In a subclan aery block at outer border of 1st rib, all of the following aeries help in maintaining the circulation to upper limb, EXCEPT?
**Core Concept**
In the context of a subclavian artery block, collateral circulation plays a crucial role in maintaining blood flow to the upper limb. This is achieved through a network of arteries that divert blood from adjacent regions to compensate for the obstruction.
**Why the Correct Answer is Right**
When the subclavian artery is blocked at the outer border of the 1st rib, the blood supply to the upper limb is compromised. However, the collateral circulation helps to maintain blood flow by recruiting arteries from adjacent regions. The following arteries contribute to this collateral circulation:
- **Costocervical trunk** (branch of subclavian artery): This artery gives rise to the supreme intercostal artery, which in turn supplies the upper intercostal spaces and helps to maintain blood flow to the upper limb.
- **Deep cervical artery** (branch of costocervical trunk): This artery provides a collateral pathway to the upper limb by anastomosing with the transverse cervical artery and the suprascapular artery.
- **Thoracoacromial artery** (branch of axillary artery): This artery arises from the axillary artery, which is a branch of the subclavian artery. It provides a collateral pathway to the upper limb by anastomosing with the supreme intercostal artery and the costocervical trunk.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it is not one of the arteries involved in maintaining collateral circulation to the upper limb in the context of a subclavian artery block.
**Option B:** This option is incorrect as it is not one of the arteries involved in maintaining collateral circulation to the upper limb in the context of a subclavian artery block.
**Option D:** This option is incorrect as it is not one of the arteries involved in maintaining collateral circulation to the upper limb in the context of a subclavian artery block.
**Clinical Pearl / High-Yield Fact**
In the context of a subclavian artery block, the costocervical trunk plays a critical role in maintaining collateral circulation to the upper limb. This is because it gives rise to the supreme intercostal artery, which provides a direct pathway to the upper limb.
**Correct Answer: D.**