1
Q
function of the lymphatic system
A
to eliminate potentially harmful substances in the body
2
Q
what are the classifications of the lymphatic tissues?
A
- primary lymphatic tissue- bone marrow, thymus- it is the site of development of lymphocytes into immunocompetent cells
- secondary- site of formation of immunological defense against antigens or pathogens- confrontation with them occur here - lymph nodes, MALT (mucosa associated lymphatic tissue), spleen
3
Q
MALT
A
- mucosa associated lymphatic tissue
- GALT- gut associated
- BALT- bronchus associated
- Genital urinary tract
- Tonsils
4
Q
what do lymphatic nodes do?
what does the spleen do?
what does MALT do?
A
- filters lymph
- filters blood
- surveillance
5
Q
How is MALT set up?
A
- it’s simplest organization is that of a loose lymphatic tissue that is part of the lamina propria (first layer) of the wall of the GI tract, respiratory tract (BALT), or GU tract (genital urinary) where an infection may be present
- cells can be loosely scattered in the lamina propria or have a defined layer
- has reticular fibers that form a supporting framework to suspend cells
6
Q
what kind of cells are in MALT?
A
lymphocytes, monocytes, macrophages, plasma cells
7
Q
what are nodules? what are the two types of lymphatic nodules and how are they different?
A
-nodules are non-encapsulated. spherical dense aggregations of lymphocytes with some organization
-primary nodules- homogenous -has mostly small lymphocytes
-secondary nodules-has two distinct zones:
corona zone and the germinal center
8
Q
what are the corona and germinal zones of secondary lymphatic nodules
A
- Corona (mantle) zone- outer, dark-staining zone containing mature, small sized lymphocytes (mnemonic-to drink corona in the sun, you get tan (dark) and you need to be mature (21))
- germinal center- inner, light staining zone containing IMMATURE (medium/large)
- encounter with an antigen causes the germinal area to swell
9
Q
how do primary and secondary nodules appear? is this permanent?
A
- If they are solitary, they are temporary
- If there are a group of them, then they are permanent
10
Q
Peyer’s Patches
A
- permanent lymphatic aggregates that contain B and T lymphocytes
- present in the ileum
11
Q
lymphatic tissue in the appendix
A
-has permanent aggregations of lymphatic nodules in the lamina propria and the submucosa of the appendix
12
Q
BALT
A
- permanent lymphatic aggregates present and in the wall of the bronchi
13
Q
The pharyngeal, palatine, and lingual tonsils are aggregations of? what kind of lymphocytes reside here?
A
lymphatic nodules
B lymphocytes
14
Q
pharyngeal tonsil
where?
type of epithelium?
special structural feature
A
- “adenoid”
- reside in nasopharynx
- covered by pseudostratified coloumnar epithelium with cilia
- has pleats instead of crypts
15
Q
Palatine tonsils
where?
what kind of epithelium?
special structural feature?
A
-pair
-lateral wall of oropharynx
has a partial cap where the tonsil sits
-stratified squamous nonkertainized epithelium
-have multiple lymphatic nodules that have germinal center (where B lymphocytes produced)
16
Q
lingual tonsils
where?
type of epithelium?
special structural feature?
A
- small bumps on dorsal posterior 1/3 of tongue
- covered by stratified squamous nonkeratinized epithelium
- has crypts
17
Q
lymph nodes
A
- lymphatic organs located along the path of lymphatic vessels
- serve as a filter for lymph before it passes into the blood vascular system
- covered by thin capsule of dense connective tissue
18
Q
what surrounds the lymph node?
A
capsule- has fenestrations called trabeculae that extend from the capsule into the lymph node carrying blood vessels and nerves
19
Q
what are the two surfaces of the lymph nodes and what are their features?
A
- concave side- Hilum- site where blood vessels (artery enters and vein leaves) and efferent lymphatic vessels (leave) node
- convex side-where afferent lymph vessels are- control the amount of lymph entering the lymph node
20
Q
What are the sinuses that exist in the lymph node?
A
- subcapsular
- trabechular
- medullary
21
Q
subcapsular sinus
A
- deep to connective tissue capsule; drains into trabecular sinuses
22
Q
Trabechular Sinus
A
- receive lymph from subcapsular sinuses and drains in to the medullary sinus
- separate lymphatic nodules
- drain into the medullary sinuses (middle)
- NOT HOLLOW- contain reticular cells in a meshwork and have macrophages that phagocytose particulate matter as lymph passes thru them
- have endothelial cells that allow for lymphatic cells to enter and exit the sinus by passing thru them
23
Q
medullary sinus
A
- wide
- empty out the lymph via the efferent lymph vessels
24
Q
flow of lymph
A
- afferent lymph vessels have valves on them that allow flow of lymph into lymph node
- enter the subcapsular sinus
- go thru the trabechular sinus
- empty into the medullary sinus and exit out of the efferent lymph vessel at the hilum
25
What are some characteristics of reticular tissue in the lymph node? What 4 types of cells are in the reticular tissue?
