Gastrointestinal tract

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It usually affects the large intestine but has been known to affect the small intestine as well. You can help by adding to it. Functional morphology of raptor hindlimbs: Capybara, rabbits, hamsters and other related species do not have a complex digestive system as do, for example, ruminants. A kingfisher using its bill to capture prey!


The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. In chemical digestion , enzymes break down food into the small molecules the body can use.

In the human digestive system , food enters the mouth and mechanical digestion of the food starts by the action of mastication chewing , a form of mechanical digestion, and the wetting contact of saliva. Saliva, a liquid secreted by the salivary glands , contains salivary amylase , an enzyme which starts the digestion of starch in the food; the saliva also contains mucus , which lubricates the food, and hydrogen carbonate , which provides the ideal conditions of pH alkaline for amylase to work.

After undergoing mastication and starch digestion, the food will be in the form of a small, round slurry mass called a bolus. It will then travel down the esophagus and into the stomach by the action of peristalsis. Gastric juice in the stomach starts protein digestion. Gastric juice mainly contains hydrochloric acid and pepsin. As these two chemicals may damage the stomach wall, mucus is secreted by the stomach, providing a slimy layer that acts as a shield against the damaging effects of the chemicals.

At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis , which is waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes.

After some time typically 1—2 hours in humans, 4—6 hours in dogs, 3—4 hours in house cats , [ citation needed ] the resulting thick liquid is called chyme. When the pyloric sphincter valve opens, chyme enters the duodenum where it mixes with digestive enzymes from the pancreas and bile juice from the liver and then passes through the small intestine , in which digestion continues. When the chyme is fully digested, it is absorbed into the blood.

Water and minerals are reabsorbed back into the blood in the colon large intestine where the pH is slightly acidic about 5. Some vitamins, such as biotin and vitamin K K 2 MK7 produced by bacteria in the colon are also absorbed into the blood in the colon. Waste material is eliminated from the rectum during defecation. Digestive systems take many forms. There is a fundamental distinction between internal and external digestion.

External digestion developed earlier in evolutionary history, and most fungi still rely on it. Animals have a tube gastrointestinal tract in which internal digestion occurs, which is more efficient because more of the broken down products can be captured, and the internal chemical environment can be more efficiently controlled.

Some organisms, including nearly all spiders , simply secrete biotoxins and digestive chemicals e. In others, once potential nutrients or food is inside the organism , digestion can be conducted to a vesicle or a sac-like structure, through a tube, or through several specialized organs aimed at making the absorption of nutrients more efficient.

Bacteria use several systems to obtain nutrients from other organisms in the environments. In a channel transupport system, several proteins form a contiguous channel traversing the inner and outer membranes of the bacteria. It is a simple system, which consists of only three protein subunits: This secretion system transports various molecules, from ions, drugs, to proteins of various sizes 20 — kDa. The molecules secreted vary in size from the small Escherichia coli peptide colicin V, 10 kDa to the Pseudomonas fluorescens cell adhesion protein LapA of kDa.

A type III secretion system means that a molecular syringe is used through which a bacterium e. One such mechanism was first discovered in Y. The conjugation machinery of some bacteria and archaeal flagella is capable of transporting both DNA and proteins.

It was discovered in Agrobacterium tumefaciens , which uses this system to introduce the Ti plasmid and proteins into the host, which develops the crown gall tumor. The nitrogen fixing Rhizobia are an interesting case, wherein conjugative elements naturally engage in inter- kingdom conjugation.

Such elements as the Agrobacterium Ti or Ri plasmids contain elements that can transfer to plant cells. Transferred genes enter the plant cell nucleus and effectively transform the plant cells into factories for the production of opines , which the bacteria use as carbon and energy sources. Infected plant cells form crown gall or root tumors. The Ti and Ri plasmids are thus endosymbionts of the bacteria, which are in turn endosymbionts or parasites of the infected plant.

