Deep palmar arch

The deep palmar arch is a major arterial structure in the hand, formed primarily by the radial artery with contributions from the deep branch of the ulnar artery. It plays a key role in providing blood supply to the deep structures of the palm, including the muscles, tendons, and bones of the hand. The deep palmar arch is one of two arterial arches in the hand, the other being the superficial palmar arch, which supplies more superficial tissues.

Location

The deep palmar arch is located deep in the palm of the hand, beneath the flexor tendons and just above the metacarpal bones. It lies close to the base of the metacarpals, typically positioned further away from the surface than the superficial palmar arch. The arch forms a curved loop, beginning on the lateral (radial) side of the hand and extending across to the medial (ulnar) side, near the base of the thumb. It provides branches that run towards the fingers, forming an anastomotic network with the superficial palmar arch.

Structure and Anatomy

The deep palmar arch is a crucial vascular structure in the hand, responsible for the blood supply to its deep muscles, bones, and ligaments. It is formed primarily by the radial artery, with contributions from the deep branch of the ulnar artery. The following provides a detailed anatomical description of its origin, course, branches, and relationships with surrounding structures.

Origin

The deep palmar arch is primarily formed by the radial artery. After the radial artery crosses the wrist and passes into the hand through the anatomical snuffbox, it curves deeply into the palm by passing between the two heads of the first dorsal interosseous muscle. Once in the palm, the radial artery contributes significantly to the formation of the deep palmar arch.

The deep branch of the ulnar artery also contributes to the deep palmar arch. This branch arises from the ulnar artery after it passes through Guyon’s canal. The deep branch joins the radial artery to complete the arch on the medial side of the hand.

Course

The deep palmar arch runs transversely across the palm, deep to the long flexor tendons and just above the metacarpal bones. It is positioned closer to the base of the metacarpals, beneath the muscles of the thenar (thumb) and hypothenar (little finger) eminences, and is located deeper than the superficial palmar arch.

Lateral to Medial Course: The deep palmar arch begins on the lateral side of the hand, where the radial artery enters the palm, and continues medially across the palm toward the ulnar side. It forms a complete or nearly complete loop, with contributions from the deep branch of the ulnar artery.

Branches

The deep palmar arch gives rise to several important branches that supply blood to the deep structures of the hand:

Palmar Metacarpal Arteries

The primary branches of the deep palmar arch are the palmar metacarpal arteries, typically three or four in number. These arteries run along the metacarpal bones and supply the interosseous muscles and the deep structures of the palm.

Anastomosis with Common Palmar Digital Arteries: The palmar metacarpal arteries eventually anastomose (connect) with the common palmar digital arteries that arise from the superficial palmar arch, contributing to the blood supply of the digits.

Perforating Branches

The deep palmar arch also gives off perforating branches that pass through the interosseous spaces to join the dorsal metacarpal arteries. These perforating arteries create connections between the dorsal and palmar vascular networks of the hand.

Perforating Arteries: These arteries are important for ensuring that the dorsal and palmar regions of the hand have an integrated blood supply.

Termination

The deep palmar arch is typically completed on the ulnar side by anastomosing with the deep branch of the ulnar artery. Together, the radial and ulnar contributions form a full or near-complete vascular loop that provides an essential blood supply to the hand’s deep tissues. In some individuals, this connection between the radial and ulnar arteries may be incomplete, but the radial artery typically provides the majority of the blood supply to the deep arch.

Variations

The formation of the deep palmar arch can vary between individuals. Common anatomical variations include:

• Incomplete Arch: In some cases, the deep palmar arch may not form a complete loop. The radial artery may dominate without substantial contributions from the ulnar artery, or the ulnar artery may have a more significant role than usual.
• Additional Branches: In some individuals, the deep palmar arch may give off additional small branches, or there may be variations in the number or course of the palmar metacarpal arteries.

Relationship to Surrounding Structures

The deep palmar arch is closely associated with several important anatomical structures in the hand:

• Flexor Tendons: The deep palmar arch lies beneath the tendons of the flexor digitorum superficialis and flexor digitorum profundus muscles, which are responsible for flexing the fingers.
• Thenar and Hypothenar Muscles: The deep palmar arch is positioned deep to the thenar muscles (responsible for thumb movements) and the hypothenar muscles (responsible for little finger movements). These muscles receive part of their blood supply from the branches of the deep palmar arch.
• Metacarpal Bones: The deep palmar arch runs just above the metacarpal bones, providing blood to these bones through its palmar metacarpal arteries.
• Nerves: The arch is also close to several important nerves of the hand, including the deep branch of the ulnar nerve, which accompanies the deep branch of the ulnar artery as it contributes to the arch.

Function

The deep palmar arch is responsible for supplying oxygenated blood to the deep structures of the hand, including the bones, muscles, and tendons. It plays a critical role in maintaining the vascular integrity of the hand’s deep tissues and ensuring the proper function of these structures. Below is a detailed description of its functions.

Blood Supply to the Deep Muscles of the Hand

One of the primary functions of the deep palmar arch is to supply blood to the deep muscles of the palm, particularly those involved in fine motor control and gripping.

• Interosseous Muscles: The deep palmar arch supplies the palmar interossei and dorsal interossei muscles, which are crucial for finger abduction, adduction, and fine control during precise movements such as pinching and gripping.
• Lumbrical Muscles: These small muscles, which play a key role in flexing the metacarpophalangeal joints (knuckles) and extending the interphalangeal joints (finger joints), also receive their blood supply from the branches of the deep palmar arch.

