The distal-most portion of the upper extremity is the human hand. The hand is composed of particular bones to which different muscles are joined as well as various neurovascular structures that are in charge of drainage and stimulation. However, only a part of the hand’s range of motion may be attributed to its intrinsic muscles.
It is composed of the wrist joint, carpal, metacarpal, and phalange bones. The digits consist of a medial thumb with two phalanges (when the palm is down) and four fingers with three phalanges each.
Except for humans, all vertebrates use their hands primarily for movement. Bipedal movement in humans frees up the hands for primarily manipulative functions.
Table of Contents
Carpal Bones
The wrist has eight irregular bones called carpal bones (or carpus). These bones connect the proximal ends of the metacarpal bones to the distal ends of the long forearm bones (radius and ulna).
Proximal and distal rows comprise the two rows of carpal bones. The lunate, scaphoid, pisiform and triquetrum bones comprise the proximal row of carpal bones. The distal row contains the trapezoid, trapezium, hamate and capitate bones.
Each carpal bone is distinct in shape and multifunctional, allowing them to articulate with various nearby forearm and hand bones, muscles, and ligaments. Thus, the carpal bones give the soft tissues of hands flexibility and various movements. Additionally, they provide most of the skeletal structure of the wrist, facilitating the passage of different neurovascular systems of the hand.
Metacarpal Bones
The metacarpal bones (metacarpus) are a collection of five bones between the carpal bones (carpus) and phalanges. Each metacarpal bone has a shaft, a distal head, and a broad proximal base. These bones are short, yet they are categorised as long bones because they have similar structural traits to long bones.
The metacarpal bones join the carpal bones at their bases (proximal ends) and the proximal phalanges at their heads (distal ends). They are numbered 1-5 in the radio-ulnar direction:
- Metacarpal I: Thumb
- Metacarpal II: Index finger
- Metacarpal III: Middle finger
- Metacarpal IV: Ring finger
- Metacarpal V: Little finger
Phalanges
The small bones that constitute the bony centre of fingers (digits) are known as the phalanges. These phalanges are small bones, but they are referred to as long bones due to their structure. Each phalanx has a proximal base, a distal head, and a shaft.
Each hand has fourteen phalanges; the thumb only has two (proximal and distal), while the other four digits each have three (proximal, middle, and distal).
Interphalangeal joints connect the phalanges, and nutritive rami to phalanges, which originate from the palmar digital arteries, provide vascularisation for the phalanges.
Related Links:
Main Page: BYJU’S NEET
Frequently Asked Questions – FAQs
How many bones are there in a human hand?
What type of joints are there in the hand and wrist?
Hinge joint: It allows bones to move back and forth in one direction with restricted motion in other planes, similar to the hinge on a door. Examples involve the elbow joint and the knee joint.
Condyloid joints: They don’t allow rotation, only rotation. Examples are the joints in our fingers and jaw.
Pivot joints: Also known as the rotary or trochoid joints, they are a specific form of joint where a cylinder-shaped bone is attached to a ring-shaped bone, and the cylinder-shaped bone is capable of rotating inside the ring-shaped bone. Examples include the neck joint between the first and second vertebrae and the joint that rotates our forearm at the junction of the ulna and radius bones.
Gliding joint: It is also known as the plane joint. The gliding joint is a synovial joint between two bones that contact on flat articulating surfaces and allows gliding or sliding motion. An example includes the joint in our wrist.
Saddle joint: It is a synovial joint, also known as a sellar joint, with opposing surfaces that are reciprocally concave and convex. It is located at the base of our thumb. It does not allow rotation.
Comments