The Ti and Ri plasmids are themselves conjugative. Ti and Ri transfer between bacteria uses an independent system the tra , or transfer, operon from that for inter-kingdom transfer the vir , or virulence , operon. Such transfer creates virulent strains from previously avirulent Agrobacteria. In addition to the use of the multiprotein complexes listed above, Gram-negative bacteria possess another method for release of material: Vesicles from a number of bacterial species have been found to contain virulence factors, some have immunomodulatory effects, and some can directly adhere to and intoxicate host cells.

While release of vesicles has been demonstrated as a general response to stress conditions, the process of loading cargo proteins seems to be selective.

The gastrovascular cavity functions as a stomach in both digestion and the distribution of nutrients to all parts of the body. Extracellular digestion takes place within this central cavity, which is lined with the gastrodermis, the internal layer of epithelium. This cavity has only one opening to the outside that functions as both a mouth and an anus: In a plant such as the Venus Flytrap that can make its own food through photosynthesis, it does not eat and digest its prey for the traditional objectives of harvesting energy and carbon, but mines prey primarily for essential nutrients nitrogen and phosphorus in particular that are in short supply in its boggy, acidic habitat.

A phagosome is a vacuole formed around a particle absorbed by phagocytosis. The vacuole is formed by the fusion of the cell membrane around the particle. A phagosome is a cellular compartment in which pathogenic microorganisms can be killed and digested. Phagosomes fuse with lysosomes in their maturation process, forming phagolysosomes.

In humans, Entamoeba histolytica can phagocytose red blood cells. To aid in the digestion of their food animals evolved organs such as beaks, tongues , teeth, a crop, gizzard, and others. Birds have bony beaks that are specialised according to the bird's ecological niche. For example, macaws primarily eat seeds, nuts, and fruit, using their impressive beaks to open even the toughest seed. First they scratch a thin line with the sharp point of the beak, then they shear the seed open with the sides of the beak.

The mouth of the squid is equipped with a sharp horny beak mainly made of cross-linked proteins. It is used to kill and tear prey into manageable pieces. The beak is very robust, but does not contain any minerals, unlike the teeth and jaws of many other organisms, including marine species.

The tongue is skeletal muscle on the floor of the mouth that manipulates food for chewing mastication and swallowing deglutition. It is sensitive and kept moist by saliva. The underside of the tongue is covered with a smooth mucous membrane. The tongue also has a touch sense for locating and positioning food particles that require further chewing. The tongue is utilized to roll food particles into a bolus before being transported down the esophagus through peristalsis.

The sublingual region underneath the front of the tongue is a location where the oral mucosa is very thin, and underlain by a plexus of veins. This is an ideal location for introducing certain medications to the body.

The sublingual route takes advantage of the highly vascular quality of the oral cavity, and allows for the speedy application of medication into the cardiovascular system, bypassing the gastrointestinal tract.

Teeth singular tooth are small whitish structures found in the jaws or mouths of many vertebrates that are used to tear, scrape, milk and chew food. Teeth are not made of bone, but rather of tissues of varying density and hardness, such as enamel, dentine and cementum. Human teeth have a blood and nerve supply which enables proprioception. This is the ability of sensation when chewing, for example if we were to bite into something too hard for our teeth, such as a chipped plate mixed in food, our teeth send a message to our brain and we realise that it cannot be chewed, so we stop trying.

The shapes, sizes and numbers of types of animals' teeth are related to their diets. For example, herbivores have a number of molars which are used to grind plant matter, which is difficult to digest. Carnivores have canine teeth which are used to kill and tear meat. A crop , or croup, is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion.

In some birds it is an expanded, muscular pouch near the gullet or throat. In adult doves and pigeons, the crop can produce crop milk to feed newly hatched birds. Certain insects may have a crop or enlarged esophagus. Herbivores have evolved cecums or an abomasum in the case of ruminants. Ruminants have a fore-stomach with four chambers. These are the rumen , reticulum , omasum , and abomasum.

In the first two chambers, the rumen and the reticulum, the food is mixed with saliva and separates into layers of solid and liquid material. Solids clump together to form the cud or bolus. The cud is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size.

