Skeletal System - 1b Flashcards
Two main divisions of vertebrate skeleton
- axial skeleton
- appendicular skeleton
axial skeleton
- skull
- vertebral column
- sternum
- ribs
appendicular skeleton
- limbs
- fins
- wings
- pectoral and pelvic girdles
- Supports the head and trunk
- Protects the spinal cord and roots of spinal nerves
vertebral column
segments of vertebral column from superior to inferior
- cervical
- thoracic
- lumbar
- sacral
- coccyx
cervical
neck
thoracic
chest
lumbar
small of back
sacral
sacrum/pelvic
coccyx
tailbone
consisted of an hypocentrum plus 2 pleurocentra called a rachitomous vertebra
Crossopterygian vertebrae
Crossopterygian vertebrae composition
- hypocentrum
- rachitomous vertebra
large, wedge-shaped piece
hypocentrum
smaller intersegmental pieces
pleurocentra
two pleurocentra
rachitomous vertebra
trend in vertebra evolution
- pleurocentra to increase in size
- hypocentrum to decrease in size
consists of centrum, 1 or 2 process, and various processes
vertebrae
parts of the vertebrae
- neural spine
- neural arch
- centrum
- neural canal
- zygapophyses
- diapophyses
- parapophyses
Types of centrum
- amphicelous
- acelous
- procelous
- opisthocoelous
- heterocoelous
- concave at both ends
- most fish, a few salamanders (Necturus), & caecilians
amphicelous
- flat-ended centrum
- mammals
acelous
- concave in front & convex in back
- anurans & present-day reptiles
procelous
- convex in front & concave in back
- most salamanders
opisthocoelous
- saddle-shaped centrum at both ends
- birds
heterocoelous
amphicelous animals
- most fish
- few slamanders (Necturus)
- caecilians
acelous animals
mammals
procelous animals
- anurans
- present-day reptiles
opisthocoelous animals
most salamanders
heterocoelous animals
birds
vertebral arches
- neural arch
- hemal arch/ chevrons
on top of centrum
neural arch
beneath centrum in caudal vertebrae of fish, salamanders, most reptiles, some birds, & many long-tailed mammals
hemal arch/ chevrons
- most common type of process
- extend laterally from the base of a neural arch or centrum & separate the epaxial & hypaxial muscles
transverse processes
articulate with ribs
- diapophyses
- parapophyses
- articulate with one another and limit flexion and torsion of the vertebral column
- projection from arches and centra
- some give rigidity to the column, articulate with ribs, or serve as sites of muscle attachment
- prezygapophyses
- postzygapophyses
prezygapophyses
cranial zygapophyses
postzygapophyses
caudal zygapophyses
- do not have typical fish vertebral columns
- vertebrae include neural arches (cartilaginous dorsal plates) & dorsal intercalary plates are located between successive arches
cartilaginous fishes
vertebra of cartilaginous fishes
- neural arches (cartilaginous dorsal plates)
- dorsal intercalary plates
located between successive arches
dorsal intercalary plates
- well-ossified amphicelous vertebrae
- notochord persists within each centrum (but constricted)
- neural arch associated with each centrum & hemal arches in tail (caudal) vertebrae
teleost
arch in tail of teleost vertebrae
hemal arches
single cervical vertebra; allows little head movement
amphibians
increased numbers of cervical vertebrae (usually 7) & increased flexibility
reptiles
usual no. of cervical vertebrae of reptiles
7
variable number of cervical vertebrae (as many as 25 in swans)
Birds
no. of cervical vertebrae of swans
25
usually 7 cervical vertebrae
mammals
mammal with six cervical vertebrae
- manatee
- two-toed sloth
mammal with eight cervical vertebrae
ant bear
mammal with nine cervical vertebrae
three-toed sloth
animals that have its 1st two cervical vertebrae modified & called the atlas & axis
- reptiles
- birds
- mammals
- 1st cervical vertebra
- ring-like (most of centrum gone)
- provides ‘cradle’ in which skull can ‘rock’ (as when nodding ‘yes’)
atlas
2nd cervical vertebra
axis
animals with ribs confined to anterior region of trunk
- Crocodilians
- lizards
- birds
- mammals
vertebrate with ribs
thoracic
vertebrate without ribs
lumbar
- may be long or short, cartilaginous or bony
- articulate medially with vertebrae & extend into the body wall
Ribs
have 2 pair of ribs for each centrum of trunk (dorsal and ventral rib)
A few teleosts
what does dorsal rib separate
epaxial and hypaxial muscles
ventral ribs only
most teleost
dorsal rib only
sharks
no ribs
agnathans
ribs usually articulate with vertebrae in moveable joints
Tetrapods
ribs articulated with every vertebra from the atlas to the end of the trunk
Early tetrapods
long ribs limited to thoracic region
Later tetrapods
most composed of a dorsal element (vertebral rib) & a ventral element (sternal rib)
Thoracic Ribs
dorsal element
vertebral ribs
ventral element
sternal rib
- may be ossified (birds)
- or remain cartilaginous (mammals)
- usually articulate with sternum (except ‘floating ribs’)
Sternal ribs
- found in birds
- provides rib-cage with additional support
uncinate processes
- Protects the heart and lungs, and assists breathing
- Support by the thoracic vertebrae
rib cage
how many pairs of ribs are there
12
connect directly to sternum
true ribs
no. of true ribs
7 pairs
do not connect directly to sternum
false ribs
no. of false ribs
5 pairs
do not connect to any bony/cartilaginous structure ventrally
floating ribs
sternum in amphibians
- absent in early amphibians
- only present in anurans among present-day amphibians
- sternum is a plate of cartilage & replacement bone
- sternum articulates with the pectoral girdle anteriorly & with a variable number of ribs
amniotes
name given to vertebrae between cervicals & sacrals when all articulate with similar ribs (e.g., fish, amphibians, & snakes)
dorsals
e.g. of animals with dorsals
- fish
- amphibians
- snakes
have short transverse processes that brace the pelvic girdle & hindlimbs against the vertebral column
sacral vertebrae
no. of sacral vertebrae in amphibians
1
no. of sacral vertebrae in living reptiles and most birds
2
no. of sacral vertebrae in most mammals
3-5
- single bony complex consisting of fused sacral vertebrae
- found when there is more than 1 sacral vertebra
sacrum
- found in birds
- produced by fusion of last thoracics, all lumbars, all sacrals, & first few caudals
- fused with pelvic girdle
- provides rigid support for bipedal locomotion
synsacrum
what is fused in synsacrum
- last thoracics
- all lumbars
- all sacrals
- first few caudals
no. of caudal vertebae in primitive tetrapods
50 or more
- number of caudal vertebrae is reduced
- arches & processes get progressively shorter (the last few caudals typically consist of just cylindrical centra)
present-day tetrapods
unique terminal segment called the urostyle
anurans
unique terminal segment in anurans
urostyle
last 4 or 5 caudal vertebrae fused to form pygostyle
birds
what is formed when last 4 or 5 caudal vertebrae in birds is fused
pygostyle
last 3 to 5 caudal vertebrae fused to form coccygeal (or tail bone)
apes and humans
what is formed by the fusion of 3-5 caudal vertebrae of apes and humans
coccygeal or tail bone
small, rounded elevation on an organ or bone
Tuberculum
ventral rib head
capitulum
- two cylinder-shaped projections of hard bone that stick out from the back part of the vertebral body, providing side protection for the spinal cord and nerves
- also serve as a bridge, joining the front and back parts of the vertebra.
pedicles
