Lymphatic and Immune System Flashcards
What are the functions of the lymphatic system?
- fluid recovery: 15% of water and plasma proteins enter lymph system from capillaries and returns to blood or tissue spaces
- immunity: fluid passes through lymph nodes where immune cells guard and it activates immune responses
- lipid absorption: lacteals in small intestine to absorb dietary lipids
How does lymph flow and return to the bloodstream:
Lymphatic Capillaries: they penetrate every tissue in the body except cartilage, bone, bone marrow, and cornea. -The structure: a capillary wall overlapping endothelial cells and valve like flaps within the endothelium lined tube
Lymphatic Vessels: two collecting ducts
-right lymphatic duct: receives lymph from right arm, right head and thorax and empties into right subclavian vein
-thoracic ducts: larger and longer, receives lymph from below diaphragm, left arm, left hand, neck and thorax. It empties into left subclavian veins
-Subclavian veins collect from thoracic ducts
Flow of Lymph: lymph flows through lymphatic vessels with valves and prevents backwards flow.
-aided by skeletal muscle pump and thoracic pump
-arterial pulsing squeezes lymphatic vessels
Name the major cells of the lymphatic system and their function
NK Cells: large lymphocytes that attack bacteria, transplanted tissue, and host cells infected with virus or cancer
T lymphocytes: mature in thymus
B lymphocytes: activation produces antibodies
Macrophages: large cells that develop from monocytes. Also antigen presenting cells, and it cleans up debris and foreign matters
Dendritic cells: branched and mobile antigen presenting cells in empidermis, mucous membranes and lymphatic organs
Reticular cells: branched stationary cells that contribute to the stroma of a lymphatic organ
What are the types of lymphstic tissue?
Diffuse lymphatic tissue: mostly in body passges open to exterior and contains mucosa associated lymphatic tissue
Lymphatic Nodules: feature of the lymph nodes, tonsils and appendix
Lymphatic Organs: an organ with a connective tissue capsule that sperates lymph tissue from other tissues
1. primary lymph organs: red bone marrow, thymus
2. secondary lymph organs: lymph nodes, tonsils and spleen where immunocompetent cells live
Thymus
Member of the endocrine, lymphatic and immune system
Structure: bilobed organ in between sternum and aortic arch
Function: houses developing T lymphocytes and secretes hormones that regulate their activity
Lymph Nodes
Most numerous lymph organ with 450 in a young adult
Structure: fibrous capsule with trabeculae that divides the interior into compartments
Function: cleanse the lymph and is where T and B cells become activated
Extra: cancer cells can break free from tumor and enter lymph vessels where they make a new home in the first node they see
Tonsils
Patches of lymphatic tissues at the entrance of the pharynx
Structure:
1. palatine tonsils at the posterior end of oral cavity that is typically infected
2. lingual tonsils: pair at root of tongue
3. pharyngeal tonsil (adenoids): single tonsil on wall of nasopharynx
Function: guard against ingested or inhaled pathogens
Spleen
Largest lymphatic organ
Structure:
-red pulp: sinuses filled with erythrocytes
- white pulp: lymphocytesz and macrophages surrounding small branches of splenic artery
-the spleen is highly vascular and vulnerable to injury
Function: healthy RBC travel through but old RBC die here
Red Bone Marrow
Structue: contains hematopoietic cells as vascular tissue in bones
Function:
-produce all RBC
- T and B cells begin life here and become fully formed in lymphatic tissue
Innate Defenses vs. Adaptive Immunity
Innate Defenses: equally guard against pathogens without specificity and memory
Adaptive Immunity: body develops seperate immunity to each pathogen
Interferons
An antimicrobial protein that alerts neighboring cells and protects them from infection
Complement System
An activated complement brings 4 methods of pathogen destruction:
1. inflammation
2. immune clearance
3. phagocytosis
4. cytolysis
Fever
An abnormal increase in body temp. that has more benefits within moderation. It promotes interferon activities, elevates metabolic rate and tissue repair while inhibiting reproduction of bacteria and viruses
Processes and Signs of Inflammation
Process:
1. Mobilization of defenses: neutrophils move into and around vessel walls and tissue spaces
2. Containment and Destruction of Pathogens: neutrophils accumulate so much causing difficulty in the pathogen spreading around the body
3. Tissue Cleanup and Repair: monocytes do the cleaning and repair. Edema contributes to swelling and forces lymphatic drainage to occur, and pus may occur.
