bio 211 lecture 1 Lymphatic system

lymphatic capillaries

Absent from bones, teeth, bone marrow, and CNS

endothelial cells

(lymphatic capillaries) overlap loosely to form one-way minivalves

dendritic cells

(structure of lymph node) nearly encapsulate follicles

tonsils

- Simplest lymphoid organs; -form a ring of lymphatic tissue around the pharynx -gather and remove pathogens in food or air - there are four tonsils (palatine, lingual, pharyngeal, tubal)

lymphatic collecting vessels

-Collecting vessels in the skin travel with superficial veins -Deep vessels travel with arteries -Nutrients are supplied from branching vasa vasorum

lymph sacs

Developed by the 5th week of embryonic development, the beginning of lymphatic vessels and main clusters of lymph nodes and buds from developing veins. - jugular lymph sacs arise → right lymphatic duct and thoracic duct

lymph transport

Lymph 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

t cells

Manage the immune response Attack and destroy foreign (infected) cells

antigens

T cells and B cells protect against ___

lymphocytes

after birth there are high numbers of ___ ; their development parallels maturation of immune systems

antigens

anything the body perceives as foreign (bacteria and bacterial toxins, viruses, mismatched RBCs, cancer cells)

white pulp

area of spleen around central artery, mostly lymphocytes on reticular fivers; involved in immune functions

thoracic duct

arises as cisterna chyli; drains rest of body

palatine tonsils

at posterior end of oral cavity

dendritic cells

capture antigens and deliver them to lymph nodes

t cells

circulate continuously amount blood, lymph nodes, and lymph

Peyer's patches

clusters of lymphoid follicles in wall of distal portion of small intestine similar structures are also found in the appendix

lymph sinuses

contain macrophages

thymic medulla

contains fewer lymphocytes and thymic corpuscles involved in regulatory t cell development (prevent autoimmunity)

thymic cortex

contains rapidly dividing lymphocytes and scattered macrophages

cortex

deep __ of the lymph node houses t cells in transit

Peyer's patches and appendix

destroy bacteria, preventing them from breaching intestinal wall generate "memory" lymphocytes

thymus

differs from other lymphoid organs in important way - has no follicles because it lacks in b cells - does not directly fight antigens (functions strictly in t lymphocyte maturation) - keeps isolated via blood thymus barrier

lymphoid tissue

diffuse lymphoid tissue of lymphoid cells and reticular fiber in every body organ - larger collections in lamina propria of mucous membranes

right lymphatic duct

drains right upper arm and right side of head and thorax

lymph

enters convex side via afferent lymphatic vessels; travels through large subcapsular sinus and smaller sinuses to medullary sinuses, exits concave side at hilum via efferent vessels

spleen and tonsils

except for the ___ lymphoid organs poorly developed at birth

medullary cords

extend inward from cortex and contain b cells, t cells, and plasma cells

lymphatic trunks

formed by the union of the largest collecting ducts ▫︎paired lumbar ▫︎paired bronchomediastinal ▫︎paired subclavian ▫︎paired jugular trunks ▫︎single intestinal trunk

thymus

forms as an outgrowth of pharynx

spleen

function site of lymphocyte proliferation and immune surveillance and response cleanses blood of aged cells and platelets, macrophages remove debris

lymph node

functions include ▫︎filter lymph- macrophages destroy microorganism and debris ▫︎immune system activation- lymphocytes activated and mount attack against antigens

lingual tonsils

grouped at base of tongue

red pulp

in spleen, in venous sinuses and splenic cords. is rich in RBC's and macrophages for disposal of worn-out RBCs and blood-borne pathogens is composed of splenic cords and sinusoids

lymph vessels

include ▫︎lymphatic capillaries ▫︎collecting lymphatic vessels ▫︎lymphatic trunks and ducts

lymphoid tissue

largely reticular connective tissue- type of losose connective tissue

spleen

largest lymphatic organ served by splenic artery and vein, which enter and exit at the hilum

lymphatic ducts

lymph delivered into one of two large ducts ▫︎right lymphatic duct ▫︎thoracic duct each empties lymph into venous circulation at junction of internal jugular and subclavian circulation at junction of internal jugular and subclavian vines on its own side of the body

cortex

lymph node __ contains follicles with ferminal centers, heavy with dividing b cells

