Exam 2 - skeletal system

skeletal system

• support

• protection : cranium, vertebrae, ribs of thoracic cavity and upper

• production of erythrocytes and immune cells within the marrow

• storage of minerals

• movement

dermal bone

develops within dermis, formed via intramembraneous ossification

endochondral bone

develops within hyaline cartilage precursor model, formed via endochondral ossification

bone classification

dermal and endochondral bone

• first bone originated and evolved from dermal armor of ostracoderms

intramembraneous ossification

• no cartilaginous precursor

• osteoprogenitor cells accumulate within the dermis

• become osteoblasts and begin to produce osteoid which is then enriched with calcium salts to form trabeculae

• osteoblasts trapped in the new bone become osteocytes

• spaces between the trabeculae contain hemopoietic tissue

endochondral ossification

• bone develops within hyaline cartilage model

• long bone consists of a diaphysis and 2 epiphyses

• metaphysics contains epiphyseal plate which is a region of active bone growth

• medullary cavity contains hemopoietic tissue

• periosteum is a vascularized connective tissue is covering of bones which connects to tendons and ligaments and anchors blood vessels and nerves

• bone deposition under periosteum increases girth of long bones

• in mammals epiphyses from secondary ossification centers but epiphyseal plates remain cartilaginous to allow for lengthening of bone until adult

• bones of fishes amphibians and most reptiles continue to grow throughout life

diarthrosis synovial joint

• most common, most movable type of joint

synovial cavity

space between bones and filled with synovial fluid

articular capsule

fibrous connective tissue capsule, surrounds joints, unites articulating bones, outer layer associated with ligaments, inner layer produces fluid

articular cartilage

ends of bones of joint covered hyaline cartilage during movement

bursa

fluid filled sac filled with synovial fluid produced by synovial membrane, provides cushion, reduces friction between bones and tendon

synarthrosis joints

• joints with limited movement but room for growth

• sutures where 2 dermal bones articulate

chondrocranium

endochondral bone, supports brain and sense organs, envelopes brain in chondrichthyans

• supports brain and sense organs

• endochondral bone in vertebrates other than chondrichthyans

• during development, cartilage forms under brain and next to notochord

• trabeculae form and develop into ethmoid plate

• parachordals form and develop into basal plate

• occipital cartilages form the occipital arch creating the foramen magnum

• sensory capsules include nasal, optic, otic

• chondrocranium envelops entire brain in chondrichthyans and does not ossify

• reduced to floor of skull in most vertebraes

splanchnocranium

endochondral bone, forms pharyngeal arches and derivitives

• pharyngeal arches support gills and contribute to formation of jaws in gnathostomes

• endochondral bone in vertebrae other than chondrichthyans

dermatocranium

dermal bone, many superficial bones of head, absent in chondrichthyans

• bondy dermal plates that encases much of chondrocranium and splanchnocranium elements

• protects brain and gills

• dermal bone

pharyngeal arches

• form mandibular, hyoid, and branchial arches, pharyngeal slits retained between the arches

• 7 arches grpw to support developing pharyngeal pouches during embryonic development

• in gnathostomes, 7 pharyngeal arches are apparent

• each pharyngeal arch separated by a slit

• spiracle is modified pharyngeal slit between the mandibular and hyoid arches

branchial arches

3-7 unmodified pharyngeal arches

• each branchial arch consists of 4 pairs of cartilage elements, united by single basibrachial cartilage

mandibular arch

1 modified pharyngeal arch

• pair of upper palatoquadrates and lower meckels cartilages

hyoid arch

2 modified pharyngeal arch

• reduced pair of hyomandibula and ceratohyal cartilage and single basihyal cartilage, supports mandibular arch

splanchnocranium homologies

• hyomandibular cartilage in sharks - hyomandibula in bony fishes - columella in amphibians, reptiles, birds - stapes in mammals

• quadrate process of platoquadrate in sharks - quadrate in bony fishes, ampibians, reptiles, birds - incus in mammals

• meckles cartilage in sharks - articular in bony fishes, amphibians, reptiles, birds - malleus in mammals

