The secondary lymphoid organs Lymphoid organs A system of organs and tissues that process and transport immune cells and lymph. Primary Lymphatic Organs, also called peripheral lymphoid/lymphatic organs, include MALT MALT Colon, Cecum, and Appendix: Anatomy, the lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 - 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy, and 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. These collections of lymphoid tissues provide constant surveillance Surveillance Developmental Milestones and Normal Growth for pathogens. In their distinct sites, these tissues are filled with immune cells ready to mount a response when antigens are detected. Lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 - 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy are seen along lymphatic vessels Lymphatic Vessels Tubular vessels that are involved in the transport of lymph and lymphocytes. Lymphatic Drainage System: Anatomy and occur as chains or groups ( neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, groin Groin The external junctural region between the lower part of the abdomen and the thigh. Male Genitourinary Examination, axillae, mesenteries, abdomen). MALTs act as immune sensors situated in locations where the lumen is exposed to the external environment ( oropharynx Oropharynx The middle portion of the pharynx that lies posterior to the mouth, inferior to the soft palate, and superior to the base of the tongue and epiglottis. It has a digestive function as food passes from the mouth into the oropharynx before entering esophagus. Pharynx: Anatomy, GI tract, genitourinary tract). 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 is the site of production of antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions and 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, but it also aids AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS in the breakdown of platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology and erythrocytes Erythrocytes Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology.
Last updated: 9 Mar, 2022
The lymphatic system Lymphatic system A system of organs and tissues that process and transport immune cells and lymph. Primary Lymphatic Organs ( lymph vessels Lymph vessels Tubular vessels that are involved in the transport of lymph and lymphocytes. Lymphatic Drainage System: Anatomy, lymph fluid Lymph fluid The interstitial fluid that is in the lymphatic system. Lymphatic Drainage System: Anatomy, 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.
Anatomy of the
lymphatic system
Lymphatic system
A system of organs and tissues that process and transport immune cells and lymph.
Primary Lymphatic Organs:
Includes the primary (
bone
Bone
Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy.
Bones: Structure and Types marrow,
thymus
Thymus
A single, unpaired primary lymphoid organ situated in the mediastinum, extending superiorly into the neck to the lower edge of the thyroid gland and inferiorly to the fourth costal cartilage. It is necessary for normal development of immunologic function early in life. By puberty, it begins to involute and much of the tissue is replaced by fat.
Lymphatic Drainage System: Anatomy) and secondary (
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 nodes
Lymph Nodes
They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system.
Lymphatic Drainage System: Anatomy, and
MALT
MALT
Colon, Cecum, and Appendix: Anatomy)
lymphoid organs
Lymphoid organs
A system of organs and tissues that process and transport immune cells and lymph.
Primary Lymphatic Organs
Lymphatic vessels
Lymphatic Vessels
Tubular vessels that are involved in the transport of lymph and lymphocytes.
Lymphatic Drainage System: Anatomy convey lymph to the larger
lymphatic vessels
Lymphatic Vessels
Tubular vessels that are involved in the transport of lymph and lymphocytes.
Lymphatic Drainage System: Anatomy in the torso, transporting fluid back to the venous
circulation
Circulation
The movement of the blood as it is pumped through the cardiovascular system.
ABCDE Assessment.
Lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy and the lymphatic system Lymphatic system A system of organs and tissues that process and transport immune cells and lymph. Primary Lymphatic Organs
Image: “Blausen 0623 LymphaticSystem Female” by Blausen. License: CC BY 3.0The main function of lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy is defense against the spread of microorganisms and tumor Tumor Inflammation cells:
Histologic section of a lymph node, identifying the capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides and the trabeculae
Image by Geoffrey Meyer, edited by Lecturio.Illustration of a lymph node cross section:
Red and blue denote
arteries and veins
Arteries And Veins
ACES and RUSH: Resuscitation Ultrasound Protocols, respectively. Yellow arrows indicate lymph
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.
Af
AF
Atrial fibrillation (AF or Afib) is a supraventricular tachyarrhythmia and the most common kind of arrhythmia. It is caused by rapid, uncontrolled atrial contractions and uncoordinated ventricular responses.
Atrial Fibrillation:
afferent
Afferent
Neurons which conduct nerve impulses to the central nervous system.
Nervous System: Histology vessels
Ef
EF
Cardiac Cycle:
efferent
Efferent
Neurons which send impulses peripherally to activate muscles or secretory cells.
Nervous System: Histology vessels
F: follicle
IS: intermediate sinuses
LL: lymphatic labyrinth
MS
MS
Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that leads to demyelination of the nerves in the CNS. Young women are more predominantly affected by this most common demyelinating condition.
Multiple Sclerosis: medullary sinuses
SS
SS
Scleroderma (systemic sclerosis) is an autoimmune condition characterized by diffuse collagen deposition and fibrosis. The clinical presentation varies from limited skin involvement to diffuse involvement of internal organs.
Scleroderma: subcapsular sinuses
Histologic section of the lymph node showing the cortex, paracortex, and medulla
Image by Geoffrey Meyer, edited by Lecturio.Structure and functional regions of a lymph node comprising a collagen-rich
fibrous
Fibrous
Fibrocystic Change
capsule
Capsule
An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides.
Bacteroides and an underlying subcapsular sinus (SCS).
