Lab 2: Lymph Nodes and Organs Flashcards
Name the two general features of lymphoid tissue?
- Aggregates of predominately lymphocytes
- A supporting skeleton usually composed of reticular fibres
Describe the structure of lymphocytes
- Small round cells of size similar to an erythrocyte
- Approx. 7 μm in diameter
Describe the histology of a lymphocyte
They are mostly filled by a dark (heterochromatic) nucleus, indented on one side, with a minimal amount of basophilic cytoplasm.
A Basophil granulocyte stains which colour and by which type of staining?
It was stain dark purple upon H&E (Haemotoxylin and Eosin) stain
T and B lymphocytes are identical morphologically thus name the technique required to distinguish T and B lymphocytes
Special immunological staining techniques (immunocytochemistry) is required to distinguish them.
Describe reticular fibres
They are fine bundles of collagen fibres
Describe the histological features of reticular fibres
Reticular fibres stain black with a silver-based stain.
List the primary lymphoid organs
Bone marrow
Thymus
What is the difference between primary and secondary lymphoid organs
In the primary organs, the lymphocytes are formed and mature.
In secondary, is the place where the lymphocytes will be activated by encountering foreign antigens producing an immune response.
Name the secondary lymphoid organs?
Lymph nodes
Tonsils
Spleen
Mucosa-associated lymphoid tissue (MALT)
List the lymphoid organs
Bone marrow
Thymus
Tonsils
Lymph nodes
Spleen
Mucosa-associated lymphoid tissue
Where are mucosa-associated lymphoid tissue located?
Digestive tract
Respiratory tract
Bone
Peyer patches (small masses of lymphatic tissue found throughout the ileum region of the small intestine)
The early cohorts of T-lymphocytes originate from the ____ and travel to the _____ where they are programmed i.e. become immunocompetent.
The early cohorts of T-lymphocytes originate from the bone marrow and travel to the thymus where they are programmed i.e. become immunocompetent
Early cohorts of T-lymphocytes originate from where?
The bone marrow
Early cohorts of T-lymphocytes are programmed i.e. acquire immunocompetence, where?
In the thymus
Remember: T cell = Thymus
Why is the thymus a unique lymphoid organ?
It does not, itself, take part in immune responses, but the other lymphoid organs – lymph nodes, spleen, tonsil, mucosa-associated lymphoid tissue – are all dependent on it for their T-cell populations and function.
Early cohorts of B-lymphocytes originate from where?
Bone marrow
B cells for Bone marrow
Early cohorts of B-lymphocytes are programmed i.e. acquire immunocompetence, where?
Bone marrow
B cells for Bone marrow
T cells arise from lymphocytes that were carried to and matured where?
In the thymus gland
What stimulates B cells to differentiate into plasma cells and to secrete antibodies?
Cytokines
B cells remain and mature where?
In bone marrow
How does B cells recognise antigens?
Recognise antigens as a result of antigen receptors on cell membranes and become activated.
Response is more intense when antigen-presenting CD4 T cells present antigens to B cells
CD4+ vs CD8+ T cells
CD4+ refers to helper T cells
CD8+ refers to cytotoxic T cells
Which of the lymphoid organ does not fit the definition of a lymphoid organ?
The bone marrow
Why does the bone marrow not fit the definition of a lymphoid organ?
As the lymphocytes are not predominant cell type within the bone marrow.
The lymphocytes are rather masked by all the other blood cell precursors: all the progenitor stages of the erythrocytes, and of the neutrophils, the eosinophils and basophils as well as the megakaryocytes that produce the platelets.
This is a section through which structure?
Lymphoid tissue
Can see the bundle of reticular fibres and aggregates of predominantly lymphocytes
What is more outer in lymph nodes:
Medulla or Cortex?
Cortex
Cortex surrounds the inner medulla
Which structures are located in the medulla of a lymph node?
Medullary cord
Medullary sinus
Name these parts of the lymph node
Name these parts of the lymph node
What is the function of lymph nodes?
They serve as filters of the lymph (excess fluid from intestitial tissue) and drains into the subclavian vein, via the thoracic duct- returning it to the bloodstream
Lymph enters the bloodstream by which vein?
Subclavian vein
The node artery and vein enter and leave the lymph node at which part?
At its hilum
Name these parts of this histological section of the medulla of a lymph node
What is the structure the arrow is pointing at that is located in the medullary sinus in the lymph node
This is debris that is being broken down in the cytoplasm of stellate macrophages
The lymph is drained into the lymph node via what?
The afferent lymphatic vessel
Generally several incoming vessels that have drained lymph from the surrounding regions
NOTE: A for Arrival
The lymph is drained from the lymph node by which vessel?
The efferent lymphatic vessel
Generally a single outcoming vessel.
NOTE: E for Exit
The parenchyma of a lymph node is supported by a delicate framework composed of?
Reticular fibres
Describe the location of the subcapsular sinus?
Lies between the capsule and the cortex
Describe the medullary cords?
Lymphocytes are arranged in irregular cords of lymphocytes.
Contain macrophages, plasma cells and lymphocytes