Chapter 9: Appendicular Skeleton Flashcards
Posterior
Pelvic girdle supporting pelvic fin or hind limb
Anterior
Pectoral girdle supporting pectoral fins or limbs
Ostracoderms
No paired appendages
Pectoral “spikes”, “lobes”, “folds”
Non-mobile
No skeleton associated with them
Origin of paired fins
•Gill arch theory -not really
>gill arches modified, cartilages moved to shoulder & became part of fin
•Fin-fold theory
>flaps of tissue get bone vs gill tissue and retain gills for respiration
Placoderms
1st paired appendages (fins)
Skeleton associated with them
“Prints” of muscle >mobile
Bony or cartilage fin rays
Fin skeleton
Basal pterygiophores (most proximal, closest to body) Radial pterygiophores (radiate out from basal) Fin rays (most dorsal) >ceratotrichia in sharks (cartilage) >lepidotrichia in bony fish *trichia = hair/thread
Fish Pelvic Girdle
Small and not attached to vertebrae
Fish Pectoral Girdle
Large and attached to head Dermal components: 1- clavicle 2- cleithrum 3- supracleithrum 4- post-temporal Replacement bones (from cartilage precursors): coracoid, scapula, suprascapula
Sarcopterygii
Basals and radials line up into fin and homologies w/ tetrapod limbs are clear
Muscles are no longer in body wall
Muscles extend down into the fin
Tetrapod pelvic girdle
3 bones fused -ilium >cranial -ischium >caudal -pubis >ventral (usually) Trend toward firmer attachment to vertebral column via sacrum
Tetrapod pectoral girdle
Dermal bone is less important Replacement bone (endochondral) more important Connection of pectoral girdle to skull broken
Appendicular skeleton trend
-early appendicular skeleton = dermal
-increase in sub-dermal elements; loss of dermal bone
Ex: humans have only one dermal bone in appendicular skeleton = clavicle
Fish vs Tetrapod appendages
Fish:
Uniform function, they only swim
Varied number and position of bones in limb
Tetrapods:
Varied function; run, walk, swim, crawl, burrow, hop, fly
Uniform structure
Fish to Amphibian
- Tiktaalik to Labyrinthodont
- Fins to limbs
- Amphibians have weak limbs, splayed to the side
- lateral “swimming” movements
Reptiles
Strong limbs and girdles -sacrum Most have splayed stance Some have legs under body -synapsids -thecodonts -dinosaurs
Birds and mammals
Specializations
Tetrapod trends
- Reduction in # of limb elements
- frogs fused radioulna, tibiofibula
- birds tibiotarsus
- loss of digits in deer, horse rhinoceros - Disproportionate lengthening of limb elements
- bat fingers (modified for flight)
- horse foot - Sub axial flexion
- limbs held more under the body than splayed to the side - Alteration of foot posture to lengthen limb
>plantigrade, digitigrade, unguiligrade
Plantigrade
Heel, wrist touch ground
Primitive: humans, bears
Digitigrade
Walk with heel and wrist above ground = cat, dog
Unguiligrade
Walk on toe tips
Ex: horse, deer
Perissodactyl = odd # toes Artiodactyl = even # toes
Evolution of flight: Why did flight evolve?
