Chap 22: Lymphoid System and Immunity

What is the lymphoid system?

a network of tissues, organs, and vessels that help to maintain the body’s fluid balance, cleanse the body of foreign matter, and provide immune cells for defense

What are lymphoid system components?

lymph, lymphatic vessels, lymphoid tissue, and lymphoid organs

What is lymph?

fluid from interstitial fluid spaces

What reabsorbs lymph?

Capillaries reabsorb 85% of it, lymph system reabsorbs the 15%

What happens if the lymphatic system has an issue with drainage?

If the lymphatic system has an issue with its drainage this can cause the tissue to swell

Tissue swelling as a result of failure to drain is called?

lymphedema

What do lymphatic vessels do?

transport the lymph

What do lymphoid tissue and lymphoid organs have?

lymphocytes and other cells are concentrated

What are functions of the lymphoid system?

fluid recovery, immune surveillance, lipid absorption

What is fluid recovery?

reabsorb 15% of fluid filtered (H2O & protein) at capillary beds into interstitial spaces. 85% of fluid is absorbed by the capillaries.

What happens if the 15% is not returned to the blood?

One can die of circulatory failure within hrs

What are pathogens?

microorganisms with the potential to cause disease

What is immune surveillance?

immune cells monitor lymph for foreign agents and pathogens (microorganisms with the potential to cause disease). On the way back to the blood, the fluid passes through lymph nodes, which act as filters where immune cells guard against pathogens & activate immune responses.

What are lacteals?

special lymphatic vessels

What is lipid absorption?

lacteals (special lymphatic vessels) in small intestine absorb dietary lipids that cannot be absorbed by the intestinal blood capillaries.

What is lymphedema?

excess fluid accumulation due to interference of lymphatic drainage.

What is edema?

accumulation of excess fluid in loose connective tissue.

What are larger lymphatic similar too in structure?

veins

Describe larger lymphatics

Larger lymphatics similar to veins in their structure, though their walls are thinner and valves are closer together

What do larger lymphatic have specifically?

a tunica interna with an endothelium and valves. a tunica media with elastic fibers and smooth muscle, and a thing outer tunica externa. Their walls are thinner and their valves are closer together than those of veins.

Although larger lymphatics are similar to veins in structure, what do they have that veins do not?

valves that are closer together

What is the flow of lymph?

Lymphatic capillaries → collecting vessels → lymphatic trunks → collecting ducts (largest lymphatic vessels) → subclavian veins (blood)

What are lymphatic trunks named by?

location

Provide examples of lymphatic trunks

jugular, subclavian, bronchomediastinal, intercostal, intestinal, and lumbar

What do lymphatic trunks converge to form?

collecting ducts

What are the two collecting ducts of the lymphatic trunk

right lymphatic duct and thoracic duct

What is the right lymphatic duct?

convergence of trunks in right thoracic cavity; drains right upper limb, right side of head, right side of thorax.

where does the right lymphatic duct drain

Drains into the right subclavian vein.

What is the thoracic duct?

(collects the fatty lymph from the small intestine called chyle) of abdomen. Drains all of the body below the diaphragm, and the left upper limb and left side of the head, neck and thorax.

Where does the throacic duct drain?

Drains into the left subclavian vein.

Collecting vessels converge to form what?

larger lymphatic trunks

Lymphatic trunks drain ?

major potions of the body

How many lymphatic trunks are there

11, whose names indicate their locations and parts of the body they drain

What does the lumbar trunk drain?

not only the lumbar region, but also the lower limbs

What are the lymphoid cells

T lymphocytes, B lymphocytes, Natural killer cells, dendritic cells

What are t lymphocytes ( t cells )

mature in thymus; have many subtypes with different functions

What are two exmaples of t lymphocytes

helper T cells and cytotoxic T cells

What do helper T cells do

activate other immune cells (signal B cells to transform into plasma cells that produce antibodies)

what do cytotoxic T cells do

destroy infected and abnormal cells (cancer cells)

What are B lymphocytes ( b cells )

mature in bone marrow; after activation they differentiate into plasma cells that secrete antibodies (defensive proteins)

What are natural killer cells ( NK )

destroy infected and abnormal (malignancy) cells

What two cells are involved in defense against cancer

cytotoxic T cells and NK cells

What cells are natural killer cells similar too?

cytotoxic cells, but broder, more generalized defense

What are dendritic cells ( DCs )

phagocytic cells. 10 role is to activate T cells and controlling responses of other cells

Where are dendritic cells found?

Found in lymphoid organs, mucous membranes & skin.

Provide the circulating lymphocyte percentage

80% T cells, 15% B cells and 5% NK & stem cells.