- has reticular cells and fibers that form a 3D network that suspends the cells and maintains its structure
- cells in the reticular meshwork are:
1) reticular cells that are like fibroblasts that synthesize and secrete collagen type 3 to form reticular fibers and ground substance
2) dendritic cells- antigen presenting cells that monitor for foreign invaders
3) Macrophages- phagocytic antigen presenting cells
4) follicular dendritic cells-antigen/antibody complexes
26
What are the nodules like in the cortex of lymph nodes?
- cortex contains B lymphocytes
- germinal centers of the nodules contain dendritic reticular cells that bind new immunoglobulins and when the same antigen is present, also binds and presents B and T lymphocytes
- more cells than then medulla
27
paracortex
- deep cortex
- no nodules
- contains T lymphocytes
- Has POSTCAPILLARY VENULES- that B and T lymphocytes escape from the bloodstream into so that they can enter the paracortex of the lymph node
- B lymphocytes pass into the cortex whereas the T lymphocytes stay in the paracortex
28
how does most lymph enter the lymph nodes?
- via the high endothelial venules of the paracortex (90%)
| - 10% enter thru the afferent lymph vessels
29
medulla
- has medullary cords that have reticular fibers and cells
| - contain lymphocytes, plasma cells, dendritic cells, and macrophages
30
Thymus
structure?
function?
what does it lack?
- consists of 2 lobes that are broken up into lobules by trabeculae that don't fully break them up and allow the lobules to be continuous with one another
- where T lymphocytes mature- T lymphocytes made in the bone marrow and then travels to thymus to mature, move out into the cortex of the thymus and then exit
- LACK AFFARENT LYMPHATIC VESSELS!, no B lymphocytes, no trabeculae, no 3D reticular fiber meshwork, no nodules, no sinuses
31
what is used in place of the 3D reticular fibers in the thymus in order to hold and suspend the T lymphocytes in place and prevent them from becoming a clump?
- EPITHELIORETIULAR CELLS! - 6 types
| - Basically, protect and aim at creating a pristine environment for maturing thymocytes in the cortex
32
how do t lymphocytes mature in the cortex of the thymus
immature t lymphocytes start in the cortex and move in toward the medulla as they mature
if they are not maturing well, they are phagocytosed by macrophages along the way
those that make it to the medulla, enter the vascular system to be delivered to SECONDARY VASCULAR ORGANS
33
type ONE epithelialretiular cells
- in the thymus on the outer edge furthest from medulla
- form a seal around the cortex separating CT and trabeculae
- form a sleeve around the tunica adventicia of vessels
- form occludens jxns sealing the cortex of the thymus with the rest of the body
34
type TWO epithelialretiular cells
- branching, sellate shaped
- form meshwork in the midcortex
- held together via desmosomes
- TEACHERS- involved in thymic cell education
35
Type three epithelialreticular cells
- in deep cortex and the corticomedulary junction
- protein synthesis to make zona occludens
- form seal between medulla and cortex- isolating the two
36
what are the epithelioreticular cells in the medulla of the thymus?
- Type 4-6
- Type 4- associated with 3 and serve as a barrier at corticomedullary jxn
- type 5- form meshwork of medulla
- type 6- form thymic corpuscles called HASSALLS CORPUSCLES
37
Hassalls corpuscles
- made by type 6 endothelioreticular cells of the medulla of the thymus
- eosinophillic
- have keratinization
38
From inward to outward, name the layers of the blood thymus barrier?
- endothelium
- basal lamina
- macrophages
- type 1 endothelialreticular cells
39
DiGeorge's syndrome
- can't produce t cells due to thymus HYPOPLASIA OR APLASIA
- lack cellularly mediated immune response
- death from infection
- do not have parathyroid glands
40
Spleen
- largest lymphatic organ
- FILTERS THE BLOOD NOT LYMPH
- site of the B and T cells
- It gets rid of old blood cells via macrophages
41
how do blood vessels and nerve fibers enter the spleen?
-its hilum
42
what is the route of vascularization of the spleen?
splenic artery to trabecular artery inside trabeculae, loose trabeculae and tunica adventitia infiltrated by T lymphocytes, surrounded by PAL and called central artery, loses lymphatic sheath and gives rise to pencillar arterioles. then develops into arterial capillaries
43
what is in the paranchyma of the spleen
white pulp with PALS and splenic nodules
marginal zone
red pulp
44
white pulp
in the spleen
has PALS -periarterial lymphatic sheath
contains t lymphocytes thus- thymus dependent zone
Has splenic nodules called malpighian corpuscles with B lymphocytes
45
red pulp
- has splenic cords- called cords of Billroth- splenic cord tissue
- loose framework of reticular fibers
- between fibers are blood cells
- filter blood via macrophages, lymphocytes and dendritic cells
46
splenic sinuses
- in red pulp
- lined by endothelial cells with wide intercellular spaces that allow for passage of blood cells
- drain into pulp veins that drain into trabecular veins
cell bio 3
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