- to help escape from predators
- to help catch prey
- to help move efficiently
- to free the hind legs for use as weapons
- to gain access to new food sources or an unoccupied niche
Muscle Homologies
- use nerve to tell where muscle is coming from and going to
- embryology
- attachment similarity
- function
Function of muscles
- move bones >locomotion
- heat (endotherms)
- keep internal organs functioning (cardiac & smooth muscle)
- restrict space (abdominal muscle)
- fight gravity (quadrupeds)
- electric organs (eels)
- protection
Skeletal muscle
Striated
Multiple nuclei
Straight lines
Voluntary
Smooth muscle
Pointed ends
Singular nuclei
Involuntary
Pod shaped
Cardiac muscle
Striated Anastemosis Intercalated discs >division b/w s >gap junctions -cell communication
Sheaths
- epimyseum (outermost layer that goes around each muscle organ)
- perimyseum (middle layer that goes around fascicles)
- endomyseum (innermost layer that goes around each muscle cell)
Apopneurosis
Flat tendon made of sheathing at the distal end of a muscle
Skeletal muscle at a microscopic/sub cellular level
- Actin & myosin = 2 proteins that make up skeletal muscle for connection
- sacromere
Naming muscles
1. Direction that fibers run Ex: external, internal, transverse obliques 2. Size Ex: vastus lateralis 3. Location Ex: vastus medialis 4. Number of divisions Ex: biceps 5. Origin & insertion Ex: xiphihumeralis 6. Action Ex: levator palatoquadrati 7. Shape Ex: trapezius
Origin
Midline (body)
Proximal (limb, speed)
Stable (doesn’t move a lot)
Antagonistic pairs
Insertion
Distal (strength)
Movable
Muscle motions
- adduct (move toward) / abduct (move away from)
- flex (decrease angle) / extend (increase angle)
- levator (elevate) / depress (lower)
Embryology
- Axial
•epaxial myomeres
•hypaxial myomeres
>epimere - Hypobranchial
•modified axials
>epimere - Appendicular
>epimere - Branchial
•associated w/ gill slits
>epimere - Extrinsic eye muscles
>epimere - Cardiac
>hypomere - Smooth
>hypomere
Phylogeny of muscles: Agnatha
Axial well-developed -no subdivision into epaxial, hypaxial -segmentation (primitive trait) No appendicular Hypobranchials, branchials = poorly developed Mouth muscles specialized
Jawed fish
Epaxial & hypaxial divisions -segmented head to tail into myomeres Hypobranchial -pectoral girdle, branchial arches, jaw Appendicular -dorsal = abductors -ventral = adductors
Evolutionary trends
Fish -> Tetrapod
Axial muscles less prominent
Loss of segmentation of axials
Remaining axial muscles more closely related to vertebral column
Appendicular muscles larger, more diverse
Branchial muscles repurposed
Amphibians axial muscles
Epaxial
-segmented, unspecialized; dorsalis trunci
Hypaxial = better developed, 3 groups
1) subvertebral
-small, ventral flexion, under vertebrae
2) rectus abdominis
3) lateral group
-external oblique (hands in pockets)
-internal oblique (opposite)
-transverse abdominal (horizontal)Amphibians new muscles: appendicular
Pelvic -small Pectoral -more complex, larger -connection to head is gone (more space for muscles)
Reptiles, mammals muscles
Epaxial (from lateral to medial)
- iliocostalis (costalis = rib)
- longissimusdorsi (cat- erector spinae)
- transversospinalis (cat- multifidi)
Hypaxial
- Subvertebral
- reduced
- Rectus abdominis
- doesn’t insert on pectoral girdle
- Lateral group
- abdominal (same)
- chest; ribs (new)
Tetrapods appendicular muscles
Sources: -branchial (ex: trapezius from cucullaris) -axial (ex: serratus anterior) -from fish appendicular •dorsal mass >forelimb (latissimus dorsi, triceps) >hindlimb •ventral mass >forelimb (pectoralis, biceps) >hindlimb (adductor femoris, hamstrings, biceps femoris, gracilis) -remember rotation of elbows & knees -far greater subdivision of Tetrapod vs. fish muscles
Branchial = Tetrapod derivatives
Jaw muscles, 1st and 2nd pharyngeal arches
Ear muscles
Shoulder, head >ex: trapezius
Larynx, throat muscles
Cutaneous muscles
*under skin Rare in reptiles Most common in mammals Platysma of neck -diversifies into facial muscles to move lips, ears -chewing, communication, expression
Specialization: Flight
Supracoracoideus muscle: like a pulley for easy upstroke w/ small muscle
Pectoralis muscle: huge, originates on keel of sternum for powered downstroke when contracts
