Chapter 19 Avian anatomy & physiology
Describe the shape & general characteristics of avian eyes
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Describe the unique anatomical features that affect the sense of hearing in nocturnal owls
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List & describe the four classifications of newly hatched chicks
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List & describe the unique features of the avian female reproductive system
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List & describe the unique features of the avian male reproductive system
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describe the composition of avian urine
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describe the functions of each component of the avian digestive system
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explain how the characteristics of avian eyes affect visual
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list the components of the avian digestive system
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list the unique anatomical features that affect the sense of taste in birds
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function of the Avian air sacs
1. They act as reservoirs for air & provide warmth & moisture to facilitate the diffusion of air through the lungs. 2. They help in thermoregulation, cooling the body by the the internal evaporation of water. 3. They help provide buoyancy to water birds. Many species of penguin & diving birds have large posterior & abdominal air sacs, the volume of which can be adjusted during diving & floating.
Describe the molting process and feather growth
> Feather develop from the papillae in the dermis layer of the skin, these papillae are located in the feather tracts & contain germ cells with the genetic information that dictates the type, size, & color of feathers. These cells are " activated" by physiological & environmental factors. Increasing day length stimulates the pituitary & thyroid glands to produce hormones that stimulate molting, & sex hormones also may play a concurrent role > Molting begins when a newly developing feather pushes an old one out. It then emerges from the skin & is covered by an epidermal covering called the PERISERM. As a bird begins to preen a growing feather, it gently removes the periderm, which can be seen as small, white flakes in the plumage. Blood vessels from the dermis reach into the new feather to provide nourishment. When a feather is fully grown, the blood dries up, & the rachis is pinched closed under the skin. During feather development, a growing feather is called a BLOOD FEATHER. Bloodcan be seen in the proximal part of the feather shaft during the entire growth phase. Injury ro a blood feather not only results in bleeding but can prevent a feather from developing normally until molted again.
Skeleton
> Two major sections of the Avian skeletal components are : AXIAL SKELETON & APPENDICULAR SKELETON. The bones that provide the general framework of the avian body includes: SKULL, VERTEBRAL COLUMN, & STERNUM called the AXIAL SKELETON. > The WINGS, SHOULDER BONES, LEGS, & PELVIC BONES support locomotion & are called APPENDICULAR SKELETON
Electrocardiogram (avian)
A bird's heart chamber contracts & relax, the resulting changes in electoral voltage can be detected by placing electrodes in strategic locations on the wings & legs. The voltage changes are converted into visual peaks & valleys with help of an electrocardiograph (ECG) machine. The ECG consists of a P,QRS, &T wave that correspond to the following muscular activities: P wave = contraction & relaxation of the atria QRS wave complex = contraction of the ventricles T wave= relaxation of the ventricles In birds, the existence of the Q wave is in question. In many species, such as chickens & turkeys, it is believed to be completely absent, but in other species, such as some ducks, it appears to be prominent. The time intervals represented in the ECG are relatively fixed, with the exception of the T to P interval, which changes based on changes in the heart rate. The ECG is an important tool to monitor a patient's stability during anesthesia & to diagnose malfunctions of the heart & major vessels.
Diagnosing a shoulder girdle fracture (clinical application)
A cockatiel (Nymphicus hollandicus) was presented to the clinic after it flew into a kitchen window. The problem now is that the bird can only fly short distances. It has full extension of it wings, but it also has a slight wing droop on its left side at rest. Its flight feathers are intact, & it has a adequate amount of muscle on its keel. Palpation of the wings reveal no bruising or fractures. Now What? > A radiograph is next logical next step. Often birds have head-on collisions, they fracture one or more of the bones in their shoulder girdle, which allows only short distance flight. Wing extension is normal: however, a slight wing droop often occurs, & blood is often found in the back of the mouth. Extremely displaced bone ends may require surgical repair to prevent a bone end from penetrating the heart, but most often, immobilizing the wing on the injured side for 2 to 3 weeks, followed by another week of cage rest, allows the bone to heal adequately
blood feathers
A developing feather that contains blood in its shaft for growth & nourishment
Describe the anatomical structures of avian claws
A horny sheath derived from specialized scales at the end of each toe. Like beaks, they also grow continuously. Species differ in the type of claws they posses, based on their perching habits & methods of procuring food. Ex., ground feeders (chickens & pheasants) have short, sharp claws that are used to scratch the ground; birds of prey have claws -TALONS that are long, sharp, & rounded to catch & kill their prey. Vultures ( scavengers) have short, blunt claws; & climbing birds (woodpeckers & nuthatches) have strongly curved claws for gripping
fault bar
Area of the feather vane that lack barbules, also called a STRESS BAR; caused by an interruption of the feathers blood supply during development
nape
Back of neck
List the unique feature of the avian respiratory system
