Flashcards in Lymphatics&Spleen_BTED Deck (53):
What is the largest lymphatic organ?
Where is the spleen located?
Upper left quadrant of the abdominal cavity and has a rich blood supply
What are the functions of the spleen?
1) Formation of blood cells
2)Destruction of blood cell
3) Reservoir function
4) Role of defence in body
5) Removal of iron
What role does the spleen play in formation of blood cells?
1) Play important role in haematopoietic function
- storage of haematopoietic stem cells in foetus
2) During hepatic stage, spleen produces blood cells along with liver
What role does spleen play in destruction of blood cells?
Older RBC, lymphocytes and thrombocytes are destroyed in spleen
What role does spleen play in reservoir function?
1) Large number of RBC stored in spleen
2) RBC are released from spleen into circulation during emergency condition like hypoxia and haemorrhage
3) Storage of platelets and granulocytes
What role does spleen play in defence in body?
1) Spleen filters blood by removing microorganism
2) Macrophage in splenic pulp phagocytes the microorganism & other foreign bodies
3) Spleen contains about 25% of T lymphocytes and 15% of B lymphocytes and site of antibody production
What does the spleen contain?
1) Large number of lymphocytes
2) Specialised vascular spaces or channel
3) Meshwork of reticular cells and reticular fibres
4) Rich supply of macrophage and dendritic cell
What is the spleen enclosed by?
Dense CT capsule from which trabecular extend into the parenchyma of organ.
What does the capsule connective tissue and trabeculae of spleen contain?
What does contraction in the capsule and trabecular do?
Help discharge stored RBC into the systemic circulation
Where is the hilum located?
Medial surface of the spleen
What is the hilum for?
Site for the passage of the splenic artery and vein, nerves and lymphatic vessels.
Where does the lymphatic vessels in the spleen originate?
In the white pulp near the trabecular and constitute a route for lymphocytes leaving the spleen
What is most of the spleen consisted of?
What is splenic pulp divided into?
1) White pulp
2) Red pulp
What is the difference histologically between white pulp and red pulp?
White pulp appears as circular or elongated whitish gray areas surrounded by red pulp
- white pulp appears basophilic
What does the white pulp consist of?
Lymphatic tissue, mostly lymphocytes. (T cells and B cells)
Why does white pulp appear basophilic under H&E staining
Dense heterochromatin in the nuclei of the numerous lymphocytes
What enters the white pulp?
Branches of the splenic artery course through the capsule and trabecular of the spleen and enters white pulp
Within the white pulp, what is the branch of splenic artery called?
Lymphocytes that aggregate around the central artery constitute the...?
Periarterial lymphatic sheath
What is the periarterial lymphatic sheath?
Rough cylindrical configuration that conforms to the course of the central artery
In cross section, what does PALS appear like?
Circular and may resemble a lymphatic nodule but the presence of central artery distinguishes PALS
Why does the central artery occupy an eccentric position?
Nodules appears as localised expansions of the PALS and displace the central artery
Which lymphocyte is found where?
Nodule: mainly B lymphocytes
PALS: mainly T lymphocytes that surround nodule
What does the nodule usually contain?
Germinal center, which develop as B cells proliferate after their activation
What are splenic nodules?
When germinal centers develop after antigen exposure and may become extremely large and visible with the naked eye. Enlarge nodules
What does red pulp look like in histological sections?
Red appearance because of the large number of RBC
What does the red pulp consist of?
Splenic venous sinuses separated by splenic cords
Cords of Billroth/splenic cords
What does splenic cords consist of?
Meshwork of reticular cells and reticular fibres that contain large number of erythrocytes, macrophage, lymphocytes, dendritic cells, plasma cells and granulocytes
- contains lots of macrophage and monocytes
What does splenic macrophage do?
Begin the process of haemoglobin breakdown and iron reclamation.
What are the percentage of B and T lymphocytes in Thymus
T lymphocytes: 100%
B lymphocytes: 0%
What are the percentage of B and T lymphocytes in bone marrow
T lymphocytes: 10%
B lymphocytes: 90%
What are the percentage of B and T lymphocytes in Spleen?
T lymphocytes: 45%
B lymphocytes: 55%
What are the percentage of B and T lymphocytes in lymph nodes
T lymphocytes: 60%
B lymphocytes: 40%
What are the percentage of B and T lymphocytes in blood
T lymphocytes: 70%
B lymphocytes: 30%
What is the splenic or venous sinuses lined by?
Rod shaped endothelial cells
What is the results of splenectomy?
- Peripheral blood film changes
- Overwhelming sepsis with Streptococcus, Meisseria, Haemophilus (avoid splenectomy until after 6 years)
- Platelets rise in 7 days
What is splenectomy
surgical procedure that partially or completely removes the spleen
What is open circulation?
The central artery sends branches to the white pulp itself and to the sinuses at the perimeter of the white pulp called marginal sinuses.
The central artery continues into the red pulp, where it branches into several relatively straight arterioles called penicillar arterioles.
The penicillar arterioles then continue as arterial capillaries. Some arterial capillaries are surrounded by aggregations of macrophages and are thus called sheathed capillaries. Sheathed capillaries then empty directly into the reticular meshwork of the splenic cords rather than connecting to the endothelium-lined splenic sinuses.
Blood entering the red pulp in this manner percolates through the cords and is exposed to the macrophages of the cords before returning to the circulation by squeezing through the walls of the splenic sinuses
What is closed circulation that takes place in dogs and rats?
some of the blood from the sheathed capillaries passes directly to the splenic sinuses of the red pulp
What happens in the lymphatic system?
Lymph is entered in the bloodstream of subclavian vein
What is at the lymph vessels?
Squeezed by smooth muscles (circular)
Nitric oxide: Vasodilation (relaxation of circular smooth muscle) -> neurotransmitter of parasympathetic automatic system
What happens at the lymph vessel when there is an increase of NO and decrease of NO
NO increase: Dilation
NO decrease: contraction
What are the clinical concerns regarding the lymphatic system?
4) Lymphatic filariasis (elephantiasis)
What is lymphangitis?
Inflammation of lymphatic vessels
What is the common cause of lymphangitis?
What is lymphadenopathy?
Abnormal size of lymph nodes
What are the two subdivision of lymphadenopathy?
1) Scrofula (cervical TB)
2) Buboes (axillary or inguinal)
What causes lymphedema?
4) Infection: parasite
5) genetic: Milroy disease: associated with a vascular endothelial growth factor
What causes lymphatic filariasis (elephantiasis)