| Lymph Nodes |
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Lymph nodes (IPA: [ lɪmf noʊdz, lɪmf nəʊdz], are components of the lymphatic system. The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. They are found throughout the body. Lymph nodes act as filters or traps for foreign particles and contain white blood cells.
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Function
Nodes act as filters, with an internal honeycomb of reticular connective tissue filled with lymphocytes that collect and destroy bacteria and viruses. Older textbooks typically refer to elastic and reticular connective tissues as specialized connective tissues A lymphocyte is a type of White blood cell in the Vertebrate Immune system. When the body is fighting an infection, lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes. Lymphatic fluid in the tissues, before it has gone into a lymph node, is called interstitial fluid.
Structure
The lymph node is surrounded by a fibrous capsule, and inside the lymph node the fibrous capsule extends to form trabeculae. A trabecula (plural trabeculae. From Latin for small beam. is a small often microscopic tissue element in the form of a small beam Thin reticular fibers form a supporting meshwork inside the node.
The concave side of the lymph node is called the hilum. The afferent (which attach to the hilum) and efferent (which emerge from the opposite pole) lymphatic vessels allow lymph to enter and leave respectively. In Anatomy, lymph vessels are thin walled Valved structures that carry Lymph.
The parenchyma of the lymph node is divided into an outer cortex and an inner medulla. Parenchyma is a term used to describe a bulk of a substance It is used in different ways in Animals and in Plants. In Anatomy and Zoology the cortex ( Latin: "bark" "rind" "shell" or "husk" is the outermost (or "superficial"
Cortex
In the cortex, the subcapsular sinus drains to cortical sinusoids. The subcapsular sinus ( lymph path, lymph sinus, marginal sinus) is a region within the Lymph node immediately deep to the capsule that contains
The outer cortex and inner cortex have very different properties:
| Location | Name/description | Predominant lymphocyte | Has nodules? |
| outer cortex | nodular cortex | B cells | yes |
| deep cortex | juxtamedullary cortex or paracortex | T cells | no |
The cortex is absent at the hilum. B cells are Lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by Paracortex is the portion of a Lymph node immediately surrounding the cortex. T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity.
Medulla
There are two named structures in the medulla:
- The medullary cords are cords of lymphatic tissue, and include plasma cells and T cells
- The medullary sinuses (or sinusoids) are vessel-like spaces separating the medullary cords. Plasma cells (also called plasma B cells or plasmocytes) are cells of the Immune system that secrete large amounts of antibodies. T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. The Lymph flows into the medullary sinuses from cortical sinuses, and into efferent lymphatic vessels. Medullary sinuses contain histiocytes (immobile macrophages) and reticular cells. A histiocyte is a cell that is part of the human Immune system. A reticular cell produces Reticular fibers and surrounds the fibers with its Cytoplasm, which isolates the fiber from other components of the tissues or
Shape and size
Human lymph nodes are bean-shaped and range in size from a few millimeters to about 1-2 cm in their normal state. They may become enlarged due to a tumor or infection. White blood cells are located within honeycomb structures of the lymph nodes. Lymph nodes are enlarged when the body is infected due to enhanced production of some cells and division of activated T and B cells. In some cases they may feel enlarged due to past infections; although one may be healthy, one may still feel them residually enlarged.
Lymphatic circulation
Lymph circulates to the lymph node via afferent lymphatic vessels and drains into the node just beneath the capsule in a space called the subcapsular sinus. The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. The subcapsular sinus ( lymph path, lymph sinus, marginal sinus) is a region within the Lymph node immediately deep to the capsule that contains The subcapsular sinus drains into trabecular sinuses and finally into medullary sinuses. The sinus space is criss-crossed by the pseudopods of macrophages which act to trap foreign particles and filter the lymph. Pseudopods or pseudopodia (from the Greek word ψευδοπόδια, ψευδός "fake false" Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that The medullary sinuses converge at the hilum and lymph then leaves the lymph node via the efferent lymphatic vessel towards either a more central lymph node or ultimately for drainage into a central venous subclavian blood vessel, most via Virchow's node and Ductus Thoracicus. In Human anatomy, the subclavian veins are two large Veins one on either side of the body In Medicine ( Oncology) Virchow's node (or signal node) is an enlarged hard left supraclavicular Lymph node which can contain In human Anatomy, the thoracic duct (aka left lymphatic duct is an important part of the Lymphatic system &mdashit is the largest lymphatic vessel in the body Valves on the afferent side prevent backflow.