Fibre, especially cellulose and hemi-cellulose , is primarily broken down into the volatile fatty acids , acetic acid , propionic acid and butyric acid in these chambers the reticulo-rumen by microbes: In the omasum, water and many of the inorganic mineral elements are absorbed into the blood stream.

The abomasum is the fourth and final stomach compartment in ruminants. It is a close equivalent of a monogastric stomach e. It serves primarily as a site for acid hydrolysis of microbial and dietary protein, preparing these protein sources for further digestion and absorption in the small intestine. Digesta is finally moved into the small intestine, where the digestion and absorption of nutrients occurs. Microbes produced in the reticulo-rumen are also digested in the small intestine.

Regurgitation has been mentioned above under abomasum and crop, referring to crop milk, a secretion from the lining of the crop of pigeons and doves with which the parents feed their young by regurgitation. Many sharks have the ability to turn their stomachs inside out and evert it out of their mouths in order to get rid of unwanted contents perhaps developed as a way to reduce exposure to toxins.

Other animals, such as rabbits and rodents , practise coprophagia behaviours — eating specialised faeces in order to re-digest food, especially in the case of roughage.

Capybara, rabbits, hamsters and other related species do not have a complex digestive system as do, for example, ruminants. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft faecal pellets of partially digested food are excreted and generally consumed immediately. They also produce normal droppings, which are not eaten. Young elephants, pandas, koalas, and hippos eat the faeces of their mother, probably to obtain the bacteria required to properly digest vegetation.

When they are born, their intestines do not contain these bacteria they are completely sterile. Without them, they would be unable to get any nutritional value from many plant components.

An earthworm 's digestive system consists of a mouth , pharynx , esophagus , crop , gizzard , and intestine. The mouth is surrounded by strong lips, which act like a hand to grab pieces of dead grass, leaves, and weeds, with bits of soil to help chew. The lips break the food down into smaller pieces.

In the pharynx, the food is lubricated by mucus secretions for easier passage. The esophagus adds calcium carbonate to neutralize the acids formed by food matter decay. Temporary storage occurs in the crop where food and calcium carbonate are mixed. The powerful muscles of the gizzard churn and mix the mass of food and dirt. When the churning is complete, the glands in the walls of the gizzard add enzymes to the thick paste, which helps chemically breakdown the organic matter.

By peristalsis , the mixture is sent to the intestine where friendly bacteria continue chemical breakdown. This releases carbohydrates, protein, fat, and various vitamins and minerals for absorption into the body. The neighboring portion of the surrounding tendon sheath contains a series of transversely running plicae folds that often have a proximal slant i.

When the flexor tendons are pulled taut, and the digits flexed, the tubercle pad moves proximally over the stationary plicae on the sheath.

When resistance to digital flexion is met, the locking elements intermesh and engage and the friction produced prevents slippage of the tendons. This permits digital flexion to be maintained with little or no muscular involvement E inoder and Richardson Action of the avian digital TLM: This shows the movement of the talon a , flexor e and extensor d tendons, ungual phalanx b , and the movement of the ventrally located tubercle pad f relative to the stationary plicated sheath g and phalangeal bone c From: Einoder and Richardson Each raptor has a unique force production, along with a different time of activity, that would allow for a degree of prey specialization.

Great Horned Owl foot. B Great Horned Owl. The relation between rate of success and direction of movement for a food item that was pulled forward a , backward b and sideways c. Direction of prey progression — dotted arrow 1 , direction of owl flight — dashed arrow 2 , and direction to which the owl had to move its head or trunk — solid arrow 3. Owl picture from Knudsen Movement and direction of prey affect raptor success rate -- Shifferman and Eilam tested a novel idea, that rather than maximizing their distance from a predator during close-distance encounters, prey species are better off moving directly or diagonally toward the predator in order to increase the relative speed and confine the attack to a single available clashing point.

They used two tamed Barn Owls Tyto alba to measure the rate of attack success in relation to the direction of prey movement. A dead mouse or chick was used to simulate the prey, pulled to various directions by means of a transparent string during the owl's attack.

