Chapter 13 The Lymphatic System and Immunity. Elsevier items and derived items © 2008, 2004 by...

Chapter 13Chapter 13The Lymphatic System and The Lymphatic System and

ImmunityImmunity

Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 2

THE LYMPHATIC SYSTEM (FIGURE 13-1)THE LYMPHATIC SYSTEM (FIGURE 13-1)

Lymph—fluid in the tissue spaces that carries protein molecules Lymph—fluid in the tissue spaces that carries protein molecules and other substances back to the bloodand other substances back to the blood

Lymphatic vessels—permit only one-way movement of lymphLymphatic vessels—permit only one-way movement of lymph Lymphatic capillaries—tiny blind-ended tubes distributed in tissue Lymphatic capillaries—tiny blind-ended tubes distributed in tissue

spaces (Figure 13-2)spaces (Figure 13-2)• Microscopic in sizeMicroscopic in size• Sheets consisting of one cell layer of simple squamous epitheliumSheets consisting of one cell layer of simple squamous epithelium• Poor “fit” between adjacent cells results in porous wallsPoor “fit” between adjacent cells results in porous walls• Called Called lactealslacteals in the intestinal wall (fat transportation from food to in the intestinal wall (fat transportation from food to

bloodstream)bloodstream) Right lymphatic duct (Figure 13-3)Right lymphatic duct (Figure 13-3)

• Drains lymph from the right upper extremity and right side of head, neck, Drains lymph from the right upper extremity and right side of head, neck, and upper torsoand upper torso

Thoracic ductThoracic duct• Largest lymphatic vesselLargest lymphatic vessel• Has an enlarged pouch along its course, called Has an enlarged pouch along its course, called cisterna chylicisterna chyli• Drains lymph from about three-fourths of the body (Figure 13-3)Drains lymph from about three-fourths of the body (Figure 13-3)


THE LYMPHATIC SYSTEMTHE LYMPHATIC SYSTEM

Lymph nodesLymph nodes Filter lymph (Figure 13-4)Filter lymph (Figure 13-4) Located in clusters along the pathway of Located in clusters along the pathway of

lymphatic vessels (Figures 13-1, 13-5, and 13-lymphatic vessels (Figures 13-1, 13-5, and 13-6)6)

Functions include defense and WBC formationFunctions include defense and WBC formation Flow of lymph: to node via several afferent Flow of lymph: to node via several afferent

lymph vessels and drained from node by a lymph vessels and drained from node by a single efferent lymph vesselsingle efferent lymph vessel



ThymusThymus Lymphoid tissue organ located in mediastinumLymphoid tissue organ located in mediastinum Total weight of 35 to 40 g—a little more than Total weight of 35 to 40 g—a little more than

an ouncean ounce Plays a vital and central role in immunityPlays a vital and central role in immunity Produces T-lymphocytes, or T cellsProduces T-lymphocytes, or T cells Secretes hormones called Secretes hormones called thymosinsthymosins Lymphoid tissue is largely replaced by fat in Lymphoid tissue is largely replaced by fat in

the process called the process called involutioninvolution



Tonsils (Figure 13-7)Tonsils (Figure 13-7) Composed of three masses of lymphoid tissue Composed of three masses of lymphoid tissue

around the openings of the mouth and throataround the openings of the mouth and throat• Palatine tonsils (“the tonsils”)Palatine tonsils (“the tonsils”)• Pharyngeal tonsils (also known as Pharyngeal tonsils (also known as adenoidsadenoids))• Lingual tonsilsLingual tonsils

Subject to chronic infectionSubject to chronic infection Enlargement of pharyngeal tonsils may impair Enlargement of pharyngeal tonsils may impair

breathingbreathing



SpleenSpleen Largest lymphoid organ in bodyLargest lymphoid organ in body Located in upper left quadrant of abdomenLocated in upper left quadrant of abdomen Often injured by trauma to abdomenOften injured by trauma to abdomen Surgical removal called Surgical removal called splenectomysplenectomy Functions include phagocytosis of bacteria and Functions include phagocytosis of bacteria and

old RBCs; acts as a blood reservoirold RBCs; acts as a blood reservoir


THE IMMUNE SYSTEM THE IMMUNE SYSTEM (TABLE 13-1)(TABLE 13-1)

Protects body from pathological bacteria, foreign Protects body from pathological bacteria, foreign tissue cells, and cancerous cellstissue cells, and cancerous cells

Made up of specialized cells and moleculesMade up of specialized cells and molecules Nonspecific immunityNonspecific immunity

Also called Also called innate immunityinnate immunity because it does not require because it does not require prior exposure to an antigenprior exposure to an antigen

Skin—mechanical barrier to bacteria and other harmful Skin—mechanical barrier to bacteria and other harmful agentsagents

Tears and mucus—wash eyes and trap and kill bacteriaTears and mucus—wash eyes and trap and kill bacteria Inflammation—attracts immune cells to site of injury, Inflammation—attracts immune cells to site of injury,

increases local blood flow, increases vascular increases local blood flow, increases vascular permeability; promotes movement of WBCs to site of permeability; promotes movement of WBCs to site of injury or infection (Figure 13-8)injury or infection (Figure 13-8)


THE IMMUNE SYSTEMTHE IMMUNE SYSTEM

Specific immunitySpecific immunity Also called Also called adaptive immunityadaptive immunity because of the ability of because of the ability of

the body to recognize, respond to, and remember the body to recognize, respond to, and remember harmful substances or bacteriaharmful substances or bacteria

