Chapter 21 Lymphatic and
Immune Systems
21-1
Ch. 21 Study Guide
1. Critically read Chapter 21 pp. 816-829 right
before 21.2 (Nonspecific Resistance) section.
2. Comprehend Terminology (those in bold)
3. Study-- Figure questions, Think About It
questions, and Before You Go On (sectionending) questions
4. Do end-of-chapter questions:
– Testing Your Recall— 1-4, 11-13
– True or False– 1, 2, 5
– Testing Your Comprehension-- #2
2
§ The Lymphatic System
1. What is the lymphatic system? a
network of vessels that penetrate nearly
every tissue of the body and a collection of
tissues and organs that produce immune
cells. Fig. 21.3, 21.1
2. Components of the system:
– Lacking a contractile “heart”; “pumpless”
– Lymph:
* Blood is to blood vessels as _______ is to
lymphatic vessels.
– Lymphatic vessels:
– Lymphatic tissue & lymphatic organs:
21-3
Capillary bed
Lymphatic
capillary
Where are lymphatic capillaries?
21-4
• Lymphatic
vessels?
• 5 lymphatic
organs– (A-E)
A-Tonsils
E-Lymph nodes
(7 locations):
1.Cervical
B-Thymus
C-Spleen
2.Axillary
3.Thoracic
4.Abdominal
MUST
MEMORIZE
this
information.
D-Red
bone
marrow
5.Intestinal &
mesenteric
6.Inguinal
7.Popliteal
21-5
“Swollen
glands”
§ Functions of Lymphatic System (1)
1. Fluid recovery:
– absorbs ECF proteins and fluid (2 to
4 L/day) from tissues and returns it to
the bloodstream
• interference with lymphatic
drainage leads to severe edema
(Fig. 21.2)
21-6
Elephantiasis—
Cause- mosquitoborne roundworms
infect the lymph
nodes and block the
flow of lymph
Symptoms– chronic
edema, especially
extremities;
Thickening of the skin
21-7
§ Functions of Lymphatic System (2)
2. Immunity:
– fluids from all capillary beds are filtered
– immune cells (where are they?) stand
ready to respond to foreign cells or
chemicals encountered
3. Lipid absorption:
– Lacteals (what are they?) in small
intestine absorb dietary lipids
21-8
§ Lymph and Lymphatic Vessels (1)
1. Lymph
– clear, colorless fluid, similar to plasma but
much ________ protein; others include . . .
2. Lymphatic capillaries (structures)
A. -- Closed at one end
B. -- Tethered to surrounding tissue by protein
filaments
C. -- Endothelial cells loosely overlapped;
tight junctions? Basement membrane?
D. -- Valvelike flaps at the edges of endothelial
cells
Fig. 21.3b
21-9
Fig. 21.3b–
uptake of
tissue fluid by
a lymphatic
capillary
21-10
§ Lymph and Lymphatic Vessels (2)
1. Larger lymphatic vessels composed of 3
layers:
– tunica interna: endothelium and valves
– tunica media: elastic fibers, smooth muscle
– tunica externa: thin outer layer
2. Compared to veins, lymphatic vessels:
– Their walls: thinner / thicker
– Their valves: (intervals) closer together/ farther
apart; therefore; ____ (more/less) valves in
lymphatics compared to veins
21-11
Fig. 21.4b
Fig. 21.4b:
valves
ensure a
one-way
flow of
lymph
21-12
Lymph flows forward
through open valves
Closed valves
§ Fluid exchange between the circulatory
and lymphatic systems (A)
– Principle: the lymphatic system picks up excess
tissue fluid and returns it to the bloodstream
– Routes: Continual recycling of fluid from blood
(blood capillaries) to the tissue, to the lymph, and
back to the blood stream
– Through what specific veins does the lymph
draining back to the bloodstream?