Because of the fast metabolism & high energy level of birds, the delivery of O2 & removal of CO2 from the body tissues must be quick & efficient. Birds possess a respiratory system with highly specialized components. Anatomy ♦ORAL CAVITY - contains several structures involved in respiration. The GLOTTIS is the opening of the trachea, which is located at the back of the tongue. Air is directed to the glottis via the mouth & nasal chambers. They are linked via the CHOANAE, which are two internal nares that open from the nasal chambers into the roof of the mouth. The LARYNX, a cartilaginous structure surrounding the glottis, has ligaments & muscle attachments that enable it to act as a valve to prevent solids & liquids from entering the trachea & lungs. It does not function in the production of sound as in mammals. ♦TRACHEA - Consists of cartilaginous rings that are held together by bands of fibrous CT. In a few species, such as swans & whooping cranes (Gus Americana), the trachea is very long & coiled. For species that migrate at high altitude, the long trachea helps provide moisture to the inhaled air & aids in the of production sound ♦ SPRINX - is the enlargement of the trachea above the sternum. It is essentially the voice box of birds & contains MUSCLES, AIR SACS & VIBRATING MEMBRANES. To create sound, air from the lungs & air sacs is forced over the membranes during expiration, causing changes in muscle tension & air pressure. These changes cause vibrations of the membranes. The complexity of a bird's vocalizations depends on the # of muscles present. Birds capable of complex vocalizations, such as many species of songbirds, have an average of seven pairs , whereas, on the other end of the spectrum, storks, vultures, & ostriches do not have any. Parrots fall in the middle, with three pairs of muscles in their syrinx. ♦ BRONCHI - Is the two branches of the trachea bifurcates located at the level of the sternum . These branches pass through the ventral side of each lung & end in the posterior air sacs. Once they enter the lung, the bronchi lose their reinforcing cartilaginous rings & are called MESOBRANCHI. The mesobronchi give rise to four to six VENTROBRONCHI. The ventrobronchi are connected to air capillaries, where gas exchanges occurs. ♦PARABRONCHI- These are, parallel tubes originate from the ventrobronchi in the lungs & are connected tot he tiny openings of air capillaries. The air capillaries, in turn, are surrounded by small blood capillaries. Gas exchange occurs between these two groups of capillaries. ♦AIR SACS - are thin-walled, lightly vascularized, transparent membranes that make up about 80% of the total of the total volume of the respiratory system. There are nine air sacs, four of which are paired. The pairs include: CRANIAL THORACIC, CAUDAL THORACIC, CERVICAL, & ABDOMINAL AIR SACS. which are located in the thoracic inlet between the clavicles. Air sacs are connected to the primary bronchi ( abdominal sacs) or ventrobronchi ( cervical, cranial thoracic, caudal thoracic, & interclavicular sacs). Diverticula of some of the air sacs penetrate the skeleton. In many species, the interclavicular sac extends into the humerus bones, sternum, syrinx, & pectoral girdle. The abdominal sacs often extend into the legs & pelvic girdle
Blood & types
Blood is made up of several components & functions to carry nutrients, O2, & hormones to cells; to carry metabolic wastes from cells to the lungs & kidneys; to control & prevent disease; & to regulate a bird's body temperature. Blood consists of RBCs, WBCs, platelets & plasma. >Erythrocytes - (RBCs are oval, nucleated, & larger than those of mammals. In most species, they are formed in the bone marrow of adult birds, but in passerines ( song birds), they are formed in the spleen & liver. The RBC possess hemoglobin for carrying O2 to the tissues. The total # of RBCs is dependent on several factors, including age, sex, diet, & time of year. In general, the percentage of RBCs to total blood volume in a healthy adult bird should fall between 35% & 55% >Leukocytes - WBCs are important in helping fight disease. In adult birds, WBCs are primarily produced by the spleen. In young birds, they are primarily produced by the liver, kidneys, pancreas, & the BURSA OF FABRICIUS which is located on the dorsal wall of the proctodeum in the cloaca .
Sites of venipuncture (clinical application)
Blood samples are taken for a variety of diagnostic purposes. In birds, blood can be drawn most easily from one of three vessels: AJUGUALR VEIN, BRACHIAL VEIN, or a MEDIAL METATARSAL VEIN. The jugular veins are located ventrally, on each side of the trachea. The right jugular is larger than the left & is most commonly used for venipuncture in psittacines (parrots). The brachial vein is located on the ventral side of the wing, extending over the elbow & up the humerus. About halfway up the humerus, it joins the cutaneous ulnar vein & increases slightly in size. In raptors, the brachial vein is often used to take blood sample or insert temporary catheters for repeated intravenous treatments. The medial metatarsal vein is located on the ventral over the heel joint. Blood samples are sometimes taken from this site for raptors, but it is most commonly used for waterfowl species.
Feet
Bottom of bird's foot is - METATARSAL PAD. It surrounded by two, three, or four toes, with the majority of species possessing four. Often one toe faces the rear & the other three face forward - ANISODACTYL. In some species, the 2nd & 3rd toes face forward, & the 1st & 4th toe is opposable & can face either forward or backward. > The digits are referred to by a #ing system based on the # of joints they have. The rear toe #1 & has one joint, where it hinges to the metatarsal pad. Digit #2 is the innermost, medial digit & possesses two joints. The middle toe is digit #3; it has three joints. The outer, lateral toe has four joints & is digit #4.
Molting
DEF: Process of feather replacement; occurs one to several times a year, depending on the species >Occurs in a species-specific pattern that allows a bird to continue normal activities. In most species, feathers replacement is symmetrical; one or two pairs of flight feathers are molted at a time so that a bird still can fly adequately. One or more exception is found in many species of waterfowl, which molt their flight feathers all at once after breeding season. They are flightless during this time but can forage by grazing on land or in the water. > between 4% & 12% of a bird's body weight is made up of feathers (Pettingill, 1972). It takes a lot of energy to replace feathers during molting, it usually occurs in North America species after breeding season & the beginning of migration, usually when food supply is abundant.