Types of specific immunityTypes of specific immunity• Natural immunity—exposure to causative agent is not Natural immunity—exposure to causative agent is not

deliberatedeliberate Active—active disease produces immunityActive—active disease produces immunity Passive—immunity passes from mother to fetus through Passive—immunity passes from mother to fetus through

placenta or from mother to child through mother’s milkplacenta or from mother to child through mother’s milk• Artificial immunity—exposure to causative agent is Artificial immunity—exposure to causative agent is

deliberatedeliberate Active—vaccination results in immunityActive—vaccination results in immunity Passive—protective material developed in another Passive—protective material developed in another

individual’s immune system and given to previously individual’s immune system and given to previously nonimmune individualnonimmune individual


IMMUNE SYSTEM MOLECULESIMMUNE SYSTEM MOLECULES

AntibodiesAntibodies Protein compounds with specific combining sitesProtein compounds with specific combining sites Combining sites attach antibodies to specific antigens Combining sites attach antibodies to specific antigens

(foreign proteins), forming an antigen-antibody complex(foreign proteins), forming an antigen-antibody complex—called —called humoral,humoral, or or antibody-mediated, immunityantibody-mediated, immunity (Figure 13-9)(Figure 13-9)

Antigen-antibody complexes may:Antigen-antibody complexes may:• Neutralize toxinsNeutralize toxins

• Clump or agglutinate enemy cellsClump or agglutinate enemy cells

• Promote phagocytosisPromote phagocytosis


IMMUNE SYSTEM MOLECULESIMMUNE SYSTEM MOLECULES

Complement proteinsComplement proteins Group of proteins normally present in blood in inactive Group of proteins normally present in blood in inactive

statestate Complement cascadeComplement cascade

• Important mechanism of action for antibodiesImportant mechanism of action for antibodies

• Causes cell lysis by permitting entry of water through a Causes cell lysis by permitting entry of water through a defect created in the plasma membrane (Figure 13-10)defect created in the plasma membrane (Figure 13-10)

Also perform other functions (Also perform other functions (examples:examples: attracting attracting immune cells to a site of infection, activating immune immune cells to a site of infection, activating immune cells, marking foreign cells for destruction, increasing cells, marking foreign cells for destruction, increasing permeability of blood vessels)permeability of blood vessels)


IMMUNE SYSTEM CELLSIMMUNE SYSTEM CELLS

Phagocytes—ingest and destroy foreign Phagocytes—ingest and destroy foreign cells or other harmful substances via cells or other harmful substances via phagocytosis (Figure 13-11)phagocytosis (Figure 13-11) TypesTypes

• NeutrophilsNeutrophils

• MonocytesMonocytes

• MacrophagesMacrophages Kupffer cells (liver)Kupffer cells (liver) Dust cells (lung)Dust cells (lung)



LymphocytesLymphocytes Most numerous of immune system cellsMost numerous of immune system cells Development of B cells—primitive stem cells migrate from Development of B cells—primitive stem cells migrate from

bone marrow and go through two stages of development bone marrow and go through two stages of development (Figure 13-12)(Figure 13-12)

• First stage—stem cells develop into immature B cells; takes place First stage—stem cells develop into immature B cells; takes place in the liver and bone marrow before birth and in the bone marrow in the liver and bone marrow before birth and in the bone marrow only in adults; immature B cells are small lymphocytes with only in adults; immature B cells are small lymphocytes with antibody molecules (which they have synthesized) in their plasma antibody molecules (which they have synthesized) in their plasma membranes; migrate chiefly to lymph nodesmembranes; migrate chiefly to lymph nodes

• Second stage—immature B cell develops into activated B cell; Second stage—immature B cell develops into activated B cell; initiated by immature B cell’s contact with antigens, which bind to initiated by immature B cell’s contact with antigens, which bind to its surface antibodies; activated B cell, by dividing repeatedly, its surface antibodies; activated B cell, by dividing repeatedly, forms two clones of cells—plasma cells and memory cells—forms two clones of cells—plasma cells and memory cells—plasma cells secrete antibodies into blood; memory cells stored in plasma cells secrete antibodies into blood; memory cells stored in lymph nodes; if subsequent exposure to antigen that activated B lymph nodes; if subsequent exposure to antigen that activated B cell occurs, memory cells become plasma cells and secrete cell occurs, memory cells become plasma cells and secrete antibodiesantibodies



Lymphocytes (cont.)Lymphocytes (cont.) Function of B cells—indirectly, B cells produce humoral Function of B cells—indirectly, B cells produce humoral

immunity; activated B cells develop into plasma cells; plasma immunity; activated B cells develop into plasma cells; plasma cells secrete antibodies into the blood; circulating antibodies cells secrete antibodies into the blood; circulating antibodies produce humoral immunity (Figure 13-12)produce humoral immunity (Figure 13-12)

Development of T cells—stem cells from bone marrow migrate Development of T cells—stem cells from bone marrow migrate to thymus gland (Figure 13-13)to thymus gland (Figure 13-13)

• Stage 1—stem cells develop into T cells; occurs in thymus during Stage 1—stem cells develop into T cells; occurs in thymus during few months before and after birth; T cells migrate chiefly to lymph few months before and after birth; T cells migrate chiefly to lymph nodesnodes

• Stage 2—T cells develop into sensitized T cells; occurs when, and Stage 2—T cells develop into sensitized T cells; occurs when, and if, antigen binds to T cell’s surface proteinsif, antigen binds to T cell’s surface proteins

Functions of T cells—produce cell-mediated immunity; kill Functions of T cells—produce cell-mediated immunity; kill invading cells by releasing a substance that poisons cells and invading cells by releasing a substance that poisons cells and also by releasing chemicals that attract and activate also by releasing chemicals that attract and activate macrophages to kill cells by phagocytosis (Figures 13-14 and macrophages to kill cells by phagocytosis (Figures 13-14 and 13-15)13-15)

Chapter 13 The Lymphatic System and Immunity. Elsevier items and derived items © 2008, 2004 by...

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