This failure to catch prey that move sideways may reflect constraints in postural head movements in aerial raptors that cannot move the eyes but rather move the entire head in tracking prey. So far there is no evidence that defensive behavior in terrestrial prey species takes advantage of the above escape directions to lower rates of predator success. However, birds seem to adjust their defensive tactics in the vertical domain by taking-off at a steep angle, thus moving diagonally toward the direction of an approaching aerial predator.

These preliminary findings warrant further studies in Barn Owls and other predators, in both field and laboratory settings, to uncover fine predator head movements during hunting, the corresponding defensive behavior of the prey, and the adaptive significance of these behaviors.

Barred Owl primary - leading edge below and trailing edge above. The silent flight of owls -- Noise is generated by vortices produced when air flows over a bird's wing and larger vortices produce more noise.

Wings with small saw-toothed projections vortex generators , like those on the leading edge of owl wings, generate many small vortices instead of large vortices and produces less aerodynamic noise. In addition, the fringe feathers at the trailing edge of the wing with fewer hooklets at the ends of the barbs help to break up the sound waves that are generated as air flows over the top of their wings and forms downstream wakes, and the soft down feathers located elsewhere on the wings and legs of owls absorb the remaining sound frequencies above 2, hertz and make owls completely silent to their prey.

As a bonus, with high angles of attack and at slow speeds, vortex generators stick out of the stagnant air near the surface of the wing, and into the freely moving air outside the boundary layer. This surface layer is typically quite thin, but dramatically reduces speed of the airflow towards the rear of the wing.

The vortex generators mix the free stream with the stagnant air to get it moving again, providing considerably more airflow at the rear of the wing and helping to prevent stalling. This process is referred to as 're-energizing the boundary layer. Unpredictable predators -- The use of space by predators in relation to their prey is a poorly understood aspect of predator-prey interactions.

Classic theory suggests that predators should focus their efforts on areas of abundant prey, that is, prey hotspots, whereas game-theoretical models of predator and prey movement suggest that the distribution of predators should match that of their prey's resources. If, however, prey are spatially anchored to one location and these prey have particularly strong antipredator responses that make them difficult to capture with frequent attacks, then predators may be forced to adopt alternative movement strategies to hunt behaviorally responsive prey.

Roth and Lima examined the movement patterns of bird-eating Sharp-shinned Hawks Accipiter striatus in an attempt to shed light on hotspot use by predators. Their results suggest that these hawks do not focus on prey hotspots such as bird feeders but instead maintain much spatial and temporal unpredictability in their movements.

Hawks seldom revisited the same area, and the few frequently used areas were revisited in a manner consistent with unpredictable returns, giving prey little additional information about risk.

But why wouldn't Sharp-shinned Hawks focus their hunting on the areas with the most potential prey bird feeders? One possibility is that behaviorally responsive prey diminish the "hotspot" quality of feeders. Although feeder hotspots are sources of abundant prey, the individuals at such feeders generally benefit from group vigilance as a result of these higher densities. As a result, the vulnerability of the prey may actually be lower at feeders than at other locations.

In addition, unpredictable movement may reflect a sort of "prey management" by predators, whereby predators spread their hunting activity over multiple areas in an effort to avoid inflating the antipredator behavior of their prey.

This hunting strategy may be effective when prey are anchored to high-resource areas such as feeders and use antipredator behaviors, such as high vigilance, that reduce a predator's attack success if it attacks frequently and predictably. Seabirds are choking on ocean plastic video. The tongues of cormorants and other fish-eating species are small because these species swallow prey whole and tongues are not needed to manipulate or position food in the oral cavity. Dorsal view of the surface of the lower bill of a Great Cormorant Phalacrocorax carbo.

