Histology (Blood vessel)

Bismillahirahmanirrahim

Ok.. basically, we have blood vessel that consist of artery and veins. But do you know that there is stages between them. Ok, I start with the important part :

1. Arteries

2. Arterioles

3.Capillaries / Sinusoids

4.Venule

5.Vein

(Can't you see o_O , the stages of blood vessel before it can reach the vein? hee)

Then, cell that made up blood vessel is endothelial cell (endothelium).

 It got flattened endothelial cell. From surface view, it has polygonal shape. The cytoplasm consist of ER, mitochondria, Microfilament and intermediate filament that provide mechanical support to cell.

What is the funtion of endothelial cell?

1. Sensitive towards increase in 

-Pressure of blood

-blood flow

-Oxygen tension

2. Secrete substance that can cause vasodilation

3.Produce factors that control coagulation of blood.

Okay.. now we enter the main topic in Histologic view :)

Actually, arteries can be categorized into 3 types:

1. Elastic artery

2.Muscular artery

3.Arterioles

And each types got those layer :

-Intima

-Media

-Adventitia

"ARTERY"

Muscular artery

For Intima :

Elastic artery : -'thickest'consist of :- endothelium (thin squamous epithelium). Subendothelium:-consist of connective tissue (fibroblast,smooth muscle, collagen). Internal elastic lamina :- not clearly seen.

Muscular artery : this part (intima), is consider 'thinner' than elastic artery. Internal elastic lamina can be seen clearly.Got numerous little fold 

Arterioles : Consist of endothelial and subendothelial. Subendothelial consist of reticular fibre and elastic fibre.

For Media :

Left : muscular artery.
Right : elastic artery

Elastic artery : Is the 'thickest' in this layer. Made up  most of 'elastic fibre' / Lamina of elastin. Got small amount of smooth muscle and collagen fibre.

Muscular artery : 'thinner' compare to elastic in this layer. More 'smooth muscle' in this layer. Got minority elastic fibre and collagen fibre.

Arterioles : For large arterioles:- got 2 layers of smooth ms. For small arteriole :- got single layer of smooth ms.

For Adventitia :

Elastic artery : 'thinner' in adventitia. Consist of fibroblast and collagen fibre.

Muscular artery : 'thicker' in adventitia. Same cotain as elastic.

Arterioles :Thin also. Same contain.

Ok.. not forgetting one critically important part : capillaries.

Capillaries got 2 types :

1. Small - consist of single layer of endothelium

2. Large : consist of 2 or more layer of endothelium

Nucleus can be seen greatly flattened in the cell.

Not only that, it also again categorized into 2 two types :

1. Continuous

Endothelium :- no interruption of layer around lumen.

Adjacent cell of endothelium :- fuse completely. means continous wall of capillaries.

Can be found in the Muscle, Nervous tissue and Connective tissue.

  

2. Fenestrated

There is interruption in endothelium by circular fenestration. Pores exist in 6-7 mm. 

Usually found in pancraeas, intestinal tract, kidney cortex and endocrine gland.

Same function as capillaries but with different features is : Sinusoids.

*It have 'broader' lumen than capillaries

* Can be found in : liver, bone marrow, certain endocrine gland and lymphoid organ.

*Consist of :- 1. endothelium 2. thin layer of connective tissue.

* May be incomplete. Thus, blood have direct contact with tissue.
* Deficiency : -fenestrated & discontinuos of sinusoids (e.g. Spleen)

Some place, rather than endotheial cells, it was replace by macrophages.

For" veins ":

Got 3 types arrange in stages :

1. Postcapillaries/ small vein

2. Medium size vein

3. Large vein

1. Small vein.

* no adventitia.

* The Intima :- consist of endothelial -cuboidal. (Got reticular fibre and pericytes.) subendothelial layer. .

*The media :- Contain contractile pericytes

2. Medium size vein :

The intima : got endothelial, basal lamina, reticular fibre but no internal elastic lamina.

Media : Got smooth muscle fibre. Thinner. Loose organise. A lot of 'collagen fibre'. Minor elastic and fibroblast.

Adventitia : Collagenous. Thickest.bundle of collagen and elastic fibre.

3. Large veins :

Intima : Got endothelium. Basal lamina. Reticular fibre and sub endothelial (thick:-fibroblast and elastic fibre)

Media : Thin. Circularly arrange- smooth muscle. Loosely arrange- connective tissue. (e.g. in pulmonary vein and portal vein)

Adventitia : 'Thick'. Rich of elastic fibre. Got vaso vasorum, to supply oxygen tissue. Found in inferior vena cava.Longitudinally smooth muscle and connective tissue.

Comparison between large artery and large vein.

Large Artery  
Tunica media : Thickest coat   

Tunica adventitia : Thin. (Fibroblast & collagen fibre)      

Vaso vasorum : present         

Large Vein

Tunica media : Thinner layer

Tunica adventitia : Thick. (Elastic and collagen fibre)

Vaso vasorum : seen

Okay.. what type of disoder that people usually get?

1. Arteriosclerosis : hardening of arteries due to thickening of collagen

2. Atherosclerosis : hardening of arterial wall due to atheroma (fibrous fatty tissue)

3. Aneurysm : ballooning of weak part of arterial wall.

4. Veins :- * varicosities and thrombosis due to impair valve in vein.
*Obstruction of lymphatic vessels due excessive fluid at tissue then produce edema.