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