Chapter 20: Lymphatic system Flashcards
What are the general functions of the lymphatic system?
Return interstitial fluid and leaked proteins that are leaked out in the capillaries back to the cardiovascular system
Acts as the structural basis of the immune system
What is the fluid inside the lymphatic system called?
lymph
Where does the lymphatic system return the collected fluid?
to the venous system near the heart
Where are lymphatic capillaries not found in the body?
teeth, bones, marrow, and CNS
What are the two structural modifications in lymph capillaries that make them so much more permeable then vascular capillaries?
Cells of the endothelium overlap in such a way that they form one way, flap-like mini valves that open/close in response to pressure.
Collagen fibers secure them to their environment so that when interstitial pressure increases, it does not collapse.
What are lacteals and where are they found?
specialized lymph capillaries that absorb digested fats and deliver fatty lymph called CHYLE to the blood
villi of the small intestine
What is CHYLE?
fatty lymph found in the lacteals
What can be said about the general structure of the collecting vessels in the lymphatic system?
run parallel to blood vessels
walls are like veins
more valves and anastomoses
nutrients are provided by VASA VASORUM
vessels join to form lymphatic trunks
formed by joining lymph capillaries
What are the 7 major trunks of the lymphatic system?
R & L LUMBAR TRUNKS: drain legs
INTESTINAL TRUNK
R & L BRONCHOMEDIASTINALS, SUBCLAVIANS, JUGULARS: drain upper body and head
What are the two ducts in the lymphatic system?
RIGHT LYMPHATIC DUCT: drains lymph from right upper arm and right side of the head and thorax
THORACIC DUCT: receives lymph from the rest of the body
What is the cisterna chyli?
a sac like structure that collects lymph from the lumbar and intestinal trunks
marks the start of the thoracic duct
Where does the right lymphatic duct drain into?
junction of right internal jugular and subclavian vein
Where does the thoracic duct drain into?
junction of left internal jugular and subclavian vein
What is the rate of lymph transport?
3L / 24 hrs
How does the rate of lymph transport compare to that of veinous blood return?
slower
what does the movement of lymph depend on?
contraction of skeletal and respiratory muscles
pulsations of nearby arteries
contraction of smooth muscle in walls of trunks and thoracic duct
What is the condition known as LYMPHEDEMA?
swelling that results from blockage of lymph flow resulting in lymph accumulating distally from the blockage.
what are the 4 types of cells in the lymphoid system?
LYMPHOCYTES
MACROPHAGES
DENDRITIC CELLS
RETICULAR CELLS
What are the two sub-categories of lymphocytes? describe the role of each.
B CELLS: mature in the bone marrow and produce antibodies
T CELLS: mature in thymus and manage immune response. Some can attack and destroy infected/mutant cells directly. constantly patrol the blood, lymph, and lymph nodes
What are macrophages?
Strong phagocytes that destroy foreign antigens and help activate t cells
What are dendritic cells?
function as an early warning system that activate defense system by capturing antigens and delivering them to lymph nodes
What do reticular cells do in the lymph system?
form internal skeleton of lymphoid organs and tissue
produce the stroma that supports other cells
What is lymphoid tissue made of and what role does this play in the lymphatic system?
reticular connective tissue
- sites for lymphocyte reproduction
- sites for surveillance
- quick travel
What are the two types of lymphoid tissue?
DIFFUSE TISSUE
LYMPHOID FOLLICLES
What is diffuse tissue?
small scattered clusters of reticular tissue found in almost every organ
What is a lymphoid follicle?
a solid sphere of reticular elements and cells (no capsule)
contain germinal centers where b cells multiply and form plasma cells
may form groups or be scattered
What are PEYER’S PATCHES?
groups of lymphoid follicles found in the small intestine
What is another name for a lymphoid follicle?
nodule
What is the function of lymph nodes?
act as the first line of defense
1) macrophages filter and remove foreign particles from lymph (prevents them entering blood)
2) lymphocytes monitor and attack antigens (help to activate immune system)
Describe the structure of a lymph node.
bean shaped with outer capsule of dense CT
TRABECULAE: extend inwards from capsule and form compartments
CORTEX:
Outer - contains follicles wrapped in dendritic cells. follicles contain germinal centers for b-cells
Inner: contains t-cells in transit
MEDULLARY CORDS: extend inwards from the cortex. Contain b-cells, t-cells, and plasma cells
LYMPH SINUS: contain macrophages
Describe circulation through a lymph node?
afferent vessels - sub capsular sinus - smaller sinuses -> exits via efferent vessels at hilium
rate of flow is slower b/c fewer efferent (out) then afferent (in) vessels
What should you consider if your glands are enlarged?
two possible reasons:
swollen glands: nodes are infected and sore. Good sign that the defense system is working
metastasizing cancer: cancer cells are trapped in cells and replicate. swollen but not sore
What are the 5 larger lymphoid organs?
SPLEEN
THYMUS
RED BONE MARROW
TONSILS
MALT - aggregates of lymphoid follicles (mucosal associated lymphoid tissue)
What are the functions of the spleen?
A. site of lymphocyte proliferation and surveillance
B. cleans blood off old cells and foreign particles
C. stores some of the products of RBC breakdown for reuse (iron)
D. site of RBC production in the fetus
E. stores platelets (thrombocytes)
Describe the structure of the spleen.
It is a lot similar to a lymph node.
CAPSULE: with trabeculae and sinuses. quite thin and easily ruptured
WHITE PULP: mainly lymphocytes on reticular fibers that cluster around central arteries. immune functions
RED PULP: around venous sinuses and splenic cords. macrophages clean blood
What is the one organ in the lymphatic system that is not composed of reticular connective tissue?
the THYMUS
What is a splenectomy?
removal of the spleen
bone marrow and liver take over functions, but inc risk of infection
regeneration can occur in children if a small portion is left
describe the thymus’s structure
2 lobes divided into lobules.
OUTER CORTEX: has densely packed T cells and scattered macrophages
INNER MEDULLA: fewer lymphocytes, but contain HASSAL’s corpuscles that are made up of keratinized epithelial cells. site of t-cell destruction
STROMA: no reticular fibers. contains thymocytes which secrete thymosin and thymopoietin that causes t cells to become immunocompetent
What is a primary lymphoid organ?
organs in the lymphatic system where B and T cells multiply and mature
What is the only lymph organ with no B cells?
thymus
What is the role of red bone marrow in the lymphatic system?
PRIMARY lymphatic organ
site where B cells mature
What are the tonsils and what is their function?
simplest lymphoid organ
functions:
1) contain follicles with germinal centers for b-cell production
2) have crypts to trap and destroy bacteria/particles
3) important in early life; exposure to antigens builds an immune catalogue which improves immunity later
what are MALTs?
“mucosal associated lymphoid tissue”
PROTECT passages that open to the outside from invaders
MEMORY cells are generated to aid recognition of foreign cells
includes:
peyer’s patches, wall of appendix, in tonsils, nodules in walls of bronchi
What is the thymus’s role?
it is a primary lymphatic organ
that is:
site of t-cell multiplication and maturation.
What happens to the thymus as we age?
it increases in size from infanthood through childhood then atrophies
