Chapter 20: Lymphatic System Flashcards
What are the 4 main parts of the lymphatic system?
Network of lymphatic vessels
Lymph (fluid)
Lymphnodes
Lymph Organs
Name 4 primary functions of the lymphatic system?
Return interstitial fluid back to the blood
Return leaked plasma protein back to the blood
Part of the immune system
Production of lymph
What happens when interstital fluid enters the lymphatic vessels?
It is now called lymph
What are lymphatic vessels?
One-way system, carry fluid towards the heart
What are 3 types of lymphatic vessels and their size?
Lymphatic capillaries (smallest)
Lymphatic collecting vessels (medium)
lymphatic trunks and ducts (largest)
What are lymphatic capillaries?
Blind-ended tubes of adjacent endothelial cells that overlap and form small flap-like vales
Entwined within capillary beds
Where does all lymph travel?
Into one of two large lymphatic ducts - right lymphatic duct and thoracic duct
What does the right lymphatic duct drain?
Drains upper arm and right side of head and thorax
What is the thoracic duct?
Comes from the cisterna chyli and carries fluids that have been collected from the rest of the body
Where do the lymphatic ducts empty into? Why?
Venous circulation close to the heart where pressure is almost 0
What allows lymph transport? Name 3 things
pulsation of nearby arteries
contraction of smooth muscle in walls of the lymphatics
contraction of nearby skeletal muscles
What is the speed of lymphatic transport? How much lymph is returned to the blood stream each day?
Sporadic and slow
Roughly 3L/day
What are lymphoid cells? And what are the 2 main parts
Lymphocytes are the major warrior of the immune system
T cells and B Cells
What is the main function of t and b cells?
Protect against foreign antigens
What is the role of a t cell?
Manage immune response
Attack and destroy foreign cells
What is the role of a b cell?
Give rise and produce plasma cells
What is the function of a plasma cell? Who produces plasma cells?
Make antibodies
Produced by B cells
What are the 5 types of lymphoid cells
t cells b cells macrophages dendritic cells reticular cells
What is the role of macrophages?
Phagocytize foreign substances and help activate t-cells
What is the role of dendritic cells?
Capture antigens and deliver these to lymph nodes
What is the role of reticular cells?
Produce the stroma that supports other cells in lymphoid organs
What are the 2 main functions of lymphoid tissues?
House and provide proliferation site for lymphocytes
Vantage point for surveillance
What are the 2 main types of lymphoid tissue?
Diffuse Lymphatic Tissue Lymphatic Follicles (Also called lymphoid Follicles)
What is lymphatic tissue? Where is it found?
Made up of scattered reticular tissue
Found everywhere in the body
Describe lymphatic follicles? What do they do?
Solid spherical body, contain germinal center
Often form parts of larger lymphoid organs
What are lymph nodes?
Principle lymphoid organs of the body
Where are lymph nodes found?
Embedded in connective tissue and in clusters along lymphatic vessels
What body surfaces can you find lymph nodes?
Axillary, Cervical, Inguinal
What are the 2 main functions of lymph nodes?
Filter lymph - macrophages destroy microrganisms and debris
Immune System - activate lymphocytes and attack antigens
What is the structure of a lymph node?
Bean shaped
external fibrous capsule
Trabeculae extending inward, dividing into compartments
2 Distinct Regions of Lymph Nodes
Cortex and Medullary Cords
What does the cortex of a lymph node contain?
Follicles with germinal center
dividing b cells
deeper cortex holds t cells in transit
Where are t cells continuously circulating?
Blood, lymph nodes, lymphatic stream
Where are the medullary cords?
Extend inward from the cortex
What do medullary cords contain?
b cells, t cells, plasma cells
What do the lymph sinuses in the medulla contain?
macrophages
How does fluid move through a lymphnode?
- Fluid enters convex side via afferent vessels
- Fluid travels through subscapsular sinus
- Fluid moves to smaller sinuses
- Exits at concave side called hilus via efferent vessels
Why are there fewer vessels leaving than entering?
Causes slowing of the fluid to give lymphocytes and macrophages plenty of time for access to the fluid to carry out their surveillance and clean up functions
What are the lyphoid organs
Spleen Thymus Tonsils Peyer's Patches Appendix Bone marrow Lymph nodes
What is the largest lymphoid organ?
Spleen
What vessels serve the spleen? Where do they enter and exit?
Splenic artery and vein, which enter and exit via the hilus
What are the functions of the spleen?
Site of lymphosite proliferation Site of immune surveilance and response Cleanses blood Stores the breakdown products of RBCs (iron) for later use Stores platelets
What does the spleen cleanse blood of?
Aged cells, platelets, debris
In the fetus, what is the spleen the site of?
erythrocyte/rbc production
What does the spleen contain?
lymphocytes
macrophages
very large numbers of erythrocytes
What are the 2 main areas of the spleen?
White Pulp
Red Pulp
What is the white pulp?
Clustered around central arteries
Contains mostly lymphocytes sitting on reticular fibers
important in immune functions
Where is red pulp found?
Found in blood filled venous sinuses and in splenic cords
What is the primary cell of red pulp? What is their function?
Macrophages whose job is disposal of RBC’s and bloodborne pathogens
What is the thymus made up of?
Outer cortex and inner medulla
What does the cortex of the thymus contain?
Densely packed lymphocytes and a few scattered macrophages
What does the medulla of the thymus contain?
Fewer lymphocytes
What is the role of thymic corpuscles?
Regulation of t cell development
What is the function of the thymus?
T cell maturation, does not directly fight antigens
What are the cells of the thymus called? What is their role?
Thymocytes, they provide optimal environment for t cells to become immunocompetent
Describe the tonils
simpest lymphoid organ
contain follicles and germinal centers
not fully encapsulated
How are tonsillar crypts formed?
Outer epithelial tissue invaginates (folds inward)
What is the role of a tonsillar crypt?
trap and destroy bacteria and particulate matter
What are Peyer’s Patches?
Clusters of lymphoid follicles
found in the wall of distal portions of the small intestine
What is the function of peyer’s patches?
destroy bacteria to prevent their movement across the intestinal wall
Generate memory lymphocytes
What does the appendix have concentrated in it’s walls?
lymphoid follicles
what is the role of the appendix?
Same as Peyer’s Patches, Destruction of bacteria and generation of memory lymphocytes
What is MALT
mucosa associated lymphatic tissue
What are types of MALT?
Peyer’s Patches
tonsils
appendix
lymphoid nodules in wall of bronchi
What is the function of MALT?
Protection of passage ways that are open to outside world
Name 4 homeostatic imbalances of the lymphatic system
Lymphedema
Buboes
Elephantiasis
Hodgkin’s Disease
What is lymphedema
Prevention of normal return of lymph to the blood, causes sever localized edema
What are Buboes
NOT swollen glands, but infected lymph nodes, main symptom of bubonic plague
What is elephantiasis
Tropical disease where lymphatics of lower limbs become clogged with a parasitic round worm
What is Hodgkin’s Disease? How is it treated?
Malignancy of lymphoid tissues
Treated with chemo and radiation
What are the symptoms of Hodgkin’s Disease
Swollen lymphnodes
fatigue
intermittent fevers
night sweats
Which is the smallest lymphatic vessel?
lymphatic capillaries
