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Histology > lymph > Flashcards

lymph Flashcards

1
Q

lymph tissue

A

it is a type of a connective tissue which consist of lymphocytes.

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2
Q

supporting framework of lymphatic tissues

A

reticular connective tissue that contain reticular fibers and reticular cells

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3
Q

staining of lymph tissue

A

basophilic and stains dark blue or purple stain in H&E staining

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4
Q

categories of lymphatic tissues

A

diffused lymphoid tissue
nodular lymphoid tissue
lymphoid organs

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5
Q

nodular lymphoid tissue overview

A

they are localized aggregates of lymphocytes masses that aren’t encapsulated
also knows as lymphoid follicles, lymphatic follies and lymphatic nodules

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6
Q

overview of lymphoid organs

A

these are massses of lymphatic tissue, surrounded by a connective tissue capsule. also contains diffuse and nodular lymphoid tissues are present

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7
Q

structure of lymphoid nodules

A

dense acumalation of lymphocytes that are not encapsulated.

lymphoid nodules is known as primary lymphoid nodule and secondary lymphoid nodule

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8
Q

primary and secondary lymphoid nodule

A

primary lymphoid nodule is the inactiavte nodule which mainly consist of B lymphocytes whereas when an antigen enter the primary nodule it becomes secondary lymphoid nodule which as a central light staining area GERMINAL CENTER and outer dark staining area the MANTLE ZONE

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9
Q

germinal center

A

germinal center activates when an antigen enters it either free floating or carried by a dendritic cell. it activates the B lymphocytes which undergo mitotsis and make up two immature lymphocytes which are plasmoblast and lymphoblast.
plasmoblast make up the Plasma cells and lymphoblast makes up the B memory cells
also contains dendritic cells (interdigitating dendritic cells) and macrophages

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10
Q

why germinal center stains lighter

A

the immature plasmoblast n lymphoblast nuclei have dispersed chromatin (euchromatin ) there stains lighter than mantle zone

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11
Q

mantle zone

A

contains B lymphocytes in high number with few dendritic cells and macrophages
has heterochromatin and stains darker

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12
Q

primary lymphoid organs are

A

bone marrow and thymus

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13
Q

secondary lymphoid organs are

A

spleen, tonsils and lymph nodes

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14
Q

what is thymus, location of thymus and embryonic orgnis

A

thymus is a primary lymphoid organ that provides the body with T lymphocytes. it is involved in the process of T cell education which is making lymphoblast immunocompetent.
thymus is present in the super mediastinum of the body and it is bilobed
thymus originates from the endodermal cells of the third layer of pharyngeal pouches
endodermal cells derived from the ventral wing of right and left pouches makes the bilobed thymic primordium

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15
Q

TECS

A

thymic epithelial cells or epithelioreticular cells or reticular cells are the cells derived from the endodermal cells. (they differentiate)
when lymphoblast originate in bone marrow invade the thymus they under the T cell education and transformed into immunocompetent T cells,

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16
Q

thymus on histological level

A

thymus is surrounded by a dense connective tissue capsule. there are septa extending from capsule into the thymus substance of each lobe subdividing the thymus parenchyma into incomplete lobules

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17
Q

thymic lobule contains what and what lymphocytes

A

contains middle lighter part medulla which contains large amount of TEC and less T lymphocytes
and the outer cortex region that contains lymphocytes (95%) of the lymphocytes of thymus and less TECs
the thymus lobules contains no lymph nodules
both contains macropahges

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18
Q

thymic coretx

A

thymic cortex stains dark basophilic cause it contains a large number of immature T lymphocytes which are thymocytes
the periphery of cortex contains large lymphoblast that undergo proliferation and make thymocytes, these thymocytes the move towards the medulla ], during this movement through thymus cortex they receive (EDUCATUON) AND become incompetent T lymphocytes

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19
Q

thymic epithelial type I cells

A

these cells are flattened and are present around the periphery of cortex separating from capsule and connective tissue
they surround the capillaries and small arterioles of cortex and have occluding junctions between them which helps in isolating the developing T cells from the blood and connective tissue of thymus

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20
Q

type II thymic epithelial cells

A

these cells are present in the form of sheets, long wide stellate shaped have processes. these cells are present in midcortex and are attached to each other by desmosomes and that’s how they make cytoreticulum that divides the cytoplasm of cortex into small compartments containing developing t lymphocytes ALSO called thymic nurse cells as they take part in T cell education.

