Post-Cranial SkeletonAxial skeleton = vertebrae, sternum,

& ribs; endochondral bone.

Appendicular Skeleton

Pectoral skeleton supports pectoral appendages (arms); dermal and endochondral bone.

Pelvic skeleton supports pelvic appendages (legs); endochondral bone.

Human Vertebra

body(centrum)

spinousprocess(neuralspine)

superiorarticularprocess

inferiorarticularprocess

transverseprocess

neuralarch

facet forhead of rib

facet fortubercle of rib

Intervertebral discs between (annulus and nucleus)

Cervical Vertebrae – 7; #1 = atlas, #2 = axis; forked neural spine on #2-#7

Thoracic Vertebrae – 12 (ribs articulate)

Lumbar Vertebrae – 5 (no ribs)

Sacral Vertebrae – 5; fusion begins at 16-18 and usually completed at 25

Coccygeal Vertebrae – 3-5; may become fused (= caudal vertebrae)

Human Vertebrae

Human Vertebrae

Intervertebral Disc Problems

Atlas, Axis, & Other Cervical Vertebrae

transverse foramen(vertebral artery)

Thoracic Vert. Articulate w/ Ribs

costalcartilage

Ribs – 12; on thoracic vertebrae

True Ribs – 7; contact sternum directly

False Ribs – 5; don’t contact sternum directly

“False” / Vertebrochondral Ribs – 3; fuse to a single costal cartilage element

Floating Ribs – 2; don’t contact sternum

Sternum – segments fuse to form 3 bones; manubrium, body, xiphoid process (x.p. doesn’t articulate with ribs)

Human Ribs & Sternum

Human Ribs

Human Sacral/Coccygeal Vert.

sacrumcoccyx

Vertebral Development Sclerotome = forms vertebral elements

Myotome = forms muscle

Both separated into segments when the somites form.

Vertical myosepta exist between segments of myotome (derived from the somite) .

The myotome is also divided by a horizontal septum.

Neural & hemal arches are centered on the vertical myosepta.

Vertebral Development

Vertebrate Neurula (section)

notochordsomite

inter-mediatemeso-derm

lateralplate mesoderm

gut

Vertebrate Embryo (section)neuralcrestcells

dermatome

sclerotome

myotome

splanchnicmesoderm

somaticmesoderm

gut

inter-mediatemeso-derm

lateralplate mesoderm

Vertebrate Embryo (section)

gut

inter-mediatemeso-derm

lateralplate mesoderm

neuralcrestcells

dermatome

sclerotome

myotome

splanchnicmesoderm

somaticmesoderm

Vertebrate Embryo (section)

gutcoelom

pigment cell precursors(neural crest)

ganglionicneuron precursors(neural crest)

dermatome

sclerotome

myotome

dorsal & ventralmesenteries(splanchnic mesoderm) lateral

plate mesoderm

Vertebrate Embryo (section)

gut

dermatome

vertebra

myotome

horizontalseptum

dorsal & ventralmesenteries(splanchnic mesoderm)

coelom

lateralplate mesoderm

Vertebrate Embryo (section)

gut

dermatome

vertebra

myotome

horizontalseptum

dorsalmesentery(splanchnic mesoderm)

coelom

lateralplate mesoderm

Fish Section

Comparative Vertebra Structure Hagfishes lack vertebral structures. Neural arches dorsal to notochord

surrounds dorsal nerve cord. Neural spines project above neural

arch Hemal arches ventral to notochord

around blood vessels in “tail” Hemal spines project below hemal arch

notochord

Vertebral Centra Centrum = solid bone or

cartilage vertebral “segment;” “replaces” part of notochord

Intervertebral pads = separate centra; derived, in part, from the notochord

Centra evolved at least three times in vertebrates (Chondrichthys, Tetrapoda, & Amia + Teleosts)

Non-tetrapod vertebrates

Trunk (Thoracic, Abdominal) vertebrae = anterior; often bear ribs, lack hemal arches

