NOTES: CH 43, part 1 –The Immune System - Nonspecific & Specific Defenses (43.1-43.2)
The lymphatic system is closely associated with the cardiovascular system.
LYMPHATIC PATHWAYS
Lymphatic capillaries
● microscopic, closed-end tubes that extend into intercellular spaces
● receive LYMPH through their thin walls (LYMPH = )
● lymphatic capillary networks
Functions of lymph:
1) returns to the bloodstream small proteins that leaked out of blood capillaries
2) , such as bacteria or viruses, to lymph nodes
**if lymph movement is impaired, it may accumulate within the intercellular spaces and produce EDEMA, or
(example: after surgery, the lymphatic vessels and lymph nodes around the wound may be damaged, causing fluid to accumulate around the surgery site and lead to swelling)
Lymph Nodes:
Structure of a Lymph Node:
● lymph nodes are subdivided into nodules
● nodules contain
Locations of Lymph Nodes:
● lymph nodes aggregate in groups or chains along the paths of larger lymphatic vessels
Functions of Lymph Nodes:
● filter potentially from lymph
● are centers for the (attack invading viruses, bacteria, parasites, etc.)
● (engulf and destroy foreign substances, damaged
cells, cellular debris)
THYMUS AND SPLEEN
Thymus:
●
● contains large numbers of LYMPHOCYTES which mature into T CELLS (T lymphocytes) – important in providing immunity (more on these later…)
Spleen:
●
● resembles a large lymph node (divided into lobules)
● spaces within splenic lobules are
● contains many macrophages, which destroy/remove foreign particles and damaged RBCs from the blood
**the spleen filters blood as the lymph nodes filter lymph!**
So, how does the body defend itself???
The body has against infection / pathogens.
●PATHOGEN: ; causes infection
-pathogens include:
Nonspecific Defenses:
● general defense
● provide protection against many different pathogens
● involve
Specific Defenses:
● very precise● target certain pathogens
● also known as
● involve specialized lymphocytes () that recognize and respond to specific pathogens
**nonspecific defenses are quick to respond;
NONSPECIFIC DEFENSES
1) Species Resistance
● each species is resistant to certain diseases that may affect other species
● examples: infect humans but not other animal species
● one species may be resistant to a disease that affects another species because its tissues somehow fail to provide a suitable environment for the pathogen (temperature, chemical environment, receptors, etc.)
2) Mechanical Barriers =
● mechanical barriers / physical barriers include:
- (and associated hairs)-
- (sweat and mucus)
● as long as they remain intact, they can keep out many pathogens
**all other “nonspecific defenses” are considered the
3) Chemical Barriers
●gastric juice: (e.g. pepsin) that are lethal to pathogens
●tears: contain the enzyme (which has antibacterial action)
● the salt in perspiration accumulates on the skin and kills bacteria on the skin
INTERFERONS:
● chemicals released by virus-infected cells; they stimulate other immune cells to synthesize antiviral proteins that stimulate phagocytosis, block virus replication
● most effective against cold and flu virus
● now mass-produced by recombinant DNA technology to be potentially used as treatment for viral infections and cancer!
COMPLEMENT SYSTEM:
●group of 30 proteins;
●catalyze a series of steps resulting in lysis of invading microbes and/or inflammatory response
4) Fever
●higher body temperature
● also lowers iron levels in the blood (bacteria and fungi require iron, so this )
5) Inflammation
● produces:
●HISTAMINE and prostaglandins released by damaged tissues attract WBCs to the site
the mass of WBCs, bacterial cells, and damaged tissue forms a
6) Phagocytosis –
● the most active phagocytes in blood are and
● Monocytes give rise to
●MACROPHAGES are found in the linings of blood vessels in the:
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EOSINOPHILS:
●
Specific Defenses / Immunity
THE IMMUNE SYSTEM = the body’s “third line of defense”
● characterized by:
●ANTIGENS: specific foreign molecules that ; usually located on a cell’s surface
-antigens include:
● before birth, body cells sort “self” proteins and other large molecules
● lymphocytes develop receptors that allow them to
● nonself antigens combine with T cell and B cell surface receptors and stimulate these cells to cause an immune reaction
LYMPHOCYTES (T and B Cells)
●originate in the
● some reach the , where they mature into
● others, the , mature in the
●both T cells and B cells reside in lymphatic tissues and organs (lymph nodes, spleen, etc.)
LYMPHOCYTE FUNCTIONS
**a lymphocyte must be before it can respond to an antigen**
Antigen Presentation:
● Carried out by a group of approx. 20 glycoproteins that make up the
(MHC)
Two main classes of MHC molecules:
Class I MHC:
*cytotoxic T cells (TC) bind to fragments of antigens displayed by class I MHC
Class II MHC: found only on specialized cells ()
*helper T cells (TH) bind to fragments of antigens displayed by class II MHC
Antigen-Presenting Cells (APCs):
-cells that take up antigens (B cells, macrophages);
-engulfed foreign matter binds to a class II MHC molecule and is
conveyed to the outside of the APC;
-foreign antigen is recognized by a helper T cells (TH);
-this interaction is enhanced by CD4, a membrane protein on TH cells.
*CLONAL SELECTION:
antigen-specific selection of a lymphocyte;
activates lymphocytes to divide and differentiate to produce CLONES of designed to eliminate the antigen that provoked the initial response
.!
● PRIMARY IMMUNE RESPONSE:
during this response, antibodies are produced for several weeks
antibodies first show up within
some B cells remain dormant as
● SECONDARY IMMUNE RESPONSE:
rapid response due to memory cells produced during the first exposure
antibodies produced within