tunica externa

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tunica

 [too´nĭ-kah] (L.)
a tunic or coat; used in anatomic nomenclature to designate a membranous covering of an organ or a distinct layer of the wall of a hollow structure, as a blood vessel.
tunica adventi´tia the outer coat of various tubular structures.
tunica albugi´nea a dense white fibrous sheath that encloses a part or organ, such as the testicle or ovary.
tunica conjuncti´va the conjunctiva.
tunica dar´tos dartos.
tunica exter´na an outer coat, such as the fibroelastic coat of a blood vessel.
tunica inter´na an inner coat or layer.
tunica in´tima the innermost coat of a blood vessel; called also Bichat's tunic.
tunica me´dia the muscular middle coat of a blood vessel.
tunica muco´sa the mucous membrane lining of various tubular structures.
tunica muscula´ris the muscular coat or layer surrounding the tela submucosa in most portions of the digestive, respiratory, urinary, and genital tracts.
tunica pro´pria the proper coat or layer of a part, as distinguished from an investing membrane.
tunica sero´sa the membrane lining the external walls of the body cavities and reflected over the surfaces of protruding organs; it secretes a watery exudate.
tunica vagina´lis tes´tis the serous membrane covering the front and sides of the testis and epididymis.
tunica vasculo´sa a vascular coat, or a layer well supplied with blood vessels.

tu·ni·ca ex·ter·na

[TA]
1. the outer of two or more enveloping layers of any structure;
2. specifically, the outer fibroelastic coat of a blood or lymph vessel.
Synonym(s): tunica extima [TA]

tunica externa

The outermost layer of a blood vessel, which envelops the tunica media. It is composed largely of collagen and elastic lamina.

Pathology
The most commonly acquired condition that affects the tunica externa is vitamin C deficiency (scurvy), which results in defective collagen synthesis.

tu·ni·ca ex·ter·na

(tū'ni-kă eks-ter'nă) [TA]
1. The outer of two or more enveloping layers of any structure;
2. Specifically, the outer fibroelastic coat of a blood or lymph vessel.