Lymphatic Drainage System: Anatomy

Overview

Immune system Immune system The body’s defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs

• The immune system Immune system The body’s defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs provides defense (immunity) against invading pathogens, ranging from viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology to parasites, and its components are interconnected by blood and the lymphatic circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment.
• 2 lines of defense Lines of Defense Inflammation (which overlap):
  • Innate immunity Innate immunity The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from the presence of naturally occurring anti-infective agents, constitutional factors such as body temperature and immediate acting immune cells such as natural killer cells. Innate Immunity: Phagocytes and Antigen Presentation (which is nonspecific) involves the following cells:
    • Natural killer cells Natural killer cells A specialized subset of T-lymphocytes that exhibit features of innate immunity similar to that of natural killer cells. They are reactive to glycolipids presented in the context of the major histocompatibility complex (MHC) class I-like molecule, CD1D antigen. Lymphocytes: Histology
    • Monocytes Monocytes Large, phagocytic mononuclear leukocytes produced in the vertebrate bone marrow and released into the blood; contain a large, oval or somewhat indented nucleus surrounded by voluminous cytoplasm and numerous organelles. Innate Immunity: Phagocytes and Antigen Presentation/ macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation
    • Dendritic cells Dendritic cells Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as skin and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process antigens, and present them to T-cells, thereby stimulating cell-mediated immunity. They are different from the non-hematopoietic follicular dendritic cells, which have a similar morphology and immune system function, but with respect to humoral immunity (antibody production). Skin: Structure and Functions
    • Neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation, basophils Basophils Granular leukocytes characterized by a relatively pale-staining, lobate nucleus and cytoplasm containing coarse dark-staining granules of variable size and stainable by basic dyes. Innate Immunity: Phagocytes and Antigen Presentation, eosinophils Eosinophils Granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing coarse, round granules that are uniform in size and stainable by eosin. Innate Immunity: Phagocytes and Antigen Presentation
    • Tissue mast cells Mast cells Granulated cells that are found in almost all tissues, most abundantly in the skin and the gastrointestinal tract. Like the basophils, mast cells contain large amounts of histamine and heparin. Unlike basophils, mast cells normally remain in the tissues and do not circulate in the blood. Mast cells, derived from the bone marrow stem cells, are regulated by the stem cell factor. Innate Immunity: Phagocytes and Antigen Presentation
  • Adaptive immunity (based on specific antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination recognition) involves:
    • T and B lymphocytes B lymphocytes Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions (derived from lymphoid organs Lymphoid organs A system of organs and tissues that process and transport immune cells and lymph. Primary Lymphatic Organs)
    • Antigen-presenting cells Antigen-presenting cells A heterogeneous group of immunocompetent cells that mediate the cellular immune response by processing and presenting antigens to the T-cells. Traditional antigen-presenting cells include macrophages; dendritic cells; langerhans cells; and B-lymphocytes. Follicular dendritic cells are not traditional antigen-presenting cells, but because they hold antigen on their cell surface in the form of immune complexes for b-cell recognition they are considered so by some authors. Adaptive Immune Response

Lymphatic system Lymphatic system A system of organs and tissues that process and transport immune cells and lymph. Primary Lymphatic Organs

The lymphatic system Lymphatic system A system of organs and tissues that process and transport immune cells and lymph. Primary Lymphatic Organs ( lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs vessels, lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs fluid, and lymphoid organs Lymphoid organs A system of organs and tissues that process and transport immune cells and lymph. Primary Lymphatic Organs) is part of the body’s immune system Immune system The body’s defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs.

