Skeletal System
Introduction to Veterinary Science
The Musculoskeletal System
• The musculoskeletal system consists of two
systems that work together to support the
body and allow for movement of the animal:
▫ the skeletal system = bones, joints, cartilage,
and various connective tissues
▫ the muscular system = muscles and various
connective tissues
What is the function of bone?
• Bone helps with:
▫ Movement
▫ Support
▫ Protection
▫ Blood cell
formation
Bones
• Bones start as cartilage and fibrous membranes
that harden into bone before birth.
▫ The formation of bone from fibrous tissue is known
as ossification.
 Osteoblasts produce bone
tissue
 Osteocytes maintain
bone tissue
 Osteoclasts break
or phagocytize bone tissue
Bones build up and break down
throughout life and has ability to
repair and heal.
Important Terms Related to the
Skeleton
The skeleton can be divided into
two parts
•
Axial Skeleton
•
Appendicular skeleton
Other Important Terms, Con't.
•
Joints—points where two or
more bones meet.
Cartilage



protects the ends of bones
provides a cushion
Other Important Terms, Con't.
•
Ligament—Tough band of connective tissue
connecting one bone to another.
•
Tendon—Thick band of connective tissue that
attaches muscle to bone.
Types of Bone
•
Bone is one of the hardest tissues of the body
▫
▫
Connective tissue
Only thing harder-tooth enamel
•
Compact Bone—layer of protective hard bone
tissue surrounding every bone
•
Cancellous Bone—soft bone filled with many
holes and spaces surrounded by hard bone.
Combining forms for Bone
• Oste/o
• Oss/e
• Oss/i
• Osteoarthritis
• Ossification
Classification of bones
•
•
•
•
Long bones
Short bones
Flat bones
Irregular Bones
Long Bone
• Long bones consist of a shaft, two ends, and a
marrow cavity.
▫
▫
▫
▫
Femur
Humerus
Tibia
Radius
• Red bone marrow is hematopoietic and is found
at the ends of long bones and in flat bones
(hemato-blood/ -poietic pertaining to formation)
▫ Red bone marrow produces red blood cells, white
blood cells, platelets
▫ Yellow bone marrow replaces red bone marrow
(mostly fat cells)
• Flat bones - thin flat bones: pelvis, ribs, scapula,
bones of the skull
▫ Flat bones are made up of a layer of spongy bone
between two thin layers of compact bone
• Short bone- cube shaped, no marrow
▫ Carpal bones
▫ Tarsal Bones
• Pneumatic bones- sinus containing bones
(frontal)
Irregular Bones
• Vertebrae-make up the spine
• Sesamoid bones- small, embedded in a tendon:
▫ Dog: patella, fabellae (2)
▫ Horse: proximal sesamoids (2) and navicular bone
FACT:
• The average dog has about 320 bones…
134 in the axial skeletonthe skull has 50 flat bones!
186 in the appendicular skeleton
The average horse has about 205 bones
Bones of the Axial Skeleton
The axial skeleton protects the major organs of the
nervous, respiratory, and circulatory systems.
•
•
•
•
Skull
Vertebrae
Ribs
Sternum
Cranium Bones and Face Bones
Occipital bone
Occipital
Parietal
Frontal
Temporal
Zygomatic Arch
Nasal
Incisive
parietal
frontal
nasal
incisive
Zygomatic arch
•
•
•
•
•
•
•
Short, Average, Long
Vertebral Column
• The vertebral column supports the head and body and provides
protection for the spinal cord.
• The vertebral column is comprised of individual bones called
vertebra.
▫ The combining forms for vertebra are spondyl/o and
vertebr/o.
▫ Vertebrae is the plural form.
Horse C7 T18 L6 S5 Cd 15-21
Dog C7 T13 L7 S3 Cd 20
Cat C7 T13 L7 S3 Cd 14-23
Parts of a Vertebra
• Vertebrae are divided
into parts:
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▫
▫
▫
▫
body
arch
lamina
vertebral foramen
processes
 spinous process
 transverse process
 articular process
Other Axial Skeleton Parts
• Ribs
▫
▫
▫
▫
Combining form is cost/o.
Are flat bones
Attached by cartilage
Purpose to protect
• Sternum
▫
▫
▫
▫
Manubrium, body, xiphoid
sternebrae
xiphoid process (caudal-most sternebra)
Flat bones and cartiligenous
Make up the boundaries of the thoracic cavity (protects
heart and lungs)
Bones of the Appendicular Skeleton
• The appendicular skeleton includes the bones of the
front and hind limbs
• Front Limb
•
•
•
•
•
•
•
Scapula
Humerus
Radius
Ulna
Carpal bones
Metacarpal bones
Phalanges
• Hind Limb
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▫
▫
▫
▫
▫
▫
Pelvis
Femur
Tibia
Fibula
Tarsal bones
Metatarsal bones
Phalanges
The Appendicular Skeleton
• Front limb
▫
▫
▫
▫
▫
▫
▫
scapula
clavicle
humerus
radius
ulna
carpal bones
metacarpal bones
 cannon bone in livestock
▫ Phalanges
 Differ in dog, horse, ungulates (cloven
hoof)
Forelimb
• Scapula
(Ball and socket joint)
• Humerus
• Radius and Ulna
• Carpal Bones
▫ Metacarpals
▫ Phalanges
Ball and Socket joint Scapula and
Humerus – Point of Shoulder
“Elbow” joint
Hinge joint between Humerus and the Radius/ Ulna AND
Pivot Joint
The Appendicular Skeleton
• Phalanx names:
▫ Proximal = long pastern
bone in livestock
▫ Medial = short pastern
bone in livestock
▫ Distal = coffin bone in
livestock
▫ Distal in small animals
may be called the claw or
nail. In cats the claw
cannot be separated from
the phalanx bone.
