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
Describe the medulla if the lobules of the thymus
Lighter staining with fewer, widely scattered and more mature T cells than in the cortex
Dendritic cells, epithelial cells and macrophages also present
Hassal’s corpuscles are present
What are Hassal’s corpuscles?
These are remnants of epithelial cells, filled with keratohyalin deposits
What happens to T cells when they leave the thymus?
T cells that leave the thymus via the blood migrate o lymph nodes, spleen and other lymphatic tissues
What are lymph nodes
Kidney or bean shaped organs responsible for filtration of lymph
They are encapsulated in a dense connective tissue capsule
Where are lymph nodes located?
Located along the lymphaticvessels occurring in clusters(e.g. axillary, cervical and inguinal)
What divide lymph nodes into lobules in the thymus
Trabecula
What are the functions of the afferent and efferent lymphatic vessels for the lymph nodes
Afferent and efferent lymphatic vessels permit flow of lymph into and out of node
What is the parenchyma in the lymph node divided into?
The parenchyma is divided into the outer cortex and deep medulla
Describe the outer cortex of the parenchyma of the lymph nodes
Densely packed with lymph nodules with B cells
What activity occurs in the outer cortex of the parenchyma of the lymph node?
B cells proliferate and differentiate into plasma cells (antibody producing cells) or memory cells
What does the deep the deep cortex of the lymph node consist of?
T cells, dendritic cells
Describe medullary cords
Dark staining inward extensions of the cortical lymphoid tissue , contain B lymphocytes, antibody producing plasma cells and macrophages
Describe the medullary sinuses
Irregular lymph channels containing reticular fibers, lymphocytes, macrophages
What is metastasis?
The spread of disease from one body part to another, can occur via lymphatic vessels
How can cancer cells travel around the body?
Cancer cells may travel in the blood or lymph and establish new tumors where they lodge
What is a clinical benefit of when metas is occurs in the lymphatic vessels?
When metastasis occurs in lymphatic vessels, secondary tumor sites can be predicted according to the direction of lymph flow from the primary tumor sites
How do cancerous lymph nodes feel?
Cancerous lymph nodes feel enlarged, firm, non-tender and fixed to underlying structures
What are the functions of the spleen?
- Filters and removes worn-out and damaged red blood cells ( RBCs) and platelets
- Storage of platelets
- Hemopoiesis during fetal life
Describe the spleen
Has dense connective tissue capsule and an outermost covering of visceral peritoneum
What does the stroma of the spleen consist of?
Capsule, trabeculae and reticular fibers
What does the parenchyma of the spleen consist of?
Red and white pulp (there are no lobules in the spleen)
Describe the white pulp of the spleen
- Consists of lymphocytes and macrophages suspended on reticular fibers surrounding central artery
- Involved with immune functions by B and T cells
Describe the red pulp of the spleen
- Veinous sinuses
2. Splenic cords
Describe the splenic cords of the red pulp of the spleen.
-reticular tissue rich in macrophages, lymphocytes, plasma cells, granulocytes, RBCs
What is the function of splenic cords of red pulp in the spleen?
Involved with disposing of worn-out RBCs and blood borne pathogens, storage of platelets and fetal hemopoiesis
Describe lymph nodules
Small egg-shaped masses of lymphatic tissue that are not surrounded by a capsule
Where are lymph nodules located?
Scattered throughout mucous membranes lining the gastrointestinal, urinary, reproductive and the respiratory therefore also called mucosa-associated lymphatic tissue( MALT)
Many are small and solitary, while other occur in clusters(tonsils)
What are mucosa associated lymphatic tissue/MALT?
Are small and solitary, while other occur in clusters
What are tonsils ?
Collections of lymphoid tissue around the aero digestive tract
What are tonsils strategically placed to do?
Tonsils are strategically positioned to participate in immune responses against inhaled or ingested foreign substances
How many tonsils are usually at the ring at the junction of the oral cavity and oripharynx and at the junction of the nasal cavity and nasopharynx. What are these tonsils?
Pharyngeal tonsil
Palatine tonsils x2
Lingual tonsils x2
What are lymphocytes?
The main warriors of the immune system
What do B lymphocytes protect against?
B lymphocytes usually protect against antigens
What do T cells do?
Manage the immune response, some of them directly attack and destroy infected cells
What is the function of macrophages?
Play a crucial role in body protection and in the immune response by phagocytizing foreign substances and by helping to activate T cells
What is the function of dendritic cells?
They capture antigens and bring them back to the lymph nodes
What are the functions of reticular cells?
These are fibroblast like cells that produce the reticular fiber stroma which is the network that supports the other cell types in the lymphoid organs
What are the cell types in lymphoid tissue?
B and T lymphocytes, reticulocytes, macrophages, plasma cells, dendritic cells
How are lymphocytes of lymphoid tissue?
Lymphocytes supported by a framework of connective tissue
What is the fiber type of lymphoid tissue?
Reticular fibers
Describe the deep medulla of the parenchyma of the lymph nodes
Medullary cords: dark staining inwards extensions of the cortical lymphoid tissue, contain B-lymphocytes, antibody producing plasma cells and macrophages
Medullary sinuses: irregular lymph channels containing reticular fibers, lymphocytes, macrophages
What is the flow of lymph in the lymph node?
- Afferent lymph node
- Subscapular sinus
- Trabecular sinus
- Medullary sinus
- Efferent lymphatic vessel
Contrast the chemical composition of outer cortex, inner cortex and medulla of a lymph node
Outer cortex lymph node- B cells, follicular dendritic cells and macrophages
Inner cortex- T cells and dendritic cells
Cells of medulla- plasma cells, B cells and macrophages
What cells line around the germinal epithelium of a lymph node?
B cells
