Lymphatic System Flashcards
What is the function of the lymphatic system?
elaborate networks of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream
1) Return excess tissue fluid to the blood
2) Return leaked proteins to the blood
3) Carry pathogens to lymph nodes
4) Carry absorbed fat from the intestine to the blood (through lacteals)
What is the structure and distribution of the lymphatic system?
It is a one way system, starting from the (lymphatic capillaries) which are absent in bones & teeth & are remarkably permeable, opening when the fluid pressure in the interstitial fluid is higher than the pressure in the lymphatic capillaries, then to the (collecting lymphatic vessels), then to (lymphatic trunks), then to (lymphatic ducts)
1) lymphatic vessel network
2) lymph
3) lymph nodes which cleanse the lymph as it passes through it
What are the modifications of the lymphatic vessels which makes them highly permeable?
1) their endothelial cells which forms their walls are not tightly joined, but are overlapped forming mini-valves
2) collagen filaments anchors them to surrounding structures, preventing their collapse
What is lacteals?
Lymphatic capillaries which are present in the small intestine which transports absorbed fats from the S.I to the Blood stream they carry a type of milky lymph called chyle
What is the collecting lymphatic vessels?
Having the same three tunics as veins given thinner walls and more valves, unites to form lymphatic trunks
What are the major lymphatic trunks?
1) lumbar
2) bronchomediastinal
3) subclavian
4) jugular
5) intestinal trunk
What are the major lymphatic ducts?
1) right lymphatic duct (drains lymph from the right upper limb, right side of the head & thorax)
2) thoracic duct (drains rest of the body)
What is lymphangitis?
When the vasa vasorum (their blood supply) becomes congested with blood and is tender to the touch
What is lymphedema?
When parts of the lymphatic system is removed surgically or tumor block a lymphatic
How is the lymph transported?
1) milking action of active skeletal muscles
2) pressure changes in the thorax during breathing
3) valves
4) pulsation of nearby arteries
5) smooth muscles in their walls
6) movement of adjacent tissue
Where does the right lymphatic duct empties?
At the junction of the right internal jugular and subclavian veins
Where does the thoracic duct empties its lymph?
Left internal jugular and subclavian veins
What does the lymphoid cells consists of?
Immune system cells, supporting cells
1) T cells (manages the immune response, & directly attack and destroy infected cells)
2) B cells produces plasma cells which secretes antibodies into the blood which marks antigens for destruction
3) macrophages (phagocytize foreign substances)
4) dendritic cells (captures antigens & brings them to the lymph nodes)
5) reticular cells (produces reticular fiber “stroma” supporting cells of the lymphoid organ)
What is a lymphoid tissue?
Mainly composed of reticular connective tissue
1) Houses lymphocytes and provides a site where they can be activated and proliferate
2) Furnishes an ideal surveillance vantage point for lymphocytes and macrophages
Two types:
1) diffuse lymphoid tissue
2) lymphoid follicles (nodules)
What is the diffuse lymphoid tissue?
loose arrangement of lymphoid cells and some reticular fibers found in every body organ. Larger collections appear in the lamina propria (loose connective tissue) such as those lining the digestive tract
What is the lymphoid follicles (nodules)?
solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers. often have lighter-staining germinal centers where proliferating (rapidly dividing) B cells predominate, which enlarge when the B cells are dividing rapidly and producing plasma cells. ln many cases, the follicles form part of larger lymphoid organs, such as lymph nodes. However, isolated aggregations of lymphoid follicles occur in the intestinal wall as Peyer’s patches (aggregated lymphoid nodules) and in the appendix
What are the lymphoid organs?
1) primary lymphoid organs:
- thymus
- red bone marrow
2) secondary lymphoid organs:
- lymph nodes
- spleen
2b) MALT (mucosa associated lymphoid tissue)
- tonsils
- prayers patch (lymphoid nodules in the S.I)
- appendix
What is the difference between the primary and secondary lymphoid organs?
Primary is where B & T cells mature, secondary lymphoid organs are where the mature lymphocytes encounter their first antigens and are activated
What is the lymph node function?
1) cleansing the lymph
2) immune system activation
What is the structure of the lymph nodes?
