Lymphoid System Part I Flashcards
Functions of Lymphoid System
- drain excess interstitial fluid and return it to the blood. (one way flow to subclavian veins)
- In the small intestine aid in lipid (fat) absorption
- Lymphocytes –> body’s defense against disease causing organisms
Lymphatic Capillaries
found in interstitial spaces of vascular tissue (composed of endothelial cells)
Once fluid enters the lymphatic capillaries is called lymph (fluid connective tissue)
Excess drainage is necessary –> edema
Lacteals
lymphatic capillaries that transport absorbed lipids away from the digestive track
Lymphatic Vessels
merged lymphatic capillaries; similar to veins
Lymphatic Trunks
merged lymphatic vessels; drain larger body regions
Lymphatic Vessels and Trunks are similar to ________.
veins; 3 layers and 1 valve; prevent back flow
Mechanisms for Lymph Movement (similar to venous return)
- skeletal muscle contraction
- Respiratory Pressure Changes
- Intestinal Movements
- Peristaltic Contractions of some Lymphatic Veins
Lymphatic Duct
receive lymph from lymphatic trunks
Right Lymphatic Duct
drains right part of the head and neck; right upper limb and right thoracic region
Right Lymphatic Duct drains to _______.
right subclavian vein
Thoracic Duct
begins at the abdominal cavity as a sac like enlargement _________. Drain left thoracic region, left upper limb, left side of the face and neck and all areas below the diaphragm.
Cisterna Chyli
Sac like enlargement that fives rise to the thoracic duct
Thoracic Duct empties to __________.
left subclavian vein
Primary Lymphoid Organs
- red bone marrow
- thymus
Site where lymphocytes origin
Primary organs; originate from stem cells in the bone marrow.
Types of Lymphocytes
- T cells (migrate after maturation to Thymus)
- B cells (after maturation to bone marrow or lymph nodes)
- Natural Killer Cells
Secondary Lymphoid Organs
- Lymph nodes
- Tonsils
- Spleen
Site where lymphocytes proliferate and immune responses
secondary lymphoid organs
tonsils
small masses of lymphoid tissue, located in the back of the throat, pharyngeal region.
Function of tonsils
- play a role in the immune system’s defense against pathogens, that enter the body through the mouth and nose.
- Initiate immune responses by producing antibodies and activating immune cells such as lymphocytes.
Where is red bone marrow found
spongey bone of axial skeleton and proximal epiphyses of femur and humerus
Red Bone Marrow
site of origin of all formed elements in blood
Immunocompetent
capable of recognizing and attacking a foreign substance; must be able to elicit and immune response.
True or False: every lymphocyte produced by the red bone marrow is immunocompetent
false
B cells become immunocompetent in ______ and T cells mature and become immunocompetent _______ before traveling to secondary lymphoid organs.
red bone marrow and thymus
Thymus
bilobed located above the mediastinum and above the heart.
Why is the thymus large in infants?
large in infants, decreases with age; plays an important role in the development of lymphoid system before birth and during early childhood. Matures after 2 years.
Functions of the thymus
- differentiation of T cells
- produces thymosins
Thymosins
produced by Thymus , promotes T cell differentiation and division, become immunocompetent
Lymph Nodes
occur along larger lymphatic vessels; 1.0 - 2.5 length; site of lymphocyte activation and proliferation.
Location of Lymph Nodes:
- Axillary
- Cervical
- Inguinal
- Thoracic and abdomino- pelvic cavity
True or False: There are lymph nodes in the central nervous system
false
Lymph Nodules
collection of lymphocytes and macrophages within reticular tissue; part of the lymph node structure.
Flow Trajectory through lymph node
- Afferent Lymphatic Vessel: enter
- Lymphatic Sinuses (surround lymph nodules)
- Efferent Lymphatic Vessel: exit
- Hilum
Function of lymph node
cleanse and filter lymph. Trapped particles are destroyed by macrophages and lymphocytes
Lymphocytes remove _______ .
cancerous cells and pathogens
Macrophages remove ______.
cellular debris, dead/ immobile bacteria and viruses.
Spleen
largest lymphoid organ (5-7 cm wide and 13- 16 cm long) found in the left upper quadrant of the abdomino - pelvic cavity. Enveloped by a thin capsule of dense irregular connective tissue, divided into compartments by reticular tissue.
Spleen is a site for ______ .
For proliferation and large venous sinuses.
White Pulp
tissue inside spleen compartment, that has a large number of lymphocytes, concerned with immune responses.
Red Pulp
tissue inside spleen compartment, used to store formed elements. Surrounds white pulp and the venous sinuses ;
site where worn out pathogens and RBC are removed.
Function of spleen in fetus
major blood forming organ
Function of spleen in adults
- cleanse and filter blood, through lymphocytes and macrophages.