– Answer:________
Fig. 21.5
______________ veins
21-13
Lymphatic, one-way,
system
4. Two
Collecting
duct
3. Six
lymphatic
trunks
Cardiovascular system
Pulmonary circuit
Subclavian vein
Superior vena cava
Lymph node
Blood flow
2. Collecting
vessels
1. Lymphatic
capillaries
Systemic circuit
21-14
§ Fluid exchange between the circulatory
and lymphatic systems (B)
The sequence of fluid flow:
1. blood capillaries (blood) 
2. interstitial spaces (interstitial fluid) 
3. ________________(lymph) 
4. lymphatic vessels (lymph) 
5. lymphatic trunks (lymph) 
6. _______________(lymph) 
7.  subclavian veins (blood)
21-15
§ Route of Lymph Flow-A
1. Lymphatic capillaries 
2. Collecting vessels: course through many
lymph nodes; 
3. (Six) larger Lymphatic trunks: drain major
portions of body; 
4. (Two) Collecting ducts:
A. right lymphatic duct – receives lymph
from R arm, R side of head and thorax;
empties into R subclavian vein (Fig. 21.6
b-c)
21-16
Areas drained
by right
lymphatic
duct.
Areas drained
by thoracic
duct (left
lymphatic
duct).
21-17
Regions of the body drained by the
right lymphatic duct
21-18
§ Route of Lymph Flow-B
4. (Two) Collecting ducts (continued):
B. thoracic duct - larger and longer;
begins as a prominent sac in
abdomen called the cisterna chyli;
receives lymph from below
diaphragm, L arm, L side of head,
neck, and thorax; empties into L
subclavian vein
Fig. X
21-19
R1
L1+2
R2
L3
R3
Intercostal
trunks
4
L5
R5
6
21-20
§ Route of Lymph Flow-C
Six principal lymphatic trunks:
Jugular (R + L)
What
What
Subclavian (R + L)
vein do
vein do
Bronchomediastinal (R+L) they
they
drain
drain
Intercostal trunks
into?
into?
Cisterna chyli
The intestinal trunk
Lumbar trunks (R + L)
21-21
§ Mechanisms of Lymph Flow
• Lymph flows at low pressure and speed
Primary ones:
1. Moved along by rhythmic contractions of ______.
2. _________ prevent backward flow
Others mechanisms:
3. Flow aided by skeletal muscle pump
4. Arterial pulsation-5. Thoracic pump aids flow from abdominal to
thoracic cavity
6. Rapidly flowing blood in subclavian veins, draws
lymph into it
21-22
§ Lymphatic Cells/lymphocytes
1. Natural killer (NK) cells-- Large lymphocytes;
destroy bacteria & certain host cells Fig. 21.17, 18.18
2. T lymphocytes (T cells) Fig. 21.20
– Lymphocytes mature in thymus
Lymphocytes
3. B lymphocytes (B cells)– lymphocytes mature
in bone marrow; They differentiate into plasma cells that
produce antibodies
4. Antigen Presenting Cells: present to T cells
– macrophages (from monocytes); very large; phagocytosis (Fig.
21.7; 21.21)
– dendritic cells (in epidermis, mucous membranes and lymphatic
organs); perform endocytosis (similar to phagocytosis)
– reticular cells stationary, in the thymus Fig. 21.10
21-23
White blood cells production
Pluripotent
stem cell
Colony-forming
units (CFUs)
Mature
cells
Precursor
cells
leaves
Eosinophilic
CFU
Eosinophilic
myeloblast
Eosinophilic
promyelocyte
Eosinophilic
myelocyte
Eosinophil
Basophilic
CFU
Basophilic
myeloblast
Basophilic
promyelocyte
Basophilic
myelocyte
Basophil
Neutrophilic
CFU
Neutrophilic
myeloblast
Neutrophilic
promyelocyte
Neutrophilic
myelocyte
Neutrophil
Monocytic
CFU
Monoblast
Promonocyte
Monocyte
B lymphocyte
B prolymphocyte
Lymphocytic
CFU
T prolymphocyte
T lymphocyte
NK prolymphocyte
NK cell
Lymphoblast
The actions of a natural killer cell
21-25
The life history and migration of B and T cells
21-26
Phagocytosis by macrophages
21-27
1--The action of
antigenpresenting cells
(macrophages);
2--Then T-cells
initiate an
attack
21-28
Figure 21.10
Thymus

Reticular epi.
