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A&P 2: Chapter 22

Anatomy & Physiology 2 Lamar University Lecture-Armacost
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Lymphatic System
components: lymph and lymphatic vessels
Lymphatic System
functions: homeostasis, immune response, and transportation
Homeostasis (lymphatic system)
drains excess interstitial fluid
Immune Response (lymphatic system)
roles in innate and adaptive immunity
Transportation (lymphatic system)
movement of dietary lipids and lipid-soluble vitamins
Lymphatic Tissue
consists of connective tissue, like blood
Lymphatic Fluid
consists of lymph, and is essentially the same as interstitial fluid, contains many lymphocytes
Lymphatic System
anatomy: lymph vessels and lymphatic organs and tissues
Lymph vessels
includes lymphatic capillaries, vessels, trunks, and ducts.
Lymphatic Fluid (formation)
some components of blood plasma leave capillaries of circulatory system to become interstitial tissue in body tissues, excess interstitial fluid enters lymphatic capillaries to become lymph
Lymphatic Capillaries
are associated with capillary beds of circulatory system, are closed at one end, merge to form lymphatic vessels, and have large pores
Pores (lymphatic capillaries)
are associated with overlapping cells of endothelium, and allow lymph to enter, but not to exit
Anchoring Filaments (lymphatic capillaries)
attach lymph capillary to surrouding tissues, and pull open pores when tissues swell with excess fluid
Lymphatic Vessels
are similar to veins, and associated with lymph nodes
Lymphatic Vessels
possess many valves, which prevent back-flow, and merge into 5 lymph trunks
Lymphatic Vessels
pressure for movement of lymph is generated by the skeletal muscle pump and the respiratory pump
Lacteals
are specialized lymphatic capillaries in the small intestine
Lacteals
absorb lipid molecules from diet that are too large to enter blood capillaries; b/c lipids travel through lymphatic system before entering blood
Primary Lymphatic (organs & tissues)
sites where stem cells give rise to immunocompetent cells; includes red bone marrow, thymus
Secondary Lymphatic (organs & tissues)
sites where most immune responses occur; includes lymph nodes, spleen, and lymphatic nodules
Red Bone Marrow
pluripotent stem cells in this, give rise to immunocompetent B cells and pre-T cells (which are both types of lymphocytes)
B Cells (red bone marrow)
cell type: migrate directly to blood/lymph nodes
Pre-T Cells (red bone marrow)
migrate to thymus to finish maturation
Thymus
located between the sternum and aorta
Thymus
contains left and right lobes, which are divided into lobules
Lobule (thymus)
contains 2 layers: a medulla and a cortex
Cortex (of thymus)
location: pre-T cells begin maturation process; most die via apoptosis, but some migrate to medulla to continue maturation process
Medulla (of thymus)
location: T cells complete maturation to blood, lymph nodes, spleen, and other lymphatic tissue
Lymph Nodes
are often in groups, and function to filter lymph as it passes through; macrophages and lymphocytes destroy pathogens
Lymph Nodes
consist of an outer cortex, an inner cortex, and a medulla
Outer Cortex (of lymph node)
includes masses of B cells, called lymphatic nodules, that can proliferate and become antibody-producing plasma cells or memory B cells
Inner Cortex (of lymph node)
location: includes masses of T cells that can proliferate and leave lymph node
Medulla
includes masses of plasma cells (mature B cells) that have migrated from outer cortex, and can produce and release antibodies
Spleen
is located between the stomach and diaphragm, and functions to filter blood; lymphocytes and macrophages destroy pathogens; macrophages destroy damaged blood cells
Lymphatic Nodules
some of these are found within lymph nodes, others are found in mucous membranes of various organ systems
MALT (lymphatic nodules)
mucosa-associated lymphatic tissue; includes GI tract, urinary tract, reproductive tract, and respiratory tract
Immunity
is the ability of the body to ward off disease and damage; is the opposite of susceptibility; has 2 types
Innate Immunity
is present at birth, nonspecific
Adaptive Immunity
immunity type: develops after exposure to a particular pathogen, specific
Internal Defenses (innate immunity)
includes antimicrobial proteins, natural killer cells, phagocytes, inflammation, and fever
Antimicrobial Proteins
are found in blood plasma and interstitial fluid, and include interferons, transferrins, and a complement system
Interferons (INFs)
are produced by a cell that has been infected by a virus, migrate to uninfected neighboring cells, and synthesis of antiviral proteins in uninfected cells
Transferrins
inhibit some microbes by limiting the availability of iron
Complement System
assist in the process of inflammation and the immune system
Natural Killer Cells
are a type of lymphocyte, that bind to microbes and release granules that contain various toxins that can kill the microbe
Natural Killer Cells
cell type: are found in blood, spleen, lymph nodes, and red bone marrow
Phagocytes
include neutrophils and macrophages, and function to engulf microbes
Macrophages
are mature monocytes
Phagocytosis
