Chapter 20- Lymphatic system

Lymph Transport

- Lymph system is a low-pressure system like venous system Lymph is propelled by : -Milking action of skeletal muscle -Pressure changes in thorax during breathing -Valves to prevent backflow -Pulsations of nearby arteries -Contractions of smooth muscle in walls of lymphatics Physical activity increases flow of lymph; Immobilization of area keeps needed inflammatory material in area for faster healing

Lymphoid organs and tissues

- structural basis of immune system houses phagocytic cells and lymphocytes - Structures include spleen, thymus, tonsils, lymph nodes, other lymphoid tissues

lymphoid tissue

-Houses and provides proliferation sites for lymphocytes -Offers surveillance Largely composed of reticular connective tissue, a type of loose connective tissue

Distribution and Structure of Lymphatic Vessels

-Lymphatic vessels offer a one-way system, ensuring lymph flows only towards heart -Lymph vessels (lymphatics) include: ---Lymphatic capillaries ---Larger lymphatic vessels

chyle

=juice fatty lymph drains from villi of intestinal mucosa

structure lymph node

Afferent lymphatic vessels Cortex Lymphoid follicle Germinal center Subcapsular sinus Efferent lymphatic vessels Hilum Medulla Medullary cord Medullary sinus Trabeculae Capsule

true

Because lymph vessels are very low-Pressure conduits, movements of adjacent tissues are important in propelling lymph through the lymphatics. True or False

Developmental Aspects of the Lymphatic System

Beginnings of lymphatic vessels and main clusters of lymph nodes seen by week 5 of embryonic development - Arise as lymph sacs from developing veins - Jugular lymph sacs arise to form right lymphatic duct and thoracic duct Lymphoid organs (except thymus) develop from mesodermal mesenchymal cells Thymus (endodermal origin) forms as an outgrowth of pharynx Except for spleen and tonsils, lymphoid organs are poorly developed at birth After birth, high numbers of lymphocytes appear; their development parallels maturation of immune system

lymph and blood pathways

Blood Heart -> arterial system -> capillaries -> venous system -> heart Lymphatic system: - Lymphatic capillary - Collecting lymphatic vessels,with valves - Lymph node - Lymphatic trunk - Lymphatic duct - heart CHECK THIS.....

true

Chyle is delivered to the blood via the lymphatic system True or False

d. The thymus

Collections of lymphoid tissue (MALT) that guard mucosal surfaces include all of the following except a. Appendix follicles b .The tonsils c. Peyer's patches d. The thymus

(d) the thymus.

Collections of lymphoid tissue (MALT) that guard mucosal surfaces include all of the following except (a) appendix follicles, (b) the tonsils, (c) Peyer's patches, (d) the thymus.

true

Digested fats are absorbed from the intestine by the lymph capillaries. True or False

a. One-way mini-valves formed by overlapping endothelial cells

Entry of lymph into the lymphatic capillaries is promoted by which of the following? a. One-way mini-valves formed by overlapping endothelial cells b. The respiratory pump c. The skeletal muscle pump d. Greater fluid pressure in the interstitial space

(a) one-way minivalves formed by overlapping endothelial cells,

Entry of lymph into the lymphatic capillaries is promoted by which of the following? (a) one-way minivalves formed by overlapping endothelial cells, (b) the respiratory pump, (c) the skeletal muscle pump, (d) greater fluid pressure in the interstitial space.

Circulation in the Lymph Nodes

Lymph enters into Afferent lymphatic vessels subcapsular sinus smaller sinuses (found throughout cortex and medulla) medullary sinuses Efferent lymphatic vessels NOTE; presence of fewer efferent vessels causes flow to somewhat stagnate, allows lymphocytes and macrophages time to function

false

Lymph from the entire body drains eventually into the thoracic duct. True or False

a. The brain

Lymph nodes are densely clustered in all of the following body areas except a. The brain b. The axillae c. The groin d. The cervical region

False

Lymph nodes are populated by B cells but not T cells. True or False

lymphatic capillary - filaments

Lymphatic capillaries are blind-ended tubes in which adjacent endothelial cells overlap each other, forming flaplike minivalves. Filaments anchored to connective tissue endothelial cell flaplike minivalve fibroblase in loose connective tissue

