L7 - Organs of the Lymphatic System

Question 1

precocious development

Answer 1

advanced development (of an organ, such as the thymus)

Question 2

parenchymal structural cell type of the thymus

Answer 2

epithelio-reticular cells

Question 3

thymic cortex

Answer 3

outer, dark-staining region of thymus comprised of large thymocytes and PAS cells

Question 4

PAS cells

Answer 4

macrophages in the thymic cortex that protect thymocytes from being exposed to antigen

Question 5

thymic medulla

Answer 5

inner, lighter-staining region of thymus that contains Hassall’s corpuscles

Question 6

Hassall’s corpuscles

Answer 6

akin to keratin pearls, these are the identifying feature of the thymic medulla; comprised of keratohyalin granules, intermediate filaments, and lipid droplets

Question 7

blood/thymic barrier

Answer 7

• Capillary Endothelium with Basal Lamina
• Perivascular CT with macrophages
• Epithelio-Reticular Cells (Type I) with basal lamina and tight junctions

Question 8

lymphatic nodule (follicle)

Answer 8

sites where B and T cells encounter antigen

Question 9

pharyngeal tonsils (adenoids)

Answer 9

tonsils marked by pseudostratified columnar epithelium with goblet cells and cilia; found in the superior and posterior portion of pharynx

Question 10

palatine tonsils

Answer 10

marked by stratified squamous epithelium and crypts

Question 11

lingual tonsils

Answer 11

tonsils marked by stratified squamous epithelium and located at base of tongue

Question 12

lymph node structure

Answer 12

CT capsule > sinus (containing macrophages) > nodular cortex (B-cells) > paracortex (T-cells) > Hilar region

Question 13

advanced development (of an organ, such as the thymus)

Answer 13

precocious development

Question 14

epithelio-reticular cells

Answer 14

parenchymal structural cell type of the thymus

Question 15

outer, dark-staining region of thymus comprised of large thymocytes and PAS cells

Answer 15

thymic cortex

Question 16

macrophages in the thymic cortex that protect thymocytes from being exposed to antigen

Answer 16

PAS cells

Question 17

inner, lighter-staining region of thymus that contains Hassall’s corpuscles

Answer 17

thymic medulla

Question 18

akin to keratin pearls, these are the identifying feature of the thymic medulla; comprised of keratohyalin granules, intermediate filaments, and lipid droplets

Answer 18

Hassall’s corpuscles

Question 19

sites where B and T cells encounter antigen

Answer 19

lymphatic nodule (follicle)

Question 20

tonsils marked by pseudostratified columnar epithelium with goblet cells and cilia; found in the superior and posterior portion of pharynx

Answer 20

pharyngeal tonsils (adenoids)

Question 21

marked by stratified squamous epithelium and crypts

Answer 21

palatine tonsils

Question 22

tonsils marked by stratified squamous epithelium and located at base of tongue

Answer 22

lingual tonsils

Question 23

thymus

Answer 23

The thymus is surrounded by a dense CT capsule from which trabeculae extend penetrating through the gland, organizing it into a dense cortex and lighter medulla. The cortex contains small T lymphocytes (also called thymocytes) which occupy spaces surrounded by epithelioreticular cells (stromal or supporting cells). Macrophages are also present and are responsible for phagocytosis of T cells that do not become thymic educated. Hence they are programed to die prior to leaving the thymus. The medulla is the lighter, inner portion of the thymus gland. It also contains epithelioreticular cells and larger lymphocytes with paler-staining nuclei and more abundant cytoplasm. There are multiple types of epithelioreticular cells but one of importance – Type VI – form Hassall’s corpuscles, which is the characteristic histological feature of the thymus gland. These acidophilic staining structures are isolated masses of cells that exhibit flat nuclei, keratohyalin granules and intermediate filaments. The core of the corpuscle often appears keratinized. Their function is unknown and they increase in number with age.