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21
Q

type III thymic epithelial cells

A

these cells also have similar processes to type II cells and are attached to each other by occluding junctions, and are present at the junction of thymic medulla and cortex and helps the separate them

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22
Q

type IV thymic epithelial cells

A

these are present at the corticomeddularry junction and are in close association with type III thymic cells. they are bound to each other with adjacent cells with occluding junctions and help to create a barrier between cortex and medulla

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23
Q

Type V thymic epithelial cells

A

these are long sheet like cells with processes that make up the cytoreticulm with the help of desmosomes and divides the medulla in compartments that have t lymphocytes in them
they stain lighter cause of euchromatin

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24
Q

type VI thymic epithelial cells

A

they have the most distinct feature. they make up the thymic corpuscles (Hassall corpuscles) which are isolated mass of closely packed cells
the have flattened nuclei and they are esinophilic. they are joined to each other by desmosomes and they produce cytokines (interleukin 4 and 7) and take part in T CELL education

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25
Q

lymphatics of thymus

A

contains no afferent lymphatics only efferent lymphatics

26
Q

function of thymus in overview

A

their function is to make immu-incompetent T lymphocytes into immunocompetent T lymphocytes

27
Q

pro lymphocytes and prelymphoctes

A

during fetal stage lymphocyte precursors originating in liver move to the thymus. in thymus these lymphoblast proliferate to make prolymphoblast. these prolymphoblast differentiate into immunoincompetent T lymphoblast, thymocytes which are also pre-Tlymphocytes WHICH moves towards the medulla in a time period of 2 weeks in which they recieve the thymic cell education

28
Q

what happens when pre-Tlymphocytes move to midcotical region

A

they have t cell receptors and CD4 AND CD8. having both markings is called double positive stage

29
Q

two stage selection process

A

in the first stage type II AND type III TEC present MHC I AND MCH II to the pre-Lymphocytes bound to various antigens and self antigen. if the lymphocytes recognize the antigens bound to MHC I AND MHC II survive passing the first stage known as the positive selection the second stage is in the medulla where macrophages and dendritic cells are presented with self antigens and if the lymphocytes recognize and bind to the antigens and they are engulfed by the macrophages this is called negative selection

30
Q

the cells that take CD4 OR CD8 markers make up the?

A

CD4 makes up the helper t cells and CD8 makes up the cytotoxic T lymphocytes

31
Q

lymph node

A

it is a small, oval bean shaped organ that is placed between the path of lymphatic vessels and act as a immunofilter of the lymph. it has a convex contour except at one distended side which is called as hilum. afferent lymphatic vessels enter from all over the convex surface of the lymph node
it as a connective tissue capsule with collagen fibers and trabeculae in the internal region
also contains dendritic cells, follicular dendritic cells and macrophages

32
Q

lymph node cortex

A

in the cortex the connective tissue trabeculae run perpendicularly to the surface and divide the cortex into incomplete compartment
the cortex is separated from the outer capsule with a space known as subcapsular sinus which has efferent lymphatic vessels and is continuous with cortical sinus

33
Q

cortical lymph node divided into

A

nodular cortex ( has lymph nodules ) and paracortex (no lymphatic nodules )

34
Q

nodular cortex

A

nodular cortex contains both secondary and primary lymphatic nodules
primary lymph nodules doesn’t have germinal center and mantle zone and only has B lymphocytes which take a uniform basophilic stain, the secondary lymph nodule contains germinal center which has lymphoblast and plasmoblast whereas the mantle zone is packed with B lymphocytes

35
Q

paracortex

A

the paracortex mainly contains T lymphocytes and is called THYMUS DEPENDANT ZONE. it has no lymph nodule
the special feature it has are the HIGH ENDOTHELIAL VESSELS which are lined by cuboidal epithelial cells and have special receptors which interact with lymphocytes and facilitate their migration from blood into the paracortex. the t lymphocytes stays in paracortex and B lymphocytes move to the nodular cortex
90% of lymphocytes enter through HEV, it also what water channels which allow the lymph entering the the lymph node to be concentrated
35% of water and electrolytes is moved back to the blood through HEV

36
Q

medulla of lymph node

A

trabeculae are highly branching and fuse with the hilum. these trabeculae make irregular anastomosing cords called medullary cords. these cords have B lymphocytes and plasma cells present between the reticular fibers and reticular cells. intervening between the medullary cord and medullary trabeculae are medullary sinuses

37
Q

spleen

A

spleen is the largest lymphoid organ in the body. it is present in the upper left quadrant of the abdominal cavity. it is an immunological filtration of blood. its sinuses contains dendritic cells and macrophages which filter out the blood passing through it
contains a capsule made of irregular dense connective tissue that also has MYOFIBROBLAST
contains septa that extend into the substance (splenic pulp) and divides the pulp into incomplete compartments

38
Q

red pulp

A

contains large number of erythrocytes, it has cellular cords called splenic cords which are separated by splenic sinusoids

39
Q

splenic cords

A

they contain all types of cells like, B AND T lymphocytes, granular leukocytes, plasma cells, platelets, macrophages and dendritic cells.