Pterylae
DEF: seven tracts of skin where feathers originate Caudal -(head, side of head) Humeral (top of wing) ALAR (along bottom of wing) Spinal - ( along spinal cord, back) Femoral -(top of leg) Crural - (mid legs, below femoral) Caudral - (tail)
topography
DEF: the distribution of parts or features on the surface of or within an organ or organism > avian external features Upper mandible (top of beak) lower mandible (bottom, jaw of break) Cere (between nostrils, connects to beak) Nostril - (nares) Crown -(Cranial area) Nape - (below crown, neck area) Wrist - (top of wing) Auricular feathers - (below eyes) Crop area (Below the lower mandible) Abdomen vent - (anal area) Digit # 2 (inside), Digit #3(outside), Claw - (middle digit)
Apteryia
DEF; Bare areas of skin of birds where feathers do not originate >However, the feathers in these tracts overlap one another to create the fully feathered look
periderm
Epidermal covering of a new feather after it emerges from the skin
Mutes: A diagnostic tool (clinical application)
Evaluation of a bird's mutes is an important diagnostic tool in assessing overall health. In many species the mutes normally have a dark fecal center surrounded by a white ring of urates. However, the color & consistency of a bird's mutes can be altered by diet, parasites, or disease, & any change in an individual bird's normal excreta should be investigated to discover the cause. [ex., parrots fed a fruity, pelleted diet often have a variety of colors to their mutes, & hawks fed day-old cockerels will have gold fecal centers in their mutes instead of dark ones]. These are normal changes & can be explained by diet. . Birds suffering from the actions of some intestinal parasites, such as coccida, often have a tinge of green in their output, & sometimes blood. Obtaining a complete patient history is important in evaluating these clinical observations. This is easy in the case of pet birds; however, for wild birds with unknown histories, extensive laboratory testing may be necessary to explain abnormal output from the digestive &urinary systems. Tests performed often from the digestive & urinary systems. Tests performed often include fecal analysis for parasites, fecal Gram stain for bacteria, a complete blood count, a chemistry profile to assess organ function, & blood lead levels in species highly vulnerable to lead poisoning, such as bald eagles (Habliaeetus leucocephalus) & golden eagles ( Aquila chrysaetos)
Feather damage
External parasites - feather mites can chew & consume parts of the feather vanes, creating weak points. Damage can occur from daily wear & tear. often, lighter tips of a bird's flight & tail feathers are worn off by the roughness of daily activities, giving the feathers a more iridescent appearance. Ex., mallard ducks ( Anas platyrhynchos) & European starlings (Sturnus vulgaris), noticeable in the spring, when males of many species lost their flight feathers tips & look more colorful before the breeding season. > another cause occurs during a feather's growth phase. If a feather is stressed during its growth, even for a few hours, there is an interruption in the blood flow. What develops is called a FAULT BAR, or stress, which is characterized by a weakness area on the feather vane, where the barbs lack barbules. When stress is removed , the blood flow returns & normal development continues. > Stressors - most common is poor diet, insufficient food supply or a food supply deficient in essential nutrients often creates fault bars on developing feathers. Can have a severe effect on nestling birds, because flight feathers grow in at the same time. Any stressor that temporarily deletes blood supply to these feathers create fault bars on all of them
Describe the structure & functions of feathers
Features are overgrowths of skin that are made of protein; once completely developed, they are nonliving structures that have sensation only at the base, where they originate from a follicle. >STRUCTURE -The are six types of feathers that cover a bird's body. The most visible feathers that give shape to a bird are called CONTOUR FEATHERS. Contour feathers have the most compact microstructure & consist of several components >FUNCTION- feathers serve several important functions, *first, they are necessary for flight. A bird without a proper complement of flight features simply cannot fly. *Second, feathers protect the thin skin from trauma, rain, & excessive radiation from sunlight. *Third, they also assist in thermoregulation & camouflage & are used in many communication behaviors, such as courtship, defense, & recognition
Cere
Fleshy colored skin located at the base of the upper beak in many bird species: supplied with touch corpuscles
emiges
Flight feathers in the wing
Treating a damaged blood feather (clinical app)
If a developing feather is cut, nicked, or damaged, it will often bleed profusely. To treat minor nicks or cuts, apply pressure to the affected area. When dry, quick-stop or a tissue glue may be applied to ensure coagulation. Many pet birds are considered prey species & their major flight feathers are loosely seated in the follicles. These birds can drop feathers quickly if grabbed as an aid to escape a predator; seen in aviary cockatiels, which drop all of their tail feathers when caught. > In pet birds, severe injury to a feather occurs, the best way to treat it is often to gently pull out the feather &pack the skin opening with Quick-stop. However, because developing feathers have good nerve supply, anesthetizing the patient to prevent pain or discomfort may be appropriate before pulling a large feather. If bleeding is persistent after a feather is pulled, the skin opening can be sutured closed for a few days to promote hemostasis, but it should be reopened to allow normal healing & new feather growth to begin > In predatory bird species, the feather are seated very strongly in the follicles, & pulling out a flight or tail feather can result in permanent follicle damage, which prevents a new feather from ever growing in. In these species, the proper approach is to stop the bleeding & allow the damaged feather to be removed by the bird or be molted during its normal cycle
Thermoregulation
In addition to the exchange of gases, the respiratory system in birds also help thermoregulation. Air in the lungs picks up heat radiated by warm body tissues & blood & removes it from the body during the breathing process. The evaporation of H2O via the air sacs, lungs, & mouth cavity helps to cool the body to maintain a safe core temperature. This is most critical when outdoor air temperatures rise or when a bird participates in strenuous exercise, such as flight. ♦To increase the amount of cooling, a bird can increase the airflow over its mouth, pharynx, bronchi, & air sacs by increasing its breathing rate. This often results in panting or GULAR FLUTTERING. The latter is often seen in doves, great blue herons (Ardea herodias), pigeons, quail, & owls, & it involves rapid vibrations of their upper throat patch. In addition to a bird's ability to use its respiratory system to remove excess heat, birds can control their body temperature in several other ways: ♦To keep cool, birds bathe or reduce their activity level during the warmest part of the day. ♦Some species, such as turkey vultures & wood storks (Mycteria Americana), defecate on their legs for evaporative cooling. ♦Birds also can adjust the position of their body features to promote both heat loss & retention. ♦To retain heat, many land & water species posses a special artery-vein arrangement in their lower extremities that acts as a countercurrent heat exchange system that limits heat loss through their bare legs ♦Birds also change their posture to conserve heat. This may include perching on one leg to reduce exposure of bare skin to cold air or tucking their beak behind feathers in their back ♦Shivering to increase muscle heat production & moving to more protected locations also helps prevent loss of body heat during times of cold stress. ♦In some smaller species, hummingbirds, short-term NOCTURNAL TORPOR -in which body temperature is decreased several degrees & heart rate & O2 consumption are reduced - is another mechanism for heat conservation.
