Bird Anatomy

The anatomy of birds . Including its physiology , it displays many unique adaptations intended, most to ensure the ability to fly. Birds have evolved to possess a light and powerful skeletal and muscular system that, together with the circulatory and respiratory systems, makes them capable of developing very high oxygenation and metabolic activity, and thereby obtaining enough energy to conquer the aerial environment. The development of the beak has conditioned the evolution of a specially adapted digestive system. Because of these anatomical specializations , they have been assigned a class of their own in the chordate phylum .

Summary

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• 1 respiratory system
• 2 circulatory system
• 3 Digestive system
  • 1 Drinking behavior
• 4 Skeletal system
• 5 Skeletal composition
  • 1 Types of skulls
  • 2 Types of spikes
  • 3 Types of feet
• 6Sistema muscular
• 7 Bird Vision
• 8 reproductive system
• 9 Scales
• 10 Beak development
• 11Enlace externo
• 12 Fountains

Respiratory system

Air flows from right (posterior) to left (anterior) through the lungs during both inhalation and exhalation. Key to the respiratory system of the Common Kestrel: 1 cervical air sac, 2 clavicular air sac, 3 cranio-thoracic air sac, 4 caudo-thoracic air sac, 5 abdominal air sac, 6 lung, 7 trachea. Because of the high metabolic rate required for flight, birds have a high oxygen demand. The development of an efficient respiratory system allowed the evolution of flight in birds . the birdsthey ventilate their lungs by means of air sacs, structures that only birds (and therefore perhaps also dinosaurs ) have. These sacs do not play a role in gas exchange, but they do store air and act like bellows, allowing the lungs to keep a fixed volume of fresh air constantly flowing through them. Three different sets of organs perform respiration (physiology).

The anterior air sacs ( interclavicular , cervical , and anterior thoracic), the lungs, and the posterior air sacs (posterior thoracic, and abdominal). The posterior and anterior air sacs, normally nine, expand during inhalation. When inhaled air enters the trachea , half goes to the posterior air sacs and half goes through the lungs to the anterior air sacs. The air sacs contract during exhalation. Air from the anterior air sacs empties directly into the trachea and is expelled through the mouth or nostrils. The posterior air sacs empty into the lungs . The air that passes through the lungs when the bird exhales is expelled through the trachea. Because fresh air flows through the lungs in only one direction, there is no mixing of oxygen-rich air and oxygen -poor , carbon dioxide- rich air , as occurs in mammalian lungs .

Thus the partial pressure of oxygen in a bird ‘s lungs is the same as that of the environment, and thus birds have more efficient gas exchange of both oxygen and carbon dioxide than occurs in mammals . . bird lungs _ _they do not have alveoli, like mammalian lungs , but instead contain millions of tiny passageways known as parabronchi. Air flows through the honeycomb walls of the parabronchi into vesicles called atria, which project radially from the parabronchi. These atria give rise to air capillaries , where the exchange of oxygen and carbon dioxide occurs by diffusion with the blood flowing through the blood capillaries. Birds also lack a diaphragm . the entire body cavityacts like a (tyre) to move air through the lungs .

The active phase of respiration in birds is exhalation, which requires muscle contraction. The syrinx is the sound-producing vocal organ in birds , located at the base of the trachea . As in the mammalian larynx , the sound is produced by the vibration of air flowing through the organ . The syrinx enables some species of birds to produce extremely complex vocalizations, including mimicking human speech. In some songbirds , the syrinx can produce more than one sound at the same time.

Circulatory system

Birds have a four- chambered heart , which is common to humans , most mammals , and some reptiles ( crocodiles ). This adaptation allows efficient transport of nutrients and oxygen throughout the body , providing birds with the energy to fly and maintain high levels of activity. A Ruby- throated Hummingbird ‘s heart beats up to 1200 times per minute (about 20 beats per second). Arterial blood, which starts from the heart , and venous blood, which returns to it from the tissues , do not mix in circulation.. They have two blood circuits, one pulmonary and another that irrigates the rest of the body .

