THE LYMPHATIC SYSTEM

Capaian pembelajaran :

Setelah mengikuti perkuliahan mahasiswa diharapkan mampu :

1. Menjelaskan organ sistem limfatik2. Menjelaskan fungsi sistem limfatik3. Menjelaskan mekanisme kerja sistem

limfatik

The Lymphatic System

Consists of two semi-independent parts Lymphatic vessels

which contains lymph

Lymphoid tissues and organs

Functions :

Lymphatic System which consists of vessels and organs plays two vital roles in our lives:

1) The vessels essentially maintain interstitial fluid levels by carrying excess fluids , any plasma proteins, back into the CVS.

2) The organs, house critical immune cells such as lymphocytes which carryout our body defense against infection and disease

Relationship of lymphatic system and cardiovascular system

Relationship of lymphatic system and cardiovascular system

Lymph

Lymph excess tissue fluid carried by lymphatic vessels

Composition of Lymph Lymph is usually a clear, colorless fluid, similar to

blood plasma but low is protein Its composition varies from place to place; after a

meal, for example, lymph draining from the small intestine, takes on a milky appearance, due to lipid content.

Lymph may contain macrophages, viruses, bacteria, cellular debris and even traveling cancer cells.

Lymphatic Vessels

Lymph Capillaries Walls overlap to form flap-like minivalves Fluid leaks into lymph capillaries Capillaries are anchored to connective

tissue by filaments Higher pressure on the inside closes

minivalves

What Type of Vessels Make up the Lymphatic System? Thin-walled and are analogous to veins. Small lymphatics are similar to capillaries

only more porous; Larger vessels are called collecting vessels: both have valves.

2 large Ducts: Right LYMPHATIC DUCT and THORACIC DUCT (BOTH EMPTY INTO THE RT AND LT SUBCLAVIAN VEINS)

Lymph flows only TO THE HEART (ONE WAY). This is a low-pressure, pumpless

system. Lymph moves via skeletal muscles and pressure changes in thorax during breathing only.

Lymphatic Organs:

A Lymph Node. Spleen Thymus Gland Tonsils MALT Peyer’s patch

MALT

The collection of lymphoid tissues linked with the digestive system is called the mucosa-associated lymphoid tissue (MALT).

Clusters of lymphoid nodules deep to the epithelial lining of the intestine are known as aggregate lymphoid nodules, or Peyer’s patches

Tonsils

Large nodules in the walls of the pharynx

Most people have five tonsils:

1. A single pharyngeal tonsil, often called the adenoids.

2, 3. A pair of palatine tonsils

4, 5. A pair of lingual tonsils.

The Thymus

The thymus is located in the mediastinum, generally just posterior to the sternum.

In newborn infants and young children, the thymus is relatively large.

The thymus reaches its greatest size (relative to body size) in the first year or two after birth. The thymus reaches its maximum absolute size just before puberty. After pubertyinvolution

The thymus produces Thymosin that promotes the development and maturation of lymphocytes

Lymph Nodes

Lymph Nodes take the germ-filled lymph and Filter lymph before it is returned to the blood

Defense cells within lymph nodes Macrophages – engulf and destroy foreign

substances Lymphocytes – provide immune response to

antigens

Where are these lymph nodes?

Lymph Node Structure

Most are kidney-shaped, less than 1 inch long

Cortex Outer part Contains follicles – collections of

lymphocytes Medulla

Inner part Contains phagocytic macrophages

Anatomy of a Lymph Node

Fluid enters afferent vessels

Exists efferent vessels

Germinal center of follicle – These enlarge during time of plasma cell production (B Cells)

Medulla- Phagocytes are located here

SPLEEN Filters blood of bacteria, viruses and

other debris Destroys worn out blood cells. It then

returns (or recycles) some of the breakdown products of RBCs to the liver.

Another function: Stores platelets and acts as a blood reservoir.

Lymphocytes are produced; RBCs also made in fetus only.

Lymphatic system and Body’s Defense System

Two general defenses:

Nonspecific defenses include physical barriers, phagocytic cells, immunological surveillance, interferons, complement, inflammation, and fever.

Specific defenses include B cells, T cells, Antibody

Lymphocytes

Lymphocytes account for 20–30 percent of the circulating white blood cell population.

1) T (thymus-dependent) cells, (2) B (bone marrow–derived) cells (3) NK (natural killer) cells

T cells

Approximately 80 percent of circulating lymphocytes

Many types of T cells: Cytotoxic T cells, which attack foreign cells

or body cells infected by viruses. Helper T cells, which stimulate the activation

and function of both T cells and B cells. Suppressor T cells, which inhibit the

activation and function of both T cells and B cells.

B cells

B Cells B cells account for 10–15 percent of circulating lymphocytes.

When stimulated, B cells can differentiate into plasma cells.

Plasma cells are responsible for the production and secretion of antibodies, soluble proteins that are also known as immunoglobulins

Antibody Classes

By amino acid sequences of C region of antibody

IgA: monomer in plasma; dimer in mucus, saliva, tears, milk, intestinal secretions, prevents adherence to epithelia

IgD: monomer; B cell membrane antigen receptor IgE: monomer; on mast cells; stimulates release of

histamines, attracts eosinophils; immediate hypersensitivity reactions

IgG: monomer; 80% circulating, crosses placenta to fetus, 2 immune response, complement fixation

IgM: pentamer, 10% in plasma, 1 immune response, agglutination, complement fixation

How Do Antibodies Work?

NK cells

The remaining 5–10 percent of circulating lymphocytes are NK cells, also known as large granular lymphocytes.

These lymphocytes attack foreign cells, normal cells infected with viruses, and cancer cells that appear in normal tissues.

Their continuous policing of peripheral tissues has been called immunological surveillance.

Vaccines Vaccine development is based on acquired

immunity. 2 BASIC TYPES:

1. TO CONFER ACTIVE IMMUNITY :

a. Weakened microbes(measles, mumps, rubella)

b. Killed pathogens that still retain surface antigens so they can stimulated antibody production

2. PASSIVE IMMUNITY: Give just the antibodies. In this case a person has already been exposed to pathogen; needs antibodies fast.

Active Immunity

Your B cells encounter antigens and produce antibodies

Active immunity can be naturally or artificially acquired

Figure 12.14

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