Appendicular skeleton Flashcards
What are 3 major components of the appendicular skeleton?
pectoral girdle
pelvic girdle
limbs
What are the 2 components of the pectoral girdle?
endochondral/cartilage replacement
dermal bone
What are the bones in the cartilage replacement of the pectoral girdle?
coracoid
scapula
suprascapula
What are the bones in the dermal investing of the pectoral girdle?
clavicle
cleithrum
supracleithrum
post-temporal
T or F: cartilaginous fishes like Chondrichthyes have a pectoral girdle composed of bone
false! only cartilaginous elements
What modification do bony fish have that Chondrichthyes lack?
dermal elements of the pectoral girdle (bones)
Describe the pectoral girdle in frogs
lost most of the dermal bones (ex. cleithrum)
humeral muscles moved to dorsal part of girdle
Describe the pectoral girdle in non-bird reptiles
dermal elements (clavicle and sometimes cleithrum) and replacement elements (scapula and part of coracoid) present
Describe the pectoral girdle in birds
clavicles (dermal) retained and fuse to form furcula (wishbone)
paracoracoid and scapula present
scapula dorsal to rib cage
Describe the pectoral girdle in mammals
loss of coracoid
only two bones present:
- scapula (replacement)
- clavicle (dermal)
What type of mammals may have reduced or absent clavicles?
running mammals ex. cats
Which pectoral girdle element is retained in all mammals? what does it look like?
scapula - broad, flat plate
What is the function of the scapula?
muscular attachment
What composes the pelvic girdle?
cartilage replacement bone only
T or F: the pelvic girdle has dermal elements
false
In which group is the pelvic girdle a single element and unattached to the vertebral column?
fish
What are the 3 main ossification areas of the pelvic girdle in most tetrapods?
ilium - wing
ischium - back
pubis - front
in more advanced vertebrates, which becomes the largest pelvic element?
the ilium
Pubic fusion occurs in most vertebrates, except which group?
birds
What is the largest foramen in the tetrapod body?
the obturator foramen in the pelvic girdle = nerve passage, blood vessels, and muscle connections
Is the pelvic girdle of amphibians attached to the vertebral column?
yes
Describe the difference between salamander and frog pelvic girdles
salamanders have short and more rectangular
frogs have elongated iliums
How is the pelvic girdle modified to allow frogs to jump?
a ligament between ilium and sacral vertebra = frees ilium to move separately and strong muscle attachment = strong jumps
Describe the pelvic girdle in non-bird reptiles
mostly reduced and fenestrated
large gap between pubis and ischium = leg muscle attachment
ilium is elongated
legless lizards have vestigial pelvic girdle
snakes have lost pelvic girdle entirely
Which group of reptiles have lost the pelvic girdle entirely?
snakes
Which group of vertebrates have a mostly reduced pelvic girdle?
non-bird reptiles
Why is it beneficial for birds to lack pubic bone fusion?
to produce larger eggs
How do birds compensate for the lack of pubic bone fusion?
their pelvic bones (ilium, ischium, pubis) are fused together = innominate bone and is fused to the sacrum
What are the 3 pelvic bones?
ilium
ischium
pubis
What is the innominate bone?
the result of the 3 pelvic bones fusing together
Which vertebrate groups have an innominate bone?
birds and mammals
What allows birds to be bipeds?
their expanded ilium and ischium to allow for enlarged muscles for walking on two legs
Describe the mammalian pelvic girdle
made from the fusion of the 3 pelvic bones = innominate bone
pubic symphysis
How does the pelvic girdle of quadruped mammals differ to that of bipeds?
quadruped pelvic girdle has an elongated pelvis for more muscle attachment
What are the major bones in the forelimb?
humerus - upper limb
radius - larger, anterior lower limb
ulna - smaller, posterior lower limb
carpals - wrist bones
metacarpals - proximal digits
phalanges - distil digits
What are the major bones of the hindlimbs?
