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20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
20. Amphibian and Reptilian Anatomy and Physiology
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20. Amphibian and Reptilian Anatomy and Physiology

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    • 1. Amphibian and Reptilian Anatomy and Physiology
    • 2. Learning Objectives
      • List the taxonomic orders in the classes Reptilia and Amphibia.
      • Define ectothermic and explain how ectothermic animals regulate their body temperatures.
      • List the unique features of the reptilian and amphibian integumentary systems.
      • Describe the process of ecdysis.
      • List the unique features of reptilian and amphibian vision and hearing.
      • List the components of the reptilian and amphibian heart and describe the flow of blood through the heart.
      • Describe the unique features of the reptilian and amphibian respiratory and gastrointestinal systems.
      • Describe the structure of the kidneys of reptiles and amphibians.
      • Describe the factors that determine the sex of offspring of reptiles and amphibians.
      • List the unique features of the musculoskeletal systems of reptiles and amphibians.
    • 3. Taxonomy
      • Class Reptilia - four orders:
        • Crocodylia (alligators and crocodiles)
        • Squamata (snakes and lizards)
        • Chelonian (turtles and tortoises)
        • Rhyncocephalia (tuataras)
    • 4. Taxonomy
      • Class Amphibia - three orders:
        • Gymnophiona (caecilians)
        • Anura (frogs and toads)
        • Caudata (salamanders and newts)
    • 5. Metabolism
      • Ectothermic animals are unable to generate body heat internally.
        • Body temperature depends on environmental temperature
      • Some reptiles can raise body temperatures via metabolic processes (e.g., muscular contractions)
      • Herptiles - maintain body temperatures via behavioral thermoregulation (e.g., postural changes)
    • 6. Ectothermy
      • Related to energy conservation
        • Animal regulates temperature depending on metabolic needs
        • Allows many herptiles to survive on very small amounts of food
      • Depends on access to temperatures within the preferred optimal temperature zone (POTZ)
        • POTZ: range of temperatures in which the animal can perform all necessary metabolic functions
    • 7. Reptile Integument
      • Keratinized skin
        • Alpha keratin - soft, flexible, found in interscalar skin
        • Beta keratin - rigid, found in scales
      • Limited subcutaneous space
    • 8. Reptile Integument
      • Dermis - dense connective tissue
        • Blood and lymph vessels, nerves, and chromatophores (pigment-containing cells)
        • Chromatophores allow some lizards to change skin color and pattern
        • Osteoderms: bony plates within dermis of some lizards and crocodilians
    • 9. Reptile Integument
      • Scales - formed by epidermal folds in most reptiles
        • Vary in size and shape
        • Brille (spectacle): modified scales that may cover eyes
      • Other epidermal structures may be present
        • Crests, tubercles, spines, and dewlaps
    • 10. Reptile Integument
      • Scale and scute nomenclature - aids in species identification and medical recording
    • 11. Ecdysis
      • Shedding of the skin
      • Occurs with growth and in response to skin injury
      • Process is controlled by thyroid gland
      • Shed in pieces or in one large piece
      • Shed skin: exuvia
    • 12. Ecdysis
      • Cells replicate new epidermis
      • Enzyme-containing lymph secreted between old and new epidermal layers
      • Skin color dulls; spectacle opacifies
      • Lymph - resorbed prior to ecdysis
      • Mechanical rubbing on objects
    • 13. Amphibian Integument
      • Epidermis - single or few layers of keratinized cells
        • Aquatic amphibians - no keratinized cells
      • Extremely permeable
        • Absorb water directly from environment
        • “ Drink patches”: areas of increased permeability on ventral surfaces
      • Dermis - chromatophores and glands
        • Glands produce secretions which help protect the amphibian’s skin
    • 14. Amphibian Integument
      • Toxic secretions - produced by some glands within dermis and epidermis
        • Defense mechanisms
      • Dermis: little subcutaneous space in salamanders and caecilians
        • Anurans: looser attachments of dermis (more subcutaneous space)
      • Amphibians regularly shed outer layers of epidermis
    • 15. Vision
      • Reptiles – iris made up of skeletal muscle under voluntary control
        • Pupillary light reflex: consensual reflexes usually not seen
      • Lower lid usually more mobile than upper
    • 16. Vision
      • Some species of lizards have thin, transparent lower lids
        • Allows for a degree of vision even when lids are closed
      • Cartilagenous pads (tarsal pads): found in lids of some reptiles
      • Nictitans: well-developed, mobile in many reptiles
    • 17. Vision
      • Snakes, some lizards - no true eyelids
        • Clear, fused scale (spectacle)
      • Tear film - between cornea and spectacle in subspectacular space
        • Tears drain into mouth through nasolacrimal duct system
    • 18.
