the lymphatic system

consists of The lymph conducting channelsLymphoid tissues Lymphoid organs

The lymphatic system is part of the immune system and acts as a secondary (accessory) circulatory system.

Functions of the lymphatic system:• remove excess fluids from bo

dy tissues,• absorb fatty acid and transport fat to circulatory system, and• produce immune cells (lymphocytes, monocytes, and plasma cells).

Blood fluid escapes through the thin-walled capillaries into spaces between body tissue cells.

Lymph vessels, which have very thin walls, pick up these fluids called lymph.

Composition

• Lymphatic vessel

– Lymphatic capillary

– Lymphatic vessels: two sets, superficial and deep

– Lymphatic trunks: nine

– Lymphatic ducts: thoracic duct, right lymphatic duct

• Lymphatic organ

– Lymphatic nodes

– Tonsil, spleen, thymus

• Lymphatic tissue

• Include diffused lymphoid tissues and lymph nodules. They are mainly situated in the wall of the respiratory-alimentary tracts and consist of aggregated of lymphocytes and associates cells.

Tissue fluid and its formation

- composition same as blood but without read blood cells (RBCs), platelets & proteins

because they are too large to leak out of the capillaries

- forms a link between blood and cells, providing a medium for exchange of materials between blood & cells

At the arterial end of a capillary, liquid is forced out as tissue fluid which is similar to plasma in composition except its has no plasma proteins, platelets & RBCs.

 At the venous end, some fluid returns to blood while some enters lymph vessels which eventually join to a vein near the heart and thus returns to blood finally.

Lymph

some tissue fluid returns to capillaries by osmosis while

some (about 10%) goes into lymph capillaries;

this fluid is now called lymph

Path:

Blood lymph capillaries

lymph vessels

lymph ducts

Blood

- Lymph re-enters blood

Lymphatic capillary Begin blindly

• The wall is composed of a single layer of overlapping endothelial cells

• They are numerous and form complex networks

• The brain, spinal cord, bone marrow, parenchyma of spleen and eyeball lack lymphatic capillaries

Lymph is driven by contraction of surrounding muscles, aided by valves which enable one-way flow to the neck.

Movement of lymph through the lymphatic system:

1. Hydrostatic pressure

2. Muscle contraction

3. Inspiratory movement

4.Valves to ensure one-way traffic towards the heart

The Lymphatic SystemHeart

Artery

Capillaries

Vein

Cell Tissue fluid Lymphatic capillary Lymphatic vessel

Lymphatic node

Lymphatic trunk

Lymphatic duct

lymphatic vessels

• lymphatic capillary• lymphatic vessel• lymphatic trunks• lumbar trunks(2)• brochomediastinal trunks

(2)• subclavian trunks(2)• jugular trunks(2)• intestinal trunk

• lymphatic ducts• thoracic duct• right lymphatic duct

Lymphatic vessel

Features of structure Three layered wall similar

to, but thinner than vein, More numerous valves

than in vein Interposed by lymph node

at interval along the course Arranged in superficial and

deep sets

Lymphatic trunks right and left jugular trunk

s right and left subclavian tr

unks right and left bronchomedi

astinal trunks right and left lumbar trunk

s intestinal trunk

Right lymphatic duct Formed by union of right jugular, subclavia

n, and bronchomediastinal trunks Ends by entering the right venous angle Receives lymph from right half of head, neck,

thorax and right upper limb

Lymphatic ducts

Thoracic duct • Begins in front of L1 as a dilated sa

c, the cisterna chyli , which formed by joining of left and right lumbar trunks and intestinal trunk

• Enter thoracic cavity by passing through the aortic hiatus of the diaphragm and ascends along on the front of the vertebral column, between thoracic aorta and azygos vein

• Travels upward, veering to the left at the level of T5

• At the roof of the neck, it turns laterally and arches forwards and descends to enter the left venous angle