List unique features of the avian skeleton
In birds, this framework is highly specialized, because it must support two very different modes of locomotion: walking & flying. The lightweight nature of the skeleton was a key component in the evolution of flight & can be explained by seven general modifications: 1. Reduction in the # of bones 2. fusion of bones to form plates that provide strength & simplify movements 3.Reduction in the density of bones, which are relatively thin but strengthen by a network of internal bony braces 4. loss of internal bone matrix (the bones of birds are generally hollow & filled with air spaces
Sternum (axial skeleton)
In most species of birds, it is large & concave. It not only protects the chest from traumatic injuries but also acts as the place of origin of the fight muscles. In strong fliers, the sternum has a large bony ridge, or KEEL, to which the muscles attach. In flightless birds, such as the ostrich, the sternum lacks a keel entirely.
Lungs
In the avian respiratory system, the lungs are relatively small, occupying only about 2% of the total body volume. They are attached to the thoracic vertebrae & ribs & are bright red, highly vascularized, & inelastic. They house the network of blood & air capillaries between which the exchange of gases occurs.
Coping beaks & nail (clinical application)
In the wild, birds maintain their beaks & claws through daily activities. ex., after completing a meal, birds often FEAK, or rub, their beaks on a rough surface to clean them & maintain their shape. Birds in captivity are provided with limited wearing surfaces, birds of prey & psittacines require frequent COPING, or trimming & reshaping, of their beaks & nails. Overgrowth, cracks & chips can occur & cause permanent damage to the beak's growth plate, located near the CERE. Claws become, long, sharp, cause uneven weight bearing on the foot pads or puncture the bottom of the foot. Resulting in pad abrasions, blisters,swelling, abscess formation, & severe cases, degeneration of the bones in the feet, or osteomyelitis. BUMBLEFOOT-term used to describe these conditions of the avian foot. > Coping beaks & claws must be done with care, because both of the structures have a blood & nerve supply that can be hit if they are trimmed too deeply. Beaks can be copped with a fingernail file or rotary tool. Claws can be trimmed using a cat or dog-nail trimmer, depending on the size of the bird. If bleeding occurs, hemostasis can be achieved by applying topical cauterizing agents, such as silver nitrate or quick-stop. In parrots, nails are often with a rotary tool, which cauterizes a blood vessel if it is hit
Leg muscles
Like the wing muscles, the leg muscles also have been moved close to the center of gravity. The majority are located in the thigh region over the femur, a smaller # are located over the TIBIOTARUS, & very few are found over the TARSOMETATARSUS. The large group of muscles over the femur can control movements in the distal leg & toes via strong tendons. Ex., in perching species, tendons that control movement of the toes originate from flexor muscles in the thigh & extend over the heel joint into the digits. Extensor tendons run down the front of the tibiotarsus & metatarsus, whereas the flexor tendons run along the back. When a bird bends its legs to perch, the tendons also bend & pull the toes closed around the perch. This is called the PERCHING REFLEX & allows a bird to firmly grip its perch while sleeping.
Clipping feathers (Clinical app)
Many pet bird owners desire to have their bird's flight feathers clipped. The goal of clipping flight feathers is not to make a bird completely flightless; it is to prevent a bird from gaining lift while still allowing it to glide safely to the ground. This prevents a bird from injuring itself when out of its cage & prevents accidental escape . Numerous pet birds are lost every year because they fly out open doors & windows. > several patterns are used to clip a bird's wing feathers. The one chosen depends on the owner's wishes & personal preference of the clinician. One technique that's common is to trim the outermost five to seven flight feathers under the overlaying coverts providing a smooth appearance to the wing. Another technique leaves the outer two to four primary flight features intact & then trims the next five to seven flight feathers underneath the overlying covert feathers. One problem encountered with this pattern is that the long outer primaries are vulnerable to breakage. Whichever used, the clipping should be done symmetrically on both wings. > another consideration in feather clipping involves the presence of blood feathers. If blood feathers are present, it is advisable to wait until those feathers are completely developed before any are trimmed. If blood feathers are cur or damaged, a significant amount of bleeding often occurs. If waiting is not an option, completely developed feathers can be trimmed such that one feather remains intact on each side of every blood feather. Intact feathers on each side are needed to protect a growing feather from injury
barbules
Microscopic projections off feather barbs that help maintain a contour feather's structure
Feather-picking disorder (clinical application)
One condition of psittacines & some humane-imprinted raptors is feather picking. Birds with this disorder preen excessively, removing most to all of their body feathers, especially on their chest &legs. Also, in severe cases, the skin surrounding the feathers is self-mutilated. >Cause- are either pathological or psychological. In the first category, toxins, bacteria, viruses, fungi, parasites, & malnutrition all can lead to feather picking. To determine, the cause, a thorough physical exam must be conducted. Radiographs, blood samples for complete blood count & serum chemistry, cytology of feather pulp or of a local skin scraping, feather biopsy, & endoscopy are all diagnostic tools that can be used. If the problem does not appear to be physiological, the attention must be turned to psychological causes. These may include changes in the environment, diet, human exposure, boredom, sexual frustration, anxiety, or exposure to new pets. Many parrots, especially African Greys (Psittacus erithacus) are very sensitive to these types of conditions > Treatments vary with the cause, bacterial, viral, parasitic, & fungal infections can be treated with established protocols, & diet can be improved & varied. However, treatment for psychological causes is more difficult, especially if the disorder cannot be attributed to a specific event or situation. Most often, changing components of the care & management of the bird is required, with no guarantee of inhibiting the feather-picking behavior
Describe the anatomical structures of avian beaks,
One derivate of a bird's skin is its beak, or bill. It consists of the upper & low mandible & is covered with a tough, horny keratin layer that grows continuously. Beaks vary in their hardness & flexibility, depending on their function. Some birds use their beaks to crack seeds & nuts (parrots); tear food into bite-sized pieces (hawks); capture food (herons & woodpeckers); preen their feathers or those of a mate; pick up & hold things, such as food & nesting material, as they fly & climb; & sometimes to protect themselves.
