Secondary Lymphoid Tissue Flashcards
Where are secondary lymphoid tissues found?
They are found in sites where mature lymphocytes are exposed to and stimulated by antigen
What are secondary lymphoid tissues also known as?
They are known as peripheral lymphoid organs
What are tissues involved in the secondary lymphoid tissues?
Lymph vessels, lymph nodes, spleen and mucosa associated lymphoid tissue (MALT)
What is the lymphoid migration like to the secondary lymphoid tissues?
It is highly specific
What do the lymphoids enter?
They enter via high endothelial venues which express specific adhesion molecules on their endothelium to which lymphocytes bind
What does adhesion lead to?
Adhesion leads to the lymphocyte sweeping through the endothelium into the node
What do lymph vessels do?
They drain tissue fluid from the connective tissue
Where do the lymph vessels empty?
They empty primarily via the thoracic duct to the left venous angle between the interior jugular vein and subclavian vein
Describe the thoracic duct
It is 45cm long, it has several branches and drains all lymph in the left head/neck and left thorax
Where does the thoracic duct start?
At T12 and ascends behind the right crus to right of the aorta and oesophagus, then crosses the midline of T5
Where does the thoracic duct lie?
Lies superficial to posterior intercostal arteries, crosses the azygos systems, to the left vertebral and left subclavian arteries
What is the flow like in valves?
Unidirectional
What is carried to lymph nodes?
Antigen from pathogens and other foreign materials is drained from the site of infection and then carried to the lymph nodes
Describe lymph nodes
They are highly organised, bean shaped structures at junctions between lymph vessels
What are the lymph nodes aggregated (together)?
Neck and groins
What is the function of the lymph nodes?
To filter lymph from tissues
What is trapped in the lymph nodes?
Antigens and then they are taken up by antigen presenting cells which is then presented to lymphocytes passing through the node
What do Afferent lymphatics do?
They enter the node in the cortex and then pass through the parachuted and exit via the efferent lymphatics in the medulla
Where do high endothelial venues enter in the lymph node?
In the paracortex
Where are B cells and T cells located in the cortex?
They are located in the primary and secondary follicles in the Cortex
What are primary follicles?they contain B cells and are the site at which germinal centres form which then form secondary follicles
Where do lymphocytes enter the node?
They enter the High endothelial venues at which point they are then exposed to antigens
What happens if the B cell when entering the HEVs do not detect an antigen?
Then it leaves via the efferent lymph node and later returns to the blood via the thoracic duct
Describe the spleen
It is a fist-sized organ, associated posteriorly with the left ribs 9 and 11, though separated from them by the diaphragm superiorly
Where does the spleen rest?
On the left colic flexure of the large intestine. The tail of the pancreas points towards the spleen. It sits on the left side of the abdomen within the hypochondrium region
What does the spleen collect?
It collects antigens from the blood, presenting it to lymphocytes
What is the function of the spleen?
It serves to filter the blood, removing and disposing of ageing red blood cells and immune complexes
What are the two distinct components of the spleen?
Red pulp and white pulp
What is red pulp?
Is a well perfused-tissue responsive for the filtration role of spleen, removing ageing and damaged red blood cells from circulation
What does white pulp do?
Has many similarities to a lymph node. It is packed with T cells, B cells and dendritic cells and sifts antigens from the blood instead of the lymph
Where are T cells located in the spleen?
In the periarteriolar lymphoid sheath (PALS)
Where are B cells located in the spleen?
Beyond the sheath in a corona around a germinal centre