Bean shaped, surrounded by dense fibrous capsule where connective tissue (trabeculae) extend inwards forming the compartments. It’s internal network are formed by reticular fibers which supports the changing population of lymphocytes
They have a:
1) cortex (superficial part contains packed follicles with germinal layers heavy with diving B cells, and its deeper sites houses T cells, it is abundant with dendritic cells associated with both T and B cells)
2) medulla (consists of medullary cords, thin inward extensions from the cortical lymphoid tissue. Where Both B and T lymphocytes are found)
3) lymph sinuses (lymphatic capillaries, spanned by reticular tissue which contains numerous macrophages)
Where is the location of the lymph nodes?
1) inguinal region
2) axillary region
3) cervical region
How does the lymph nodes clean the lymph?
They act as lymph filters where their macrophages remove & destroy microorganisms & other debrise preventing their spread
How does the lymph nodes activate the immune system?
It is where lymphocytes encounter their first antigens & are activated to mount an attack against them which where brought by the dendritic cells
What is the circulation in the lymph nodes?
1) lymph enters from the afferent lymphatic vessels
2) subcapsular sinus
3) medullary sinus
4) exits from the hilum via efferent lymphatic vessels
What is lymphadenopathy?
Is is when the lymph nodes becomes overwhelmed by the antigens they encounter causing the lymph node to become inflamed, swollen, & tender to the touch
What is the structure of the spleen?
Size of a fist, largest lymphoid organ served by the splenic artery and vein which enters from its hilum, surrounded by a fibrous capsule and contains trabeculae which extend inwards, it consists of two parts:
1) white pulp (composed of lymphocytes suspended on reticulocytes where immune functions takes place)
2) red pulp (where worn-out RBC and blood borne pathogens are destroyed, contains huge amount of RBC and macrophages, It consists of splenic cords, regions of reticular connective tissue, that separate the blood-filled splenic sinusoids (venous sinuses))
What is the function of the spleen?
Provides a site for lymphocytes proliferation, immune surveillance & response, it also cleans the blood by extracting aged and defected blood cells & platelets and its macrophages removes debris and foreign matter.
It also:
1) recycles breakdown products of RBC
2) Stores platelets, monocytes and iron
3) can be a site of erythrocytes production in the fetus
What is meant by MALT?
Mucosa-associated lymphoid tissues, they are a set of distributed lymphoid tissues located in the mucous membranes through the body which protects us against never ending number of pathogens
What are the major components of MALT?
1) tonsils
2) payers patches
3) appendix
4) mucosa of respiratory system
5) mucosa of genitourinary organs
6) digestive track
What is the tonsils?
Ring of lymphoid which (contains follicles with obvious germinal centers surrounded by diffusely scattered lymphocytes) tissue around the entrance of the pharynx, the epithelium lining them invaginates deep into their interior, named according to their locations:
1) lingual tonsil (base of the tounge)
2) pharyngeal tonsil (posterior wall of the nasopharynx)
3) tubula tonsils (opening of the auditory tubes into the pharynx)
What is the function of the tonsils?
gather and remove many of the pathogens entering the pharynx in food or in inhaled air
What is the tonsillar crypts?
Invagination of the epithelium into the interior of the tonsils where bacteria are trapped and work their way to the lymphoid tissue where they are destroyed this way produces immune cells that have a memory for the trapped pathogen
What is preyers patches?
Aggregated lymphoid nodules located in the wall of the small intestine
What is the appendix?
tubular offshoot of the first part of the large intestine and contains a high concentration of lymphoid follicles.
1) prevent bacteria (present in large numbers in the intestine) from breaching the intestinal wall
2) to generate many “memory” lymphocytes for long-term immunity.
What is the structure of the thymus?
Bilobed, found in the inferior of the neck and extends to the superior of the thorax, resembles a cauliflower which there heads are the thymus lobules containing outer cortex (densely packed with rapidly dividing lymphocytes, with few macrophages) and and Inner medulla (containing fewer lymphocytes and thymus corpuscles (concentric rings of keratinized epithelial cells “site of T cell destruction” and the corpuscles are also involved in the development of regulatory T cells to prevent autoimmune responses))
What is the function of the thymus?
1) T lymphocytes precursor matures to become immunocompetent
How is the thymus (primary lymphoid organ) different from secondary lymphoid organs?
1) thymus has no follicles as it lacks B cells
2) doesn’t directly fight antigens
3) their stroma consists of epithelial cells rather than reticular fibers
What is a lymph node?
Small organs associated with lymphatic vessels