      • Most reptiles - poorly developed extraocular muscles
        • Exception - chameleons; eyes move freely and independently of one another
      • Chelonians - no nasolacrimal ducts; tears spill over the lid margin
      Vision
    • 19. Vision
      • Lacrimal and harderian glands present in most reptiles and amphibians
        • Produce secretions that combine to form the tear film
      • Eyelids absent in some aquatic species
      • Caecilians - eyes covered with skin
      • Amphibian eyes - often protrude ventrally into the oral cavity when animal swallowing
    • 20. Vision
      • Ossicles: scleral bones present in most reptiles (except snakes and crocodilians)
      • Lens: more fluid in reptiles than mammals (more rigid in snakes)
      • Accommodation
        • Chelonians - lens is squeezed through the pupil
        • Snakes - lens moves back and forth due to pressure changes within the aqueous and vitreous humors
    • 21. Vision
      • Reptiles - avascular retinas
        • Nutrition and waste removal via choroidal vessels in vitreous
        • Conus papillaris: in lizards, extends into vitreous from optic disc
          • provides nutrition and waste removal
      • Crocodilians have a tapetum
      • Parietal eye - found in some reptiles
        • Rudimentary retina and cornea, no iris, lids, or musculature
        • Exact function unknown
        • May play a role in light-cycle-mediated hormone function
    • 22. Cardiovascular System
      • Location of the heart varies
      • Chelonians - on midline just caudal to thoracic girdle, ventral to the lungs
      • Most lizards - within thoracic girdle
      • Crocodilians and some lizards - farther back in the coelomic cavity
      • Snakes - usually at junction of the first and second third of the body length
        • Fairly mobile within the coelomic cavity
    • 23. Heart
      • Two atria
      • One ventricle
    • 24. Heart
      • Ventricle Regions
      • Cavum venosum: paired aortic arches, lead to systemic circulation
      • Cavum arteriosum: receives blood from pulmonary veins and directs oxygenated blood to cavum venosum
      • Cavum pulmonale: receives blood from right atrium and directs flow into pulmonary circulation
    • 25. Heart
      • Pressure differences of outflow tracts and muscular ridge that partially separates cavum venosum and cavum pulmonale maintain separation of oxygenated and deoxygenated blood
    • 26. Heart Rate
      • Depends on species, size, temperature, activity level, and metabolic function
      • Heart rate = 33.4 × (Weight in kg -0.25 )
      • Lizards - vasovagal reflex induces drop in heart rate, blood pressure, and a catatonic state
        • Triggered by applying gentle pressure to both eyeballs through closed lids
        • Lizard recovers with cessation of pressure or mild stimulation
    • 27. Blood Cells
      • Reptilian red blood cells: oval and nucleated
      • RBC life span between 600 and 800 days
      • Immature erythrocytes occasionally seen, especially in juveniles and during ecdysis
    • 28. Blood Cells
      • Heterophils: round with eosinophilic rod-shaped granules and round to oval nuclei
        • Analogous to mammalian neutrophils without peroxidase and acid phosphatase
        • Reptiles produce caseous pus instead of liquid material
      • Eosinophils: similar appearance to heterophils but granules are round
      • Basophils: small round cells with deeply basophilic cytoplasmic granules that may obscure the nucleus
    • 29. Blood Cells
      • Lymphocytes : vary in size; usually round cells with large nuclei, large nuclear-to-cytoplasm ratio, and no cytoplasmic granules
      • Monocytes: oval or lobed nuclei, blue-grey cytoplasm, may contain small vacuoles or very fine granules
        • Some reptile monocytes have small azurophilic granules (azurophils)
      • Thrombocytes: small, oval, nucleated cells; colorless cytoplasm may contain small granules
    • 30. Respiratory System
      • Reptiles capable of surviving long periods without breathing
        • Because of large pulmonary volume, reptiles have efficient anaerobic metabolism and cardiac shunting capabilities.
