Lymphatic System and Immunity

Discuss the function of anchoring filaments that surround lymphatic capillaries.

1. are microscopic closed ended tubes that extend into interstitial spaces; 2. receive lymph through their thin walls; 3. are associated with anchoring filaments, which serve an important function during edema (discussed later); 4. are located throughout the body, except in: a. avascular tissues; b. CNS; c. splenic pulp; d. bone marrow. 5. include lacteals that are lymphatic capillaries within villi of the small intestine.

List the functions of the lymphatic system.

1. returns small leaked plasma proteins back to the blood stream. 2. transports foreign particles to the lymph nodes. 3. transports lipids and lipid-soluble vitamins absorbed in GI tract to bloodstream.

3. Name the major types of cells of the lymphatic system and state their functions.

1.Natural killer (NK) cells are large lymphocytes that attack and destroy bacteria, transplanted tissues, and host cells (cells of one's own body) that have either become infected with viruses or turned cancerous. They are responsible for a mode of defense, discussed later, called immune surveillance. 2.T lymphocytes (T cells) are lymphocytes that mature in the thymus and later depend on thymic hormones; the T stands for thymus-dependent. There are several subclasses of T cells that will be introduced later. 3.B lymphocytes (B cells) are lymphocytes that differentiate into plasma cells—connective tissue cells that secrete antibodies. They are named for an organ in chickens (the bursa of Fabricius1) in which they were first discovered. However, you may find it more helpful to think of B for bone marrow, the site where these cells mature in humans. 4.Macrophages are very large, avidly phagocytotic cells of the connective tissues. They develop from monocytes that have emigrated from the bloodstream. They phagocytize tissue debris, dead neutrophils, bacteria, and other foreign matter (fig. 21.7). They also process foreign matter and display antigenic fragments of it to certain T cells, thus alerting the immune system to the presence of an enemy. Macrophages and other cells that do this are collectively called antigen-presenting cells (APCs). 5.Dendritic cells are branched, mobile APCs found in the epidermis, mucous membranes, and lymphatic organs. (In the skin, they are often called Langerhans2 cells.) They play an important role in alerting the immune system to pathogens that have breached the body surfaces. They engulf foreign matter by receptor-mediated endocytosis rather than phagocytosis, but otherwise function like macrophages. After internalizing an antigen, they migrate to a nearby lymph node and activate an immune reaction to it. 6.Reticular cells are branched, stationary APCs that contribute to the connective tissue framework (stroma) of the lymphatic organs (see fig. 21.10). (They should not be confused with reticular fibers, which are fine, branched collagen fibers common in lymphatic organs.)

Identify the body's three lines of defense against pathogens.

1.The first line of defense consists of external barriers, notably the skin and mucous membranes, which are impenetrable to most of the pathogens that daily assault us. 2.The second line of defense consists of several nonspecific defense mechanisms against pathogens that break through the skin or mucous membranes. These defenses include leukocytes and macrophages, antimicrobial proteins, immune surveillance, inflammation, and fever. 3.The third line of defense is the immune system, which not only defeats a pathogen but leaves the body with a "memory" of it, enabling one to defeat it so quickly in future encounters that the pathogen causes no illness.

Describe the process of inflammation and explain what accounts for its cardinal signs; and

A complex of tissue responses to trauma or infection serving to ward off a pathogen and promote tissue repair; recognized by the cardinal signs of redness, heat, swelling, pain, and compromised function.

Describe the defensive functions of Eosinophil's.

A granulocyte with a large, often bilobed nucleus and coarse cytoplasmic granules that stain with eosin; phagocytizes antigen-antibody complexes, allergens, and inflammatory chemicals and secretes enzymes that combat parasitic infections.

Describe the defensive functions of Basophil's.

A granulocyte with coarse cytoplasmic granules that produces heparin, histamine, and other chemicals involved in inflammation.

Describe the defensive functions of Neutrophil's.

A granulocyte, usually with a multilobed nucleus, that serves especially to destroy bacteria by means of phagocytosis, intracellular digestion, and secretion of bactericidal chemicals.

Describe the defensive functions of Lymphocytes.

A relatively small agranulocyte with numerous types and roles in nonspecific defense, humoral immunity, and cellular immunity.

Describe the defensive functions of Monocytes.

An agranulocyte specialized to migrate into the tissues and transform into a macrophage.

Describe the body's other non specific defenses.

Antimicrobial -Interferon's -Complement System -Transferrin Natural Killer Cells Phagocytosis Inflammation Fever

Describe the body's other nonspecific defenses.

