The primary lymphoid organs, also referred to as central lymphoid/lymphatic organs, are the tissues responsible for the production of lymphoid cells from progenitor cells, incuding 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 the 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. In 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, hematopoietic stem cells Hematopoietic stem cells Progenitor cells from which all blood cells derived. They are found primarily in the bone marrow and also in small numbers in the peripheral blood. Bone Marrow: Composition and Hematopoiesis progress to become oligopotent progenitors Oligopotent progenitors Bone Marrow: Composition and Hematopoiesis (in the case 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, the common lymphoid progenitor). 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 stay and undergo processes for differentiation before migrating to the secondary lymphoid organs (such as 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). The progenitor cells that are to become T lymphocytes T lymphocytes 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 proceed to the 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 for further maturation.
Last updated: 9 Mar, 2022
The lymphatic system ( 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) is part of the body’s immune system.
Anatomy of the lymphatic system:
Includes the primary (
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,
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
Lymphatic vessels
Lymphatic Vessels
Tubular vessels that are involved in the transport of lymph and lymphocytes.
Lymphatic Drainage System: Anatomy convey
lymph
Lymph
The interstitial fluid that is in the lymphatic system.
Secondary Lymphatic Organs 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.
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 is the spongy tissue found in the medullary canals Medullary canals Bone Marrow: Composition and Hematopoiesis of long bones Long bones Length greater than width. Bones: Structure and Types and cavities of the cancellous bones.
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:
Cross section showing the red and yellow marrow of the
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
Schematic representation of 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 microenvironment:
The hematopoietic stem cell (HSC) area contains the HSCs and uncommitted progenitors. These cells are in close association with endosteal
osteoblasts
Osteoblasts
Bone-forming cells which secrete an extracellular matrix. Hydroxyapatite crystals are then deposited into the matrix to form bone.
Bones: Development and Ossification and bone-lining cells. As HSCs change from quiescence to proliferative states, they migrate and colonize the subendosteal region and then the central region of the marrow (progenitors).
Differentiated cells reach the mature area, closer to the
sinusoids
Sinusoids
Liver: Anatomy. To be released into
circulation
Circulation
The movement of the blood as it is pumped through the cardiovascular system.
ABCDE Assessment, these mature cells pass through the
endothelium
Endothelium
A layer of epithelium that lines the heart, blood vessels (vascular endothelium), lymph vessels (lymphatic endothelium), and the serous cavities of the body.
Arteries: Histology (lining the
sinusoids
Sinusoids
Liver: Anatomy) by
transcellular
Transcellular
The movement of one cell into, through, and out of another cell.
Tubular System migration.
Human
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 histologic architecture:
Images show the different cells and structures that are in the marrow.
A: A
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
biopsy
Biopsy
Removal and pathologic examination of specimens from the living body.
Ewing Sarcoma from a 5-year-old child is > 90% cellular, with a predominance of trilineage
hematopoiesis
Hematopoiesis
The development and formation of various types of blood cells. Hematopoiesis can take place in the bone marrow (medullary) or outside the bone marrow (extramedullary hematopoiesis).
Bone Marrow: Composition and Hematopoiesis and little admixed
adipose tissue
Adipose tissue
Adipose tissue is a specialized type of connective tissue that has both structural and highly complex metabolic functions, including energy storage, glucose homeostasis, and a multitude of endocrine capabilities. There are three types of adipose tissue, white adipose tissue, brown adipose tissue, and beige or “brite” adipose tissue, which is a transitional form.
Adipose Tissue: Histology.
B: A
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
biopsy
Biopsy
Removal and pathologic examination of specimens from the living body.
Ewing Sarcoma from a 60-year-old adult is composed of 50% hematopoietic elements and 50% admixed mature
adipose tissue
Adipose tissue
Adipose tissue is a specialized type of connective tissue that has both structural and highly complex metabolic functions, including energy storage, glucose homeostasis, and a multitude of endocrine capabilities. There are three types of adipose tissue, white adipose tissue, brown adipose tissue, and beige or “brite” adipose tissue, which is a transitional form.
Adipose Tissue: Histology.
A and B: Original magnification 10Ă—;
scale
Scale
Dermatologic Examination bar = 100 ÎĽm
The main function of the 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 is to act as the site of T-cell differentiation and maturation (from 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, progenitor cells go to the 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).
The
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:
A primary lymphoid organ located in the anterosuperior
mediastinum
Mediastinum
The mediastinum is the thoracic area between the 2 pleural cavities. The mediastinum contains vital structures of the circulatory, respiratory, digestive, and nervous systems including the heart and esophagus, and major thoracic vessels.
Mediastinum and Great Vessels: Anatomy.
The architecture consists of an outer
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 with
lobules
Lobules
Breasts: Anatomy separated by trabeculae. Each lobule has an outer dark-staining cortex and a central, pale-staining medulla. The cortex contains immature
T lymphocytes
T lymphocytes
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, which eventually migrate to the medulla as they mature.
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 (
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
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) are in the corticomedullary junction.
Histologic section showing the structure of a 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
Image by Geoffrey Meyer, edited by Lecturio.