Birds Skeletal System: Anatomy of Avian Skeletal System

Birds have a variety of hollow bones with crisscrossing reinforcements for structural strength as part of their skeleton. Birds don't have teeth, and their beaks are lighter. Birds have a fused collarbone that is connected to the location of their flight muscles.

What is Bird’s Skeletal System?

The rest of the systems, organs, and tissues that make up the fowl's body are supported and protected by the skeletal system, which offers a sturdy foundation. Over time, bird bones that resemble those in other animals have evolved to improve the bird's capacity to fly.

Birds are given the capacity to fly, and their physical makeup supports this. Although the skeletal systems of birds and humans are not the same, their skulls and limbs do. Avian skeletal systems are altered based on their intended use.

Features of Bird’s Skeletal System

• The vertebral segments of the bird's backbone are fused together to give the stiffness needed for flight.

• Birds are able to fly more effortlessly because of their proportionately smaller skull sizes when compared to other species.

• Birds have a variety of hollow bones with crisscrossing reinforcements for structural strength as part of their skeleton.

• Birds don't have teeth, and their beaks are lighter.

• Birds have a fused collarbone that is connected to the location of their flight muscles.

Avian Anatomy

Pneumatic bones, or hollow bones with air spaces, make up the respiratory system of birds. These comprise the skull and trunk bones. Nasal cavities and skull bones are one and the same. Vertebrae, pelvic bones, and breastbones are considered trunk bones. In comparison to mammals, there are a lot more cervical bones. They have between 13 and 25 cervical bones, and their flexibility aids in brushing their feathers. Another important group of bones is the medulla, which includes the shoulder, pubic, and limb bones. They are where egg-laying birds get their calcium. Eggshells are thick and sturdy because of the calcium given by medullary bones.

Since aves are toothless animals, they lack powerful jaws. Ave limb organisation is very similar to human limb organisation with certain changes. Most of them have four toes. However, some only have three. Despite having the same number of toes, they are arranged differently depending on the type. For example, parrots, owls, and other birds have four toes, two of which point forward and two of which point back when they are perched.

Axial Skeleton

The skeleton of the bird is well-equipped for flight. Despite being incredibly light, it is robust enough to resist the strains of takeoff, flight, and landing. The joining of many bones into a single ossification, like the pygostyle, is a necessary adaptation. Birds often have fewer bones than other terrestrial animals because of this. Additionally, birds don't have teeth or a proper jaw; instead, they have a beak, which is much lighter. Many young birds have an extension on the tip of their beaks called an egg tooth, which helps them break free from the amniotic egg. Once the egg has been broken, it comes off.

Origin of Feathers

Complex and unusual evolutionary structures include feathers. Contrary to what was once believed, they did not directly evolve from reptilian scales. According to current theories, they developed from the invagination of the epidermis around a dermal papilla's base, followed by an increase in form and function complexity. They developed earlier than birds and even before birds could fly.

Early feathers had a variety of purposes, such as thermal insulation, communication, or water resistance, but not flying or aerodynamics. Feathers are no longer regarded as birds' distinctive and distinguishing features among extinct life forms. On a variety of theropod dinosaurs, modern-looking feathers were visible in a variety of morphologies. Nine dinosaurs from the Cretaceous period had feather-like features.

Skeletal Anatomy

Skull

The skull's few moveable bones are sparse in number. These are the bones of the tongue, the lower jaw, and the roof of the mouth. The eyes are enclosed by huge orbits. Teeth are replaced by beak ridges or sharp edges.

Vertebral Column

The spine is made up of a series of bones called vertebrae. The spinal cord and nerve roots can pass through and are protected by these vertebrae.

• Cervical Vertebrae: The first thoracic vertebral body and the skull are connected by the cervical vertebrae (C).

• Thoracic Vertebrae: Either of the two ribs on each side connects to a thoracic vertebra (T). In chickens, the first three thoracic vertebrae are united.

• Lumbar and Sacral Vertebrae: L and S vertebrae are fused together to form one long synsacrum containing several fused caudal vertebrae.

• Caudal vertebrae: The pygostyle, a single, flattened bone formed by the fusion of the final three to four caudal vertebrae, serves as a point of attachment for multiple tail feathers (rectrices).

Ribs

A flattened arch of bone joined to the sternum and the final cervical or thoracic vertebra. To create a solid ribcage, uncinate processes extend from one rib to the rib next to it. Uncinate processes (stars), which are projections that overlap and fuse to adjacent ribs to generate a more rigid thoracic cage, are present on thoracic ribs (arrows).

Sternum

The breastbone of birds that cannot fly, such as ostriches, is flattened. The sternum of the majority of birds, especially gallinaceous birds, is carinate or keeled and resembles the keel of a boat. The muscles used for flight can attach to a larger surface area as a result.

Gallinaceous birds have a large, flat, but narrow region on their sternum where the flying muscles can be attached on either side.

Pectoral Girdle

To support the wing bones, the pectoral or shoulder girdle is made up of three bones (a "tripod"). The coracoid bone, scapula, and furcula—which is the clavicle—make up the girdle. The glenoid cavity, created by the coracoid and scapula, serves as the attachment point for the humeral head. The foramen triosseum, which serves as a channel for the tendon of the supracoracoideus muscle, an essential flight muscle, is also formed by the coracoids, scapula, and clavicle.

Gallinaceous birds have a large, flat, but narrow region on their sternum where the flying muscles can be attached on either side.

Wing

The humerus, ulna, and radius, as well as carpal bones, carpometacarpus, and digits, make up the skeleton of the wing. When the bird is at rest, the humerus is located near the thoracic cavity and joins the glenoid cavity of the pectoral girdle. To elevate and descend the wing during flight, the supracoracoideus and superficial pectoral muscles' tendon attachments are located on the opposing sides of the humerus.

The Origin of Birds

The question of whether birds originated directly from thecodont reptiles, which lived around 230 million years ago (during the Triassic Period), or from a later lineage, the carnivorous theropod dinosaurs, is at the centre of the argument over the origin of birds. This argument has been contentious for a while. Theropod ancestor theory, which holds that modern birds are the descendants of feathered dinosaurs, has gained significant support towards the start of the twenty-first century. Synapomorphy analysis and enhanced samples of early bipedal theropods provide evidence in favour of this idea.

Facts about Birds Skeletal System

• Hollow bones, commonly known as pneumatised bones, are present in birds. These include air-filled spaces.

• To allow oxygen to enter their bodies while breathing, their lungs extend out over all of their bones. This modification enables the bird to have a larger energy supply during flight.

• The rumour surrounding this hollow bone is that it impairs the bird's strength. In contrast, birds are bulkier compared to other animals of the same size. Since their bones are thick, they are slender, rigid, and hard.