Manus (anatomy)

Manus (Anatomy)

The front foot of a European hamster, illustrating the structure of the manus.

The manus is the anatomical term for the distal segment of the forelimb in tetrapods, including humans, mammals, and other vertebrates. It is commonly referred to as the "hand" in humans and the "forepaw" in quadrupeds. The manus is a complex structure that plays a crucial role in various functions such as manipulation, locomotion, and sensory perception.

Anatomy of the Manus

The manus consists of several key components:

Bones

The skeletal structure of the manus includes the following bones:

• Carpals: These are the small bones that form the wrist in humans and the equivalent joint in other animals. They provide flexibility and support for the hand.
• Metacarpals: These are the long bones of the hand that connect the carpals to the phalanges. In humans, there are five metacarpals, one for each digit.
• Phalanges: These are the bones of the fingers or digits. Each finger typically has three phalanges (proximal, middle, and distal), except for the thumb, which has two.

Muscles and Tendons

The manus is controlled by a complex array of muscles and tendons that allow for precise movements. These include:

• Flexor muscles: These muscles are responsible for bending the fingers and wrist.
• Extensor muscles: These muscles straighten the fingers and wrist.
• Intrinsic muscles: These are small muscles located within the hand itself, allowing for fine motor control.

Nerves and Blood Supply

The manus is innervated by several major nerves, including the median nerve, ulnar nerve, and radial nerve. These nerves provide sensation and motor control to the hand. The blood supply to the manus is primarily through the radial artery and ulnar artery.

Function

The manus serves several important functions:

• Manipulation: In humans, the opposable thumb allows for grasping and manipulating objects, a key factor in tool use and fine motor skills.
• Locomotion: In quadrupeds, the manus is involved in walking, running, and climbing.
• Sensory Perception: The fingertips are rich in sensory receptors, providing detailed information about texture, temperature, and pressure.

Evolutionary Perspective

The structure of the manus has evolved significantly across different species to adapt to various ecological niches. For example, the manus of primates is adapted for grasping and climbing, while in bats, it has evolved into wings for flight.

Related Pages

• Hand
• Forelimb
• Tetrapod
• Opposable thumb