19. Avian Anatomy and Physiology


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  • 19. Avian Anatomy and Physiology

    1. 1. Avian Anatomy and Physiology
    2. 2. Learning Objectives <ul><li>Describe the anatomical structures of avian skin, beaks, and claws. </li></ul><ul><li>Describe the structure and functions of feathers. </li></ul><ul><li>List the types of feathers and the location of each type. </li></ul><ul><li>List the unique features of the avian skeleton and musculature. </li></ul><ul><li>Describe the shape and general characteristics of avian eyes and explain how those characteristics effect visual acuity. </li></ul><ul><li>Describe the unique anatomical features that affect the sense of hearing in nocturnal owls. </li></ul><ul><li>List the unique anatomical features that affect the sense of taste in birds. </li></ul><ul><li>List the components of the avian digestive system and describe the functions of each. </li></ul><ul><li>List the unique features of the avian circulatory and respiratory systems. </li></ul><ul><li>Describe the composition of avian urine. </li></ul><ul><li>List and describe the unique features of the avian male and female reproductive systems. </li></ul><ul><li>List and describe the four classifications of newly hatched chicks. </li></ul>
    3. 3. Skin <ul><li>Epidermis : thin layer of flattened epithelial cells that produce keratin </li></ul><ul><ul><li>Fibrous protein necessary for the production of scales, feathers, and outer sheath of beaks and claws </li></ul></ul>
    4. 4. Skin <ul><li>Dermis : thick layer of fibrous connective tissue </li></ul><ul><ul><li>Stores fat for nutrition </li></ul></ul><ul><ul><li>and insulation </li></ul></ul><ul><ul><li>Smooth muscles in </li></ul></ul><ul><ul><li>dermis innervate </li></ul></ul><ul><ul><li>feather follicles to </li></ul></ul><ul><ul><li>aid in heat regulation </li></ul></ul>
    5. 5. Glands <ul><li>Uropygial (preen) gland : </li></ul><ul><ul><li>On dorsal surface at upper base of the tail </li></ul></ul><ul><ul><li>Preening stimulates secretion of an oily, fatty substance </li></ul></ul><ul><ul><li>Bird uses beak to spread the oil throughout its feathers to clean and waterproof them </li></ul></ul>
    6. 6. Beak <ul><li>Derivative of skin </li></ul><ul><li>Upper and lower mandible covered with a horny keratin layer </li></ul><ul><li>Grows continuously </li></ul><ul><li>Variable hardness and flexibility, depending on the function </li></ul>
    7. 7. Claws <ul><li>Horny sheath derived from specialized scales at the end of each toe </li></ul><ul><li>Grow continuously </li></ul><ul><li>Variable types of claws, depending on perching habits and method of procuring food </li></ul>
    8. 8. Feathers <ul><li>Outgrowths of skin </li></ul><ul><li>Made of protein </li></ul><ul><li>Functions: </li></ul><ul><ul><li>Flight </li></ul></ul><ul><ul><li>Protect thin skin from trauma, rain, and excessive radiation from sunlight </li></ul></ul><ul><ul><li>Assist in thermoregulation and camouflage </li></ul></ul><ul><ul><li>Used in communication behaviors (e.g., courtship, defense, and recognition) </li></ul></ul>
    9. 9. Feather Structure <ul><li>Inferior umbilicus : opening at base of feather </li></ul><ul><li>Superior umbilicus : opening on feather shaft where webbed part of the feather begins </li></ul><ul><ul><li>May give rise to an afterfeather : accessory feather thought to provide additional insulation </li></ul></ul><ul><li>Calamus : quill; round, hollow, semitransparent </li></ul><ul><ul><li>Extends from inferior to superior umbilicus </li></ul></ul><ul><li>Rachis : main feather shaft </li></ul>
    10. 10. Feather Structure <ul><li>Vane : flattened part of a feather </li></ul><ul><ul><li>Numerous slender, closely spaced barbs that give rise to barbules containing hooklets (hamuli) </li></ul></ul><ul><ul><li>Hooklets interlock </li></ul></ul><ul><ul><li>each barb with an </li></ul></ul><ul><ul><li>adjacent one </li></ul></ul>