femur - thigh
tibia - larger, anterior shank bones
fibula - smaller, posterior shank bones
tarsals - ankle bones
metatarsals - proximal digit bones
phalanges - distil digit bones
Which component of the appendicular skeleton are most tetrapods’ limbs more firmly attached? which group(s) is excluded?
pelvic girdle
fish = more strongly connected to pectoral
Which component of the appendicular skeleton are fishes limbs more firmly attached?
pectoral girdle
What are fish fins/limbs made of?
spines or rays (not the same bones as in fore and hindlimbs of other groups)
How are fish fins supported? (ie., are they connected to the skeleton)?
except for the caudal fin, there’s no connection between fins and the spine
fins are supported only by muscle
What is the function of pectoral fins in fish?
allow fish to maintain depth in water by producing lifting forces
in some fish, fins are specialized for ‘walking’ or ‘flying’
What is the function of pelvic fins in fish?
change direction
stop or turn quickly
How are the limbs of amphibians distributed on the body?
aside from Caecilians
amphibians have 4 legs spread out on both sides of the body
How many digits do amphibians have on their forelimbs? hind limbs?
forelimbs: 4 digits
hind limbs: 5 digits
How are limbs modified in jumping or swimming frogs?
hind limbs are larger than forelimbs
How are limbs modified in running or walking amphibians?
both fore- and hind limbs are short and similar in length
Which vertebrates can regenerate limbs?
frogs and salamanders
How are non-bird reptile limbs situated on the body?
to either side of the body at right-angles
T or F: the common ancestor of all reptiles had 4 limbs
true
Is the lack of limbs in snakes a derived or lost characteristic?
secondarily lost characteristic
the common ancestor of all reptiles had 4 limbs
Are birds quadrupeds like other reptiles, or bipeds like some mammals?
bipeds
How have bird forelimbs been modified? What has this been useful for?
evolved into wings - useful for flight
How have the hind limbs of birds been modified to support bipedalism?
many bones are fused to increase strength
What are the 3 different walking/weight bearing types?
plantigrade
digitigrade
unguligrade (2 types)
Describe plantigrades and give an example
animals that bear weight on the entire sole of their foot
ex. humans, bears
Describe digitigrades and give an example
animals that bear weight on only their digits
ex. cats
Describe unguligrades and give an example
animals that bear weight only on the tip of their digits/toes
ex. horse
What are the two types of unguligrades?
digit III only - ex. horse
digit III + IV - ex. pig, cow, deer
What type of -grade are birds?
plantigrades - they use all 4 digits to bear weight when they walk
How many digits do birds have in their hind limbs?
4
digit I: back
digits II-IV: forward
How is the scapula different between quadrupeds and bipeds?
quadrupeds: scapula is vertical because forelimbs are beneath the body
bipeds: scapula is horizontal because forelimbs are beside the body
How is a vertical scapula an advantageous adaptation for animals that walk on two legs and climb?
horizontal scapulas can move with arms/forelimbs as they move forward and backward when running or climbing
How are the forelimbs attached in bipeds? how is this evolutionary advantageous?
to the sternum via the clavicle
beneficial for animals that climb because it allows arm and chest muscles to pull body weight
How are the forelimbs attached in quadrupeds like cats? how is this evolutionary advantageous?
there is no connection between clavicle and sternum
cat clavicles are very reduced
instead, forelimbs are connected to sternum via compressible ligaments
cat’s have stronger hind limbs than forelimbs, so there doesn’t need to be strong connection to joints for forelimbs
How are quadruped (ex. cat) hind limbs modified for walking on 4 legs?
hind limbs are more muscular than forelimbs = provide most of the forward momentum
hindlimbs connect to vertebral column via joints between the innominate bone and the sacrum (3 fused vertebrae) = increases muscular power
How is the reduced clavicle in cats beneficial?
they can land on their forelimbs from high heights without hurting themselves because there’s no clavicle = instead, soft tissues in the collar and shoulder absorb the landing shock
