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2015-02-14 16:01:19

Lab Test 1
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  1. Directional terms
    • Anterior, posterior (caudal), dorsal, ventral
    • Lateral, Medial
    • Any pair of directional terms can be combined to form a new term.
  2. Planes of the body
    • Sagital-divides the body in left and right halves
    • Frontal-divides the body in top and bottom halves
    • Transverse (coronal)-divides the body in front and back halves
  3. Binomial Nomenclature
    Kingdom, Phylum, Class, Order, Family, Genus, Species
  4. Cladistic Terminology
    • One method of documenting Phylogeny
    • Clades: monophyletic vs. paraphyletic
    • Taxa
    • Characters: synapomorphies vs. plesiomorphies
    • Homoplasy
    • Nodes
    • Grades
    • Sister groups
    • Outgroups/Ingroups
    • Linnaean Heirarchy-older, begun by Linnaeus
  5. First Chordate
    • Pikaia
    • Cambrian period
    • Canada
    • 542 mya
    • no bone
    • Other chordates look even less like what you'd expect a chordate to look like.
  6. 3 main taxa (subphylums) in phylum chordata
    • Urochordata
    • Cephalochordata
    • Vertebrata
  7. What is a chordate?
    Any animal possessing the 5 main characters of chordates:  notochord, post anal tail, hollow dorsal nerve cord, pharangeal gill slits, endostyle or thyroid gland
  8. phylogeny vs. ontogeny
    • Phylogeny is the true ancestry of an animal or group, where as ontogeny is the growth series that an animal goes through.
    • Ontogeny recapitulates phylogeny
  9. Notochord
    • Stiffened rod to which the body muscles attach and act against.  Note that the blocks of striated muscle fibers are arranged in bands, called myotomes, which are along the sides of the animal.
    • The notochord is incompressible.  When the muscles on one side of the body contract they do not cause the animal to shorten in length, but bend the body.
    • The animal swims by making alternate contractions of the myotomes on the two sides of the body.
  10. Pharyngeal Slits
    • Used in feeding.  The pharynx wall is perforated by up to 200 vertical slits, separated by stiffening rods.
    • Rows of beating cilia cause a water current to flow in through the mouth, through the pharyngeal slits and out of the body through a hold in the body wall (atriopore).  Small particles in the water are trapped by the cilia in different parts of the mouth chamber and separated into edible and waste material.
    • Evolved into jaw/skull bones or gills in vertebrates.
  11. Endostyle
    • Thyroid gland
    • Endocrine functions (hormones), but in basal chordates, produces mucus on cilia which trap food particles and sweep them towards gut.
  12. Dorsal (hollow) Nerve Cord
    • Nerve cord is dorsal in the body, directly above the notochord.  It is hollow.
    • Made up of neurons that carry sensory/motor information to and from the head.
  13. Post-anal Tail
    The tail continues posterior to anal opening, differing from invertebrates which generally have their anus at the tip of tail.  May also provide more muscles for movement.
  14. Secondary characteristics
    • Bilateral symmetry (laterally)
    • Segmentation
    • Coelom-fluid filled interal body cavity
  15. Hemichordata
    • do not have all five chordate characteristics
    • Ex: Saccoglossus Acorn worm
    • Possess pharyngeal slits and nerve cord, but no other features of a chordate.
