Tunica intima
Tunica intima
Also known as: intima, internal elastic lamina
The tunica intima is the innermost layer of a blood vessel wall. It consists of endothelium on a basement membrane and a thin layer of connective tissue beneath it. In arteries it is bounded on the outside by an internal elastic lamina.
Overview
The intima has three components. The endothelium is a single layer of flat cells resting on a basal lamina. Beneath it is a thin subendothelial layer of loose connective tissue, which occasionally contains smooth muscle cells. This layer thickens with age (intimal thickening). In arteries, the internal elastic lamina marks the outer boundary of the intima. It is a fenestrated sheet of elastin whose holes let nutrients diffuse to the inner media. It is most prominent in muscular arteries and looks wavy in sections because arteries contract after death.
In veins the intima is thin. Its folds form the venous valves. The intima contains no blood vessels and is nourished by diffusion from the blood in the lumen.
The intima is where atherosclerosis develops.
Anatomy
- Histology
Simple squamous endothelium, a basal lamina, subendothelial loose connective tissue and, in arteries, a fenestrated internal elastic lamina.
Function
- Provides a smooth, non-thrombogenic, selectively permeable lining.
- Its endothelium regulates vascular tone, clotting and inflammation.
- Forms the venous valves.
Clinical significance
Atherosclerotic plaque
Lipid, foam cells, smooth muscle and fibrous tissue build up in the intima, between the endothelium and the internal elastic lamina.
Neointimal hyperplasia
After a stent is placed or a vein graft is inserted, smooth muscle cells grow into the intima and narrow the vessel again (restenosis). Drug-eluting stents release antiproliferative drugs such as everolimus and sirolimus to prevent this.
Intimal tear in dissection
Aortic dissection starts with a tear in the intima. CT shows the torn intima as a thin flap between the true and false lumens.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.