40
Q

splenic sinusoids

A
  1. they are composed of fusiform shaped endothelial cells called as stave cells
  2. they have large gaps present between their endothelial cells for the exchange of formed blood elements into the sinusoids and adjacent splenic cord
  3. the endo cells lie on an incomplete basal lamina and
    supported by transversely arranged by reticular fiber
41
Q

white pulp

A

mainly composed of lymphoid tissues surrounding the branches of splenic artery. the lymphoid tissue makes periartrial lymphatic sheath around the splenic arteries
PALS contains T lymphocytes and at some place it also contains lymph nodule contains B lymphocytes which are secondary and contains a germinal center
the arteries that go through the PALS is called CENTRAL ARTERY

42
Q

stains that each splenic pulp picks up

A

the white pulp stains deeply basophilic because it has a large amount of lymphocytes as compared to red pulp

43
Q

penicillar arterioles

A

the branching of arterioles in the red pulp

44
Q

functions of spleen

A

it filters out the blood as the spleens contains APC (macrophages and dendritic cells) which phagocytose bacteria and other foreign material and present these epitomes to b and t lymphocytes which intestates an immune response against the blood borne disease
it also removes the dead RBC and platelets by macrophages

45
Q

Tonsiles

A

these are masses of lymphoid tissues arranged in the form of ring (waldeyers ring ) at the entrance of the oropharynx. these are incompletely encapsulated, aggregates of lymphoid tissue and its free surface is lined by mucosal epithelium
they have no afferent lymphatics and no sinuses

46
Q

waldeyers ring

A

consist of paired (bilateral) palatine tonsils, one lingual and one pharyngeal tonsils.

47
Q

palatine tonsils

A

ovoid masses of lymphoid tissue present between the palatoglossal and palatopharyngeal folds of pharyngeal wall. they are covered by stratified squamous nonkeratinized epithelium which is continuous with the epithelium of oropharynx.
the surface of epithelium dips into interior lymphoid tissue to form tonsillar crypts
tonsillar epithelium contains lymphocytes (B)
THE parenchyma has dense accumulation of lymphoid follicles that contains lymphocytes
dense band present over deep aspect of tonsils known as capsule

48
Q

pharyngeal tonsils

A

present at posterosuperior wall of nasopharynx, covered by pseudostratified squamous epithelium with patches of stratified squamous non keratinized epithelium
doesn’t contains crypts but has lymph nodules beneath the epithelium
also has PLEATS
DEEP aspect is covered by fibrous connective tissue

49
Q

lingual tonsils

A

present in the posterior one third (root of the tongue) covered by stratified squamous epithelium contains crypts whose epithelium is continuous with the epithelium of root tongue (stratified squamous non keratinized epithelium)
beneath the epithelium is present diffused lymphoid and lymph nodules which have germinal centers
a very thin capsule separates the underlying structures

50
Q

diffused lymphoid tissue

A

lose and random distribution of lymphocytes.

51
Q

MALT

A

these are lymphoid tissues present in urogenitial tracts, mucosal lining of the respiratory tract and digestive tracts. it has non encapsulated lymphoid tissue and lymphoid follicles

52
Q

GALT

A

in the digestive tract MALT is called GALT

53
Q

BALT

A

in bronchiole tree MALT is called BALT

54
Q

thymic medulla

A

central region of the thymic lobule, less t lymphocytes so it stains lighter has type IV V AND VI epithelial cells

55
Q

capillaries present in medulla of thymus

A

fenestrated capillaries (that finally drain into postcapillary venule)

56
Q

blood thymus barrier has 3 major components

A
  1. the lining of endothelium of cortical capillaries
  2. type I thymic epithelial cells
  3. macrophages
57
Q

follicular dendritic cells

A

are present in the germinal center of lymphoid follicles (nodules) they they trap immune complexed antigens on their surface and produce chemokimes this play an important role in b lymphocyte response

58
Q

role of lymph node in the filtration of lymph

A

the lymph sinuses (subcapsular, cortical and medullary sinus) are lined by reticular cells and simple squamous epithelial cells, these also have macrophages whose cytoplasmic process intervenes the sinuses with the reticular fibers and cells lined on the fibers
this criss cross meshwork retards the flow of lymph and promotes filtration

59
Q

role of t lymphocytes present in lymph node in immune reponse

A

dendritic cells present in skin and mucosal membrane capture antigens and present the epitope-MCH II to t lymphocytes in paracortex.
t lymphocytes divide to make more helper t cells migrate to the site of antigenic activity

60
Q

role of b lymphocytes in lymph node in immune response

A

as lymph passes to lymph node, any antigenic substances percolates through cortical sinuses gets either attached to the lymphoid follicle dendrite or its phagocytosed by macrophages in the cortical nodule
presentation of antigen to b lymphocytes of cortical nodule activates b lymphocytes they migrate to primary lymphatic nodule, transforms it into secondary lymphatic nodule and makes lymphoblast and plasmoblast
the plasma cells migrate to the medullary cords and travel through the blood and memory b cells either remain in cortex or join the blood

61
Q

what are sheathed capillaries

A

pencillar arterioles divide to form arterial capillaries which make up the sinusoid capillaries. these capillaries are surrounded with APC and are called as sheathed capillaries

62
Q

which type of circulation system is present in spleen of humans

A

open type (terminal arterial capillaries empty blood in splenic cords and it slowly percolates into splenic sinusoids)

Histology (9 decks)

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