Caudal vertebrae = posterior; rarely bear ribs, have hemal arches

Tetrapods

Have Ant. & Post. Articulatory Processes

Cervical vertebrae = neck vertebrae

Thoracic vertebrae = have ribs

(Lumbar vertebrae = lack ribs)

Sacral vertebrae = attached to pelvic girdle

Vertebral Regionalization

Vertebral Regionalization

Synsacral vertebrae = vertebrae attached to pelvic girdle (homologs of sacral, lumbar,

some thoracic and some caudal vertebrae)

Bird Vertebral Regionalization

Atlas = first cervical vertebra in tetrapods;

reduced centrum, large neural canal

Axis = second cervical vertebra in amniotes (Lissamphibians have only 1 cervical vertebra, an atlas.);

odontoid process (dens) for rotation of atlas, large neural canal

Atlas/Occipital Condyle joint = tilting

Atlas/Axis joint = rotation

Cervical: Atlas & Axis

Vertebral RegionalizationGroup Trunk Vertebrae“fish”: hagfishes, lampreys, chondrichthyans, lungfish, actinopterygiians,

many trunk (number greatly variable)

amphibians 1 cervical, few to many trunk, 1 sacral

mammals 7 cervical, 13-27 trunk (9-20 thoracic & 4-7 lumbar), 3-5 sacral,

turtles, lizards & snakes, & crocodilians

7-9 cervical, few to many trunk (especially many in snakes), 2 sacral (0 in

snakes)

birds 11-25 cervical, 3-10 trunk, 10-22 synsacral

Caudal (“Tail”) Vertebrae vary greatly in number, even within groups.

Subphylum Vertebrata

hagfis

hes

lam

preys

Chondrichth

ys

Actin

optery

gii

coel

acan

ths

lungfis

hes

amphib

ians

Mam

mal

ia

Reptil

iace

ntr

a

R S G AT

cen

tra

axis,>1 sacralvertebrae(Amniota)

centra; atlas; sacral

vertebrae; articulatory processes

Ribs Form within myosepta

from cartilage.

Dorsal ribs form where the myoseptum intersects the horizontal septum

Ventral ribs form where the myoseptum intersects the coelom somatic mesoderm.HOMOLOGY CONTROVERSY

Vertebrate Embryo (section)

gut

dermatome

vertebra

myotome

horizontalseptum

dorsalmesentery(splanchnic mesoderm)

coelom

lateralplate mesoderm

Ribs

dorsal rib

ventral rib

Tetrapod Ribs

dorsal rib?or

ventral rib?

capitulum

tuberculum

Sternum Sternum (midventral endochondral element)

where ribs often articulate

Evolved independently in most groups.

Mammalian sternum composed of multiple ossified elements (stern - ebrae); manubrium = 1st; xiphisternum/xiphoid process = last

Subphylum Vertebrata

hagfis

hes

lam

preys

Chondrichth

ys

Actin

optery

gii

coel

acan

ths

lungfis

hes

amphib

ians

Mam

mal

ia

Reptil

ia

Ribs (of some kind)(Gnathostomata)

2 headed dorsal ribs, ventral ribs lost (Tetrapoda)

* **

*segmental sternum

**solid sternum

Human Pectoral Skeleton

claviclesupra-sternalnotch

acromion

Clavicle – (collar bone) large, connects acromion process of scapula and superior sternum; dermal

Scapula – (shoulder blade; endochondral

Acromion process – contacts clavicle

Coracoid process

Glenoid fossa

Scapular blade

Scapular spine

Human Pectoral Girdle

coracoid process

Human Scapulaacromion

acromion

coracoid process

glenoid fossa

coracoidprocess

scapularblade

scapularspine

Human Arm Bones

olecranon processof ulna

styloid processof ulna

lateral epicondyleof humerus

Human Arm External

Human Hand (Manus)

I

III IIIV

V

pisiform

Human Hand (Manus) Bones

Human Hand External

Human Pelvic Skeleton

Innominate Bone – pelvis; 3 pairs bones; connects to sacral vertebrae; endochondral