• Just before termination, it

receives the left jugular,

subclavian and bronchomediastinal

trunks

Thoracic duct

Thoracic duct

• Drains lymph from lower limbs, pelvic cavity, abdominal cavity, left side of thorax, and left side of the head, neck and left upper limb

Lymphatic vessel• Have valves that give them a beaded

appearance

• Two sets: superficial (lie in the superficial fascia ) and deep (run with blood vessels and nerves)

• Passes through at least one lymph node and often several

lymphatic ducts

• thoracic ductfrom cisterna chyli (L1) to left venous angles• left jugular trunk• left subclavian trunk• left bronchomediastinal trunk• right and left lumbar trunk • intestinal trunk right lymphatic duct

• right brochomediastinal trunk• right subclavian trunk• right jugular trunk

The lymph vessels join to form larger ducts that pass through lymph nodes (or glands).

Each lymph node has a fibrous outer covering (capsule), a cortex, and a medulla.

lymph node (Small oval or bean-shaped bodes• Afferent vessels enter the node on i

ts convex surface, and efferent vessels leave the node at its concave surface － the hilum

• Arranged in groups, along the blood vessels

• Regional nodes• is the lymph node where the ly

mph of the organ or part of the body drainage to firstly

Photo from U. S. Federal Government courtesy of Wikipedia.

Lymph nodes filter foreign substances, such as bacteria and cancer cells, from the lymph before it is re-entered into the blood system through the larger veins.

Lymph nodes, which are scattered among the lymph vessels, act as the body’s first defense against infection.

Lymph nodes produce the following cells:• Lymphocytes – a type of white blood cell,• Monocytes – a leukocyte that protects against blood-borne pathogens, and• Plasma cells – produce antibodies.

Each lymph node has its own blood supply and venous drainage.

The lymph nodes usually have names that are related to their location in the body.

When a specific location gets infected, the lymph nodes in that area will enlarge to fight the infection.

If the lymph node closest to an infected area is unable to eliminate the infection, other lymph nodes in the system will attempt to fight the infection.

This is particularly critical in the case of cancer, which can be spread from its point of origin to all parts of the body through the lymphatic system.

Lymph drainage of the body

The lymphatic drainage of head Lymph nodes of head

• Located at junction of head and neck• Consist of

– Occipital lymph nodes– Mastoid lymph nodes – Parotid lymph nodes ★ Submandibular lymph nodes

lies near the submandibular gland, receive lymphatic vessels from the face, nose and mouth

– submental lymph nodes• Drain into deep cervical lymph nodes

Lymph nodes of the neckAnterior cervical ln. • Superficial anterior cervical lymph

nodes

• Deep anterior cervical lymph nodes

Lateral cervical ln. ★ Superficial lateral cervical ln. － lie along the external jugular vein

★ Deep lateral cervical ln. － exten

d along the internal jugular vein

Lymph nodes of the neck★ Deep lateral cervical ln.

• Extend along the internal jugular vein from the base

of skull to the root of neck

• Divided into superior deep lateral cervical ln. and inferior deep lateral cervical ln.

• Receive lymphatic vessels from head, neck, tongue, larynx, cervical parts of esophagus and trachea, thyroid gland, upper parts of the thoracic wall and breast

• Efferent vessels form the jugular trunk– Left jugular trunk joins the thoracic duct

– Right jugular trunk joins the right lymphatic duct

Lymph nodes of the neckSuperior deep lateral cervical l

n. Jugulodigastric ln. – Lies at the junction of posterior belly of dig

astric and internal jugular vein– Drain the nasopharynx, palatine tonsil and r

oot of tongue

Inferior deep lateral cervical ln. Juguloomohyoid ln. – Lies at the junction of the intermediate tendo

n of omohyoid and internal jugular vein– Drain the apex of tongue

Lymph nodes of the neckInferior deep lateral cervical

ln. Supraclavicular lymph nodes

– Lie along transverse cervical a. & v.– palpable in the supraclavicular fossa.

The most notable supraclavicular lymph node is Virchow's node. which can contain metastasis of visceral (abdominal) tumor.