Digestive system

Many birds have a muscular pouch along the esophagus called the crop or ingluvis. The crop works to soften the feed and to regulate its flow through the system by temporarily storing it. The size and shape of the crop is quite variable among birds . Members of the order Columbiformes , of pigeons , produce a nutritious buch’s milk which they feed to the young by regurgitation. Birds have a ventricle or gizzard, made up of four muscular bands that rotate and grind food, moving it from one area to another within the gizzard. The gizzard of some birds contains small pieces of sand and stone swallowed by the bird .to aid in the grinding process of digestion , serving in the function of teeth in mammals and reptiles . The use of stones in the gizzard is a similarity between birds and dinosaurs , both of which left gizzard stones called gastroliths as a trace fossil.

drinking behavior

There are four general ways that birds drink. Most birds are not capable of swallowing by sucking or peristalsis pumping action in their esophagus (as humans do ), and drink by repetitively raising their heads after filling their mouths to allow the liquid to flow by gravity.

one recognizes the order by a single behavioral characteristic, such as drinking water is pumped up by peristalsis of the esophagus which occurs without exception within the order. The only other group, however, that shows the same behavior, the Pteroclididae, is placed next to the pigeons just because of this undoubtedly very old characteristic.

Other birds, such as nectarivores such as suimangas (Nectariniidae) and hummingbirds ( Trochilidae ), drink using a protractile ribbed tongue , and parrots ( Psittacidae ) lap up the water. Many seabirds have glands near their eyes that allow them to drink seawater. Excess salt is removed from the nostrils. Many desert birds get their water needs entirely from their food . The elimination of nitrogenous wastes in the form of uric acid (uricothelism) reduces the physiological demand for water .

skeletal system

The skeleton of birds is highly adapted for flight. It is extremely light in weight yet strong enough to withstand the stress of take off, flight and landing. A key adaptation is the fusion of bones into a single ossification, such as the pygostyle from the last caudal vertebrae . Because of this, birds typically have fewer bones than other land vertebrates . They also lack teeth or a jaw, and instead they have a beak (zoology), which is much lighter. The beak of many newly hatched birds have an egg tooth, which facilitates their exit from the amniotic egg. Birds have many bones that are hollow with intersecting braces or buttresses to give structural strength.

The number of hollow bones varies between species, although large soaring birds tend to have the greatest number. Respiratory air sacs often form pockets within the semi-hollow bones of the bird skeleton . Some flightless birds like penguins and ostriches have bonessolid only, further evidencing the relationship between flight and the adaptation of hollow bones. Birds also have more cervical ( neck ) vertebrae than many other animals ; most have a highly flexible neck consisting of 13 to 25 vertebrae . Birds are the only vertebrate animals that have fused clavicles (the furcula (birds) or lucky bone ) or a keeled sternum (bird).

The keel of the sternum serves as the attachment site for the muscles used for flight, or similarly those used for swimming by penguins .. Again, flightless birds such as ostriches, which do not have highly developed pectoral muscles, lack a keel on the sternum. It is to be observed that swimming birds have a wide sternum , those that walk have it long or high and, those that fly, have it of almost the same height as width. Birds have uncinate processes above the ribs . These are hooked bony extensions that help strengthen the rib cage by overlapping with the posterior rib. This feature is also found in the reptile tuatara (Sphenodon). They also have a greatly elongated tetraradiate pelvis as in some reptiles . There is extensive fusion of the vertebrae of thetrunk as well as fusion with the pectoral girdle. They have a diapsid skull like in reptiles with prelacrimal fossae (present in some reptiles ). The skull has a single occipital condyle.

skeletal composition

The skull consists of four major bones : frontal (upper head ), parietal (back head ), premaxilla and nasal (upper beak), and mandible (lower beak). The skull of a normal bird usually weighs about 1% of the bird’s total body weight. The vertebral column consists of vertebrae , and is divided into three sections: cervical (13 to 16, in the neck), synsacral (fused vertebrae of the back , also fused to the hips or pelvis), and the pygostyle ( tail ).

The chest consists of the furcula ( lucky bone ) and coracoid (collar bone), which together with the scapula , form the pectoral girdle. The sides of the chest are formed by the ribs , which articulate with the sternum (at the midline of the chest). The shoulder consists of the scapula (shoulder blade), coracoid (mentioned earlier in the chest), and the humerus ( upper arm ). The humerus articulates with the radius and ulna (anterior arm) to form the elbow . The carpus and metacarpus form the “wrist” and “hand” of the bird, and the fingers are used together. the boneson the wing they are extremely light so the bird can fly more easily. The hips consist of the pelvis which includes three major bones : ilium (upper hip), ischium (sides of hip), and pubis (open front of hip ).