Ilium – fused to sacrum

Ischium – posterior & inferior

Pubis – anterior & inferior

Obturator foramen – btw. pubis & ischium

Acetabulum – femur

articulates

Human Pevic Girdle

Human Pelvic Girdle

ilium sacrumcoccyx

ischiumobturatorforamen

acetabulum

pubis

iliac crest(iliac spine)

Human Pelvis External

iliac crest(iliac spine)

Human Leg Bones

Human Leg External

patella

tibial tuberosity

lateral epicondyleof femur

medial epicondyleof femur

tibial shaft (“shin”)

headof fibula

Human Pes

Human Foot (Pes) Bones

Pectoral girdle =cartilaginous scapulocoracoid

Pelvic girdle = cartilaginous puboischiac bar

Radials = support keratinous “fin rays”

--Only Gnathostomes Have--Chondrichthyan Pectoral & Pelvic

scapulocoracoid puboischiac bar

radials

Scapulocoracoid (or scapula & coracoid) = endochondral; articulate(s) with radials (also endochondral)

Extensive, dermal pectoral girdle

Posttemporal, supracleithrum, cleithrum, clavicle, and interclavicle (median & unpaired)

Fin rays = dermal bony rods (support most of fin); modified lamellar bone “scales”

Osteichthyan Pectoral Girdles

Radials

Scapulo-coracoid

Osteichthyan Pectoral Girdle

Lepido-trichia

Cleithrum

Supracleithrum

Posttemporal

ClavicleInterclavicle

Actinopterygiians - loss of ventral dermal bones (Teleosts & Amia lack clavicles & interclavicles. Gars lack interclavicles, but have clavicles.)

Tetrapods - loss of dorsal dermal bones

(lack posttemporal, supracleithrum, & cleithrum)

Humerus = single radial articulates with “scapulocoracoid” in sarcopterygiians. (Glenoid fossa = articulation point) In Tetrapods - Humerus Radius & Ulna Carpals Metacarpals Phalanges

Osteichthyan Pectoral Girdles

Tetrapod Pectoral Appendages

Coracoid

Scapula

Clavicle

Interclavicle

Humerus

Radius

Ulna

Carpals

Metacarpals

Phalanges

Glenoidfossa

Clavicles & interclavicle in turtle ventral shell.

furcula = fused clavicles & interclavicle in birds.

postcoracoid = endochondral ossification unique to mammals; fuses to scapula in therians (= coracoid process of scapula)

Therian mammals lack interclavicle and coracoid.

Amniote Pectoral Girdles

Echidna Skeleton

Dermal Pectoral GirdleGroup inter-

clavicleclavicle cleithrum supra-

cleithrumpost-

temporal

reedfishes and sturgeons

present present present present present

gars absent present present present present

teleosts & Amia absent absent present present present

lungfishes present present present present absent

amphibians present present absent absent absent

monotremes present present absent absent absent

Theria absent present absent absent absent

turtles, birds, & lizards/snakes

present present absent absent absent

crocodilians present absent absent absent absent

Endochondral Pectoral GirdleGroup scapula coracoid postcoracoid

Chondrichthys present, fused to → present, fused to ← absent

reedfishes present present absent

sturgeons & paddlefish, gars, & Amia

present, fused to → present, fused to ← absent

teleosts present present absent

lungfishes present, fused to → present, fused to ← absent

amphibians presentsometimes fused to →

presentsometimes fused to ←

absent

monotremes present present present

Theria present absent present, fused to scapula (= coracoid

process)

Reptilia presentsometimes fused to →

presentsometimes fused to ←

absent

Subphylum Vertebrata

hagfis

hes

lam

preys

Chondrichth

ys

Actin

optery

gii

coel

acan

ths

lungfis

hes

amphib

ians

Mam

mal

ia

Reptil

ia

loss ofcleithrum,supracleithrum,& posttemporal(have “neck”) (Tetrapoda)

R S G AT

***

**loss of interclavicle*loss of clavicles

pectoral & pelvic appendages (Gnathostomata)

dermalpec. girdle(Osteichthys)