      • Respiration driven by oxygen levels in blood
    • 31. Respiratory System
      • Glottis of most amphibians and reptiles: rostral portion of oral cavity
      • Glottis very mobile in snakes; protrudes from mouth to allow respiration during ingestion of prey
      • Paired arytenoid cartilages: border glottal opening; open during respiration
    • 32. Respiratory System
      • No vocal cords
      • Only vocalizations possible are hissing, grunting, bellowing
      • Frogs and toads - vocal sacs arise from trachea
      • Glottal keel present in some species of snakes
        • Increases volume of vocalizations
    • 33. Pulmonary Tissues
      • Honeycomb appearance
      • Openings of honeycomb end at faveoli
        • Fixed structures surrounded by capillaries
        • Site of gas exchange
      • Tracheal rings incomplete (except chelonians)
    • 34. Reptile Lungs
      • Unicameral lung
        • Simple, saclike
        • Cranial portion: site of gas exchange
        • Caudal portion: avascular, comparable to avian air sac
    • 35. Reptile Lungs
      • Multicameral lung
        • Many compartments
        • Intrapulmonary bronchi
    • 36. Reptile Lungs
      • Paucicameral Lung
        • Characteristics of both unicameral and multicameral lungs
    • 37. Reptile Respiratory System
      • No true diaphragms
      • Action of intercostal muscles and parts of axial musculature used for respiration
    • 38. Reptile Respiratory System
      • Crocodilians - muscular septum caudal to lungs
        • Cranial aspect of liver is attached to septum
        • Caudal aspect of liver is attached to pubis by diaphramaticus muscle
        • Lung inflation results from contraction of diaphramaticus moving the septum caudally
    • 39. Amphibian Respiratory System
      • Simple saclike lungs
      • Some salamanders have no lungs
        • Cutaneous respiration
      • Pulmonary ventilation results from pumping of buccal cavity and pharynx
        • Gas exchange can also occur across mucous membranes of buccal cavity, pharynx, and cloaca
    • 40. Hearing
      • Ears - both sides of head, usually caudal to eyes
      • Tympanum - may lie in depression and/or be covered by folds of skin (some lizards and crocodilians)
      • Columella - single bone in middle ear of reptiles
        • Connects to tympanum and quadrate bone
        • Transmits vibrations to oval window of cochlea
        • Converted to nerve impulses and transmitted to the brain via the vestibulocochlear nerve
    • 41. Hearing
      • Semicircular canals control balance and equilibrium (reptiles)
      • Snakes - no external ears; columella articulates with quadrate bone
        • Allows snakes to be very sensitive to ground vibrations transmitted through the mandibles
        • Snakes also able to hear aerial sounds
      • Salamanders and caecilians - no tympanic membranes; columella may be degenerate
    • 42. Feeding Strategies
      • Carnivorous, omnivorous and herbivorous reptiles all exist
      • Snakes, crocodilians, and adult amphibians are strict carnivores
      • Some diets are very specialized
    • 43. Oral Cavity
      • Snakes and lizards: deeply forked tongues
        • Function as particle delivery system for vomeronasal organ (accessory olfactory organ)
        • Allow for detection of particle gradients
    • 44. Oral Cavity
      • Chameleons: specialized projectile tongues designed for capturing prey from long distances
        • Sticky end which the prey items stick to
      • Turtles and tortoises: typically thick, fleshy, relatively immobile tongues
    • 45. Oral Cavity
      • Crocodilians: immobile tongue attached to intermandibular space
        • Muscular flaps from base of tongue and dorsal pharynx allow for opening of mouth while submerged without ingesting or inhaling water
    • 46. Oral Cavity
      • Tongue used to capture prey (most amphibians)
      • Anurans, most terrestrial
      • salamanders: caudodorsal
      • aspect of tongue is flipped
      • cranioventral to prehend
      • food (lingual flipping)
    • 47. Oral Cavity
      • Numerous salivary glands
      • Salivary secretions provide lubrication that aids in ingestion of large prey
        • Also has enzymatic properties
      • Venom glands (some snakes, lizards) - modified salivary gland
    • 48. Dentition
      • Turtles and tortoises
      • No teeth
      • Tomia (keratinized beaks)
      • Other reptiles: 3 types of dentition
    • 49. Types of Dentition
      • Thecodont dentition: teeth arise from sockets in skull bones (crocodilians)
    • 50.
