Chapter 9: Appendicular Skeleton

Question 0

Posterior

Answer 0

Pelvic girdle supporting pelvic fin or hind limb

Question 1

Anterior

Answer 1

Pectoral girdle supporting pectoral fins or limbs

Question 2

Ostracoderms

Answer 2

No paired appendages
Pectoral “spikes”, “lobes”, “folds”
Non-mobile
No skeleton associated with them

Question 3

Origin of paired fins

Answer 3

•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

Question 4

Placoderms

Answer 4

1st paired appendages (fins)
Skeleton associated with them
“Prints” of muscle >mobile
Bony or cartilage fin rays

Question 5

Fin skeleton

Answer 5

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

Question 6

Fish Pelvic Girdle

Answer 6

Small and not attached to vertebrae

Question 7

Fish Pectoral Girdle

Answer 7

Large and attached to head
Dermal components:
1- clavicle
2- cleithrum
3- supracleithrum
4- post-temporal 
Replacement bones (from cartilage precursors): coracoid, scapula, suprascapula

Question 8

Sarcopterygii

Answer 8

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

Question 9

Tetrapod pelvic girdle

Answer 9

3 bones fused
  -ilium >cranial
  -ischium >caudal
  -pubis >ventral (usually) 
Trend toward firmer attachment to vertebral column via sacrum

Question 10

Tetrapod pectoral girdle

Answer 10

Dermal bone is less important 
Replacement bone (endochondral) more important 
Connection of pectoral girdle to skull broken

Question 11

Appendicular skeleton trend

Answer 11

-early appendicular skeleton = dermal
-increase in sub-dermal elements; loss of dermal bone
Ex: humans have only one dermal bone in appendicular skeleton = clavicle

Question 12

Fish vs Tetrapod appendages

Answer 12

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

Question 13

Fish to Amphibian

Answer 13

• Tiktaalik to Labyrinthodont
• Fins to limbs
• Amphibians have weak limbs, splayed to the side
• lateral “swimming” movements

Question 14

Reptiles

Answer 14

Strong limbs and girdles -sacrum
Most have splayed stance
Some have legs under body
  -synapsids
  -thecodonts
  -dinosaurs

Question 15

Birds and mammals

Answer 15

Specializations

Question 16

Tetrapod trends

Answer 16

1. Reduction in # of limb elements
   - frogs fused radioulna, tibiofibula
   - birds tibiotarsus
   - loss of digits in deer, horse rhinoceros
2. Disproportionate lengthening of limb elements
   - bat fingers (modified for flight)
   - horse foot
3. Sub axial flexion
   - limbs held more under the body than splayed to the side
4. Alteration of foot posture to lengthen limb
   >plantigrade, digitigrade, unguiligrade

Question 17

Plantigrade

Answer 17

Heel, wrist touch ground

Primitive: humans, bears

Question 18

Digitigrade

Answer 18

Walk with heel and wrist above ground = cat, dog

Question 19

Unguiligrade

Answer 19

Walk on toe tips
Ex: horse, deer

Perissodactyl = odd # toes
Artiodactyl = even # toes

Question 20

Evolution of flight: Why did flight evolve?

Answer 20

• 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

Question 21

Muscle Homologies

Answer 21

• use nerve to tell where muscle is coming from and going to
• embryology
• attachment similarity
• function

Question 22

Function of muscles

Answer 22

• move bones >locomotion
• heat (endotherms)
• keep internal organs functioning (cardiac & smooth muscle)
• restrict space (abdominal muscle)
• fight gravity (quadrupeds)
• electric organs (eels)
• protection

Question 23

Skeletal muscle

Answer 23

Striated
Multiple nuclei
Straight lines
Voluntary

Question 24

Smooth muscle

Answer 24

Pointed ends Singular nuclei Involuntary Pod shaped

Question 25

Cardiac muscle

Answer 25

``` Striated Anastemosis Intercalated discs >division b/w s >gap junctions -cell communication ```

Question 26

Sheaths

Answer 26

- 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)

Question 27

Apopneurosis

Answer 27

Flat tendon made of sheathing at the distal end of a muscle

Question 28

Skeletal muscle at a microscopic/sub cellular level

Answer 28

- Actin & myosin = 2 proteins that make up skeletal muscle for connection - sacromere

Question 29

Naming muscles

Answer 29

``` 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 ```

Question 30

Origin

Answer 30

Midline (body) Proximal (limb, speed) Stable (doesn't move a lot) Antagonistic pairs

Question 31

Insertion

Answer 31

Distal (strength) | Movable

Question 32

Muscle motions

Answer 32

- adduct (move toward) / abduct (move away from) - flex (decrease angle) / extend (increase angle) - levator (elevate) / depress (lower)

Question 33

Embryology

Answer 33

1. Axial •epaxial myomeres •hypaxial myomeres >epimere 2. Hypobranchial •modified axials >epimere 3. Appendicular >epimere 4. Branchial •associated w/ gill slits >epimere 5. Extrinsic eye muscles >epimere 6. Cardiac >hypomere 7. Smooth >hypomere

Question 34

Phylogeny of muscles: Agnatha

Answer 34

``` Axial well-developed -no subdivision into epaxial, hypaxial -segmentation (primitive trait) No appendicular Hypobranchials, branchials = poorly developed Mouth muscles specialized ```

Question 35

Jawed fish

Answer 35

``` Epaxial & hypaxial divisions -segmented head to tail into myomeres Hypobranchial -pectoral girdle, branchial arches, jaw Appendicular -dorsal = abductors -ventral = adductors ```

Question 36

Evolutionary trends

Answer 36

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

Question 37

Amphibians axial muscles

Answer 37

``` 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) ```

Question 38

Amphibians new muscles: appendicular

Answer 38

``` Pelvic -small Pectoral -more complex, larger -connection to head is gone (more space for muscles) ```

Question 39

Reptiles, mammals muscles

Answer 39

Epaxial (from lateral to medial) - iliocostalis (costalis = rib) - longissimusdorsi (cat- erector spinae) - transversospinalis (cat- multifidi) Hypaxial 1. Subvertebral - reduced 2. Rectus abdominis - doesn't insert on pectoral girdle 3. Lateral group - abdominal (same) - chest; ribs (new)

Question 40

Tetrapods appendicular muscles

Answer 40

``` 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 ```

Question 41

Branchial = Tetrapod derivatives

Answer 41

Jaw muscles, 1st and 2nd pharyngeal arches Ear muscles Shoulder, head >ex: trapezius Larynx, throat muscles

Question 42

Cutaneous muscles

Answer 42

``` *under skin Rare in reptiles Most common in mammals Platysma of neck -diversifies into facial muscles to move lips, ears -chewing, communication, expression ```

Question 43

Specialization: Flight

Answer 43

Supracoracoideus muscle: like a pulley for easy upstroke w/ small muscle Pectoralis muscle: huge, originates on keel of sternum for powered downstroke when contracts