True

Lymphatic capillaries are more permeable than blood capillaries. True or False

true

Lymphatic capillaries are permeable to proteins. True or False

c) Transport leaked plasma proteins and fluids to the cardiovascular system

Lymphatic vessels a) Serve as sites for immune surveillance b) Filter lymph c) Transport leaked plasma proteins and fluids to the cardiovascular system d) Are represented by vessels that resemble arteries, capillaries and veins

Mucosa - associated lymphoid tissue (MALT)

Lymphoid tissues in mucous membranes throughout body Protects from pathogens trying to enter body Found in mucosa of respiratory tract, genitourinary organs, and digestive tract; largest collections of MALT found in -Tonsils -Peyer's patches -Appendix

Lymphoid organs are grouped into two functional categories

Primary lymphoid organs Secondary lymphoid organs primary - where B and T cells mature 1. thymus 2. red bone marrow secondary - where mature lymphocytes first encounter their antigens and are activated 1. lymph nodes 2. tonsils - (collection of mucosa-associated lymphoid tissue MALT) 3. spleen 4. peyers patches (aggregated lymphoid nodules in Small intestine) 5. appendix

lymph node

Reticular cells on reticular fibers Macrophage medullary sinus lymphocytes reticular fibers

Lymphatic trunk

Right jugular trunk Right lymphatic duct Right subclavian trunk Right broncho-mediastinal trunk Cisterna chyli Right lumbar trunk Left jugular trunk Left subclavian trunk Left broncho-mediastinal trunk Thoracic duct Left lumbar trunk intestinal trunk

Tonsils

Simplest lymphoid organs Form ring of lymphatic tissue around pharynx; appear as swellings of mucosa Named according to location - Palatine tonsils - Lingual tonsil - Pharyngeal tonsil - Tubal tonsils Tonsil function -gather and remove pathogens in food or inhaled air Tonsillar crypts- Bacteria or particulate matter are trapped and destroyed

Peyer's patch (aggregated lymphoid nodules).

Smooth muscle in the distal section of small intestinal wall Follicles of a Peyer's patch (aggregated lymphoid nodules) structurally similar to tonsils

false

The cisterna chyli collects lymph from the lumbar trunks draining the upper limbs and from the intestinal trunk draining the digestive organs True or False

(b) proliferating B lymphocytes,

The germinal centers in lymph nodes are largely sites of (a) macrophages, (b) proliferating B lymphocytes, (c) T lymphocytes, (d) all of these.

(a) more permeable than blood capillaries,

The lymphatic capillaries are (a) more permeable than blood capillaries, (b) less permeable than blood capillaries, (c) as permeable as blood capillaries, (d) completely impermeable.

true

The lymphatic capillaries function to absorb the excess protein -containing interstitial fluid and return it to the bloodstream. True or False

b. Thymus

The lymphoid organ that functions primarily during youth and then begins to atrophy is the a. Spleen b. Thymus c Palatine tonsils d. Bone marrow

(b) thymus,

The lymphoid organ that functions primarily during youth and then begins to atrophy is the (a) spleen, (b) thymus, (c) palatine tonsils, (d) bone marrow.

false

The most important role of the spleen is to provide a site for lymphocyte proliferation and immune surveillance and response. True or False

a. Splenic sinusoids, macrophages and red blood cells

The red pulp areas of the spleen are sites of a. Splenic sinusoids, macrophages and red blood cells b Clustered lymphocytes c. Connective tissue septa

c) cisterna chyli

The saclike initial portion of the thoracic duct is the a) lacteal b) right lymphatic duct c) cisterna chyli d) lymph sac

(c) reticular tissue,

The structural framework of lymphoid organs is (a) areolar connective tissue, (b) hematopoietic tissue, (c) reticular tissue, (d) adipose tissue.

c). Reticular tissue

The structural framework of lymphoid organsis: a). Areolar connective tissue b). Hematopoietic tissue c). Reticular tissue d). Adipose tissue