    11. 11. Types of Feathers <ul><li>Contour Feathers </li></ul><ul><li>Flight feathers of the wings and tail </li></ul><ul><li>(remiges and retrices) </li></ul><ul><ul><li>Moved by muscles attached to the walls of </li></ul></ul><ul><ul><li>the follicles </li></ul></ul><ul><li>Auriculars : small contour feathers </li></ul><ul><li>around external ear openings </li></ul><ul><ul><ul><li>Improve bird’s hearing ability </li></ul></ul></ul>
    12. 12. Types of Feathers <ul><li>Semiplume Feathers </li></ul><ul><li>Have main rachis with barbs and no barbules or hooklets </li></ul><ul><li>Found under contour feathers </li></ul><ul><li>Provide insulation </li></ul><ul><li>Provide flexibility for movement </li></ul><ul><li>of contour feathers </li></ul><ul><li>Help with buoyancy in water birds </li></ul>
    13. 13. Types of Feathers <ul><li>Down feathers </li></ul><ul><li>Soft, fluffy feathers </li></ul><ul><li>Lack a true shaft </li></ul><ul><li>No barbules or hooklets </li></ul><ul><li>Located next to skin </li></ul><ul><li>under contour feathers </li></ul><ul><li>Function in insulation </li></ul>
    14. 14. Types of Feathers <ul><li>Filoplume Feathers </li></ul><ul><li>Bare shaft with barbs on the tip </li></ul><ul><li>Located on the nape and upper back </li></ul><ul><li>near contour feathers </li></ul><ul><li>Nerve endings in follicles may play role </li></ul><ul><li>in controlling feather movement </li></ul>
    15. 15. Types of Feathers <ul><li>Bristles </li></ul><ul><li>Modified contour feathers </li></ul><ul><li>Stiff rachis with few barbs at the base </li></ul><ul><li>May play role in sense of touch </li></ul><ul><li>May be found around the eyes, </li></ul><ul><li>nostrils, mouth, and toes </li></ul>
    16. 16. Types of Feathers <ul><li>Powder Down Feathers </li></ul><ul><li>Grow continuously at the base </li></ul><ul><li>Disintegrate at their tip </li></ul><ul><li>Create waxy powder that spreads throughout the rest of the plumage </li></ul><ul><li>Birds without a uropygial gland have abundant powder down feathers </li></ul>
    17. 17. Feathers <ul><li>Pterylae : tracts where feathers are located </li></ul><ul><li>Apteria : bare areas of skin between pterylae </li></ul><ul><li>Feathers in pterylae overlap one another </li></ul>
    18. 18. Feather Damage <ul><li>Feather mites and other external parasites can chew and consume parts of the feather vanes </li></ul><ul><li>Daily wear and tear: lighter tips of flight and tail feathers can be worn off </li></ul>
    19. 19. Feather Damage <ul><li>Fault bar (stress bar): weakened area on the feather vane where barbs lack barbules </li></ul><ul><ul><li>Results from stress that interrupts blood flow during feather growth </li></ul></ul><ul><ul><ul><li>Common stressor: poor diet </li></ul></ul></ul>
    20. 20. Molting <ul><li>Process of feather replacement </li></ul><ul><li>Occurs once to several times a year, depending on species </li></ul><ul><li>In most species, feather replacement is symmetrical </li></ul><ul><ul><li>One or two pairs of flight feathers molted at a time </li></ul></ul><ul><ul><li>Many species of waterfowl molt all flight feathers at once after the breeding season </li></ul></ul>
    21. 21. Molting <ul><li>Feathers develop from papillae in feather tracts of the dermis </li></ul><ul><li>Contain cells with genetic information that dictates type, size, and color of feathers </li></ul><ul><li>Hormones stimulate molting, activate cells in papillae </li></ul>
    22. 22. Molting <ul><li>Newly developing feather pushes old feather out </li></ul><ul><li>Feather emerges covered by periderm </li></ul><ul><ul><li>Periderm removed by preening </li></ul></ul><ul><li>Blood vessels from dermis reach into new feather </li></ul><ul><ul><li>When feather is fully grown, blood dries up </li></ul></ul>
    23. 23. Skeletal System