Arrow shows the tongue with sharpened tip. Scale bar, 12 mm. Lateral view of the cormorant tongue. The tongue and the small anterior and posterior areas of the mucosa of the bill are covered by white keratinized epithelium. Black arrow shows short base of the tongue. White arrow shows the median crest on the dorsal surface of the tongue. A, anterior; B, posterior. Scale bar, 3 mm Source: Detailed view of the horny tip left of the Guadeloupe Woodpecker tongue in vivo position Villard and Cuisin Dorsal view of the tongue of the Spotted Nutcracker Nucifraga caryocatactes.

Arrows show two elongated processes of the apex. A, apex, B, body, R, root, LP, laryngeal prominence. Scale bar, 3 mm. Lateral view of the tongue of the nutcracker. Arrow shows elongated processes, pointed diagonally, B, body, R, root. Hummingbird tongues are fluid traps, not capillary tubes -- Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics.

Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes.

Rico-Guevara and Rubega found that hummingbird tongues do not function like a pair of tiny, static tubes drawing up floral nectar via capillary action.

Instead, the tongue tip is a dynamic liquid-trapping device that dynamically traps nectar by rapidly changing their shape during feeding. In addition, the tongue—fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap.

These results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Hummingbird tongue tips twist to trap nectar. How the hummingbird tongue really works with videos. Close encounters with possible prey. You want to live 10—20 years. You are peering under leaves, poking into rolled ones, searching around stems, exploring bark crevices and other insect hiding places.

Abruptly an eye appears, 1—5 cm from your bill. The eye or a portion of it is half seen, obstructed, shadowed, partly out of focus, more or less round, multicolored, and perhaps moving. Now, a safe few meters away, are you going to go back to see whether that was food? Associated body patterns often suggest other head and facial features, which in turn enhance the eye-like nature of the spots. None of these patterns exactly matches the eyes or face of any particular species of predator; but, even when quickly and partially glimpsed, all give the illusion of an eye or face.

These false eyes are mimicking the eyes and faces of such predators of insect-eating birds as snakes, lizards, other birds, and small mammals, as perceived at close range by the insectivorous birds in their natural world.

Note the distended throat of this American Kestrel. Pigeons generally lay two eggs one day apart, which hatch 18 days after they are laid. A similar substance is produced by flamingos and male Emperor Penguins. The normal function of the crop is food storage. Pigeon 'milk' also contains IgA antibodies and antioxidants carotenoids. The avian stomach is divided into 2 parts:. Photomicrograph 50X of a cross section through the proventriculus showing folds of mucous membrane P ; deep proventricular glands GP ; capsule connective tissue around the glands arrow head ; muscle layer m ; serosa connective tissue with blood vessels S , and the lumen L From: Photomicrograph X of longitudinal section of the gizzard showing folds of mucous membrane lined by simple prismatic epithelium P ; simple tubular glands Gs in the lamina propria constituted by connective tissue Lp ; secretion of glands S that are continuous with the cuticle or koilin ; C , part of muscle layer m , interpersed with bundles of connective tissue Tc From: Photomicrograph X of the koilin of an Eclectus Parrot Eclectus roratus.

Note the regular, columnated structure of the koilin layer K and its association with the glandular epithelium E of the ventriculus From: De Voe et al. A, koilin, B, crypts, C, glands that secrete koilin, D, epithelial surface, E, desquamated epithelial cells, 2 Mucosa of the gizzard.

A, koilin, B, secretion in gland lumens and crypts, and 3 Koilin layer. A, secretion column, B, koilin-layer surface, C, horizontal stripe indicating a 'pause' in secretion of the koilin, D, cellular debris. Eglitis and Knouff Vultures of the seas -- Animals are primarily limited by their capacity to acquire food, yet digestive performance also conditions energy acquisition, and ultimately fitness. Optimal foraging theory predicts that organisms feeding on patchy resources should maximize their food loads within each patch, and should digest these loads quickly to minimize travelling costs between food patches.

GPS-tracking of 40 Wandering Albatrosses from the Crozet archipelago during the incubation phase confirmed foraging movements of between — km, giving the birds access to a variety of prey, including fishery wastes. Using miniaturized, autonomous data recorders placed in the stomach of three birds, the first-ever measurements of gastric pH and temperature in procellariformes were obtained.