Lymphocytes, both B cells and T cells, constantly circulate through the lymph nodes. A lymphocyte is a type of White blood cell in the Vertebrate Immune system. B cells are Lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. They enter the lymph node via the bloodstream and cross the wall of blood vessels by the process of diapedesis. Leukocyte extravasation is the movement of Leukocytes out of the Circulatory system, towards the site of tissue damage or infection
- The B cells migrate to the nodular cortex and medulla.
- The T cells migrate to the deep cortex ("paracortex").
When a lymphocyte recognizes an antigen, B cells become activated and migrate to germinal centers (by definition, a "secondary nodule" has a germinal center, while a "primary nodule" does not). An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response Germinal centres (GC are areas within Lymph nodes where B lymphocytes rapidly divide and are an important part of the humoral immune response. When antibody-producing plasma cells are formed, they migrate to the medullary cords. Stimulation of the lymphocytes by antigens can accelerate the migration process to about 10 times normal, resulting in characteristic swelling of the lymph nodes.
The spleen and tonsils are large lymphoid organs that serve similar functions to lymph nodes, though the spleen filters blood cells rather than bacteria or viruses. The spleen is an organ found in all Vertebrate animals In humans the spleen is located in the abdomen of the body where it functions in the destruction of redundant Red For the structure in the Cerebellum, see Cerebellar tonsil. The tonsils are areas
Distribution
Humans have approximately 500-600 lymph nodes distributed throughout the body, with clusters found in the underarms, groin, neck, chest, and abdomen.
Lymph nodes of the human head and neck
- Cervical lymph nodes
- Anterior cervical: These nodes, both superficial and deep, lie above and beneath the sternocleidomastoid muscles. Cervical lymph nodes are Lymph nodes found in the neck Classification There are approximately 300 lymph nodes in the neck and they can be classified in many In Human Anatomy, the sternocleidomastoid (pronounced /ˌstɚ They drain the internal structures of the throat as well as part of the posterior pharynx, tonsils, and thyroid gland. In Anatomy, the throat is the anterior part of the Neck, in front of the vertebral column. The pharynx (plural pharynges) is the part of the Neck and Throat situated immediately Posterior to (behind the Mouth and Nasal For the structure in the Cerebellum, see Cerebellar tonsil. The tonsils are areas The thyroid is one of the largest Endocrine glands in the body
- Posterior cervical: These nodes extend in a line posterior to the sternocleidomastoids but in front of the trapezius, from the level of the Mastoid portion of the temporal bone to the clavicle. In Human anatomy, the trapezius is a large Superficial Muscle which extends longitudinally from the occipital bone to the lower thoracic vertebrae The Mastoid portion of the Temporal bone forms the posterior part of the temporal bone They are frequently enlarged during upper respiratory infections.
- Tonsillar: (sub mandibular) These nodes are located just below the angle of the mandible. The mandible (from Latin mandibula, "jawbone" or inferior maxillary bone forms the lower Jaw and holds the lower teeth in place They drain the tonsillar and posterior pharyngeal regions.
- Sub-mandibular: These nodes run along the underside of the jaw on either side. They drain the structures in the floor of the mouth.
- Sub-mental: These nodes are just below the chin. They drain the teeth and intra-oral cavity.
