Structure and Function Flashcards
Structures of the lymphatic system
Lymph
Lymphatic vessels
Lymph nodes
Tonsils
Thymus
Spleen
Bone marrow
Drainage of Lymph
Lymph
- Clear, watery-appearing fluid found in the lymphatic vessels
- Isotonic
Interstitial fluid
Fills spaces between cells
Has a lower protein concentration
Lymphatic capillaries
- Microscopic vessels that are the origin of lymphatic vessels
Closed at one end - Wall of each capillary consists of a single layer of flattened endothelial cells
Circulation of Lymph
Water and solutes continually filter out of capillary blood into the interstitial
Lymphokinesis
The movement of lymph
Lymph nodes
Oval shaped structures enclosed by a fibrous capsule. Lymph enters a node and then moves slowly though sinuses to drain into an exit vessel
Where is the thymus located?
Mediastinum
What are the functions of lymph nodes?
Mechanical and biological filtration, haematopoiesis
What is the relationship between lymphatic and blood capillary networks?
They lie side by side but are always independent of each other
What do lymphatic capillaries merge to form?
Larger lymphatics and the main lymphatic trunks
Which direction does lymph move through a system?
I’m the right direction because of the larger number of valves
What extends from the capsule toward the center of a lymph node?
Trabeculae
What are medullary sinuses of the lymph node lined with?
Reticuloendothelial cells capable of phagocytosis
Thymus
Unpaired organ made up of two pyramidal lobes. Shortly after birth, thymus secretes thymosin and other hormones resulting in lymphocytes developing into T cells. Final site of lymphocyte development before birth
Where is the Thymus located?
Mediastinum
What colour is the thymus in childhood?
Pinkish grey
How are the lobes of the thymus subdivided?
Lobes of the thymus are subdivided into small lobules by connective tissue septa
Thymus point 2
Mechanical filtration
Stops particles from progressing further in the body
Biological filtration
Processes of cells. Phagocytosis destroys and removes particles
Haematopoiesis as a function of lymph nodes
Lymphoid tissue is the site of the final stages of B and T cell maturation
Tonsils
Protect against bacteria that may invade tissues around the nasal and oral cavities
Where are the tubal tonsils located?
Near the openings of the auditory (eustachian) tubes
Pharyngeal tonsils location
Near the posterior opening of the nasal cavity
Where are the palatine tonsils located
On each side of the throat
Where is the lingual tonsil located
Near the base of the tongue
Where is the spleen located?
Upper left quadrant of the abdomen
What is the spleen surrounded by?
A fibrous capsule
Spleen functions
Defence, tissue repair, haematopoiesis, blood reservoir, RBC and platelet destruction
Red pulp (spleen)
A network of fine reticular fibres submerged in blood that comes from nearby arterioles
White pulp (spleen)
Contains dense masses of developing lymphocytes
Each day, what percentage of proteins leak out of the capillaries into the interstitial fluid?
50%
Functions of the lymphatic system
Maintains fluid balance in the internal environment.
Lymph vessels act as “drains” to collect excess tissue fluid and return it to venous blood. Returns certain substances to the general circulation
What is interstitial fluid absorbed/reabsorbed by?
Interstitial fluid is absorbed by tissue cells or reabsorbed by the blood
Oedema (fluid retention) may lead to tissue destruction