- store reserve supply of red blood cells and platelets which can be released in blood in times of need.
- Major site of RBC destruction and recycling
- major site of lymphocyte activation and proliferation
Splenectomy
spleen not essential for life; more susceptible to potential pathogens and the effects of hemorrhage
Tonsils
lymphoid tissue beneath mucous membrane of pharynx and oral cavity.
contain lymphocytes and macrophages
Intercept pathogens that enter through the nose and mouth before entering the blood
Palatine Tonsils
junction of oral cavity and pharynx
Pharyngeal (adenoid) Tonsils
behind nasal cavity; in the upper portion of the pharynx
Lingual Tonsils
base of tongue in the back of oral cavity
tonsilitis
condition characterized by inflammation of the tonsils, which are located in the back of the throat.
What causes tonsillitis?
- Virus (common cold or Epstein Barr, causes infectious mononucleosis)
- Bacterial infection (streptococcus)
Tonsillectomy
recurrent cases of tonsillitis or if complications such as abscess formation. Affect a person’s quality of life and health.
Mucosa Associated Lymphoid Tissue (MALT)
individual lymph nodules (collection of macrophages and lymphocytes) trapped in reticular tissue located throughout the body that provide additional barriers to pathogen invasion
Where is MALT located?
- Respiratory
- Reproductive
- Digestive
- Urinary
Appendix
extension of the large intestine; located in the right lower quadrant of the abdomino- pelvic cavity
Helps control bacterial growth in the large intestine
Lymph nodule, Lymphoid follicles or lymphoid aggregations
localized clusters of lymphoid tissue found in organs (spleen, tonsils, and lymph nodes)
Composed of densely packed lymphocytes (primarily B cells) and can contain germinal centers where B cell proliferate and differentiate into antibody producing plasma cells.
Function of lymph nodules
sites for immune surveillance and response; help filter lymph and blood, trap antigens and initiate immune reactions against pathogens.
Non - Specific Resistance
protect against all pathogens and foreign substances; not direct
Mechanical Barrier (Non- specific resistance)
skin, mucous membrane, tears, saliva, and vaginal secretion
Skin (mechanical barrier; non - specific resistance)
closely packed epidermal cells; makes penetration of pathogens difficult
Mucous membrane (mechanical barrier; non - specific resistance)
produce mucus lining the respiratory and digestive tract; entrap pathogens and usually prevent their contact with underlying membranes.
Fluid Mechanical Barriers (non- specific resistance)
help flush away pathogens before they can attack body tissue
1. tears
2. saliva
3. vaginal secretion
4. urine flow
Chemical Reactions:
lysozyme, pH of the skin, gastric juice, interferon and complement
Lysozyme (Enzymes; chemical reaction; non specific defense)
destroys certain type of bacteria, present in tears, saliva, nasal secretion and perspiration
Acidic pH of the Skin (chemical reaction; non - specific defense)
inhibits bacterial growth
Gastric Juice (chemical reaction; non- specific defense)
pathogens that tonsils miss are swallowed at frequent intervals. low pH and enzyme pepsin
Interferon (chemical reaction; non- specific defense)
produced by viral infected cells; cause infected cells to make proteins that inhibit viral replication (rapid growth of virus inhibited)
Complement/ Complement Fixation (chemical reaction; non- specific defense)
plasma proteins that bind to certain pathogens initiating a chain of events that leads to the destruction of the pathogen.
Complement Fixation enhances ________ and ________.
phagocytosis and inflammation
Phagocytosis (chemical reaction; non- specific defense)
engulfing and destruction of pathogens, damaged or cancerous cells and cellular debris. Carried by neutrophils and monocytes.
Who carries out phagocytosis?
neutrophils and monocytes
Macrophages
monocytes that enter infected tissue
tissue macrophage system
some macrophages remain in a fixed position
tissue macrophage system can be found in?
spleen
red bone marrow
liver
inner walls of blood and lymphatic vessels.
Inflammation (chemical reaction; non- specific defense)
localized response to infection or injury
promotes pathogen destruction; healing process
characterized by redness, pain, heat and swelling
Histamine and complement proteins
are produced with an injury or infection, which dilate arterioles and increase capillary permeability
Blood flow increases, causes redness and heat
Irritation of nocireceptors
results in pain during the process of inflammation by pathogens, swelling or chemical from infected cells.
Fibrinogen and Fibroblasts
attract WBC and work to seal oof the infected area and prevent pathogen spread
pus
white fluid; accumulated mass of living and dead WBC, tissue cells and bacteria
forms at site of inflammation.
