Anatomy of the Immune System - Lesson 28 (PDF)

Anatomy III: Blood and the Cardiovascular and Respiratory Systems Antoni Alegre Martinez 6 CM Lesson 28 Anatomy of the immune system. Generalities 2 Immune system System for the protection against the diseases The immu...

Anatomy III: Blood and the Cardiovascular and Respiratory Systems Antoni Alegre Martinez 6 CM Lesson 28 Anatomy of the immune system. Generalities 2 Immune system System for the protection against the diseases The immune system must distinguish the normal body cells from the pathogen cells like bacteria, virus, cancer cells, etc. Classifications: – Innate vs Adaptative – Humeral vs Cellular In the following lessons, we are going to learn the anatomical basis of the immune system, and not how the immune response works, which has been studied in the subject of Physiology 3 Composition of lymphoid system Lymphoid organs: those organs that produce lymphocytes: Primary lymphoid organs: where the immature lymphocytes develop – Thymus – Red bone marrow Secondary lymphoid organs: the lymphocytes remain until the presentation of the antigen – Spleen – Tonsils – Some lymphoid nodules in the alimentary tract and appendix – Lymph nodes 4  Thymus Located in the anterior and superior mediastinum Shape: flat triangle After puberty, it degrades into fat 5 Bone marrow Main hematopoietic organ Primary lymphoid organ It produces 500 billion blood cells per day It generates lymphocytes from immature hematopoietic progenitor cells It is possible to transplant it, useful to treat cancer (multiple myeloma, leukemia, etc) 6 Bone marrow Two types of bone marrow: – Yellow marrow: fat cells at the medullary cavity – Red marrow: hematopoietic tissue, where the red blood cells, platelets and lymphocytes grow At birth, all marrow is red and with the age, the marrow is becoming yellow Yellow marrow can be transformed into red marrow in case of severe hypovolemia 7 Bone marrow Main places to find bone marrow: Pelvis Vertebrae Sternum Ribs Cranium Scapulae The spongy end of long bones – Humerus – Femur 8 Spleen Located in the left upper quadrant of the abdomen (hypocondrium) Shape: purple fist. It is the largest lymphatic organ Most vulnerable abdominal organ It is a lymphoid organ because of: – Lymphocyte proliferation – Immune surveillance – Immune response 9 Spleen Spleen recycles iron and globin from old blood cells and platelets Spleen acts as a blood reservoir, storing red blood cells and platelets It is not a vital organ, we can live without it It is capable of expansion and contraction 10  Tonsils The pharynx has abundant lymphoid tissue forming masses called tonsils This lymphoid tissue forms a tonsillar ring around the superior part of the pharynx, also known as Waldeyer’s ring It protects from the external bodies that enter inside the body through the mouth and nose 11 Pharyngeal tonsil also called adenoid: located at the mucous membrane at the superior part of the nasopharynx If it grows during tonsillitis, it can cause dysphagia It is separated from the superior pharyngeal constrictor muscle thanks to a capsule that allows the surgeon to remove the whole tonsil during adenoidectomy 12 Pharyngeal tonsil is made by clusters of lymph nodules with many crypts and invaginations It is highly vascularized thanks to tonsillar branches that come from many arteries such: Ascending palatine, from facial artery Descending palatine, from internal maxillary artery Ascending pharyngeal artery Innervated by IX Glossopharyngeus nerve 13 Tubal tonsils Lymphoid tissue in the submucosa of the pharynx Located near the nasopharyngeal opening to the pharyngotympanic tube = Eustaquian tube 14 Palatine tonsils: bilateral collections of lymphoid tissue located on the oropharynx between the palatine arches. Their removal is called tonsillectomy Tonsillar fossa: fossa between the palatoglossal and palatopharyngeal arches in adults Tonsillar bed: formed by the superior pharyngeal constrictor muscle and the thin fibrous sheet of pharyngobasilar fascia 15 Lingual tonsil Located on the dorsal surface at the base of the tongue It is partially encapsulated It has many mucous glands associated 16 Mucosa-associated lymphoid tissue (MALT) Small groups of lymphoid tissue found in several places of the body Formed by populations of T cells, B cells, plasma cells and macrophages The antigens that come from the mucosal epithelium find here the immune cells. This is a mechanism to avoid infections – Microfold cells: take antigen from the lumen of the intestine to deliver it to the lymphoid tissue Examples: – BALT: bronchus-associated lymphoid tissue – GALT: gut-associated lymphoid tissue – SALT: skin-associated lymphoid tissue 17 Peyer’s patches Named after the Swiss anatomist Johann Conrad Peyer They are 1cm-sized lymphoid tissue GALT located on the ileum Observable at microscope as oval or round lymphoid follicles in the lamina propria layer of the mucosa and extending into the submucosa 18 Peyer’s patches Between the lumen and the follicle there are microfold cells or M Cells that direct the antigens to the lymphocytes – B lymphocytes are located in the center of the follicles – T lymphocytes are located in the zones between two follicles Activated lymphocytes pass to the blood via thoracic duct 19  Microfold cells are antigen presenting cells? No Microfold cells phagocyte the antigen from the lumen of the intestine and deliver it through transcytosis to: – Dendritic cells – Macrophages – T lymphocytes All these cells are the true antigen presenting cells 20  Vermiform Appendix Blind intestinal diverticulum that contains masses of lymphoid tissue About 10 cm in length It arises from the cecum inferior to the ileo-cecal junction The position of the appendix is variable, but it is usually retrocecal 21 Bibliography Moore's Clinically Oriented Anatomy 9th Edition / Anne M. R. Agur, Arthur F. Dalley. Published 2022 Moore Essential Cllinical anatomy 6th edition. Published 2019 Gray's Anatomy for students / Drake, Richard L. 4th Edition Published 2019 Color atlas of anatomy 7h edition, Rohen, Yokochi Manual de embriología y anatomía general. V Smith Agreda Histology of the tonsils by David King Anatomía: estructura y morfología del cuerpo humano, 4ª Edición, Lippert 22