Skeleton of the Equine The Fore and Hind Limbs Gerard Laverty A.W.C.F.

The Skeletal System The Bones: Cartilages: Form the major portion of the embryonic skeleton and part of the skeleton in the adult Ligaments: Connect the articular ends of the bones, binding them together and facilitating or limiting movement Connect cartilage and other structures Serve to support or attach fascia or muscles Gerard Laverty

The Function of Bones A framework to support the horses body Protection of internal organs Plays an important role in the formation of blood cells, in the Medullary Canal Provide elevation Part of the propulsion mechanism, articulation A reservoir of minerals, Calcium and Phosphorous For example the ribs, skull, spine. Elevation, long bones of the legs Combined with the muscles produce movement. The bones act as levers Gerard Laverty

Important Points Bone is not static – bone cells are being replaced and remodeled constantly Remodeling may be due to Conditioning Diet Conformation Disease Age Gerard Laverty

Positive Change Increase in thickness Increase in density Gerard Laverty

Negative changes Loss of bone quality or quantity, rarefaction or degeneration – for example Osteoporosis Extra bone deposits, exostosis – for example a “splint” May be caused by “Endogenous” or “exogenous” factors Gerard Laverty

The Composition of Bone The organic component, cells and matrix Organic – from living tissue The inorganic component, the minerals Inorganic – not derived from living tissue Gerard Laverty

Regions of the Part The Limb: All the bones of the structure The Leg: The bones from the knee or hock to the ground The Digit: The bones from the fetlock to the ground Gerard Laverty

The Parts of a Bone Epiphysis: The ends of the bone, may include articular surface The Physis: The area of growth The Diaphysis: The shaft of the bone Periosteum: Skin covering the bone except at the articular surface and P.3. Compact or cortical bone: The outer dense, hard, layer of bone tissue Medullary Canal: A narrow space or cavity throughout the length of the diaphysis Bone marrow: Soft material filling the canal Cancellous or spongy bone: The network of spongy bone tissue that makes up the majority of the bone Gerard Laverty

Gerard Laverty

Bones of the Fore Limb Scapula: The shoulder blade Humerus: Point of shoulder to elbow Ulna: Forms the point of the elbow Radius: The area from the elbow to the knee The Carpal bones: 7 bones in 2 rows, lowest joint does not open The Metacarpal bones The Sesamoids, proximal First Phalange Second Phalange Third Phalange Distal Sesamoid Gerard Laverty

Bones of the Fore Limb Scapula Humerus Ulna Radius Carpals Metacarpals What will happen to this. Carpals Metacarpals Sesamoids 1st 2nd 3rd.Phalanges Distal Sesamoid Gerard Laverty

Bones of the Hind Limb The Pelvis The Femur, hip to stifle Patella Fibula, Tibia Tarsal bones, 6, main movement between the Tibia and the Tibia - Tarsal Metatarsal bones, 3 Same as the fore leg and digit Gerard Laverty

Pelvis Pelvis Femur Patella Fibula, Tibia Tarsals Metatarsals, 2,3,4 Proximal Sessamoid Phalange 1,2,3. Distal Sessamoid Gerard Laverty

The Metacarpals Large Metacarpal: M. 3. Long bone, large head forms part of the knee joint. Tapered shaft, with large Foramina on the posterior face. Large distal end, articular surface divided by Median Ridge, articulates with P. 1. and Proximal Sessamoids Small Metacarpals: M. 2 and M. 4. Large head, fine tapering shaft, rounded distal end. Forms part of the knee joint. M. 2 has two articular faces and is slightly larger than M. 4. They form a groove on the posterior aspect of M. 3 for ligament and tendons. Gerard Laverty

Proximal Sesamoids Located on the posterior distal end of M. 3. Articulate with M. 3 Triangular in shape Increase the articular surface of the fetlock joint Act as fulcrum point for ligaments and tendons Gerard Laverty

First Phalange Located between distal end of M. 3 and proximal end of P. 2 Large articular head with Median Groove matching the Median Ridge of M. 3 Forms part of the fetlock joint Tapered shaft Large distal end forms part of Pastern Joint Gerard Laverty

Second Phalange Cube shaped Proximal articular face forms part of Pastern joint Distal end forms part of the Coffin joint Distal end of the bone is within the hoof Gerard Laverty

Distal Sesamoid Small boat shaped Located on distal posterior aspect of P. 2 Forms part of the Coffin joint Acts as a fulcrum for tendon to pass over Gerard Laverty

Distal Phalange, P.3. Modified bone Very porous No Periosteum Corium Fore digit, P. 3 is rounded on it’s lower perimeter Hind is more pointed, palmar surface more concave Gerard Laverty

Parts of P.3. Pyramidal or Extensor Process Distal perimeter rounded on fore, pointed on hind The Wings, divided by the Pre – Plantar Groove Semi – Lunar Crest Palmar/plantar Foramina Corium in place of Periosteum Very Porous, concave solar surface Articular surface divided by a median ridge Gerard Laverty

Self Test The skeletal system is made up of how many parts, what are they? A major portion of the embryonic skeleton is composed of …………… Ligaments connect bones together, T/F List four functions of bones Bone is constantly being replaced, T/F Three causes of bone change, A negative change of bone would be called……., for example ………… The term for an extra bone deposit is ……….. Bone change brought on by external factors is said to be “Exogenous”, T/F Bone has an organic and inorganic makeup, the organic part is the bone cell or matrix. What is the inorganic part? Using the forelimb as an example what part is the leg and what part the digit? Any bone can be separated into different areas, the ends are called ……. The area of growth in a young bone is called the ………. The shaft is called the ……….. All the bones of the limb except one are covered by a thin skin called the ………. If you cut through a bone the outer layer is very dense that is the “cortical bone” T/F The inner layer of bone is “Cancellous bone” T/F The cavity in the centre of long bones is called the ……………… The acronym SHUR stands for Scapula, ………., ……….., ……….. Below the knee of hock there are, 7, 8, 9, or 11 bones? The scapula is attached to the spine with a shoulder joint as in humans, T/F The small bones of the knee are called, ………………? The correct term for the cannon bone of the fore leg is …………? The correct term for the navicular bone is ………..? The hind leg differs from the fore because it has a boney joint to the spine T/F? Bones have holes for blood vessels to pass through, they are called ……….? Gerard Laverty