Immuno - Lymphoid Structures Flashcards
Pg. 192-193 Sections include: Lymph node Lymph drainage Sinusoids of spleen Thymus
What kind of lymphoid organ is a lymph node? How many afferents versus efferents does it have?
A secondary lymphoid organ that has many afferents, 1 or more efferents
What are 2 histological characteristics of a lymph node?
Encapsulated, with trabeculae
What functions do lymph nodes serve?
Functions are (1) nonspecific filtration by macrophages, (2) storage and activation of B and T cells, (3) antibody production
Where are lymph node follicles found? What function/purpose do they serve?
In outer cortex; Site of B-cell localization and proliferation
What is the difference between primary and secondary follicles in lymph nodes?
PRIMARY follicles are dense and dormant, SECONDARY follicles have pale central germinal centers and are active
Of what components does the medulla of a lymph node consist?
Consists of medullary cords (closely packed lymphocytes and plasma cells) and medullary sinuses
What function/purpose do medullary sinuses of lymph nodes serve?
Medullary sinuses communicate with efferent lymphatics and contain reticular cells and macrophages
Where is the paracortex of a lymph node found? What type of cells does it house?
Region of cortex between follicles and medulla; Houses T cells
What kind of vessels are found in the paracortex, and what function do they serve? What implication does this have?
Contains high endothelial venules through which T and B cells enter from blood; In an extreme cellular immune response (i.e., viral), paracortex becomes enlarged.
Which lymph node component is not well developed in DiGeorge syndrome?
Paracortex - Not well developed in patients with DiGeorge syndrome
Draw a visual of a lymph node, labeling the following: (1) Capsule (2) Subcapsular sinus (3) Capillary supply (4) Efferent lymphatic (5) Afferent lymphatic (6) Artery (7) Vein (8) Postcapillary (high endothelial) venules (9) Follicle of cortex (B cells) (10) Paracortex (T cells) (11) Medullary sinus (macrophages) (12) Trabecula (13) Medullary cords (plasma cells).
See p. 192 in First Aid for visual
Name the primary cell type associated with each of the following regions in a lymph node: (1) Follicle (2) Paracortex (3) Medullary sinus (4) Medullary cords.
(1) B cells (2) T cells (3) Macrophages (4) Plasma cells
What are the 3 areas of the body that have an axillary primary lymph node drainage site?
Upper limb, lateral breast, skin above umbilicus
What are the areas of the body that have the following primary lymph node drainage sites: (1) Celiac (2) Superior mesenteric (3) inferior mesenteric
(1) Liver, stomach, spleen, pancreas, upper duodenum (2) lower Duodenum, jejunum, ileum, colon to splenic flexure (3) Colon from splenic flexure to upper rectum
What are the 2 areas of the body that have a superficial inguinal primary lymph node drainage site?
(1) Anal canal (below pectinate line) (2) skin below umbilicus (except popliteal territory)
What are the areas of the body that have the following primary lymph node drainage sites: (1) Internal iliac (2) Para-aortic
(1) Lower rectum to anal canal (above pectinate line), bladder, vagina (middle third), prostate (2) Testes, ovaries, kidneys, uterus
What are the 2 areas of the body that have a popliteal primary lymph node drainage site?
Dorsolateral foot, posterior calf
What are the names of the 2 lymph ducts in the body? What does each drain?
(1) Right lymphatic duct - drains right side of body above diaphragm (2) Thoracic duct - drains everything else into junction of left subclavian and internal jugular vein
Draw a visual of a sinusoid of spleen, labeling the following: (1) Arterial supply (2) Germinal center (B cells) (3) Central arteriole (4) Red pulp (RBCs) (5) Section of white pulp (6) PALS (T cells) (7) Venous drainage.
See p. 193 in First Aid for visual
Define the sinusoids of the spleen. Include what they are, where they are, and what kind of basement membrane is associated within them.
Long, vascular channels in red pulp with fenestrated “barrel hoop” basement membrane
Where are T cells found in the spleen?
T cells are found within the periarterial lymphatic sheath (PALS) within the white pulp of the spleen
Where are B cells found in the spleen?
B cells are found in the follicles within white pulp of spleen
What types of cells are found nearby the sinusoids of spleen? What function do these cells serve in spleen?
Macrophages found nearby; Macrophages in spleen remove encapsulated bacteria
What are the consequences of splenic dysfunction? List them as a sequence of events.
Splenic dysfunction: decreased IgM –> decreased complement activation –> decreased C3b opsonization –> increased susceptibility to encapsulated organisms
To what type of organisms do patients with splenic dysfunction have an increased susceptibility? Give specific examples of such organisms.
Increased susceptibility to encapsulated organisms: Streptococcus pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis, E. coli, Salmonella, Klebsiella pneumoniae, Group B Streptococci; Think: “SHiNE SKiS”
What 2 major findings can be seen on blood smear postsplenectomy? What other hematological abnormality occurs postsplenectomy?
(1) Howell-Jolly bodies (nuclear remnants) (2) Target cells; Thrombocytosis
What function does the thymus serve?
Site of T-cell differentiation and maturation
What is the embryological origin of the thymus? What is a key structural/physical feature of the thymus?
From epithelium of 3rd branchial pouches; Encapsulated
What is the origin of lymphocytes in the thymus?
Lymphocytes of mesenchymal origin
What is the difference between the thymus cortex versus medulla in terms of appearance?
CORTEX is dense with immature T cells; MEDULLA is pale with mature T cells and epithelial reticular cells containing Hasall’s corpuscles
What types of cells are found in the thymus cortex versus medulla?
CORTEX is dense with immature T cells; MEDULLA is pale with mature T cells and epithelial reticular cells containing Hasall’s corpuscles
Where in the thymus does positive versus negative selection occur?
Positive selection (MHC restriction) occurs in the cortex and Negative selection (nonreactive to self) occurs in the medulla.
