lymphatic system Flashcards
A group of cells, tissues, and organs that monitor body surfaces and internal fluid and reactants to potentially harmful substances
lymphatic system
- also known as lymphoid system
[example:
body surfaces - skin, mucous membrane
internal fluid - lymph, blood plasma
reactants - antibodies, wbc]
what is included in the lymphoid system
consist of a huge networks of
lymph nodes
lymphatic vessels
lymphatic/ lymphoid organs
lymphoid tissue cells
what are the organs and tissues that are part of the immune system
tonsil and adenoids
thymus
spleen
Peyer’s patches
lymph nodes
bone marrow
appendix
what are the functions of the lymphatic system
1.monitor body surfaces and fluid compartments [spacesbetween cells] (epidermis, mucosae, and interstitium)
[to see if have harmful substances]
2.immune defense: reacts to the presence of potentially harmful antigen as “non-self”
[fights harmful antigens (harmful germs) that enter the body]
- autoimmune disease response
leads to
- rheumatoid arthritis
- type I diabetes - transport large molecules such as - proteins
- hormones
- waste products
(maintain fluid balance, immune defense and liquid absorption)
what type of molecules does lymphatic system transport
large molecules such as
- proteins
- hormones
- waste products
A cell that helps in immune response
WBCs especially the lymphocytes
- helps the body’s immune system to fight against cancer, foreign virus and bacteria
What are the components of the lymphatic system
[made up of diff parts that work tgt to protect the body]
CELLS
Lymphocytes
APC, antigen-presenting cells
- dendritic cells
- Langerhans cells
- macrophages
LYMPHATIC TISSUE
Diffuse tissue
Nodular tissue
LYMPHATIC ORGANS
Lymph nodes
Spleen
Thymus
LYMPHATIC VESSELS
Carry the cell and fluid
it is known as the encapsulated bundles of lymphatic cells
diffuse tissue
- consist of lymphocytes and macrophages
[loosely packed w/o outer covering]
nodular tissue is commonly called as
MALT - Mucosa-Associated Lymphatic Tissue
[found in the intestines, lung and other mucosa areas to detect and fight infections]
classification of lymphatic system
Primary Lymphoid Organs:
➔ Responsible for the creation of special immune cells (Lymphocytes)
○ Thymus
○ Bone Marrow
○ Lymphatic nodules of the distal intestinal tract
Secondary Lymphoid Organs/ Tissue:
○ Spleen and Lymph nodes
○ Mucosa Associated Lymphoid Tissue (MALT)
[Primary organs = Create and train immune cells
Secondary organs = Store and activate immune cells to fight infections]
primary lymphoid organs
bone marrow, thymus, peyer’s patches
- these are the initial ‘education center’
thymus > T cells
bone marrow and gut > B cells
- lymphocytes will differentiate into immunocompetent cells
[able to recognize diff btwn self and non-self]
*this differentiation is said to be antigen-independent
[immune cells mature and get ready for action on their own]
It is the site where lymphocytes become mature and immunocompetent
pri lymphoid organs
site of T lymphocytes maturation and production
thymus
site where T and B lymphocytes develop from stem cells in red bone marrow
bone marrow
how does T cells and B cells developed
T CELLS
- T cells developed in bone marrow (not yet fully developed)
- travel to the thymus whr they will remain until they become functional cells (bcms fully functional immune cells)
- once it becomes fully immunocompetent, it will leave thymus and migrate to the lymphatic organs and tissues (lymph nodes, spleen and tonsils)
B CELLS
- unlike t-cells it will remain in bonne marrow until they are fully matured and functional
- after maturation, move to the lymphatic organs and tissues (particularly, lymph nodes in the BM and mucous membrane)
two types of T cells
Helper T cells:
- bind with specific antigens presented by the macrophages
Killer T cells:
- kill viruses that invaded the body cells and the cancerous body cells
what do B cells produce
palsma cells
- secrete antibodies
this is where immunocompetent lymphocytes differentiate into immune effectors and memory
