a&p 2: lymphatic and immune system

The body harbors at least __ times as many bacterial cells as human cells

10

bacterial cells can be beneficial as well as potentially ________________

disease-causing

Immune system

not an organ system, but a cell population that inhabits all organs and defends the body from agents of disease

the immune system is especially concentrated in this true organ system

lymphatic system

Lymphatic system

A network of organs and vein-like vessels that recover fluid

inspects it for disease

activate immune responses

return fluid to the blood stream

What is one function of the immune system?

Inspect it for disease agents.

What does the immune system activate?

Immune responses.

What does the immune system return to the bloodstream?

Fluid.

Fluid recovery

Fluid continually filters from the blood capillaries into the tissue spaces

blood capillaries reabsorb __%

85

15% (2 to 4 L/day) of the water and about half of the plasma proteins enter the ____________ system and then are returned to the ________.

lymphatic; blood

What picks up foreign cells and chemicals from the tissues in the lymphatic system?

Excess filtered fluid

What do lymph nodes do in the lymphatic system?

Immune cells stand guard against foreign matter

What is activated when foreign matter is detected in the lymphatic system?

A protective immune response

lipid absorption

lacteals, in small intestine absorb dietary lipids that are not absorbed by the blood capillaries

lymph

recovery fluid

lymphatic vessels

transport the lymph

lymphatic tissues

Composed of aggregates ( group) of lymphocytes and macrophages that populate many organs in the body

lymphatic organs

Defense cells are especially concentrated in these organs

Separated from surrounding organs by connective tissue capsules

lymph

Clear, colorless fluid, similar to plasma, but much less protein.

Where does lymph originate?

It originates as extracellular fluid drawn into lymphatic capillaries.

How does the chemical composition of lymph vary?

The chemical composition varies in different places, such as in the intestines and after lymph nodes.

Lymphatic Capillaries

Penetrate nearly every tissue of the body absent from cartilage, cornea, bone, and bone marrow

What type of cells make up the wall of lymphatic capillaries?

Endothelial cells overlapping each other like roof shingles

How are lymphatic capillaries closed?

Closed at one end

What tethers lymphatic capillaries to surrounding tissue?

Protein filaments

What is the size of the gaps between endothelial cells in lymphatic capillaries?

Large enough to allow bacteria and cells to enter

What do the valve-like flaps in lymphatic capillaries respond to?

Interstitial fluid pressure

When do the valve-like flaps in lymphatic capillaries open?

When interstitial fluid pressure is high

When do the valve-like flaps in lymphatic capillaries close?

When interstitial fluid pressure is low

What are the three layers of larger lymphatic vessels?

Tunica interna, tunica media, tunica externa

What is found in the tunica interna of lymphatic vessels?

Endothelium and valves

What components are present in the tunica media of lymphatic vessels?

Elastic fibers and smooth muscle

What is the characteristic of the tunica externa in lymphatic vessels?

It is a thin outer layer

How do lymphatic vessels change as they converge?

They converge into larger and larger vessels

What do collecting lymphatic vessels course through?

Many lymph nodes

Two collecting ducts

right lymphatic duct & thoracic duct

Right lymphatic duct

receives lymph from right arm, right side of head and thorax; empties into right subclavian vein.

Thoracic Duct

larger and longer, begins as a prominent sac in abdomen called the cisterna chyli; receives lymph from below diaphragm, left arm, left side of head, neck, and thorax; empties into left subclavian vein.

Subclavian veins

collect from thoracic duct and right lymphatic duct

How does lymph flow compared to venous blood?

Lymph flows at low pressure and slower speed than venous blood.

What governs the flow of lymph?

Lymph flows under forces similar to those that govern venous return, except no pump (heart).

What helps move lymph along lymphatic vessels?

Rhythmic contractions of lymphatic vessels.

What stimulates the contraction of lymphatic vessels?

Stretching of vessels stimulates contraction.

What aids the flow of lymph?

Skeletal muscle pump

What rhythmically squeezes lymphatic vessels?

Arterial pulsation

What aids the flow of lymph from the abdominal to thoracic cavity?

Thoracic pump

What prevents backward flow in lymphatic vessels?

Valves

What draws lymph into subclavian veins?

Rapidly flowing blood

What significantly increases lymphatic return?