Subphylum Vertebrata

hagfis

hes

lam

preys

Chondrichth

ys

Actin

optery

gii

coel

acan

ths

lungfis

hes

amphib

ians

Mam

mal

ia

Reptil

ia

radius, ulna,metacarpals, (tibia, femur,metatarsals),phalanges(Tetrapoda)

humerus, (femur)

(Sarcopterygii)

Amniota

montre

mes

mar

supia

ls

euth

eria

ns

turtl

es

lizar

ds & s

nakes

croco

dylia

ns

birds

furculaclavicles &interclaviclein ventral shell

posteriorcoracoid

loss of interclavicle& anteriorcoracoid

lossof clavicles

ALL Endochondral

Not in actinopts. = radials.

3 “bones” in tetrapods.

Ilium = contacts sacral vert.

Pubis = Anterioventral

Ischium = Posterioventral

Femur = single radial articulates with plvic girdle in sarcopterygiians. (Acetabulum = articulation point)

Osteichthyan Pelvic Girdlesanterior

turtle

is

il

pu

Tetrapod Pelvic AppendagesIlium

IschiumPubis

Acetabulum

Femur

Fibula

TibiaTarsals

Metatarsals

anterior

In Archosaurs the acetabulum is “perforated.”

In birds the 3 pelvic bones fuse (innominate bone); form a synsacrum.

In mammals the 3 pelvic bones often fuse (innominate bone).

Amniote Pelvic Girdlesanterior

bird

is

ilpu

Subphylum Vertebrata

hagfis

hes

lam

preys

Chondrichth

ys

Actin

optery

gii

coel

acan

ths

lungfis

hes

amphib

ians

Mam

mal

ia

Reptil

ia

ilium, ischium, & pubis (Tetrapoda)

pelvic girdlelost; fused basal radials

pelvic girdle

Amniota

montre

mes

mar

supia

ls

euth

eria

ns

turtl

es

Lizard

s & s

nakes

croco

dilian

s

birds

synsacrum;tibiotarsus;

tarsometatarsusperforatedacetabulum (Archosauria)

Manus = “hand”

Pes = “foot”

Digits numbered anterior to posterior. Ancestrally 5 digits per limb in amniotes .

Pollux = “thumb;” digit I of manus

Hallux = “big toe;” digit I of pes

Phalangeal formula = number of phalanges in each digit starting with digit I.

(e.g., 2-3-3-3-3)

Tetrapod Digit Terminology

Ancestral Tetrapod Manusphalanges

meta-carpals

radius

ulna

ulnare

radiale

inter-medium

distal carpals

54

3

12

4 3

1

2

I

II

III

IVV

centrales

Ancestral Tetrapod Pesphalanges

meta-tarsals

tibia

fibula

fibulare

tibiale

inter-medium

distal tarsals

54

3

12

4 3

1

2

I

II

III

IVV

centrales

Human Manus

Birds: much fusion of elements

Only 2 free carpals

Carpometacarpus = distal carpals + metacarpals of digits III & IV

Tibiotarsus = tibia + proximal tarsals

Tarsometatarsus = distal tarsals + metatarsals

Bird Manus & Pes

Talus = tibiale + intermedium (called Astragalus in non-mammals)

Mammals - Maximum of only 1 free centrale (humans = 0 in manus, 1 in pes)

Pisiform = sesamoid ossification on manus

Calcaneus = fibulare with posterior process; forms heel

Amniote Manus & Pes

Genetralized Amniote Pesphalanges

meta-tarsals

tibia

fibula

Calcaneus (fibulare)

Astragalus(tibiale + intermedium)

distal tarsals

54

3

12

4 3

1

2

I

II

III

IVV

centrales

Amniota

monotre

mes

mar

supia

ls

euth

eria

ns

turtl

es

lizar

ds & s

nakes

croco

dilian

s

birds

carpometacarpus;tibiotarsus;

tarsometatarsus

calcaneus (= “heel” on fibulare);

tibia-tarsal joint (not an intratarsal joint)

astragalus / talus(= tibiale + intermedium)