Lymphoid structures Flashcards
Lymph node - general anatomy (gross)
is a 2ry lymphoid organ that has many afferents and 1 or more efferents. Encapsuled, with trabeculae (fibrous capsule extends to form trabeculae)
bean shape
It has a hilum (blood vessels and efferent lymphatics)
Lymph node - afferents vs efferents
many afferents and 1 or more efferents
Lymph node - trabeculae structure
fibrous capsule extends to form trabeculae
The lymph parenchyma is divided into (functionally)
- Follicle of cortex
- Paracortex
- Medulla
Lymph node - function
- nonspecific filtration by macrophages
- storage of B and T cells
- immune response activation
Lymph node - Follicle
Site of B-cell location and proliferation. In outer cortex
1ry follicles are dense and dormant. 2ry have pale central germinal centers and are active
Lymph node - Follicle - 1ry vs 2ry
1ry follicles are dense and dormant. 2ry have pale central germinal centers and are active
Lymph node - medulla
Consist of medullary cords (closely packed lymphocytes and plasma cells) and medullary sinus. Medullary sinus communicate with efferent lymphatics and contain reticular cells and macrophages
Lymph node - medulla conistis of (and contain)
- medullary cord –> lymphocytes and plasma cells
2. medullary sinus –> reticular cells and macrophages
Lymph node - Paracortex
Houses T cells. Region of cortex between follicles and medulla. Contains high endothelial venules (postcapillary) through which T cells and B cells enter enter from blood
lymphoid tissue - Parenchymal anatomy - from outter to inner
outer - capsule (with trabecula) - subcapsular - cortex (follicle of cortex and inner the paracortex) - medullar - inner
lymph tissue - site of B-cell localization and proliferation
Follicle
lymph tissue - area of macrophages and medullary cords plasma cells
macrophages –> medullary sinus
lymphocytes –> medullary cords
Lymph node - Paracortex not well developed in / enlarge in
not well –> DiGeorge syndrome
enlarges –> extreme cellular immune response (eg. viral)
Cervical lymph node cluster drains … (area)
head and neck
Hilar lymph node cluster drains … (area)
lungs
Mediastinal lymph node cluster drains … (area)
Trachea and esophagus
Axillary lymph node cluster drains … (area)
Upper limb, breast, skin above umbilicus
Celiac lymph node cluster drains … (area)
liver, stomach, spleen, pancreas, upper duodenum
Superior mesenteric lymph node cluster drains … (area)
lower duodenum, jejunum, ilieum, colon to splenic fructure
Inferior mesenteric lymph node cluster drains … (area)
colon from splenic flexure to upper rectum
Internal iliac lymph node cluster drains … (area)
Lower rectum to anal canal (above pectinate line), bladder, middle third of vagina, prostate, cervix, corpus carvenosum
Para-aortic lymph node cluster drains … (area)
- Testes 2. ovaries 3. kidneys 4. uterus
The paraaortic lymph nodes lie ….
in front of the lumbar vertebrae near the aorta
Superficial inguinal lymph node cluster drains … (area)
anal canal (below pectinate line), skin below umbilicus (except popliteal territory), scrotum, vuvla , distal vagina
The superficial inguinal lymph nodes form a chain …. (area)
immediately below the inguinal ligament.
Popliteal lymph node cluster drains … (area)
dorsolateral foot, posterior calf
Lymph ducts - function
- Right lymphatic duct drains right side of body above diaphragm into juction of left subclavian and internal jugular veins
- Thoracic duct drains everything else into junction of left subclavian and internal jugular veins
spleen parenchyma is divided to (and locations)
- white pulps (centrally)
- red pulps (RBCs) (peripherally)
- marginal zone (between red and white pulps)
Speen sinusoids?
long, vascular channels in red pulp with fenestrated “barrel hoop” basement membrane
spleen - cells and their location
- T cell: periarteriolar lymphatic sheath (white pulp)
- B cell: follicles (white pulp)
- macrophages and specialized B cells: Marginal zone
- macrophages: Cords of Billroth (red purples)
spleen - role of Marginal zone
it contains macrophages and specialized B cells –> APCs capture blood-borne antigens for recognition by lymphocytes
spleen - role of macrophages
remove encapsuled bacteria
splenic dysfunction - problem (and mechanism) (and example of spleen dysfunction
low IgM synthesis –> decreased complement activation
–> decreased C3b opsonization –> increased susceptibility to encapsuled organisms
example –> 1. postsplenoctomy 2. sickle cell anemia
Encapsuled bacteria - their capsule serve as an
anthiphagocytic viruence factor
asplenic patients - vaccines and their structure
- S. pneumoniae –> PCV conjugate (Prevnar) , PPSV non congugate (Pneumovax)
- H. influenzae type B–> conjugate
- N. meningitidis –> conjugate
Postsplenectomy - lab findings (and mechanism)
- Howell-jolly bodies (nuclear remnants)
- Target cells
- Thrombocytosis (loss of sequestration and removal)
- Lymphocytosis (loss of sequestration)
Thymus - function
site of T-cell differentiation and maturation
Thymus - gross anatomy and location
encapsuled
located in anteriosuperior mediastinum
Thymus embriology
thymus –> third pharyngeal pounch
Lymphocytes –> mesenchymal
Thymus - histology
- cortex is dense with immature T cells
- medulla is pale with mature T cells and Hassal corpuscles containing epithelial reticular cells
Thymus - situations that change its size
- hypoplastic in DiGeorge syndrome and severe combined immunodeficiency
- Enlarged in myasthenia gravis
spleen - follicle anatomy
germinal center in the middle –> mantle zone –> marginal zone
spleen - types of circulation (and area)
- open circulation (sinusoids)
2. closed circulation
