What are the lymph nodes?
The lymph nodes are pinhead- to bean-sized organs located mainly in the neck, armpits, groin, chest and abdominal cavity. Linked by the lymphatic vessels, they form a widespread net throughout the body. They filter microbes, cancerous cells and foreign particles from the body fluid called lymph and are therefore a part of the body’s immune system.
Shape and Size
The lymph nodes appear as small balls that have a bean-like shape. Normal nodes around the ears, on the inner sides of the elbows and behind the knees can be as small as few millimeters, while those in the groin can reach 1.5 centimeters . In some healthy older children, the lymph nodes in the neck and armpits can be palpated, while in healthy adults, except in some very skinny ones, they usually can not be . Normal lymph nodes are usually not visible.
Swollen lymph nodes can measure from about 1 to more than 5 cm . Swollen nodes in the neck, around the ears, at the back of the head, in the armpits and groin can be visible and palpated. Under the fingers, they appear as soft or firm lumps with well defined borders.
The lymph node has the pulp-like center covered by the capsule.
The capsule is composed of dense connective tissue. A quick expansion of the lymph node, for example, during an acute infection, results in a capsule stretch, which causes pain.
The cortex homes the lymphoid follicles, which contain mainly B lymphocytes .
The paracortex contains mainly T lymphocytes.
The medulla contains mainly macrophages (which ingest foreign particles) and plasma cells (which are derived from B lymphocytes and produce antibodies, which are spread via the blood and fight microbes all over the body).
The lymph is composed of the fluid that is derived from the blood plasma–it appears around the cells (interstitial fluid)–and from the lymphocytes. The lymph is delivered to the lymph nodes via the lymphatic vessels.
The afferent lymphatic vessels drain the lymph from a certain area, for example, the afferent vessels of the submandibular nodes drain the lymph from the mouth and the facial skin.
Within the lymph node, the lymph flows through the system of sinuses and present microbes and other foreign particles to the lymphocytes.
The efferent lymphatic vessels collect the lymph from the lymph nodes and deliver it to the subsequent nodes. For example, the efferent vessels from the popliteal nodes behind the knee deliver the lymph to the inguinal nodes in the groin. Eventually, all the lymph drains into the subclavian veins, either directly, but mostly via the right lymphatic or left lymphatic (thoracic) duct in the chest cavity and via the jugular trunk in the neck.
The lymph nodes have their own arteries, which deliver the blood with the nutrients and lymphocytes to them [14,22]. The blood leaves the lymph nodes via the veins.
The lymph nodes filter the lymph: they remove and destroy bacteria, viruses, parasites, fungi, cancer cells and foreign particles from it .
The roles of different cells in the lymph nodes:
- B lymphocytes produce antibodies.
- T lymphocytes directly destroy microbes and foreign particles.
- Macrophages ingest microbes and foreign particles and present them to the lymphocytes.
The lymph nodes filter the lymph in a similar way in which the spleen filters the blood. The lymph nodes do not remove toxins and drugs from the body as the liver and kidneys do. The lymph nodes are the only organs that filter the lymph.
Together with the spleen, bone marrow, tonsils, thymus, the lymphatic tissue in the small intestine and white blood cells (leukocytes), the lymph nodes form the human’s immune system, which fights against infections.
There are hundreds of lymph nodes in the human body. They appear in groups, mainly in the neck, under the jaw, around the ears, at the back of the head, in the armpits, groin, chest and abdominal cavity and on the inner sides of the elbows and knees.
Chart 1. Lymph Node Locations
|HEAD||Preauricular and parotid, Retroauricular, Occipital, Submental, Submandibular|
|NECK||Anterior superficial, Posterior superficial, Anterior deep, Superior deep, Inferior deep|
|CHEST||Bronchopulmonary, Mediastinal, Hilar|
|ABDOMEN||Iliac, Lumbar, Sacral, Retroperitoneal, Mesenteric|
Preauricular and Parotid Nodes
- Preauricular nodes: in front of the auricle at the level of the tragus
- Parotid nodes: in front and below of the auricle, over the parotid gland
Drainage: the skin at the temples and front of the head, the front side of the ear’s auricle, external ear canal, lateral two thirds of the eyelids and conjunctiva, the root of the nose [3,4,5,6,7,16-s.105]
Efferent lymphatic vessels lead to the anterior superficial or superior deep cervical nodes [16,17].
Retroauricular (Mastoid) Nodes
Location: behind the bottom of the auricle
Drainage: the back side of the auricle, external ear canal, skin from the temples and top of the head [6,7]
Efferent lymphatic vessels lead to the superior deep cervical nodes [1,16].
Location: at the base of the skull, at the back of the head near the hairline
Drainage: the scalp at the back of the head 
Efferent lymphatic vessels lead to the superior deep cervical nodes .
Location: under the chin
Drainage: the tip of the tongue, the front part of the mouth floor, the front lower teeth (incisors) and the related part of the gums, the skin of the chin and the medial third of the lower lip [7,8].
Efferent vessels lead to the submandibular and deep cervical nodes .
Location: under and medially to the jawline (NOTE: medially to the submandibular nodes, there are submandibular salivary glands)
Drainage: the skin on the cheeks, sides of the nose and below the jaw, the medial third of the eyelids and eye’s conjunctiva, the front half of the nasal cavity, paranasal sinuses (maxillary, frontal and ethmoid sinuses), upper lip, lateral 2/3 of the lower lip, upper and lower teeth and gums except lower incisors, lateral parts of the front 2/3 of the tongue, sides and palate of the mouth, submandibular salivary glands and the submental nodes [1,3,6,7,8,16]
Efferent vessels lead to the superior deep cervical nodes .