• Lymphoid organs Lymphoid organs A system of organs and tissues that process and transport immune cells and lymph. Primary Lymphatic Organs:
  • Primary: 
    • Locations where lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology develop from progenitor cells (initial formation)
    • Include the bone marrow Bone marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. Bone Marrow: Composition and Hematopoiesis and thymus
  • Secondary: 
    • Sites where lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology undergo activation, proliferation and additional maturation
    • Include the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy, lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes, and MALT MALT Colon, Cecum, and Appendix: Anatomy (e.g., tonsils Tonsils Tonsillitis)
• Lymphatic vessels and ducts:
  • A network, similar to the blood vessels, that extends throughout the human body
  • Connect lymphoid organs Lymphoid organs A system of organs and tissues that process and transport immune cells and lymph. Primary Lymphatic Organs and transport interstitial fluid Interstitial fluid Body Fluid Compartments ( lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs) 
  • Play crucial roles in immune response and fluid balance

Lymph and Lymphatic Vessels

Structures

• Lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs: 
  • Fluid that enters the lymphatic vessels 
  • Originates from extracellular fluid Extracellular fluid The fluid of the body that is outside of cells. It is the external environment for the cells. Body Fluid Compartments and contains products of tissue metabolism and catabolism, apoptotic cells, debris, and immune cells
• Lymphatic capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology:
  • Permeable, blind-ended vessels (endothelial cells are not tightly joined)
  • Carry lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs from the tissues to the lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes via lymphatic vessels
  • Greater diameter (as wide as 100 μm) than blood capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology
  • Endothelial cells overlap each other, forming minivalves that can easily open.
  • Interstitial proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis cannot enter the blood capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology, but they can enter lymphatic capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology. 
• Lymphatic vessels (types):
  • Initial lymphatics:
    • No valves
    • No smooth muscles Smooth muscles Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. Muscle Tissue: Histology in the walls
    • Found in regions such as the intestines and skeletal muscles Skeletal muscles A subtype of striated muscle, attached by tendons to the skeleton. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles. Muscle Tissue: Histology
    • Fluid enters through junctions of endothelial cells, and muscle contractions (of organs and blood vessels) encourage fluid flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure.
    • Drain into the collecting lymphatics
  • Collecting lymphatics: 
    • With valves (the beaded appearance of lymphatic ducts and vessels reflects the presence of valves)
    • With smooth muscles Smooth muscles Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. Muscle Tissue: Histology in the walls
    • Muscle contractions in the lymphatic vessels move the fluid along the vessels.

Main functions

• Lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs transport and immune surveillance Surveillance Developmental Milestones and Normal Growth:
  • Pathogens, tumor Tumor Inflammation cells, and debris travel through the lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs.
  • Lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs is filtered, and the appropriate immune response is mounted in the lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes.
• Fluid homeostasis Homeostasis The processes whereby the internal environment of an organism tends to remain balanced and stable. Cell Injury and Death:
  • Increase in interstitial fluid Interstitial fluid Body Fluid Compartments volume and leaked protein molecules will cause fluid accumulation in tissue spaces ( edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema).
  • Lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology pick up excess or extravasated fluid (which forces the minivalves to open) and proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis, enabling return to circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment.
• Fat transport:
  • Fats Fats The glyceryl esters of a fatty acid, or of a mixture of fatty acids. They are generally odorless, colorless, and tasteless if pure, but they may be flavored according to origin. Fats are insoluble in water, soluble in most organic solvents. They occur in animal and vegetable tissue and are generally obtained by boiling or by extraction under pressure. They are important in the diet (dietary fats) as a source of energy. Energy Homeostasis and fat-soluble vitamins from the digestive system are absorbed.
  • Special lymphatic capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology in the small intestinal villi (lacteals) facilitate transport to the venous circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment. 
  • Lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs in lacteals: also called chyle (milky appearance due to fat content) 

Route of lymphatic drainage

• Unidirectional
• Lymphatic capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology → lymphatic vessels (enter lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes via afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology vessels and leave via efferent Efferent Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology vessels) → lymphatic ducts
• 1 major lymphatic duct on each side of the body: 
  • The right lymphatic duct drains from:
    • Right side of the body above the diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy (the right side of the head and neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, the right side of the thorax, and the right upper extremity)
    • Drains into the junction of the right subclavian and internal jugular vein Internal jugular vein Parapharyngeal Abscess
  • The thoracic duct (larger) drains from the rest (75%) of the body.
    • Drains lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs from both lower limbs, left upper limb, and left half of the head and neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess
    • Starts at the cisterna chyli, lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs sac at level of L2 vertebra 
    • Ascends into the thorax, going through the aortic hiatus Aortic hiatus Diaphragm: Anatomy of the diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy
    • Continues upward into the posterior mediastinum Posterior mediastinum Mediastinum and Great Vessels: Anatomy on the right, and then shifts to the left at T5 vertebra
    • Drains into the convergence Convergence Pupil: Physiology and Abnormalities between the left subclavian and internal jugular veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology

Lymphatic Drainage Associations

Lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy is caused by several etiologies, and an approach for determining the etiology is based on the location(s) of and areas drained by the lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs node(s).

