The Lymphatic SystemKUFRE ROBERTSIGNACIO RODRIGUEZBRANDON SMITH

The Lymphatic System

The Lymphatic System consists of lymphatic vessels and the lymphatic organs, and it has three main functions that contribute to homeostasis:1. Fluid Balance- The system takes up excess tissue fluid and returns

it to the bloodstream.2. Fat Absorption- The system absorbs fats from the digestive tract,

then transports them to the bloodstream.3. Defense- The system aids in the defense of the human body

against disease through the use of white blood cells.

Lymphatic Vessels

Lymphatic Vessels form a one-way system that begins with lymphatic capillaries.

Lymphatic Capillaries- Tiny, close ended vessels whose walls consist of simple squamous epithelium. They take up excess tissue fluid, which become lymph, the fluid inside lymphatic vessels.

Capillaries join to form Vessels that merge before entering the thoracic duct or right lymphatic duct.

Thoracic Duct- Returns lymph collected from the left side of the body into the left subclavian vein.

Right Lymphatic Duct- Returns lymph from the right side of the body into the right subclavian vein.

Lymphatic Vessels (Cont’d.)

The structure of larger lymphatic vessels is similar to cardiovascular veins.

► The movement of lymph within capillaries is dependent of muscle contraction. Said lymph is kept from flowing backward by one-way valves in the vessels.

► Edema is a result of the lymphatic system failing to properly collect and return excessive tissue fluid to the bloodstream.

Organs, Tissues, and Cells of the Immune System

Immune System- Keeps the human body healthy; consists of a network of lymphatic organs, tissues, and cells, as well as products of said cells, including:• Antibodies• Regulatory agents

► Immunity- The ability to react to antigens so that the body remains free of disease• Disease results from a failure of homeostasis.

Organs, Tissues, and Cells of the Immune System (Cont’d.)

Lymphatic (lymphoid) organs- Contain large numbers of lymphocytes, a type of white blood cell (WBC) that plays a pivotal role in immunity. Primary Lymphatic Organs are red bone marrow and the thymus

gland. Red Bone Marrow- Site of stem cells that divide and produce blood cells,

some of which become different types of blood cells, like: Neutrophils, eosinophils, basophils, lymphocytes, and monocytes. Lymphocytes differentiate into B lymphocytes (which mature in the marrow) and

T lymphocytes (which mature in the thymus).

Organs, Tissues, and Cells of the Immune System (Cont’d. 2)

Thymus Gland- Located in the thoracic cavity between the trachea and the sternum, superior to the heart. Connective tissue divides the thymus into lymphocyte-filled lobules. The gland produces hormones, such as thymosin, believed to aid in the

maturation of T lymphocytes. The Thymus is critical to immunity, and without one:

The body fails to reject foreign tissue Blood lymphocyte levels are drastically reduced The body’s response to most antigens is lacking or nonexistent.

Organs, Tissues, and Cells of the Immune System (Cont’d. 3)

Secondary Lymphatic Organs are places where lymphocytes encounter and bind antigens. These places are:

Spleen- The largest lymphatic organ; connective tissue splits the spleen into compartments, each of which contain ‘white pulp’ and ‘red pulp’.

White Pulp- Contains a concentration of lymphocytes. Red Pulp- Involved in filtering blood.

Lymph nodes- Small, ovoid structures that occur along lymphatic vessels. The nodes are compartmentalized; each compartment has a node filled with B lymphocytes,

along with a sinus that increases in size toward the center of the node. The lymph is filtered by macrophages( phagocytic white blood cells), which engulf

pathogens and debris. T lymphocytes, present in the sinus(s) fight infections and attack cancer cells. Physicians look for the presence of swollen lymph nodes as evidence that the body is

fighting infection.

Organs, Tissues, and Cells of the Immune System (Cont’d. 4)

Lymphatic Nodules- Concentrations of lymphatic tissue not surrounded by a capsule Tonsils are lymphatic nodules located in the posterior pharynx. They operate

like lymph nodes, but are the first to encounter pathogens and antigens that enter the body through nose or mouth.

Phyaryngeal tonsil (adenoids)- Located in the nasopharynx. Lingual tonsils- Located at the base of the tongue. Palatine tonsils- Located in the posterior oral cavity.

Peyer Patches- Located in the intestinal wall and the walls of the appendix.

Sec. 3 Nonspecific & specific Defenses.• Nonspecific Defenses:

• Barriers to Entry: Built in barriers, both physical and chemical that help to prevent infection by microbes.

• Inflammatory Reaction: Happens whenever tissue is either damaged chemically or physically or by pathogens.

• Natural Cell (NK) killers: Kill virus infected cells and tumor cells by cell-to-cell contact.

• Protective Proteins (The complement system): These proteins “complement” certain immune responses, which accounts for their name.

Specific Defenses

Specific defenses respond to antigens, which are molecules the immune system recognizes to be foreign.

-It is said that the immune system is able to distinguish “self” from “non self”. Immunity is primarily the result of the action of B lymphocytes

and T lymphocytes.

B Cells and Antibody-Mediated Immunity

When a B cell encounters a specific antigen, it is ordered to divide many times, resulting in plasma cells.