Barbs
Slender projections off the main feather shaft. Barbs that help maintain a contour feather's structure
Muscles of the head & neck
The most pronounced muscles of the head are the JAW MUSCLES, which control the beak. The extent of this musculature varies among species & is generally correlated with a bird's diet. Ex., species such as parrots use their beaks to crack open large, coarse seeds, so they have relatively large & strong jaw muscles compared with species that consume smaller seeds, like doves, or those that consume insects. > A bird's has great flexibility in it neck. It has several thin stringy neck muscles that weave through each other & allow movement in different directions. Some muscles are attached to the CT, or fascia, of adjacent neck muscles. When one muscle is stimulated, neighboring muscles contract, making a variety of movements possible. This is best demonstrated in parrot species that move their heads up & down, left & right, & many combinations thereof. One highly specialized muscle in birds is referred to as the HATCHING MUSCLE. This muscle, located on the dorsal side of a chick's head, develops during embryonic stage & is needed to help a chick break out of its shell. It is largest a day or two before hatching, & once a chick reaches the outside world, it rapidly atrophies.
retices
Tail feathers
Freak
The act of rubbing the beak on rough surface to clean it & maintain shape
List the types of feathers and the location of each type
The are six types of feathers that cover a bird's body > CONTOUR feathers typically cover a bird's body & constitute the flight feathers of the wings & tails. The flight feathers in the wing are commonly called EMIGES, & the tail feathers are called RETRICES. Small contour feathers, are found around the external ear openings & improve a bird's hearing ability. They are especially numerous in some species of parrots, hawks, & owls. Contour feathers are moved by muscles attached to the walls of the follicles. >SEMIPLUME feathers possess a main rachis with barbs that lack barbules & hooklets. They are commonly found under contour feathers, especially on the sides of the abdomen & along the neck & back. Like down feathers, semiplumes provide insulation. They also provide flexibility for the movement of the contour feathers & help with buoyancy in water birds. >DOWN feathers are soft, fluffy feathers that lack a true shaft, barbules, & hooklets on their barbs. They are located next to the skin under contour feathers, & they function primarily as insulation > FILOPLUME feather have a bare shaft that lacks barbs on the majority of its length, except at the tip.. They are located on the NAPE & upper back near contour feathers, & their follicles contain sensitive nerve endings that may play a sensory role in controlling feather movement. Slight movement of the contour feathers are transmitted to pressure & vibration receptors in the skin via the filoplume feathers. > BRISTLES are modified contour feathers with a stiff rachis & few barbs at the base. They are thought to serve a bird's sense of touch. Depending on the species, they may be found in various locations.Crows, ravens, & woodpeckers have bristles around their nostrils; owls have them around the mouth & sometimes around their toes, as do grouse; other birds have bristles around their eyes. > POWDER Down feathers are unusual feathers that never stop growing. They grow continuously at the base & disintegrate at their tips, creating waxy powder that is spread throughout the rest of the plumage to clean it & provide waterproofing. They are most highly developed in herons & bitterns, especially on the breast, belly & back; they can be found more diffusely scattered in parrots & hawks. Birds without a UROPYGEAL GLAND have abundant powder down feathers
List the unique features of avian musculature
The average bird has 175 to 200 muscles, many of which have been placed ventrally, near the center of gravity. Reptiles, the avian predecessor, have muscles on their dorsal surface. In birds, these have been replaced with strong plates of fused vertebrae, which protect the skeleton during contraction of the powerful flight muscles. The muscle of birds are classified as SMOOTH or STRAITED & VOLUNTARY or INVOLUNTARY. >Many muscles that contain smooth muscle fibers are also involuntary, stimulating the movement of the internal organs. Many muscles with striated fibers are skeletal & are associated with bone movement, so they are under voluntary control. Cardiac muscle is also striated but has its own intrinsic rhythm that does not require external innervation. >The skeletal muscles can have white or red muscle fibers. some muscle consist primarily of one type or the other, but many have a mixture of both (light meat or dark meat). White fibers are thick & have a low blood supply, have little myoglobin for carrying O2, & use stores of glycogen to sustain muscle contraction. They predominate in the flight muscles of short-distance fliers, such as chickens, quail, grouse, & many other gallinaceous birds( heavy-bodied largely terrestrial birds including pheasants, turkeys, grouse & common domestic chickens) that have rapid takeoffs but are capable of only short flights. If these birds are forced to fly repetitively, they quickly become fatigued & cannot fly at all until they recover. In contrast, red fibers are thinner & have a rich supply of blood, fat myoglobin, & mitochondria. Using these components for long periods. Red fibers are found in the flight muscles of long-distance fliers, including many species of songbirds, water birds, pigeons, & birds of prey.
Muscles
The average bird has 175 to 200 muscles, many of which have been placed, ventrally, near the center of gravity. reptiles, the avian predecessor, have muscles on their dosal surface. In birds, these been replaced with strong plates of fused vertebrae, which protect the skeleton during contraction of the powerful flight muscles.