Signs:
1. heat
2. redness
3. swelling (edema)
4. pain
What are three characteristics of adaptive immunity?
- systemic effect throughout the body
- specificity against a particular pathogen
- memory, where the immune system can recognize the pathogen a second time and destroy it quickly
Active vs Passive Immunity
-Active immunity is when our own immune system protects us from pathogens
-Passive immunity is when we are protected from a pathogen through someone else’s immunity that we gained (vaccine)
Cell-mediated vs Humoral Immunity
Cell-mediated: lymphocytes directly attack viral or diseased cells that antibodies cannot reach. Usually T-cells (t cells attack tissues)
Humoral: mediated by antibodies that tag a pathogen for destruction and is most useful in infectiongs by microorganisms. Usually B-cells (antibodies travel through blood)
Natural Passive vs Artificial Passive Immunity
Natural Passive: temporary immunity where the antibody is gained from another person. Ex: placenta and fetus
Artifical Passive: temporary immunity after injection of immune serum (antibodies)
Describe an antigen
Any molecule that triggers an immune
response
– Complex molecules with structures unique to the
individual
– Proteins, polysaccharides, glycoproteins, glycolipids
– Characteristics enable body to distinguish “self” molecules from foreign ones
* Epitopes (antigenic determinants)—certain regions
of an antigen molecule that stimulate immune
responses
Describe an antibody
Antibodies vary, but there are 5 main types. The two most common are IgG and IgE.
T-cell Development
Life stages:
- Born in bone barrow
– Educated in thymus (become immunocompetent)
– Deployed to carry out immune function (Naive lymphocyte leave thymus and colonize lymphatic tissues)
B-cell Development
-B cells develop in bone and some fetal stem cells remain in bone marrow to become B cells.
-B cells that react to self-antigens undergo either anergy
or clonal deletion, same as T cell selection
-Self-tolerant B cells synthesize antigen surface receptors,
divide rapidly, produce immunocompetent clones
-Leave bone marrow and colonize same lymphatic tissues and organs as T cells
Antigen Processing and Antigen Presenting Cells
The function of APC is dependent on MHC protein complex.
– MHC-I proteins
* Constantly produced by nucleated cells,
transported to, and inserted on plasma membrane
– MHC-II proteins (human leukocyte antigens, HLAs)
* Occur only on APCs and display only foreign
antigens
Antigen processing
– APC encounters antigen
– Internalizes it by endocytosis
– Digests it into molecular fragments
– Displays relevant fragments (epitopes) in the grooves of the MHC protein
Antigen presenting
– Wandering T cells inspect APCs for displayed antigens
– If APC only displays a self-antigen, the T cell disregards it
– If APC displays a nonself-antigen, the T cell initiates an
immune attack
– APCs alert the immune system to presence of foreign
antigen
Antibodies Four Mechanisms of Action
- Neutralization
– Antibodies mask pathogenic region of antigen - Complement fixation
– IgM or IgG bind to antigen, change shape and initiate
complement binding which leads to inflammation,
phagocytosis, immune clearance, or cytolysis
– Primary defense against foreign cells, bacteria, and
mismatched RBCs - Agglutination
– Antibody has 2 to 10 binding sites; binds to multiple
enemy cells, immobilizing them from spreading
– Enhances phagocytosis by creating “bigger bites” - Precipitation
– Antibody binds antigen molecules (not cells); creates
antigen–antibody complex that precipitates, allowing
them to be removed by immune clearance or
phagocytized by eosinophils
