TYPES AND EXAMPLES OF CAPILLARIES

             CAPILLARY:(hair like)

It has two meanings:

1-pertaining to hair or resembling a hair.

2-any one of minute vessels that connect the arterioles and venules, forming a network in nearly all parts of the body.

Walls of capillaries:

The walls of the capillary act as semipermeable membranes for interchange of fluids, gases, nutrients, hormones, vitamins, minerals antibodies, etc., between the blood and tissue fluids. Their diameter varies from 7-9 m.

Types of capillaries;

a) Continuous capillaries:

 In these capillaries, no pores are seen. They are present at following sites:

*Skin.

*Connective tissue

*Skeletal and smooth muscle.

* Lungs.

*Brain.


b) Fenestrated capillaries:

These are those capillaries, the lining endothelial cells of which show characteristic pore system. They are seen at following sites:

*Renal glomeruli.

* Intestinal villi.

* Endocrine glands.

*Pancreas


Sinusoids of sinusoidal capillaries :

These are dilated capillaries and are lined by reticulo-endothelial cells.

Examples:

*Liver

*Spleen

* Parathyroid glands.

*Hypophysis cerebri.

*Carotid and Coccygeal bodies.

*Pancreas (Endocrine portion).

*Haemolymph nodes.


The sinusoids differ from capillaries in four respects :

>The lining is incomplete, irregular, and is formed by endothelial cells and reticuloendothelial cell

 >They are only surrounded by a fine network of reticulin fibres, and are often collapsed when they are empty of blood.

>The sinusoids connect the vessels of same type, i.e., venous vessels whereas a capillary is always a connecting link between arterial and venous vessel

>The sinusoids have a wider lumen (20 μm. or more

Some Interesting Examples of Capillaries~


Erythrocytic capillaries

These are the capillaries of bone marrow of early life which seem to produce erythrocyte

Meigs's capillaries

These are the capillaries of myocardium of the hear

Secretory capillaries

These are extremely thin capillaries present between adjacent gland cell

Arterial capillaries

These are minute capillaries, distal to the arterioles and carry oxygenated bloo

Venous capillaries:

 These are minute capillaries proximal to venules which carry venous blood

Lymphatic or lymph capillaries: These are the capillaries of lymphatic system. Their caliber is slightly greater than the capillaries of blood circulatory system

Bile capillaries or cholangioles or Bile Canaliculi:

These are minute channels formed by apposition of cell membranes of hepatic cells and carry the bile.







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