Splenic circulation : lecture note

Splenic circulation:

1.      Splenic artery entering at the hilum of the spleen

2.      Via trabeculae the trabecular artery inter the spleen

3.      Then leave the trabeculae enter into the parenchyma,& surrounded by  periarterial

       lymphatic sheath, occasional lymphatic nodules, now  it is called central artery

4.        The central artery enter the red pulp by losing the lymphatic sheath &  subdivided into Numerous straight vessels, known as penicillar arteries

5.      The penicillar artery terminate into 2 to 3 sheath capillaries, than formed terminal  arterial capillaries (TAC)

6.      TAC directly drain into sinusoids (closed circulation)

                                           Or

7.      TAC terminate as  open ended vessels in the splenic cords ( open circulation)

Primary lymphatic nodule: the lymphatic nodule which do not contain germinal centre

Secondary lymphatic nodule: the lymphatic nodule which contains germinal centre

 

Closed circulation:

Splenic artery →the trabecular artery →central artery →penicillar arteries→ terminal  arterial capillaries (TAC) →splenic sinusoids →splenic vein

Open circulation:

Splenic artery →the trabecular artery →central artery →penicillar arteries→terminal  arterial capillaries (TAC) →red pulp →splenic sinusoids →splenic vein

Anatomy o f Lymph node: lecture note

Anatomy o f Lymph node: lecture note

 

Lymph nodes are small encapsulated organs located along the pathway of lymphatic vessels   

Diameter: 1mm to 2 cm

Two types of lymphatic vessels are connected with lymph node: they are - the afferent and efferent lymph vessels

Afferent lymph vessels: convey lymph toward the L. node and penetrate the capsule at multiple sites

Efferent lymph vessels: convey lymph away from the lymph node and leave at the hilum. It is one in number.

Functions of lymph node:

1. Filter the lymph 2.Produce lymphocytes 3. Initiation of immune responses 4.phagocytosis

3. Histological features of Lymph node:

1. capsule is present
2. sub-capsular sinus is present
3. Outer cortex contains lymphatic nodules. Superficial part of cortex contain B lymphocytes and deeper zone of cortex contain T lymphocyte
4. inner medulla  contain medullary cord which composed of B lymphocyte and plasma cells  

5. What is lymph?

Ans: Tissue fluid, when enters into the lymphatic system is known as lymph

Lymph contains macromolecules of proteins and large particles – dust, carbon, bacteria, cancer cells etc. 

What is trabeculea? Ans: they are the part of capsule which enter in to the organ

What do you mean by sinuses of lymph node? Ans: these are empty spaces within a lymph node where lymph flows.

6. Lymph circulation: lymph enters into lymph capillaries then through afferent lymphatic vessels enters into subscapsular sinus of lymph nodes then trabecular sinuses of lymph node then medullary sinuses of lymph node then through efferent lymph vessel the lymph leave the lymph node and drain into the venous system

7. Cells present within the lymph nodes: T & B lymphocyte, dendritic cells, macrophages

 8. What is lymphatic nodule?

Ans: small collection of lymphocytes found in mucosa of different organs like ileum, appendix, bronchus etc.

Types of lymphatic nodule: primary and secondary lymphatic nodules

When a germinal center appears in a lymphatic nodule the lymphatic nodule known as secondary L nodule

9. What is germinal center: it is the site of lymphocyte production mainly B lymphocyte. It is a pale

Staining area situated within a lymphatic nodule contain immature lymphoblast. It is found in secondary lymphatic nodule.

 

Thymic or Hassall’s corpuscles

Thymic or Hassall’s corpuscles

•          Are distinguishing feature of thymic medulla. It is formed by epithelioreticular cells

•          The epithelioreticular cells are concentrically arranged and cytoplasm of the cells contain keratohyalin granules, lipid droplet and intermediate filaments

 

Blood thymic barrier

 

Blood thymic barrier

• Lining endothelium of the capillary  wall
•  Basal lamina of endothelial cells
•  Macrophages in the surrounding  perivascular connective tissue
•  Basal lamina of epithelioreticular    cells
•  Epithelioreticular cells

Important of blood thymic barrier: Prevent entering of antigen into the thymic cortex