What are macrophages ( big eaters )

widespread phagocytes that develop from monocytes

Where do macrophages develop from?

monocytes

What is the function of macrophages

Engulf and break down debris, dead cells, microbes, and foreign matter; secrete growth factors & other signaling molecules to stimulate wound healing and tissue regeneration

What do macrophages serve as?

antigen-presenting cells (APCs) to alert the immune system to invaders & activate immune responses

What is the macrophage system?

all the body’s phagocytic cells (except leukocytes)

Describe the body’s phagocytic cells

Some are wandering cells, Others are fixed in place like lymph nodes, blood sinusoids of liver & spleen

Give examples of cells of macrophages

microglia (brain), alveolar macrophages (lungs), stellate macrophages (liver), interstitial macrophages (intestinal mucosa)...

Describe the flow of afferent and effernt lymphatic vessels

Several afferent lymphatic vessels lead to node, but few efferent lymphatic vessels leave its hilum

What is the lymph node?

a bottleneck that slows down lymph flow an allows time for cleansing it of foreign matter

What do macrophages and reticular cells of the sinuses do before the lymph leaves the node?

removes about 99% of the impurities before the lymph leaves the node

On the way to the bloodstream, where does the lymph go?

lymph flows through one lymph node after another and thus becomes quite thoroughly cleansed

Why are the axillary lymph nodes often biopsied in cases of suspected breast cancer

cancer cells breaking free of a breast tumor enter the lymphatic and often lodge and seed the growth of secondary tumors in these nearby lymph nodes

What are the largest and most infected tonsils

the palatine tonsils

What is tonsillitis?

acute inflammation of the palatie tonsils, usually caused by a viral or bacterial infection

What is tosillectomy?

surgical removal of palatine tonsils

Tonsillectomy used to be ?

the most common surigical procedure performed on children, however, it is less often done today due to tonsillities being treated w/ antibiotics

Which tonsils are most likely to be affected by an inhaled pathogen

pharyngeal tonsil is th emost vulnerable to inhaled pathogens

What is the spleen

argest lymphoid organ measuring up to 12 cm long; has two types of tissue, red pulp and white pulp

Where is the spleen located?

Located in LUQ, specifically left hypochondriac region.

What are the two types of tissue in the spleen?

red pulp and white pulp

What is red pulp?

sinusoids full of concentrated erythrocytes

What happens to old, fragile RBCs

Old, fragile RBCs recognized and phagocytized by macrophages, removing them from bloodstream (erythrocyte graveyard)

What is white pulp?

lymphocytes and macrophages aggregated along branches of the splenic artery

What do cells of the white pulp do?

monitor the blood for foreign agents and

what is the function of white pulp

Reservoir for monocytes to be released when needed

What is the spleen called

“erythrocyte graveyard”

Why is the spleen called the erythrocyte graveyard

old, fragile RBCs exhibit oxidative stress to their plasma membrane, enabling macrophages to recongize and phagocytize them, removing them from circulation just as they dispose of blood-borne bacteria and other cellular deris.

What does the spleen produce

erythrocytes in the fetus and may rsume this role in adults w/ extreme anemia

What is the spleen a reservoir for

large “standing army” of monocytes, waiting in emergency preparedness.

when monocytes disperse and colonie organs, what happens after?

monocytes become macrophages and help to combat pathogens and repair damageed tissues

What does the spleen stabilize

blood volume by transferring excess plasma from the bloodstream into the lymphoid system

review an overwie of the immune system

Describe the first step of Lymphocyte Activation

B cells bind and engulf antigens, and present fragments to helper T cells

Describe the second step of Lymphocyte Activation

Helper T cells may activate the B cell

Describe the third step of Lymphocyte Activation

Activated B cells multiply and transform into plasma cells that produce antibodies

Describe the fourth step of Lymphocyte Activation

Some activated B cells become memory B cells to resist future encounters. Provide lasting protection.

What are the three categories immune disorders are classified into?

autoimune diseases, hypersensitivity, immunodeficiency diseases

What are autoimmune diseases

immune attack of own tissues

What is an example of an autoimmune disease

insulin-dependent diabetes, rheumatoid arthritis

where are autoimmune diseases more common

in women than men

What is hypersensitivity

exaggerated immune responses to antigen

what does hypersensitivity include?

Includes allergies: excessive reactions to environmental antigens (allergens) such as insect venoms, plant products (poison oak, poison ivy), dust, pollen, nuts, milk, eggs, and others

In many cases, what does an allergen stimulate and what does it cause?

An allergen stimulates basophils and mast cells to release histamine and other chemicals that cause a broad range of symptoms, edema, congestion, watery eyes, runny nose, hives, cramps, diarrhea, vomitting, and sometimes catastrophic circulatory failure (anaphylactic shock)

What is Immunodeficiency diseases

failure of immune responses

What is a congenital example of an Immunodeficiency diseases

Congenital example: severe combined immunodeficiency disease (SCID)-

born without a functional immune system

What is a acquired example of an Immunodeficiency diseases

acquired immunodeficiency syndrome (AIDS), caused by HIV virus infection. Targets helper T cells (CD4)

Provide the lymphatic trunks

paired jugular, subclavian, bronchomediastinal, inercostal, and lumbar trunks