Skull (axial skeleton)
The bird skull possesses several adaptations for lightness. The bones are thinner than in other animals & instead of supporting heavy teeth, The jaws extend into a keratinized bill. The shape of the bill varies with species, & it consists of a lower & upper components. >The lower bill hinges on two small, moveable bones - QUADRATES. The upper bill has a somewhat flexible attachment to the skull & can move although slightly. Thus their upper & lower bills move independently, gives them greater control in manipulating food & increases the size of their gape. The gape is the size of the bird's mouth when open: larger the gape, larger the pieces of food that can be ingested. > Eye sockets, good vision is important for an aerial creature, & thus a large portion of a bird's skull is devoted to supporting & protecting the eyes. The avian skull has large eye sockets that are bordered by a ring of protective bony plates -SCLEROTIC RING. In most species, a relatively small portion of the skull is devoted to the olfactory system, & the size of the ear canal varies with species & its lifestyle
Respiratory Rate
The breathing rate of birds varies with species, activity level, age, sex, time of day, & outdoor temperature. Smaller birds usually breathe faster than larger birds, & birds in flight have a higher respiratory rate than nonflying birds. The variability in rate under different conditions can make it difficult to use respiratory rate as a diagnostic tool.
Legs
The hip joint in birds is well hidden by thigh muscles & is the place where the femur attaches to the pelvis. The femur (drumstick) is relatively short but wide. It ends at the knee joint, where it is directed a little forward so that the lower part of a bird's leg is placed under it center of gravity. Similar to the pectoral crest of the humerus, the femur possesses two crests called the GREATER & LESSER TROCHANTERS, where the leg muscles attach. > Two bones are located in the middle section of the leg & are called TIBIOTARSUS & FIBULA. The fibula is relatively small in diameter & acts as a splint. These two bones ends at the ankle or HOCK JOINT, & the ankle itself consists of a single, elongated bone -TARSOMETATATSUS
Toxic fumes (clinical application)
The large volume of space present in a bird's respiratory tract, the unidirectional flow of air, & the spatial relationship between the air & blood capillaries create an extremely efficient system that is highly sensitive to gaseous molecules in the air. Fumes from disinfectants, such as concentrated bleach: heated Teflon-coated pans or light bulb covers: moth balls (naphthalene); oil-based paints & varnishes: & exhaust fumes can create illness in birds & even death. Symptoms of exposure to noxious fumes are rapid in onset & may include imbalance, so a bird may fall off its perch & stand fluffed on the floor. Other systems are respiratory riles, or raspy breathing sounds; tail bobbing, in which the tail moves with each labored breath; & severe respiratory distress. Depending on the source of the fumes respiratory distress. Depending on the source of the fumes & extent of exposure, death can quickly occur. Diagnosing the problem relies on obtaining a detailed patient history: treatment revolves around providing support to the respiratory system, which includes reducing stress, providing O2 therapy & warmth, placing an air sac canula to assist with the movement of air, & sometimes administering a mild diuretic to remove fluid from the lungs. However, due to the low rate of survival after exposure to toxic vapors it is critical to educate all bird owners regarding the potential deadly effects of these fumes to prevent exposure in the first place
Microstructure and components of contour feathers
The most visible feathers that give shape to a bird are called CONTOUR FEATHERS. Contour feathers have the most compact microstructure & consist of several components >INFERIOR UMBILICUS- this structure is a tiny opening at the base of the feather, where it inserts into the skin. When a new feather is developing, it receives nourishment from blood vessels that pass through this opening. > SUPER UMBILICUS - This structure is a tiny opening on the feather shaft, where the webbed part of the feather begins. In some birds, including several apecies of parrots, hawks, herons, & grouse, it gives rise to an after feather, which is an accessory feather thought to provide additional insulation to retain body heat >CALAMUS - Also called the QUILL, the calamus is the round, hollow, semitransparent portion of the feather that extends from the inferior umbilicus to the superior umbilicus >RACHIS - the rachis is the main feather shaft > VANE - is the flattened part of a feather that appears web-like on each of the rachis. It consist of numerous slender, closely spaced BARBS, which have rolled edges & tiny hooklets know as HAMULI. These hooklets interlock each barb with an adjacent one forming a tightly linked, flexible web.. The degree of tightness varies with the species. Ex., the contour feathers of owls have fewer barbules than do those of hawks. The result is a loose feather weave that feels softner & allows air to pass through, creating silent flight.
Classification
The muscles of birds are classified as SMOOTH or STRIATED & VOLUNTARY or INVOLUNTARY. Many of the muscles contain smooth muscle fibers are also involuntary, stimulating the movement of the internal organs. Many muscles with striated fibers are skeletal & are associated with bone movement, so they are under voluntary control. > Cardiac muscle is also striated but has it own intrinsic rhythm that does not require external innervation > The skeletal muscle can have white or red muscle fibers. Some muscles consist primarily of one type or the other. White fibers are thick & have a low blood supply, have little myoglobin to sustain for carrying oxygen, & use stores of glycogen to sustain muscle contraction. They predominate in the flight muscles of short-distance fliers, such as chickens, quail, grouse, & many of he gallinaceous birds that have rapid takeoffs but are capable of only short flights. If these birds are forced to fly repetitively, they quickly become fatigued & cannot fly at all until they recover. In contrast, red fibers are thinner & have a rich supply of blood, fat, myoglobin, & mitochondria. Using these components, they can produce enough energy to sustain muscle contractions for long periods. Red fibers are found in the flight muscles of long-distance fliers including many species of songbirds, water birds, pigeons, & birds of prey
Pectoral Girdle (appendicular skeleton)
The pectoral (shoulder) girdle consists of three pairs of bones: CORACOIDS, SCAPULAS, & CLAVICLES. On each side, the coracoid & scapula are joined, forming a depression _GLENOID CAVITY, or TRIOSSEAL CANAL. The wing attaches tot he body by forming a joint in this cavity. During contraction of the powerful flight muscles, the strong, broad coracoids help to protect the sternum; the scapulas, positioned along the backbone, help protect the rib cage; & the clavicles, aka as the WISHBONE, are positioned outward & forward from the body & keep a bird's shoulders separated. >WINGS - are connected to the body by forming a joint with the shoulder girdle. This joint is highly flexible, allowing rotation of the wing in several planes. The humerus extends from the shoulder to the elbow joint & possesses a PECTORAL CREST for the attachment of wing muscles. Humerus length varies among species, being relatively short in birds that depend primarily on flapping flight & relatively long in birds that glide & soar. > the elbow joint is less flexible than the shoulder, & it only allows wing movement parallel to the wing. The radius & ulna extend from this joint to the wrist. The ulna has a large diameter than the radius & acts as an attachment point for the secondary flight feathers. These two bones create the forearm of the wing & slide past each other slightly during flight. > Extending from the shoulder to the wrist is a web of skin -PATAGIUM, or PROPATAGIUM. This skin is lightly vascularized & possesses a ligament that runs along its cranial edge. Provides elasticity to the wing & assists in aerodynamics of flight. (If a bird damages it patagium, it may be grounded permanently). The wrist joint consists of two bones &, like the elbow, allows movement only in the plane of the wing. The 1st finger -ALULA BONE, originates from the wrist & carries the alula feathers, which are important for steering. The major & minor metacarpal bones extend from the wrist & join with the 2nd &3rd fingers near the distal end of the wing. These two fingers, along with the metacarpal bones, support the primary flight feathers.
