Talk:Draft 2016: Difference between revisions

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==Spleen==
==Spleen==
===Spleen Anatomy===
===Thymus Anatomy===
{|
{|
! Spleen Anatomy
! Thymus Anatomy
|-
|-
| [[File:Spleen anatomy.jpg|400px]]
| [[File:Spleen anatomy.jpg|400px]]
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| almost entirely surrounded by peritoneum adherent to its capsule
| almost entirely surrounded by peritoneum adherent to its capsule
|}
|}
===Thymus Functions===
{| class="wikitable mw-collapsible mw-collapsed"
{| class="wikitable mw-collapsible mw-collapsed"
! Spleen Functions 
! Thymus Functions 
|-  
|-  
|  
|  
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# '''Blood Reservoir''' - The sinuses in the spleen also act as a reservoir for blood. In emergencies (haemorrhage) smooth muscle in the vessel walls and in the capsule of the spleen contracts, squeezes blood out of the spleen into the general circulation.
# '''Blood Reservoir''' - The sinuses in the spleen also act as a reservoir for blood. In emergencies (haemorrhage) smooth muscle in the vessel walls and in the capsule of the spleen contracts, squeezes blood out of the spleen into the general circulation.
|}
|}
===Thymus Structure===


{| class="wikitable mw-collapsible mw-collapsed"
{| class="wikitable mw-collapsible mw-collapsed"
! Spleen Structure 
! Thymus Structure 
|-  
|-  
|  [[File:Spleen structure cartoon 01.jpg|800px]]
|  [[File:Spleen structure cartoon 01.jpg|800px]]
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|}
|}


===Thymus Histology===
{| class="wikitable mw-collapsible mw-collapsed"
{| class="wikitable mw-collapsible mw-collapsed"
! Spleen Histology 
! Thymus Histology 
|-  
|-  
|   
|   
* Capsule with trabeculae (dense connective tissue)
* Capsule with trabeculae (dense connective tissue)
* Reticular fibroblasts - reticular fibres (Type III collagen)


[[File:Spleen histology 06.jpg|600px]]
[[File:Spleen histology 06.jpg|600px]]


{|
 
|-
! bgcolor="CEDFF2" width=200px|White Pulp
! bgcolor="salmon" width=200px|Red Pulp
|-
| valign=top|
* lymph follicle
* germinal center
* central artery
** periarterial lymphoid sheath (PALS)
| valign=top|
* splenic cords
** macrophages
** reticular fibroblasts
* splenic sinuses
** endothelium (discontinuous structure)
|}
{|
{|
! Overview - red and white pulp
! Overview - red and white pulp
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|}
|}


{{Spleen Histology}}
{{Thymus Histology}}
|}
 
 
 
==Thymus==
[[File:Lymphatic-system-thymus.jpg|600px]]
 
[[File:Thymus cartoon.jpg|thumb|Adult Thymus]]
[[File:Gray1178.jpg|thumb|Fetal thymus anatomy]]
Gross Anatomy
* Superior mediastinum, anterior to heart
* Bilobed lymphoepithelial organ
{|
| Histology
* Contains reticular cells but no fibers
* Stem lymphocytes
** proliferate and differentiate
** forms long-lived T- lymphocytes
* removes auto-reactive  T-lymphocytes (negative selection)
| {{Thymus Movie 1}}
|}
===Thymus Cells===
{|
|-bgcolor="F5FAFF"
! Reticular cells
! Macrophages
! Lymphocytes
|-
|
* Abundant, eosinophilic, large, ovoid and light nucleus 1-2 nucleoli
* sheathe cortical capillaries
* form an epitheloid layer
* maintain microenvironment for development of T-lymphocytes in cortex (thymic epitheliocytes)
|
* cortex and medulla
* difficult to distinguish from reticular cells in {{HE}}
* remove auto-reactive  T-lymphocytes
|
* located in cortex and medulla
* more numerous (denser) in cortex
* majority are developing T-lymphocytes (= thymic lymphocytes or thymocytes)
|}
 
===Development Changes===
{Changes with age
Overall Size
* birth 10-15 g
* puberty 30-40 g
* after puberty - decreases in size (involution)
* middle-aged 10 g, replaced by adipose tissue
 
Histology
<gallery>
File:Fetal thymus.jpg|Fetal thymus
File:Thymus - young 01.jpg‎|Young medulla
File:Thymus - young 02.jpg‎|Young cortex
</gallery>
 
===Adult Thymus===
{|
| [[File:Thymus adult.jpg|300px]]
|
 
* Cortical lymphoid tissue is replaced by adipose tissue (involution)
* Increase in size of thymic corpuscles
* '''Thymic corpuscle''' - (Hassall’s corpuscle) mass of concentric epithelioreticular cells.
 