    • Closely related to echinoderms (starfish, urchins)
    • Characteristics:
    • Stomochord, Trunk dorsal nerve cord, Trunk ventral nerve, cord, Pharynx, Pharyngeal slits/clifts, Trunk coelom, Proboscis coelom, Trunk, Collar, Proboscis, and stalk, Branchial pore, Anal opening
  16. Urochordata
    • Tunicates "sea squirts"
    • All characters present in larva, 3 lost in adult (post-anal tail, notochord, and nerve cord) all used in locomotion
    • Be able to identify: sessile adults, and active juvenile larvae
    • Additional characters (Juveniles): Post-anal tail, notochord, Dorsal nerve cord, epidermis, tunic, adhesive papilla, branchial basket, pharyngeal slits, visceral ganglion, incurrent branchial siphon, cerebral ganglion, otolith, excurrent atrial siphon
    • Additional characteristics (adult); branchial basket, oral tentacle, incurrent siphon, cerebral ganglion, excurrent siphon, intestine, gonad, stomach, heart, stigmata, endostyle, tunic
  17. Cephalochordates
    • All five characters present
    • Fusiform body, but still a filter/suspension feeder
    • Amphioxus (or lancelets)
    • This is not a vertebrate, no bone
    • Additional lancet characters: Dorsal fin, notochord, myomeres, dorsal and tubular nerve cord, oral hood, paryngeal slit, midgut cecum, esophagus, wheel organ, hatschek's pit, pigment spot, midgut, iliocolic ring, atriopore, hindgut, ventral fin, anus, post-anal tail ocellus, velar tentacle, velum, buccal cirri
  18. Vertebrata
    • (Spinal column, not necessarily bone) boty taxa have lost bony elements phylogenetically
    • Spinal column provides support, muscle attachment, protects nerve cord
    • Agnathans=jawless
    • Myxini: hagfishes
    • Petromyzoniformes: lamprey (plus ammocetes larvae)
  19. Integuments
    • body coverings
    • skin, bone, hair, fur, scales, feathers, quills, horns, antlers, crests, baleen, armor
    • The integument is a body organ (the largest) and includes body coverings and associated glands.  It is complex, and consists of ectodermal epidermis and mesodermal dermis.  During development, neural crest ectoderm migrates through the space between ectoderm and mesoderm to produce such important structures as dermal bone and chromatophores.
  20. Integument functions
    First, it holds the animal together.  The skin forms a boundary between the animal and its environment, and thus helps to regulate what enters the vertebrate body.  Good things that might enter include heat, water, O2 and other small inorganic or organic nutrients.  Bad things are legion, and include ultraviolet radiation, pathogens, toxins, water, claws, and teeth.  The skin also regulates what exits the body, including water and CO2.
  21. Skin
    • The skin protection from predators traces back to the dermal skeleton of the earliest vertebrates and includes both tooth-like scales and bony plates.
    • In terrestral tetrapods (amniotes) the highly keratinized superficial skin layer resists water loss.  Keratinized skin allowed the evolution of two types of appendage that helped to maintain heat and thus, allow the evolution of endothermy.  These appendages are hair and feathers.
    • The skin, as part of the skeleton, transmits forces from muscles for behaviors like swimming in sharks and frowning in humans.  The skin of the fish fin expands for swimming while skin of the wings of bats expands for flight.
    • Chemical and structural skin features allow it to advertize reproductive cues to the opposite sex or warning signals to predators.
    • A composite structure: epidermis, basement membrane, dermis, hypodermis
  22. Epidermis
    • Superficial, multilayer epithelium with cells that synthesize keratin.
    • The epidermis usually has pores and glands that help moisten the skin.  In fishes and amphibians, the glands usually produce a thick mucus that helps to ensure laminar flow over the body and that has antibacterial properties.
    • In amphibians, the mucus also helps keep the skin from drying.
    • In terrestrial vertebrates, the epidermis usually forms a thickened outer layer.  This layer is made of the protein Keratin and is said to be cornified and is called the stratum corneum.  These roughened areas tend to be thicker in regions that experience a lot of contact like the sole of the foot and the fingers.
    • Some fish also developed keratinized tissues.  Examples include mudskippers, fish that pull themselves out onto land, and breeding minnows.  Many minnows around here develop breeding tubercles in the males that are keratinized structures that are often very long and are used for sparring.  The epidermis may also form folds that develop into really thick structures or epidermal scales.
  23. Basement membrane
    Material secreted by epidermis and dermis.
  24. Dermis
    • Deep layer of dense connective tissue (mostly collagen)
    • Dermis produces dermal bone through intramembranous ossification.  However, the dermis of vertebrates is largely collagen with the protein elastin woven in it.  This collagen sheath is one of the mosst significant parts for maintaining body shape.  In sharks, the strong coat keeps the skin from wrinkling when it bends. For a fast swimming fish, this is improtant because it removes wrinkles from the skin and alleviates surface distortion.
    • This improves swimming efficiency by smoothing water flow (=laminar flow).
