Chapter 20 The Lymphatic System and Lymphoid Organs and Tissues

lymph flow

-From lymphatic capillaries to larger lymphatic vessels containing one-way valves (lymphatic capillaries> collecting lymphatic vessels> lymphatic trunks> lymphatic ducts)

lymphatic system consists of three parts :

1) A network of lymphatic vessels 2) Lymph, the fluid contained in those vessels 3) Lymph nodes, cleanse the lymph as it passes through them

Activated _________ cells protect the body by producing plasma cells, daughter cells that secrete antibodies into the blood (or other body fluids)

B

oversee humoral immunity; their descendants differentiate into anti-body producing plasma cells

B cells (B lymphocytes)

thymic lobule

Contains a dense outer cortex and a pale central medulla -Lymphocytes divide in the cortex -T cells migrate into medulla -Mature T cells leave thymus by medullary blood vessels

T/F: Proteins in the interstitial space are unable to enter lymphatic capillaries, but they enter blood capillaries easily.

FALSE: Proteins in the interstitial space are unable to enter blood capillaries, but they enter lymphatic capillaries easily.

T/F: The lymphatic vessels form a two-way system in which lymph flows toward the heart and connective tissue

FALSE: The lymphatic vessels form a one-way system in which lymph flows only toward the heart.

What is the benefit of having fewer efferent than afferent lymphatics in lymph nodes?

Having fewer efferents causes lymph to accumulate in lymph nodes, allowing more time for its cleansing.

process to know:

Lymph enters the convex side of a lymph node through a number of afferent lymphatic vessels.It then moves through a large, baglike sinus, the subcapsular sinus, into a number of smaller sinuses that cut through the cortex and enter the medulla. The lymph meanders through these medullary sinuses and finally exits the node at its hilum (hi′lum), the indented region on the concave side, via efferent lymphatic vessels.

What is lymph? Where does it come from?

Lymph is the fluid inside lymphatic vessels. It enters lymphatic vessels from interstitial fluid. Interstitial fluid, in turn, is a filtrate of blood plasma.

What is the driving force for lymph movement?

Lymph movement is driven by the contraction of adjacent skeletal muscles, pressure changes in the thorax during breathing, the pulsations of nearby arteries, and contraction of smooth muscle in the lymphatic vessel walls. (Valves in lymphatic vessels prevent backflow of lymph.)

What is a lymphoid follicle? What type of lymphocyte predominates in follicles, especially in their germinal centers?

Lymphoid follicles are solid, spherical bodies consisting of tightly packed reticular fibers and lymphoid cells, often with a lighter-staining central region. They are regions where B cells predominate.

______ helps protect us from the never-ending onslaught of pathogens that seek to enter our bodies.

MALT

prevents pathogens from penetrating mucous membrane, site for lymphocyte activation and proliferation

MALT

diffusely distributed collections of lymphoid tissue in the mucous membranes

MALT (mucosa- associated lymphoid tissue)

play a crucial role in body protection and the immune response by phagocytizing foreign substances and by helping to activate T cells.

Macrophages

Both B and T cells originate in red bone marrow. Where do you find red marrow in adults?

Red bone marrow in adults is found in the cavities between trabeculae of spongy bones in the flat bones of the skull, the sternum, ribs, clavicles, scapulae, hip bones, and vertebrae. In addition it is found in the heads of the femur and humerus.

lymph sinuses

Spaces between these groups of lymphatic tissues. These spaces contain a network of fibers and the macrophage cells.

Activated ______ cells manage the immune response, and some of them directly attack and destroy infected cells.

T

lymphocytes that mediate cellular immunity; include helper, cytotoxic, regulatory, and memory cells

T cells (T lymphocytes)

two main varieties of lymphocytes

T cells (T lymphocytes) B cells (B lymphocytes)

A tumor in the left groin is blocking lymphatic drainage from Mr. Thomas's left leg, causing obvious edema. Which two of the functions of lymphatic vessels listed above no longer work in that leg? Think about the pressures driving bulk flow (Chapter 19 ) and state which two pressures are affected by the loss of these two lymphatic vessel functions and how the pressures are affected.

The blocked lymphatic vessels in Mr. Thomas's left leg no longer return excess tissue fluid or proteins to the bloodstream. The lack of fluid return from the tissues into the blood will result in a higher interstitial fluid hydrostatic pressure. This is an inward pressure, and will tend to help limit the edema. However, the lack of proteins being returned from the interstitial fluid to the blood will result in a higher interstitial fluid osmotic pressure, which will tend to pull more fluid into the tissue.

lymphatic capillary permeability it due to:

The endothelial cells forming the walls of lymphatic capillaries are not tightly joined. Instead, the edges of adjacent cells overlap each other loosely, forming easily opened, flaplike minivalves. Collagen filaments anchor the endothelial cells to surrounding structures so that any increase in interstitial fluid volume opens the minivalves, rather than causing the lymphatic capillaries to collapse.