These are fused into one (the innominate bone ). The innominate bones are evolutionarily significant in that they allow the bird to lay eggs . They meet at the acetabulum, the socket where the femur , which is the first bone of the hind limb, articulates. At the top of the leg is the femur. At the knee joint , the femurit connects with the tibiotarsus (shin) and the fibula or fibula (lateral bone of the lower leg). The tarsometatarsus forms the lower portion of the leg, and the toes are articulated distally . Birds ‘ leg bones are the heaviest in their bodies, contributing to a low center of gravity. This helps the flight. The skeleton of a bird comprises only about 5% of the body weight.

The feet or legs of birds are classified as anisodactyls, zygodactyls, syndactyls or pamprodactyls.

types of skulls

We can find 3 main types of skull , according to the structure of its bones :

• Schizognathous– the smallest and fully fused vomer; the maxillopalatines never reach the sagittal line of the palate; the palatine and pterygoid bones articulate with the parasphenoid.
• Desmognathus: the vomer is very small and fused; the maxillopalatines reach the midline and are frequently welded; Like the schizognathous skull , the palatines and pterygoids articulate with the parasphenoid.
• Aegitognathus: The vomer is wider than it is long, and is fused at the end. The maxillopalatines are separated.

Types of spikes

Broadly speaking, twelve types of peaks can be distinguished:

• Acute face. It is a hard and very pointed beak . Mainly present in woodpeckers .
• Anseroid: the upper jaw is highly developed and has a kind of nail at the end. The lower jaw is flat. It is found in ducks , geese , and is useful for filtering silt or pulling up grass .
• Aquiline: It is a strong bill that has a sharp hook on the upper jaw that protrudes from the mandible . It is typical of carnivorous birds , such as the falconiformes .
• Conirrostro: it is a short but bulky beak, as well as strong and pointed. It is mainly found in granivorous birds.
• Corvuno: it is a long beak with globular jaws. They are typical of omnivorous birds, such as common ravens ( Corvus corax ).
• Cultirrostro: it is a strong beak, in the shape of a stiletto. Examples: bitterns and little bitterns.
• Dentirrostro: it is a strong, hooked and long beak.
• Scolopaceous: it is a long, fine and flexible beak. It is mainly useful for tracking through muddy or muddy areas. Example: black-tailed needle .
• Phisirrostro: it is a very small beak, although associated with large jaws. They are specially adapted to feed in flight. Example: canastera ( Glareola pratincola ).
• Gallinaceous: it is a strong and short beak, whose end ends in a cone. Example: gallus.
• Laroidal– is a strong hooked beak at the end. Example: Albatross .
• Tenuirrostro: it is a pincer-shaped beak that has fine and balanced jaws. It is common in insectivorous birds.

types of feet

Seven types of feet are generally distinguished :

• Anisodactyl: Finger I is directed caudally.
• Anseroid: the foot has three forward toes joined by a membrane. Finger I is directed backwards.
• Steganopod: the foot has all four toes joined by a membrane.
• Lobed: the fingers have their own independent membranes.
• Pamprodactyl – Allfour toes are pointed forward.
• Syndactyl: The end toe is attached to the middle to the penultimate phalanx.
• Zygodactyl: two fingers are directed forwards and the other two backwards.

muscular system

Most birds have about 175 muscles , primarily controlling the wings , skin , and legs . The largest muscles in the bird are the pectoral muscles, which control the wing and make up about 15-25% of the body weight of a flying bird. These provide the powerful wing beat essential for flight. The muscle ventral (further down) to the pectorals is the supracoracoid. This raises the wing between the downward strides. The supracoracoids together with the pectorals make up about 25 to 35% of the bird’s body weight. skin muscles _ _they help a bird in its flight by adjusting the feathers , which are attached to the skin muscle and help the bird in flight maneuvers. There are only a few other muscles in the trunk and tail , but they are very strong and essential to the bird . The pygostyle controls all movements in the tail and controls the tail feathers . This gives the bird a larger surface area which helps it stay aloft.

bird vision

Birds have sharp vision , raptors have vision eight times sharper than humans , thanks to higher photoreceptor densities in the retina (up to 1,000,000 per square mm in Buteos, compared to 200,000 for humans), a high number of optic nerves , a second set of muscles not found in other animals , and, in some cases, an indented fovea that increases the central part of the visual field. Many species, including hummingbirds and albatrosses , have two foveas in each eye . Many birds can detect polarized light. TheThe eye occupies a considerable part of the skull and is surrounded by a sclerotic eyering, a ring of tiny bones that surrounds the eye . This character is also present in reptiles . The beak of many waders have Herbst’s corpuscles which allow them to detect prey hidden under the sand using minute pressure differences in the water . Birds have a high brain /body mass ratio. This is reflected in the advanced and complex intelligence of birds. The region between the eye and the beak on the sides of the headit’s called lore. This region is sometimes featherless, and the skin may be colored, as in many species of the cormorant family.