    • In fishes and aquatic vertebrates, the elastic skin retains some of the energy from a bend in the body.  When the body bends it stretches the skin on one side, and when the fish wants to complete the next stroke, the stored energy in the skin snaps the body back to straight, requiring less energy.  Terrestrial vertebrates have collagen in their dermis, but it is not as orderly as that of fishes.  We can't take advantage of elastic recoil as well as we don't need to worry about wrinkles in our skin slowing us down.
  25. Hypodermis
    is a loose connective tissue between dermis and the deep muscle.  Human anatomists call this the superficial fascia.
  26. Fish Integuments (slide 11)
    • Skin or skin and scales
    • Lamprey and hagfish have lost scales/armor from ancestors.
  27. Dermal skin - primitive vertebrates and fishes
    Primitive extinct vertebrates present an array of dermal features including: odontodes, teeth, and dermal bone
  28. Odontodes
    tooth-like scales. These are dentine cones with a pulp cavity and covered with a hypermineralized tissue like enamel or enameloid, hypermineralized means that most of the extracellular matrix is mineral and not protein.  Bone has a much larger protein component than enamel. The chief protein is collagen.  The base is typically bony.
  29. Teeth
    similar to odontodes, except occuring in the mouth and pharynx.
  30. Dermal bone
    • develops in the dermis of the skin. The precursor is a sheet of dense connective tissue.
    • Dermal bones tend to be restricted to the face and anterior part of the braincase.
  31. Fish rays
    Fish fins are supported by bony rays=lepidotrichia, which are also dermal skeletal features but how these were derived (and if) from odontodes is unknown.
  32. Fish skin
    • skin: fish have thin skin compared to mammals. It contains an epidermis lacking dead cornified cells and dermis of connective tissue in varying densities.
    • The epidermis contains single-celled mucus-secreting glands which appear as clear circles in the epidermis. Some schooling fishes have alarm cells which secret a chemical signal to alert other fish. Also notice pigment cells in the dermis.
  33. Hagfish skin
    • note the row of ducts located ventrally along the body for the exit of mucous from the numerous slime glands.
    • Note the row of larger pores are the exits for water from the hagfish's gills.
    • Low power shows epidermis and dermis of skin and the skeletal muscle that surrounds slime gland.
  34. Lamprey skin
    • smooth and thin. Note spiracles - openings where gills are found.
    • Shows epidermis at far right with some unicellular mucous glands. Dermis is relatively thin compared to the hagfish. Far left shows some muscle tissue in cross section.
  35. Fish scale types
    • Placoid, cosmoid, ganoid, cycloid, ctenoid, bony armor, keratinized
    • The most obvious fish integument structures are scales.  The are of largely dermal origin. Primitively, they consist of a deep layer of lamellar bone, then a layer of vascular bone, i.e., bone containing with blood vessels, a layer of dentine, and then a layer of enamel. Enamel is ectodermal in origin. Enamel is the hardest material in the body. Dentine is always associated with enamel, but is a little softer.  the type of dentine in fish scales is called cosmine. Four of them involve this type of system. Two, the ganoid and cosmoid scale are similar to one another. The difference is that the ganoid scales lack a layer of dentine. Ganoid scales are found in primitive fishes such as the gar and the bichir while cosmoid scales are found in extinct sarcopterygians. The cycloid scale is derived from the ganoid scale. Cycloid scales lack everything but the lamellar bone layer and are water thin. Finally the ctenoid scales is derived from the cycloid scale with teeth on the poterior margin.
    • The cteni of ctenoid scales probably act in the same way.
    • In addition to scales, many fishes have evolved bony armor.
  36. Scale phylogeny
    Scales have evolved over time and are of major importance in classifying fishes. Most are deeply buried in the fish's epidermis, or outer skin layer, with only part of them showing.
  37. Cosmoid scales
    • Consist of two basal layers of bone, a layer of dentin like cosmine, and an outer layer of vitrodentine.
    • In order: Enamel, dentin (cosmine), vascular bone, lamellar bone
    • Cosmoid scales are found in extinct sarcopterygians and extant cossopterygians. Cosmoid scales are similar to placoid scales and probably evolved from the fusion of placoid scales. As the fish grows each scale becomes larger as new bone is adde to basal layers.
