What is the lymphatic system?
Returns fluid that have leaked from the vascular system back to the blood
What does the lymphatic system consist of?
-A meandering network of lymphatic vessels
-Lymph (fluid contained in those vessels)
-Lymph Nodes (cleanse the lymph as it passes through them)
What do lymphoid organs consist of?
Spleen, thymus, tonsils, and other tissues scattered throughout the body
What are lymphatic vessels?
-elaborate network of drainage vessels
Once interstitial fluid enters lymphatics, what is it called?
What are lymphatic capillaries?
these capillaries are blind-ended vessels that weave between tissue cells and blood capillaries in the loose connective tissues of the body
Where are lymphatic capillaries absent from?
Bones, teeth, bone marrow and CNS (CNS uses CSF for drainage)
Why are lymphatic capillaries so remarkably permeable?
-Endothelial cells form loosely joined lymphatic walls, they overlap and are easily opened, like mini valves
-Collagen filaments anchor the endothelial cells, so any increase in ECF (interstitial fluid) opens the mini valves rather than causing the lymphatic capillaries to collapse
What is the immune system analogous to?
one way swinging doors
What are lacteals?
special set of lymphatic capillaries that transport absorbed fat from the small intestine to the bloodstream.
Why are lacteals called, lacteals?
Because of the milky white lymph that drains through them (lact= milk)
This fatty lymph, is called chyle ("juice") and it drains from the fingerlike villi of the intestinal mucosa.
What are collecting lymphatic vessels (CLV)?
From the lymphatic capillaries, lymph flows through larger channels and finally to the ducts. CLV have same three tunics as veins, but they anastomose more frequently .
In general lymphatics in skin travel along w superficial veins and deep lymphatic vessels in trunk and digestive viscera travel w deep arteries.
What do lymphatic trunks do?
Drain large parts of body
-the major trunks are named mostly for the region for which they drain lymph
ex: paired lumbar, bronchomediastinal, subclavian, jugular trunks and the single intestinal trunk
What does the right lymphatic duct drain?
drains lymph from the right upper limb and the right side of the head and thorax
the *much* larger thoracic duct drains?
receives lymph from the rest of the body . It collects lymph from the two large lumbar trunks that drain the lower limbs and from the intestinal trunk that drains the digestive organs
Where does the thoracic duct begin in about half of the individuals?
the cisternal chyli (an enlarged sac)
What is lymphangitis?
associated lymphatics become visible through the skin as red lines that are tender to the touch
What is lymphedema?
severe localized edema
caused by anything that prevents the normal return of lymph to blood
ex: tumors blocking lymphatics or removal of lymphatics during cancer surgery
(T/F) the lymphatic system is a low pressure system like the venous system
What is lymph propelled by?
-milking acting of the skeletal muscles
-pressure changes in the thorax during breathing
-valves to prevent backflow
-pulsations of nearby arteries
-contractions of smooth muscle in walls of lymphatics
Why do we immobilize infected parts of body?
Physical activity increases flow of lymph, so immobilization of the area keeps inflammatory material in area for faster healing
What are lymphocytes? What are the 2 types?
cells of the adaptive immune system; mature into
that protect body from antigens
REFRESHER: What are antigens?
anything that provokes an immune response/ body perceives as foreign
ex: mismatched blood, bacteria, viruses,cancer cells
What do T cells manage?
manage immune response, and also attack and destroy infected cells
What do B cells manage?
produce plasma cells which secrete antibodies into blood
REFRESHER: What are antibodies?
mark antigens for destruction by phagocytosis or other means
What are macrophages?
play a crucial role in body protection and the immune response by phagocytizing foreign substances and by helping activate t cells
What are dendritic cells?
capture antigens and deliver them to lymph nodes ; also help activate T cells
What are reticular cells?
produce the reticular fiber stroma which is a network that supports the other cell types in lymphoid organs and tissues aka its a scaffold for other cells
What are the functions of lymphoid tissue?
-House and provides a proliferation site for lymphocytes
-Furnishes an ideal surveillance vantage point for lymphocytes and macrophages as they filter through the lymph
Vocabulary word- Proliferation: rapid and repeated production
What is lymphoid tissue largely composed of
reticular connective tissue
-macrophages live on the fibers of the reticular connective tissue
-space bwtn fibers offers a place for lymphocytes to occupy when they return from patrolling the body
What are the 2 types of main lymphoid tissues?
Diffuse lymphoid tissue
Lymphoid follicles (nodules)
What is diffuse lymphoid tissue?
a loose arrangement of lymphoid cells and some reticular fibers- found in virtually every body organ
What are lymphoid follicles?
solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers
often have germinal centers where B cells proliferate
What are primary lymphoid organs?
where t and B cells mature
red bone marrow and thymus
B cells mature in red Bone marrow
T cells mature in Thymus
What are secondary lymphoid organs?
where mature lymphocytes first encounter their antigens and are activated
lymph nodes, spleen, appendix, tonsils (MALT), peters patches in the small intestine
lymphocytes encounter their antigens and are activated in the diffuse lymphoid tissue
What is the most important secondary lymph nodes in the body?
What are the lymph nodes' 2 basic protective functions?
1. Cleansing the lymph: they act as "filters" of lymph. macrophages in lymph destroy and remove microorganisms that enter lymph from the loose connective tissue, preventing spreading
2. Immune System activation: where lymphocytes encounter antigens and are activated to mount an attack against them
What is the structure of a lymph node?
Less than 1 inch in length
surrounded by an external fibrous capsule
capsule fibers extend inward as trabeculae that divide node compartments
What are the 2 histologically distinct parts of a lymph node?
Superficial area contains follicles w/ germinal cells that are HEAVY with dividing B cells
Deep cortex houses T cells in transit
Dendritic cells are abundant in the cortex and intimately associated w both T&B cells
medullary cords are thin inward extensions from the cortical lymphoid tissue and contain both types of lymphocytes
What are lymph sinuses?
dispersed throughout the node
sinuses are large lymphatic capillaries spanned by crisscrossing reticular fibers.
numerous macrophages reside in these reticular fibers and phagocytize foreign matter in the lymph