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The Equine Skeletal System

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on 5 January 2015

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Transcript of The Equine Skeletal System

Lecture Content
Equine Skeleton
Strong framework that:
Directional Terms
Scientific / anatomical nomenclature
Common language
Quick and succinct identification
CRITICAL that you learn these and practice using them- written and orally
The Equine Skeletal System
Sarah Lacy
The Appendicular Skeleton
C/o Pleasantvalleyhorsefarm.com
1) Introduction to Anatomy & Physiology
2) Directional terms
3) Species comparison
4) Axial and appendicular skeleton
Anatomy & Physiology
Deals with

Deals with the normal function of the body
Why Study A & P?
Compare between normal and abnormal structure and function:
Normal= anatomy and physiology
Abnormal= disease (pathology)
Anatomical features reflect body conformation
Athletic performance
Soundness/ lameness
Understanding of physical limitations
Form vs. function
Examples in context
The spinal column is
to the abdomen= above
There are more grey hairs in the
region of the head= towards the muzzle
The crack is on the dorsal wall of the hoof
The fracture is at the distal aspect of the femur
Can combine 2 terms, eg. the distomedial aspect of the cannon bone
C/o farriergodmother.com
C/o Berkeleybop.com
Supports the body
Protects muscles and vital organs
Facilitates movement
Provides attachment for tendons and muscles
Made of bone- approx. 205 bone
Production and storage of red blood cells
Functions of bone
Storage for fats and minerals
The Axial Skeleton
Heaviest bone in body
Protects the brain
Weight lessened by sinuses
Consists of:
Maxilla- long upper bone
Mandible- lower jaw bone
Specialised adaptation
Large and weighty skull and long neck aids balance
34 flat and irregular bones connected by fibrous joints
4 cavities:
1) Cranium- houses brain
2) Orbital cavity- surrounds + protects the eye
3) Oral cavities
4) Nasal cavities
Enlarged maxilla
House nerves, blood vessels and muscles
C/o Pleasantvalleyhorsefarm.com
Skull attaches to spine at atlas via occipital bone
Atlanto-occipital Joint

Skull+spinal column+ribs
Temporomandibular Joint
C/o Horse360.com.au
Synovial joint

Mandible attaches to skull just below base of each ear at temporal bone

Allow mouth to open and close
Facilitate chewing in elliptical movement
The Vertebral Column
Spinal column= 54 bones made up of:
7 cervical (neck) vertebrae
18 thoracic (chest) v
6 lumbar (loin) v
5 sacral (croup) fused v
18 coccygeal (tail) v
= singular
= plural
Coccygeal v. vary from 15-25 (breed dependent)
Each vertebra separated by 185 fibro-cartilaginous and synovial joints
1) Protect spinal cord
2) Provide areas for muscle and ligament attachment
3) Protect main aorta
4) Protect internal organs eg. kidneys
5) Provide strength for suspension of the torso
C/o Research.vet.upenn.edu
Anatomically flexible, functionally rigid- lateral and longitudinal
Structural plan

Vertebral body
Articular Processes
Vertebral Foramen/ canal
Transverse Processes
Spinous Processes
Comparatively rigid region
Why? shape of interconnecting articular processes and strong fibro-cartilaginous joints that restrict movement
This strength allows us to ride our horses
Thoracic DSPs are longest at withers
DSPs provide attachment and leverage for muscles- act as fulcrum for nucal and supraspinous ligaments- influence head and neck position
18 pairs of ribs attach to the 18 TV via synovial joints
C/o Chestofbooks.com
"Tail" vertebrae

