of events called inflammation is

initiated

tonsillitis, tendonitis, and laryngitis are examples of short-lived, or acute, inflammation; arthritis is an

example of long-term, or chronic, inflammation

there are 4 cardinal signs of inflammation: pain, swelling, redness, and heat

the purpose of inflammation is to bring white blood cells and plasma proteins into an injured area;

inflammatory mediators (e.g. histamine from basophils and mast cells) cause vasodilation

(increasing blood flow to the area) and an increase in vascular permeability (allowing phagocytes

and plasma proteins to enter the tissue)

plasma proteins and more fluid than usual leak into the injured area causing EDEMA (increased

interstitial fluid); edema causes swelling, which can contribute to the sensation of pain

(7th edition)




fever

generalized increase in body temperature

PYROGENS - chemicals secreted by leukocytes and macrophages that have been exposed to foreign

substances in the body; they cause the body’s thermostat (located in the hypothalamus) to set its

temperature higher

higher body temperatures enhance phagocytosis and cause the liver and spleen to sequester iron and

zinc (making these essential elements less available to bacteria); pathogens also do not grow very

well at higher temperatures

(7th edition)

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Adaptive Defenses - the body’s third line of defense = Slide 23

• Adaptive Defenses are Specific, Systemic, and have Memory; they include

Humoral Immunity (antibody-mediated) and Cellular Immunity (cell-meditated)

• B and T Lymphocytes are key players in adaptive immunity

• Antigens (fig. 21.7)

have multiple antigenic determinants (based on shapes)

self-antigens are the shapes that lymphocytes expect to find in the body

(thus lymphocytes do not normally attack them)

antigen receptors are specific and diverse

(7th edition)

Adaptive Defenses = Slide 24

• “Education” of Lymphocytes

immunocompetence - the lymphocyte is able to recognize its one specific

antigen by binding to it

self-tolerance - the lymphocyte is unresponsive to self-antigens, so that it

does not attack the body’s own cells

T cells become immunocompetent and self-tolerant in the thymus, whereas

for B cells this occurs in the bone marrow

• Autoimmune Diseases - lymphocytes attack the body’s own cells; e.g. Type 1

Diabetes mellitus, Grave’s disease, and Multiple sclerosis

• Memory Cells - are created in large numbers during a primary immune response

(exposed to antigen for first time); memory cells create a larger number of

effector cells during a secondary immune response (exposed to antigen again);

thus, the response to the second attack will be much greater

(7th edition)

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