KEY NOTES CHAPTER 1: GENERAL PRINCIPLES (B) Blood supply to the skin.

Question 0

What is the interconnecting system composed of?

Answer 0

1. Fasciocutaneous (or septocutaneous) vessels
   - directly traverse fascial septa, e.g. limbs.
2. Musculocutanous vessels
   - indirectly to skin via multiple perforating muscular branches, e.g. torso.

Question 1

How does blood reach the skin?

Answer 1

• Deep vessels supply
• Interconnecting vessels which supply
• Vascular plexuses of fascia, sc tissue and skin.

Question 2

Name the vascular plexuses of fascia, subcut tissue and skin.

Answer 2

1. Subfascial - under deep fascia
2. Prefascial - superficial to deep fascia. Main supply = fc vessels, predominant in limbs.
3. Subcutaneous - superficial fascia. Main supply mc vessels, predominant in torso.
4. Subdermal - main plexus supplying skin.
5. Dermal - mainly arterioles, important in thermoregulation.
6. Subepidermal - nutrition and thermoregulation.
   N.B. epidermis contains no blood vessels.

Question 3

What is an angiosome?

Answer 3

A 3D composite block of tissue supplied by a named artery.

Question 4

Who are the names associated with describing angiosomes?

Answer 4

Manchot 1889.
Salmon 1930.
Taylor and Palmer - coined angiosome.

Question 5

What are the anatomical, dynamic and potential territories of an artery?

Answer 5

Anatomical - area into which vessel ramifies before anastomosing with adjacent vessels.
Dynamic - area into which fluorescein extends into after injection into artery.
Potential - area that can be included if flap was delayed.

Question 6

What are choke vessels?

Answer 6

Vessels that pass between anatomical territories.

Question 7

Describe the different theories of the TRAM flap angiosomes.

Answer 7

Zone 1 - ipsilateral DIEA musculocutaneous perforators supplies the anatomical territory

Hartrampf 1982.
Zone 2 = contralateral to midline.

Holm 2006.
Zone 2 = lateral to zone 1 (anatomical territory of SCIA). Perfusion from DIEA crosses 1 set of choke vessels.
Zone 3 = contralateral to midline = dynamic territory.

Zone 4 - perfusion crosses 2 sets of choke vessels

Question 8

How is blood flow controlled by the muscular tone of vessels?

Answer 8

1. Myogenic theory
   - pressure of blood within vessels (increased intraluminal pressure, vessels constrict).
2. Neural innervation
   - sympathetic control of arterioles, AVAs and pre-capillary sphincters. (Cutaneous blood flow is reduced by increased tone of arterioles, decreased AVA tone and increased pre-capillary sphincter tone.)
3. Humoral factors
   (- Epinephrine, norepinephrine, serotonin, TXA2, PG cause vasoconstriction.
   - Histamine, bradykinin and PGE1 cause vasodilatation, as does low O2, high CO2 and acidosis).
4. Temperature - heat causes vasodilatation and increased flow through AVAs, bypassing capillaries.

Question 9

What is the delay phenomenon?

Answer 9

Any preop manoeuvre that results in increased flap survival.
1. Increased axiality of blood flow.
2. Tolerance to ischaemia.
3. Sympathectomy vasodilatation theory.
4. Intraflap shunting hypothesis.
5. Hyperadrenergic state.
Unifying theory (Pearl) - all 5.