the process of engulfing microbes
Inflammation
symptoms: redness, pain, heat, swelling, loss of functions
Inflammation
is a localized response, and functions to kill microbes
Inflammation
prevents microbes from spreading to other tissues, and prepares site for tissue repair
Inflammation (steps)
includes: vasodilation and increased permeability of capillaries, emigration of phagocytes, and tissue repair
Fever
symptoms: increased body temperature
Fever
functions to increase reaction rates of interferons and tissue repair mechanisms, and inhibits growth of some microbes
Adaptive Immunity
is a targeted response to a specific antigen in the body
Antigen (adaptive immunity)
is essentially an antibody generator; foreign substances that provoke an immune response, such as viruses, bacteria, parasites, toxins, and foreign tissue
Antigen (adaptive immunity)
typically is a protein molecule on the surface of a pathogen or parasite, and is characterized by specificity and memory
Specificity (adaptive immunity)
characteristic of adaptive immunity: targeting particular antigens; distinguishing self from non-self
Memory (adaptive immunity)
characteristic of adaptive immunity: secondary exposure to previousy encountered antigen provokes a rapid, strong response
Cell-mediated (immune response)
immune response: involves T cells; which leave lymphatic tissue, mature into helper T cells and cytotoxic T cells, and destroy pathogens directly
Cell-mediated (immune response)
immune response: targets intracellular pathogens (such as viruses, bacteria, and fungi in host cell), cancer cells, and foreign tissue
Antibody-mediated (immune response)
immune response: involves B cells; which remain in lymphatic tissue, mature into plasma cells, and release antibodies, which leave lymphatic tissues to destory pathogens
Antibody-mediated (immune response)
immune response: targets antigens in body fluids, and extracellular pathogens (in body fluids, outside cells)
Clonal Selection
upon infection by a novel antigen; only a few helper T cells, cytotoxic T cells, and B cells will have receptors for the antigen, these cells proliferate to form thousands of cells
Clonal Selection
proliferation is accompanied by differentiation into effector cells and memory cells
Effector Cells (clonal selection)
cell type: includes active helper T cells, active cytotoxic T cells, and plasma cells
Memory Cells (clonal selection)
includes: memory helper T cells, memory cytotoxic T cells, and memory B cells
Antigens
includes 2 characteristics: immunogenicity and reactivity
Immunogenicity (antigen)
is the ability to provoke an immune response; production of antibodies by B cells or proliferation of T cells
Reactivity (antigen)
is the ability to react with antibodies or the cells it provokes
Chemical Nature (antigens)
typically large molecules, most often proteins, often on the surface of cells (in plasma membrane), often only a small region (epitope) of a molecule triggers the immune response
Receptors (antigen)
antigen part: molecules in the plasma membranes of T cells and B cells that recognize specific antigens
Antigen
the incredible diversity of these on the environment is a problem, b/c each recognizes a specific epitope
Major Histocompatibility Complex (MHC) Antigens
the immune system must be able to recognize our own body's cells, occurs in the plasma membranes of somatic cells (except RBCs), every combination is unique, and are ignored by T cells and B cells
Response (to antigens)
antigen receptors allow B cells and T cells to recognize and react to foreign antigens
B Cells
cell type: recognize antigens directly; b/c they mainly target extracellular pathogens
T Cells (response to antigens)
cell type: these recognize only fragments of antigens that have been processed and presented; b/c they mainly target intracellular pathogens
Cell-Mediated Immunity
immunity type: T cell activated when presented with an antigen, activated T cell proliferates and differentiates to produce many effector cells (clones), which include helper T cells and cytotoxic T cells
Cytotoxic T Cells
target intracellular pathogens; leave lymphatic tissue, bind to infected cells, and destroy pathogens via 2 mechanisms
Antibody-Mediated Immunity
immunity type: B cell activated when presented with an antigen, activated B cell proliferates and differentiates to produce many effector cells (clones), which include plasma cells
Antibodies
have immunoglobin proteins, most are composed of 4 polypeptide chains, and have 2 regions: a constant region and variable regions
Antibodies
functions: to recognize the epitope of the antigen that triggered that antibody's production, and to disable pathogens via 5 main mechanisms
Immunological Memory
immune system remembers specific antigens that have triggered an immune response in the past; memory B and T cells activated by first exposure to antigen, and the antibodies are circulating in blood
Immunological Memory
upon first exposure, only a few immunological cells recognize the foreign antigen, so proliferation is slow
Immunological Memory
upon second exposure, thousands of immunological cells recognize the foreign antigen, so proliferation is rapid (thus allowing immunity to antigens develop)