      • Pleurodont dentition: teeth attached to medial aspect of periosteum on mandibles and maxillae (snakes and iguanid lizards)
      Types of Dentition
    • 51. Types of Dentition
      • Acrodont dentition: teeth fused to biting edge of mandible and maxillae (some lizards)
    • 52. Dentition
      • Snakes have 6 rows of teeth: two mandibular, two maxillary, two on palantine/pterygoid bones
      • Aglyphous snakes lack fangs
    • 53. Dentition
      • Venomous snakes - specialized dentition for venom delivery
      • Proteroglyphous and opisthoglyphous - fangs are fixed upright
      • Solenoglyphous - fangs are folded on roof of mouth when mouth is closed and are erect when snake bites
    • 54. Dentition
      • Venom-delivering teeth: hollow with an opening near end where venom expelled
      • Fangs receive venom through a duct from venom gland at its base
      • Contraction of muscles around venom gland forces venom out through the fang
      • Snakes can control amount of venom delivered with each bite
    • 55. Dentition
      • Most amphibians have teeth
      • Caecilians and salamanders - both maxillary and mandibular teeth
        • Palatal teeth in some species
      • Maxillary dentition present in some anuran species
      • Odontoid process: cutting plates on rostral mandibles of some frogs
    • 56. Esophagus
      • Reptile - thin and distensible
        • Unique morphology reflects type of prey
      • Amphibian esophagus very short and wide, especially in anurans
    • 57. Stomach
      • Reptile - variable size and shape
        • Snakes - highly distensible
        • Crocodilians - thick muscle comparable to avian gizzard
      • Amphibian - anurans capable of prolapsing stomach through the mouth; gastric prolapse is a terminal event in dying animals
    • 58. Amphibian Intestinal Tract
      • Indistinct regions
      • Liver may contain melanomacrophages involved in immune function
      • Pancreas - between stomach and proximal segments of intestine
    • 59. Reptilian Intestinal Tract
      • Varies according to diet
        • Herbivores - longer intestinal tracts than carnivores
      • Snakes - relatively straight intestinal tracts
    • 60. Reptilian Intestinal Tract
      • Colon - large and complex in herbivores
        • Hindgut fermentation for digestion
      • Cecae - site of hindgut fermentation in herbivorous lizards and chelonians
      • Liver - usually large and bi-lobed
    • 61. Cloaca
      • Common outflow tract for GI and urogenital tracts (all reptiles and amphibians)
      • Three chambers: coprodeum, urodeum and proctodeum
    • 62. Reptile Kidney
      • Usually oblong and smooth-surfaced
      • Snakes - kidneys that are lobulated
      • Ureters empty into dorsolateral aspects of the urodeum
        • Some species do not have urinary bladders
    • 63. Reptile Kidney
      • No distinct renal pelvis
      • Distal collecting tubules join into collecting ducts that merge to form the ureter
      • No loop of Henle present
      • Not able to concentrate urine as mammals do
      • Water can be absorbed from urine through wall of the urinary bladder, rectum, or cloaca
    • 64. Amphibian Kidney
      • Nephrostomes - connect the coelomic cavity to the renal tubules; filter blood and coelomic fluid
      • Kidneys usually lobulated and in caudodorsal coelomic cavity
    • 65. Amphibian Kidney
      • Some amphibians excrete ammonia as a nitrogenous waste product; others excrete urea, some excrete uric acid
      • No ability to concentrate urine
      • Urinary bladders and cloacal anatomy similar to reptiles
    • 66. Reptile Reproductive System
      • Males have internal testes located in dorsal coelomic cavity
      • Ductus deferens leads from testes to dorsal wall of the urodeum
      • Most also have a sexual portion to the kidney tubules
        • Develops in response to high levels of circulating sex hormones
        • Probably provide secretions that contribute to the seminal fluid
    • 67. Reptile Reproductive System
      • Copulatory organs vary in structure
        • Crocodilians and chelonians - phallus of erectile tissue rising from
        • floor of cloaca
        • Snakes and lizards - paired hemipenes everted from the tail base through the vent
    • 68. Reptile Reproductive System
      • Females - paired ovaries in dorsal coelomic cavity
      • Paired oviducts lead to cloaca and end at genital papillae in dorsal wall of the urodeum
