Ch 23_lecture_presentation

© 2012 Pearson Education, Inc.
23
The Lymphoid System
PowerPoint® Lecture Presentations prepared by
Steven Bassett
Southeast Community College
Lincoln, Nebraska

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 microorganisms
Lymphatic vessels originate in peripheral tissues and deliver lymph to
the venous system.

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

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

Figure 23.2a Lymphatic Capillaries
A three-dimensional view of the association
of blood capillaries and lymphatic capillaries.
Arrows show the direction of blood,
interstitial fluid, and lymph movement.
Arteriole
Endothelial
cells
Loose
connective
tissue
Lymph
flow
Interstitial
fluid
Venule
Smooth
muscle
Blood
capillaries
Lymphatic
capillary

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.

Figure 23.2b Lymphatic Capillaries
Incomplete
basal lamina
Sectional view through a cluster of lymphatic capillaries
Lymph
flow
Loose
connective
tissue
Lymphocyte
To larger
lymphatics
Interstitial
fluid
Interstitial fluid
Blood
capillary
Lymphatic
capillary

Figure 23.3ac Lymphatic Vessels and Valves
Vein
Lymphatic
vessel
Artery
Vein
Lymphatic
vessel
The cross-sectional view emphasizes
the structural differences between
blood vessels and lymphatic vessels.
Toward
venous
system
Lymphatic
valve
From lymphatic
capillaries
Artery
A diagrammatic view of loose connective
tissue showing small blood vessels and
a lymphatic vessel. Arrows indicate the
direction of lymph flow.

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

Figure 23.1 Lymphoid System
Tonsil
Cervical
lymph nodes
Right lymphatic duct
Thymus
Thoracic duct
Cisterna chyli
Lumbar
lymph nodes
Lymphatics
of lower
limb
Lymphatics
of upper limb
Axillary lymph nodes
Thoracic (left lymphatic) duct
Lymphatics of mammary gland
Spleen
Mucosa-associated lymphoid
tissue (MALT)
Pelvic
lymph nodes
Inguinal
lymph nodes

Figure 23.4a Lymphatic Ducts and Lymphatic Drainage
Right internal jugular vein
Right jugular trunk
Right lymphatic duct
Right subclavian trunk
Right subclavian vein
Right bronchomediastinal
trunk
Superior
vena cava (cut)
Rib (cut)
Inferior vena cava
(cut)
Right lumbar trunk
The collecting system of lymph vessels, lymph nodes, and major lymphatic
collecting ducts and their relationship to the brachiocephalic veins
Azygos vein
Brachiocephalic veins
Left internal jugular vein
Left jugular trunk
Thoracic duct
Left subclavian trunk
Left bronchomediastinal
trunk
Left subclavian
vein
First rib
(cut)
Highest
intercostal
vein
Thoracic
duct
Thoracic
lymph nodes
Hemiazygos
vein
Parietal
pleura (cut)
Diaphragm
Cisterna chyli
Intestinal trunk
Left lumbar trunk

Figure 23.4b Lymphatic Ducts and Lymphatic Drainage
Drainage
of thoracic
duct
Drainage
of right
lymphatic
duct
The thoracic duct collects lymph
from tissues inferior to the
diaphragm and from the left side of
the upper body. The right lymphatic
duct drains the right half of the
body superior to the diaphragm.

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

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)

Figure 23.6a Lymphocytes and the Immune Response
BACTERIA
Macrophage
activation
Antigen
presentation
Activation of
cytotoxic T cells
Activation of
helper T cells
Activation of
B cells
Destruction of
bacteria by
cell lysis
Antibody
production by
plasmocytes
Defenses against bacterial pathogens
are usually initiated by active
macrophages.

Figure 23.7 Derivation and Distribution of Lymphocytes
Thymus Red Bone Marrow
The second group of stem
cells migrates to the thymus,
where subsequent divisions
produce daughter cells that
mature into T cells.
One group remains in the
bone marrow, producing
daughter cells that mature
into B cells and NK cells
that enter peripheral
tissues.
Peripheral Tissues
Cell-mediated
immunity
Pluripotential stem cell
Interleukin-7
Lymphoid stem cells
Antibody-mediated
immunity
Immunological
surveillance
Mature T cells leave the circulation to take temporary residence in peripheral
tissues. All three types of lymphocytes circulate throughout the body in the
bloodstream.
Lymphoid stem cells
Mature T cell
Thymic
hormones
Production and
differentiation of
T cells
Migrate to
thymus
Transported by
circulatory system
Lymphoid stem cells
Mature T cell B cells NK cells
As they mature, B cells
and NK cells enter the
bloodstream and migrate
to peripheral tissues.