• portions of ceratohyal, basihyal, and branchial arches 1, 2 in sharks and bony fishes - hyoid in amphibians, reptiles, birds, mammals

• portions of ceratohyal, basihyal, and branchial arches 2, 3 in sharks and bony fishes - cartilaginous elements of the larynx in amphibians, reptiles, birds, mammals

• branchial arches 4, 5 in sharks - branchial 4 in bony fishes - not present in amphibians, reptiles, birds, mammals

palatoquadrate palatal region

homologous with the epipterygoid in bony fishes, amphibians, reptiles, birds, and alisphenoid in mammals

hyoid apparatus

• portions of ceratohyal, basihyal, and branchial arches 1, 2 in sharks and bony fishes are homologous with the hyoid apparatus in amphibians, reptiles, birds, mammals

• supports tongue musculature

larynx cartilaginous elements

• portions of ceratohyal, basihyal, and branchial arches 2, 3 in sharks are homologous with the cartilaginous elements of the larynx in amphibians, reptiles, birds, mammals

evolutions of jaw articulation and suspension : agnathans

• no jaws

• palaeostyly : no gill arches attach to braincase

evolution of jaw articulation and suspension : placoderms and acanthodians

• articulation between cartilaginous palatoquadrate and meckles cartilage

• euautostyly : mandibular arch suspended from brain case without help of hyoid arch

evolution of jaw articulation and suspension : primitive sharks

• articulation between cartilaginous palatoquadrate and meckles cartilage

• amphistyly : mandibular arch attached to brain case and hyoid arch

evolution of jaw articulation and suspension : modern sharks

• articulation between cartilaginous palatoquadrate and meckles cartilage

• hyostyly : mandibular arch suspended from brain case and hyoid arch

evolution of jaw articulation and suspension : bony fishes

• articulation between quadrate bone and articular bone

• modified hyostyly : mandibular arch reduced to region of articulation and lower jaw suspened by the hyomandibula via dermally derived symplectic bone

• teeth restricted to dermal derived bones

evolution of jaw articulation and suspension : amphibians, reptiles, birds

• articulation between quadrate bone and articular bone

• metaautostyly : mandibular arch reduced to region of jaw articulation

• hyomandibula is now columella

• teeth resticted to dermally derived bones

evolution of jaw articulation and suspension : mammals

• articulation between dentary bone and temporal bone

• craniostyly : jaws are entirely dermal bone, upper jaw fused to braincase and lower jaw suspended from temporal bone

dermal bone facial series

forms snout and encircles nares

• includes maxilla, pre maxilla, nasals

dermal bone orbital series

encircles eye and defines orbit

• includes lacrimal, postorbital, jugal

dermal bone temporal series

behind orbit and forma lateral aspect of braincase

• includes temporal bones, quadratojugal, squamosal

• temporal bone is a composite bone

• petrous regoin and mastoid, ear ossicles and styloid process, squamosal region and tympanic regoin

• all fused into temporal bone in humans

dermal bone vault series

roof of skull

• includes frontal, parietal, post parietal

dermal bone palatal series

roof of oral cavity

• includes pterygoids, vomer, palatine, parasphenoid

• all may be dentigerous

sphenoid

• composite bone

• sphenoid body, greater wing, pterygoid plates

• all fused into sphenoid bone in humans

primary plate

roof of oral cavity in fishes and amphibians formed by ventral skull bones

secondary plate

• function - suckling and breathing

• reptiles and mammals, extension of pre maxilla, maxilla, palatine, and pterygoids grow midline forming secondary plate

• separates nasal passages form mouth

• incomplete in most reptiles forming deep groove that channels air to the pharynx

• completee secondary palate in crocodiles and mammals forming nasal chamber

cleft palate

2 halves didnt fuse leaving a gap

incisive bone

• in many other species the incisive foramen allows for passage of ducts to the vomeronasal organ

conchae

• scroll shaped bony elements that increase the surface area of these cavities

• inferior concha - independent bone

• middle concha - part of ethmoid

• superior conchae - part of ethmoid

dermal bone mandibular series

encases meckles cartilage

• includes denture, angular, surangular, prearticular

• only the denture forms the lower jaw in mammals

• meckles groove is a medial opening on mandible exposing meckelian cartilage

• in all tetrapods the meckles cartilage ossifies at the proximal end of the jaw and becomes the articular bone in amphibians, reptiles, birds, and the malleus in mammals

