1

Lymphatic SystemLymphatic System LL

YY

MM

PP

HH

AA

TT

II

CC

CC

OO

MM

PP

OO

NN

EE

NN

TT

SS

What is a Lymphatic System?What is a Lymphatic System?The lymphatic system is a

complex system of fluid drainage

and transport, immune response,

and disease resistance.

Fluid that is forced out of the

bloodstream during normal

circulation is filtered through

lymph nodes to remove bacteria,

abnormal cells and other matter. This fluid is then

transported back into the bloodstream via the lymph vessels.

Lymph only moves in one direction, toward the heart.

• Return tissue fluid

to the bloodstream

(fluid balance)

• Immunity

• Transport fats from

the digestive tract to

the bloodstream

FunctionsFunctions

2

Lymphatic VesselsLymphatic Vessels– Resemble veins in structure

– Connect to lymph nodes at various intervals, but begin

blindly in the intercellular spaces of the soft tissues.

They do NOT form a closed circuit.

– Ultimately deliver lymph into 2 main channels …

� Right lymphatic duct

– Drains right side of head & neck,

right arm, right thorax

� Thoracic duct

– Drains the rest of the body

– Biggest lymphatic vessel!

Lymphatic VesselsLymphatic Vessels

Lymph: Clear, watery-appearing fluid which resembles blood plasma but

has a lower % of protein. It is found in the lymphatic vessels.

Interstitial Fluid: Complex fluid which fills the spaces between cells.

Lymph TissueLymph Tissue1. Diffuse lymphatic tissue

– No capsule present

– Found in connective tissue of almost all organs

2. Lymphatic nodules– No capsule present

– Oval-shaped masses

– Found singly or in clusters

3. Lymphatic organs– Capsule present

– Lymph nodes, spleen, thymus gland

There are lymph nodes

you can feel in your

armpits, in your groin

at the top of your legs,

and in your neck.

There are lymph nodes

you cannot feel in your

abdomen, pelvis, and

chest.

Lymph Nodes

3

Swollen lymph nodes, sore throat, fatigue and headache are

some of the symptoms of mononucleosis which is caused by

the Epstein-Barr virus. Most patients recover in 4 - 6 weeks

without medication.

TonsilsTonsilsMultiple groups of large lymphatic nodules located on

the mucous membrane of the oral and pharyngeal

cavities.

� Palatine

• Posterior-lateral walls of oropharynx

� Pharyngeal (Adenoids)

• Posterior wall of nasopharynx

� Lingual

• Base of tongue

4

(Palatine)

The palatine

tonsils are

the ones we

see at the

back of the

throat.

SpleenSpleen– Largest lymphatic organ!

– Located below the diaphragm,

behind the stomach, and above

the left kidney

– Functions:

� Filters blood – macrophages remove microorganisms

� Hematopoiesis – monocytes & lymphocytes finish

their development here

� Red blood cell & platelet destruction

� Stores blood

Thymus GlandThymus Gland

– Located behind the sternum

– Functions in differentiation and maturation of T cells

5

Immune SystemImmune System– Defends against

harmful organisms,

chemicals, and

tumors.

– 2 types of defense

� Nonspecific

� Specific

Nonspecific Defense Mechanisms

Interferon: protein made by certain cells and released into circulation if invaded by viruses.

Inflammation is a non-specific defense mechanism.

Phagocytosisis a non-specific

defense mechanism too!

� Antibody-mediated Immunity (Humoral)B cells become plasma cells which produce antibodies

that bind with specific antigens.

� Cell-mediated ImmunityT cells directly destroy foreign cells.

Specific Defense MechanismsAntigen specificity; self/non-self recognition; immunological memory

6

Sensitized B-cell

Plasma cells

Antibodies

secrete

Memory B-cellsSubsequent antigen meetings

Secondary

response

Antibody-mediated Immunity (Humoral)

Primary

response

5 Classes of Antibodies5 Classes of AntibodiesIgM – produced for initial contact with antigen; first

secreted during primary response

IgG – major antibody of the secondary response;

found in plasma

IgA – predominant antibody in mucous membranes,

tears, saliva, and mother’s milk

IgE – small amount; involved in allergies: promotes

the release of histamine by mast cells

IgD – small amount; exact function is unknown

Sensitized T-cell

Helper

T-cells

Killer

T-cells

Suppressor

T-cells

Memory

T-cells

Activate

B-cells

Directly contact

and kill target

Persist to provide for

secondary responses;

Circulate in blood & lymph

Slow or stop the

activity of B and T cells

Cell-mediated Immunity

7

HIVHuman immunodeficiency virus is a retrovirus that

primarily infects the human immune system, specifically

CD4+ T cells (Helper T-cells) � AIDS!

The HIV infection cycle: The cycle begins and ends

with free HIV particles present in the bloodstream of its

human host. These free viruses infect white blood cells

that have CD4 receptors (CD4+ cells).

� Attachment

� Entry into macrophages

� Replication

� Entry into T cells

The Future of HIV Treatment

1. Combination Therapy – Use of 2 drugs … AZT

which blocks replication of the virus and protease

inhibitors to block the production of vital proteins.

2. Vaccine - using defective viral gene nef

Drug Therapy – to inhibit nef’s protein product

3. Blocking receptors

4. Disabling receptors

5. Blocking replication with CAF (an antiviral factor)