    24. 24. Skeletal System <ul><li>Skeletal modifications allow for flight and walking: </li></ul><ul><ul><li>Reduction in number of bones </li></ul></ul><ul><ul><li>Fusion of some bones to form plates </li></ul></ul><ul><ul><li>Reduction in bone density </li></ul></ul><ul><ul><li>Loss of internal bone matrix; bone becomes hollow and filled with air spaces </li></ul></ul>
    25. 25. Skull <ul><li>Skull bones are thinner than in other animals </li></ul><ul><li>Jaws extend into a keratinized bill </li></ul><ul><li>Large eye sockets bordered by sclerotic ring </li></ul><ul><ul><li>Protective bony plates </li></ul></ul>
    26. 26. Vertebral Column <ul><li>Cervical Vertebrae: </li></ul><ul><li>Atlas contains a single condyle for attachment of the skull </li></ul><ul><ul><li>Allows greater range of head movements </li></ul></ul><ul><li>Greater number of cervical vertebrae than mammals </li></ul><ul><ul><li>Variable in different species </li></ul></ul>
    27. 27. Vertebral Column <ul><li>Thoracic Vertebrae: </li></ul><ul><li>Rigid and provide a strong support for the rib cage </li></ul><ul><ul><li>First few ribs are relatively short and incomplete </li></ul></ul><ul><ul><li>Remaining ribs attach to underside of sternum and have a projection (uncinate process) that overlaps the adjoining rear rib to strengthen the rib cage </li></ul></ul>
    28. 28. Vertebral Column <ul><li>Lumbar and Sacral Vertebrae: </li></ul><ul><li>Synsacrum : strong bony plate created from fusion of several distal lumbar vertebrae, sacral vertebrae, and first few coccygeal vertebrae </li></ul><ul><ul><li>Synsacrum fuses with the pelvis, supports the legs </li></ul></ul><ul><li>Coccygeal vertebrae: </li></ul><ul><li>First few are mobile </li></ul><ul><li>Pygostyle : bony structure created from fusion of some coccygeal vertebrae </li></ul>
    29. 29. Sternum <ul><li>Large and concave </li></ul><ul><li>Site of origin of flight muscles </li></ul><ul><li>In some species, muscles attach to large bony ridge or keel </li></ul><ul><li>In flightless birds sternum lacks a keel </li></ul>
    30. 30. Pectoral Girdle <ul><li>Paired coracoids, scapulas, and clavicles </li></ul><ul><li>Glenoid cavity (triosseal canal): formed from joining of scapula and coracoid </li></ul><ul><ul><li>Site of wing joint attachment </li></ul></ul><ul><li>Clavicles (wishbone): positioned outward and forward from the body </li></ul>
    31. 31. Wings <ul><li>Joint at shoulder allows rotation in several planes </li></ul><ul><li>Humerus : wing muscles attach at pectoral crest of humerus </li></ul><ul><ul><li>Humerus length varies </li></ul></ul><ul><ul><li>Shorter in birds with flapping flight; longer in birds that glide and soar </li></ul></ul>
    32. 32. Wings <ul><li>Joint at elbow only allows movement parallel to wing </li></ul><ul><li>Ulna has a larger diameter than radius </li></ul><ul><li>Patagium (propatagium): web of skin </li></ul><ul><ul><li>Ligament runs along its cranial edge </li></ul></ul><ul><ul><li>Provides elasticity to the wing and assists in the aerodynamics of flight </li></ul></ul>
    33. 33. Wings <ul><li>Alula bone : originates from the wrist and carries the alula feathers (steering feathers) </li></ul><ul><li>Metacarpal bones join with the second and third fingers near the distal end of the wing </li></ul><ul><ul><li>Help support the primary flight feathers </li></ul></ul>
    34. 34. Pelvic Girdle <ul><li>Three paired bones that join where the leg attaches to the body </li></ul><ul><li>Ileum : broad and fused to the synsacrum </li></ul><ul><li>Ischium and pubis : thin, long, and fused to the ileum anteriorly </li></ul>
    35. 35. Hip <ul><li>Femur (drumstick): short and wide; directed forward at the knee </li></ul><ul><ul><li>Allows for lower part of bird's leg to be under its center of gravity </li></ul></ul><ul><li>Greater and lesser trochanters on femurs: site of attachment of leg muscles </li></ul><ul><li>Tibiotarsus and Fibula : end at the hock joint </li></ul><ul><li>Hock : single, elongated bone ( tarsometatarsus ) </li></ul>
