The hand in the human body is made up of the wrist, palm, and fingers. The most flexible part of the human skeleton, the hand enables us to perform many of our daily activities. When our hand and wrist are not functioning properly, daily activities such as driving a car, bathing, and cooking can become impossible. The hand and wrist are made up of many different bones, muscles, and ligaments that enable a wide range of movements. The hand’s complex anatomy consists of 27 bones, 27 joints, 34 muscles, over 100 ligaments, and tendons, numerous blood vessels, nerves, and soft tissue.
The ligaments are tough bands of connective tissue that connect the bones to support them and keep them in place. Important ligaments of the hand are collateral ligaments, volar plate, dorsal radiocarpal ligaments, ulnocarpal and radioulnar ligaments.
It is important to understand the normal anatomy of the hand to learn about diseases and conditions that can affect our hands.
The wrist is comprised of 8 bones called carpal bones. These wrist bones connect to 5 metacarpal bones that form the palm. Each metacarpal bone connects to one finger or a thumb at a joint called the metacarpophalangeal joint, or MCP joint. This joint is commonly referred to as the knuckle joint. The bones in our fingers and thumb are called phalanges. Each finger has 3 phalanges separated by two joints. The first joint, closest to the knuckle joint, is the proximal interphalangeal joint or PIP joint. The second joint nearer the end of the finger is called the distal interphalangeal joint, or DIP joint. The thumb in the human body only has 2 phalanges and one interphalangeal joint.
The thickness of the nasal soft tissue varies tremendously from the cephalic portion to the midvault and tip area. The radix and supratip region have thicker soft tissue coverage, while the midvault area has thinner soft tissue coverage. To achieve an optimal dorsal profile and dorsum with a supratip break, this differential soft tissue thickness mandates a frame with a slightly deeper nasion, a lower anterocaudal septal angle, and a 6- to 12-mm tip projection beyond the dorsum, depending on the supratip soft tissue volume. A straight dorsal frame may produce a fuller radix and supra tip area, resulting in a suboptimal rhinoplasty outcome.
The soft tissue components of the nose include skin, muscles, nerves, and vascular tissues. Beneath the dermis lies the superficial fatty panniculus, and under the panniculus is a fibromuscular layer. Thinning of the fibromuscular layer, occurring iatrogenically or naturally as a result of senescence, would reveal any dorsal imperfections and may cause skin wrinkling. Deep to the fibromuscular layer, a fatty layer encases another longitudinal fibrous sheet that links the upper to the lower lateral cartilages.4,5 Release of these fibers facilitates caudal tip rotation. Fibrous intradermal ligaments are uniting the medial crura; their release may result in separation of the domes and widening of the tip. The fibrous layers, overall, play a key role in stabilization of the nasal frame but have no dynamic function.
On the other hand, the musculature of the nose has a very dynamic function, the understanding of which is crucial to the functional and aesthetic outcomes of rhinoplasty. Because these muscles are thin and difficult to visualize, it is a challenge to preserve them.
The significance of these small nasal muscles is evident in patients who suffer from facial paralysis. In the early stages after facial paralysis, even without a significant nasal deviation, these patients demonstrate a notable blockage of the nasal airway on the ipsilateral side to the paralysis. After the nose shifts to the opposite side of the paralytic face, the deviation becomes conspicuous and the airway becomes more constricted. Additionally, in patients in whom the nasal muscles are iatrogenically violated during rhinoplasty, the result is a disconcerting change in the function of the nose–an adverse event that is especially evident in animation. This type of muscle dysfunction is a hallmark of rhinoplasties performed 3 to 4 decades ago when the dissection was conducted in a supraperiosteal plane, irreparably damaging the thin nasal muscles.