secondary lymphoid organs
- aka peripheral lymphoid tissue
these lymphocytes carry out functions in
- CT
- sec lymphoid organs
- mucosal surface lining epithelia
- also participate in cell mediated immunity (mostly cytotoxic T cells)
- humoral responses (production of antibodies)
[B and T cells move to the secondary lymphoid organs to become fully active and start fighting infections
- immune effectors: fighters
- memory cells: rmbr past infection]
location of the peyer’s patches
wall of the small intestine
function of the peyer’s patches
macrophages of Peyer’s patches are in an ideal position to capture and destroy bacteria (always present in tremendous amt)
= prevent from penetrating the intestinal wall
Peyer’s Patches also known as
Aggregated Lymphatic Follicles
- covered by a specialized epithelium: follicle-associated epithelium (FAE) which differs from typical intestinal epithelium
what is peyer’s patched epithelium
covered by a specialized epithelium known as the follicle-associated
epithelium (FAE):
modified simple columnar
- lacks of typical villi
- fewer goblet cells (reduce mucous production)
- rich in M cells (Microfold cells)
- has erythrocytes
A secondary lymphoid structure where most immune cells (lymphocytes) get activated
MALT, mucosa-associated lymphoid tissue
- lymphocytes are activated by antigen presentation
Also includes: lymph nodes and spleen
this is one of the largest lymphoid organs, containing up to ___% of all the body’s immune cells
MALT, 70%
- most of the lymphocytes are B cells, among T cells, CD4+ Helper T cells predominates
function of the MALT
aguments (enhance)
- the mechanical (physical structure) and chemical (substance) barriers of surface mucosal epithelia
distribution of MALT
[location of MALT]
1. pharynx
- tonsils (palatine, lingual and pharyngeal)
2. small intestine
- aggregated lymphoid modules (peyer’s patches)
3. colon
- aggregate lymphoid nodules
4. tonsil
5. BALT, bronchus-associated lymph
6. GALT, gut-associated lymph tissue
where is thymus located
- a bilobed organ
- superior mediastinum (above the heart, behind the sternum).
cells present in the thymus gland
- lymphocytes
- T cells - epithelial reticular cells
it has a vascularized connective tissue capsule that extends septa into the parenchyma, dividing the organ into many
incompletely separate lobules
thymus
- vascularized connective tissue capsule (rich in blood vessels)
- divided into lobules by connective tissue (not completely separated)
* receive O2, nutrients and even immune cells
* heal relatively quickly
[each lobule has:
Cortex (outer dark-staining layer) – Contains immature T cells.
Medulla (inner lighter-staining layer) – Contains more mature T cells.
* outer darkly basophilic cortex surrounds a more lightly stained medulla]
function of thymus gland
Production of immunocompetent T
lymphocytes
Production of mature T cells for peripheral tissues and circulation
Regulations of T cell maturation, proliferation, and function via secretion of hormones
[thymus produces hormones that help T cells grow, multiply, and work properly to protect the body]
It is the outer layer of the thymus develop and grow.
Thymic Cortex
- contains many:
T lymphoblasts (young T cells)
along with macrophages
thymic epithelial cells (TECs) - that have certain features of both epithelial and reticular cells
*that help in their development
what are the 3 major types of TECs
● Squamous Thymic Epithelial Cells
○ Important in the formation of the thymus blood barrier
● Stellate Thymic Epithelial Cells
○ Forms the cytoreticulum
● Other Squamous Thymic Epithelial Cells
○ Form the corticomedullary barrier
structure of the thymic cortex
Outer cortical zone: Densely packed with developing T lymphocytes (and associated support cells)
Inner medullary zone: Loosely packed with more mature T cells
- where the resident cells have greater amt of cytoplasm, so the dark staining nuclei are farther apart
Special swirled cell structures found within the medulla of the thymus.