• Retropharyngeal ln. – Lying vertically behind the pharynx– drain nasopharyngeal lymph

Lymph nodes of upper limb• Cubital lymph node

• lies above medial epicondyle of humerus

• Receive lymph vessels from forearm

• Axillary lymph node

• arranged in five groups

Axillary lymph nodes

• Axillary lymph nodes vary i

n size from a pin-head to a l

arge bean.

• They are arranged in five gr

oups.

Axillary lymph nodes

Pectoral lymph nodes Lying along the lower border of pectoralis minor behind the pectoralis major

• Receive lymph vessels from the lateral quadrants of the breast and superficial vessels from the anterolateral abdominal wall above the level of the umbilicus

Axillary lymph nodes

Lateral lymph nodes Along medial side distal part of axillary vein

• Receives lymph from upper limb

Axillary lymph nodes

Subscapular lymph node

• Lying along subscapular vessels, in front of the subscapularis

• Receive superficial lymph vessels from the back, down as far as the level of the iliac crests

• Efferents of above three groups pass to central lymph node

Axillary lymph nodes

Central lymph node• Lying in the center of the axi

lla in the axillary fat

• Receive lymph from the above three nodes

• Efferents pass to apical lymph node

Axillary lymph nodes

Apical lymph node infraclavicular lymph no

des Lying at the apex of the axill

a at the lateral border of the fist rib

• Receive lymph of the efferent lymph vessels from all the other axillary nodes

• The efferents of the apical nodes form the subclavian trunk

Axillary lymph nodes

Lateral ln.

Pectoral ln.

Subscapular ln.

Central ln.

Apical ln.

Efferents form subclavian trunk, the right subclavian trunk joins the right lymphatic duct; left usually drains directly into thoracic duct

Subclavian trunk

Lymphatic drainage of thorax

The lymphatic drainage of thoracic wall

• To axillary lymph nodes

• To parasternal lymph nodes (along internal thoracic vessels)

• To intercostals lymph nodes from deeper structures

• The lymphatic and venous drainages of the breast are of great importance in the spread of carcinoma.

• About three quarters of the lymphatic drainage is to the axillary nodes: (1) Lymphatics pass around the edge of the pectoralis major and reach the pectoral group of axillary nodes;

• (2) routes through or between the pectoral muscles may lead directly to the apical nodes of the axilla;

• (3) lymphatics follow the blood vessels through the pectoralis major and enter the parasternal (internal thoracic) nodes;

• (4) connections may lead across the median plane and hence to the contralateral breast;

• (5) lymphatics may reach the sheath of the rectus abdominis and the subperitoneal and subhepatic plexuses.

• It should be noted that free communication exists between nodes below and above the clavicle and between the axillary and cervical nodes.

lymph nodes of the thorax• Pulmonary ln. lie in the angles of bif

urcation of branching lobar bronchi

• Bronchopulmonary hilar ln. － lie in the hilums of the lung

• Tracheobronchial ln. － situated above or below the bifurcation of trachea

• Paratracheal ln. － along each side of the trachea

lymph nodes of the thorax• Anterior mediastinal lymph no

de – Lies anterior to the large blood vessels of

thoracic cavity and pericardium– The efferents unite with those of paratrach

eal lymph nodes and parasternal lymph nodes to form the right and left bronchomediastinal trunks

– The left bronchomediastinal trunk terminates in thoracic duct, and right in the right lymphtic duct

• Posterior mediastinal lymph nodes lie along the esophagus and thoracic aorta

Lymph nodes of lower limb

Popliteal ln. • Embedded in the fatty connective tis

sue of popliteal fossa

• Receive superficial lymphatic vessels from posterolateral part of calf, and from deep lymphatic vessels accompanying anterior and posterior tibia a.

• Efferents pass to the deep inguinal ln.

Lymph nodes of lower limbSuperficial inguinal lymph nodes Su

perior group: – Lies just distal to the inguinal ligament

– Receive lymph vessels from anterior abdominal wall below umbilicus, gluteal region, perineal region, external genital organs

• Inferior group: – Lies vertical along the terminal great saphenous

v.

