Anatomy and physiology

image of Anatomy and physiology
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The integument is a complex organ which mediates between an organism and its environment. In birds, the most obvious roles of the skin are protection from harmful environmental influences and thermoregulation. This chapter advises on integument, musculoskeletal system, body cavity, digestive system, respiratory system, urogenital system, cardiovascular system, lymphatic system, endocrine system, nervous system and senses.

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5.1 Cross-section of a developing avian claw, displaying the distal phalanx encased in the heavily cornifying modified skin of the claw that thus forms the cornified claw capsule with wall (W) and solear (So) aspects. Also note the distal scutate scales and the digital pads. (Trichrome stain.)
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5.2 Plantar and medial view of the digits of a falcon. Note the opposed position of the first digit and the typically shaped claws, i.e. the talons or falculae. The dorsal aspect of the toes and tarsometatarsus is covered by scutate scales (ScS), while the side and plantar aspects are covered by small reticulate scales (RS). The metatarsal (MP) and digital (DP) pads feature prominent surface modifications that enable a better grasp. The claws comprise the hard (and in this case distinctly pointed) claw plate (CPl) and the softer claw sole (CS).
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5.3 Scanning electron micrographs displaying the structure of the feather vane of contour feathers. The rachis gives rise to the lateral branches (barbs, rami) that then ramify into proximal and distal barbules (radii). The proximal and distal barbules of adjacent barbs overlap and are stabilized by barbicles (hamuli). (© H. Bragulla)
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5.4 Feather types (European Goldfinch). From left to right: rectrix (tail feather), dorsal view; remex (flight feather), dorsal view; remex, ventral view; tectrix (contour feather), dorsal view; tectrix, ventral view; semiplume; plume.
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5.5 Mounted skeleton of the Eurasian Blackbird (lateral view). Note the ossified flexor tendon elements of the lower legs (arrow). Car = carina; Co = coracoid; F = furcula (fused clavicles); Fem = femur; Hum = humerus; Not = notarium; R = radius; Scap = scapula; Syns = synsacrum; TMt = tarsometarsus; TT = tibiotarsus; U = ulna.
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5.6 Schematic drawing of the wing, displaying primary and secondary flight feathers and the relevant musculoelastic elements of the wing (modified after ). 1 = propatagial tensor muscle; 2 = flexor carpi ulnaris muscle, and 3 = its elastic ligament; 4 = secondary extensor muscle; 5 = elastic inter-remigial ligament.
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5.7 Schematic drawing displaying insertion and action of the flight muscles (modified after ). The pectoral muscles (2) achieve downward movement of the wing, whereas the supracoracoid muscles (3) achieve lifting of the wing due to diversion of fibres via the triosseous foramen (1). H = humerus; C = coracoid; F = furcula (fused clavicles); St = sternum, with prominent carina.
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5.8 Schematic drawing of the body cavity. A = air sacs; L = liver.
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5.9 The gastrointestinal tract of a pigeon. Note the complex arrangement of the jejunoileum. C = crop; CR = colorectum; G = gizzard; P = proventriculus; Pa = pancreas within the duodenal loop.
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5.10 Pigeon dissection showing the prominent crop (C), the position of the heart (H) within the pericardium and the two liver lobes (L). T = trachea.
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5.11 Pigeon dissection showing the loops of the small intestines tilted cranially, thus revealing the course of the colorectum (CR), and the position of the testes (T) and the caudal division of the kidneys (K).
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5.12 Head of a falcon. Note the prominent cone or tubercle (arrowed) within the nostrils that acts as a baffle during high-speed flight. The bill displays the species-specific shape, with the characteristic ‘tomial tooth’ of the upper beak. The proximal part of the upper bill forms the yellow waxy membrane of the ceres.
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5.13 Pigeon dissection showing the syrinx. Note the trachea (T) and its bifurcation, and the dorsal position of the relatively small lungs (L). The specifically shaped tracheobronchial junction forms the syrinx (S).
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5.14 System of air sacs (modified after ). The right side displays opening of the major bronchi supplying the respective air sacs. The colours indicate functional grouping into caudal (blue) and cranial (green) compartments. 1 = unpaired clavicular air sac with axillary diverticle (1’) and the recess pneumatizing the humeral bone (1’’); 2 = cervical air sac with vertebral recesses (2’) pneumatizing the cervical vertebrae; 3 = cranial thoracic air sac; 4 = caudal thoracic air sac; 5 = abdominal air sac; L = lungs; Tr = trachea.
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5.15 Cross-section through avian lung. (Original magnification × 25; H&E.)
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5.16 Movement of air through the lung of a bird. Inspiratory movements increase air sac volumes and expiratory movements decrease them. The volume and shape of the lung remains the same. Because of the arrangement of the parabronchi and the possible presence of an aerodynamic valve, the air is moved unidirectionally through the parabronchi and therefore through the area of gaseous exchange. (© Nigel Harcourt-Brown)
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5.17 Pigeon dissection showing the position of the kidneys (K), the adjacent testes (T) and the ureter and the spermatic duct running towards the urodeum of the cloaca (C). L = lung
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5.18 Schematic drawing displaying the vascular system of the kidney (modified after ). The encircled areas show the localization of the renal valve that enables redirection of venous return. 1 = descending aorta and cranial vena cava; 2 = cranial portal vein; 3 = external iliac artery and vein; 4 = caudal portal vein; 5 = caudal renal vein; 6 = ischiadic artery and vein; 7 = internal iliac vein; 8 = median sacral artery and caudal mesenteric vein.
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5.19 Cross-section of the kidney at high magnification, displaying one lobule. (Original magnification × 50; H&E.)
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5.20 Schematic drawing of the female genital tract (modified after ).
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5.21 Dissected hindlimb of a falcon to show superficial and deep vascular structures, with associated nerves, on the medial aspect. 1 = external iliac artery and vein; 2 = ischiadic artery and vein; 3 = medial femoral vein. 1 = ischiadic artery and nerve; 2 = ischiadic vein; 3 = caudal tibial artery and lateral plantar nerve (tibialis nerve); 4 = cranial tibial artery and right profundus fibularis nerve. 1 = medial femoral vein; 2 = ischiadic vein; 3 = caudal tibial vein; 4 = superficial plantar metatarsal vein.
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5.22 Schematic drawing of the structures of the eye. (© Nigel Harcourt-Brown)

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