Lymphatic System, Chapter 20
Where are lymph nodes located?
found along the lymph vessels and clustered in inguinal, axillary, and cervical regions
Diffuse Lymphoid Tissue
found in all body tissues
Tonsils
have crypts that trap antigens that can enter the epithelial covering to evoke an immune response
Collecting lymphatic vessels
have the same tunics as veins, but the collecting vessels have thinner walls and more internal valves
White pulp (Spleen)
immune functions-WBCs monitor blood
Does the spleen regenerate?
it can regenerate in children. You can also live without your spleen
What happens to the Thymus as we get older?
it shrinks
Peyer's Patches (aggregated lymphoid nodules)
large collections of lymphoid tissue found in the submucosa of the small intestine
Lymph sinuses
large lymph capillaries spanned by crisscrossing reticular fibers
Which side of the body drains more lymph?
left
Lymphoid (lymphatic) Tissue-composition
made of loose connective tissue occupied with macrophages
T Cells (T Lymphocytes)
manage the immune response, and some of them directly attack and destroy infected cells
Location of Peyer's Patches
mesentary
MALT
mucosa-associated lymphoid tissues
Red pulp (Spleen)
old RBCs
Macrophages
play a crucial role in body protection and the immune response by phagocytizing foreign substances and by helping to activate T cells -->"highly phagocytic"
Germinal centers
primary locations where B lymphocytes reproduce and proliferate
Structure of Lymphatic Vessels
*same 3 tunics as blood veins with more valves. *vessels unite to form trunks (lumbar, bronchomediastinal, subclavian, jugular, and intestinal trunks) *trunks unite to form ducts (right and thoracic ducts) which then dump the lymph into the R and L subclavian veins
Spleen
-blood filled with WBCs for immunity, ~stores iron and platelets~ -left side of body, under diaphragm >blood filter, old RBCs get picked up
Pharyngeal tonsil
-in the posterior wall of nasopharynx -referred to as adenoids if enlarged
9. Collections of lymphoid tissue (MALT) that guard mucosal surfaces include all of the following, and does not include
-includes: appendix follicles, tonsils, peyer's patches -doesn't include: the thymus
Why is lymphoid tissue important in the immune system?
-it houses and provides a proliferation site for lymphocytes -it furnishes an ideal surveillance vantage point for lymphocytes and macrophages
Palatine tonsils
-located on either side at the posterior end of the oral cavity -largest tonsils -most easily infected
The major lymphatic trunks include
-lumbar -bronchomediastinal -subclavian -jugular -intestinal trunk
3. Entry of lymph into the lymphatic capillaries is promoted by
-one way mini valves formed by overlapping endothelial cells -greater fluid pressure in the interstitial space
Tonsillar Crypts
-trap and destroy bacteria and particulate matter -allow immune cells to build memory for pathogens
12. Which anatomical characteristic ensures that the flow of lymph through a lymph node is slow? Why is this desirable?
.-the fact that there are fewer efferent vessels draining the node than afferent vessels feeding it. -This feature is desirable to allow time for the lymphocytes and macrophages to perform their protective functions
What are the 2 types of lymphoid tissue?
1. Diffuse lymphoid tissue 2. Lymphoid follicles
What are the two main functions of Lymph nodes?
1. Filtration 2. Immune system activation
Aggregates of Lymphoid Follicles
1. peyer's patches 2. appendix
Lymphocytes consist of
B and T cells
Loss of fluid return into lymph results in:
Edema
What is the Thymus made of?
Epithelial tissue
Once interstitial fluid enters the lymphatic vessels it is called
Lymph
13. There are no lymphatic arteries. Why isn't this a problem?
Lymph is generated in the body tissues and only flows back toward the heart, so there is no need for arteries to carry lymph away from the heart.
10. Compare and contrast blood, interstitial fluid and lymph
Lymph is the fluid inside lymphatic vessels. It enters lymphatic vessels from interstitial fluid. Interstitial fluid, in turn, is a filtrate of blood plasma
11. Compare the structure and functions of a lymph nodes to those of the spleen
Lymph nodes are very small structures consisting of a medulla and a cortex, which act as filters to cleanse lymph before it reenters the blood. Each node is surrounded by a dense fibrous capsule from which connective tissue strands called trabeculae extend inward to divide the node into compartments. The stroma is an open network of reticular fibers that physically support lymphocytes and macrophages. The outer cortex contains densely packed spherical collections of lymphocytes called follicles, which frequently have lighter-staining centers called germinal centers. Cordlike extensions of the cortex, called medullary cords, invade the medulla. Macrophages are located throughout the node but are particularly abundant lining the sinuses of the medulla. The spleen is the largest lymphoid organ. It functions to remove aged or defective blood cells, platelets, and pathogens from the blood and to store some of the breakdown products of RBCs or release them to the blood for processing by the liver. The spleen is surrounded by a fibrous capsule, and has trabeculae. It contains lymphocytes, macrophages, and huge numbers of erythrocytes. Venous sinuses and other regions that contain red blood cells and macrophages and process blood are referred to as red pulp, whereas areas composed mostly of lymphocytes suspended on reticular fibers are called white pulp. The white pulp clusters around small branches of the splenic artery within the organ and serves the immune functions of the organ.