 Combining form
for claw or nail
is onych/o.
Phalanges
• Dog:
▫ 3 phalanges
 proximal, middle, distal
▫ 5 digits I-V
 Start medial to lateral
 Medial digit is digit I
 (the dewclaw in dogs)
Phalanx
• Horse
▫ One digit (III)
▫ 3 phalanx bones
Fetlock
joint
Cloven hoof
•Cloven hoofed animals
•Two digits (III-IV)
•Three phalanx bones
•Digits II and V are
vestiges
•Distal phalanx is
encased in a hoof.
The Hind Limb
• Hind limb
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▫
▫
▫
▫
▫
▫
pelvis
femur
patella
tibia
fibula
tarsal bones
metatarsal bones
 cannon bone in livestock
▫ phalanges
Pelvic Bones
• The bones of the
pelvis:
▫
▫
▫
▫
ilium
ischium
pubis
acetabulum—
bony part
of the socket
joint
Cat skeleton:
Where is the Clavicle
Owl Skeleton
Horse Skeleton
Unlabeled Horse Skeleton
Veterinary Medicine of Bones
Bone problems –
Pathological conditions
• Hip dysplasia
• Invertebral disc disease
▫ Herniated disc
▫ Ruptured disc
▫ IVDD
• Osteochondrosis dissecans
▫ OCD
• Osteoarthritis
Degenerative Joint Disease / DJD
• Spondylosis
• Luxation and Subluxation (complete vs partial)
IVD – invertebral disc disease
• Can happen
suddenly or
slowly
• Can cause
paralysis
• CT junction
• TL junction
• Breed
propensity
• Treatment
Spondylosis
Osteochonditis Dissecans - OCD
Luxating Patella
Hip Dysplasia
Normal hip joint
Hip Joint = Coxofemoral joint
Subluxation = femoral head slips in and out of
acetabulum
FHO –Femoral Head Ostectomy
Fracture terminology
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•
•
•
•
Closed Fracture/ Simple
Open Fracture/ Compound
Manipulation/ Reduction-realignment of bone
Immobilization-holding in a fixed position
Crepitation-cracking sensation (felt and heard)
• Surgical Procedure:
▫ Osteotomy-cutting into a bone
▫ Ostectomy-removal of a bone –FHO
(Femoral Head Ostectomy)
Fractures
Comminuted fracture
-cat radius and ulna
Femur Fracture and Repair
Femur- Pinned
Structures
• Bones are not smooth and have bumps, ridges,
grooves,etc
▫ Foramen-hole (Infraorbital foramen, magnum foramen,
obturator foramen)
▫ Condyle-rounded projection
▫ Process-projection (spinous process, xiphoid process)
▫ Aperture-opening
▫ Canal – tunnel (Haversian Canal)
▫ Crest - high projection or border projection (sagittal crest)
▫ Fossa-trench or hollow depressed area (trochanteric fossa
of femur, supraspinatous fossa)
▫ Head- major protrusion, round, spherical (femoral head)
▫ Lamina-thin, flat plate
More bumps, ridges and grooves
▫ Sinus-space or cavity
▫ Spine-sharp projection (spine of the scapula)
▫ Sulcus-groove (gingival sulcus, radial sulcus on humerus
for radial nerve)
▫ Suture-seam (skull)
▫ Trochanter-broad flat projection (greater
trochanter/lesser trochanter on the femur)
▫ Trochlea-pulley shaped structure in which other
structures pass or articulate (patella sits in a trochlea)
▫ Tuberosity-projecting part (iliac tuberosity, ishiatic
tuberosity)
▫ Facet-smooth area
▫ Fovea-small pit (fovea capitus…head of the femur)
Femur
The Muscular System
• Muscles are tissues that contract to produce
movement.
• Muscles are responsible for the following:
▫
▫
▫
▫
ambulation
control of organs and tissues
pumping of blood
generation of heat
Muscles
• Muscles are made up of long, slender cells
called muscle fibers.
• Each muscle consists of a group of muscle
fibers in a fibrous sheath.
▫ My/o is the combining form for muscle.
▫ Fibr/o and fibros/o are combining forms for
fibrous tissue.