True

The two functions of the lymphatic system are the maintenance of fluid balance in the internal environment and immunity. True or False

true

The white pulp of the spleen gets its colour mainly from lymphocytes and macrophages True or False

false

There are more efferent lymphatic vessels leaving a lymph node than there are afferent vessels entering a lymph node. True or False

false

Tonsillectomy is regarded as the current treatment of choice for most cases of tonsillitis. True or False

Lymphoid Organs

Two main types of lymphoid tissues - Diffuse lymphoid tissue: loose arrangement of lymphoid cells and some reticular fibers --Found in virtually every body organ --Larger collections in lamina propria of mucous membranes - Lymphoid follicles (nodules): solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers --Contain germinal centers of proliferating B cells --May form part of larger lymphoid organs (nodes) --Isolated aggregations in Peyer's patches and in appendix

(c) right lymphatic duct,

Which lymphatic structure drains lymph from the right upper limb and the right side of the head and thorax? (a) lumbar trunk, (b) thoracic duct, (c) right lymphatic duct, (d) cisterna chyli.

antigens

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

Thymus

bilobed lymphoid organ found in inferior neck Functions as lymphoid organ where T cells mature Thymus is broken into lobules that contain - outer Cortex and inner Medulla - differs from other lymphoid organs as: -- Has no follicles -- Does not directly fight antigens -- Stroma is made up of epithelial cells, not reticular fibers -- blood thymus barrier that keeps bloodborne antigens out of the thymus most active and larges in size during childhood

Lymphatic capillaries

blind-ended tubes in which adjacent endothelial cells overlap each other, forming flaplike minivalves. - very permeable

special features of lymphatic capillaries

collagen Filaments anchor endothelial cells to connective tissue/surrounding structures Endothelial cells forming walls are not tightly joined, instead they overlap to form Flaplike minivalves Fibroblast in loose connective tissue

lingual tonsil

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

Lymphangitis

condition in which lymphatic vessels appear as painful red lines under the skin Caused by inflammation of larger lymphatic vessels that contain vaso vasora - Vaso vasora become congested with blood - Larger lymphatics, like blood vessels, receive their nutrients from branching vasa vasorum

Macrophages

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

right lymphatic duct

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

cisterna chyli

enlarged sac located in the region between the last thoracic and second lumbar vertebrae appears in approx 50% individuals, where the thoracic duct begins as an enlarged sac

Pathway of lymph

enters the convex side of a lymph node through afferent lymphatic vessels. moves through a large, baglike sinus, the subcapsular sinus, into smaller sinuses that cut through the cortex and enter the medulla. through medullary sinuses exits the node at its hilum (indented region on the concave side), via efferent lymphatic vessels.

Buboes

inflamed, swollen, tender lymph nodes that result when nodes are overwhelmed by what they are trying to destroy Condition often referred to as swollen "glands" Buboes are sometimes pus-filled Bubonic plague was named after chief clinical feature of this disease Lymph nodes can become secondary cancer sites if metastasizing cancer cells become trapped in node

Spleen

largest lymphoid organ -Site of lymphocyte proliferation -Cleanses blood of aged cells removes debris -Stores breakdown products of RBCs (e.g., iron) for later reuse -Stores blood platelets and monocytes for release into blood when needed -May be site of fetal erythrocyte production Spleen is encased by fibrous capsule and also has trabeculae Histologically, consists of two components White pulp Red pulp The spleen has a thin capsule, so direct blow or severe infection may cause it to rupture, spilling blood into peritoneal cavity

pharyngeal tonsil

located posterior wall of the nasopharynx referred to as adenoids if enlarged

lymphatic system

lymphatic duct lymphatic trunk lymph node collecting lymphastic vessels with valves Lymphatic capillaries are blind-ended tubes in which adjacent endothelial cells overlap each other, forming flaplike minivalves.

functions of Lymph nodes

principal secondary lymphoid organs of body Two main functions of lymph nodes 1. Cleansing the lymph: act as lymph "filters" 2. Immune system activation: offer a place for lymphocytes to become activated and mount an attack against antigens

B cells

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

Lymphatic system

returns fluids leaked from blood vessels back to blood; consists of three parts 1. Network of lymphatic vessels (lymphatics) 2. Lymph: fluid in vessels 3. Lymph nodes: cleanse lymph