Such low stomach pH gives Wandering Albatrosses a strategic advantage because it allows a rapid chemical breakdown of ingested food and rapid digestion. This is useful for feeding on patchy, natural prey, but also on fishery wastes, which might be an important additional food resource for Wandering Albatrosses.

It is likely that this physiological characteristic evolved as a response to a diet largely composed of squid, and to a patchy distribution of this food resource resulting in large, infrequent meals.

The strategy of Wandering Albatrosses is to cover long distances rapidly and at low costs to increase the probability of encountering dispersed prey patches whose distribution is unpredictable.

Knots with large gizzards consumed far more molluscs with shells than the birds with smaller gizzards. Birds with smaller gizzards simply couldn't feed fast enough. By allowing them to crush more shell per gizzard-full, larger gizzards gave birds the edge. Thus, even though it is energetically costly for the knots to maintain a larger gizzard, when the bird needs to get the most out of its crunchy diet, it's a price worth paying. So, the birds' gizzards enlarge as they fatten for migration.

Because the molluscs' shells stay the same size as the molluscs shrink, the amount of shell a bird must process to eat its fill also increases. But with their larger gizzards, the birds can still make the most of even the crunchiest winter diet! Within 14 days, they showed a doubling of the size of their gizzards. Red Knots have strong muscular gizzards for feeding on molluscs. A shift back to a mussel diet induced about a doubling in gizzard mass in just a few days.

As the knots were fed progessively smaller mussels day 22 to day 46 that are easier to crush, gizzard mass again declined. A switch back to a soft food pellet diet caused a further decline in gizzard mass.

Finally, a switch back to a mussel diet again cause a rapid increase in gizzard mass From: Piersma and Drent Ostrich Struthio camelus stomach.

Note how particle size of material in the gizzard ventriculus is smaller than in the proventriculus due to the grinding action of the muscular walls plus small pebbles gastroliths. The capacity to reduce particle size is related to the metabolic demands of a species. Therefore, particle size reduction is often considered the key digestive difference between ecto- and endotherms that allows endotherms to rely on shorter digesta retention times without losing digestive efficiency, and hence facilitate the high level of food intake necessary to meet their increased metabolic requirements.

In contrast, adaptations for chewing intrinsically increase the weight of the head. The use of the gizzard system has the potential advantages that intake rate is not limited by chewing, that no investment in dental tissue is necessary, and that dental wear is not a determinant of senescence as observed in mammals.

The absence of age-dependent tooth wear might even be a contributing factor to the slower onset of senescence in birds as compared to mammals. On the other hand, the use of a gizzard requires the intake of suitable grit or stones—an action that represents, in the few studies where this has actually been quantified in birds, a relevant proportion of feeding time Fritz et al.

Gastrointestinal tracts of a carnivorous hawk, an omnivorous chicken, and 4 herbivorous birds. Note larger size of crop in omnivore and herbivores, and particularly in hoatzin. Ceca are small in hawks and relatively large in grouse. Although ceca are relatively small in Hoatzins , Emus, and Ostriches, an expanded foregut Hoatzins , a much longer midgut Emus , or a much longer colon Ostriches compensates for this From: Stevens and Hume Over-reliance on the passive pathway provides metabolic advantages and ecological constraints.

It does provide birds with an absorptive process that can deal with rapid and large changes in intestinal sugar concentrations. The passive pathway is also energetically inexpensive to maintain and modulate. However, passive absorption through the paracellular pathway is dependent on concentration gradients. In the absence of a transport system that selects which materials to absorb, this non-discriminatory pathway may also increase vulnerability to toxins, and thus constrain foraging behavior and limit the breadth of the dietary niche of the birds.

Another problem is that when luminal sugar concentrations are lower than those in plasma, glucose may diffuse back into the lumen. Cross-section of the intestine ileum of a Spotted Tinamou Nothura maculosa.