Types of Muscle Tissue
SKELETAL MUSCLE TISSUE
Voluntary = conscious thought
Striated = striped
Muscle cell = many nuclei and mitochondria
Types of Muscle Tissue
CARDIAC MUSCLE
Involuntary = unconscious thought
Striated = striped
Intercalated Discs
Types of Muscle Tissue
SMOOTH MUSCLE
Involuntary
Not striated
Examples: Urinary bladder, walls of the stomach, blood vessels
Structures Associated
with Muscles
• Fascia
is a sheet of fibrous connective tissue that
covers, supports, and separates muscles.
▫ Fasci/o and fasc/i are combining forms for
fascia.
▫ Plural is fasiae
Structures Associated
with Muscles
• Tendons
are fibrous connective tissues that connect muscle to
bone (or other structures).
▫ Tend/o, tendin/o, and ten/o are combining forms for
tendon.
▫ Linea Alba
apponeuroses that connects abdominal muscles to the
abdominal wall
Nuchal Ligament
• Ligament: Connects bone to bone
The nuchal ligament
Origin: cervical vertebrae and the
skull
Insertion: dorsal spinous process
of the fourth thoracic vertebra
Origin and Insertion
• Muscle Origin- place where a muscle begins
attached / the part (or end) of the muscle closest to
midline. (Tends to be relatively fixed)
• Muscle Insertion- place where a muscle ends
is more moveable, is portion of the muscle farthest from midline
Muscles may be named according to where they originate
and end.
Brachioradialis muscles are connected to the brachium
(humerus) and to the radius.
Muscle Terms
 Kinesiology
is the study of movement.
▫ Kinesio/o and -kinesis mean movement.
• Antagonistic muscles work against or opposite
other muscles.
▫ anti- = against
▫ agon = struggle
 Synergist
muscles work with other muscles
to produce movement.
▫ syn = together
▫ erg = work
Superficial muscles of the dog
• Head and Neck
▫ Masseter, Brachiocephalicus, Trapezius,
• Thoracic Limb (front limb)
▫ Deltoid, Biceps Brachii, Triceps Brachii,
Latissimus Dorsi, Pectoral
• Abdominal muscles
▫ External Abdominal Oblique, Intercostal
• Pelvic Limb (back limb)
▫ Gluteal, Biceps femoris, semitendinus,
gastrocnemius
86
Masseter
Brachiocephalicu
s
Trapezius
Anatomy &
Physiology
TM
Latissimus
dorsi
External abdominal
oblique
Gluteals
Pectorals
Semitendino
us
Deltoid
Triceps
brachii
Gastrocnemi
us
Intercostal Biceps
femoris
Naming Muscles
• Muscle movement terms:
▫ Abductor-muscle that moves a part away from
midline
 Adductor-
▫ Flexor-muscle that bends a limb at its joint or
decreases the joint angle.
 Extensor-
▫ Levator-raises or elevates a part
 Depressor-
▫ Rotator-muscle that turns a body part on its axis
▫ Supinator-muscle that rotates the palmer or
plantar surface upward
 Pronator-
Naming Muscles
• Muscle location terms:
▫
▫
▫
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Pectoral-chest
Epaxial-above the pelvic axis
Intercostal-between ribs
Infraspinatus-beneath the spine of the scapula
Supraspinatus-above the spine of the scapula
▫ Inferior-below or deep, Medius-middle, Superior-above
▫ Externus-outer vs internus- inner
▫ Orbicularis-surrounding another structure
Naming Muscles
• Muscle fiber directional terms:
▫ Rectus-straight/ align with the vertical axis
(rectus abdominus)
▫ Oblique-slanted-slant outward away from midline
(external abdominal oblique muscles)
▫ Transverse- crosswise- crosswise to the midline
(transversus abdominus muscle)
▫ Sphincter- tight band-ringlike and constrict
(Urinary sphincter)
• Number of muscle division terms:
▫ biceps
▫ triceps
▫ quadriceps
Naming Muscles
• Muscle size terms:
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▫
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Minimus
Maximus (Vastus)
Major
Minor
Latissimus
Longissimus (Gracilis)
Naming Muscles
• Muscle shape terms:
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▫
Deltoid – delta
Quadratus – square/ four sided
Rhomboideus- diamond shape
Scalenus- unequal three sided
Serratus – sawtoothed/notched
Teres - cylindrical
Latissimus
dorsi
deltoid
triceps
biceps
Abdominal
obliques
pectorals
Pathological conditions for the
Musculoskeletal System
• Ataxia - lack of voluntary control of muscle
movement
• Atonic - lacking muscle control
• Dystrophy - defective growth
• Fibroma - tumor composed of fibrous connective
tissue
• Hernia - protrusion of an organ or fascia through
the wall of the cavity that normally contains it
• Myopathy- abnormal condition of disease of muscle
• Tetany – muscle spasms or twitching
Ataxia-lack of
voluntary control
of muscle
movement
“wobbliness”
Tetanymuscle spasms
or twitiching