Plasma
The plasma is about 80% H2O. The remaining 20% consists of a variety of substances, including salts, glucose, fats, amino acids, hormones, antibodies, vitamins, enzymes, waste products, & special blood proteins. These proteins are important for maintaining normal levels of H2O & blood in tissues by osmotic pressure.
remiges
The primary & secondary flight feathers in the wing
coping
The process of trimming & shaping a bird's beak
Describe the anatomical structures of avian skin
The skin of birds consist of two layers : an outer layer -epidermis & inner layer - dermis. Epidermis is relatively thin & consists of flattened epithelial cells that produce keratin, a tough fibrous protein necessary for the production of scales, feathers, & the outer sheath of beaks & claws. The inner layer of the skin (dermis) is thicker & consists of a tough, fibrous CT. It stores fat for nutrition & insulation & supplies a pathway for nerves, blood vessels, & muscles to reach the epidermis. Smooth muscles in the dermis innervate FEATHER FOLLICLES to help in the regulation of heat. > during hot weather, depressor muscles press the feathers against the body to promote heat loss. When a bird gets cold or ill, it looks "fluffed" because erector muscles in the dermis elevate the body feathers to trap warm air near the body
WBCs
There are several types of WBCs, & each type has a different function: > HETEROPHILS - These cells are equivalent to the mammalian neutrophils. They are generally round, have a bilobed nucleus with clumped chromatin, & have rod-shaped, re-orange granules in the cytoplasm. Heterophils are phagocytic cells that engulf foreign matter. A rise in the # of heterophils is usually seen with the onset of acute disease. > EOSINOPHILS-These cells are the same as the mammalian eosinophils. They are round cells with a lobed nucleus & large, re-orange, round granules in the cytoplasm. Their #s increase in response to allergic reactions & heavy internal parasite loads. > BASOPHILS- These cells are identified by a round, centrally placed nucleus & stain dark blue. The function of basophils is still being investigated. > MONOCYTES- These cells are phagocytic cells that act as a body's second line of cellular defense. The nucleus is often shaped like a kidney bean & can be located centrally or off to one side. An increase in monocyte production is often in cases of tuberculosis & aspergillosis > LYMPHOCYTES - These cells are the essential components of the immune system. Their centrally placed nucleus is round & contains densely clumped chromatin. They are produced by the thymus & bursa of Fabricius: lymphocytes originating from the bursa of Fabricius produce humeral antibodies to help fight off infections. >THROMBOCYTES- Are nucleated cells that act as platelets. They are smaller the RBCs & have a large, round to oval nucleus. They are important in blood clotting ^ are produced by bone marrow in adult birds.
Airflow
Two inhalations & two expirations are required to one pocket of air through the entire respiratory system. ♦To begin the cycle, the first inhalation involves an expansion of the thoracoabdominal space; *birds do not have a diaphragm*, the major inspiratory muscle in mammals, so this expansion creates pressure gradient that rings air into the body. Most of the air flows into the posterior air sacs ( abdominal & caudal thoracic), where it is warmed & humidified. With the first expiration, this air is pushed into the lungs, where gas exchange occurs. ♦The second inspiration results in the air moving out of the lungs & into the anterior air sacs ( cranial thoracic, cervical, interclavicular), & the second expiration results in air leaving the body through the trachea. > The key factor in the flow of air through a bird's respiratory system is that air is pushed into the lungs, not pulled in. More than any other group of animals, birds truly can get a "breath of fresh air". Fresh air flows in a continuous, unidirectional path in the lungs & does not get mixed with dirty air containing waste products. This unique feature allows each breath of air to reach the lung capillaries with the maximum amount of O2 possible, close to 21% present in atmospheric air. In contrast, the lungs of mammals inflate & deflate, always leaving quantity of residual air. When new air comes in, it mixes with air remaining in the lungs, diluting the percentage of O2 available for gas exchange. ♦ Another unique feature that contributes to its high efficiency is the flow between the air & blood capillaries. The air capillaries are positioned at right angles to the blood capillaries so that CO2 is continually removed from the blood & O2 is continually added.
Glands
Unlike mammals, birds do not posses sweat glands. Feathers cover such large portion of the bird's body that sweat glands would not be effective. The one major gland that most birds do posses is UROPYGEAL GLAND, or PREEN GLAND. It is located on the dorsal surface at the upper base of the tail. The act of preening stimulates this gland to secrete an oily, fatty substance. > a bird uses its beak to spread this oil throughout its feathers to clean & waterproof them. The gland varies in size & structure & is relatively large in aquatic species, such as waterfowl & osprey. The gland is completely lacking in some parrots, ostriches, in a few other species.