  38. Placoid scales
    • Sharks/rays/chimeras have the fifth type of scale, called a placoid scale. The placoid scale appears to have evolved independently from the cosmoid-based scale types.
    • The placoid scale is essentially a tooth; it has a surface layer of enamel, an inner layer of dentine, and inside is a pulp cavity. They are almost always tiny except for the modified scales on the tails of rays and the spines often found in front of the dorsal fin. They probably act to reduce frictional drag.
  39. Ganoid scales
    • Enamel (ganoid), vascular bone, then lamellar bone. No dentin layer in these scales.
    • In order: enamel (ganoin), vascular bone, lamellar bone
    • This kind of scale is an evolutionary reflection of the time when fishes had armor plating to protect themselves. Ganoid scales are hard and smooth, and may take the form of only a few scales (or scutes, as in the sturgeon and stickleback), partial plating, or overall body plating. Sturgeons, gars, and sticklebacks have ganoid scales (or scutes).
  40. Cycloid scales
    • ONly have lamellar bone with connective tissue. Material deposited in circular pattern - see growth rings.
    • in order: Lamellar bone
    • Many fishes with which we are most familiar have cycloid scales, which are the thin, round, almost transparent scales. These scales are mostly buried in the epidermis, allowing only the small posterior margin to show.
  41. Growth of scales
    The image of fish scales, like a tree, shows rings that indicate periods of growth. Rings that are farther apart occur when the fish grows well and there is lots of food - in the summer season. Rings that are close together occur when the fish does not get much food and grows slowly. On the scale you can identify the summer growth and the winter growth. (there will be several rings in each). The core represents the fish when it was first born, as a fry. The rings near the edge are the most recent periods of growth.
  42. Ctenoid scales
    • Only have lamellar bone with connective tissue. Material deposited in horseshoe pattern.
    • In order: lamellar bone
    • Ctenoid (TEEN-oyd) scales, are much like cycloid scales except that they have tiny, comb-like projections (ctenii) on their posterior edges (the edges that show, and are not buried in skin). The colors of brightly colored fishes also show on these posterior edges.
  43. Tetrapod skin
    • The first tetrapods developed a novel feature in the epidermis, the stratum corneum, which is the most superficial layer of the epidermis and is characterized by cells that are filled with keratin and that secrete hydrophobic lipids. This layer is thin in amphibians but is much thicker in amniotes.
    • This creates a tough, largely impermeable barrier to water, which was important for becoming fully terrestrial.
  44. Amphibian integument
    • skin (most prevalent in extant taxa)
    • scales
    • Keratinized patches
    • Bony Armor
    • Early amphibians had dermal scales like their fish ancestors. The skin of amphibians is very important because most use the skin for at least part of their respiration. Dermal scales are found in some caecillians, but their homologies are unclear. Caecillians may have re-evolved scales.
    • Skin thin, membranous for gas exchange, less in toads.
    • Mucous glands, fungicidal secretions, poison glands, etc.
    • few extant have scale remnants
  45. Tetrapod integument
    Reptiles evolved an epidermal scale with cells supported by two types of keratin (alpha and beta). Beta keratin is a synapomorphy of reptiles and is not found in toher vertebrates. The cornified superficial layer has the bets keratin while the softer, deep layer has the alpha keratin. The soft layer provides a hinge that allows the harder outer layer to overlap with neighboring scales.
  46. Reptilian scales
    • These scales are distincly different than fish scales because they are made of keratin rather than bone and are epidermal rather than dermal. Reptiles usually have at least some dermal bone throughout their bodies, that is not in the head. In particular, there are the gastralia or gastirc ribs and usually small bones called osteoderms. Some of the plates on turtles are osteoderms and crocodile shave a small osteoderm in the eyelid. Reptiles shed the outer cornified layer as they grow.
    • Reptilian skin, with its waterproof scales, is one of the features of reptiles that makes life on land possible. The scales form a continuous barrier to evaporation. The bodies of reptiles are not wet and slimy like the bodies of fish or amphibians. Reptile skin is dry because reptiles have no skin glands.