Fever (chemical reaction; non- specific defense)
high blood temperature (useful purpose as long as body temp doesn’t get to high)
function of fever
- inhibit growth of certain pathogens
- Increases rate of body processes (those that fight infection)
Natural Killer Cells (chemical reaction; non- specific defense)
immune surveillance
kill viral infected cells, bacteria, transplanted cells and tumor cells
Immunity (specific resistance)
directed at a specific antigen; it has memory (allows a quicker and stronger response to subsequent infections)
antigen (protein and glycoproteins)
any substance that can cause an immune response (production of specific cells and substances that attack a specific antigen)
Specialization of lymphocytes
must mature and become specialized within primary lymphoid organs before they can participate in immunity
T cells in the thymus
B cells in the red bone marrow
Percent of T cells in the blood
75%
Percent of B cells in the blood
25%
Recognizing Pathogens
cells of each person has a unique set of surface recognition molecules called antigens. Lymphocytes learn how to distinguish self from non- self cells and launch an attack
each B and T cell have specific receptors that bind with a specific antigen
graft rejection
lymphocytes recognize a transplanted organ as foreign
autoimmune disease
lymphocytes fail to recognize certain body tissues as self and attack the body’s own tissue
Cell Mediated Immunity
- T cells activated and phagocytosis stimulated
- Direct Attack against foreign antigens by chemical and physical means
- Destroys intracellular pathogens and foreign diseased cells and transplanted cells
True or False: T cells develop a memory for their antigens
true
Step #1: Cell Mediated Immunity
begins when antigen presenting cell (APC), macrophage that engulfs a foreign antigen.
Part of the antigen is expressed in plasma membrane
Step #2: Cell Mediated Immunity
T cell that can bind to the antigen on the APC, is activated and begins repeated mitotic division.
Forms clone of T cells which are capable of binding with the same antigen that activated the parent T cell.
Step #3: Cell Mediated Immunity
Active Th Cells
If activated T cell is a helper T cell (Th) it forms clones with mostly Th cells along with memory T cells. bind to antigens and secrete cytokines
cytokines
produced by active Th cell in cell mediated immunity;
1. attract neutrophils and macrophages and stimulate phagocytic activity.
2. Stimulate mitotic division and immune responses of activated B and cytotoxic T cell.
Step #3: Cell Mediated Immunity
Active T cell is cytotoxic T cell (Tc)
if rooms mostly active Tc cells along with some regulatory T cell. Binds to any cell displaying the antigen; releases lethal dose of chemicals to kill the cell.
T memory cells
remain after pathogen is eliminated; allow for a quicker attack if encountered again
Regulatory T cell
monitor and direct actions of cytotoxic T cells by releasing cytokines that prevents cytotoxic T cells from being over active.
Step #4: Cell Mediated Immunity
As more active T cells are produced and the pathogen is eliminated, the immune response slows and stops.
Antibody Mediated Immunity:
- B cells activated to become antibody producing plasma cells
- Indirect attack by producing antibodies that bind foreign antigens
- Bind extracellular pathogens for destruction by phagocytosis and other means.
Involves both B and Th cells
provide defense against extracellular pathogens
antibodies
bind to foreign antigens tagging them for destruction.
Step #1: Antibody Mediated Immunity:
antigen recognition: begins when foreign antigens bind to B cell receptors
Step #2: Antibody Mediated Immunity:
- B cell activation; B cell engulfs antigen and displays it on its plasma membrane
- TH cell binds to the displayed foreign antigen. Secretes cytokines that activate B cells.
Step #3: Antibody Mediated Immunity:
Clone Formation; clone of identical B cells, that produce the same antibodies against the specific antigen.
Step #4: Antibody Mediated Immunity:
Differentiation; most B cells in the clone become plasma cells. Some become memory B cells, that allow for a stronger response in a later encounter.
Step #5Antibody Mediated Immunity:
Action; plasma cells rapidly produce and release antibodies capable of biding with the targeted antigen
Antibodies ( immunoglobulins)
known as globulins (proteins)
its structure determines its classification
Function of Antibodies
they form an antigen body complex (complement fixation) they also neutralize bacterial toxins by binding the antigens (prevent toxins from attaching to body cells)
antigen antibody are engulfed and destroyed by macrophages, eosinophils and neutrophils.
IgG 75%
located in the plasma
1. Long term immunity, following vaccination or recovery from infection.
2. Crosses the placenta to give passive immunity to newborn infants
3. Most important in fixing complement
IgA 15%
Located in saliva, tears, mucus, breast milk and plasma
1. protects mucus membranes from pathogens
2. Provide passive immunity for breast- fed infants
IgM 10%
Located in B cells and plasma
1. release from B cells and agglutinates antigens
IgD 0.2%
B cells;
1. receptors on B cells
IgE 0.02%
mast cells and basophils
1. triggers allergic reaction by causing release of histamine when bind to allergen