cells of cortex

Capsule
Reticular epi.
cells of medulla
Trabecula
21-29
§ Lymphatic Tissue– aggregation
of lymphocytes-- two forms:
1. Diffuse lymphatic tissue
– lymphocytes in mucous membranes and
CT of many organs
– prevalent in 4 body systems open to
exterior– Respiratory, digestive, etc.
systems
• It is called Mucosa-Associated
Lymphatic Tissue (MALT) (Fig. 21.8)
21-30
Lymphatic nodule in the mucosa of
the small intestine
Intestinal
villus
Lymphatic
nodule
21-31
§ Lymphatic Tissue– aggregation
of lymphocytes-- two forms:
2. Lymphatic nodules
A. come and go-- dense oval masses of
lymphocytes and macrophages, congregate in
response to pathogens
B. permanent feature-– in some organs– lymph nodes (Fig. 21.12),
tonsils, and appendix
– In the ileum– called Peyer patches: clusters
found at junction of small to large intestine
21-32
Lymphatic nodules
A lymph node
Fig. 21.12 a and b
Afferent
lymphatic
vessels
Efferent
lymphatic
vessel
21-33
§ Lymphatic Organs
In contrast to the diffuse lymphatic tissue, these
organs have: well defined anatomical sites;
have CT capsules
1. Primary lymphatic organs
– site where B and T cells become
immunocompetent
– ________________ and ______________
2. Secondary lymphatic organs
– immunocompetent cells populate these
tissues
– lymph nodes, __________, and tonsils
21-34
§ A. Red Bone Marrow
1. Functions– hemopoiesis and immunity
(supply of lymphocytes)
2. Structure– Fig. 21.9
– Highly vascularized, numerous arteries
enter the bone surface, and empty into
large sinusoids capillaries
– The sinusoids drain into a central
longitudinal vein that exit the bone
– Reticular cells; location? (1) induce
formation of WBCs; (2) aging reticular cells
become adipose cells
21-35
21-36
§ B. Thymus (1)
Thymus
21-37
Thymus (2)
• Large in fetus; after age 14 begins involution
• Capsule gives off trabeculae, divides thymus
into lobules
• Reticular epithelial cells (Fig. 21.10 a-c)
– Form BTB____________________; Where?
– secretes hormones (thymopoietin, thymulin
and thymosins etc.); Function?
• T Cells– develop in the cortex, migrate to the
medulla, and enter blood or lymphatic vessels
21-38
Figure 21.10a
See
next
slide
21-39
21-40
Figure 21.10c
Reticular epi.
cells of
cortex
Reticular epi.
cells of
medulla
Medulla
Cortex
21-41
§ C. Lymph Nodes (1)
• Lymph nodes - only organs that filter lymph; only
organs have afferent lymphatic vessels
• Bean-shaped, less than 3 cm long, hilum present;
most numerous lymphatic organs
1. Two main functions–
A. Cleanse the ___________
B. A site for T and B cell activation
2. 7 major locations— Fig. 21.1, Fig. 21.11
– Cervical lymph nodes etc.
21-42
• 5 lymphatic
organs– (A-E)
• Locations of
lymph nodes--
A-Tonsils
E-Lymph nodes
(7 locations):
1.Cervical
B-Thymus
C-Spleen
2.Axillary
3.Thoracic
4.Abdominal
MUST
MEMORIZE
this
information.