Contribution to movement is negligable

Articular processes and neural canals not present beyond C3

Terminal bones merely short rods united by cartilaginous discs

Position linked with body language, general health, various physiological states- can indicate pathology in cranial areas of spinal column
C/o Rodnikkel.com
Jean-Marie Denoix
Flexion and extension associated with cranial thoracic area
Rotation and lateral flexion possible in mid-thoracic
Flexion and extension are normal in the thoracolumbar junction
Lumbosacral area specialised in its flexion/ extension movement. Rotation and lateral movement do not occur here. Less overall movement in lumbar area
Thehorse.com, 2001
Irregular bones
Common features, vary in size and shape according to position and function
Dorsal view of C1-2
Nuchal ligament runs along nuchal crest from occipital bone-dorsal spinous processes of T3-8
Hinge Joint
Atlanto-axial joint
Protection for heart and lungs, liver, stomach etc.
Flexible- expansion and contraction with inhalation and expiration
Contribute to bend- closer on inside, further apart on outside of bend
C/o Horsesinsideout.com
L1-6 are flatter, wider, heavier than TV
Least flexible area
Large, horizontal transverse processes- extensive area for muscle attachment, offering strength and stability
Power transmitted through LV from hind end
Lateral movement decreases as you move caudally
Injury prone area- myopathy
5 fused vertebrae
Functions as one bone
S1 specialized
C/o Rodnikkel.com
Lumbo-sacral Junction
Between lumbar and sacral v.
Hinge Joint
LSJ allows pelvis to 'tilt', role in allowing hind limbs under body during jumping and high level dressage movements
Highly flexible
Absorption and transfer of forces
Subject to concussion
Edward Gal & Moorlands Totilas
WEG Grand Prix Freestyle
London 2012 Jumping Horses
Centaur Biomechanics

Impinging DSPs (kissing spines)
Wobblers Syndrome
Facet Joint Arthritis
18 on each side
8 sternal (true) attached directly by individual cartilainous attachment to the sternum
10 asternal (false) ribs attached by cartilage at the distal end to the rib in front
The Forelimb
Load bearing
No bony attachment to thorax
Top part cartilaginous + spine provide area for muscle attachment
Large, triangular flat bone
Partially covers first 6-7 ribs- muscles and loose connective tissue allow free movement
Ideal orientation 45 degrees
Thorax slung between scapulae by
serratus ventralis
Meets humerus at shoulder joint
(Ball and socket)
One of strongest bones
Angled to absorb shock
Has various specialised indentations
Greater tubercle
Elbow joint
Radius & Ulna
Equivalent to our lower arm
Radius is larger bone running full length of the forearm
Ulna attached to upper end of radius forming part of the elbow joint
Olecranon process acts as a lever arm for extensor (triceps) muscles of the elbow
United by ligament during growth- ossification into adulthood
The Carpus
Equivalent to human wrist
6 bones arranged in 2 layers- 7th bone (accessory carpal bone) located at the posterior
Comprises multiple, synovial hinged joints
Allows flexion, extension,minor amount of lateral movement between upper and lower forelimb
The Metacarpal Bones
Equine forelimb contains 3 metacarpal bones
Equivalent of human palm
The large 3rd metacarpal (cannon) provides the major support of body weight
2nd and 4th metacarpals (splint bones) placed medially and laterally respectively-
2nd and 4th metacarpals are joined to 3rd by fibrous tissue
The Phalanges

First Phalanx
Long pastern/ PI/ Proximal phalanx
Lies distal to 3rd metacarpal bone...
...forms condylar metacarpophalangeal joint
Undergoes large motion in extension (dorsiflexion)
Common digital extensor and superficial digital flexor tendon attach to PI
Second Phalanx
Short pastern/ PII/ Middle phalanx
Forms proximal interphalgeal joint (pastern joint) with PI
Half inside, half outside hoof cavity
Supported along posterior surface by DDFT
Not orientated vertically
Third Phalanx
PIII/ distal phalanx/ pedal/ coffin bone
Completely encased by hoof capsule
Articulates with PII and distal sesamoid...
...forms distal interphalangeal joint (coffin joint)
The Sesamoid Bones

Paired bones, lies palmer to metacarpophalangeal joint
Joined by intersesamoidean ligament
Covered by hyaline cartilage

Proximal Sesamoids
Distal Sesamoid
Covered by fibrocartilage
"Navicular bone"
Articulates closely with PIII, connected by the Impar ligament

The Hindlimb

(Pelvic limb)
The Pelvic Girdle
2 symmetric halves- combine with sacrum and first 3 coccygeal vertebrae to form the pelvis
Upper portion attached to sacrum is Ilium
Front portion is the pubis
Rear portion is the ishium
These form an articular cavity- acetabulum (houses head of femur)
Outermost portion of the ilium is the tuber coxae
The Femur
One of leanest and strongest bones
Specially adapted
Diagram shows left equine femur, caudal aspect
Meets both patella (femoropatella joint) and the tibia (femorotibial joint)
The Fibula and Tibia
Tibia= main bone of second thigh
Fibula= very thin, no distal attachment, but fibula still involved in stifle joint
6 bones bound by ligaments in the joint capsule

3 rows of wedge, flattened or cuboidal bones
Bones of distal row articulate with the metatarsal bones
Tuber calcis forms lever arm
Metatarsal, phalangeal and sesamoid bones
As with forelimb
To do list...
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Work hard on learning directional terminology

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