LYMPHATIC SYSTEM

BY-: Dr. ANILESH1ST YR PGRD

HISTORY

•Ancient greeks Hippocrates and Aristotle described lymph as white fluid.

•Gasparo aselli an italian anatomist discovered lymphatic vessels in 1622.

•Van hook in 1652 demonstrated the presence of cisterna chyli and thoracic duct in humans.

William hunter in the late 18th century

was the first to describe the functions of lymphatic system.

Olof Rudbeck of swedish university described that lymphatic system constitute a circulatory system separate from blood circulation.

Lymphatic System•Lymphatic Vessels – transport only in the direction toward the heart .

Pick up the “extra” tissue fluid that capillaries leave

Lymph – the interstitial fluid carried by lymphatics

•Lymphatic Organs – “filtration” devices staged at various important junction points in the body

Lymph Vessels•Lymphatic capillaries – diffuse, highly permeable due to presence of:

-Minivalves loosely overlapping endothelial cells

-Collagen fiber attachment to surrounding structures prevents collapse of capillary

•Lymphatic collecting vessels like veins but thinner walled with more valves and anastomoses•Lymphatic trunks – lumbar, bronchomediastinal, subclavian, jugular and intestinal•Lymphatic ducts – Right Lymphatic Duct & Thoracic Duct

Lymphatic Capillaries

Figure 20.1b

Lymphatic Capillaries•During inflammation, lymph capillaries can absorb:

-Cell debris

-Pathogens

-Cancer cells

•Cells in the lymph nodes cleanse and “examine” this debris

•Lacteals – specialized lymph capillaries present in intestinal mucosa

-Absorb digested fat and deliver chyle to the blood

Lymph Capillaries

Lymphatic Collecting Vessels•Have the same three tunics as veins

•Have thinner walls, with more internal valves

•Anastomose more frequently

•Collecting vessels in the skin travel with superficial veins

•Deep vessels travel with arteries

•Nutrients are supplied from branching vasa vasorum

Lymphatic Trunks•Lymphatic trunks are formed by the union of the largest collecting ducts

•Major trunks include: -

Paired lumbar, bronchomediastinal, subclavian, and jugular trunks

-A single intestinal trunk

Lymphatic Trunks•Lymph is delivered into one of two large trunks

-Right lymphatic duct – drains the right upper arm and the right side of the head and thorax.

-Thoracic duct – arises from the cisterna chyli and drains the rest of the body.

NOTE- Lymph from these ducts enters the blood stream via the left subclavian vein and the right subclavian vein

Lymph Transport•The lymphatic system lacks a pumping organ

•Vessels are low-pressure conduits

•Uses the same methods as veins to propel lymph: -

Pulsations of nearby arteries -

Contractions of smooth muscle in the walls of the lymphatics

COMPOSITION OF LYMPH

•PROTEINS : 2 to 6 % of solids.

•Depending upon the part of body from which it is collected

Albumin, globulin, clotting factors (fibrinogen, prothrombin) , all antibodies and enzymes.

•LIPIDS : 5-15 % - mainly chylomicrons and lipoproteins.

•CARBOHYDRATES : Sugar - 132 mg per 100 ml (Mainly glucose).

•Non protein nitrogenous substances : Urea, A.A & Creatinine.

•ELECTROLYTES : sodium, calcium, potassium, Chloride &

bicarbonate.

•CELLULAR CONTENT : mainly lymphocytes 1000-2000 per cu mm

96% water 4% solids96% water 4% solids

RATE OF LYMPH FLOW

•T

otal estimated lymph flow is 120 ml / hr

•A

bout 100 ml flows through Thoracic duct in resting, per hour

•A

pprox 20 ml flow into circulation through other channels

•3

– 4 liters / day

Lymphoid Cells•Lymphocytes are the main cells involved in the immune response •Two main varieties:

T cells

B cells

•T cells and B cells protect the body against antigens NOTE= Antigen – anything the body perceives as foreign

-Bacteria and their toxins; viruses

-Mismatched RBCs or cancer cells

•T cells -

Manage the immune response -

Attack and destroy foreign cells•B cells

-Produce plasma cells, which secrete antibodies

-Antibodies immobilize antigens

Other Lymphoid Cells Macrophages – phagocytize foreign substances and help activate T cells

Dendritic cells – spiny-looking cells with functions similar to macrophages

Reticular cells – fibroblast–like cells that produce a stroma, or network, that supports other cell types in lymphoid organs

Lymphoid Tissue•Diffuse lymphatic tissue – scattered reticular tissue elements in every body organ.

