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BIOC21H3 Study Guide - Lymphatic Vessel, Lymph Node, Mhc Class Ii


Department
Biological Sciences
Course Code
BIOC21H3
Professor
Stefan Rusyniak

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LECTURE 9 LYMPHATIC TISSUES
ANTIGEN-PRESENTING
CELLS (APC)
DIFFUSE LYMPHATIC
TISSUE (DLT)
LYMPH NODULES
FOLLICULAR
DENDRTIC CELLS
- Phagocytic
- Group of cells with MHC II
complexes on their surfaces to
allow for lymphocyte stimulation
- Phagocytosis, degradation and
presentation
Antigen presentation is done
by a specialized cell surface
component MHC II
stimulate T- or B-lymphocyte
activation
MHC II complexes only used
to present what the cell has
engulfed outside of itself
once cell recognizes it, the cell
will proliferate and produce
1000s of lymphocytes that can
recognize the antigen
- Includes most members of the
Mononuclear Phagocyte System
(MPS)
Macrophages
Kupfer Cells: specialized
macrophages within the liver
Langerhan’s Cells: found
within skin (embedded in
epidermis); migrate out of skin
into lymph vessel and travel to
nearest lymph node to activate
- Disorganized tissue usually
found underneath epithelium
in contact with the outside
world (e.g., respiratory
system, urinary system)
- Accumulations of
leukocytes under epithelia
Includes: Lymphocytes,
Eosinophils, Plasma
Cells
- Located at entry points
into the body
- Named based on location
MALT Mucosa
Associated Lymphatic
Tissue Found in the
Mucosal layer of
gastrointestinal,
respiratory and
genitourinary tracts
Often subdivided into:
1) GALT Gut
Associated
Lymphatic Tissue
2) BALT
Bronchus
Associated
Lymphatic Tissue
- Usually lined by stratified
- Localized clusters of
lymphocytes, etc.
Well defined but not
encapsulated
Often associated with DLT
- Found in:
Tonsils (Pharyngeal, Palatine,
Lingual)
Ileum of the small intestine
(Peyer‟s Patches) – found in
the exact same spot always
Appendix
- Have a boundary
- Sit on a reticular tissue network
- Divide into 1o and 2o nodules:
1) Primary Nodules mostly
composed of small
lymphocytes
Display fairly uniform
staining
Inactivated, has not come
across a pathogen
2) Secondary Nodules
Mantle (outer rim) of
small lymphocytes
Have a light-staining
germinal center
(proliferated lymphocytes;
where lymphocytes have
- Collect Antigen-
Antibody complexes on
the cell surface
This makes them
available to
adjacent
lymphocytes
- Not considered an APC
but has similar functions
No MHC II
complex at the
surface
No phagocytosis of
Ab-Ag complex
occurs
- Found at the germinal
centres
- Have long branching
processes with
lymphocytes in between
them large
- FDC spread out their
projections to collect
material passing through
from afferent lymph vessel
Sticky; grabs
passing protein and
has them flow
through/along

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other cells for immune
response
B-lymphocytes
- Includes Epithelioreticular
Cells (REC) (thymus)
Not part of MPS
epithelia (tougher to get
through than simple epithelia)
- Embedded in the loose CT
under epithelia (Tunica
mucosa)
been activated) due to lots
of cytoplasm from large
lymphocytes
surface of cell
interacts with B-
lymphocyte on FDC
surface
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LYMPH NODE
THYMUS
SPLEEN
Type Of
Organ
2o Lymphatic Organ
1o Lymphatic Organ
2o Lymphatic Organ (largest)
Structure
- Encapsulated (incomplete capsule)
dense irregular CT
- Capsule = type I collagen, fibroblasts,
etc.
- Kidney bean-shaped
- Capsule invaginates into the interior of
the organ to form trabeculae gives
porous structure
- Composed of a reticular tissue network
produced by reticular cells (specialized
fibroblasts)
- Efferent lymphatic vessels, arteries and
veins enter through a region called a Hilus
- Afferent lymphatic vessels enter from
exterior
- Bilobed, somewhat heart-shaped
- Transient structure
Fully functional at birth
Atrophies (decreases in size) and
replaced by adipose tissue starting at
puberty (involution) also occurs in
bone marrow (from red to yellow)
- Encapsulated (dense irregular CT)
continuous capsule due to filtration occurring
- Capsule invaginates to form
septa/”trabeculae”
Divide the interior into lobules
- Lobules contain a support network
Composed of REC
No reticular fibers, no reticular cells
- Blood supply
Highly vascularized
Many small blood vessels are seen
throughout the cortex and medulla
Larger vessels are seen in
septa/trabeculae
Has a Blood-Thymus Barrier
prevents contact with non-
immunocompetent T-cells with
interior of blood vessel
- No afferent lymphatic vessels but does have
an efferent lymphatic vessel
- Lobules subdivided into cortex and medulla
- Encapsulated (dense irregular CT) thick,
continuous capsule (smooth muscle
sometimes seen within capsule because of
blood vessel going through it)
- Capsule invaginates to form “trabeculae”
Contain blood vessels
Trabeculae may appear to have
muscle because of blood vessels
- Highly vascularized
- No afferent lymphatic vessels
- Not divided into cortex and medulla
- Divided into White Pulp and Red Pulp due
to the appearance of freshly sectioned tissue
Cortex
- Contains Lymph Nodules
Follicular Dendritic Cells (FDC)
- Contains densely-packed lymphocytes
- Other common cells are Reticuloepithelial
None
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