LYMPHOID SYSTEM and organs with structure.pdf

Various lymphoid organs are covered

1. lymphoid
organs
Delving into our Immune System

2. INDEX
Lymphoid System
1
Thymus
2
Spleen
4
Bone Marrow
3
MALT (Mucosa Associated
lymphoid Tissue)
5

3. LYMPHOID SYSTEM
The Immune system consists of Immune cells that
continuously circulate between the Blood and
Lymphoid organs.
The Lymphatic system consists of Lymphatic organs
and the circulating clear fluid called Lymph.
The Lymphatic system was first described in the seventeenth
century independently by Olaus Rudbeck and Thomas
Bartholin.
Lymphoid organs are classified into 2 types. They are:
(1) Primary Lymphoid Organs
(2) Secondary Lymphoid Organs.

4. PRIMARY & SECONDARY LYMPHOID ORGANS
PRIMARY LYMPHOID
ORGANS
SECONDARY LYMPHOID
ORGANS
Central lymphoid organs.
Primary lymphoid organs are thesiteswhere
Leukocytes (WBCs)aregenerated. It includes:
(i)Bone marrow and (ii) Thymus.
The Lymphoid stem cells proliferate (rapid
increase), differentiate and mature.
Contains either B - cell or T-cell.
Antigens cannot enter in.
Peripheral lymphoid organs.
Secondary lymphoid organs are the sites
where Adaptive immuneresponses (Acquired
immunity)are initiated. It includes: (i)Spleen, (ii)
Lymph Node and (iii)MALT.
The Lymphoid stem cells becomes functional.
Contains both B-cell or T― cell.
Antigens enter in and stimulates the Lymphoid
cells.

5. Thymus

6. Growth and maturation of T lymphocytes takes place in Thymus only.
It is large at the time of birth (70 g) but with age, the size keep on reducing
and becomes very small byattaining puberty (3 g).
It is a flat, bilobed organ situated above the heart. Each Lobe is surrounded
by a Capsule and is divided intoLobules, which are separated from each
other by strands ofConnective tissue called Trabeculae.
Each lobule is organized into 2 compartments: the outercompartment, or
cortex, is densely packed withimmature T cells, called Thymocytes, whereas
theinner compartment, or medulla, is sparsely populatedwith Thymocytes.

7. Both the cortex and medulla of the thymus are crisscrossed (moved travel
around) by a or three -dimensional stromal cell network composed of
Epithelial cells, Dendritic cells and Macrophages, which make up the
framework of the organ and contribute to the growth and maturation of
Thymocytes.
Some thymic epithelial cells in the outer cortex, called Nurse cells, have long
membrane extensions that surround as many as 50 Thymocytes, forming
large multicellular complexes.
Hassall corpuscles are a characteristic morphologic feature located within
the medullary region of the thymus.

8. The main function of the Thymus is to release Thymosin hormone that will
stimulate the maturation of T-cells.
Failure of Thymus development shows dramatic decreasein circulating
Lymphocytes of the T-cell lineage andabsence of cell-mediated immunity.
Aging is accompanied by a decline in Thymic function.
FUNCTIONS OF THYMUS

9. Bone marrow is the soft, flexible connective tissue present within the bone
cavities.
In humans and Mice, bone marrow is the site of B-cell origin and
development.
Bone marrow forms around 4% of total body weight.
There are two categories of bone marrow tissue: Redmarrow and Yellow
marrow. From birth to earlyadolescence, the majority of our bone marrow is
redmarrow. As we grow and mature, increasing amounts of redmarrow is
replaced by yellow marrow.
Bone marrow can generate 200 billions of new blood cells every day.
BONE MARROW

10. Bone marrow is the site of B-cell origin and development.
A bone marrow transplant can save the lives of people battling leukemia,
lymphoma and other blood cancers.
Bone marrow generates Platelets or Thrombocytes help prevent bleeding
and aid in clotting of blood. Granulocytes (Neutrophils, Basophils &
Eosinophils) and Macrophages fight against microbial infections. They also
remove dead cells and remodel tissue and bones.
Bone marrow generates RBCs which carry oxygen to the tissues.
FUNCTIONS OF BONE MARROW

11. Lymph nodes are a group of small, bean-shaped organs (2.6 cm in length)
found mainly in the neck and trunk of the human body.
They play vital roles in the filtration of antigens and debris from Lymph
(circulating colourless watery fluid) and in the generation of immune
responses to pathogens.
Lymph nodes are often removed from cancer patients as their filtration
function catches tumor cells metastasized (spread to other sites in the body)
from primary tumors.
LYMPH NODE

12. Drainage of fluid from blood stream into the tissues.
Filtration of the lymph at the lymph nodes.
Filtering blood.
Raise an immune reaction and fight against microbial infections.
FUNCTIONS OF LYMPH NODE

13. The Spleen is an organ found in virtually all Vertebrates.
The spleen is an organ the Abdominal cavity under muscular partition
between the Abdomen and the Chest.
Similar to a Lymph node, it acts primarily as a blood filter. Old RBCs are
recycled in the Spleen.
Platelets and WBCs are stored in Spleen.
The spleen also helps to fight against certain kinds of bacteria that cause
Pneumonia and Meningitis.
SPLEEN

14. Similar to a Lymph node, Spleen acts primarily as a blood filter.
Old RBCs are recycled in the Spleen.
Platelets and WBCs are stored in Spleen.
The spleen also helps to fight against certain kinds of bacteria that cause
Pneumonia and Meningitis.
FUNCTIONS OF SPLEEN

15. The mucous membranes lining the digestive, respiratory, and urogenital
systems have a combined surface area of about 400 m2 and are the major
sites of entry for most pathogens.
These vulnerable membrane surfaces are defended by a group of organized
lymphoid tissues mentioned earlier and known collectively as Mucosal-
associated lymphoid tissue (MALT).
MALT can be further classified as Gut-associated lymphoid tissue (GALT) or
Bronchus-associated lymphoid tissue (BALT).
The Tonsils, Appendix and Peyer's patches are representative of lymphoid
tissue found in and around mucosal epithelia.
MALT ( Mucosa associated lymphoid tissue )

16. THANK
YOU
~ SHASHANK GAUTAM