    • Reptiles scales are epidermal scales, arising from the skin. Like feathers, scales are composed of the protein keratin, which is light, flexible, and strong, like the keratin that makes up fingernails.
    • Reptiles actually have two kinds of scales - one type more typical of snakes and lizards and the other of crocodiles and turtles. These are different both in their arrangement over the animal's body and in the way they develop.
    • Scales develop as a projection from the skin, skin has two layers, called the epidermis and the dermis. The epidermis is the top layer.
    • In snakes and lizards, a scale typically, into which part of the dermis projects. See the diagram on the left. As the scale continues to develop, the upper layer of the epidermis becomes hardened with the protein keratin, and the dermis withdraws, leaving a series of tough overlapping scales.
  47. Reptilian non-lepidosaur scales
    In turtles and crocodiles, most scales do not overlap. In these animals, scales begin as local thickening in the epidermis. Bony plates may also develop in the dermis under the scales. These plates do not necessarily form in the same pattern as the scales above them.
  48. Bird scales
    • Birds, which are archosaurs like crocodiles, ahve epidermal scales on their legs and feet.
    • Have feathers covering the rest of the body.
  49. Feathers
    • found on birds and some extinct dinosaurs.
    • Feathers are derived from reptilian scales, but we are not really sure how they formed. There are serveral types of feathers including flight, bristle, semiplume, down, contour, and filoplumes.
  50. Feather adaptations
    • Flight, pigmentation, insulation, waterproofing
    • Flight feathers are asymetrical, that is the rachis lies to one side. The barbs are then locked together by barbules to make the feather a seemingly solid structure. When a bird pulls its flight feathers through its beak, it is locking the barbules back together like a siplock bag. The reason for the asymetry is so that the feather rotates when the wing moves. When the wing moves down, he feathers twist so that they all lock together into a single solid surface. When the wing moves up, the feathers rotate away from one another and let air pass through.
  51. Feathers
    epidermal structures with a follicle, which is a part of the epidermis that has invaginated into the dermis and provides a protective house for the germinal layer of cells (the cells differentiating into the feather). This geometry also creates a structure that develops deep and is pushed superficially, out of the body, as it grows.
  52. Pterosaur hair?!?
    • There is evidence that the first flying archosaurs, the Pterosaurs, were warmblooded, which implies that they would have needed insulation.
    • Several debatable fossils show what looks like a hairy covering.
    • If true, this "hairy" covering may not be similar to mammalian hair.
  53. Mammal hair evolution
    Hair may have evolved in two ways. As surface insulation from the reptilian scales or as small, sensory hairs between successive hairs. In modern mammals hair serves both as insulation and as a sensory structure. There is some evidence that Therapsid reptiles had hair, but this is contentious. Most modern mammals develop long, thick hairs on the head called vibrissae or whiskers. These vibrissae are associated with pits on the skull. In some therapsids, there are tiny pits on the skull which may have been from vibrissae. Unfortunately, some lizards have similar pits and they lack hair. There is a very good skin imprint of a therapsid from the upper Permina that shows no evidence of hair or scales. Given that mammals evolved late in the Triassic around 230 mya, it is still possible that hair evolved prior to mammals, but we are still waiting for the fossil evidence.
  54. Hair structure
    • Several types
    • Serve same purpose as feathers, but also has different glands (eg. sweat and mammary)
    • Like feathers, hair develops from a follicle, so it grows out of the body from dermal layer, not epidermal.
  55. Claws, nails and hooves
    • Epidermal derivatives in all known tetrapods (earliest amphibians)
    • Cornified epithelium (keratin) grows outward from proliferating matrix cells in base.
  56. Horns
    • Characterized by bony core. Covered by keratin sheath that enlarges it considerably and makes it sharper.
    • found in all known tetrapods.
  57. Antlers
    found in Cervidae, mammals only, characterized by being deciduous, bony core, vascular skin (velvet) covers bone that has abcission (breaking point).
  58. Baleen
    • keratinized plates evolved in whales (Balaenopteridae family), for catching small food.
    • Around 30mya
    • Evolved from gummy, hard keratinized outgrowths of upper jaw.