What are the primary lymphoid organs and what makes them special?

The primary lymphoid organs are the red bone marrow and thymus. Primary lymphoid organs are special because they are the organs where lymphocytes originate and mature.

Name two lymphatic ducts and indicate the body regions usually drained by each.

The right lymphatic duct receives lymph from the right upper arm and the right side of the head and thorax. The thoracic duct drains lymph from the rest of the body.

List several functions of the spleen.

The spleen cleanses the blood, recycles breakdown products of RBCs, stores iron, stores platelets and monocytes, and is thought to be a site of erythrocyte production in the fetus.

From which blood vessel does the splenic artery arise? The splenic vein empties into which blood vessel?

The splenic artery arises from the celiac trunk. The splenic vein empties into the hepatic portal vein.

nerve that contains axons of sensory neurons and carries action potentials to the central nervous system

afferent (sensory)

Lymph enters the convex side of a lymph node through a number of____________

afferent lymphatic vessels.

____________ are anything that provokes an immune response, such as bacteria and their toxins, viruses, mismatched RBCs, or cancer cells.

antigens

is a tubular offshoot of the first part of the large intestine and contains a high concentration of lymphoid follicles

appendix

where are lymphatic capillaries absent from?

bones (including bone marrow) and teeth.

In about half of individuals, the thoracic duct begins as an enlarged sac, the _________________

cisterna chyli,

Lymph nodes have two basic protective functions:

cleansing the lymph immune system activation

The _____________ have the same three tunics as veins, but the collecting vessels have thinner walls and more internal valves, and they anastomose more

collecting lymphatic vessels

A lymph node has two histologically distinct regions:

cortex and medulla

capture antigens and bring them back to the lymph nodes

dendritic cells

a loose arrangement of lymphoid cells and some reticular fibers—is found in virtually every body organ. Larger collections appear in the lamina propria (loose connective tissue, p. 141) of mucous membranes such as those lining the digestive tract.

diffuse lymphoid tissue

carrying away or away from

efferent

lymphadenopathy.

enlarged lymph nodes

T/F: The stroma of the thymus consists reticular fibers.

false: The stroma of the thymus consists of epithelial cells rather than reticular fibers. These epithelial cells provide the physical and chemical environment in which T lymphocytes mature.

T/F: the thymus has follicles

false: the thymus has no follicles because it lacks B cells

the indented region of an organ from which blood and or lymphatic vessels and nerves enter and exit

hilum

In the thymus, T lymphocyte precursors mature to become__________________

immunocompetent lymphocytes.

lymphangitis

inflammation of lymphatic vessels

Cisterna chyli is located in the region between the __________________

last thoracic and second lumbar vertebrae.

The____________ is the collective term for a lumpy collection of lymphoid follicles at the base of the tongue.

lingual tonsil

Lymphatic capillaries weave between the tissue cells and blood capillaries in the ________________ of the body

loose connective tissues

The major trunks, named mostly for the regions from which they drain lymph, are the paired _____________________________________________________________

lumbar, bronchomediastinal, subclavian, and jugular trunks, and the single intestinal trunk

protein- containing fluid transported by lymphatic vessels

lymph (clear water)

small lymphoid organ that filters lymph; contains macrophages and lymphocytes

lymph node

cleanse lymph, site for lymphocyte activation and proliferation

lymph nodes

secondary lymphoid organs include:

lymph nodes, the spleen, and the collections of mucosa-associated lymphoid tissue (MALT) that form the tonsils, Peyer's patches (aggregated lymphoid nodules) in the small intestine, and the appendix.

The transport of lymph begins in microscopic blind-ended ___________

lymphatic capillaries

transports absorbed fat from the small intestine to the bloodstream

lymphatic capillaries called LACTEALS

returns fluids that have leaked from the vascular system back to the blood.

lymphatic system

The largest collecting vessels unite to form _________________, which drain fairly large areas of the body.

lymphatic trunks

general term used to designate the lymphatic vessels that collect and transport lymph

lymphatics

agranular white blood cells that arises from bone marrow and becomes functionally mature in the lymphoid organs of the body (main warriors of immune system)

lymphocyte

are solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers.

lymphoid follicles (lymphoid nodules)

-provide structural basis of the immune system -play essential roles in the body's defense mechanisms and its resistance to disease.

lymphoid organs and tissues

Houses lymphocytes and provides a site where they can be activated and proliferate (multiply) Furnishes an ideal surveillance vantage point for lymphocytes and macrophages

lymphoid tissue

The paired _____________ are located on either side at the posterior end of the oral cavity. These are the largest tonsils and the ones most often infected.

palatine tonsils

lymphoid organs located in the small intestine; also called aggregated lymphoid nodules

peyer's patches

The ________ (referred to as the adenoids if enlarged) is in the posterior wall of the nasopharynx.

pharyngeal tonsil

Members of a B cell clone; effector B cells specialized to produce and release antibodies.

plasma cells

tonsillar crypts

portion of tonsils that trap and destroy bacteria and particulate matter.

