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© 2012 Pearson Education, Inc.
23The Lymphoid System
PowerPoint® Lecture Presentations prepared bySteven BassettSoutheast Community College Lincoln, Nebraska
© 2012 Pearson Education, Inc.
Introduction
The lymphoid system Lymphatic vessels Lymph (fluid connective tissue) Lymphoid tissues
Diffuse lymphoid tissues Lymph nodule
Lymphoid organs Lymph node Thymus: most active during infancy and youth. Spleen (the largest organ of the lymphatic system)
Plays central role in body’s defenses against viruses, bacteria, and other microorganismsLymphatic vessels originate in peripheral tissues and deliver lymph to the venous system.
© 2012 Pearson Education, Inc.
An Overview of the Lymphoid System
Lymph consists of: Interstitial fluid, which resembles blood
plasma, but with a lower concentration of proteins
Lymphocytes, cells responsible for the immune response
Macrophages of various types
© 2012 Pearson Education, Inc.
Functions of the lymphatic system
Primary functions of the lymphoid system: Produce, maintain, and distribute lymphocytes Maintain normal blood volume and eliminate
local variations in the chemical composition of the interstitial fluid
Provide an alternative route for the transport of hormones, nutrients, and waste products
© 2012 Pearson Education, Inc.
Figure 23.2a Lymphatic Capillaries
A three-dimensional view of the associationof blood capillaries and lymphatic capillaries.Arrows show the direction of blood,interstitial fluid, and lymph movement.
Looseconnectivetissue
Endothelialcells
Lymphflow
Interstitialfluid
Venule
Smoothmuscle
Bloodcapillaries
Arteriole
Lymphaticcapillary
© 2012 Pearson Education, Inc.
Structure of Lymphatic Vessels
Lymphatic capillaries (or terminal lymphatics) form a complex network within peripheral tissues.
Lymphatics contain internal valves that prevent backflow of lymph.
Lymphatic vessels (or lymphatics) carry lymph from peripheral tissues to the venous system. The right lymphatic duct receives lymph from the right side of
the thorax. The rest of the body’s lymph (most of the lymph) returns to
the venous system through thoracic duct. Thoracic duct joins the left subclavian vein at the junction of left internal jugular vein.
Large lymphatic trunks are located in the posterior thoracic and abdominal wall.
© 2012 Pearson Education, Inc.
Figure 23.2b Lymphatic Capillaries
Sectional view through a cluster of lymphatic capillaries
Incompletebasal lamina
Lymphflow
Looseconnective
tissue
Lymphocyte
To largerlymphatics
Interstitialfluid
Interstitial fluid
Bloodcapillary
Lymphaticcapillary
© 2012 Pearson Education, Inc.
Figure 23.3ac Lymphatic Vessels and Valves
The cross-sectional view emphasizesthe structural differences betweenblood vessels and lymphatic vessels.
Lymphaticvessel
Vein
Artery
Towardvenoussystem
Lymphaticvalve
Lymphaticvessel
From lymphaticcapillaries
Artery
Vein
A diagrammatic view of loose connectivetissue showing small blood vessels anda lymphatic vessel. Arrows indicate thedirection of lymph flow.
© 2012 Pearson Education, Inc.
Structure of Lymphatic Vessels
Two sets of lymphatic vessels: Superficial lymphatic vessels travel with superficial
veins The subcutaneous layer next to the skin The loose connective tissues of the mucous membranes The loose connective tissues of the serous membranes
Deep lymphatic vessels are large lymphatic vessels that accompany the deep arteries and veins. Collect lymph from skeletal muscles and other organs of the
neck, limbs, and trunk, as well as visceral organs in the thoracic and abdominopelvic cavities
© 2012 Pearson Education, Inc.
Figure 23.1 Lymphoid SystemTonsil
Cervicallymph nodes
Right lymphatic duct
Thymus
Thoracic duct
Cisterna chyli
Lumbarlymph nodes
Lymphaticsof lower
limb
Lymphaticsof upper limb
Axillary lymph nodes
Thoracic (left lymphatic) duct
Lymphatics of mammary gland
Spleen
Mucosa-associated lymphoidtissue (MALT)
Pelviclymph nodes
Inguinallymph nodes
© 2012 Pearson Education, Inc.
Figure 23.4a Lymphatic Ducts and Lymphatic Drainage
The collecting system of lymph vessels, lymph nodes, and major lymphaticcollecting ducts and their relationship to the brachiocephalic veins
Right lumbar trunk
Inferior vena cava(cut)
Azygos vein
Rib (cut)
Superiorvena cava (cut)
Right bronchomediastinaltrunk
Right subclavian vein
Right internal jugular vein
Right jugular trunk
Right lymphatic duct
Right subclavian trunk
Brachiocephalic veins
Left internal jugular vein
Left jugular trunk
Thoracic duct
Left subclavian trunk
Left bronchomediastinal trunk
Left subclavianvein
First rib(cut)
Highestintercostalvein
Thoracicduct
Thoraciclymph nodes
Hemiazygosvein
Parietalpleura (cut)
Diaphragm
Cisterna chyli
Intestinal trunk
Left lumbar trunk
© 2012 Pearson Education, Inc.