    36. 36. Feet <ul><li>Metatarsal pad : bottom of foot; surrounded by two, three, or four toes </li></ul><ul><li>Anisodactyl : one toe faces the rear, other three face forward </li></ul><ul><li>Zygodactyl : second and third toes face forward, first and fourth are directed backward </li></ul><ul><li>Digits are numbered: </li></ul><ul><ul><li>Digit one (rear toe) - one joint; Digit two (medial) - two joints; Digit three - three joints; Digit four (lateral) - four joints </li></ul></ul>
    37. 37. Muscles <ul><li>Skeletal muscles - can have white or red muscle fibers or combination of both </li></ul><ul><ul><li>White fibers : thick in diameter, low blood supply, little myoglobin </li></ul></ul><ul><ul><ul><li>Use stores of glycogen to sustain muscle contraction </li></ul></ul></ul><ul><ul><ul><li>Found in flight muscles of short-distance fliers </li></ul></ul></ul><ul><ul><li>Red fibers : thin, have rich supply of blood, fat, myoglobin, and mitochondria </li></ul></ul><ul><ul><ul><li>Found in flight muscles of long-distance fliers </li></ul></ul></ul>
    38. 38. Wing Muscles <ul><li>Raise or depress leading edge of wing </li></ul><ul><li>Pull wing forward or backward </li></ul><ul><li>Extend or flex wing </li></ul><ul><li>Control movements of alula bone </li></ul>
    39. 39. Flight Muscles <ul><li>Pectoralis : large, superficial </li></ul><ul><ul><li>Origin: sternum </li></ul></ul><ul><ul><li>Insertion: underside of humerus </li></ul></ul><ul><ul><li>Depresses wing (downstroke) </li></ul></ul><ul><li>Supracoracoideus : small, deeper </li></ul><ul><ul><li>Origin: sternum </li></ul></ul><ul><ul><li>Insertion: top of humerus </li></ul></ul><ul><ul><li>Elevates wing (upstroke) </li></ul></ul>
    40. 40. Leg Muscles <ul><li>Primarily located over the femur </li></ul><ul><li>Small number located over the tibiotarsus and tarsometatarsus </li></ul>
    41. 41. Muscles of the Head and Neck <ul><li>Extent of jaw muscles vary, depending on bird's feeding habits </li></ul><ul><li>Neck muscles allow movement in different directions </li></ul><ul><li>Hatching muscle : used to help chick break shell open </li></ul><ul><ul><li>Atrophies after hatching </li></ul></ul>
    42. 42. Sense Organs <ul><li>Location of control centers of brain are similar to mammals </li></ul><ul><li>Control centers for vision and hearing are relatively large </li></ul><ul><li>Control centers for </li></ul><ul><li>taste, touch, and smell are relatively small </li></ul>
    43. 43. Vision <ul><li>Highly developed </li></ul><ul><li>Optic lobes make up majority of midbrain </li></ul><ul><li>Eye shape determined by the orbits </li></ul><ul><ul><li>Diurnal birds usually have round or flat eyes </li></ul></ul><ul><ul><li>Nocturnal species have tubular eyes </li></ul></ul><ul><li>Position of eyes varies </li></ul>
    44. 44. Anatomy of the Eye <ul><li>Fibrous tunic : sclera, cornea </li></ul><ul><ul><li>Sclera contains ring of bones: sclerotic ring </li></ul></ul><ul><li>Uveal tunic : choroid, iris, ciliary muscles </li></ul><ul><ul><li>Nictitating membrane may have clear center </li></ul></ul><ul><li>Neural tunic : retina </li></ul><ul><ul><li>Pectin: vascular structure attached to retina </li></ul></ul>
    45. 45. Photoreception <ul><li>Rods and cones similar to mammals </li></ul><ul><li>Nocturnal birds have more rods than cones </li></ul><ul><ul><li>Rods contain rhodopsin - night vision pigment </li></ul></ul><ul><li>Retina : lightly vascularized and contains numerous photoreceptor cells </li></ul><ul><li>Some species have a second temporal fovea rather than a single central fovea </li></ul><ul><li>Birds can see wide spectrum of wavelengths </li></ul>
    46. 46. Hearing and Equilibrium <ul><li>Ears are located behind and slightly below the eyes </li></ul><ul><li>Columella : single bone in middle ear </li></ul><ul><li>External ear is often bordered with auricular feathers </li></ul>
    47. 47. Hearing in Nocturnal Owls <ul><li>Operculum : fleshy flap of skin at each external ear opening </li></ul><ul><ul><li>Helps funnel sound into the ears </li></ul></ul><ul><li>Ear openings are asymmetrical </li></ul><ul><ul><li>Helps with vertical location of sound </li></ul></ul>
