Equine Skeletal system

Objectives List the components of the skeletal system Label the divisions of the vertebral column Label the bones of the skull Label the bones of the appendicular skeleton Foreleg and hind leg List and describe three types of joints Label the joints of the leg (fore and rear)

Surface Planes of the horse Caudal- The plane going towards the hindend. The rear portion. Cranial- The plane going towards the head end (front). The front portion Distal- Further away from the main part of the body, furthest. Example: The hoof is the most distal part of the leg. Dorsal- Back surface or topline Lateral- Away from the median (middle line) plane. It is also the outside or external surface. Medial- Towards the middle (median plane) of the body. The inner or more internal part. Palmer- The sole (bottom) of the front hoof continuing up to the back of the knee (carpus) Plantar- The sole of the hind hoof continuing up to the back of the hock (tarsus) Proximal- Closer to the body, or point of attachment. Example: The knee is proximal to the ankle Rostral- Towards the nose Ventral- Underneath or belly side

Axial Skeleton contains bones in the trunk area. Skull Spine (Vertebral column) Ribs Breastbone (Chest cavity) Pelvis Tail

Skull bones – flat, irregular in shape Forms framework for the brain, mouth, eyes & nasal cavity. Vertebral column – flexible column of small bones (vertebrae) Hip bones – two large flat bones attached to the spine and sacrum that forms the pelvis or pelvic girdle Ribs & Breastbone (Sternum) along with thoracic vertebrae form the chest cavity

Bones of the skull (fig. 5-4) Temporal Frontal Nasal Parietal Zygomatic arch Maxilla Mandible

Appendicular Skeleton – forelegs and hindlegs used for locomotion, defense and feeding Forelegs – connected to axial skeleton by muscles, not skeletal attachments Hindlegs – attached to pelvis at the hip joint

Foreleg

Rear leg

Vertebral Bones (fig. 5-5) 7 Cervical vertebrae 18 thoracic 6 lumbar 5 sacral 15 – 21 coccygeal (tail)

Ribs and sternum 18 pairs of ribs 7 – 8 bony segments connected by cartilage make up the sternum

Types of joints A joint is the union of two or more bones: 1. Immovable joint: bones are directly connected by cartilage or fused and permit no movement Example: bones of the cranium 2. Slightly moveable joint: joined by a pad of cartilage that adheres to both bones. Vertebrae Ribs to vertebrae

Types of Joints 3. Freely moveable joints: “True joints” allow range of movement. Bones are held together by ligaments that pass from one bone to another Ends of bones are covered in smooth cartilage: articular cartilage Absorbs shock and provides cushion, provides for smooth bearing Entire joint is enclosed in fibrous sac: joint capsule Inner surface of capsule – synovial membrane Contains synovial fluid, lubricant

Joints of the foreleg (from top downward: Shoulder: formed by scapula and humerus Elbow: formed by humerus Knee: formed by radius. carpal bones, and three metacarpal bones, splints and cannon bones Fetlock: formed by cannon, two seismoid bones and the first phalanx (long pastern) Pastern: formed by first and second phalanges (long and short Pastern) Coffin: formed by second phalange (coffin bone)and navicular bone.

Joints of the rear leg (from top downward Hip: formed from the pelvis and femur Stifle: formed from the femur, tibia and fibula Hock: formed by the tibia, tarsals (hock bone) and the metatarsals (splint and cannon bone). Fetlock: formed by cannon, two seismoid bones and the first phalanx (long pastern) Pastern: formed by first and second phalanges (long and short Pastern) Coffin: formed by second phalange (coffin bone) and navicular bone.