• Larger collections appear in the lamina propria of mucous membranes and lymphoid organs.

•Lymphatic follicles (nodules) – solid, spherical bodies consisting of tightly packed reticular elements and cells.

• Germinal center composed of dendritic and B cells

• Found in isolation and as part of larger lymphoid organs

LYMPHOID ORGANS

Primary or Central

lymphocytes are produced and undergo development and are supplied to secondary organs.

Thymus

Bone marrow

Secondary or peripheral organs :

lymphocytes are activated to participate in specific immune response.

Lymph nodes

Spleen

Tonsils

LYMPHOID ORGANSLYMPHOID ORGANS

THYMUSTHYMUS

Primary organ of Lymphatic System.

Unpaired organ.

Consists of 2 pyramidal lobes..

Delicate & finely lobulated surface.

Located in mediastinum.

Extending :-

-Upwards - into neck as far as lower edge of thyroid gland

-Downwards - as far as fourth costal cartilage

Largest at puberty and weighs 35 to 40 gms - Pinkish grey.

Gradually atrophies in old age- yellowish in colour ( fat).

•Size of the thymus varies with age: -

In infants, it is found in the inferior neck and extends into the mediastinum where it partially overlies the heart

-It increases in size and is most active during childhood

-It stops growing during adolescence and then gradually atrophies

FUNCTIONS OF THYMUSFUNCTIONS OF THYMUS

- Thymus contains lobes divided into lobules.- Each lobule – cortex ( immature T lymphocytes, Macrophages) – medulla ( T lymphocytes, thymic corpuscels)

1) Processing the “T’’ Lymphocytes2) Endocrine functions Of Thymus They Secretes Hormones namely A) Thymosin B) Thymin C) Thymic Humoral Factor D) Thymulin

Figure 20.4a

Lymph Nodes -Principal lymphoid organs of the body

-Embedded in connective tissue and clustered along lymphatic vessels

-Aggregations of these nodes occur near the body surface in inguinal, axillary, and cervical regions of the body

•Two basic functions: -

Filtration – macrophages destroy microorganisms and debris

-Immune system activation – monitor for antigens and mount an attack against them

Structure of a Lymph Node

-Nodes are bean shaped and surrounded by a fibrous capsule

-Trabeculae extended inward from the capsule and divide the node into compartments

-Nodes have two histologically distinct regions: a cortex and a medulla

Structure of a Lymph Node -Cortex contains follicles with germinal centers, heavy with dividing B cells

-Dendritic cells nearly encapsulate the follicles

-Deep cortex houses T cells in transit

-T cells circulate continuously among the blood, lymph nodes, and lymphatic stream

Structure of a Lymph Node -Medullary cords extend from the cortex and contain B cells, T cells, and plasma cells

-Throughout the node are lymph sinuses crisscrossed by reticular fibers

-Macrophages reside on these fibers and phagocytize foreign matter

Structure of a Lymph Node

Figure 20.4a, b

Circulation in the Lymph Nodes -Lymph enters via afferent lymphatic vessels

-It then enters a large subcapsular sinus and travels into smaller sinuses

-It moves through these sinuses and exits the node at the hilus via efferent vessels

