Thymus/Marrow Flashcards
Describe the normal gross features of Thymus
- Lobulated - Each lobule with a cortex/medulla
- Anterior mediastinum
- involutes with age
Microscopic normal thymus
- Network of epithelial cells
- Filled with Lymphs, Mphages. and DC
- Cortex = dense lymph populaton
- Medulla = aggregates of keratinized epithelial cells (Hassall’s corpuscles)
Major function of the Thymus
Maturation of the T lymphs –so they do no recognize self
Embryonic origin of Thymus
Endoderm of 3rd pharyngeal pouch –> Epithelial reticular cells
Hassel’s corpuscles
aka Thymic corpuscles
- Concentric clusters of reticular epithelial cells in medulla
- sometimes they keratinize
Combined Immunodeficiency (CID)
-Marked lymphoid hypoplasia in lymphoid organs –> secondary adenoviral bronchitis/ bronchopneumonia –> Death (before 3mo)
- autosomal recessive =Arabian foals
- X-linkd Dz = Basset
Lymphoid necrosis causes..
Thymic Atrophy
Acute Thymusitis
- Necrotizing
- Bovine Chlamydial Abortion
- Canine Parvovirus, Equine herpesvirus, feline panleuk, FIV - Suppurative
Common species associated with Thymoma
Cat, Dog
-Neoplastic thymic epithelial cells mixed with non-neoplastic lymphocytes
Structure of Bone Marrow
support structure formed by a network of adventitial cells (reticular cells)
hematopoietic cells (erythrocytic, myelomonocytic, megakaryocytic, lymphocytic) and sinusoids reside with in
Function of bone marrow
- Hematopoiesis
2. Fat Depot
What are the hemopoietically active bones in an Adult
- Ribs
- Sternum
- Vertebral body
- Pelvis
Causes of Hypoplasia/aplasia in Bone Marrow
- Chemicals
- Cytostatic drugs
- Bracken fern
- Radiation
- Virus
- Feline Panleuk
- Uremia
-Yellow Fatty Marrow
Causes of Serous atrophy of fat
- Starvation
- Cachexia (chronic infection / neoplasia)
- Pale gelatinous marrow
Causes of Acute Osteomyelitis
- Suppurative
- Staph aureus
- Necrotizing
- Embolic osteomyelitis