Reproductive system

Although most male birds do not have external sex organs , the male has two testicles that become hundreds of times larger during the breeding season to produce sperm . The ovaries of females also grow, although only the left usually works. However, if the left ovary is damaged by infection or other problems, the right ovary will develop trying to replace the left ovary. In males of species without a penis , sperm are stored in the seminal vesicles within the Cloaca (zoology), cloacal bulge before copulation. During copulation, the female moves her tail to the side and the male may mount the female from behind or in front, or moving very close to the female. The cloacae then touch so that the sperm can enter the female’s reproductive tract. This happens very quickly, sometimes in less than half a second. The sperm is stored in the female’s sperm storage tubules for a week or a year, depending on the species. The eggs will then be individually fertilized as they exit the ovary , before being laid by the female. The eggs continue their development outside the female ‘s body . They have albumin (clear) that comes from the glandsfrom the middle of the oviduct, and the shell and its membranes are secreted into glands at the back of the oviduct. Many waterfowl and some other birds, such as the ostrich and the guanajo or turkey, have a penis. When not copulating, it hides inside the proctodeum, which is a compartment inside the cloaca, near the anus.

Scales

Bird scales are made of the same keratin as beaks, nails or claws, and spurs. They are found mainly on the toes and tarsometatarsals, but in some birds they can be found higher up to the ankle (or tibiotarsal-tarsometatarsal joint). Most scales in birds do not overlap significantly, except in the case of kingfishers and woodpeckers . Bird scales are thought to be homologous to those of reptiles and mammals .. The bird embryo begins its development with smooth skin . On the feet , the corneum , or outermost layer of this skin can become keratinized, thickened, and scaled. Scales can be classified into:

1. Cancela – very small scales that are really just a thickening and hardening of the skin, crisscrossed by shallow striae .
2. Reticle – scalessmall but distinct, separate. they are found on the lateral and medial surfaces of the metatarsus of the chicken. These are made from alpha-keratin.
3. Skutela – scalesthat are not as large as scutae, such as those found on the caudal, or posterior, part of the chicken ‘s metatarsus .
4. Scutes – the largest scales, usually on the anterior surface of the metatarsals and the dorsal surface ofthe toes . These are made of beta-keratin like that of reptile scales .

The rows of scutes on the front of the metatarsus may be called an acrometatarsus or acrotarsus. Feathers may intermingle with scales on the feet of some birds . The feathery follicles can be arranged between the scales or even below them, in the dermis , the deepest layer of the skin. In the latter case, the feather may emerge directly through the scale, and be curved in the plane of emergence entirely by the keratin of the scale.

beak development

The beak in birds has a mesodermal embryonic origin, from neural crest cells, which migrate from the neural tube to form part of the facial primordia. The upper beak is derived from the paired maxillary and frontonasal primordia, while the lower beak is derived from the paired mandibular primordium. This has been verified by transplanting neural crest cells between ducks and quails, generating crossed beak morphotypes between the birds to which these cells have been transplanted . Regarding the shape of the beak, it is known that it fulfills diverse ecological functions in the different groups of birds .existing, having a great morphological variety through the families. Currently, thanks to studies on the early development of the beak in bird embryos , it has been possible to determine which expression factors are responsible for regulating the shape of the beak during embryonic development. One of these studies shows that the growth factor. Bone morphogenic protein Bmp4 is closely related to changes in the width and height of the beak, where the greater the expression of Bmp4, the greater the width and length of this organ . On the other hand, this study also shows that the factors Bmp2 and Bmp7 are closely related to the size of the peak (Abzhanov, Protas et al. 2004). Finally, in 2006, through a similar study, it was shown that thecalmodulin “CAM” (a molecule involved in the mediation of Ca2+ signaling) is correlated with the length of the peak, where the greater the expression of this molecule, the greater the elongation of the peak in development.