the appendix is in an ideal position to __________________

prevent bacteria (present in large numbers in the intestine) from breaching the intestinal wall, and (2) to generate many "memory" lymphocytes for long-term immunity.

are where B and T cells mature—the red bone marrow and the thymus.

primary lymphoid organs

While both B and T cells originate in the red bone marrow, B cells mature in the________________ and T cells mature in the ____________

red bone marrow, thymus

is where worn-out red blood cells and bloodborne pathogens are destroyed, so it contains huge numbers of erythrocytes and the macrophages that engulf them. It is essentially all splenic tissue that is not white pulp. It consists of splenic cords, regions of reticular connective tissue, that separate the blood-filled splenic sinusoids (venous sinuses).

red pulp

fibroblast-like cells that produce the reticular fiber stroma (stro′mah), which is the network that supports the other cell types in lymphoid organs and tissues

reticular cells

connective tissue with a fine network of reticular fibers that form the internal supporting framework or lymphoid organs

reticular connective tissue

drains lymph from the right upper limb and the right side of the head and thorax

right lymphatic duct

are where mature lymphocytes first encounter their antigens and are activated.

secondary lymphoid organs

cleanses blood and removes aged or defective red blood cells, site for lymphocyte activation and proliferation, stores platelets, monocytes and iron

spleen

largest lymphoid organ

spleen

largest lymphoid organ, provides a site for immune surveillance, lymphocyte activation, and erythrocyte destruction

spleen

lymphoid organs and tissues include

spleen, thymus, tonsils, and other lymphoid tissues scattered throughout the body.

what serves the spleen?

splenic artery and vein, which enter and exit the hilum on its slightly concave anterior surface.

splenectomy

surgical removal of the spleen

lymphedema

swelling due to an abnormal accumulation of lymph fluid within the tissues

buboes

swollen lymph nodes

Where is the spleen located?

the left side of the abdominal cavity just beneath the diaphragm, it curls around the anterior aspect of the stomach

Recycles the breakdown products of red blood cells for later reuse. It releases the breakdown products to the blood for processing by the liver and stores some of the iron salvaged from hemoglobin. Stores blood platelets and monocytes for release into the blood when needed. May be a site of erythrocyte production in the fetus.

the spleen

large lymphatic duct that receives lymph drained from the entire lower body, the left upper extremity, and the left side of the head and thorax

thoracic duct

It is found in the inferior neck and extends into the superior thorax, where it partially overlies the heart deep to the sternum

thymus

Prominent in newborns, the________ continues to increase in size during the first year, when it is highly active. After puberty, it gradually atrophies and by old age it has been replaced almost entirely by fibrous and fatty tissue and is difficult to distinguish from surrounding connective tissue

thymus

Site of T cell maturation

thymus

lymphoid organ active In immune response; site of maturation of T lymphocytes

thymus

A Ring of Lymphoid tissue around the entrance of the pharynx is

tonsils

The___________ gather and remove many of the pathogens entering the pharynx in food or in inhaled air.

tonsils

largest collections of MALT

tonsils, peyer's patches, appendix

(1) Any of the fibrous bands extending from the capsule into the interior of an organ; (2) strut or thin plate of bone in spongy bone.

trabeculae

Each node is surrounded by a dense fibrous capsule from which connective tissue strands called__________ extend inward to divide the node into a number of compartments

trabeculae

T/F: Anything that prevents the normal return of lymph to the blood—such as when tumors block the lymphatics or lymphatics are removed during cancer surgery—results in short-term but severe localized edema (lymphedema)

true

T/F: As lymph is transported back to the bloodstream, the lymph nodes act as lymph "filters." Macrophages in the nodes remove and destroy microorganisms and other debris that enter the lymph from the loose connective tissues, preventing them from being delivered to the blood and spreading to other parts of the body.

true

T/F: Lymph nodes and other lymphoid organs are strategically located sites where lymphocytes encounter antigens and are activated to mount an attack against them. Many antigens are brought to lymph nodes from their point of entry into the body by dendritic cells. Dendritic cells use these antigens to activate T cells in the lymph nodes.

true

t/F: The thymus does not directly fight antigens. Instead, the thymus functions strictly as a maturation site for T lymphocyte precursors. These precursors must be kept isolated from foreign antigens to prevent their premature activation. In fact, there is a blood thymus barrierthat keeps bloodborne antigens out of the thymus.

true

The tiny ___________ surround the openings of the auditory tubes into the pharynx.

tubal tonsils

Like the larger blood vessels, the larger lymphatics receive their nutrient blood supply from a branching _____________

vasa vasorum.

thymic corpuscles

where regulatory T cells develop

is where immune functions take place, so it is composed mostly of lymphocytes suspended on reticular fibers. The ______ clusters or forms "cuffs" around central arteries (small branches of the splenic artery). These clusters of white pulp look like islands in a sea of red pulp.

white pulp

the spleen consists of two components

white pulp and red pulp