Skeletal System Part 2
Axial and Appendicular Skeleton
319-321 bones in the dog
Dog Skeleton 319 – 321 bones…what accounts for the range?
Axial Skelton
•
•
•
•
•
Skull
Hyoid bone
Spinal column
Ribs
Sternum
Skull
 Usually consists of
37 or 38 separate
bones
 Most of the skull
bones are joints
called sutures.
 The mandible is
connected to the
rest of the skull
by a synovial joint.
Bones of the Cranium
External bones:
•
•
•
•
•
Frontal bones (2)
Interparietal bones (2)
Occipital bones (1)
Parietal bones (2)
Temporal bones (2)
Internal Bones:
• Ethmoid bone (1)
• Sphenoid bone (1)
Bones of the Face
External:
• Incisive bones (2)
• Lacrimal bones (2)
• Mandible (1 or 2)
• Maxillary bones (2)
• Nasal bones (2)
• Zygomatic bones (2)
Hyoid Bone
• Sometimes included with the cranial
bones
• Also called the hyoid apparatus
• Composed of several portions of bone
united by cartilage
Bones of the Ear
• Incus (2)
• Malleus (2)
• Stapes (2)
Bones of the Face
Internal:
•
•
•
•
Vomer bone (1)
Turbinates (4)
Pterygoid bones (2)
Palatine bones (2)
Vertebrae
• Consist of a body,
an arch, and
processes
• Intervertebral
disks: cartilage
separating bodies
of adjacent
vertebrae
Vertebrae
• Vertebral arches
line up to form the
spinal canal
• Vertebrae usually
contain several
processes
– Spinous process
– Transverse processes
– Articular processes
Vertebral Regions
• Cervical
– C1 atlas
– C2 axis
Vertebral Regions
•
•
•
•
Thoracic
Lumbar
Sacral
Coccygeal
Thoracolumbar joint
T 11 vertebra = spinous process is more vertical than the
others
Myelogram of spinal cord…can you see it?
Ribs
• Flat bones that
form lateral walls
of the
thorax
• Dorsal heads of
theribs articulate
with thoracic
vertebrae
Ribs
• Costal Cartilage:
ventral ends of
the ribs
• Costochondral
junction:
area where costal
cartilage meets
bony rib
Ribs
 Costal cartilages
join the sternum or
the costal cartilage
ahead of them
 Floating ribs:
cartilage does not
join anything at all
› Often end in the muscles
of the thoracic wall
Sternum
 The breastbone
 Forms the floor of the
thorax
 Composed of
sternebrae
 Manubrium sterni:
most cranial sternebra
 Xiphoid process: most
caudal sternebra
Skeleton games on computer
http://www.vet.osu.edu/assets/flash/educati
on/outreach/games/skeleton/skeleton.html
http://www.cvmbs.colostate.edu/vetneuro/i
ndex.html
Appendicular Skeleton
Thoracic Limb
•
•
•
•
•
•
Scapula
Humerus
Radius
Ulna
Carpal bones (carpus)
Metacarpal bones
• Phalanges
Scapula
 Flat, triangular bone
 Forms portion of
the shoulder joint
 Spine of the
scapula:
longitudinal ridge
on lateral surface
 Glenoid cavity:
shallow, concave
articular surface
Humerus (Brachium)
Long bone of the
brachium
Forms portion of
the shoulder joint
and elbow joint
Tubercles: processes
where shoulder
muscles attach
Humerus
 Condyles: articular
surfaces
› Trochlea: articulates
with ulna
› Capitulum: articulates
with radius
 Olecranon fossa:
indentation above
condyle
 Epicondyles: nonarticular (they are the
rounded features)
HUMERUS
Antebrachium
Radius
• Main weight-bearing bone of the antebrachium
• Articulates with humerus and ulna
• Styloid process articulates with carpus
Antebrachium
Ulna
• Olecranon process
– Point of the elbow
– Site for tendon attachment of triceps brachii muscle
• Trochlear notch: concave articular surface
• Anconeal and coronoid processes
Elbow Joint
Canine Forelimb (elbow)
– Humerus, radius, ulna- how do they fit together?
Carpus
Two rows of carpal bones
• Proximal row bones are
named (“radial carpal
bone,” “ulnar carpal
bone,” etc.)