Wing muscles
Wings posses several pairs of muscles that are each responsible for a specific action or counteraction: raising or depressing the leading edge of the wing, pulling the wing forward or backward, extending or flexing the wing. or controlling movements of the ALULA BONE (thumb). > Two most prominent muscle pairs are those responsible for depressing & elevating the wing. Both pairs are those originate on the sternum but differ in where they insert. The larger, more superficial muscle is called PECTORALIS, & it inserts on the UNDERSIDE of the HUMERUS. When it contracts, it DEPRESSES the wing, causing the DOWNSTOKE. This stroke requires a large muscle because it works against two resistant forces: gravity & a tight wing structure formed when the leading edge of each flight feather touches the adjacent feather. Because of its relatively large size & accessibility, the pectoralis is the muscle of choice for administering intramuscular injections, such as vitamins & antibiotics. > The smaller, deeper flight muscle is called the SUPRACORACOIDEUS; it urns into a TENDON that passes through the GLENOID CAVITY formed by the SHOULDER GIRDLE & inserts on TOP of the HUMERUS. When it contracts, it causes the COUNTERACTION, which is the ELEVATION of the wing during the UPSTROKE. During this stroke, the flight feathers slightly separate from each other, allowing air to pass through. This creates less resistance & allows the wing to move more easily. In strong, log-distance fliers, the two pairs of flight muscles constitute between 20% & 25% of a birds weight.
uropygial gland
aka PREEN GLAND; secretes an oily substance that cleans & waterproofs feathers
feather follicle
depression in the skin that gives rise to & stabilizes a new feather
Vertebral column (axial skeleton)
it is similar to that of other animals in that it consists of five general groups of vertebrae : CERVICAL, THORACIC, LUMBAR, SACRAL & COCCYGEAL. Birds have fewer vertebrae than other animals in the three central regions, but they have more vertebrae in the cervical & coccygeal areas, allowing for greater mobility of the neck & tail, respectively. >CERVICAL VERTEBRAE -1st, CV, the atlas, contains a single condyle ( ball & socket type of structure) for attachment to the skull. This allows for greater range of head movements as compared with mammals, which have two condyles attaching the skull to the vertebrae column. Birds have more CV than mammals, ranging from 11 in parakeets to 25 in swans, whereas all mammals have 7. In birds, these vertebrae have special connecting surfaces that allow movement, thus contributing to flexibility of their necks. > THORACIC VERETBRAE - are rigid & provide a strong support for the rib cage. In birds, the first few ribs are relatively short & incomplete. The other ribs are complete, attach to the underside of the sternum, & possess a projection - UNCINATE PROCESS that over-laps the adjoining rear ribs to strengthen the rib cage. One exception to the rigidity of these vertebrae is found in penguins; these birds swim like fish & require a great degree of flexibility in their backs >LUMBAR & SACRAL VERTEBRAE- these two groups are also rigid. Several of the distal LV fuse with the SV & the first few COCCYGEAL VERTEBRAE to form a light, strong, bony plate -SYNSACRUM. When a bird lands, the synsacrum acts as a shock absorber to protect the legs & backbone from injury. > COCCYGEAL VERTEBRAE - birds have an average of 12 CyV. The 1st few are mobile to allow movement of the tail feathers during flight. The rest are fused into a bony structure- PYGOSTLE that supports the tail feathers
hameli
microscopic nooks that links barbules together
Pelvic Girdle
provides a rigid framework for support of the legs. Each side is made up of three bones that join where the leg attaches to the body: ILEUM - is relatively broad & is fused to the synsacrum: ISCHIUM, & PUBIS-are thin & long & are fused to the anterior ileum & directed rearward, parallel to the backbone. The distal ends of these three bones are not fused, leaving the lower part of the pelvis open. this provides room for the abdomen & facilitates egg laying in hens.
auriculars
small contour feathers located around the external ear opening within birds
List the unique features of the avian circulatory system
♦HEART - has four-chambers that consist of a RIGHT ARTIUM, RIGHT VENTRICLE, LEFT ARTIUM & LEFT VENTRICLE. The right side is smaller & less muscular, pumping blood only to the lungs. The left side is larger, & it has well-developed muscles that pump blood to the rest of the blood. The heart is located cranial portion of the throracoabdominal space. It is enclosed a thin, fibrous pericardial sac, which contains fluid that aids in the lubrication of the heart muscle. This sac, adheres to several internal surfaces to keep the anchored in place. VESSELS- The heart is supported by a group of vessels that provide channels for the passage of blood. Arteries carry oxygenated blood from the heart to the tissues, & veins carry blood containing metabolic waste products away from the tissues & back to the heart. Capillaries are small vessels in which the exchange of gases & nutrients occurs. To meet the specific demands of the avian body, some of these vessels are highly specialized in the following way: (1.) The pectoral & brachial arties provide blood to the flight muscles & wings, respectively, & are relatively large. (2.) Birds posses a RENAL PORTAL SYSTEM that begins & ends in a network of capillaries. Blood returning from the extremities via the iliac veins travel to the kidneys. Valves at the junction of the iliac veins travels to the kidneys. Valves at the junction of the iliac veins & renal (kidney) veins steer blood either to the kidneys, so metabolic waste products can be removed, or directly to the heart via the posterior vena cava. (3.) Many aquatic & terrestrial species possess a counter-current system of heart exchange in their lower extremities. This system consists of a network of arteries & veins that are placed close together. Heat from arterial blood traveling to the lower extremities is transferred to the cooler, venous blood returning to the heart. Thus blood reaching the lower extremities is cooler, & less of a temperature gradient exists with the environment. This feature reduces the amount of heat loss. >BLOOD- Birds are active & have a relatively high body temperature -between 37° & 42° C. To maintain this temperature & generate body heat, they also have a relatively fast metabolism. High demands on the circulatory to deliver O2 & nutrients to tissues quickly & efficiently. Demands are met with a relatively fast heart rate; smaller birds have a faster heart rate than larger species, subsequently, more rapid blood flow ({ex., 6 seconds for blood to make a complete circuit in unstressed chickens].
