equine anatomy

basic components of life

• organic compounds

  • carbon (C), oxygen (O), and hydrogen (H) are basic building blocks

  • carbohydrates, lipids, and proteins

tissue

group of similar cells

organ

group of similar tissues functioning together

system

group of organs with similar function

digestive system

breaks down and absorbs nutrients from food

skin and coat

• protection

• synthesis of vitamin D

• temperature regulation (sweating)

  • anhydrosis - inability to sweat

• sensation (touch)

urinary system

• removes waste from the blood

• expels wastes as urine

• regulates pH

respiratory system

• exchange oxygen and carbon dioxide

• external respiration: breathing

• internal respiration: oxygen used by cells

upper airway anatomy

• pharynx

• nasal cavity

• nostrils

• sinuses

• nasal septum

• larynx

• trachea

why can’t horses breathe through their mouths?

they have a long soft palette

roaring

• recurrent laryngeal neuropathy/hemiplasia

• caused by laryngeal hemiplegia

dorsal displacement of the soft palate

• soft palate displaces and sits on top of the epiglottis - obstructs airway

• usually intermittent

• treatment - nosebands, surgery

breathing

• controlled by the respiratory center (medulla oblongata)

• also - voluntary control

  • phonation, parturition, defecation

• locomotion - respiratory coupling during gallop

  • horse only inhales in suspension phase

EIPH

• exercise induced pulmonary hemorrhage

• seen in performance animals

  • intense exercise

  • increased pressure in pulmonary capillaries

  • capillary walls rupture

  • blood leaks into alveolar sac

  • exits via nostrils (epistaxis)

heaves (COPD)

• chronic obstructive pulmonary disorder

• caused by respiratory irritants

• treatment

  • remove irritant

  • increase turnout

  • bronchodilators

circulatory system

• supply body with nutrients and remove waste

  • heart

  • arteries

  • veins

  • capillaries

average thoroughbred heart weight

3.5 kg

how does blood get back to the heart?

blood percentages

• 9% of body weight (45L)

• 20% pulmonary (lung), 80% systemic

• 60% veins, 40% arteries

blood components

• RBCs

• WBCs

• platelets

• plasma

blood sampling

• jugular vein

• collected into tubes

• anticoagulant = plasma

• no anticoagulant = serum

hematocrit (PCV)

• percentage of RBCs in blood

• 30-45% is normal

• decrease if anemic, increase during stress and dehydration

spleen

stores and releases RBCs during exercise for increased oxygen delivery

control systems

• nervous system

• endocrine system

• maintain homeostasis - respond to external stimuli and change

equine sight

• wide range of vision

  • mostly monocular

  • some binocular

• blind spot immediately front and behind

equine eye

• eye is flattened

  • retina closer to lens at bottom

  • visual streak

• dichromatic vision

  • see blue and yellow-green, not red

tapetum lucidum (reflective)

night vision

hearing

• better than humans

• ears can rotate 180 degrees via 16 muscles

• deteriorates with age

• sound wave → eardrum vibrates → electrical impulses

taste

• highly linked to smell

• taste buds in papillae on tongue

• horses prefer sweet tastes

smell

• selection of food

• predator detection

• communication

  • social, reproduction

• smell droppings

  • what other horses have been here?

vomeronasal organ (organ of Jacobson)

• specialized olfactory (“scent”) cells

• can detect chemicals called pheromones

• enhanced with the flehmen response

axial skeleton

• bones that run along the central axis of the body

• skull

• vertebrae

• ribs (18 pairs)

• sternum

  • breastbone

touch

• nerve endings in the skin → transmit signals to the brain

• particularly sensitive over ribs

• communication

vertebrae

appendicular skeleton

• attached to axial skeleton at:

• pectoral girdle

  • no collarbone, muscular attachment only

  • pelvic girdle

forelimb

hindlimb

joints

• union of bones

• joint capsule

  • synovial fluid

  • articular cartilage

fibrous joints

or fixed, such as skull structures

cartilaginous joints

such as between the intervertebral discs

synovial joints

or free moving, the most common in horses

joint movements

• flexion

• extension

• lateral bending

• rotation

shoulder joint

ball and socket, flexion and extension only

stifle joint

a hinge joint similar to the human knee. femur and tibia, femur and patella

elbow

a hinge joint

knee

a gliding. joint similar to the human wrist, actually multiple joints

hock

a gliding joint similar to the human ankle, 4 joints. mostly absorb shock in lower 3

arthritis

inflammation of the joint

arthritis management

• oral joint supplements

• IM injections

• IA injections

• rest

• pain meds

types of muscle

cardiac, smooth, skeletal

muscles of the head

• splenius

• rhomboideus

• masseter

• brachiocephalicus

muscles of the forelimb

• no muscles below the carpus (knee), all tendons and ligaments

• deltoid

• triceps

• pectoral

muscles of the trunk

• trapezius

• latissimus dorsi

• intercostal

• abdominals

muscles of the hindlimb

• no muscles below the carpus (knee), all tendons and ligaments

• gluteals

• quadriceps

• gastrocnemius

exertion rhabdomyolysis

• muscle pain, tying up, azoturia, elevated CK

• recurrent - TBs, Standardbreds, arabians

• calcium issue inside muscle cell

polysaccharide storage myopathy

• muscle pain, stiffness, exercise intolerance

• quarter horse/related breeds

hyperkalemic periodic paralysis

• impressive bloodline (QH)

• weakness, muscle tremors, paralysis

hoof functions

• protection

• support weight, reduce concussion

• prevent slipping

• circulation

the lower limb

• support the weight of the horse

• 60% of the horse’s weight is in the front end

  • 1000 lb horse → 600 lb front end → 300 lb per foot

  • coffin bone supports almost all of this

• with help:

  • suspensory ligament

  • navicular bone

  • laminae/hoof capsule

tendons

• attach muscle to bone

• muscle contracts → pulls tendons → moves bone

flexor tendons

attach bone to muscles which contract to bend or flex a joint

extensor tendons

attach bone to muscles which contract to straighten or extend a joint

ligaments

• attach bone to bone

• hold tendons and joints in place

check ligaments

• help support flexor tendons

• superior and inferior

suspensory ligament

• between cannon bone and DDFT

• supports full weight of the horse

• stay apparatus

stay apparatus

• allow horse to rest while standing

• minimal muscle energy

stay apparatus - forelimb

opposing angle of joints and tendons/ligaments work together

stay apparatus - hindlimb

• opposing angle of joints and tendons/ligaments work together

• locking patella

• rotated over femur

• reciprocal mechanism - locks stifle and hock