    48. 48. Hearing in Nocturnal Owls <ul><li>Large eardrums, columellae, cochleae, and well-developed acoustic center in the hindbrain </li></ul><ul><li>Very large number of auditory neurons </li></ul>
    49. 49. Taste & Touch <ul><li>Taste buds: few in number; scattered on sides of tongue and soft palate </li></ul><ul><li>Nerve endings for touch </li></ul><ul><ul><li>Grandry's corpuscle : in the tongue and palate of species that dig for food </li></ul></ul><ul><ul><li>Herbst corpuscle : sensitive to feather movement </li></ul></ul>
    50. 50. Smell <ul><li>Highly variable </li></ul><ul><li>In some species, well developed and needed for locating food </li></ul><ul><li>In other species, less developed but adequate </li></ul>
    51. 51. Endocrine System <ul><li>Seven major endocrine glands </li></ul><ul><li>Function similar to mammals </li></ul>
    52. 52. Digestive System
    53. 53. Digestive System <ul><li>Beaks - vary with diet and foraging habits </li></ul><ul><ul><li>Seedeaters - thick, crushing beak </li></ul></ul><ul><ul><li>Woodpeckers - heavy, blunt, chiseling beak </li></ul></ul><ul><ul><li>Raptors - sharp-edged, tearing, hooked beak </li></ul></ul><ul><ul><li>Shorebirds - long, delicate, probing beak </li></ul></ul>
    54. 54. Digestive System <ul><li>Mouth: consists of hard upper palate, soft lower palate, distinctive tongue, salivary glands, taste buds </li></ul><ul><ul><li>Soft palate may be enlarged into a pouch used to temporarily store food </li></ul></ul><ul><li>Tongue: has few muscles in most species </li></ul><ul><li>Crop: expansion of esophagus over the furcula in some species </li></ul><ul><ul><li>Storage pouch for food </li></ul></ul>
    55. 55. Stomach <ul><li>Two compartments: glandular stomach, muscular stomach </li></ul><ul><li>Proventriculus : anterior glandular stomach; site where chemical digestion begins </li></ul><ul><li>Gizzard : muscular stomach; striated muscles that grind food </li></ul><ul><ul><li>Many birds ingest small pieces of grit to aid in grinding food </li></ul></ul>
    56. 56. Liver and Pancreas <ul><li>Liver </li></ul><ul><li>Bilobed, right lobe larger than left </li></ul><ul><li>Pancreas </li></ul><ul><li>Relatively large; rests in the loop of the duodenum </li></ul><ul><li>Endocrine portion of pancreas occupies more tissue mass than in mammals </li></ul>
    57. 57. Digestive System <ul><li>Duodenum </li></ul><ul><li>Main digestive organ; varies in length and thickness depending on diet </li></ul><ul><li>Ceca </li></ul><ul><li>Paired sacs at junction of small and large intestines in some species </li></ul><ul><li>Play role in water reabsorption and bacterial fermentation of cellulose </li></ul><ul><li>Contents excreted independent of fecal material </li></ul>
    58. 58. Cloaca <ul><li>End of digesive tract </li></ul><ul><li>Coprodeum : anterior section; receives excrement from the intestine </li></ul><ul><li>Urodeum : receives discharge from the kidneys and genital ducts </li></ul><ul><li>Proctodeum : posterior section; stores the excrement </li></ul><ul><li>Vent : muscular anus </li></ul>
    59. 59. Feeding Habits <ul><li>Diet is determined by: </li></ul><ul><ul><li>Physical characteristics (type of bill, feet, plumage, development of senses) </li></ul></ul><ul><ul><li>Daily activity cycle (diurnal vs. nocturnal) </li></ul></ul><ul><ul><li>Flight style and endurance </li></ul></ul><ul><ul><li>Habitat, time of year, geographical location </li></ul></ul><ul><ul><li>Sex </li></ul></ul><ul><ul><li>Age </li></ul></ul>
    60. 60. Heart <ul><li>Four-chambered heart </li></ul><ul><li>In cranial portion of the thoracoabdominal space </li></ul><ul><li>Enclosed by thin, fibrous fluid-filled pericardial sac </li></ul><ul><ul><li>Adherent to several internal surfaces </li></ul></ul>
    61. 61. Blood Vessels <ul><li>Pectoral and brachial arteries </li></ul><ul><ul><li>Large; provide blood </li></ul></ul><ul><ul><li>to flight muscles and wings </li></ul></ul>
