Dr. Ahmed Osman

Human Biology 2

Lymphatic system

•Definition•Function of lymph (nodes)•Dynamics of circulation•Role in dental practice•Clinical applications (Regional lymph nodes).

As blood flows through the capillaries of the body, two opposing forces are exerted.

Blood pressure tends to force fluid through the walls of the capillaries into the tissue spaces, whereas the osmotic pressure osmotic pressure of the blood tends to draw fluid into the vessels.

Lymphatic system

• Fluid tends to pass out of vessels on the arterial side.

• About 90% of this fluid returns to the blood vessels, the remaining 10% entering lymph vessels that eventually carry this lymph back to the venous circulation after passing through the lymph nodes.

Lymphatic system

The lymphatic system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph (from Latin lympha "water") in a unidirectional pathway.

The widely and extensively dispersed vessel system collects tissue fluids from all regions of the body to eventually convey them towards the heart.

Lymphatic tissue is a specilized connective tissue - reticular connective, that contains large quantities of lymphocytes(filter fluids prior to adding it to circulation).

It transports immune cells to and from the lymph nodes in to the bones

The lymph transports antigen-presenting cells (APCs), such as dendritic cells, to the lymph nodes where an immune response is stimulated.

works with the circulatory system to deliver nutrients, oxygen, and hormones from the blood to the cells that make up the tissues of the body.

It absorbs and transports fatty acids and fats as chyle to the circulatory system

• It is responsible for the removal of interstitial fluid from tissues i.e. act as "drains" to collect the excess fluid and return it to the venous blood just before it reaches the heart preventing massive edema (which can cause tissue destruction: “pressure necrosis”). •Returns back to circulation, the protiens that may have escaped into interstitial spaces.

Circulation at the rate of 125 mL/hour.

The “pump” is: breathing & muscle contractions

A sound knowledge of the regional lymph nodes of the head and neck is very important for dentists because it is a reliable guide towards the origin of problem, and because of the possible involvement of

the lymphatic system in the spread of infection or the spread of malignant tumour cells (metastasis).

Role in headache?

Clinical significance:1. Diagnostic value2. Aid in prediction of treatment outcome

(modification of treatment plan/course)

3. Prediction of disease history and therefore prognosis.

4. Lymph vessels can also transmit other substances such as injected material or neoplastic cells.

Classification of nodes in head and neck region

The lymph nodes in the head and neck region can be grouped into:

• Superficial nodes

• Deep nodes.

Classification of nodes in head and neck region

The superficial cervical lymph nodes lie above the investing layer of the above the investing layer of the deep fasciadeep fascia.

They consist of a few small nodes that lie superficial to the external jugular and anterior jugular veins.

1. Submental2. Submandibular 3. Buccal4. Parotid (pre-auricular)5. Mastoid (retro auricular/ post-

auricular)6. Occipital7. Superficial cervical8. Anterior cervical.

Superficial Superficial cervical nodescervical nodes

1. Upper deep cervical

2. Lower deep cervical

3. Waldyer’s ring

4. Nodes of midline

The upper deep cervical (Jugulo-digastric group: lie along the upper part of internal jugular vein deep to the sternomastoid.

The lower deep cervical (jugulo-omohyoid gp): arranged along the lower part of IJV also deep to the SMm.

Deep cervical nodes

Deep cervical nodes

The waldyer’s ring is formed by: lingual, palatine, tubal, and pharyngeal tonsils.

Midline nodes are termed in correspondence to the anatomical area where they exist:

A. Infrahyoid

B. Prelaryngeal

C. Pretracheal

D. Paratracheal

Efferents of lower deep cervicals then collect into larger lymph vessel called the “jugular lymph trunk”.

This trunk joins another two lymph trunks lymph (subclavian and brachiocephalic trunks) to form the so called the “lymph ducts” (right or left).

This “duct” finally opens into the angle between internal jugular and subclavian veins to drain its contents back to venous circulation.

The right and left lymph ducts are NOT of equal size.

The left lymph duct (also called the “Thoracic duct” )

which is considered the largest lymphatic vessel in the body.

It collects most of the lymph in the body (except that from the right arm and the right

side of the chest, neck and head, which is collected by the right lymphatic duct).

Thoracic duct

• It begins down as low as level of L2

(at the cisterna chyli) and extends upward to drain into the region near the junction of the left subclavian and internal jugular veins, with tributaries from the cervical, subclavian and mediastinal trunks.

Thoracic duct

Lymphatic drainage

600-700 lymph nodes present in the average human body

The first sign of a malignancy (especially an intra-abdominal one) may be an enlargement of the lymph node that lies in the left supraclavicular area, in the vicinity where the thoracic duct empties into the left subclavian vein (Virchow’s node).

When the thoracic duct is blocked or damaged a large amount of lymph can quickly accumulate in the pleural cavity,

(Chylothorax).

Clinical applications

• The scalp drains into the occipital, mastoid and parotid nodes.

• Lower eye lid and anterior cheek drains into buccal LNs.

• The cheeks drain into the parotid, buccal and submandibular nodes.

• The upper lips and sides of the lower lips drain into the submandibular nodes.

While the middle third of the lower lip drains into the submental nodes

• The skin of the neck drains into the cervical nodes.

• The gingivae drain into the submandibular, submental and upper deep cervical lymph nodes.

• The palate drains via lymph vessels that pass through the pharyngeal wall to the upper deep cervical nodes.

• Teeth drain into the submandibular and deep cervical lymph nodes.

• Anterior part of mouth floor drain into submental and upper deep cervical while posterior part into submandibular and upper deep cervical.

Drainage of oral structures

Drainage of oral structures

• In relation to the lymph drainage of the tongue, the farther backward the origin of the vessel, the lower down is the lymph node in which it ends.

• Lymph vessels in the floor of the mouth pierce the mylohyoid muscle and travel to the submental and submandibular lymph nodes.

• Some medially located lymphatics in the tongue also cross the midline.

Lymphatic drainage of tongue

Lymphatic drainage of tongue

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