Figure 23.4b Lymphatic Ducts and Lymphatic Drainage
The thoracic duct collects lymphfrom tissues inferior to thediaphragm and from the left side ofthe upper body. The right lymphaticduct drains the right half of thebody superior to the diaphragm.
Drainageof thoracicduct
Drainageof right
lymphaticduct
© 2012 Pearson Education, Inc.
Lymphocytes
Lymphocytes are the primary cells of the Lymphoid system, and they are responsible for specific immunity. They respond to the presence of
Invading organisms, such as bacteria and viruses Abnormal body cells, such as virus-infected cells or
cancer cells Foreign proteins, such as the toxins released by some
bacteria
© 2012 Pearson Education, Inc.
Lynphocytes
Three different classes of lymphocytes in the blood: T cells (thymus dependent)
Cytotoxic T cells Helper T cells Suppressor T cells Memory T cells
B cells (bone marrow derived) Plasma cells (providing humoral immunity) Memory B cells (stay in the body to fight off the second time
infection easier)
NK cells (natural killer)
© 2012 Pearson Education, Inc.
Figure 23.6a Lymphocytes and the Immune Response
BACTERIA
Macrophageactivation
Antigenpresentation
Activation ofcytotoxic T cells
Activation ofhelper T cells
Activation ofB cells
Destruction ofbacteria bycell lysis
Antibodyproduction byplasmocytes
Defenses against bacterial pathogensare usually initiated by activemacrophages.
© 2012 Pearson Education, Inc.
Figure 23.7 Derivation and Distribution of Lymphocytes
The second group of stemcells migrates to the thymus,where subsequent divisionsproduce daughter cells thatmature into T cells.
One group remains in thebone marrow, producingdaughter cells that matureinto B cells and NK cellsthat enter peripheraltissues.
Mature T cells leave the circulation to take temporary residence in peripheraltissues. All three types of lymphocytes circulate throughout the body in thebloodstream.
Cell-mediatedimmunity
Antibody-mediatedimmunity
Immunologicalsurveillance
Peripheral Tissues
Red Bone MarrowThymus
Lymphoid stem cells
Mature T cell
Thymichormones
Production anddifferentiation of
T cells
Migrate tothymus
Transported bycirculatory system
Lymphoid stem cells
Mature T cell B cells NK cells
Lymphoid stem cells
Pluripotential stem cell
Interleukin-7
As they mature, B cellsand NK cells enter thebloodstream and migrateto peripheral tissues.
© 2012 Pearson Education, Inc.
Lymphoid Tissues
Any tissue containing an abundance of lymphocytes
Diffuse lymphoid tissues—loosely packed lymphocytes within connective tissue
Lymphoid nodules—densely packed lymphocytes within loose connective tissue Tonsils
Pharyngeal tonsils(Adenoid) Lingual tonsils (at the base of the tongue) Palatine tonsils(at the entrance to oropharynx)
Aggregated lymphoid nodules (Peyer’s patches)
© 2012 Pearson Education, Inc.
Figure 23.8c Histology of Lymphoid Tissues
The location of the tonsils and the histological organization of a single tonsil
Pharyngeal tonsil
Pharyngeal epithelium
Germinal centerswithin nodules
LM 50
Pharyngeal tonsil
Palatine tonsil
Lingual tonsil
Palate
© 2012 Pearson Education, Inc.
Lymphoid Organs
Lymphoid tissues that are separated from surrounding tissues by a capsule
Lymph nodes Receive the lymph through afferent vessels and the
cleanest lymph will leave the node through efferent vessels.
Thymus Spleen
© 2012 Pearson Education, Inc.
Figure 23.1 Lymphoid SystemTonsil
Cervicallymph nodes
Right lymphatic duct
Thymus
Thoracic duct
Cisterna chyli
Lumbarlymph nodes
Lymphaticsof lower
limb
Lymphaticsof upper limb
Axillary lymph nodes
Thoracic (left lymphatic) duct
Lymphatics of mammary gland
Spleen
Mucosa-associated lymphoidtissue (MALT)
Pelviclymph nodes
Inguinallymph nodes
© 2012 Pearson Education, Inc.
Figure 23.9 Structure of a Lymph Node
Lymph node artery and vein
HilumLymph nodes
Lymphnodes
Lymphvessel
Efferent vessel
Trabeculae
Medulla
Cortex
Subcapsularspace
Deep cortex(T cells)
Capsule Medullary cord(B cells and
plasmocytes)
Afferentvessel
Medullary sinus
Outer cortex (B cells)
DividingB cell
Germinalcenter
Subcapsularspace
Outer cortex Capsule
Dendriticcells
Nuclei ofB cells
Capillary
© 2012 Pearson Education, Inc.
