Microscopic Structure of Lymph Node, Spleen, Thymus and Tonsil PDF

# Microscopic Structure of Lymph node, Spleen, Thymus and Tonsil ## Anatomy Department ## Objectives - Understand the location of lymphatic organs. - Discuss the microscopic features of Lymph Node. - Discuss the microscopic features of Spleen. - Discuss the microscopic features of Thymus. - Disc...

# Microscopic Structure of Lymph node, Spleen, Thymus and Tonsil ## Anatomy Department ## Objectives - Understand the location of lymphatic organs. - Discuss the microscopic features of Lymph Node. - Discuss the microscopic features of Spleen. - Discuss the microscopic features of Thymus. - Discuss the microscopic features of Tonsil. ## Location of Lymphatic Organs - An image of a human body showing the location of lymphatic organs ## Lymph Node - **Stroma**: Covered by a capsule which extends to form Trabeculae - **Parenchyma**: Divided into: - Outer cortex - Paracortex - Inner medulla - The most abundant cells of lymph nodes are many reticular cells, plasma cells, dendritic cells, macrophages, APCs, and lymphocytes of all types. - **Outer Cortex**: - A subcapsular sinus - Cortical sinuses running between the lymphoid nodules arise from the subcapsular sinuses - Lymphoid Nodules: Lymphoid nodules can be with or without germinal center (consist largely of developing B lymphocytes & few helper T) - **Paracortex**: Lacks lymphoid nodules and has an accumulation of T cells. - **Inner Medulla**: - Medullary Cords (B lymphocytes, plasma cells and macrophages) - Medullary Sinus (lymph, lymphocytes, often many macrophages) ## An image of a lymph node - **Cortex:** Lymphatic Nodule, Germinal Center, Mantle Zone - **Medulla:** Medullary sinus, Medullary cord - **Paracortex** - **Capsule** - **Trabeculae** - **Hilum** - **Efferent lymphatic vessel** - **Afferent lymphatic vessels** - **Artery** - **Vein** - **High endothelial venule** - **Blood capillaries around lymphatic nodule** - **Subcapsular sinus** ## An image of a lymph node - **SC**: subcapsular sinus - **C**: cortex - **M**: medulla - **H**: hilum - **LN**: lymphatic nodules - **T**: trabeculae - **MS**: medullary sinus - **MC**: medullary cords ## An image of a lymph node under a microscope - **CT**: connective tissue - **C**: cortex - **M**: medulla - **P**: paracortex - **LN**: lymphatic nodules - **T**: trabeculae - **MS**: medullary sinus - **MC**: medullary cords ## An image of a lymph node under a microscope - **C**: capsule - **S**: subcapsular sinus - **N**: lymphatic nodules ## An image of a lymph node under a microscope - **1**: connective tissue - **2**: afferent lymphatic vessel with valve - **3**: capsule - **4**: subcapsular (marginal) sinus - **5**: connective tissue trabecula - **6**: trabecular (cortical) sinuses - **7**: germinal center of lymphatic nodule - **8**: paracortex (deep cortex) - **9**: medullary cords - **10**: medullary sinuses - **11**: venule and arteriole - **12**: subcapsular (marginal) sinus - **13**: lymphatic nodule - **14**: connective tissue trabecula - **15**: germinal center of lymphatic nodule - **16**: trabecular blood vessels - **17**: paracortex (deep cortex) - **18**: medullary sinuses - **19**: medullary cords ## An image of a lymph node under a microscope - **1**: subcapsular sinus - **2**: macrophage - **3**: capsule - **4**: trabecula - **5**: endothelial cell - **6**: macrophage - **7**: small lymphocytes - **8**: reticular cells - **9**: germinal center - **10**: medium-sized lymphocytes - **11**: reticular cells - **12**: trabecular sinuses - **13**: endothelial cell - **14**: lymphatic nodule (peripheral zone) - **15**: lymphoblasts undergoing mitosis - **16**: macrophage - **17**: lymphoblasts ## Spleen - **Stroma (Connective Tissue)**: Covered by a capsule which extends to form Trabeculae which partially subdivide the parenchyma. Trabeculae contains trabecular arteries & Veins. - **Parenchyma (Splenic pulp)**: No cortex/medulla - **Splenic Pulp**: White pulp and Red pulp - **White pulp**: - Lymphatic nodules with germinal centers: central artery passes through lymphatic nodules which is surrounded with the periarteriolar lymphoid sheathes (PALS of T cells) - **Red pulp consists of**: - Splenic cords of Billroth (reticular tissue filled with T and B lymphocytes, macrophages, other leukocytes, and red blood cells) - Splenic sinusoids - Red pulp is filled with blood cells of all types. located both in cords and sinuses. ## An image of a spleen - **C**: capsule - **T**: trabeculae - **W**: white pulp - **R**: red pulp ## An image of a spleen under a microscope - **1**: capsule - **2**: central artery - **3**: trabeculae - **4**: lymphatic nodule (white pulp) - **5a**: trabecular: vein - **5b**: trabecular: artery - **6**: lymphatic nodule (white pulp) - **7**: central artery - **8**: germinal center - **9**: germinal center - **10**: central artery - **11**: trabeculae - **12**: splenic cords (in red pulp) - **13**: venous sinuses (in red pulp) - **14**: pulp arteries ## An image of a spleen under a microscope - **1**: splenic cord - **2**: venous sinus - **3**: lymphatic nodule - **4**: central artery - **5**: germinal center - **6**: trabecular artery - **7**: trabecular vein - **8**: splenic cords - **9**: venous sinuses - **10**: pulp arteries ## An image of a splenic cords and sinusoids under a microscope - **Sinusoid:** a blood-filled space - **Splenic cord** - **Reticular fibers** ## Open and Closed Circulation in Spleen - An image of a representation of blood circulation in the spleen - Blood flow in red pulp is either a closed circulation, moving from capillaries into the venous sinusoids, or an open circulation, with capillaries opening directly into the splenic cords. ## Thymus - **Stroma**: Covered by a capsule which extends to form Trabeculae. Trabeculae extends inwards to forms numerous incomplete lobules (lobulated appearance). - **Parenchyma**: Each lobule consists of: - Outer cortex (dark staining) - Inner medulla (light staining) ## An imagen of a thymus - **1**: capsule - **2**: trabeculae - **3**: cortex - **4**: medulla - **5**: blood vessels - **6**: thymic (Hassall’s) corpuscles - **7**: adipose cells - **8**: lobule - **9**: thymic (Hassall’s) corpuscles - **10**: connective tissue of trabecula - **11**: adipose cells - **12**: medulla (continous between lobules) - **13**: cortex - **14**: blood vessel ## An image of a thymus under a microscope - **1**: cortex (with thymic lymphocytes) - **2**: trabecula - **3**: medulla - **4**: adipose cells - **5**: cortex (with thymic lymphocytes) - **6**: blood vessels - **7**: epithelial reticular cells - **8**: thymic (Hassall’s) corpuscle - **9**: degeneration centers of thymic (Hassall’s) corpuscle - **10**: epithelial reticular cells ## Tonsils - Masses of lymphoid nodules are collected in three general locations in the wall of the pharynx. - Palatine tonsils - Lingual tonsils - Both the Palatine & Lingual tonsils are covered with stratified squamous epithelium. - The pharyngeal tonsil: It is usually covered by ciliated pseudostratified columnar epithelium typical of the upper respiratory tract. - All these epithelia of the tonsils contain intraepithelial lymphocytes and dendritic cells. ## Palatine Tonsil - Surface of the Tonsil is covered by Stratified Squamous nonkeratinized epithelium. - Tonsil is invaginated by deep grooves called Tonsillar Crypts. - Below epithelium is lymphoid tissue filled diffusely with lymphocytes, with many secondary lymphoid nodules around the crypts. - Dense connective tissue underlies the palatine tonsil and forms capsule. ## An image of the pharynx and its tonsils - **Pharyngeal tonsil** - **Opening of auditory tube** - **Palate** - **Palatine tonsil** - **Lingual tonsil** ## An image of a palatine tonsil under a microscope - **1**: stratified squamous nonkeratinized epithelium - **2**: lymphatic nodules - **3**: tonsillar crypts - **4**: capsule - **5**: skeletal muscle - **6**: stratified squamous nonkeratinized epithelium - **7**: germinal centers - **8**: trabeculae with blood vessels - **9**: tonsillar crypts - **10**: capsule ## Lingual Tonsils - Are covered by stratified squamous epithelium with crypts. - The lymphoid tissue of these tonsils has many of the same basic features as that of palatine tonsils. ## Pharyngeal Tonsil - Is usually covered by ciliated pseudostratified columnar epithelium - Below the epithelium is diffuse lymphoid tissue and lymphoid nodules. - Lacks crypts - Hypertrophied pharyngeal tonsils resulting from chronic inflammation are called adenoids. ## Thank You The file was converted from a PDF document containing images. The descriptions were generated automatically, so some descriptions could be inaccurate.