Lecture 6 Lymphatic Flashcards
What are the 3 roles of the lymphatic system
- Drainage of interstitial fluid
- Transport of digested products of fats
- lacteal: lymph vessels of the small intestine - Protection complementary to immune system
What is interstitial fluid
Fluid that remains in the tissue spaces
What does interstitial fluid contain ( 5)
- leukocytes (WBC) mobile units
- small proteins
- electrolytes
- dissolved gasses
- sugars
The majority of the filtrate of lymphatic system is what?
Plasma
- has passed from capillaries to the interstitial fluid
What happens to interstitial fluid after passing through lymph vessels
Its reabsorbed downstream
How many liters per day of interstitial fluid enters the lymphatic vessels and eventually return to the blood
3 L per day
When does interstitial fluid become lymph
When it enters and circulates inside the lymphatic vessels
How are lymphatic capillaries located in relation to vascular capillaries
They are blind ended so closed vessels that interweave between the vascular capillaries
Where are there NO lymphatic vessels
Bone
Red bone marrow
CNS (brain and spinal cord)
What are 3 structures in lymphatic system
Lymph duct
Lymph trunk
Lymph node
What is structure of lymph vessels
- endothelial squamous cells that overlap which make flap like mini valves. The mini valves are not firmly attached
- attached to c.t. by fine filaments to give it integrity
What is the function of the lymphatic vessels
-the mini valves on lymphatic vessels open and close so fluid can drain into them when there is excess interstitial fluid
What is the route in the circulation of lymph
- unidirectional (towards the heart)
- movement fron capillarie to vessel occurs by diffusion (due to differences in size of vessels)
Characteristics of lymphatic vessels
- structurally similar to veins
- higher density of valves and anastomose
Lymphatic capillaries merge to form what
Larger lymphatic and eventually form the main lymphatic trunks, the right lymphatic ducts and the thoracic duct
Where does lymph from upper right quadrant empty into
Into right lymphatic duct and then right subclavian vein
Where does lymph from rest of the body empty into
The thoracic duct and then drains into the left subclavian vein; thoracic duct originates as the cisterna chyli (chyle cistern)
What is grouped in clusters along the lymphatic vessels
Lymph nodes
What are the main clusters of lymph nodes (6)
- Inguinal (pelvis)
- Cubital
- Axillary (armpits)
- Cervical
- Preauricular
- Submaxillary
What is the capsule of the lymph node
- envelop of dense c.t. that surrounds the node and divides the interior as it penetrates the structure forming compartments.
- the divisions of the interior are called trabeculae
What are the 3 inner structures of the lymph node
Cortex
Medulla
Medullary sinus
What are the functions of the lymph nodes
Filtration and phagocytosis
- cortical and medullary sinuses are lined with reticuloendothelial cells
- these cells are macrophages and capable of phagocytosis
And some hematopoiesis of Lymphocytes
Why do they say accessory organs of lymphatic system are located in strategic locations
Because they are where potential for a pathogen invasion is high (I.e. skin, intestine..)