Figure 23.10 Lymphatic Drainage of the Head and Neck
Periauricularlymph node
Retroauricularlymph node
Occipital lymph node
Parotid lymph node
Superficial cervicallymph node
Deep cervicallymph node
Sternocleidomastoidmuscle
Orbicularis oculimuscle
Infraorbitallymph node
Submandicularlymph node
Buccal lymph node
Mandibular lymph node
Submental lymph node
Parotid salivary gland
© 2012 Pearson Education, Inc.
Figure 23.11a Lymphatic Drainage of the Upper Limb
Superficial lymphaticvessels and nodes thatdrain the upper limband chest of a male
Deltopectoral lymph node
Deltoid muscle
Pectoralis major muscle
Cephalic vein
Basilic vein
Axillarylymph nodes
Supratrochlearlymph node
© 2012 Pearson Education, Inc.
Figure 23.11b Lymphatic Drainage of the Upper Limb
Superficial and deeper lymphatic vessels and nodes of the upper limb and chest of a female
Subclavianlymph node
Axillarylymph nodes
Pectoralis majormuscle (cut)
Axillaryvein
Subscapularlymph node
Pectorallymph node
Mammarygland
Centrallymph node
Parasternallymph node
© 2012 Pearson Education, Inc.
Figure 23.12 Lymphatic Drainage of the Lower Limb
Superficial inguinallymph nodes
Deep inguinallymph nodes
Popliteal lymph nodes
Great saphenousvein
© 2012 Pearson Education, Inc.
Figure 23.14b Lymphatic Drainage of the Inguinal Region
A superficial and deeper view of the inguinal region of a maleshowing the distribution of lymph nodes and lymphatics
Deep Inguinaland Iliac Lymph Nodes
SuperficialInguinal Lymph Nodes
Superficial inguinallymph nodes
Lymphaticvessels
Fascia
Anterior superior iliac spineExternal iliac artery
External iliac vein
Inguinalligament
Femoralartery
Deep inguinallymph nodes
Femoral vein
Greatsaphenous vein
© 2012 Pearson Education, Inc.
Figure 23.15 Lymph Nodes in the Large Intestine and Associated Mesenteries
Inferior mesentericlymph nodes
Inferior mesentericartery
Distal portionof duodenum
Superior mesentericartery
Descending colon
Sigmoid colon
Rectum
Appendix
Appendicularlymph nodes
Transverse mesocoliclymph nodes
Cecum
Ileum
Ascending colon
Transverse colon
Superior mesentericlymph nodes
Ileocolic lymphnodes
© 2012 Pearson Education, Inc.
Figure 23.16a Anatomy and Histological Organization of the Thymus
The location of the thymus on gross dissection;note the relationship to other organs in the chest
Right lobe
Diaphragm
Trachea
Thyroid gland
Rightlung
Leftlung
Left lobe
THYMUS
Heart
© 2012 Pearson Education, Inc.
Figure 23.16bc Anatomy and Histological Organization of the Thymus
Anatomical landmarkson the thymus
Histology of the thymus. Note the fibrous septathat divide the thymic tissue into lobulesresembling interconnected lymphoid nodules.
Left lobe
Rightlobe
Septa
Lobule
SeptaMedulla Cortex
Lobule
Lobule
The thymus gland LM 50
© 2012 Pearson Education, Inc.
Figure 23.16cd Anatomy and Histological Organization of the Thymus
Histology of the thymus. Note the fibrous septathat divide the thymic tissue into lobulesresembling interconnected lymphoid nodules.
Histology of the unusual structure of thymiccorpuscles. The small cells in view arelymphocytes in various stages of development.
A thymic corpuscle LM 550
Lymphocytes
Thymiccorpuscle
Reticularcells
SeptaMedulla Cortex
Lobule
Lobule
The thymus gland LM 50
© 2012 Pearson Education, Inc.
Figure 23.17a Anatomy and Histological Organization of the Spleen
The shape of the spleen roughly conforms to theshapes of adjacent organs. This transverse sectionthrough the trunk shows the typical position of thespleen within the abdominopelvic cavity (inferior view).
Spleen
Aorta
Rib
Pancreas
Liver
Parietal peritoneum
Visceral peritoneum
Stomach
Diaphragm
Kidneys
Gastrosplenic ligament
Gastric area
Diaphragmatic surface
SPLEEN
Hilum
Renal area
© 2012 Pearson Education, Inc.
Figure 23.17b Anatomy and Histological Organization of the Spleen
External appearance of the visceral surface of theintact spleen showing major anatomical landmarks.This view should be compared with that of part (a).
SUPERIOR
INFERIOR
Splenic lymphaticvessel
Splenic artery
Splenic vein
Hilum
Renalarea
Gastricarea
© 2012 Pearson Education, Inc.
Aging and the Lymphoid System
With advancing age, the lymphoid system becomes less effective at combating disease.
T cells become less responsive to antigens. The number of helper T cells is reduced. B cells are less responsive. Antibody levels do not rise as quickly after
antigen exposure.
The net result is an increased susceptibility to viral and bacterial infection, and cancer.