© 2012 pearson education, inc. structures of body defenses organization of the lymphatic system 1....
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© 2012 Pearson Education, Inc.
Structures of Body Defenses
• Organization of the Lymphatic System
1. Lymph
• A fluid similar to plasma but does not have plasma proteins
2. Lymphatic vessels (lymphatics)
• Carry lymph from peripheral tissues to the venous system
3. Lymphoid tissues and lymphoid organs
4. Lymphocytes, phagocytes, and other immune system cells
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Structures of Body Defenses
• Function of the Lymphatic System
• To produce, maintain, and distribute lymphocytes
• Lymphocyte Production • Lymphocytes are produced
• In lymphoid tissues (e.g., tonsils)
• Lymphoid organs (e.g., spleen, thymus)
• In red bone marrow
• Lymphocyte distribution
• Detects problems
• Travels into site of injury or infection
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Structures of Body Defenses
• Lymphocyte Circulation
• From blood to interstitial fluid through capillaries
• Returns to venous blood through lymphatic vessels
• The Circulation of Fluids
• From blood plasma to lymph and back to the venous system
• Transports hormones, nutrients, and waste products
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Structures of Body Defenses
• Lymphatic Vessels
• Are vessels that carry lymph
• Lymphatic system begins with smallest vessels
• Lymphatic capillaries (terminal lymphatics)
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Structures of Body Defenses
• Lymphatic Capillaries
• Differ from blood capillaries in four ways
1. Start as pockets rather than tubes
2. Have larger diameters
3. Have thinner walls
4. Flat or irregular outline in sectional view
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Figure 22-2a Lymphatic Capillaries
Smoothmuscle
Arteriole Lymphaticcapillary
Venule Interstitialfluid
Blood capillaries Loose connective tissue
Lymphflow
Endothelialcells
The interwoven network formed by blood capillariesand lymphatic capillaries.
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Figure 22-2b Lymphatic Capillaries
Incompletebasementmembrane
Lymphflow
Lymphocyte
To largerlymphatics
Looseconnective
tissue
Interstitial fluid
Interstitial fluid
Bloodcapillary
Lymphaticcapillary
A sectional view indicating the movement of fluidfrom the plasma, through the tissues as interstitialfluid, and into the lymphatic system as lymph.
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Structures of Body Defenses
• Lymphatic Capillaries
• Endothelial cells loosely bound together with overlap
• Overlap acts as one-way valve
• Allows fluids, solutes, viruses, and bacteria to enter
• Prevents return to intercellular space
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Structures of Body Defenses
• Lymph Flow
• From lymphatic capillaries to larger lymphatic vessels
containing one-way valves
• Lymphatic vessels travel with veins
• Lacteals
• Are special lymphatic capillaries in small intestine
• Transport lipids from digestive tract
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Figure 22-3a Lymphatic Vessels and Valves
Vein
Artery
Lymphaticvessel
Lymphaticvalve
From lymphaticcapillaries
Vein
Artery
Lymphaticvessel
Towardvenoussystem
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Figure 22-3b Lymphatic Vessels and Valves
Lymphaticvessel
Lymphaticvalve
Like valves in veins, eachlymphatic valve consists ofa pair of flaps that permitmovement of fluid in onlyone direction.
Lymphatic vessel and valve LM 63
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Figure 22-4 The Relationship between the Lymphatic Ducts and the Venous System
Right internal jugular vein
Right jugular trunk
Right lymphatic duct
Right subclavian trunk
Right subclavian vein
Right bronchomediastinal trunk
Superiorvena cava (cut)
Azygos vein
Rib (cut)
Brachiocephalic veins
Drainageof right
lymphaticduct
Inferior vena cava (cut)
Drainageof thoracicduct
Right lumbar trunk
Left internal jugular vein
Left jugular trunk
Thoracic duct
Left subclavian trunk
Left bronchomediastinaltrunk
Left subclavianvein
First rib(cut)
Highestintercostalvein
Thoracicduct
Thoraciclymph nodes
Hemiazygosvein
Parietalpleura (cut)
Diaphragm
Cisterna chyli
Intestinal trunk
Left lumbar trunk
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Structures of Body Defenses
• Lymphoid Tissues
• Connective tissues dominated by lymphocytes
• Lymphoid Nodules
• Areolar tissue with densely packed lymphocytes
• Germinal center contains dividing lymphocytes
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Figure 22-7a Lymphoid Nodules (Part 1 of 2)
Intestinal lumen
Aggregatedlymphoid nodule
Underlyingconnective tissue
LM 40Aggregated lymphoid nodules in large intestine
Aggregated lymphoid nodules in section
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Figure 22-7a Lymphoid Nodules (Part 2 of 2)
Aggregated lymphoid nodules in section
Intestinal lumen
Mucousmembrane
Germinal center
Aggregatedlymphoid nodule
Underlyingconnective tissue
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Figure 22-7b Lymphoid Nodules
Pharyngealepithelium
Germinal centerswithin nodules
Pharyngeal tonsil
Palate
Palatine tonsil
Lingual tonsil
The positions of the tonsils and a tonsil in section. Notice the pale germinal centers, where lymphocyte cell divisions occur.