Villi are lined with columnar epithelium EP , including goblet cells arrows that secrete mucus. The muscle layer includes longitudinal fibers MI on the perimeter, circular fibers Mc , and additional longitudinal fibers at the base of the villi muscularis muscosae; MM From: Chikilian and de Speroni Blue-headed Parrots at clay lick.

Meyer-Rochow and Gal determined that the pressures involved could be approximated if they knew the 1 distance the feces traveled, 2 density and viscosity of the material, and 3 shape, aperture, and height of the anus above ground.

How penguins choose the direction of defecation, and how wind direction factors into that decision, remain unknown. Avian Pancreas tissue Source: The Avian Digestive Tract. Avian geophagy and soil characteristics in southeastern Peru.

Luminal morphology of the avian lower intestine: Histological aspects of the stomach proventriculus and gizzard of the Red-capped Cardinal Paroaria gularis gularis. Comparative study of the digestive system of three species of tinamou. Crypturellus tataupa, Nothoprocta cinerascens , and Nothura maculosa Aves: Journal of Morphology Journal of Experimental Zoology Rictal bristle function in Willow Flycatcher. Dysplastic koilin causing proventricular obstruction in an Eclectus Parrot Eclectus roratus.

Journal of Avian Medicine and Surgery Anatomy and physiology of the digestive system in fowl. Pages in Proc. An histological and histochemical analysis of the inner lining and glandular epithelium of the chicken gizzard.

American Journal of Anatomy An ecomorphological study of the raptorial digital tendon locking mechanism. Dietary and developmental regulation of intestinal sugar transport. Digesta retention patterns in geese Anser anser and turkeys Meleagris gallopavo and deduced function of avian caeca.

Comparative Biochemistry and Physiology A Histological and global gene expression analysis of the 'lactating' pigeon crop. Vultures of the seas: Evolution of the structure and function of the vertebrate tongue.

Journal of Anatomy Light and scanning electron microscopic study of the tongue in the cormorant Phalacrocorax carbo Phalacrocoracidae, Aves. Functional morphology of the tongue in the nutcracker Nucifraga caryocatactes. A tropical horde of counterfeit predator eyes. Instructed learning in the auditory localization pathway of the Barn Owl.

The morphology of the bill apparatus in the Steller's Sea Eagle. Wild Bird Society of Japan, Tokyo. Use of dung as a tool by burrowing owls.

The integration of energy and nitrogen balance in the hummingbird Sephanoides sephaniodes. Does gut function limit hummingbird food intake?

Physiological and Biochemical Zoology Pressures produced when penguins pooh—calculations on avian defaecation. Scare tactics in a neotropical warbler: Gliding flight and soaring. Theoretical Ecology Series, vol. Modelling the flying bird C. Structure, form, and function of flight in engineering and the living world.

Phenotypic flexibility and the evolution of organismal design. Trends in Ecology and Evolution The hummingbird tongue is a fluid trap, not a capillary tube. Between air and water: Use of prey hotspots by an avian predator: Structure and mechanical behavior of a toucan beak.

Movement and direction of movement of a simulated prey affect the success rate in Barn Owl Tyto alba attack. Musculoskeletal underpinnings to differences in killing behavior between North American accipiters Falconiformes: Accipitridae and falcons Falconidae. Journal of Morphology, online early. Le Bohec, and Y. Adjustments of gastric pH, motility and temperature during long-term preservation of stomach contents in free-ranging incubating King Penguins. Journal of Experimental Biology A tough nut to crack.

Adaptations to seed cracking in finches. Cost-benefit analysis of mollusc-eating in a shorebird. Optimizing gizzard size in the face of seasonal demands. How do woodpeckers extract grubs with their tongues?

Why do woodpeckers resist head impact injury: Functional morphology of raptor hindlimbs: The turning- and linear-maneuvering performance of birds: Canadian Journal of Zoology Hummingbird jaw bends to aid insect capture. A mechanical analysis of woodpecker drumming and its application to shock-absorbing systems.

I - Introduction to Birds. VII - Circulatory System.