Lymphatic And Immune Systtem 1 Flashcards
What is lymph?
Ultrafiltrate of blood- interstitial fluid
How does Blood hydrostatic pressure(BHP) lead to lymph formation?
blood hydrostatic pressure (BHP) pushes fluid out of capillaries(filtration), and blood colloid osmotic pressure( BCOP) pulls fluid into capillaries (reabsorption)
Fluid remaining in the interstitial space passes into lymphatic capillaries, it is lymph
Small quantities of protein are filtered into the interstitial space, what happens to this protein?
This protein returns to blood via lymphatic vessels
What are the functions of the lymphatic system?
- Drains excess interstitialnfluid- lymphatic vessels drain excess interstitial fluid from tissue spaces and return it to blood
- Transport dietary lipids- Lymphatic vessels(lacteals)transport lipids and lipid soluble vitamins(A,D,E and K) absorbed by the GI tract
- Carries out immune responses- Lymphatic tissue initiates highly specific responses directed against particular microbes or abnormal cells
What vitamins are lipid soluble?
Vitamins A, D, E and K
Where are lymph vessels absent?
In a vascular tissue, CNS and bone marrow
Blind ended lymph vessels beginning in the spaces between cells are…
Anchored to the surrounding tissue by filaments
Describe small lymph vessels, their lining and convergence
- are thin-walled and lined by endothelium
- Small lymphatic capillaries converge to form larger vessels
What do lymph vessels generally follow?
Lymph vessels generally follow veins in subcutaneous tissue or arteries in visceral structures
How are mini valves formed in lymph vessels?
The edges of the endothelial cells overlap each other to form mini valves
What is the function of mini valves in lymph vessels?
Permit fluid to enter when pressure outside the vessel increases but not the reverse
How is general one way circulation assisted in larger vessels?
Larger vessels have smooth muscles in the walls and one-way valves to assist with return of lymph to general circulation
What are lymphatic trunks?
Sites that drain most of the lymph from the body into the veinous circulation
Name the main lymphatic trunks
- Jugular
- Subclavian
- Bronchomediastinal
- Intestinal
- Lumbar
What is unique about lymphatic drainage?
Drainage pattern on left and right side is different
Name the mechanisms of flow in lymphatic circulation
Skeletal muscle pump
Respiratory pump
Outline lymphatic circulation
- Lymphatic capillaries
- Lymphatic vessels
- Lymph nodes
- Lymph trunks ( Jugular, Subclavian, Bronchomediastinal, Intestinal, lumbar)
- Lymphatic ducts (right lymphatic duct and thoracic duct)
- Blood
What are examples of primary lymphatic organs?
Red bone marrow and the thymus
What are examples of secondary lymphatic organs?
Spleen, lymph nodules(follicles) and lymph nodes
What are Primary lymphatic organs?
Sites where stem cells divide and become immunocompetent
What are secondary lymphatic organs?
Sites where most immune responses occur
What is the thymus?
A bilobed organ located in the mediastinum and covered by dense connective tissue capsule
How does the thymus differ between infants and adults?
Thymus is large in infants
Thymus becomes involuted in adults
What is the function of the T cells?
Proliferation and maturation of T cells
What happens after T cells mature in the thymus?
Mature T cells leave the thymus via the blood stream and migrate to other lymphoid organs e.g. spleen, lymph nodes
How are the lobes of the thymus further divided?
Lobes further divided into lobules by penetrations called trabeculae
What does each lobule in the thymus consist of?
A cortex
A medulla
Describe the composition of the cortex of lobules in the thymus
Dark-staining, composed or large numbers of T cells and scattered dendritic cells, epithelial cells and macrophages
How does the cortex of the thymus uses the substances it is comprised of?
- Dendritic cells assist in maturation of T cells
- Epithelial cell surround maturing T cells and help in “educating” them
- Macrophages clean up debris and dead cells
- Mature T cells enter the medulla