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First Year Term 1 > Lymphoid Histology > Flashcards

Lymphoid Histology Flashcards

1
Q

Function of the Lymph

A

To respond to any foreign body, microorganism, infection etc- involved in the immune response

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2
Q

What makes something a primary lymphoid organ? and what is one

A
  1. Needs to have a partial or complete connective tissue capsule surrounding the organ
  2. Organ where the lymphocytes receive immunocompetence (bone marrow and thymus)
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3
Q

What is a secondary lymphoid organ?

A

organs that receive lymphocytes for residence that have received immunocompetence in the primary lymphoid organs (lymph nodes, spleen, tonsils)

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4
Q

What are types of resistance to disease?

A

Non specific = innate = present at birth
1. First - skin and mucous membranes: protective surfaces/ secretions (tears, saliva, mucus)
2. Second- internal defences: including inflammation and phagocytosis by macrophages!
During life develop specific immunity!

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5
Q

Where does maturation of B and T cells occur and then where do they go?

A

In Primary lymphoid organs (B = bone marrow and T = thymus)
Then travel to secondary lymphoid organs where clonal expansion occurs, differentiate into diff cells which are then involved in specific immune response

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6
Q

What is lymphoid tissue made up of?

A

aggregates of lymphocytes and associated cells of the immune system

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7
Q

What is the thymus?

A

A primary lymphoid organ - site of maturation for T cells

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8
Q

What is the structured morphology (internal structure) of the Thymus?

A
  1. Divided into 2 lobes, left and right. within = made up of smaller lobules
  2. Septa are invaginations of the connective tissue capsule which divide the cortex (only) into lobes = support
  3. Darker (outer) region of the lobe is the cortex
  4. Inner (lighter) region is the medulla
  5. connective tissue capsule surrounds entire organ and supports
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9
Q

What type of organ is the Lymph node?

A

A secondary lymphoid organ

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10
Q

What is the paradox of the lymph nodes?

A
  1. to act as barriers to the spread of infection and tumours by containing and destroying come antigens
  2. facilitate their spread through the lymphatic circulation: METASTASIS
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11
Q

How are the lymph important in clinical examination?

A

Swelling indicates disease

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12
Q

What is the structural morphology of the Lymph node? (not pigs or ruminants)

A
  1. Bean Shape
  2. Outer semi circle is the cortex, inner the medulla
  3. surrounded by a connective tissue capsule - connective tissue septa runs from capsule into medulla
  4. some fat adipose tissue surrounds connective tissue
  5. Afferent Lymphatic Vessels are tiny vessels that ENTER the organ at outer convex part, collect lymph from different tissues.
  6. Efferent lymphatic vessels where lymph EXITS at the HILUM which is a depression and where the blood vessels are.
  7. Vein- blood leaves at hilum
  8. Artery where blood enters
  9. trabecula invaginate in
  10. contains B and T cells
  11. Para cortical centre between medulla and cortex
  12. Lymphoid follicles = circular bit in cortex
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13
Q

Focus on outer capsule what would you expect to see?

A
  1. Afferent lymphatic vessels within the capsule (simple squarmous epithelial/ endothelium with flattened bulging nuclei)
  2. Blood supply (circular)
  3. Subcapsular sinus on inside which is followed by lymphocytes in cortex
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14
Q

What is in the cortex and describe its structure

A
  1. Lymphoid follicle
  2. Lightly stained zone (germinal centre) - B cells which have differentiated into plasma cells - antibodies) (enlarged nuclei)
  3. Darker outer circumference - T cells
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15
Q

Within the medullary region what can you identify

A
  1. Epithelial cells embedded = called Hassall’s Corpuscles
  2. function not known - believed to respond to foreign bodies
  3. circular profile = prominant = looks like thumb print!
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16
Q

How does the pig and ruminant lymph node structure differ?

A
  1. structural arrangement reverses
  2. cortex inverted = inside
  3. medullary = outside
  4. efferent lymph vessles on outer
  5. afferent on HILUM
  6. BV enter from convex surface
17
Q

What is the blood vessel supply to a lymph node?

A
  1. Arteries and veins at indentation (HILUM/HILUS) on concave surface
18
Q

What structures would you expect to see in the outer lymph capsule?

A
  1. BV
  2. Afferent lymphatic vessel
  3. Valve
  4. SIMPLE SQUAMOUS EPITHELIUM - flattened bulging nuclei
  5. Subscapular sinus beneath connective tissue
19
Q

What do lymph nodes look like

A
  1. circular shapes in the cortex

2. Lighter inside centre: germinal centre B cell generation = lighter stain

20
Q

What type of lymph organ is the spleen and what is it involved in?

A
  1. Secondary lymph organ

2. involved in blood filtration rather than lymph itself

21
Q

Roughly describe gross anatomy of the spleen

A
  1. not quite circular
  2. lower renal depression/ fossa = no functional importance
  3. Ventral aspect = Hilum, where vein and artery is
22
Q

What is the difference in organ shape of the spleen

A
  1. horse - sickle shaped
  2. Cattle = oblong
  3. Dog = dumbell shape
23
Q

What histological features can you identify of the spleen

A
  1. White pulp - aggregates of T lymphocytes near arterioles that are distributing blood
    Middle = artery
    whitest bit = germinal centre = B cells
  2. red pulp - RBC
24
Q

What are the different categories + examples of lymphoid organs and tissues

A
  1. primary organs - bone marrow and thymus
  2. Secondary organs: spleen and lymph node
  3. Secondary lymphoid Tissue: tonsils
25
Q

What are the histological characteristics of the thymus at low magnification

A
  1. outer connective tissue capsule encloses entire structure
  2. divided into lobules
  3. outer darkly stained cortex
  4. inner lightly stained medulla
26
Q

What is the subcapsule sinus

A

space right underneath outer connective tissue capsule

27
Q

What is the trabecula

A

invagination of connective tissue right into medullary region

28
Q

What specialised type of cell is within the medullary region of thymus?

A
  1. Hassall’s Corpuscles - lightly stained thumb print

2.

29
Q

What should you expect to see within the connective tissue trabecular

A
  1. trabecular blood vessels - vein with RBC
30
Q

What sort of vessels would you expect to see in the outer capsule

A
  1. blood supple - artery and vein, efferent enter via hilum

2. Afferent vessels outside

31
Q

What is the type and structure of the follicle

A
  1. Primary folicle/ nodule - inactive lymphocyte cells: v dark
  2. Secondary cells: some lighter zone in middle, enlarged cell. Middle = lightly stained B cells, enlarged than T. Actively involved in producing antibodies = germinal centre
32
Q

What are medullary cords?

A
  1. Cord like structure in the medulla, aggregates of B/ T lymphocytes cells, inactive and active cells.

First Year Term 1 (35 decks)

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