    • 69. Reptile Reproductive System
      • Oviducts - 5 regions: infundibulum, magnum, isthmus, uterus, and vagina
      • Albumin and shell - in oviparous species, added to ova in the oviduct prior to egg laying
      • In viviparous species, fetuses are retained in uterine portion of oviduct
    • 70. Reptile Reproductive Cycle
      • Vitellogenesis - development and maturation of the follicles
        • Triggered by environmental cues that stimulate release of FSH and estrogen
      • Vitellogenin - lipid substance added to yolk within developing follicle
        • Large amounts of calcium are also added
      • In viviparous reptiles - some support of fetus
        • Some lizards have true placentas
    • 71. Reptile Reproductive Cycle
      • Oviposition - many reptiles dig nests to lay eggs
        • Without suitable nesting material, female may experience dystocia
      • Chelonians and lizard species may excavate deep holes to deposit eggs
    • 72. Reptile Reproductive Cycle
      • After oviposition or parturition, reptiles not involved with care of eggs or offspring
        • Exceptions - crocodilians protect their nests and young for a period of time following hatching
        • Pythons and cobras - protect their nests until hatching
    • 73. Egg Incubation
      • Development and hatching requires proper temperature, humidity, and gas composition of nest
      • Incubation time and temperature varies
      • Reptile eggs should not be rotated during incubation
    • 74. Sex Determination in Reptiles
      • Determined by genotype or temperature at which eggs are incubated
      • Sex chromosomes:
        • Females are heterozygous (ZW) and males are homozygous (ZZ)
    • 75. Sex Determination in Reptiles
      • Some species do not have sex chromosomes
        • Higher incubation temperatures produce males in crocodilians and lizards
        • Opposite occurs in chelonians
        • Temperature range within the nest allows for production of a mixed clutch of hatchlings
    • 76. Secondary Sex Characteristics
      • Snakes - no real sexual dimorphism
      • In some species, pelvic spurs can be larger in males
        • Pelvic spurs: remnants of pelvic limbs; provide tactile stimulation to females
    • 77. Secondary Sex Characteristics
      • Male chelonians may have concave plastron and more distally located vent
        • Allows closer apposition of the cloacas when the male mounts the female
      • Some lizards show obvious dimorphism
        • Example: male Jackson’s chameleon has three well-developed horns on its face
    • 78. Amphibian Reproduction
      • Sexual dimorphism in some species
        • Poison dart frog males have enlarged toe pads
        • Large tympanic membranes in some male anurans
        • Prominent cloacal glands in male salamanders
    • 79. Amphibian Reproduction
      • Paired gonads in dorsocaudal coelomic cavity
      • Bidder’s organs - ovarian remnants near testes in male toads
      • Most caecilians are viviparous
      • Most anurans and salamanders are oviparous
      • Amplexus - Male frogs and toads fertilize eggs as they are laid while grasping the female
    • 80. Amphibian Reproduction
      • Phallodeum - portion of cloaca in caecilians that is everted to deposit semen into female’s cloaca
      • Spermatophores - packets of sperm deposited onto substrate by male salamanders
        • Picked up by the female salamander’s cloaca
        • Spermatotheca - pocket in cloaca of female salamanders where sperm can be stored
    • 81. Amphibian Reproduction
      • Eggs are usually deposited in or near water
      • Some parental care of eggs and/or young in anurans and most salamanders
      • Larval anurans (tadpoles) have completely aquatic lives prior to metamorphosis
      • Tadpole metamorphosis - usually complete within 90 days
        • Metamorphosis is stimulated by thyroid hormones
    • 82. Endocrine System
      • Single thyroid gland (except lizard)
        • Crocodilians - bilobed thyroid has a thin isthmus between lobes
      • Size of thyroid gland varies according to season and metabolic state
      • Parathyroid glands and ultimobrachial bodies in cervical region
    • 83. Endocrine System
      • Adrenal glands - usually within the ligaments that suspend the gonads
      • Produce epinephrine, norepinephrine, aldosterone, and corticosterone
      • No distinct separation of adrenal cortex and medulla