Cells, Tissue, Organ, System, and Body General defensive mechanisms effective on a wide range of pathogens (disease producing microbes)

Explain how lymph forms and path of return to the bloodstream.

Lymph Formation 1. As protein concentration in interstitial spaces increases, its pressure increases. 2. Increasing pressure forces tissue fluid into lymphatic capillaries. 3. This fluid is now called lymph. 4. Lymph formation prevents accumulation of excess tissue fluid (i.e. prevents edema). Lymph Flow a. Lymph is under low pressure and may not flow readily without aid from external forces (similar to venous return). o The squeezing action of skeletal muscles aids movement. o The low pressure in the thoracic cavity created by breathing movements, moves lymph up from abdominal to thoracic region. o Recall the presence of one-way valves. 2. Obstruction of lymph movement a. Any condition that interferes with the flow of lymph results in edema. o Edema = accumulation of excess interstitial fluid leading to swelling of tissues. b. Tissue swelling pulls on anchoring filaments making openings between cells even larger so that more fluid can move into the lymphatic capillary (i.e. reducing swelling). See Fig 16.8, p. 611. c. The surgical removal of lymph nodes causes obstruction and results in edema (i.e. accompanying mastectomy).

Trace the flow of lymph from interstitial tissues to the bloodstream.

Lymphatic pathways begin as lymphatic capillaries, which come together to form afferent lymphatic vessels, which lead to lymph nodes. The vessels that leave the lymph nodes are called efferent lymphatic vessels, which come together to form lymphatic trunks, which lead to two collecting ducts, which finally join the subclavian veins, where the lymph enters the cardiovascular system.

Name and describe the types of lymphatic tissue.

Lymphatic tissue occurs in the body in various forms. 1. When it is not encapsulated, it is called diffuse lymphatic tissue (i.e. found in submucosa of mucous lining). 2. When it is aggregated into a solitary, oval-shaped mass, it is called a lymphatic nodule (i.e. tonsils, and recall the lymphatic nodule in the small intestine model). 3. Primary lymphatic organs are the sites of production of immunocompetent cells, B cells and T cells. These cells can carry out an immune response. a. bone marrow (red) b. thymus. 4. Secondary lymphatic organs are the sites where most immune responses occur. a. lymph nodes b. spleen.

Describe the basic structure and function of the red bone marrow, thymus, lymph nodes, tonsils, and spleen.

Red bone marrow is a soft, loosely organized, highly vascular material, separated from osseous tissue by the endosteum of the bone. It produces all classes of formed elements of the blood; its red color comes from the abundance of erythrocytes. Thymus The thymus is a member of the endocrine, lymphatic, and immune systems. It houses developing lymphocytes and secretes hormones that regulate their later activity. Lymph Node A small organ found along the course of a lymphatic vessel that filters the lymph and contains lymphocytes and macrophages, which respond to antigens in the lymph. Tonsils The tonsils are patches of lymphatic tissue located at the entrance to the pharynx, where they guard against ingested and inhaled pathogens. Each is covered by an epithelium and has deep pits called tonsillar crypts lined by lymphatic nodules Spleen The spleen is the body's largest lymphatic organ, measuring up to 12 cm long and weighing up to 160 g. Its blood capillaries are very permeable; they allow RBCs to leave the bloodstream, accumulate in the sinuses of the red pulp, and reenter the bloodstream later. The spleen is an "erythrocyte graveyard"—old, fragile RBCs rupture as they squeeze through the capillary walls into the sinuses. Macrophages phagocytize their remains, just as they dispose of blood-borne bacteria and other cellular debris. The spleen produces blood cells in the fetus and can resume this role in adults in the event of extreme anemia. Lymphocytes and macrophages of the white pulp monitor the blood for foreign antigens, much like the lymph nodes do the lymph. The spleen also helps to stabilize blood volume by transferring excess plasma from the bloodstream into the lymphatic system.

Name the organs that compose the lymphatic system and give three general functions performed by this system.

The lymphatic system is closely associated with the cardiovascular system. The primary organs of the lymphatic system are the bone marrow and thymus gland, and the secondary lymphatic organs include the lymph nodes and spleen. These organs work together to transport excess tissue (interstitial) fluid to the blood stream, transport dietary fat, and help defend the body against disease causing agents.

Define Immunity

The state of being protected from an infectious disease, usually by having been exposed to the infectious agent or a vaccine; human immunity has two major components: innate and adaptive. Innate immunity is nonspecific, has no memory, and consists of anatomic barriers, defensive cells, and chemicals. Adaptive immunity is specific, has memory, and may involve antibodies