A plasma cell is a mature B cell that mass produces anti-bodies for that specific antigen.

-The clonal selection theory states that the antigen “selects” one particular lymphocyte to reproduce multiple copies of itself. If the antigen enters the system again, memory B cells quickly

divide and give rise to more lymphocytes capable of quickly producing antibodies.

B Cells and Antibody-Mediated Immunity Cont.

Apoptosis: is the process of programmed cell death involving a cascade of specific cellular events leading to the death and destruction of the cell.

-It is important that this happens otherwise, the body could mistakenly destroy body cells in an autoimmune response. Defense by B cells is called antibody-mediated immunity also

called hormonal immunity.

Structure and Function of antibodies

The basic unit that composes antibody molecules is a Y-shaped protein molecule with two arms.

- Each arm has a “heavy” (long) and “light” (short) polypeptide chain (shown below.)

Classes of antibodies

Five different types:1.IgG2.IgM3.IgA4.IgD5.IgE

(look in the book, when I tried to copy the chart from the book it only showed the outline, not the text) Pg. 285 Table 13.1 Antibodies.

Section 13.4 Induced Immunity

Active immunity: When the individual alone produces antibodies against an antigen.

Passive immunity: is then an individual receives prepared antibodies from another person.

Active Immunity

Immunization: Includes vaccines, substances that contain an antigen to which the immune system responds.

Allergies

Allergies are hypersensitivities to substances as pollen or animal hair that ordinarily would do no harm to the body.

-This response to the antigens called allergens usually includes some degree of tissue damage.

IgE-Mediated Allergic Response

Often referred to as an immediate allergic response because it can occur within seconds of contacts with an antigen.

- An example of this would be when pollen gets into your nose and your eyes start to get watery also causing a runny nose

called a hey fever.-Anaphylactic shock: Occurs when the antigen enters the bloodstream. This response is characterized by a sudden life-threatening drop in blood pressure due to blood vessel

dilation.

T-Cell Mediated Allergic Response

Often referred to delayed allergic response because it takes longer than the IgE antigens to develop.

-Example: Skin being tested for tuberculosis (TB). When the test result is positive, the tissue where the injected antigen becomes red and hardens.

Autoimmune Disease

When the body mistakenly attacks the body’s own calls as if they bear foreign antigens. What exactly causes autoimmune diseases is get to be discovered.

- Some autoimmune diseases are:1.Myasthenia gravis2.Multiple sclerosis (MS)3.Systemic lupus erythematosus4. Rheumatoid arthritis

Immune Deficiency

When a person has an immune deficiency, the immune system is unable to protect the body against disease. (AIDS…)

Lastly, Severe combined immunodeficiency disease (SICD), a generic disorder, both antibody and cell-mediated immunity are lacking or inadequate.

- Without treatment, one could die from the common cold.

Section. 5/6

Effects Of Aging• WITH ADVANCING AGE, PEOPLE BECOME MORE VULNERABLE TO ALL TYPES OF INFECTIONS AND

DISORDERS BECAUSE THE IMMUNE SYSTEM EXHIBITS LOWER LEVELS OF FUNCTION. • THE THYMUS GLAND DEGENERATES. WHEN IT REACHES ITS MAXIMUM SIZE IN EARLY CHILDHOOD, IT

BEGINS TO SHRINK AFTER PUBERTY AND HAS VIRTUALLY DISAPPEARED BY OLD AGE.• AS THE GLAND DECREASES SO DOES THE NUMBER OF T CELLS. THE REMAINING T CELLS DO NOT

RESPOND TO FOREIGN ANTIGENS, THIS PROCESS INCREASES THE CHANCE OF HAVING CANCER INCREASED WITH AGE.

• THE B CELLS SOMETIMES FAIL TO FORM CLONES AMONGST THE ELDERLY, OR WHEN THEY DO FORM THE CLONES THE ANTIBODIES RELEASED MAY NOT FUNCTION WELL. WHICH CAUSES INFECTIONS TO BE MORE COMMON IN THE ELDERLY.

• THE ANTIBODIES ARE MORE LIKELY TO ATTACK THE BODY’S OWN TISSUES WHICH INCREASES THE INCIDENCE OF AUTOIMMUNE DISEASES.

• DUE TO THE OVERALL LOW LEVEL OF THE IMMUNE RESPONSE, IT IS BENEFICIAL THAT THE ELDERLY GET VACCINATION EACH YEAR.

HomeostasisTHE LYMPHATIC SYSTEM HELPS THE DIGESTIVE SYSTEM BY ABSORBING FATS. IN THE PROCESS OF ABSORBING DIETARY FATS ,LACTEALS ALSO ABSORB FAT SOLUBLE VITAMINS.THE LYMPHATIC SYSTEM ALSO ASSIST THE CARDIOVASCULAR SYSTEM BY ABSORBING EXCESS TISSUE FLUID, IT RETURNS THE EXCESS TISSUE FLUID AS LYMPH TO CARDIOVASCULAR VEINS IN THE THORAX, WITHOUT THIS PROCESS IT WOULD BE DIFFICULT FOR THE BODY TO MAINTAIN THE BLOOD VOLUME AND PRESSURE NEEDED FOR THE CAPILLARY EXCHANGE.

Lymphatic System