The deep palmar arch ensures that these muscles receive adequate oxygen and nutrients to maintain hand dexterity and strength.

Blood Supply to the Metacarpal Bones

The deep palmar arch also plays a vital role in supplying blood to the metacarpal bones of the hand.

• Palmar Metacarpal Arteries: The deep palmar arch gives rise to the palmar metacarpal arteries, which run along the shafts of the metacarpal bones. These arteries supply the periosteum (outer layer) of the bones, ensuring bone health and strength.
• Metacarpal Growth and Repair: The continuous blood flow from the deep palmar arch is essential for the growth, maintenance, and repair of the metacarpal bones, particularly after fractures or stress injuries.

By supplying the metacarpal bones, the deep palmar arch contributes to the structural integrity of the hand, ensuring the bones can withstand the forces applied during hand movements.

Blood Supply to the Deep Ligaments and Tendons

The deep palmar arch is responsible for the vascularization of the ligaments and tendons located in the deeper layers of the palm, particularly those that support finger movements and hand stability.

• Flexor Tendons: The deep palmar arch supplies blood to the flexor digitorum profundus tendons, which are responsible for flexing the distal phalanges (the tips of the fingers). These tendons need a steady blood supply to maintain their flexibility and strength, especially during repetitive hand movements.
• Palmar Ligaments: The deep palmar arch also supplies the ligaments that stabilize the joints between the metacarpal bones and phalanges. These ligaments are essential for hand stability and precise finger movements.

Contribution to Collateral Circulation

The deep palmar arch plays a crucial role in forming an anastomotic network with the superficial palmar arch and the dorsal carpal arteries. This network ensures collateral circulation, which provides alternative pathways for blood flow in the hand, particularly during times of arterial compromise.

• Anastomosis with the Superficial Palmar Arch: The deep palmar arch anastomoses with the superficial palmar arch through the palmar metacarpal arteries, which connect with the common palmar digital arteries. This anastomotic network ensures that the fingers and palm continue to receive blood even if one of the arches is compromised.
• Perforating Branches to the Dorsal Carpal Arteries: The deep palmar arch gives off perforating branches that pass through the interosseous spaces to join the dorsal metacarpal arteries. This connection ensures that blood can flow between the palmar and dorsal sides of the hand, providing redundancy in the blood supply.

This collateral circulation is vital in maintaining blood flow in cases of injury, arterial blockage, or surgical procedures where one artery may need to be clamped or ligated.

Support for Hand Function and Dexterity

The deep palmar arch, by supplying blood to the muscles, bones, tendons, and ligaments of the hand, plays a fundamental role in supporting hand function and dexterity.

• Grip Strength: The deep palmar arch supplies the muscles involved in grip, such as the interosseous and lumbrical muscles. These muscles allow for strong and coordinated gripping motions, necessary for holding objects and performing tasks that require hand strength.
• Fine Motor Control: The precise movements of the fingers, such as pinching, writing, or manipulating small objects, depend on the proper blood supply provided by the deep palmar arch. The interosseous and lumbrical muscles, which receive blood from the arch, are directly responsible for these fine motor functions.

The deep palmar arch ensures that the muscles involved in both gross and fine motor skills remain well-nourished and capable of performing complex tasks.

Blood Supply to the Thumb and Index Finger

The deep palmar arch, particularly through its connection with the radial artery, provides an important blood supply to the thumb and index finger, which are critical for many hand functions.

Thenar Muscles: The thenar muscles, which control the movements of the thumb, receive part of their blood supply from the deep palmar arch. These muscles are essential for thumb opposition, allowing the thumb to touch the other fingers, a movement necessary for grip and dexterity.

By supplying the thumb and index finger, the deep palmar arch supports functions like writing, typing, and holding small objects.

Oxygen and Nutrient Delivery

As with all arteries, the fundamental role of the deep palmar arch is to deliver oxygen and nutrients to the tissues it supplies. This ensures the health and function of the hand’s deep structures.

• Tissue Repair: The blood supplied by the deep palmar arch is essential for repairing tissues after injuries, such as fractures, tendon injuries, or muscle strains.
• Bone Maintenance: Continuous blood flow helps maintain the health and density of the bones in the hand, preventing degenerative conditions and promoting healing after fractures.

Clinical Significance

The deep palmar arch is clinically significant because it provides critical blood supply to the deep structures of the hand, including muscles, tendons, and bones. Any injury or compromise to this artery can have serious consequences for hand function.

• Hand Trauma: Injuries involving deep lacerations, fractures, or penetrating trauma to the palm can damage the deep palmar arch, leading to significant bleeding and potential ischemia of the hand. Surgical repair may be required to restore proper blood flow.
• Vascular Assessment: The deep palmar arch plays an important role in hand vascularization and is involved in collateral circulation with the superficial palmar arch. Surgeons assess the integrity of both arches, especially before procedures like radial artery harvesting for coronary artery bypass surgery, to ensure that sufficient blood flow will remain in the hand.
• Arterial Occlusion: Diseases such as atherosclerosis or thromboembolism affecting the deep palmar arch can lead to compromised blood flow in the hand, causing symptoms like pain, coldness, or impaired hand function.