Pharyngeal tonsil LM 20
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Structures of Body Defenses
• Distribution of Lymphoid Nodules
• Lymph nodes
• Spleen
• Respiratory tract (tonsils)
• Along digestive, urinary, and reproductive tracts
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Structures of Body Defenses
• Mucosa-Associated Lymphoid Tissue (MALT)
• Lymphoid tissues associated with the digestive
system
• Aggregated Lymphoid Nodules
• Clustered deep to intestinal epithelial lining
• Appendix (Vermiform Appendix)
• Contains a mass of fused lymphoid nodules
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Structures of Body Defenses
• The Five Tonsils
• In wall of pharynx
• Left and right palatine tonsils
• Pharyngeal tonsil (adenoid)
• Two lingual tonsils
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Structures of Body Defenses
• Lymph Nodes
• Trabeculae
• Bundles of collagen fibers
• Extend from capsule into interior of lymph node
• Hilum
• A shallow indentation where blood vessels and nerves
reach the lymph node
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Structures of Body Defenses
• Lymph Nodes
• Afferent lymphatics
• Carry lymph
• From peripheral tissues to lymph node
• Efferent lymphatics
• Leave lymph node at hilum
• Carry lymph to venous circulation
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Figure 22-8 The Structure of a Lymph Node (Part 1 of 2)
Efferentvessel
Lymph nodeartery and vein
Hilum
Lymphvessel
Lymphnodes
Lymph nodes
Medullary sinus
Outer cortex (B cells)
Trabeculae
Medulla
Cortex
Subcapsularspace
Deep cortex(T cells)
Capsule Medullary cord(B cells and
plasma cells)
Afferentvessel
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Structures of Body Defenses
• Lymph Node Function
• A filter
• Purifies lymph before return to venous circulation
• Removes:
• Debris
• Pathogens
• 99% of antigens
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Structures of Body Defenses
• Lymphatic Functions
• Lymphoid tissues and lymph nodes
• Distributed to monitor peripheral infections
• Respond before infections reach vital organs of trunk
• Lymph nodes of gut, trachea, lungs, and thoracic duct
• Protect against pathogens in digestive and respiratory
systems
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22-2 Structures of Body Defenses
• Lymph Nodes (Glands)
• Large lymph nodes at groin and base of neck
• Swell in response to inflammation
• Lymphadenopathy
• Chronic or excessive enlargement of lymph nodes
• May indicate infections, endocrine disorders, or cancer
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22-2 Structures of Body Defenses
• The Thymus
• Located in mediastinum
• Atrophies after puberty
• Diminishing effectiveness of immune system
• Divisions of the Thymus
• Thymus is divided into two thymic lobes
• Septa divide lobes into smaller lobules
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Figure 22-9a The Thymus
Thyroid gland
Trachea
Right lobe
Diaphragm
Rightlung
THYMUS
The appearance and position of the thymus inrelation to other organs in the chest.
Leftlobe
Heart
Leftlung
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Figure 22-9b The Thymus
Rightlobe
Leftlobe
Lobule
Anatomicallandmarks onthe thymus.
Septa
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Figure 22-9c The Thymus CortexSeptaMedulla
Lobule
Lobule
The thymus gland LM 50
Fibrous septa divide the tissue of the thymus into lobulesresembling interconnected lymphoid nodules.
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22-2 Structures of Body Defenses
• Three Functions of the Spleen
1. Removal of abnormal blood cells and other blood components by phagocytosis
2. Storage of iron recycled from red blood cells
3. Initiation of immune responses by B cells and T cells
• In response to antigens in circulating blood
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Figure 22-10b The Spleen
SUPERIOR
Gastricarea
Hilum
Splenic vein
Splenic artery
Splenic lymphaticvessel
Renalarea
INFERIOR
A posterior view of the surface of an intactspleen, showing major anatomical landmarks.
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Figure 22-10c The Spleen
The histological appearance of the spleen. White pulp isdominated by lymphocytes; it appears purple becausethe nuclei of lymphocytes stain very darkly. Red pulpcontains a large number of red blood cells.
The spleen LM 50
White pulp ofsplenic nodule
Capsule
Red pulp
Trabecularartery
Central artery insplenic nodule