[[File:Thymus - young 01.jpg|300px]]
 
|}
|}

Revision as of 15:44, 26 February 2016

Spleen

Thymus Anatomy

Thymus Anatomy
Spleen anatomy.jpg Gray1039.jpg
left hypochondriac region almost entirely surrounded by peritoneum adherent to its capsule

Thymus Functions

Thymus Functions 
  1. Immune - filters blood in much the way that the lymph nodes filter lymph.
    1. Lymphocytes in the spleen react to pathogens in the blood and attempt to destroy them.
    2. Macrophages then engulf the resulting debris, the damaged cells, and the other large particles.
  2. Red Blood Cell Removal - spleen (and liver) removes old and damaged erythrocytes from the circulating blood.
  3. Blood Reservoir - The sinuses in the spleen also act as a reservoir for blood. In emergencies (haemorrhage) smooth muscle in the vessel walls and in the capsule of the spleen contracts, squeezes blood out of the spleen into the general circulation.

Thymus Structure

Thymus Structure 
Spleen structure cartoon 01.jpg
  • afferent splenic artery branches into central arterioles, which are sheathed by white pulp areas.
  • white pulp areas consist of the T-cell zone (also known as the periarteriolar lymphoid sheath, PALS), arterioles and B-cell follicles.
  • arterioles end in cords in the red pulp, from where the blood runs into venous sinuses that collect into the efferent splenic vein.
  • larger arteries and veins run together in connective-tissue trabeculae, which are continuous with the capsule that surrounds the spleen.

Thymus Histology

Thymus Histology 
  • Capsule with trabeculae (dense connective tissue)

Spleen histology 06.jpg


Overview - red and white pulp Overview - blood vessels Red pulp
Spleen histology 01.jpg Spleen histology 02.jpg Spleen histology 03.jpg

Reticular Fibers (type III collagen) act as supporting meshwork (can be seen in Silver stained preparations)

Spleen histology 05.jpg Spleen histology 04.jpg
Thymus Histology: Fetal Thymus overview | Fetal Thymus Medulla | Fetal Thymus Cortex | Adult Thymus | unlabeled fetal overview | unlabeled fetal medulla |unlabeled fetal thymic corpuscle |unlabeled fetal cortex | unlabeled adult overview | Category:Thymus | Immune System Development


Thymus

Lymphatic-system-thymus.jpg

Adult Thymus
Fetal thymus anatomy

Gross Anatomy

  • Superior mediastinum, anterior to heart
  • Bilobed lymphoepithelial organ
Histology
  • Contains reticular cells but no fibers
  • Stem lymphocytes
    • proliferate and differentiate
    • forms long-lived T- lymphocytes
  • removes auto-reactive T-lymphocytes (negative selection)
Mouse adult thymus 11.jpg
 ‎‎Thymus 1
Page | Play

Thymus Cells

Reticular cells Macrophages Lymphocytes
  • Abundant, eosinophilic, large, ovoid and light nucleus 1-2 nucleoli
  • sheathe cortical capillaries
  • form an epitheloid layer
  • maintain microenvironment for development of T-lymphocytes in cortex (thymic epitheliocytes)
  • cortex and medulla
  • difficult to distinguish from reticular cells in (Stain - Haematoxylin Eosin)
  • remove auto-reactive T-lymphocytes
  • located in cortex and medulla
  • more numerous (denser) in cortex
  • majority are developing T-lymphocytes (= thymic lymphocytes or thymocytes)

Development Changes

{Changes with age Overall Size

  • birth 10-15 g
  • puberty 30-40 g
  • after puberty - decreases in size (involution)
  • middle-aged 10 g, replaced by adipose tissue

Histology

  • Fetal thymus

    Fetal thymus

  • Young medulla

    Young medulla

  • Young cortex

    Young cortex

Adult Thymus

Thymus adult.jpg
  • Cortical lymphoid tissue is replaced by adipose tissue (involution)
  • Increase in size of thymic corpuscles
  • Thymic corpuscle - (Hassall’s corpuscle) mass of concentric epithelioreticular cells.

Thymus - young 01.jpg

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