Exercise

Natural killer (NK) cells

Large lymphocytes that attack and destroy bacteria, transplanted tissue, host cells infected with viruses or that have turned cancerous

T lymphocytes (T cells)

Mature in thymus

B lymphocytes (B cells)

Activation causes proliferate (multiply) and differentiate into plasma cells that produce antibodies.

• Some activated B cells also become memory B cells.

macrophages

Large, avidly phagocytic cells of connective tissue.

What do macrophages develop from?

Monocytes.

What do macrophages phagocytize?

Tissue debris, dead neutrophils, bacteria, and other foreign matter.

What is the role of macrophages in the immune system?

They process foreign matter and display antigenic fragments to certain T cells.

antigen-presenting cells (APCs)

Cells that present antigenic fragments to T cells, including macrophages.

dendritic cells

Branched, mobile antigen-presenting cells (APCs)

Found in epidermis, mucous membranes, and lymphatic organs.

What is the function of dendritic cells?

They alert the immune system to pathogens that have breached the body surface.

Reticular cells

Branched stationary cells that contribute to the stroma( supporting framwork) of a lymphatic organ

Lymphatic (lymphoid) tissue

aggregations of lymphocytes in the connective tissues of mucous membranes and various organs

What is the simplest form of lymphatic tissue?

Diffuse lymphatic tissue

How are lymphocytes arranged in diffuse lymphatic tissue?

Scattered (not clustered)

Where is diffuse lymphatic tissue prevalent (found in) ?

In body passages open to the exterior

Which tracts contain diffuse lymphatic tissue?

Respiratory, digestive, urinary, and reproductive tracts

What does MALT stand for?

Mucosa-associated lymphatic tissue

What are lymphatic nodules (follicles)?

Dense masses of lymphocytes and macrophages that congregate ( form group) in response to pathogens.

Where are lymphatic nodules a constant feature?

In the lymph nodes, tonsils, and appendix.

What are aggregated lymphoid nodules?

Dense clusters of lymphatic nodules found in the ileum, the distal portion of the small intestine.

are lymphatic organs anatomically well-defined?

Yes, they have connective tissue capsule that separates lymphatic tissue from neighboring tissues

primary lymphatic organs

Red bone marrow and thymus,

• where we make lymphocytes

site where T and B cells become immunocompetent -- able to recognize and respond to antigens

Secondary lymphatic organs

Lymph nodes, tonsils, and spleen, immunocompetent cells populate these tissues

What two processes is red bone marrow involved in?

hematopoiesis (blood formation) and immunity

What type of tissue is red bone marrow?

Soft, loosely organized, highly vascular material

What separates red bone marrow from osseous tissue?

Endosteum of bone

How do blood cells mature in red bone marrow?

They push their way through the reticular and endothelial cells to enter the sinus and flow away in the bloodstream.

What systems is the thymus a member of?

Endocrine, lymphatic, and immune systems

What does the thymus house?

Developing lymphocytes

What does the thymus secrete?

Hormones regulating lymphocyte activity

Where is the thymus located?

In the superior mediastinum between the sternum and aortic arch

What happens to the thymus with age?

It undergoes degeneration (involution)

What structure gives off trabeculae that divide the thymus gland into several lobes?

Fibrous capsule

What are the two main regions of the thymus lobes?

Cortex and medulla

What type of cells populate the cortex and medulla of the thymus?

T lymphocytes

What do epithelial cells in the thymus form between the cortex and medulla?

Blood-thymus barrier

Name the signaling molecules produced by the thymus.

thymosin, thymopoietin, thymulin, interleukins, and interferon

What are lymph nodes?

Most numerous lymphatic organs.

How many lymph nodes are typically found in a young adult?

About 450.

What are the two main functions of lymph nodes?

Cleanse the lymph and act as a site of T and B cell activation.

What is the shape of lymph nodes?

Elongated, bean-shaped structure.

What is the hilum in relation to lymph nodes?

It is a part of the lymph node structure that lets it have an opening indent

What encloses lymph nodes?

A fibrous capsule.

What divides the interior of lymph nodes into compartments?

Trabeculae.

What is the stroma of lymph nodes made of?

Reticular fibers and reticular cells.

What are the two main regions of a lymph node?

Cortex and medulla

What are germinal centers in lymph nodes responsible for?

Where B cells multiply and differentiate into plasma cells

How many afferent ( arrives) lymphatic vessels typically lead into a lymph node?

Several

Through how many efferent lymphatic vessels does lymph leave a lymph node?

One to three

Where do efferent lymphatic vessels exit a lymph node?

The hilum