Retropharyngeal nodes lie between the pharynx and spine and cannot be palpated. They drain the nasal cavity, the nasal part of the pharynx and the auditory tubes . The efferent vessels lead to the superior deep cervical glands .
Lateral Superficial Cervical Nodes
Location: over the sternocleidomastoid muscle (which extends from the mastoid process behind the ear diagonally down toward the sternum and clavicle), along the external jugular vein
- The skin of the neck, parotid gland [4,6,7,8,9]
- The preauricular nodes 
Efferent vessels lead to the deep cervical nodes .
Anterior Superficial Cervical Nodes
Location: on the sides of the larynx and trachea, along the anterior jugular vein
Drainage: the larynx and trachea
The efferent lymph vessels probably lead to the deep cervical nodes.
Anterior Deep Cervical Nodes
Location: in the middle of the neck, in front of the larynx and trachea [8,26]
Drainage: the larynx, trachea and thyroid
The efferent lymphatic vessels lead to the superior deep cervical nodes [8,26].
Superior Deep Cervical (Jugular) Nodes
Location: Under the upper part of the sternocleidomastoid muscle, along the internal jugular vein 
- The posterior third of the nasal cavity, paranasal sinuses, mouth, larynx (voice box), the upper parts of the trachea and esophagus, thyroid gland, parotid glands [17,19,20,21]
- The scalp at the back of the head (via occipital nodes)
- The uppermost superior deep cervical or jugulodigastric node, which lies at the side of the neck just below the jaw angle, drains the posterior 2/3 of the tongue, pharynx and soft palate including the palatine tonsils [8,21].
The efferent vessels lead to the inferior deep cervical nodes.
Inferior Deep Cervical (Jugular) Nodes
Location: behind the posterior border of the lower part of the sternocleidomastoid muscle .
Drainage: the larynx, thyroid, esophagus, other head and neck nodes [16,17]
Efferent vessels lead to the jugular trunk in the neck and eventually to the thoracic duct, right lymphatic duct or subclavian vein .
Location: above the clavicles on both sides of the neck (in the supraclavicular fossa)
- Right: the mediastinum (the space between the lungs), esophagus, lungs
- Left: via the thoracic duct: the gastrointestinal and genitourinary tract
- Both: via the cervical nodes: the head and neck; via the axillary nodes: the breast; skin of the arm, chest and back
Efferent vessels lead to the jugular trunk, left (thoracic) or right lymphatic duct or subclavian vein .
Location: below the clavicle, between the deltoid and pectoralis major muscle.
- The upper lateral portions of the breast
- The radial side of the arm and palm and the thumb and index finger
- Axillary (armpit) lymph nodes
Efferent vessels lead to the subclavian trunk and eventually to the subclavian vein .
Location: in the armpits
Drainage: breasts, chest, upper back and abdominal wall above the belly button, arm, hand and fingers [1,3,10,14]
Efferent vessels lead to the infraclavicular and supraclavicular nodes, the subclavian lymphatic trunk and eventually to the subclavian vein [10,25].
Supratrochlear (Epitrochlear, Cubital) Nodes
Location: on the inner ulnar (pinky) side of the elbow 
Drainage: the pinky, ring and middle finger and the related parts of the hand and forearm 
Efferent vessels lead to the axillary nodes .
Location: around the division of the trachea into the bronchi ; and more laterally: bronchopulmonary nodes (before the lungs) and pulmonary (within the lungs) 
Location : in the chest, between the lungs
Drainage: the lungs, pleura, heart, pericardium, thymus, esophagus, trachea, bronchi 
Location: at the entrance of the bronchi into the lungs (hilum)
Drainage: the lungs, pleura, heart, pericardium, thymus, esophagus, trachea, bronchi 
- External and internal iliac nodes: along the external and internal iliac arteries in the groin and pelvis
- Mesenteric nodes: between the 2 layers of the mesentery – the membrane that attaches the intestine to the abdominal wall
- Lumbar (paraaortic, periaortic) and sacral nodes: in front of the lumbar and sacral spine
- Retroperitoneal nodes: at the back of the abdominal cavity
Drainage: abdominal organs (stomach, liver, gallbladder, pancreas, kidneys, intestine) and pelvic organs (bladder, prostate, testicles, uterus, Fallopian tubes, ovaries) 
Efferent vessels lead to the intestinal lymph trunk, cisterna chyli, left lymphatic duct (thoracic duct) [12,23] and, possibly, to the left supraclavicular (Virchow’s) node .
- Superficial nodes:
- Horizontal group: along the inguinal ligament, between the lower abdomen and thigh
- Vertical group: along the upper great saphenous vein on the upper inner side of the thigh
- Deep (femoral) nodes: along the femoral artery
- Superficial horizontal group: the abdominal wall below the belly button, retroperitoneal space (around the kidneys), penis and scrotum skin, anal canal, vulva and lower third of the vagina, perineum, buttocks and lower back [1,3,5]
- Superficial vertical group: penis, scrotum, thighs and–via the popliteal nodes–the lower legs
- Deep (femoral) nodes: the legs, penis, clitoris 
Efferent vessels lead to the external iliac nodes in the pelvis .
Location: at the back of the knee, in the popliteal fossa 
Drainage: the foot, lower leg and knee 
Efferent vessels lead to the deep and superficial inguinal nodes .
Lymph nodes can become swollen (enlarged) in [1,14]:
- Insect and snake bites
- Autoimmune disorders
- Long-term exposure to silicon or beryllium
- Genetic storage diseases
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