      • Exact location of endocrine organs in amphibians varies
    • 84. Reptile Nervous System
      • Three major divisions of reptilian brain
        • Forebrain - olfactory lobes, cerebral hemispheres, diencephalon
        • Midbrain - optic lobes, cerebral peduncles, nerve fibers connecting forebrain and hindbrain
        • Hindbrain - cerebellum, medulla oblongata
      • No surface gyri or sulci on the brain
    • 85. Reptile Nervous System
      • Brain meninges: pia-arachnoid layer and dura mater
      • 12 cranial nerves
      • Depend on spinal segmental reflexes and locomotor centers for control of movement
    • 86. Amphibian Nervous System
      • Brain - well developed for basic functions (sight, olfaction, and movement)
      • 10 cranial nerves
      • Spinal cord extends to the tip of the tail in amphibians and caecilians; ends in lumbar region in frogs and toads
      • Animal dependent upon spinal segmental reflexes to control movement
    • 87. Reptile Musculoskeletal System
      • Types of skulls
      • Anapsid: no temporal openings; chelonians
      • Diapsid: temporal openings in the skull
    • 88. Reptile Musculoskeletal System
      • Snake skulls -extremely mobile
      • Mandibular symphysis is connected by ligaments that allow jaws to move independently of each other
    • 89. Snake Skulls
      • Mandibular symphysis connected by ligaments allows jaws to move independently
      • Quadrate bones - allow wider opening of mouth
      • Moveable bones of maxillae and palate
    • 90. Reptile Musculoskeletal System
      • Spine - extremely flexible; presacral, sacral, and caudal-vertebral regions
      • Single occipital condyle forms the articulation between skull and spine
      • Well-developed ribs
        • Exceptions: chelonians’ spine and ribs are fused to the bony shell
    • 91. Amphibian Musculoskeletal System
      • Skulls of anurans - broad and fenestrated
      • Parts of the skull involved with olfaction and hearing are well developed
      • Palate - poorly developed with reduced dentition
      • Caecilians - compact, well-ossified skulls with well-developed dentition
    • 92. Amphibian Musculoskeletal System
      • Highly variable number of vertebrae
      • Vertebrae - no distinctions of regions
        • Salamanders and anurans also possess sacral vertebrae
      • Anurans’ vertebrae are fused
        • Urostyle - last caudal vertebra
      • Caecilians lack a sternum
      • Sternum is a small cartilaginous plate in salamanders
    • 93. Axial Skeleton
      • Tail autonomy - defensive mechanism
        • Some lizards and salamanders
        • Discarded tail usually continues to wiggle and distract predator
      • The species capable of tail autonomy have “fracture planes” along which tails break
        • Little to no blood loss
      • Lost tail can regenerate; regenerated tail stiff and cartilaginous
    • 94. Reptile Appendicular Skeleton
      • Pectoral girdle - scapula and coracoid bone with muscular attachments to the body
      • Pectoral limbs - humerus, radius, ulna, carpal bones, metacarpal bones, and phalanges
      • Pelvic limb - femur, tibia, tarsal and metatarsal bones, and the phalanges
        • Usually five digits on both front and rear feet
    • 95. Reptile Appendicular Skeleton
      • Spurs - vestigial pelvic limbs of some snake species
        • Found on either side of the vent
        • Used in courtship behavior
      • Some lizards have very reduced limbs
        • “ Legless lizards” retain vestigial thoracic and pelvic limb structures
    • 96. Amphibian Appendicular Skeleton
      • Pectoral girdle - primarily cartilaginous; consists of precoracoid, coracoid and scapula
        • Exception - anurans’ pectoral girdle is completely ossified and consists of scapula, clavicle, and coracoid
      • Pectoral limb - similar to reptile, except for radioulna (fused radius and ulna in anurans)
        • Four toes usually present on the pectoral limbs
      • Pelvic girdle - ilium, ischium and pubis
    • 97. Amphibian Appendicular Skeleton
      • Pelvic limb - elongated and well developed for swimming and jumping
        • Elongated metatarsal bones in anurans
        • Usually five toes are present
    • 98. Muscular Structure
      • In four-limbed amphibians and reptiles, musculature is somewhat analogous to that of mammals.
      • Snakes: epaxial muscles and segmental muscles

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