Microscopic Structure of Lymph node, Spleen, Thymus and Tonsil Dr. Sama ul Haque

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

Lymph Node

Lymph Node Covered by a capsule which extends to form Trabeculae. Divided into outer cortex and inner medulla. OUTER CORTEX contains: Lymphatic nodules with germinal center INNER MEDULA contains: Medullary Cords and Medullary Sinus

Lymph node SC --- Subcapsular Sinus C --- Cortex M --- Medulla H --- Hilum LN --- Lymphatic Nodules T --- Trabeculae MS --- Medullary Sinus MC --- Medullary Cords Capsule SC C M MS H MC T Lymphatic nodules لاحـظوا الـ LN

Lymph node CT --- Connective tissue C --- Cortex M --- Medulla P --- Paracortex LN --- Lymph Node T ---Trabeculae MS --- Medullary Sinus MC --- Medullary Cords Lymphatic nodules لاحـظوا الـ

C -- Capsule, S -- Subcapsular Sinus, N -- Lymph Node Lymphatic nodules لاحـظوا الـ C -- Capsule, S -- Subcapsular Sinus, N -- Lymph Node

Lymph node Lymphatic nodules لاحـظوا الـ

Lymph node Lymphatic nodules لاحـظوا الـ

Flow of Lymph

Spleen

Spleen Covered by a capsule which extends to form Trabeculae. Trabeculae contains trabecular arteries & Veins. Lymphatic nodules with germinal centers constitutes the white Pulp. Central artery passes through lymphatic nodules. Red or Splenic pulp contains pulp arteries, Venous sinuses and Splenic cords (Cords of Billroth).

Spleen

Spleen

Splenic Cords and Splenic Sinusoids

Open and Closed Circulation in Spleen

Thymus

Thymus Covered by a capsule which extends to form Trabeculae. Trabeculae extends inwards to forms numerous incomplete lobules (lobulated appearance). Each lobule consists of dark staining outer cortex and a light staining inner medulla.

Thymus Cortex contains densely packed lymphocytes (No lymphatic nodules). Medulla contains fewer lymphocytes but more epithelial reticular cells. Medulla also contains Thymic (Hassall’s) Corpuscles. Thymic (Hassall’s) Corpuscles are oval structures consisting of round whorls of flattened epithelial cells.

Thymus

Thymus

Palatine Tonsil

Palatine Tonsil Surface of the Tonsil is covered by Stratified Squamous nonkeratinized epithelium. Tonsil is invaginated by deep grooves called Tonsillar Crypts. Below epithelium lymphatic nodules are present in the connective tissue. Dense connective tissue underlies the palatine tonsil and forms capsule.

Palatine Tonsil

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