D-Red
bone
marrow
5.Intestinal &
mesenteric
6.Inguinal
7.Popliteal
21-43
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Colon
Superior
mesenteric
lymph nodes
Transverse
mesocolic
lymph nodes
Superior
mesenteric
artery
Inferior
mesenteric
artery
Ileocolic
lymph nodes
Small
intestine
Appendicular
lymph nodes
Appendix
(a)
Inferior
mesenteric
lymph nodes
§ C. Lymph Nodes (2)
3. Structure: (Fig. 21.12)
A. Stroma– capsule with trabeculae, subcapsular
sinus (reticular fibers, macrophages etc.)
B. Parenchyma– C-shaped cortex and medulla
(they perform functions of the lymph nodes)
4. Outer cortex: (outer 4/5)
• lymphatic nodules- shapes?
• When fighting a pathogen, germinal centers
develop where B cells become plasma cells
• Cortical sinuses  subcapsular s.  medullary
s.
21-45
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A--Stroma:
Capsule
Trabecula
B1--Cortex
Medulla
cord
Lymphatic nodule
Germinal center
B2--Medulla
Afferent
lymphatic
vessels
(a)
Efferent
lymphatic
vessel
§ C. Lymph Node (3)
5. Inner medulla:
– Branching network of medullary cords,
composed of lymphocytes, plasma cells,
macrophages, reticular cells
– Medullary sinuses
6. Routes of lymphatic flow: Afferent lymphatic v.
 (Network of sinuses)
 Subcapsular space
 Outer cortex and then deep cortex
 Sinuses of the Medulla (the core)
 Efferent lymphatic v. (at the hilum)
21-47
Disorders on lymph nodes
• Lymphadenopathy
– Collective term for all lymph node diseases
• Lymphadenitis
– swollen, painful node responding to foreign
antigen
• Lymph nodes are common sites (called
lymphoma) for metastatic cancer
– swollen, firm and usually painless
21-48
§ D. Tonsils
• Def. Patches of lymphatic tissue
located at the entrance to the pharynx
and vicinity
• Each tonsil:
– Covered by epithelium
– Having deep pits called tonsillar crypts
– Tonsillar crypts lined by lymphatic
nodules
Fig. 21.13
21-49
Histology
of
pharyngeal
tonsil
21-50
Three Locations of Tonsils
1. Pharyngeal tonsil (adenoid)
– single tonsil on wall of pharynx
2. Palatine tonsils
– A pair; at posterior margin of oral cavity
– Largest and most often infected called
tonsillitis (treatments-- tonsillectomy
or with antibiotics)
3. Lingual tonsils (many)
– at root of tongue
Fig. 21.13, 25.5
21-51
Regions of pharynx
Lingual
tonsils
Pharyngeal
tonsil
Hyoid
bone
Cricoid
cartilage
22-52
Figure 21.13a
Only 1
2; a pair
many
21-53
Figure 25.5a
21-54
§ E. Spleen (1)
• Largest lymphatic organ
• Location of the spleen:
– Protected by ribs 10-12
– Left hypochondriac region
– Dorsolateral to the stomach
– Fits between the diaphragm, stomach,
and kidney;
– The spleen has gastric area, renal
area, and colic area
Fig. 21.14a, b, x
21-55
21-56
ID
these
five
organs
—A-E
E
D
C
A
B
21-57
21-58
§ E. Spleen (2)
• Two types of tissue in fresh specimens as:
– red pulp: sinuses filled with erythrocytes
– white pulp: lymphocytes, macrophages;
surrounds small branches of splenic artery
• Functions of the spleen:
– ________________ in fetus
– RBC disposal (graveyard)
– Monitor the blood for foreign antigens;
stabilize blood volume by transferring excess
plasma from the blood into the lymphatic
system
Fig. 21.14c, Fig. Y
21-59
21-60
Fig. 21.14c
What cells account for the colors of the
red pulp and white pulp, respectively?
21-61