Hassall’s corpuscles
- derived from thymine reticular cells
largest lymphatic organ
spleen
- usually measured 12cm or 5 inches
where is the spleen located
left side of the abdominal cavity, just beneath the diaphragm
and curls around the anterior aspect of the stomach
spleen is surrounded by?
by a capsule of dense CT from which emerge trabeculae to penetrate the parenchyma or splenic pulp
what are the 2 main regions inside the spleen
White Pulp
– contains compact muscle of lymphocytes
Red Pulp
– contains a network of erythrocyte-filled sinuses and the phagocytic cells
functions of the spleen
- remove abnormal blood cells and particulate matter via phagocytosis (spleen filters blood, macrophage in spleen will remove bacteria and other pathogens including cellular debris and aged blood cells)
- storage of iron from recycles RBC
- reservoir of blood
- destroys old RBCs and recycles their parts
○ iIt removes the iron from the heme group of the RBC and bonds the iron to the storage proteins - initiation of the immune response byy B cells and T cells in response to antigen circulating in the blood
- spleen is active in immune responses
○ T cells proliferate in the white pulp before returning to the blood to attack the non-self cells when necessary - Hematopoiesis in fetus and sometimes adult
- spleen produces or remove blood cells
○ RBC and WBC that are produced in the spleen during fetal development - spleen provides a reservoir of blood, ⅓ of the blood platelets are stored in the spleen
How does the spleen help in removing old or damaged blood cells?
macrophages in the spleen break down and remove old RBCs, pathogens, and debris from circulation.
role of the spleen in iron storage
stores iron by recycling it from old red blood cells and binding it to storage proteins.
Two Components of Splenic Pulp
● White Splenic Pulp
○ Consists of lymphoid
nodules and periarteriolar lymphoid
sheath (PALS)
○ Site of immune reaction to blood-borne pathogens
● Red Splenic Pulp
○ Consists of blood-filled sinusoids and splenic cord
○ Responsible for filtering blood foreign materials and old or damaged RBCs
[red pulp: removes aged RBCs and acts as a blood reservoir.
white pulp: contains B & T cells that help fight infections.]
How does the spleen act as a platelet reservoir?
spleen stores about 1/3 of the body’s platelets, which can be released when needed
what are the parts of the spleen
● Capsule
- dense CT enclosing organ
a. trabecula
● White pulp
- composed of ymphatic tissue
- appears basophilic sue to the large no. of nuclei
a. splenic nodules
b. central arterioles
c. PALS (periarteriolar lymphatic sheath)
● Red Pulp
- filters and degrades RBC
- appears eosinophilic due to the large no. of RBCs
● Marginalized Zone
- region between white and red pilp where macrophages, dendritic cells and lymphocytes interact
substance or structure or tissue component that stains dark blue or purple with the basic or alkaline dyes such as Hematoxylin.
Basophilic
- This staining occurs because the
basophilic structures are rich in negatively charged molecules
CT that extends inward from the
capsule through which blood vessels enter the pulp
Trabecula
clusters of B lymphocytes located on central arterioles. They usually contain a germinal center of activated B lymphocytes
Splenic Nodules
branches of trabecular arteries coated by PALS and adjacent to nodules
Central Arterioles
cylindrical mass of mature T lymphocytes that surrounds central
arterioles
PALS (Periarteriolar Lymphatic Sheath)
region between white and red pulp
where macrophages, dendritic cells, and lymphocytes interact
marginalized zone
a dense CT enclosing the spleen
capsule
Large, irregular masses of lymphoid tissue that ring the pharynx (the throat), where they are found in the mucosa
tonsil
- clusters of lymphatic tissue in the throat
- function: trap and remove any bacteria or other foreign pathoges entering the throat
where are the tonsils located
in the mucosa around the pharynx
Chronic inflammation of the pharyngeal lymphoid tissue and tonsils of children often produces hyperplasia and enlargement of the tonsils to form “adenoids”, which can obstruct the eustachian tube and lead to middle ear infections
tonsilitis
- more common in children than adults
- adenoids: Chronically swollen tonsils in children can grow larger (hyperplasia) and become “adenoids”.
what is the complication of tonsilitis
Adenoids can block the eustachian tube (connects throat to ear), causing ear infections.