  59. connective tissue
    • Loose connective tissue
    • dense connective tissue
    • blood - white blood cells, red blood cells, platlets
    • lymph cartilate
    • bone
  60. Losse connective tissue
    • Mesenchyme - unspecialized tissue
    • Areolar - around organs and in dermis
    • Reticular - found within certain organs and bone marrow, provides structure
    • Adipose - fat
  61. Dense connective tissue
    • Regular dense: tendons, ligaments
    • Irregular dense: resists forces, found in dermis
    • Elastic tissue: Elastic ligaments found between vertebrae
  62. Ligaments
    • connect bone to bone
    • generally found across joints where two bones meet or articulate.
    • Composed mainly of long, stringy collagen fibers that form tough fibrous bands.
    • Some ligaments limit the mobility of articulations, or prevent certain movements altogether, e.g., cruciate ligaments
  63. Tendons
    • Connect muscles to bones
    • made of tough fibrous bonds of collagen.
    • They can be flat or round in shape but able to glide freely to ensure easy movement.
  64. Cartilage
    • created by chondrocytes
    • Has few blood vessels=heals slowly or not at all.
    • 3 types - all distinguished by amount of collagen fibers
    • hyaline, fibrous, and elastic
  65. Hyaline cartilage
    • Most common
    • Moderate amounts of collagen fibers, but can not view with naked eye.
    • Found on surface fo smooth, gliding joints.
    • Endochrondral, or developing, bones start out as this ossify.
  66. Fibrous
    • Fibrocartilage
    • Many collagen fibers which can be seen more easily.
    • Fibers give strength in weight-bearing areas and shock points between joints (eg. Vertebra)
  67. Elastic Cartilage
    • Many fibers of protein elastin.
    • Can hold shape after stretching/deformation - not very strong
    • Ears, noses, and larynx
  68. Bone
    • Rigid living organs that are growing, highly vascularized connective tissue.
    • Functions are mainly support, protection, and shock absorbance for the body.
    • Thin superficial membranous tissue (periosteum) articulates with ligaments.
  69. functions of bones
    • They also protect the delicate internal organs.
    • -skull protects the brain and eyes.
    • -Sternum and ribs protect the heart and lungs.
    • Other bones provide support and locomotion.
    • -i.e. legs, tail and neck
    • Bones in the ear provide sound transmission.
    • -helps the dog to hear.
  70. bone tissue
    • cortical, or compact bone, makes up around 80% of total bone mass, and is most abundant in the shafts of long bones.
    • It has a high mineral content, ~70%
    • -calcium salts
    • -Phosphorus
  71. Cortical (compact) bone
    • Cortical bone tissue is made up of cylindrical units called osteons, that have a well defined longitudinal arrangement.
    • At the center of each osteon is a Haversian canal.
    • -This structure contains blood vessels and nerves. It is also surrounded by many layers of bone, described as lamellae.
  72. Cancellous (spongy) bone
    • Mostly in interior of bones.
    • Light and airy in structure and has spaces for storage/growth of marrow for red blood cell production.
    • Still rigid and strong.
  73. Trabeculae
    • also spongy bone
    • Trabeculae are reinforced bone columns.
    • -present in bone interior where strength is needed.
    • -Saves materials, imparts lightness, but still strong.
  74. Osteology
    study of bones
  75. Appendicular skeleton
    portion of the skeletal system includes bones contained in the limbs (appendages) of the animal.
  76. Axial skeleton
    bones of the skull, spine, ribs and sternum. The axial portion of the skeletal system is located along the longitudinal axis of the animal.
  77. Visceral skeleton
    Bones formed in soft organs. Examples are the middle ear ossicles and derivatives of the gill arch. They are not present in all species of animals.
  78. long bones
    • Length is greater than the diameter.
    • -found in the appdendicular skeleton, in the limbs, consisting of a diaphysis, metaphysis and two sections of epiphysis.
  79. Short bones
    approximately equivalent dimensions found in the carpals, metacarpals, tarsals, metatarsals.
  80. Flat bones
    • Scapula and many bones in the skull.
    • They surround and protect the eye, ear, sinuses, and brain.