Cells are segregated into (1) the cortex (consisting of
B cells
B cells
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, T
follicular helper cells
Follicular helper cells
A specialized subpopulation of CD4+ T cells involved in formation of germinal center. Tfh cells are mostly located in secondary lymphoid organs, e.g., tonsil; spleen and lymph nodes. They are CD4 antigen; CD45 antigen; b-cell lymphoma 6 protein; cxcr5 receptors; icos inducible t-cell co-stimulator; and pd1 receptor positive.
T cells: Types and Functions, and
follicular dendritic cells
Follicular dendritic cells
Non-hematopoietic cells, with extensive dendritic processes, found in the primary and secondary follicles of lymphoid tissue (the B cell zones). They are different from conventional dendritic cells associated with T-cells. They are derived from mesenchymal stem cells and are negative for class II mhc antigen and do not process or present antigen like the conventional dendritic cells do. Instead, follicular dendritic cells have fc receptors and C3b receptors that hold antigen in the form of antigen-antibody complexes on their surfaces for long periods for recognition by B-cells.
MALT Lymphoma arranged in primary follicles, in which
B cells
B cells
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 survey antigens presented on the follicular dendritic cell stromal network); and (2) the paracortex (accommodates
T cells
T cells
Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.
T cells: Types and Functions,
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, and fibroblastic reticular cells, which form stromal cell networks and reticular fibers).
The inner medulla is composed of lymphatic tissues (medullary cords) separated by medullary sinuses consisting of lymph.
Lymph node vascular structure:
Consists of blood vessels (BVs), high endothelial
venules
Venules
The minute vessels that collect blood from the capillary plexuses and join together to form veins.
Veins: Histology (HEVs), and
lymphatic vessels
Lymphatic Vessels
Tubular vessels that are involved in the transport of lymph and lymphocytes.
Lymphatic Drainage System: Anatomy (LVs).
Blood vessels can be found throughout the whole lymph node, with specialized HEVs located within the T-cell areas. High endothelial
venules
Venules
The minute vessels that collect blood from the capillary plexuses and join together to form veins.
Veins: Histology are specialized BVs that orchestrate extravasation of
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 into the lymph node.
Afferent
Afferent
Neurons which conduct nerve impulses to the central nervous system.
Nervous System: Histology LVs enter the lymph node, where they transit into sinuses that ultimately exit via the
efferent
Efferent
Neurons which send impulses peripherally to activate muscles or secretory cells.
Nervous System: Histology LV.
Histologic section of a lymph node showing an afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology vessel
Image by Geoffrey Meyer, edited by Lecturio.Histologic section of a lymph node showing an efferent Efferent Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology vessel
Image by Geoffrey Meyer, edited by Lecturio.Mount an immune response against pathogens encountered in the mucosa of the GI, respiratory, and genitourinary tracts.
Tonsils
Tonsils
Tonsillitis in the oropharyngeal area, front view:
Pharyngeal, palatine and lingual
tonsils
Tonsils
Tonsillitis
Tonsils
Tonsils
Tonsillitis in the oropharyngeal area, side view:
Pharyngeal, palatine, and lingual
tonsils
Tonsils
Tonsillitis.
The tubal
tonsils
Tonsils
Tonsillitis (not pictured) are in the area of the
nasopharynx
Nasopharynx
The top portion of the pharynx situated posterior to the nose and superior to the soft palate. The nasopharynx is the posterior extension of the nasal cavities and has a respiratory function.
Pharynx: Anatomy.
Cross section of a tonsil (left) and close up of the bottom of a tonsillar crypt (right).
On the right, a lymphatic
nodule
Nodule
Chalazion (activated lymphoid tissue) can be seen very close to the bottom of the crypt.
Histologic section of the ileum Ileum The distal and narrowest portion of the small intestine, between the jejunum and the ileocecal valve of the large intestine. Small Intestine: Anatomy showing Peyer’s patches Patches Vitiligo
Image by Geoffrey Meyer.Cross section of an
appendix
Appendix
A worm-like blind tube extension from the cecum.
Colon, Cecum, and Appendix: Anatomy:
Lymphoid nodules can be seen reacting to an
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination from the lumen.
Cross section of
stomach
Stomach
The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus.
Stomach: Anatomy mucosa showing inactive lymphoid tissue (left) and cross section of intestine mucosa showing active lymphoid tissue (right):
Lymphoid tissues stand guard until they are activated and form nodules, with germinal centers.
Diagram of 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 (from left to right):
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 is a highly vascularized organ in the LUQ of the abdomen.
The
hilum
Hilum
Lungs: Anatomy is the area where the splenic artery enters and the splenic vein leaves 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. A cross section of 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 would show that the majority of the splenic parenchyma contains the red pulp (filled with all types of blood cells). The white pulp contains mainly lymphoid nodules and the periarteriolar lymphoid sheaths (PALS), which surround the central arteriole.
Cross section of a
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:
In a gross specimen, the white pulp and red pulp can be identified and differentiated owing to their difference in color and placement. White pulp agglomerates around blood vessels, while red pulp makes up the rest of the parenchyma.
Histologic section of 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:
The periarterial lymphoid sheath (PALS) engulfs a central arteriole. A lymphoid
nodule
Nodule
Chalazion has formed, surrounded by
T cells
T cells
Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.
T cells: Types and Functions, indicating that an
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination was detected in the splenic blood supply and an immune response was initiated.