• Distal row bones are
numbered medial to lateral
Carpal Bones
2 parallel rows
• Proximal Carpal Bones
– Radial/intermediate carpal
– Ulnar carpal
– Accessory carpal
• Distal Carpal Bones
– First carpal (medial)
– Second carpal
– Third carpal
– Fourth carpal
Metacarpal Bones
Extend distally from
distal carpal bones
to proximal phalanges
• Dogs & cats - 5 digits
– Numbered medial to
lateral
– Metacarpal I: dewclaw
Thoracic Limb Phalanges - Canine and
Feline
 Digit I (dewclaw):
one proximal and
one distal phalanx
 Digits II to V: a
proximal, a middle,
and a distal phalanx
› Ungual process –
surrounds the claw
on distal phalanx
Metacarpal Bones
• Horses
› One large
metacarpal bone
(cannon bone)
› Two smaller
vestigial
metacarpal bones
(splint bones)
 Non weightbearing
Thoracic Limb Phalanges - Equine
 1 digit with 3 phalanges
1. Proximal phalanx
(long pastern bone)
2. Middle phalanx
(short pastern
bone)
3. Distal phalanx
(coffin bone)
 Also have sesamoid
bones
Thoracic Limb Phalanges - Bovine
 Four digits on each
limb
 Two support weight,
two are vestigial
(dewclaws)
 Each digit has a
proximal, middle,
and distal phalanx
 Also proximal distal
sesamoid bones
Metacarpal Bones
• Cattle
– Two fused
metacarpal
bones (bones III
and IV)
Appendicular Skeleton
Pelvic Limb:
 Pelvis
› Ilium
› Ischium
› Pubis






Femur
Tibia
Fibula
Tarsal bones (tarsus)
Metatarsal bones
Phalanges
•
Connected to the axial skeleton
at the sacroiliac joint
Pelvis
• 3 fused bones
– Ilium
– Ischium
– pubis
• Pelvic symphysis:
cartilaginous joint
between the two halves
of the pelvis
Pelvis
• Ilium
– Projects in dorsocranial direction
– Forms sacroiliac joint with the sacrum
• Ischium
– Caudalmost pelvic bone
– Forms caudal portion of the pelvic floor
• Pubis
– Forms cranial portion of the pelvic floor
Femur
• Proximal end forms
part of hip joint
• Femoral head fits
deeply into acetabulum
of pelvis
• Trochanters: processes
where hip and thigh
muscles attach
Femur
Shaft extends downward
to form the stifle joint
with patella & tibia
Articular surfaces:
› 2 condyles
› trochlea
Trochlea: articular
groove containing
the patella
Patella and Fabellae
Patella
Fabellae
• Large sesamoid bone
• Formed in the distal
tendon of the
quadriceps femoris
muscle
• Protects the tendon
• Two small sesamoid
bones in proximal
gastrocnemius muscle
tendons of dogs and
cats
• Not present in cattle or
horses
Tibia
Main weight-bearing
bone
of lower limb
Forms the stifle joint
with the
femur, the hock with the
tarsus
Tibial tuberosity
Tibial crest
Dog
Horse
Fibula
• Parallel to tibia
• Not weight-bearing
• Serves as a muscle
attachment site
• Lateral malleolus: knob-like
process
Tarsus
• Hock
• 2 rows of tarsal bones
› Proximal row is named;
distal row is numbered
medial to lateral
• Calcaneal tuberosity:
point of attachment
for the tendon of the
gastrocnemius muscle
Metatarsal Bones
Dogs & cats: four
metatarsal bones
(II to V)
Horses: one large
metatarsal bone
(cannon bone)
and two small
metatarsal bones
(the splint bones)
Pelvic Limb Phalanges
• Similar to thoracic limb phalanges
• Exceptions: dogs and cats
– Usually only 4 digits (II to V)
Visceral Skeleton
• Bones that form in organs
• Examples
– os cordis: in heart of cattle and sheep
– os penis: in penis of dogs, beaver, raccoons, and walruses
– os rostri: in nose of swine
Joints
Three general classifications:
1. Fibrous joints: immovable
2. Cartilaginous joints: slightly movable
3. Synovial joints: freely movable
Fibrous Joints
• Synarthroses (archaic
term)
• United by fibrous
tissue
• Examples: sutures
of skull, splint bones
of horses
Cartilaginous Joints
• Amphiarthroses (archaic term)
• Capable of slight rocking movement
• Examples: mandibular symphysis, pubic
symphysis, intervertebral disks
Synovial Joints
Diarthroses (archaic term)
Components
› Articular surfaces on bones
› Articular cartilage (hyaline) covering
articular surfaces
› Fluid-filled joint cavity enclosed by a joint
capsule
 Synovial membrane
 Synovial fluid
› Ligaments - fibrous connective tissue
Synovial Joint Movements
•
•
•
•
•
•
Flexion
Extension
Adduction
Abduction
Rotation
Circumduction
Synovial Joint Movements
Flexion and Extension
• Opposite movements
• Increase or decrease the angle between two bones
Synovial Joint Movements
Adduction and Abduction
• Opposite movements
• Move an extremity toward or away from medial plane
Synovial Joint Movements
Rotation
• Twisting movement of
a part on its own axis
Circumduction
• Movement of an
extremity so that the
distal end moves in
a circle
Types of Synovial Joints
•
•
•
•
Hinge joints
Gliding joints
Pivot joints
Ball-and-socket joints
Hinge Joints
• Ginglymus joints
• One joint surface
swivels around
another
• Only capable of
flexion and
extension
• Example: elbow
joint
Gliding Joints
 Arthrodial joints
 Rocking motion of
one joint surface on
the other
 Primarily capable of
flexion and
extension
 Abduction and
adduction possible
 Example: carpus
Pivot Joints
• Trochoid joints
• One bone pivots
(rotates) on
another
• Only capable of
rotation
• Example: the
atlantoaxial joint
Ball-and-Socket Joints
• Spheroidal joints
• Allow for all joint
movements
• Examples:
shoulder and hip
joints