- adenoids: Chronically swollen tonsils in children can grow larger (hyperplasia) and become “adenoids”.
part of tonsil
● Palatine Tonsils
- posteriorly on the soft palate
- covered by stratified squamous epithelium
- has 10-20 deep crypts (folds) to trap germs.
● Lingual Tonsils
-base of the tongue
- covered by stratified squamous epithelium w crypts
- lack distinct capsules
● Pharyngeal Tonsils
- situated in the posterior wall of the nasopharynx
- covered by pseudostratified ciliated columnar epithelium
- has thin underlying capsule
The surface area of each is enlarged with 10-20 deep invaginations or tonsillar crypts in which the epithelial lining is densely infiltrated with lymphocytes and other leukocytes
palatine tonsils
what are the parts of the palatine tonsil
● Stratified Squamous Non-Keratinized Epithelium
○ Covers the numerous nodules that comprise the palatine tonsil
● Nodules
○ Spherical aggregations of lymphocytes that usually have geminal centers
● Crypts
○ Infoldings of the epithelium into the underlying CT
● Plasma Cells
○ Large numbers of plasma cells are usually seen in the underlying CT near the epithelium
shape of the lymph nodes
tiny oval-shaped structures
location of lymph nodes and what is it covered by
located: superior mediastinum
covered: capsule of fibrous connective tissue
*Bilobed organ
true or false:
lymph nodes produces lymphocytes
true
it filters potentially harmful particles from the lymph
lymph nodes
what are the 3 functional but not physically separate compartments in the lymph nodes
the outer cortex
the underlying paracortex
the inner medulla adjacent to the hilum and the efferent lymphatic
What happens when lymphatics enter the cortex of a lymph node?
🔹 B cells in the cortex encounter antigens (foreign invaders).
🔹 They proliferate (multiply) in lymphoid nodules.
🔹 Activated B cells then move deeper into the lymph node for further immune response.
function of the lymph nodes
● They filter the lymph, preventing the spread of microorganisms and toxins that enter the interstitial
fluids
● They destroy bacteria, toxins, and particulate matter through the phagocytic action of macrophages
● They produce antibodies through the activity of B cells
parts of the lymph nodes
● Capsule
- dense CT enclosing the node
a. Subcapsular Sinus
b. Trabecula
- CT that extends inwards from the capsule
c. Trabecular Sinuses
● Cortex
- outer region of the node
a. Outer Cortex
- nodules
b. Inner Cortex (paracortex)
● Medulla
- inner part of the node
a. Medullary Cords
- contain antibody-secreting
plasma cells, macrophages, and B lymphocytes
b. Medullary Sinuses
- intervening spaces in which lymph flows before exiting the node via efferent lymphatic vessels
space underneath the capsule that receives lymph from different
lymphatic vessels
Subcapsular Sinus
Spaces alongside trabeculae in which lymph flows from the subcapsular sinus into the cortex
Trabecular Sinuses
spherical clusters of B lymphocytes. The lighter center is the germinal center where B lymphocytes differentiate into plasma cells
Nodules
region between the outer cortex and the medulla that is free of nodules
Inner Cortex (paracortex)
inflammation of the lymph nodes
Lymphadenitis
Inflammation of the tonsils
Tonsillitis
Swelling of the tissue due to an abnormal collection of lymph
Lymphedema
disease caused by the Epstein-Barr Virus
Infectious monouceosis
Cancer of lymphocytes where lymphocytes change and grow out of control, and often begins in the lymph nodes
Lymphoma
Two types:
■ Hodgkin’s Lymphoma
■ Non-Hodgkin’s Lymphoma
important histologic comparison of the major lymphoid organs
transes
Secondary lymphoid organs is also known as
Peripheral lymphoid tissue
these are the ‘educational center’ of the immune system
bone marrow
thymus
peyer’s patches
- they’re the pri lymphoid organs
