淋巴系统与免疫

b. Lymphatic Vessels
• Lymphatic vessels are spread out throughout the body except in the CNS (Fig 22.1)
• They originate from within lymphocyte producing organs and empty into the thoracic duct.
• They contain many lymphatic nodes and nodules.
• Like blood vessels, they have small vessels called lymphatic capillaries which lay close to the blood capillaries.
• Thymus Gland – On top of the heart – T-cells mature here – Becomes large during the first or second year. – Intrinsic size is largest at puberty and then decreases. – Produces lymphocytes which then move to other lymphatic tissues. – Blood-thymic barrier - reticular cells wrap around capillaries and prevent large molecules from entering the cortex of the thymus.
• Kill bacteria: lysozyme and sebum mucus
• Others: histamine and kinins by vasodilation; interferon production, etc..
Innate Immunity
a. Mechanical Mechanism
• Physical barriers, such as the skin and membranes
b. Chemical Mediators (Table 22.1)
• Molecules which contribute to develop immunity.
• Specificity. Innate immunity can act against bacteria in genera. (no memory)
• Memory. Adaptive immunity can distinguish among different kinds of bacteria and generally get more sensitive with each new encounter.
immune response or immunity.
• Organization and Functions of the Lymphatic System
• In the lymphatic system there are:
– Lymphatic fluid, lymph, that contains lymphocytes
• Lymph soluble fluid will be picked up through the capillaries and pushed back to larger truck.
• They even have valves to control the flow of lymph through very low pressure of fluid.
• When these foreign bodies are capable of living in the human body and are harmful, they are called pathogens.
• Plasma contains antibodies against cells other than its own. These antibodies are formed when the infants are about three months old. Recall when the blood types were formed.
• Tonsils – Large groups of lymph nodules and diffuse lymphatic tissue located in the oral cavity (Fig. 22.3) – Protection against bacteria, etc.. In the nose and mouth. – Three types of tonsils: pharyngeal, palatine, and lingual – Enlarged pharyngeal tonsil is called adenoid.
• The Spleen – Upper and posterior part of the abdominal cavity. – Largest of the lymphatic tissue, 160g. (Fig. 22.5) – Contains two types of lymphatic tissue: white pulp (arterial supply) and red pulp (venous supply). – The spleen detects and responds to foreign substances in the blood, destroys worn-out RBC’s and acts as a blood reservoir.
• Lymph Nodes ( Fig. 22.1 and Fig. 22.4) – Found throughout the body except in the brain. – They are encapsulation of lymphocytes, macrophages and reticular cells with blood vessels – 1-25mm in diameter and are subdivided into two regions called, a medulla and cortex. – Within the cortex germinal centers are found. This is where lymphocyte division takes place. – Act as sieve and removal of 99% of antigens while reactivating T- cells and B-cells.
• Thus, there is the lymphatic system in the body to identify and destroy foreign bodies. (by forming antibodies)
• But, how do they distinguish our own from the others? • When the reaction is against each specific foreign body, it is called
• Packed with lymphocytes. • Flexible in size depending upon the number of
lymphocytes • Spread in loose C.T. of the digestive, respiratory and
urinary systems. Larger patches in intestinal system call Peyer’s patches. • In lymph nodes they are called follicles, there they contain a germinal center, where lymphocytes divide. • Though filled with lymphocytes, lymphoid nodules could be infected: tonsillitis, appendicitis.
• The lymph system has three major functions:
– 1. Fluid Balance. Circulating blood release about 30 L of fluid into interstitial space each day. Of the 27 L are returned to the circulation. The remaining 3L will enter the lymphatic system as lymph. The lymph passes through the lymphatic system and enter back to the blood vessels. In addition to water, lymph contains substances as in plasma and substances extracted from cells.
• Immunity
• How the human body defends itself against damage from foreign substances such as microorganisms and harmful chemical as toxins.
• Innate (non-specific) and adaptive (specific) immunity. These two types are distinguished by the way they respond to specific stimulations and how they memorize the events.
Chapter 22
Anatomy & Physiology
Fifth Edition
Seeley/Stephens/Tate
(c) The McGraw-Hill Companies, Inc.
The Lymphatic System and Immunity
• The human body recognizes anything other than its own as an invader.
– 2. Fat Absorption. Fats and other substances are absorbed from the digestive tract and carried through the lymphatic system.
– 3. Defense. Iells, T-cells)
– Vessels that transport lymph
– And sites where large contents of lymphocytes are held: lymph nodes, spleen, and thymus.
a. Functions of the lymphatic system
c. Lymphatic Organs
– Diffuse lymphatic tissue
• Dispersed lymphocytes, macrophages and other cells. No clear boundaries. (Fig. 22.2)
– Lymphoid Nodules