• 18 week old human fetus with meckles cartilage exposed

dermatocranium evolution within amniotes

• temporal bar separates supra temporal fenestra from infra temporal fenestra

• euryapsids have supra temporal fenestra only

homodont dentition

teeth have similar morphology along jaw margin

heterodont dentition

teeth differ in morphology along jaw margin

theocodont tooth attachment

set in sockets

acrodont tooth attachment

attached loosely to top of jaw without sockets

• acrodont teeth may be found on multiple bones in bony fishes

pleurodont tooth attachment

attached to inner surface of jaw

tooth attachment

• moray eel has large sharp fang-like teeth along jaw margin

• pharyngeal jaws also possess teeth

• during feeding pharyngeal jaws grasp prey and transport it into pharynx

• anurans have pedicellate teeth with pleurodont tooth attachment

• reptiles and mammals have thecodont tooth attachment

mammalian tooth morphology

• crown, above gingiva

• root, fits into bone socket

• enamel, hardest substance in body, surface of the crown

• dentine, calcareous tissue, major portion of tooth, surrounds pulp cavity

• pulp, connective tissue in pulp cavity and root canal, supports vasculature and nerves that enter via apical foramen

• cementum, rests on dentine, grows in layers on the root surface

• periodontal ligament, collagenous fibers connecting cementum of root to bone

mammalian tooth development

• dental lamina grows into dermis

• underlying dermal papilla pushes into and interacts with the dental lamina forming tooth bud

• cells at periphery of dermal papilla form layer of odontoblasts, deposit dentine as they move towards center of developing tooth bud

• epithelial tissue of dental lamina forms an enamel organ

• remainder of papillae forms vasculature and nerves of pulp cavity

• root devlops shortly before eruption

• cementocytes form cementum anchoring tooth socket

mammal dentition

• most diphyodont

• deciduous and permanent set

• heterodonty : incisors, canines, premolars, and molars

• marine mammals reverted by to homodont dentition

incisors

• horizontal cutting edge

• well developed in herbivores

• rodents, single pair, chisel like, enamel only on anterior surface, grow throughout life

• sloths lack incisors

• elephant tusks

canines

• spear like in carnivores

• missing in lagomorphs and rodents forming diastema

• walrus tusks

• male narwhal, single extremely long tusk projects from left side of upper jaw, through lip, forms left handed helix

cheek teeth

• premolars, most are bicuspids, missing in rodents and absent in human infant

• molars, tricuspids, human permanent molars do not have any teeth preceding them

• cheek teeth of carnivores adapted for tearing felsh, ungulates adaptedb for macerating vegetation

mammalian crown heights

• brachydont, low crowns

• hypsodont, high crowns

mammalian cusp shape

• bunodont, rounded cusps

• lophodont, cusps form ridges

• selenodont, cusps crescent shaped

post cranial skeleton

• includes axial skeleton and appendicular skeleton

• protection, support, locomotion

human post cranial axial skeleton

• consists of the vertebral column, ribs and sternum

vertebrae post cranial axial skeleton

• vertebrae typically consists of a centrum and a neural arch that protects the spinal cord

• processes provide muscle attachment

• in humans superior and inferior processes and facets for zygapophyseal joints that articulate adjacent vertebrae

• in quadruped tetrapods, pre and post-zygapophyses articulate adjacent vertebrae

