Chapter 21 Lymphatic and Immune Systems

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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 (section-ending) 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

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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:

§ The Lymphatic System

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Capillary bed

Lymphatic capillary

Where are lymphatic capillaries?

1.Cervical

2.Axillary

5.Intestinal & mesenteric

C-Spleen

B-Thymus

A-Tonsils• Lymphatic vessels?

• 5 lymphatic organs– (A-E)

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D-Red bone marrow

7.Popliteal

6.Inguinal

E-Lymph nodes (7 locations):

3.Thoracic

4.Abdominal

MUST MEMORIZE this information.

“Swollen glands”

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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)

§ Functions of Lymphatic System (1)

Elephantiasis—

Cause- mosquito-borne roundworms infect the lymph nodes and block the flow of lymph

Symptoms– chronic edema, especially extremities;Thickening of the skin

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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

§ Functions of Lymphatic System (2)

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§ 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 endB. -- Tethered to surrounding tissue by protein

filamentsC. -- Endothelial cells loosely overlapped;

tight junctions? Basement membrane?D. -- Valvelike flaps at the edges of endothelial

cells Fig. 21.3b

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Fig. 21.3b– uptake of tissue fluid by a lymphatic capillary

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§ 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

Fig. 21.4b

Fig. 21.4b:valves ensure a one-way flow of lymph

Closed valves

Lymph flows forward through open valves

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§ 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:________ ______________ veins

Fig. 21.5

Subclavian vein

Cardiovascular systemLymphatic, one-way, system

3. Six lymphatic

trunks

4. Two Collecting

duct

2. Collectingvessels

Lymph node

1. Lymphaticcapillaries

Pulmonary circuit

Superior vena cava

Blood flow

Systemic circuit21-14

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§ 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)

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§ Route of Lymph Flow-A1. 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)

Areas drained by thoracic duct (left lymphatic duct).

Areas drained by right lymphatic duct.

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Regions of the body drained by the right lymphatic duct

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§ 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

R1

R2

R3

R5

6

4

L1+2

L3

L5

Intercostal trunks

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§ Route of Lymph Flow-CSix principal lymphatic trunks:

Jugular (R + L)Subclavian (R + L)Bronchomediastinal (R+L)Intercostal trunks

The intestinal trunkLumbar trunks (R + L)

What vein do they drain into?

What vein do they drain into?

Cisterna chyli

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§ 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

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§ Lymphatic Cells/lymphocytes1. 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

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

Lymphocytes

leaves

Lymphoblast

B prolymphocyteB lymphocyte

T lymphocyte

NK cell

T prolymphocyte

NK prolymphocyte

Monoblast Promonocyte Monocyte

Basophil

Eosinophil

Neutrophil

Pluripotentstem cell

Colony-formingunits (CFUs)

Precursorcells

Maturecells

Eosinophilicmyelocyte

Eosinophilicpromyelocyte

Eosinophilicmyeloblast

EosinophilicCFU

BasophilicCFU

NeutrophilicCFU

MonocyticCFU

LymphocyticCFU

Basophilicmyeloblast

Neutrophilicmyeloblast

Neutrophilicpromyelocyte

Basophilicpromyelocyte

Basophilicmyelocyte

Neutrophilicmyelocyte

White blood cells production

The actions of a natural killer cell

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The life history and migration of B and T cells

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Phagocytosis by macrophages

1--The action of antigen-presenting cells (macrophages); 2--Then T-cells initiate an attack

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Figure 21.10

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Thymus

Reticular epi. cells of cortex

Reticular epi. cells of medulla

Capsule

Trabecula

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§ 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)

Intestinal villus

Lymphaticnodule

Lymphatic nodule in the mucosa of the small intestine

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§ Lymphatic Tissue– aggregation of lymphocytes-- two forms:

2. Lymphatic nodulesA. 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

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Fig. 21.12 a and b

Afferent lymphatic vessels

Efferent lymphatic vessel

A lymph nodeLymphatic nodules

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§ Lymphatic OrgansIn 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

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§ A. Red Bone Marrow1. 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

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§ B. Thymus (1)

Thymus

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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

Figure 21.10a

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See next slide

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Figure 21.10c

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CortexMedulla

Reticular epi. cells of cortex

Reticular epi. cells of medulla

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§ 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 organs1.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.

1.Cervical

2.Axillary

5.Intestinal & mesenteric

C-Spleen

B-Thymus

A-Tonsils• 5 lymphatic organs– (A-E)

• Locations of lymph nodes--

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D-Red bone marrow

7.Popliteal

6.Inguinal

E-Lymph nodes (7 locations):

3.Thoracic

4.Abdominal

MUST MEMORIZEthis information.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Colon

Appendix

(a)

Transversemesocolic

lymph nodesSuperiormesentericartery

Inferiormesentericartery

Inferiormesenteric

lymph nodesAppendicularlymph nodes

Smallintestine

Ileocoliclymph nodes

Superiormesenteric

lymph nodes

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§ 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.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(a)

B1--Cortex

Germinal center

B2--Medulla

A--Stroma:CapsuleTrabecula

Lymphatic nodule

Afferent lymphaticvessels

Efferentlymphatic

vessel

Medulla cord

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§ 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)

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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

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§ 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

nodulesFig. 21.13

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Histology of pharyngeal tonsil

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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

Hyoid bone

Cricoid cartilage

Regions of pharynx

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Pharyngeal tonsil

Lingual tonsils

Figure 21.13a

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Only 1

2; a pair

many

Figure 25.5a

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§ 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 areaFig. 21.14a, b, x

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A

D CB

EID these five organs—A-E

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§ 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

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Fig. 21.14c

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What cells account for the colors of the red pulp and white pulp, respectively?