Lymphatics
Lymphatic capillaries and vessels
Which is more permeable, blood vessels or lymphatic capillaries?
Lymphatic capillaries are more permeable than blood vessels with mini-valves.
What movement insures the WBCs patrol the body?
Lymphocytes move throughout the tissue as well as blood
What forms a ring around the entrance of the pharynx
Tonsils
2. The sac that often forms the initial portion of the thoracic duct is the
cisterna chyli
Primary lymphoid organs
Where B and T cells mature - the red bone marrow and the thymus
Subcapsular sinus
a large, bag like structure leading into a number of small sinuses
Lymph flow through lymph nodes
afferent vessel, sinus, cortex to medulla, exit at hilum via efferent vessel
Function of Lymphatic Capillaries
allows the excess tissue fluid to move in (3L/day)-~w/protein~
Lymphoid follicles (nodules)
are tightly packed lymph tissue found in peyer's patches and appendix (and nodes too)
Location of Appendix
attached to the small intestine (ileum)
Structure of Lymph Nodes
bean shaped and less than 1 inch with a cortex and medulla & capsule
Why does the thymus have no follicles?
because it lacks B Cells
**Why is lymph flow so slow?**
because there are more afferent vessels than efferent vessels so the WBCs can monitor.
Lymphatic capillaries-Location
begin in tissues throughout the body except for bones, teeth, and CNS
afferent lymphatic vessels
bring lymph to a lymph node
Dendritic cells
capture antigens and bring them back to lymph nodes
Lingual tonsil
collective term for a lumpy collection of lymphoid follicles at the base of the tongue
thymic corpuscles
consisting of concentric whorls of keratinized epithelial cells
medullary sinuses
contain reticular cells + macrophages
Macrophages
destroy unwanted materials
Lymphatic Trunks
drain fairly large areas of the body
right lymphatic duct
drains right upper arm and right side of head and thorax
Lymphatic vessels/Lymphatics
elaborate networks of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream
Chyle
fatty lymph that flows through lacteals
Reticular Cells
fibroblast like cells that produce the reticular fiber stroma
Are lymph nodes organs?
yes
Describe Lymph Transport
lymphatic vessels are usually bundled with blood vessels, which makes them have low pressure, causing slow moving lymph
6. The germinal centers in lymph nodes are largely sites of
proliferation B lymphocytes
B Cells (B Lymphocytes)
protect the body by producing PLASMA CELLS, that secrete antibodies into the blood. Antibodies mark antigens for destruction.
Lymphocytes
protects the body from antigens, B/T Cells
Lymphoid organs and tissues
provides the structural basis of the immune system, plays an essential role in body's defense mechanisms and its resistance to disease, and includes the spleen, thymus, tonsils, lymph nodes and other lymphoid tissues scattered throughout the body.
Thoracic Duct
receives lymph from the left side of the head, neck, chest, abdomen, left arm, and lower extremities (the rest of the body)
splenic cords
regions of reticular connective tissue exceptionally rich in macrophages, that separate the blood filled splenic sinusoids
4. The structural framework of lymphoid organs is
reticular tissue
Lymphatic System
returns fluids that have leaked from the vascular system back to the blood
Cisterna Chyli
serves as a storage area for purified lymph before this lymph returns to the bloodstream
Lacteals
specialized lymphatic capillaries in the digestive system that transport absorbed fat from the small intestine to the blood stream.
7. The red pulp areas of the spleen are sites of
splenic sinusoids , macrophages, and RBCs
Tubal tonsils
surround the openings of the auditory tubes in the pharynx
5. Lymph nodes are densely clustered in all of the following body areas except
the brain
Stroma
the network that supports the other cell types in lymphoid organs and tissues
8. The lymphoid organ that functions primarily during youth and then begins to atrophy is the
thymus
MALT includes
tonsils, peyer's patches, and appendix
Efferent Lymphatic vessels
transport filtered lymph away from the lymph node
1. Lymphatic Vessels
transport leaked plasma proteins and fluids to the cardiovascular system
Appendix
tubular offshoot of the first part of the large intestine and contains a high concentration of lymphoid follicles
splenic sinusoids
venous sinuses
Thymus
where T cells mature, has no B cells, does not fight antigens
Secondary lymphoid organs
where mature lymphocytes first encounter their antigens and are activated-lymph nodes, spleen, collections of MALT that form tonsils, peyer's patches in the intestines and appendix