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)

Figure 23.8c Histology of Lymphoid Tissues
The location of the tonsils and the histological organization of a single tonsil
Palate
Pharyngeal tonsil
Pharyngeal
epithelium
Germinal centers
within nodules
LM ´ 50
Pharyngeal tonsil
Palatine tonsil
Lingual tonsil

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

Figure 23.9 Structure of a Lymph Node
Lymph node artery and vein
Hilum
Lymph nodes
Lymph
nodes
Lymph
vessel
Efferent
vessel
Trabeculae
Medulla
Cortex
Subcapsular
space
Deep cortex
(T cells)
Capsule Medullary cord
(B cells and
plasmocytes)
Afferent
vessel
Medullary sinus
Outer cortex (B cells)
Dividing
B cell
Germinal
center
Subcapsular
space
Outer cortex Capsule
Dendritic
cells
Nuclei of
B cells
Capillary

Figure 23.10 Lymphatic Drainage of the Head and Neck
Parotid salivary gland
Buccal lymph node
Mandibular lymph node
Submental lymph node
Periauricular
lymph node
Retroauricular
lymph node
Occipital lymph node
Parotid lymph node
Superficial cervical
lymph node
Deep cervical
lymph node
Sternocleidomastoid
muscle
Orbicularis oculi
muscle
Infraorbital
lymph node
Submandicular
lymph node

Figure 23.11a Lymphatic Drainage of the Upper Limb
Superficial lymphatic
vessels and nodes that
drain the upper limb
and chest of a male
Deltoid muscle
Deltopectoral lymph node
Pectoralis major muscle
Axillary
lymph nodes
Cephalic vein
Basilic vein
Supratrochlear
lymph node

Figure 23.11b Lymphatic Drainage of the Upper Limb
lymph node
Parasternal
lymph node
Pectoralis major
muscle (cut)
Axillary
vein
Subclavian
lymph node
Axillary
lymph nodes
Subscapular
lymph node
Pectoral
lymph node
Mammary
gland
Central
Superficial and deeper lymphatic vessels and
nodes of the upper limb and chest of a female

Figure 23.12 Lymphatic Drainage of the Lower Limb
Superficial inguinal
lymph nodes
Deep inguinal
lymph nodes
Great saphenous
vein
Popliteal lymph
nodes

Figure 23.14b Lymphatic Drainage of the Inguinal Region
Deep Inguinal
and Iliac Lymph Nodes
Superficial
Inguinal Lymph Nodes
Anterior superior iliac spine
Superficial inguinal
lymph nodes
Fascia
Lymphatic
vessels
A superficial and deeper view of the inguinal region of a male
showing the distribution of lymph nodes and lymphatics
External iliac artery
External iliac vein
Inguinal
ligament
Femoral
artery
Deep inguinal
lymph nodes
Femoral vein
Great
saphenous vein

Figure 23.15 Lymph Nodes in the Large Intestine and Associated Mesenteries
Transverse colon
Superior mesenteric
lymph nodes
Ascending colon
Ileocolic lymph
nodes
Ileum
Appendicular
lymph nodes
Superior mesenteric
artery
Distal portion
of duodenum
Inferior mesenteric
artery
Inferior mesenteric
lymph nodes
Descending colon
Sigmoid colon
Rectum
Appendix
Transverse mesocolic
lymph nodes
Cecum

Figure 23.16a Anatomy and Histological Organization of the Thymus
Thyroid gland
Trachea
The location of the thymus on gross dissection;
note the relationship to other organs in the chest
Right lobe
Diaphragm
Right
lung
Left
lung
THYMUS
Left
lobe
Heart

Figure 23.16bc Anatomy and Histological Organization of the Thymus
Right
lobe
Septa
Lobule
Anatomical landmarks
on the thymus
Left
lobe
Medulla Septa Cortex
Lobule
Lobule
The thymus gland LM ´ 50
Histology of the thymus. Note the fibrous septa
that divide the thymic tissue into lobules
resembling interconnected lymphoid nodules.

Figure 23.16cd Anatomy and Histological Organization of the Thymus
A thymic corpuscle LM ´ 550
Histology of the thymus. Note the fibrous septa
that divide the thymic tissue into lobules
resembling interconnected lymphoid nodules.
Histology of the unusual structure of thymic
corpuscles. The small cells in view are
lymphocytes in various stages of development.
Lymphocytes
Thymic
corpuscle
Reticular
cells
Medulla Septa Cortex
Lobule
Lobule
The thymus gland LM ´ 50

Figure 23.17a Anatomy and Histological Organization of the Spleen
The shape of the spleen roughly conforms to the
shapes of adjacent organs. This transverse section
through the trunk shows the typical position of the
spleen within the abdominopelvic cavity (inferior view).
Spleen
Rib
Pancreas
Aorta
Liver
Parietal peritoneum
Visceral peritoneum
Stomach
Diaphragm
Gastrosplenic ligament
Gastric area
Diaphragmatic surface
SPLEEN
Hilum
Renal area
Kidneys

Figure 23.17b Anatomy and Histological Organization of the Spleen
Hilum
Splenic vein
Splenic artery
External appearance of the visceral surface of the
intact spleen showing major anatomical landmarks.
This view should be compared with that of part (a).
SUPERIOR
INFERIOR
Splenic lymphatic
vessel
Renal
area
Gastric
area

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.

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