    62. 62. Blood Vessels <ul><li>Renal portal system </li></ul>
    63. 63. Blood Vessels <ul><li>Countercurrent heat exchange system </li></ul><ul><ul><li>In lower extremities of some species </li></ul></ul><ul><ul><li>Network of arteries and veins placed close together </li></ul></ul><ul><ul><li>Heat from arterial blood transferred to cooler venous blood </li></ul></ul>
    64. 64. Blood <ul><li>Erythrocytes </li></ul><ul><ul><li>Oval, nucleated </li></ul></ul><ul><ul><li>Percentage of red blood cells in a healthy adult bird ~ 35% - 55% </li></ul></ul><ul><li>Heterophils </li></ul><ul><ul><li>Equivalent to neutrophils </li></ul></ul><ul><ul><li>Bilobed nucleus </li></ul></ul><ul><ul><li>Rod-shaped red-orange granules </li></ul></ul>
    65. 65. Respiratory System
    66. 66. Oral Cavity <ul><li>Glottis : opening of trachea at back of tongue </li></ul><ul><li>Choanae : internal nares </li></ul><ul><ul><li>Open from nasal chambers into roof of mouth </li></ul></ul><ul><li>Larynx : does not function in production of sound as in mammals </li></ul>
    67. 67. Oral Cavity <ul><li>Trachea : long and coiled (some species) </li></ul><ul><li>Syrinx : enlargement of trachea above lungs </li></ul><ul><ul><li>Muscles, air sacs, and vibrating membranes </li></ul></ul><ul><ul><li>Vocalization complexity depends on number of muscles present in syrinx </li></ul></ul>
    68. 68. Bronchi <ul><li>Mesobronchi - in lungs </li></ul><ul><ul><li>No cartilaginous rings </li></ul></ul><ul><ul><li>Divide into secondary bronchi (ventrobronchi) </li></ul></ul><ul><li>Ventrobronchi - divide into parabronchi </li></ul><ul><li>Parabronchi - connect to air capillaries </li></ul><ul><ul><li>Site of gas exchange </li></ul></ul>
    69. 69. Air Sacs <ul><li>Thin walled, lightly vascularized membranes </li></ul><ul><ul><li>Paired - cranial thoracic, caudal thoracic, cervical, and abdominal air sacs </li></ul></ul><ul><ul><li>Unpaired - interclavicular air sac </li></ul></ul><ul><li>Reservoirs for air </li></ul><ul><li>Provide warmth and moisture to facilitate diffusion of air through capillaries </li></ul><ul><li>Aid in thermoregulation </li></ul><ul><li>Help provide buoyancy </li></ul>
    70. 70. Lungs <ul><li>Small, inelastic </li></ul><ul><li>Attached to thoracic vertebrae and ribs </li></ul><ul><li>Air capillaries are at right angles to the blood capillaries </li></ul><ul><ul><li>Carbon dioxide continually removed from blood and oxygen continually added </li></ul></ul>
    71. 71. Air Flow <ul><li>Inspiration: expansion of thoracoabdominal space </li></ul><ul><ul><li>Creates pressure gradient that brings air into posterior air sacs </li></ul></ul><ul><li>Expiration pushes air into the lungs </li></ul>
    72. 72. Air Flow <ul><li>Second inspiration moves air out of the lungs and into the anterior air sacs </li></ul><ul><li>Second expiration moves air out through the trachea </li></ul>
    73. 73. Respiratory Rate <ul><li>Varies with species, activity level, age, sex, time of day, and outdoor temperature </li></ul><ul><li>Smaller birds usually breathe faster than larger birds </li></ul><ul><li>Birds in flight have a higher respiratory rate than nonflying birds </li></ul>
    74. 74. Thermoregulation <ul><li>Air in the lungs picks up heat from body tissues and blood and removes it from the body during the breathing process </li></ul><ul><li>Increased air flow over mouth, pharynx, bronchi, and air sacs increases cooling </li></ul><ul><ul><li>Achieved through panting or gular fluttering (rapid vibrations of upper throat patch) </li></ul></ul>
    75. 75. Thermoregulation <ul><li>Birds bathe or reduce activity level during warmest parts of the day </li></ul><ul><li>Some species defecate on their legs for evaporative cooling </li></ul><ul><li>Can adjust the positions of body feathers and posture to promote both heat loss and heat retention </li></ul><ul><li>Countercurrent heat exchange system limits heat loss through their bare legs </li></ul>