What are the 5 accessory organs of the lymphatic system
- Tonsils (pharyngeal region)
- Thymus (in thorax, most active in youth)
- Spleen (curves around L side of stomach)
- Peyer’s patches (aggregated lymphoid nodules in small intestine)
- Appendix (RLQ)
Where is the spleen located
Anatomical left side of the abdominal cavity
- beneath diaphragm
- behind the stomach
It is richly vascularized (++ blood vessels)
What are the functions of the spleen(4)
- Proliferation of Lymphocytes site for erythropoiesis - fetus
- Purifies blood (destroys debris)
- RBC and platelets destruction
- Blood reservoir
What are the 2 features of the spleen
White pulp:
- T&B Lymphocytes are suspended among the reticular fibers
- form clusters ‘cuffs’ around the central arteries
Red pulp:
- sinusoid (venous sinuses)
- splenic cords (reticular c.t. containing RBC & macrophages)
What is the location of the thymus
In the mediastinum, partially covers the heart
What is the function of the thymus
- release and circulation of hormones (Thymosin)
- they stimulate the maturation of Lymphocytes T ( making them immuno competent/ immunoreactive)
- thymus ordinarily atrophies with age
What are the components of the thymus
- 2 lobes (bilobed)
- those lobes are divided into globules by septum (Capsule, cortex, medulla: thymic corpuscles)
What is the location of the tonsils
Forms a ring at the entry to the pharynx
What are the 4 tonsils
- Pharyngeal (posterior wall of nasopharynx)
- Tubal (surround opening of auditory tubes in pharynx)
- Palatines (posterior end of oral cavity, biggest and most frequently infected)
- Lingual (base of the tongue)
What are the components of the tonsils
- follicles with lymphocytes
- crypts that capture intruders
What is the function of the tonsils
Destroys intruders brought via air & food to the pharynx
What is adenopathy
Enlargement of the lymphatic nodes often associated with inflammation and tumors
What is tonsilitis
Inflammation of the tonsils; often caused by infectious bacteria can be acute or chronic
What is elephantitis
Tropical disease where the lymphatic vessels are obstructed by parasitic worms (filarial nematode) resulting in extreme edema
What is splenomegaly
Increase in volume of the spleen because of infectious organisms; can result in HTN or anemia
Hodgkin’s disease
Cancer of the lymphatic nodes; painless edema of the lymphatic nodes
What is mononucleosis
Frequent viral disease (Epstein barr) transmission: saliva
swollen lymphatic nodes
Lasts about 4-6 weeks
What is an antigen
- macromolecule that induces immune system response
- can be self or non-self (foreign)
What is immunocompetence
- effective response to antigen
What is cytokines
- involved in many immune functions
- interleukins, leukotrienes, interferons
What is non-susceptibility
“Species resistance”
- absolute protection against a given disease or diseases
- genetic link = dont have receptors for antigen binding
- internal environment differences
- small percentage of the population
What is the first line of defense of the immune system
Barriers
- physical
- chemical
What are the physical and chemical barriers of the first line of defense
•skin and mucosa
- wall that separate internal and external environment
•Sebum
- contains pathogen inhibiting chemicals
•mucus in respiratory
- traps pathogen which are swept away by cilia
•Gastric juices
- destroys pathogens
•Acidity
- ex. In vagina
What is the 2nd line of defence
Barriers
- inflammatory response
- biological
What are the important components of the inflammatory response
- Kinins (hormone that stimulate prostaglandins ex. Bradykinin)
- Histamine ( stimulate vasodilation of arterioles)
- Chemotactic agents ( attraction of cells toward a given area)
What are the 5 classic symptoms of the inflammation response
Redness Heat Pain Swelling Impairment of function
What are the biological barriers in the second line of defence
- phagocytes
- natural killer cells (clean & promote apoptosis)
- fever (increased system activity, trigger pyrogenic effect)
- complement (grp of proteins which cause cytolysis)
- interferons (proteins that inhibit viral replication)
What are the phagocytosis of 2nd kine of defense
- responsible for ingestion and destruction of foreign particles
- some display protein fragments from destroyed cells - antigen presenting cells
- short life span - dead cells make pus
- 10 to 15% of all cells are phagocytes
- dendritic cells, macrophages - important APCs
What is the process of phagocytosis in the 2nd line of defence
- Phagocyte adheres to pathogen or debris
- Phagocyte makes pseudopods that engulf the particles = phagosome
- Lysosome fuses with phagocytic vesicle forming phagolysosome
- Lysosomal enzymes digest the particles leaving residual body
- Exocytosis of the vesicle removes indigestible and residual material
What is complement of second line of defence
- group of ~20 inactive plasma and surface proteins
- involved in complement cascade (classical, lection, alternative)
- produce membrane attack complex (MAC)
- can also act as anaphylatoxins, opsonization
What are the natural killer cells of 2nd line of defence
- group of Lymphocytes produced in RBM
- broad range of targets, no specific antigen
- recognition depends on 2 receptors
- destroys cells via apoptosis, requires receptor binding
What are the 2 receptors that recognition depends on in natural killer cells
Kill-activating
- binds to many common surface molecules
Kill-inhibiting
- binds to major histocompatibility complex (MHC) I
What is interferon of second line of defence
- protein released by cells in response to viral infection
- promote release of enzymes that block viral replication
- three major types: (leukocyte, fibroblast, immune)
- some promote synthesis of MHCs