one

lymphatic distribution is a __ way system; lymph flows towards the heart

mesoderm

lymphatic organs (except thymus) arise from

mesodermal

lymphoid organs (except thymus) develop from ____ mesenchymal cells

Mucosa-associated lymphoid tissue (MALT)

lymphoid tissue in mucous membranes throughout body protects from pathogens trying to enter body largest collections of MALTH are in the tonsils, peyers patches, appendix, also in mucosa of respiratory and genitourinary organs; rest of digestive tract

lymphocytes

main warriors of immune system, arise in red bone marrow

antibodies

mark antigens for destruction by phagocytosis or other means

lymphoid cells

mature into one of two main varieties ▫︎ t cells (t lymphocytes) ▫︎ b cells ( b lymphocytes)

stroma

of epithelial cells (no reticular fibers) provide environment in which t lymphocytes become immunocompetent (mature)

lymph

once interstitial fluid enters lymphatics its called

appendix

peyers patches are located in the

macrophages

phagocytize foreign substances; help activate t cells

pharyngeal tonsil

posterior wall of nasopharynx

b cells

produce plasma cells, which secrete antibodies

reticular cells

produce reticular fiber stroma that supports other cells in lymphoid organs

lymphatic vessels

return intersitial fluid and leaked plasma proteins back to blood, about 3l a day

lymphatic system

returns fluids that leaked from blood vessels back to blood ▫︎network of lymphatic vessels (lymphatics) ▫︎lymph- fluid in vessels lymph nodes- cleans lymph

lymphatic capillaries

similar to blood capillaries, except they are very permeable (take up proteins, cell debris, pathogens, and cancer cells) ▫︎endothelial cells overlap loosely to form one-way minivalves ▫︎anchored by collagen filaments, preventing collapse of lymphatic capillaries; increase in interstitial fluid volume (ECF) opens the mini-valve ▫︎pathogens travel throughout body via lymphatics

lymphatic collecting vessels

similar to veins except ▫︎have inner walls, with more internal valves ▫︎anastomose more frequently

lymphoid follicles (nodules)

solid, spherical bodies of tightly packed lymphoid cells and reticular fibers ▫︎germinal centers of proliferating B cells ▫︎ may form part of larger lymphoid organs ▫︎isolated aggregations of peyers patches in appendix

lacteals

specialized lymph capillaries present in intestinal mucosa - absorb digested fat and deliver fatty lymph (chyle) to the blood

tubal tonsils

surround the openings of the auditory tubes into the pharynx

lymph tissue

surveillance vantage point for lymphocytes and macrophages

efferent vessels

there are fewer _____ so flow is somewhat stagnate; allows lymphocytes and macrophages time to function

lymphoid tissue

there are two types diffuse lymphoid tissue and lymphoid follicles

efferent vessels

through what structure does lymph exit a lymph node?

thymus

thymic lobules contain outer cortex and inner medulla most thymic cells are lymphocytes

largest collection is in tonsils, peyer's patches, and appendix

which structures constitute MALT

thymus

▫︎ important functions early in life ▫︎ found in inferior neck; extend into mediastinum; particularly overlies heart ▫︎ increases in size and most active during childhood stops growing during adolescence, then gradually atrophies -still produces immunocompetent cells, though slowly

spleen

▫︎ stores breakdown products of RBCs for later reuse ▫︎ stores blood platelets and monocytes ▫︎ may be site of fetal erythrocyte production (normally cases before birth) ▫︎ encased in fibrous capsule; has trabeculae ▫︎ contains lymphocytes, macrophages, and huge number of erythrocytes

lymph node

▫︎ vary in shape and size but most are bean shaped ▫︎ have external fibrous capsule ▫︎ trabeculae extend inward and divide node into compartments ▫︎ they have two histologically distinct regions (cortex and medulla)

lymphoid orangs and tissues

▫︎provide structural basis of immune system ▫︎house phagocytic cells and lymphocytes ▫︎structures include the spleen, thymus, tonsils and other lymphoid tissue

tonsils

◻︎ contain follicles with germinal centers ◻︎ are not fully encapsulated ◻︎ overlying epithelium invaginated forming tonsillar crypts -trap and destroy bacteria and particulate matter - allow immune cells to building memory for pathogens

lymph tissue

Houses and provides a proliferation site for lymphocytes

lymph nodes

Principal lymphoid organs of body Embedded in connective tissue, in clusters along lymphatic vessels Near body surface in inguinal, axillary, and cervical regions of body