Lymphedema

severe localized edema Caused by anything that prevents normal return of lymph to blood Examples: tumors blocking lymphatics or removal of lymphatics during cancer surgery Lymphedema may improve if some lymphatic pathways remain and enlarge

Splenectomy

surgical removal of ruptured spleen If spleen must be removed, liver and bone marrow take over most of its functions In children younger than 12, spleen will regenerate if a small part is left

tubal tonsils

surround the openings of the auditory tubes into the pharynx.

lymphatic capillary

tissue fluid tissue cell blood capillaries lymphatic capillaries

Appendix

tubular offshoot of first part of large intestine Contains a large number of lymphoid follicles Location aids in functions (like Peyer's patches) 1. Destroy bacteria, preventing them from breaching intestinal wall 2. Generate "memory" lymphocytes

lymph nodes unlikely to react to cancer

what is the difference between cancer infected nodes and microogranism infected node

White pulp of spleen

where immune functions take place composed mostly of lymphocytes suspended on reticular fibers. clusters or forms "cuffs" around central arteries (small branches of the splenic artery).

Red pulp of spleen

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

Lymphatic trunks

which are formed by union of largest collecting vessels, drain large areas of body drain fairly large areas of the bodu Named for regions of body they drain: -Paired lumbar -Paired bronchomediastinal -Paired subclavian -Paired jugular trunks -Single intestinal trunk

true

Most plasma cells form in the germinal centers of the lymph nodes. True or False

True

Obstruction of a major lymphatic vessel is likely to cause edema. True or False

lymph

Once interstitial fluid enters lymphatics, it is called lymph (LYMPH = CLEAR WATER)

TRUE

One of the main differences between lymph and interstitial fluid is that lymph is in vessels. True or False

Lymphocytes

T cells (T lymphocytes) and B cells (B lymphocytes)—that protect the body against antigens.

b.Proliferating B lymphocytes

The germinal centers in lymph nodes are largely sites of a. Macrophages b.Proliferating B lymphocytes c. T lymphocytes d.all of these

reticular cells

fibroblast-like cells that produce the reticular fiber stroma

collecting lymphatic vessels

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

lymph sinuses

large lymphatic capillaries spanned by crisscrossing reticular fibers contain numerous macrophages

thoracic duct

larger - receives lymph from the two large lumbar trunks that drain the lower limbs and from the intestinal trunk that drains the digestive organs.

Activated T cells

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

antibodies

mark antigens for destruction

stroma

network that supports the other cell types in lymphoid organs and tissues

palatine tonsils

paired located on either side at the posterior end of the oral cavity. largest tonsils most often infected.

(b) forming crypts that trap bacteria,

Functions of the spleen include all of those below except (a) removal of old or defective blood cells from the blood, (b) forming crypts that trap bacteria, (c) storage of blood platelets, (d) storage of iron.

Lymphoid Cells

Immune system cells --T cells: attack and destroy infected cells --B cells: produce plasma cells, which secrete antibodies --Other lymphoid immune cells ----Macrophages ----Dendritic cells Supporting lymphoid cell - Reticular cells produce reticular fibers called stroma in lymphoid organs

false

In the spleen, red pulp is involved in the immune functions and white pulp is involved in disposing of worn out RBCs. True or False

(d) lower extremities.

Large clusters of lymph nodes occur in all of the following locations except the (a) inguinal region, (b) cervical region, (c) axillary region, (d) lower extremities.

false

Like blood, lymph flows both to and from the heart. .True or False

true

Lymphatic nodules are permanent structures enclosed in fibrous capsules True or False

Structure of a Lymph Node

Vary in shape and size, but most are bean shaped - Small, less than 2.5 cm (~1 inch) Surrounded by external fibrous capsule Capsule fibers extend inward as trabeculae that divide node into compartments Two histologically distinct regions of node: 1. Cortex 2. Medulla

dendritic cells

capture antigens and bring them back to the lymph nodes. spiny-looking

lacteals

specialized lymph capillaries present in intestinal mucosa that transport absorbed fat from the small intestine to the bloodstream