    • They are found in the pelvis where they provide for the attachment of muscles and long bones.
  81. Irregular bones
    short and multiple bones e.g. vertebrae and all bones of the skull that are not of the flat type, and three parts of the hip bone.
  82. Sesamoid bones
    Small bones within tendons e.g. knee cap (patella). Small cuboidal shaped bones associated with tendons and ligaments. These bone reduce wear and tear on the tendons and as they pass over a articulation or prominence.
  83. Articular surface
    a joint surface
  84. Condyle
    a large rounded articular surface
  85. Bone Head
    the rounded proximal articular surface of many long bones - united to shaft by "neck"
  86. Facet
    a flat articular surface
  87. Processes
    • lumps and bumps on bones
    • ex: tuber, tubercle, tuberosity, trochanter
  88. Fossa
    a depressed area on a bone
  89. Foramen
    a hole in a bone
  90. Enamel
    hard outer covering - one of the hardest organic substances that keeps charp edges, prevents/slows wear
  91. Dentin
    Softer than enamel, harder than bone, underneath enamel and makes up most of mass of tooth - neither enamel or dentin have much of a bascular supply
  92. Pulp cavity
    • mucous connective tissue underneath dentin.
    • connects to root canal supplies blood and nerves.
  93. Cusp
    • Ridge, or raised structure on tooth surface.
    • -evolve quickly in response to changing food requirements.
    • -allow identification of many vertebrates, especially mammals.
    • All cusps have separate names; some are unique to taxa, others occur broadly.
  94. Alveolus
    tooth socket for organisms that have teeth imbeded in the dentary bone.
  95. Occlusal
    Biting surface; contact surface with other teeth or food item.
  96. Lingual
    surface facing the tongue
  97. Vestibular
    surface of anterior teeth facing the buccal mucosa (cheek).
  98. Homodont
    • teeth all have same structuer and size.
    • found commonly in amphibians (Necturus), fish (Squalus)
  99. Heterodont
    • Teeth have differetn structures and/or sizes for different functions.
    • Common in mammals (Felis).
  100. Polyphyodont
    • Teeth are replaced continuously until death.
    • All vertebrates, with few exceptions.
    • -mammals
  101. Diphyodont
    • Teeth only replaced twice during lifetime (deciduous)
    • -most mammals display this: primary or milk teeth, adult/permanent dentition.
  102. Hypsodont teeth
    • Teeth that keep growing after eruption.
    • -also known as 'high crown' teeth because of the height of the enamel above the gum line.
    • Found in most herbivores.
  103. Brachydont teeth
    • Teeth stop growing after eruption.
    • 'Low crown' teeth, found closer to the gum line.
    • Found mainly in carnivores and omnivores.
  104. Incisors
    They are rooted in the upper jaw (in the premaxilla). In placentals, incisors never number more than 3 in each quadrant. They are genearlly chiselshaped and usually function in nipping, as in a human biting an apple.
  105. Canines
    In the upper jaw, they are the first teeth rooted in the maxillae. They are long and usually unicusped. Canines function in the piercing and stabbing of food and (as in the Walrus) may vary tremendously in length.
  106. Premolars
    situated behind the canines, they differ from molars in that they are preceded by deciduous milk teeth and often have a simpler cusp pattern. Because premolars are so similar in function to molars, the two are often grouped as "cheek teeth" (CT).
  107. Molars
    The last teeth in the jaw, and generally having the greatest surface area, molars usually function in crushing. In herbivores, molar cusp patterns is often complex (for grinding). In carnivores, molars have a shearing function and have blade-like cusps, eg. carnassials.
  108. Carnassials
    Specialized teeth of carnivores found at the last upper premolar and first lower molar.
  109. Tooth formula (mammals)
    • Dental formula lists the number of each tooth type (incisors, canines, premolars, molars) in one half of the mouth.
    • Each upper number in the formula refers to the number of teeth of each type in one quadrant of the upper jaw, and each lower number refers to the number of teeth of each type in one quadrant of the lower jaw.
    • Individual teeth are referred to by a letter and number: a superscript denotes a tooth in the upper jaw, a subscript denotes a tooth in the lower jaw.