- Supraclavicular lymph nodes: These nodes are in the hollow above the clavicle, just lateral to where it joins the sternum. Supraclavicular lymph nodes are Lymph nodes found superior to the Clavicle, palpable in the Supraclavicular fossa. The sternum (from Greek στέρνον sternon, "chest" or breastbone) is a long flat Bone located in the center of the thorax (chest They drain a part of the thoracic cavity and abdomen. The thoracic cavity (or chest cavity) is the chamber of the human body (and other animal bodies that is protected by the Thoracic wall ( Thoracic cage Virchow's node is a left supraclavicular lymph node which receives the lymph drainage from most of the body (especially the abdomen) via the thoracic duct and is thus an early site of metastasis for various malignancies. In Medicine ( Oncology) Virchow's node (or signal node) is an enlarged hard left supraclavicular Lymph node which can contain In human Anatomy, the thoracic duct (aka left lymphatic duct is an important part of the Lymphatic system &mdashit is the largest lymphatic vessel in the body Metastasis ( Greek: displacement μετά=next + στάσις=placement, plural metastases) sometimes abbreviated mets,
Lymph nodes of the arm
These drain the whole of the arm, and are divided into two groups, superficial and deep. The superficial nodes are supplied by lymphatics which are present throughout the arm, but are particularly rich on the palm and flexor aspects of the digits.
- Superficial lymph glands of the arm:
- supratrochlear glands: Situated above the medial epicondyle of the humerus, medial to the basilic vein, they drain the C7 and C8 dermatomes. The humerus is a Long bone in the Arm or Forelimb that runs from the Shoulder to the Elbow. In Human anatomy, the basilic vein is a large Superficial vein of the Upper limb that helps drain parts of hand and Forearm. A Dermatome is an area of Skin associated with a pair of Dorsal roots from the spine
- deltoideopectoral glands: Situated between the pectoralis major and deltoid muscles inferior to the clavicle. The Pectoralis major (popularly known as pecs) is a thick fan-shaped muscle situated at the upper front ( Anterior) of the Chest wall Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the
- Deep lymph glands of the arm: These comprise the axillary glands, which are 20-30 individual glands and can be subdivided into:
- lateral glands
- anterior or pectoral glands
- posterior or subscapular glands
- central or intermediate glands
- medial or subclavicular glands
Lower limbs
Pathology
- Further information: Lymphadenopathy
Lymphadenopathy is a term meaning "disease of the lymph nodes. The Axillary lymph nodes are of large size vary from twenty to thirty in number and may be arranged in the following groups Brachial lymph nodes (or "lateral" The superficial inguinal lymph nodes form a chain immediately below the Inguinal ligament. The deep inguinal lymph nodes are located medial to the Femoral vein and under the Cribriform fascia. Lymphadenopathy is a term meaning "disease of the Lymph nodes. " It is, however, almost synonymously used with "swollen/enlarged lymph nodes". In this case, the lymph nodes are palpable, and is a sign of various infections and diseases.
Additional images
 Lymphatic system |
 The human lymphatic system |
 Section of small lymph node of rabbit. X 100. |
 Lymphatics of the arm |
 Lymphatics of the axillary region |
 Transverse section of human vermiform process. X 20. |
 Section of mucous membrane of human rectum. X 60. |
See also
External links
Adenitis is a general term for an Inflammation of a gland or Lymph node. Lymphadenectomy consists of the surgical removal of one or more groups of Lymph nodes. Lymphoma a type of Neoplasm that originates in Lymphocytes (a type of White blood cell in the vertebrate Immune system) Hematological malignancies are the types of Cancer that affect Blood, Bone marrow, and Lymph nodes As the three are intimately connected through Western Kentucky University ( WKU) is a public university in Bowling Green Kentucky, USA For similarly-named academic institutions see Education in Boston MA.Dictionary
lymph node
-noun
- (anatomy, immunology) Small oval bodies of the lymphatic system, distributed along the lymphatic vessels, that are clustered in the armpits, groin, neck, chest and abdomen. They act as filters, with an internal honeycomb of connective tissue filled with lymphocytes and macrophages that collect and destroy bacteria, viruses and foreign matter from lymph. When the body is fighting an infection, these lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes.
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