Lymphatic and Immune Systems

Vocabulary flashcards covering primary and secondary lymphatic organs, tissues, lymph node structure and anatomy, and related medical conditions based on the lecture text.

Appendix

A narrow pouch projecting off the lower end of the large intestine that is densely populated with lymphocytes and serves as a reservoir for beneficial gut bacteria.

Peyer's Patches

Small masses of lymphatic tissue scattered throughout the small intestine beneath the intestinal mucosa that monitor bacterial populations and alert lymphocytes during an invasion.

Gut-Associated Lymphatic Tissue (GALT)

A subset of mucosa-associated lymphoid tissue (MALT) located in the digestive tract, including Peyer's patches, that plays a critical role in the immune response.

Lymphatic Organs

Well-defined structures enclosed by connective tissue capsules that separate them from neighboring tissues, categorized into primary and secondary organs.

Primary Lymphatic Organs

Organs including the thymus and red bone marrow where stem cells divide, mature into T and B lymphocytes, and acquire immunocompetence.

Secondary Lymphatic Organs

Organs including lymph nodes and the spleen where mature lymphocytes become activated to protect the body from pathogens.

Immunocompetence

The trait acquired by lymphocytes enabling them to recognize and attack foreign invaders.

Thymus

A primary lymphatic organ located in the mediastinum that produces T cells and the hormone thymosin, and undergoes regression beginning around age $14$.

Thymosin

A hormone secreted by the thymus that promotes the development of lymphocytes.

Thymic Lobules

Structural divisions of the thymus extending inward from a fibrous capsule, consisting of a dense outer cortex and a less dense inner medulla filled with T lymphocytes.

Lymph Nodes

Bean-shaped secondary lymphatic organs ranging from $\frac{1}{25}''$ ($1\,mm$) to over $1''$ ($25\,mm$) that filter lymph, removing $99\%$ of impurities.

Trabeculae

Connective tissue extensions from the capsule into a lymph node that divide it into compartments.

Cortical Nodules

Lymphocyte-filled compartments inside a lymph node formed by trabeculae.

Germinal Centers

Less dense central areas within cortical nodules that form and release lymphocytes during an infection.

Afferent Lymphatic Vessels

Multiple vessels that channel unfiltered lymph fluid into a lymph node.

Efferent Lymphatic Vessel

A single vessel through which filtered lymph exits a lymph node.

Cervical Lymph Nodes

Lymph node clusters located in the neck that monitor lymph arriving from the head and neck.

Axillary Lymph Nodes

Lymph node clusters located in the armpit that receive lymph from the arm and breast, through which more than $85\%$ of breast lymph enters.

Inguinal Lymph Nodes

Lymph node clusters located in the groin that receive lymph returning from the legs.

Sentinel Lymph Node

The first lymph node reached by metastasizing cancer cells after breaking free from a primary tumor.

Lymphedema

Swelling in surrounding tissues resulting from the disruption of normal lymph flow and accumulation of lymph.

Lymphadenopathy

Painful enlargement of one or more lymph nodes caused by lymphocyte proliferation in response to infection or malignancy.

Suboccipital Lymph Nodes

Lymph nodes residing where the back of the neck meets the head that drain lymph from the head and scalp.

Postauricular Lymph Nodes

Lymph nodes located behind the ear that drain the head, neck, sinuses, ears, scalp, and pharynx.

Preauricular Lymph Nodes

Lymph nodes located in front of the ear that drain the scalp and external auditory canal.

Submandibular Lymph Nodes

Lymph nodes located beneath the mandible that drain the head, neck, sinus, ears, eyes, scalp, and pharynx.

Spleen

The body's largest lymphatic organ, located in the upper left quadrant inferior to the diaphragm, responsible for filtering blood, destroying worn-out RBCs, storing $20\%$ to $30\%$ of platelets, and hematopoiesis.

White Pulp

Splenic tissue consisting of compact masses of lymphocytes surrounding arteries that screen passing blood for foreign antigens.

Red Pulp

Splenic tissue along compartment edges containing erythrocyte-filled sinuses supported by reticular fibers and phagocytic cells.

Splenectomy

The surgical removal of the spleen, typically performed following severe trauma or rupture.