A&P 2: Chapter 22

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Anatomy & Physiology 2 Lamar University Lecture-Armacost

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


are specialized lymphatic capillaries in the small intestine


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


located between the sternum and aorta


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


includes masses of plasma cells (mature B cells) that have migrated from outer cortex, and can produce and release antibodies


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


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


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


include neutrophils and macrophages, and function to engulf microbes


are mature monocytes


the process of engulfing microbes


symptoms: redness, pain, heat, swelling, loss of functions


is a localized response, and functions to kill microbes


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


symptoms: increased body temperature


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


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


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


have immunoglobin proteins, most are composed of 4 polypeptide chains, and have 2 regions: a constant region and variable regions


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)

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