    76. 76. Urogenital System
    77. 77. Kidneys <ul><li>Located dorsally in slight depression formed at level of synsacrum </li></ul><ul><li>Elongated with three divisions; no renal pelvis </li></ul><ul><li>Three divisions subdivide into lobules containing nephrons </li></ul>
    78. 78. Ureters <ul><li>Surrounded by smooth muscle that helps squeeze urates from the kidney or inhibit their flow into the cloaca </li></ul><ul><li>Urine passes through ureters to urodeum of the cloaca </li></ul><ul><ul><li>Either moved upward to colon and ceca for further reabsorption of water or propelled outward through the vent </li></ul></ul>
    79. 79. Urine Composition <ul><li>Primary nitrogenous waste component is uric acid </li></ul><ul><li>Waste is eliminated as a paste with a small quantity of fecal material </li></ul><ul><li>Excreted product is called a mute </li></ul>
    80. 80. Reproductive System <ul><li>Reproduction is periodic </li></ul><ul><ul><li>Increasing daylight stimulates release of hormones that directly affect the reproductive process </li></ul></ul><ul><li>Reproductive organs larger on the left side of the body </li></ul><ul><ul><li>In females the right ovary is rudimentary and not even functional </li></ul></ul><ul><li>During nonbreeding season, gonads are relatively small </li></ul>
    81. 81. Copulation <ul><li>Copulation is achieved in one of two ways: </li></ul><ul><li>Grooved erectile penis is attached to the wall of the cloaca to help transfer sperm into the female's vagina </li></ul><ul><li>Sperm transfer occurs when the male and female bring their cloacae into close proximity </li></ul>
    82. 82. Oviduct <ul><li>Infundibulum : grabs ovum as it comes out of ovary </li></ul><ul><li>Magnum : secretes layers of albumin around egg </li></ul><ul><li>Isthmus : deposits keratin shell membrane </li></ul>
    83. 83. Oviduct <ul><li>Uterus : deposits watery albumin, a hard external shell, and pigmentation </li></ul><ul><ul><li>Large and muscular </li></ul></ul><ul><ul><li>Also called the shell gland </li></ul></ul><ul><li>Vagina : secretes mucus to assist in egg laying; can store sperm for several hours to several days </li></ul>
    84. 84. Clutch <ul><li>Number of eggs that a female lays and incubates </li></ul><ul><li>Varies among species </li></ul><ul><ul><li>Many species lay one egg per day </li></ul></ul><ul><ul><li>Some species lay eggs every other day </li></ul></ul><ul><ul><li>Some larger species may lay at 4- to 5-day intervals </li></ul></ul>
    85. 85. Clutch <ul><li>Total number of eggs that a female can lay varies with the species </li></ul><ul><li>Determinate layers : specific number of follicles that develop </li></ul><ul><li>Indeterminate layers : can produce more eggs than their normal clutch size </li></ul><ul><ul><li>Continue to lay eggs if their eggs disappear </li></ul></ul>
    86. 86. Incubation <ul><li>Average incubation temperature for many species is 35° C </li></ul><ul><li>Prolactin promotes broodiness (incubation behavior) </li></ul><ul><li>Hormones also stimulate development of a “brood patch” </li></ul><ul><ul><li>Area of skin on the lower abdomen where heat is transferred to the egg </li></ul></ul><ul><li>Incubation time varies with the species </li></ul>
    87. 87. Hatching <ul><li>Involves powerful neck muscles and specialized egg tooth on the outside of a chick's bill </li></ul><ul><li>After hatching, neck muscles atrophy and egg tooth disappears </li></ul>
    88. 88. Chicks <ul><li>Newly hatched chicks differ in amount of feather cover, status of eyes, and degree of mobility </li></ul><ul><li>Altricial: hatched with eyes closed and skin bare </li></ul><ul><li>Semialtricial: covered with down, are immobile, eyes may be open or closed </li></ul><ul><li>Precocial: covered with downy feathers, eyes open, are mobile, leave the nest quickly </li></ul><ul><li>Semiprecocial: downy covering, eyes open, limited movement from the nest </li></ul>