Skeletal System
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What is it?
 Framework of structures
 Made of bones & cartilage
 Supports & protects the body
 Axial Skeleton
 Includes skull, vertebrae, ribs, and sternum
Axial Skeleton
 Skull
 Many plates of bones fused together
 Soft spot on top of skull

Fontanel
 Vertebrae
 Five distinct regions
Cervical
 Thoracic
 Lumbar
 Sacral
 Coccygeal

Cervical
 Vertebrae of the neck region

Atlas  called “C1”, the first cervical vertebra


Axis  called “C2”, the second cervical vertebra


Forms joint that lets you nod “yes”
Forms joint that lets you nod “no”
7 cervical vertebrae in all mammals
Thoracic
 Vertebrae of the body region, always have a rib
attached and a spine on top
 “True ribs”
 Directly attached to sternum with cartilage
 “False ribs”
 Connect to each other with cartilage, not the sternum
 “Floating ribs”
 Seen in the dog, have cartilage on the tips but do not attach to
anything
Lumbar
 Vertebrae of the lower back
 Carnivores tend to have more – greater flexibility
 Herbivores need to have short, strong back to
support large digestive and reproductive organs
Sacral
 Vertebrae of the pelvic region
 Fused together on the ventral side
 Herbivores generally have more to add strength &
support to the back.
 Carnivores less for flexibility
Coccygeal
 Vertebrae of the tail region
 Used for balance
 Become smaller at the end of the tail
Appendicular Skeleton
 The fore and hind limbs
 Forelimb
 Scapula- shoulder blade attached with muscle

Clavicle


Humerus


Cat is the only domestic animal with a clavicle
Forms the upper arm
Ulna

Forms the elbow joint, fused with the radius in herbivores
Appendicular Skeleton
 Forelimb
 Radius- forms the forearm

Carpus


Commonly called the “knee” in horses, the “wrist” in dogs and
humans
Metacarpals- commonly called the cannon region of the
forelimb
Appendicular Skeleton
 Metacarpals
Number depends on species:
 Humans: 5
 Horses: 1 plus 2 accessory metacarpals, called splint bones
 Dogs & Cats: 4 plus the dewclaw
 Cattle: 1 that splits at bottom into a cloven hoof & 2 dewclaws
 Pigs: 4 (2 toes & 2 dewclaws)
Appendicular Skeleton
 Forelimb

Proximal phalanx (P1)

Bones of the finger, hoof, and claw

Intermediate phalanx (P2)

Distal phalanx (P3)


Proximal sesamoids


The coffin bone in horses
Tucked in behind P1
Distal sesamoid

Tucked in underneath P3
Appendicular Skeleton
 Hind Limb
 Pelvis



Tuber coxae-part of pelvis that forms the “point of hip”

Ischiatic tuberosity-part of pelvis that forms the “seat bones”
Femur
Patella


Forms the “stifle” joint in horses, knee in dogs or humans
Tibia

Main bone of the gaskin of the horse
Appendicular Skeleton
 Hind Limb
 Fibula


Tarsus



Fused with the tibia & considered vestigial in herbivores
Commonly called “hock”
Human ankle
Metatarsal

Cannon region in the hind limb. Number depends on species

P1

P2

P3

Proximal & distal sesamoids
Axis
Skull
Vertebrae
Cervical
Sacral
Thoracic Lumbar
Coccygeal
Atlas
Scapula
Pelvis
Humerus
Olecranon
Radius
Carpals
Phalange
s
Femur
Patella
Fibula
Ribs
Tibia
Tarsals
Metatarsals
Phalange
s
Metacarpal
s
Ulna
Sesamoids
Classification of Bones
 Short Bone

Cube shaped (carpus & tarsus)
 Flat Bone

Plate of bone (scapula, rib, skull)
 Irregular Bone

Complex shaped (vertebrae)
 Sesamoid

Small, seed-shaped bone (proximal & distal sesamoids, patella)
 Long Bone

Bone is longer than it is wide (femur, tibia, humerus)
Bone Anatomy
 Diaphysis

Body of a long bone
 Epiphysis

Enlarged ends of long bones
 Metaphysis

Joining point of diaphysis & epiphysis
 Medullary Cavity

Space within bone filled with marrow
 Endosteum

Thin inner protective layer lining the medullary cavity
Epiphysis
Diaphysis
Periosteum
Medullary cavity
Metaphysis
Bone
marrow
Endosteum
Bone Growth
 Occurs in the epiphysis of long bones
 Epiphyseal growth plates produce cartilage, which
gradually turns into bone via a process called
ossification.
Fractures
 Simple
 Bone does not break skin
 Compound
 Bone breaks through skin, much more serious
 Complete
 Fracture goes completely across the bone.
 Incomplete
 Fracture does not go completely across bone.
Classifying Fractures
 Fissure fracture

Incomplete break, along the long axis of the bone
 Greenstick fracture

Incomplete break on one side of a bone, usually due to a bending
force
 Transverse fracture

Break across the bone
 Comminuted fracture

Bone shatters into many pieces
Fissured
Greenstick
Transverse
Comminuted