Chapter 12 -The Lymphatic and Immune System Flashcards Preview

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Functions of the immune system

Responsible for protecting humans against bacteria, viruses, fungi, toxins, parasites, and cancer

Works with the organs of the lymphatic system to clear the body of these disease-causing agents
Thymus, spleen, lymphatic vessels, lymph nodes, and lymphoid tissue


Lymphatic System Components and Functions

Network of connecting vessels that collects the interstitial (or tissue) fluid found between cells

Lymphatic vessels then return this fluid, now called lymph, to the bloodstream

Also picks up lipids and fat-soluble vitamins from the digestive tract and transports them to the bloodstream

Protects the body against disease-causing agents


Interstitial Fluid and Lymph Fluid

Fluid constantly leaks out of blood capillaries into the spaces between cells
Increased tissue hydrostatic pressure moves interstitial fluid into the lymphatic vessels
Fluid is destined to become lymph


Lymphatic Capillaries

Similar in structure to blood capillaries
Larger in diameter

Thin, very permeable walls
Lined by a single layer of squamous epithelial cells called endothelium

Epithelial cells overlap
Create flaplike valves that allow fluid to enter the capillary, but do not allow fluid to exit under normal conditions

Lymph can leak out of the vessels, causing edema or fluid buildup in the interstitial spaces


Lymphatic Trunks

Named after the region in which they are found
Jugular trunks - Head and neck region
Lumbar trunk - Lower extremities
Subclavian trunk - Upper limbs
Bronchomediastinal trunk - Thorax


Right lymphatic duct

Receives lymph from the upper right side of the body
Empties its contents into the right internal jugular and right subclavian veins
Return the lymph to the right atrium by way of the superior vena cava


Thoracic duct

Drains lymph from all parts of the body that are not drained by the right lymphatic duct
Begins at the level of the second lumbar vertebra and has a dilated sac or channel called the cisterna chyli
Empties into the junction of the left internal jugular and left subclavian veins


Lymphatic Movement

Lymph is moved along towards the heart


Skeletal muscle pump

Utilizes skeletal muscle contractions to move the lymph


Respiratory pump

Utilizes pressure changes in the thorax to assist circulation


Lymphatic Pathway

Lymphatic Capillary >Afferent Lymphatic vessel> lymph node> Efferent Lymphatic vessel >Lymphatic trunk>collecting duct >Subclavian trunk



Blockage of lymphatic vessels

Caused by genetics, parasitic infections, trauma to the vessels, tumors, radiation therapy, cellulitis, and surgeries (mastectomies and biopsies).
Tissue swelling that lasts longer than a few days or increases over time
compression stockings . maintain good nutrition . keep skin clean


Lymph Nodes

Very small, glandular structures
Located along the paths of larger lymphatic vessels
Spread throughout the body

Indented side is called the hilum- Nerves and blood vessels enter
Afferent lymphatic vessels -Carry lymph to the node
Efferent lymphatic vessels - Carry lymph out of a node are called efferent vessels
Lymph tends to concentrate in the node.- Pressure builds up that assists in filtration
Surrounded by a fibrous capsule of connective tissue
Medulla- Inner portion
Cortex- Outer portion


Macrophages and lymphocytes

Together these form the lymph nodules
Lymph nodules are found in the cortex.
Macrophages digest unwanted pathogens in the lymph.
Lymphocytes are part of the immune response against the pathogen.


Viral or bacterial infection, causes lymphadenitis

Inflammation of the lymph nodes
Any disease of the lymph nodes is called lymphadenopathy
Terms lymphadenitis and lymphadenopathy are often used interchangeably



Soft, bilobed organ
Located behind the sternum, just below the thyroid gland and above the heart
Large in the infant
Maximum size, 1 to 2 ounces, when the child is about two years of age
After adolescence, atrophies or involutes
In older adults, tiny or almost nonexistent

Produces the hormone thymosin
Stimulates the production of mature lymphocytes


Cortex of thymus

Outer portion
Where T lymphocytes (T cells) that have been produced in the bone marrow proliferate


Medulla of thymus

Inner portion
T cells move to and mature



Located in the upper-left quadrant of the abdominal cavity
Below the diaphragm and behind the stomach
Protected by the rib cage
Divided into lobules with two types of tissues
White pulp is concentrated with lymphocytes.
Red pulp has an abundance of red blood cells, lymphocytes, and macrophages.

Filters blood and removes worn-out red blood cells from the bloodstream
Splenomegaly- Injured or becomes enlarged due to disease
Splenectomy- Removed to prevent rupture


Lymphatic Nodules

Masses of lymphatic tissue not surrounded by a capsule
Often referred to as mucosa-associated lymphoid tissue (MALT)



Lymphatic Nodules
Tonsils are three sets of lymphoid tissue
Form a ring known as the Ring of Waldeyer
Pharyngeal tonsils or adenoids
Junction of the mouth and oropharynx
Palatine tonsils
Junction of the nasal cavity and nasopharynx
Lingual tonsils
Located at the base of the tongue


Appendix, or vermiform appendix

Lymphatic Nodules
Located in the lower-right quadrant at the junction of the large and small intestines
Once thought to have no function
Part of the immune system

Peyer’s patches
Located in the small intestine


Disease Defenses

Immunity, also known as resistance
Divided into innate and acquired immunity
We are born with innate or nonspecific immunity.
Acquired or specific immunity takes place over a period of time after exposure to an antigen.
Disease may take the form of injury, infection, or malignancy.
Infection is the presence of a pathogen in or on the body.
Pathogen is a disease-causing agent such as a bacterium, virus, toxin, fungus, or protozoan.


Zoonotic disease

Disease that is transmissible from an animal to humans



Innate (Nonspecific) Defenses
Neutrophils and monocytes have phagocytic characteristics
Monocytes are transformed into macrophages.
Very large and active phagocytes capable of ingesting very large particles
Neutrophils, monocytes, and macrophages make up what is called the mononuclear phagocytic system or the reticuloendothelial system


Physical barriers

Skin and the mucosa that line the digestive tract, oral cavity, and other areas
First line of defens


Chemical barriers

Chemicals and enzymes in body fluids provide barriers that destroy pathogens
Along with the remaining nonspecific mechanisms, form the second line of defense


Natural killer (NK) cells

Innate (Nonspecific) Defenses
Natural killer (NK) cells
Type of lymphocyte which primarily targets cancer cells
Like cytotoxic T cells, NK cells kill harmful cells on contact
Secrete chemicals called perforins that punch holes in the membranes of harmful cells
Unlike B and T cells, NK cells do not have to rely on memory to recognize a specific antigen to start destroying pathogens



Innate (Nonspecific) Defenses
Injury or infection cause this vascular response
Cardinal signs
Heat, swelling, erythema, pain, and loss of function
Blood vessels in the injured area first constrict then dilate
Also become more permeable or “leaky”

Neutrophils and monocytes
Leave the blood vessels to fight the infection
Clean up the area


Acquired (Specific) Defenses

Another name for immunity, the third line of defense
Classified as cellular or humoral immunity