Clinical Relevance

• Lymphedema Lymphedema Edema due to obstruction of lymph vessels or disorders of the lymph nodes. Lymphatic Filariasis (Elephantiasis): interstitial fluid Interstitial fluid Body Fluid Compartments colloid Colloid Colloid solutions include large proteins or cells that do not readily cross capillary membranes. They remain in the ecf and do not distribute into the icf (similar to crystalloids). Intravenous Fluids osmotic pressure Osmotic pressure The pressure required to prevent the passage of solvent through a semipermeable membrane that separates a pure solvent from a solution of the solvent and solute or that separates different concentrations of a solution. It is proportional to the osmolality of the solution. Intravenous Fluids increases, resulting in lymphedema Lymphedema Edema due to obstruction of lymph vessels or disorders of the lymph nodes. Lymphatic Filariasis (Elephantiasis). The lymphatic drainage serves as the main route for the removal of interstitial fluid Interstitial fluid Body Fluid Compartments. Dysfunction of the lymphatic vessels results in the development of edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship can present with peau d’orange Peau D’Orange Mastitis skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions changes and elephantiasis Elephantiasis Lymphatic filariasis, also known as elephantiasis, is a chronic mosquito-borne infection caused by Wuchereria bancrofti, Brugia malayi, and B. timori. The majority of causes are due to W. bancrofti. Mosquitos are the vectors, and humans are the primary reservoir. Patients with acute infection can present with fever, adenolymphangitis, dermatolymphangioadenitis, and tropical pulmonary eosinophilia. Lymphatic Filariasis (Elephantiasis). Causes occur from congenital hypoplasia Hypoplasia Hypoplastic Left Heart Syndrome (HLHS) of lymphatics (Milroy disease), malignancy Malignancy Hemothorax, obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity, or surgery.
• Chylothorax Chylothorax The presence of chyle in the thoracic cavity. Pleural Effusion: condition in which the thoracic duct is disrupted and chyle escapes into the pleural space Pleural space The thin serous membrane enveloping the lungs (lung) and lining the thoracic cavity. Pleura consist of two layers, the inner visceral pleura lying next to the pulmonary parenchyma and the outer parietal pleura. Between the two layers is the pleural cavity which contains a thin film of liquid. Pleuritis. The condition is commonly caused by trauma (e.g., thoracic surgery Thoracic Surgery Basic surgical intervention in the thoracic cavity has the primary goal of alleviating any malady that mechanically affects the function of the heart and lungs, which can be secondary to underlying pathologies or, most commonly, trauma. Interventions include tube thoracostomy, thoracentesis, and emergency thoracotomy. Thoracic Surgery) but also arises from tumors. Presentation includes dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea and a pleural effusion Pleural Effusion Pleural effusion refers to the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Pleural Effusion on chest radiograph. On thoracentesis Thoracentesis Aspiration of fluid or air from the thoracic cavity. It is coupled sometimes with the administration of drugs into the pleural cavity. Thoracic Surgery, a milky pleural fluid with an elevated triglyceride level is noted. Evaluation is by lymphangiogram and a mediastinal CT scan.
• Lymphangitis Lymphangitis A lymphatic disease characterized by inflammation of lymphatic vessels. Erysipelas: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the lymphatic vessels, often caused by bacterial spread. The most common etiology is group A β-hemolytic streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus. The vessels are dilated and filled with exudate Exudate Exudates are fluids, cells, or other cellular substances that are slowly discharged from blood vessels usually from inflamed tissues. Pleural Effusion. On examination, red subcutaneous streaks representing inflamed lymphatics are seen. This is accompanied by painful and enlarged lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes ( lymphadenitis Lymphadenitis Inflammation of the lymph nodes. Peritonsillar Abscess).