– Receives all superficial lymph vessels of lower limb, except for those from the posterolateral part of calf

– Efferent vessels drain into the deep inguinal ln. or external iliac ln.

Lymph nodes of lower limb

Deep inguinal lymph nodes• Lie medial to the femoral v.

• Receive deep lymph vessels of lower limb, perineal region, and efferent vessels from the superficial inguinal ln.

• Drain into the external iliac ln.

Lymph nodes of pelvis• Internal iliac lymph node

– Surround internal iliac vessels– Receive afferents from pelvic viscera, perine

um, buttock and back of thigh• External iliac lymph nodes

– Lie along external iliac artery– Receive afferents from lower limb and some

parts of pelvic viscera• Sacral lymph node locate along middle sacral a. and lateral sacral a. Receive lymph from posterior pelvic wall ,rectum,

prostate or uterus• Common iliac lymph node

– Lie along common iliac artery– Receive afferents from all the above nodes– Efferent pass to lumbar lymph node

Lymph nodes of abdomen

Lymphatic drainage of abdominal wall

• To axillary lymph node from region above umbilicus

• To superficial inguinal lymph node from region below umbilicus

• To lumbar lymph node from post wall of abdomen

Lymph nodes of abdomenLymphatic drainage of abdom

inal viscera• Lumbar lymph nodes

– Lie on posterior abdominal wall, along the abdominal aorta and inferior vena cava

– Receive lymph from kidneys, suprarenal glands, testes, ovaries, fundus of uterus, uterine tubes, and common iliac nodes

– Right and left lumbar trunks formed by efferent vessel

– Paired viscera － drain to the lumbar lymph nodes

Lymph nodes of abdomen• Right and left gastric ln. lie along

the same vessels and finally to the celiac ln.

• Right and left gastroomental ln. lie along the same vessels, the former drain into subpyloric ln., the latter drain into splenic ln.

• Suprapyloric and subpyloric ln. receive lymphatics from pyloric part and finally to the celiac ln.

• Splenic ln. receive lymphatics from fundus and left third of stomach, and finally to the celiac ln.

• Celiac lymph nodes － situated around the celiac trunk

Lymph nodes of abdomen

• Superior mesenteric lymph node － situated around superior mesenteric a.

• Inferior mesenteric lymph node － situated around inferior mesenteric a.

• Intestinal trunk － formed by efferent vessel of celiac, superior and inferior lymph nodes

Thymus

Featrues Consists of two elongated

lobesIs large organ in the fetusOccupies the thoracic cavi

ty behind the sternumSecrete lymphopoietin

Thymus The thymus is partly in the neck and partly in the thorax. It co

mprises one to three lobes, each of which consists of numerous lobules containing lymphocytes, which are important in the development and maintenance of the immune system. The cervical part of the thymus lies on the anterior and lateral sides of the trachea, whereas the thoracic part lies posterior to the superior portion of the sternum. The organ has a profuse blood supply and lymphatic drainage. The thymus reaches its greatest size at puberty and then begins to regress. Much of its substance is replaced by fat and fibrous tissue, but thymic tissue never disappears completely. Function:to develop lymph cell

Spleen• Shape– The largest single mass of

lymphoid tissue in the body

– Reddish in color

• Location: – lies in the left hypochondriac region

(between stomach and diaphragm) deep to the 9th to 11th rib

– its long axis corresponds roughly to the 10th rib

– Its lower pole extends forward only as far as the midline and cannot be palpated on clinical examination

Spleen • Two surfaces

– Diaphragmatic: smooth, convex

– Visceral: concave, hilum of spleen

• Two extremities – Anterior － wider

– Posterior － rounder

• Two border – Superior － has 2-3 splenic notch, which s

erve as a landmark on palpation when it is enlarge; normally it is not palpable

– Inferior － rounder

Spleen Function

Erythrocyte storagePhagocytosisCytopoiesisImmune responses