• notochord restricted to nucleus pulpous of intervertebral disc in humans

centrum morphology

• amohucoelous - concave anterior and posterior articulating surfaces

• procoelous - concave anterior and convex posterior articulating surfaces

• opisthocoelous - convex anterior and concave posterior articulating surfaces

• acoelous - flat articulating surfaces

• heterocoelous - saddle-shaped articulating surfaces

protochordates evolution of post cranial axial skeleton

• have notochord

• hydrostatic organ with elastuc properties that resist axial compression

fishes evolution of post cranial axial skeleton

• each vertebrae consists of centrum and neural arch

• trunk vertebrae contains ribs, whereas caudal vertebrae lack ribs

• ribs protect viscera and provide muscle attachment

• ventral ribs from hemal arch in caudal region to protect vasculature

• notochord remains in some vertebrates

shark

• notochord constricted within each vertebrae

• centra are amphicoelous

• spinal cord enclosed by neural and inter neural arches

• hemal arches consists of paired ventral plates

bony fishes

• most have only ventral ribs but some have ventral and dorsal ribs

• centra are amohicoelous

rhipidistians

• notochord is surrounded by intercentrum and pleurocentrum, known as aspidospondyly

median fins

• includes dorsal and anal fins

• spines - hard and pointed, unsegmented, unbranched

• lepidotrichia - softer, segmented, branched

caudal fins

• sharks - heterocercal tail - upper lobe larger than lower, vertebral column extending into upper lobe, generates force forward and up

• primitive actinoptergyians - abbreviated heterocercal tail - externally but not internally symmetrical, vertebral column extends dorsally

• teleosts - homocercal tail - upper and lower lobes symmetrical, vertebral column ends at base

• enlarged hemal and neural spines form plates that support fin rays and produces forward thrust

• lateral undulation of vertebral column in fishes assists in locomotion

tetrapods evolution of post cranial axial skeleton

2 vertebrae types

• aspidospondyly, all bony elements remain separate

• holospondyly, all bony elements fused into single structure

• intercentrum became prominent in the temnospondyl lineage

• pleurocentrum became prominent in the anthracosaur linegae

• intercentrum does not contribute to centrum in amniotes and is homologous with head of ribs

• regionalization

• pre and post zygapophyses articulate adjacent vertebrae in tetrapods

amphibians

• lateral undulation of vertebral column in salamanders assist in locomotion

• frog urostyle adapted for saltatorial locomotion by transferring force from legs to body

reptiles

• presence of atlas and axis

lizards and crocodiles

• gastralium - dermal ribs restricted to ventral body wall, used from muscle attachment and abdominal support

turtles

• appendicular skeleton lies inside rib cage

• thoracic vertebrae and ribs expand and fuse with dermal bony plates and keratinized epidermal plates/ skutes of the integument to form carapace

• plastron consists of dermal bony plates, clavicle elements, and keratinized epidermal plates/ skutes

• 8 double jointed cervical vertebrae permits extensive range of motion

pleurodire turtles

retract head by bending the neck horizontally

cryptodire turtles

retract head into shell by bending the neck in a vertical s shape

archelon

• late cretaceous of the western interior seaway of north america

• 4.9m long

• leathery carapace, narrow skull with extreme overbite

snakes

• ribs found throughout trunk, caudal vertebrae without ribs

• lacks sternum

eophis

• oldest snake found from the middle jurassic

• limbs and girdles

najash from the late cretaceous of south america

• two legged with a sacrum and pelvic girdle

• no extant species shows any remains of the pectoral girdle or forelimbs

• remnanats of the pelvic girdle and hindlimb are found in basal snakes

birds

• pygostyle

• uncinate processes strengthen rib cage

• synsacrum

• carinate birds have enlarged sternal keel to support flight muscles

• ratite birds lack distinctive keel

mammals

• cervical vertebrae includes atlas, axis and 5 additional cervical vertebrae

• thoracic - articulates with ribs

• lumbar - robust lower back vertebrae

• sacrum - fused sacral vertebrae

• caudal - tail vertebrae

• 12 pairs of ribs in humans

• true ribs connect with sternum via costal cartilage

• false ribs no direct connect with sternum

• help strengthens body wall

• protect thoracic organs

• surface for muscle attachment

• assist in breathing

• sternum forms complete enclosure of chest region

• consists of manubrium, sternal body, xiphoid process in humans

• sternal body made up of multiple sternebrae in many mammals

• axial skeleton connected to pectoral girdle via articulation between the manbrium of the sternum and clavicle in humans