-Because there are fewer efferent vessels, lymph stagnates somewhat in the node

-This allows lymphocytes and macrophages time to carry out protective functions

FUNCTIONS OF LYMPH NODESFUNCTIONS OF LYMPH NODES

DEFENSE

A

s lymph passes through lymph Node reticuloendothelial cells

remove microorganisms & other injurious particles

HEMATOPOIESIS

Site for final stage of maturation of lymphocytes &

monocytes that have migrated from bone marrow

CLASSIFICATION OF LYMPH NODES CLASSIFICATION OF LYMPH NODES HORIZONTAL CHAIN - Outer circle

- Inner circle

VERTICAL CHAIN

level 1 consist of sub mental,

submandibular nodes

level 2 consist of upper jugular nodes

level 3 consist of middle jugular group

level 4 lower jugular group

level 5 posterior triangle group

level 6 anterior compartment group

level 7 superior mediastinal group

level 8 supraclavicular nodes

level 9 retropharyngeal nodes

LYMPHATIC DRAINAGE OF FACELYMPHATIC DRAINAGE OF FACE

U

pper part Parotid Lymph nodes

M

iddle part Submandibular lymph nodes

L

ower part Submental lymph nodes

Gingiva Submandibular lymph nodes

Hard palate Superficial deep cervical

and retropharyngeal

Soft palate Retropharyngeal

Floor of the mouth Submandibular and Submental

Teeth Submandibular and deep cervical

submental

Tonsil Jugulodigastric nodes

LYMPHATIC DRAINAGE OF MOUTH, LYMPHATIC DRAINAGE OF MOUTH, TEETH, TONSILTEETH, TONSIL

Tip Submental

Anterior 2/3rds Submandibular & deep cervical

Posterior 1/3rd Jugulodigastric lymph nodes

LYMPHATIC DRAINAGE OF TONGUE

LYMPHATIC DRAINAGE OF PARANASAL AIR SINUSES

FRONTAL SINUS SUBMANDIBULAR NODES

MAXILLARY SINUS SUBMANDIBULAR NODES

ETHMOIDAL SINUSES SUBMANDIBULAR NODES

SPHENOIDAL NODES RETROPHARYNGEAL NODES

Other Lymphoid Organs

-The spleen, thymus gland, and tonsils

-Peyer’s patches and bits of lymphatic tissue scattered in connective tissue

-All are composed of reticular connective tissue

-All help protect the body

-Only lymph nodes filter lymph

Spleen

-Largest lymphoid organ, located on the left side of the abdominal cavity beneath the diaphragm

-It is served by the splenic artery and vein, which enter and exit at the hilus

-Functions:S

ite of lymphocyte proliferationI

mmune surveillance and responseC

leanses the blood

Additional Spleen Functions

•Stores breakdown products of RBCs for later reuse.

• Spleen macrophages salvage and store iron for later use by bone marrow.

•Site of fetal erythrocyte production (normally ceases after birth).

•Stores blood platelets.

Structure of the Spleen•Surrounded by a fibrous capsule, it has trabeculae that extend inward and contains lymphocytes, macrophages, and huge numbers of erythrocytes

•Two distinct areas: -

White pulp – containing mostly lymphocytes suspended on reticular fibers and involved in immune functions

-Red pulp – remaining splenic tissue concerned with disposing of worn-out RBCs and bloodborne pathogens

Tonsils•Simplest lymphoid organs; form a ring of lymphatic tissue around the pharynx

•Location: -

Palatine tonsils – either side of the posterior end of the oral cavity

-Lingual tonsils – lie at the base of the tongue

-Pharyngeal tonsil – posterior wall of the nasopharynx

-Tubal tonsils – surround the openings of the auditory tubes into the pharynx

•Lymphoid tissue of tonsils contains follicles with germinal centers

•Tonsil masses are not fully encapsulated

Epithelial tissue overlying tonsil masses invaginates, forming blind-ended crypts

•Crypts trap and destroy bacteria and particulate matter

Aggregates of Lymphoid Follicles

Peyer’s patches – isolated clusters of lymphoid tissue, similar to tonsils

Found in the wall of the distal portion of the small intestine

Similar structures are found in the appendix

Peyer’s patches and the appendix: D

estroy bacteria, preventing them from breaching the intestinal wall

Generate “memory” lymphocytes for long-term immunity

MALT MALT – mucosa-associated lymphatic tissue:

Peyer’s patches, tonsils, and the appendix (digestive tract)

Lymphoid nodules in the walls of the bronchi (respiratory tract)

MALT protects the digestive and respiratory systems from foreign matter

Lymphography

-valuable tool for detection of lymphatic fistulas and lymphatic leakage

-Ethidiol

Lymphangioscintigraphy

-Tc-99m albumin –intradermally, and after 1 minute

and again after 10–30 minutes,

-High-resolution scintiscan camera

•Ultrasonography

•Computed Tomography

•PET

•MRI (MR lymphography)

•Fluorescein Microlymphangiography (isothiocynate)

•BIOPSY

INVESTIGATIONS

  Normal appearance of lymph nodes. (a) Lymphogram obtained during the filling phase shows a homogeneous appearance of the lymph nodes.

(b) Lymphogram obtained during the nodal phase shows a smooth peripheral indentation (arrowheads), which corresponds to the hilar area.

.

(A) (B)

  Normal appearance of the cisterna chyli. Lymphogram shows the cisterna chyli and the abdominal segment of the thoracic duct.

  Normal appearance of the thoracic duct. Lymphogram shows the termination of the thoracic duct at the left subclavian-jugular venous anastomosis at the base of the neck. At the termination, several powerful valves are seen.

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