apendicular skeleton

includes paired fins or limbs and supporting girdles

fishes evolution of appendicular skeleton

• derived ostracoderms - pectoral girdle/fins, lacked pelvic fins

• lampreys and hagfish - lack post pectoral and pelvic girdle/fins

• placoderms - both pectoral and pelvic girdles/fiins

• acanthodian - both pectoral and pelvic girdles/fins, preceded by spines

shark evolution of appendicular skeleton

• pectoral girdle and fins

• pectoral girdle has no connection with skull or vertebral column

• stabilizers, provides lift

• basal pterygiophores articulate with scapular portion of the pectoral girdle

• radial pterygiophores support ceratotrichia

• pelvic girdle and fins

• pelvic girdle has no connection to vertebral column

• stabilizers

• claspers for reproduction

bony fishes actinopterygians evolution of appendicular skeleton

• pectoral girdle and fins - scapulocoracoid supports basal and radial pterygiophores and lepidotrichia - attached to back of skull via cleithrum, postcleithrum, supracleithrum, posttemporal bones and clavicle

• pelvic girdle and fins - pelvic girdle and fins located anterior and ventral to pectoral girdle and fins in teleosts

bony fishes sarcopterygians evolution of appendicular skeleton

• fleshy lobe like stalk extending from body

• pectoral girdle connected to skull

tiktaalik

• transiotional form

• tetrapod like limb bones and functional wrist joint but fin rays instead of digits, pectoral girdle separate from skull forming mobile neck

• girdle and fins bones mostly resemble tetrapod girdle and limb bones

• metapterygial axis is important for fin to limb transition

tetrapod evolution of appendicular skeleton 1

• early tetrapod girdle were robust

• pelvic girdle becomes attached to vertebral column

• significant loss of dermal bone attaching pectoral girdle to skull

• dermally derived cleithrum, clavicle, inter clavicle remains in some tetrapods

• scapulocoracoid bone of pectoral girdle will eventually be formed by 2 separate endochondral ossification centers producing separate scapula and coracoid bones in most extant tetrapods

• coracoid process of therian mammals is not homologous with the coracoid bone of other vertebrates

• cleithrum, clavicle, interclavicle reduced in frogs and lost in extant salamanders

• cleithrum lost in amniotes

• turtles, clavicle and interclavicle incorporated into plastron

• birds, clavicle and interclavicle fuse forming furcula, strengthens thoracic skeleton for flight

• eutherians, interclavicle is lost but retain clavicle

• tetrapod limb characterized by a chiridium

tetrapod evolution of appendicular skeleton 2

• stylopodium divides to form the preaxial and post axial elements of the zeugopodium

• postaxial element branches to form the autiopodium

• metapterygial axis is important for fin to limb transition

• earliest tetrapod had variable number of digits

• 5 digit pattern is a stabilization from a polydactylous condition

• marine tetrapods have secondarily returned to water and evolved flippers

• generally exhibit polyphalangy

• polydactyly is very rare

• ichthyosaur flipper exhibits polydactyly

• more often there is a reduction of digits

• most dog breeds have 4 regular digits on the forelimb and one dewclaw whereas the hindlimb have 4 regular digits

posture and locomotion plantigrade

walking on soles of feet

posture and locomotion digitigrade

walking with ankle and heel off the ground

posture and locomotion unguligrade

walking on ends of digits and hooves

• artiodactyls weight bearing axis through 3 and 4 metacarpals/metatarsals and digits

• perissodactyls weight bearing axis through 3 metacarpal/metatarsal and digit

sprawling posture

most primitive, upper limbs typically held horizontally, body may or may not dragged on the ground, lateral undulations with each step

erect posture

mammals, dinosaurs, limbs placed beneath body, often associated with endothermy, avoids carriers constraint and allows prolonged activity

flight

evolved independently 3 times

• pterosaurs - large membrane wing supported by elongated 4 digit and attached to side of body, entire 5 digit lost

• birds - feathered wing, fusion of carpals with metacarpals forming carpometacarpus and fusion and loss of digits

• bats - membrane wing supported by elongated 2 thru 5 digits, 1 digit free from wing and forms hook