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THE SKELETAL SYSTEM

THE SKELETAL SYSTEM. CH 6 – THE APPENDICULAR SKELETON. FORELIMBS. The number of bones and their development differs among species EXAMPLE: Many species have DIGITS that are similar to our fingers Some species have HOOVES that encase their digit or digits

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THE SKELETAL SYSTEM

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  1. THE SKELETAL SYSTEM CH 6 – THE APPENDICULAR SKELETON

  2. FORELIMBS • The number of bones and their development differs among species • EXAMPLE: • Many species have DIGITS that are similar to our fingers • Some species have HOOVES that encase their digit or digits • These animals are called UNGULATES

  3. CLAVICLE • COLLARBONE • Articulates medially with the sternum and laterally with the scapula • Only well developed in animals that can grasp (cats and primates) • Usually a vestigial remnant (relating to a body part that has become small and lost its use because of evolutionary change) • Both are fused in birds to form wishbone

  4. SCAPULA (shoulder blade) • Large triangular bone on the side of the thorax • HUMERUS • Long bone that extends from theshoulder (articulates with scapula) to the elbow (articulates with ulna and radius) • ULNA • Located caudal to radius • Forms the elbow • Articulates with the humerus at the OLECRANON (point of the elbow) • Fused to the radius in the HORSE

  5. RADIUS • Cranial to ulna • Articulates with the humerus, ulna, and carpal bones • main load-bearing bone of the lower forelimb • CARPUS • Numerous short/irregular bones arranged in 2 rows • Refers to the entire wrist including the joint • Also called the KNEE in large animals

  6. METACARPALS • Vary in number between species (Ex: dog – 5, horse – 3) • Numbered from medial to lateral • Horse has a CANNON BONE (3rd metacarpal) that articulates with the digit • Small metacarpals are calledSPLINT BONES in the horse (smaller than the cannon and do not articulate with the digit)- metacarpals 2 and 4

  7. DIGITS • Numbered from medial to lateral • PHALANGES are located within the digits • Usually 3 phalanges in one digit (P1, P2, P3) • Digit 1 (dewclaw) is often removed in dogs • Horses have only one digit (III) with 3 phalanx bones. • P1 and P2 are PASTERNS • P3 is the COFFIN BONE

  8. CLOVEN hoofed animals have a split hoof • Cow, pig, goats • 2 metacarpals ( III and IV) which are fused in the cow, and 2 complete digits (III and IV) with 3 phalanx bones in each • The other digits are vestigial

  9. SESAMOIDS • Small bones found with a joint capsule or tendon • HORSE: Caudal aspect of fetlock (called proximal sesamoids) and caudal to P3 (navicular bone) • Patella is the largest sesamoid

  10. HINDLIMB • Variations exist between species in the number and development of the bone

  11. PELVIS • 3 pairs of bones that fuse to become one • IIium – the largest bone • Flares out to the side • Ischium – strongest, most caudal • Pubis – Most ventral • Connects to the sacrum at the sacroiliac joint • Pubic Symphysis is where the paired pubic bones meet • Acetabulum of the pelvis forms the ball and socket joint

  12. PELVIS

  13. FEMUR • Longest bone in the body • Thigh • Articulates with the acetabulum proximally to form the hip joint • Articulates with the tibia and patella at the distal end of to form the STIFLE JOINT (knee in humans)

  14. PATELLA • Kneecap • Flat sesamoid bone that glides over the stifle joint in the patellar ligament at the trochlea of the femur

  15. TIBIA • Part of the shin • Located on medial aspect of the leg • Articulates with the femur proximally and the tarsus and/or the fibula distally, depending on the species • Larger than fibula, more weight bearing

  16. FIBULA • Also part of the shin • Smaller than tibia • Small in size in the horse and cow (doesn’t articulate with tarsus in these species) • Long and slender in shape • Articulates with the femur proximally and the tibia and/or tarsus distally

  17. TARSUS • Ankle • Called HOCK in animals • Composed of numerous irregularly shaped bones arranged in rows

  18. METATARSALS • Very similar to forelimb • Vary in number between species • Numbered medial to lateral • Digits are also very similar to forelimb

  19. JOINTS • JOINT – an articulation between bones and cartilage that is held in place by ligaments • A joint may or may not have movement • Classified according to the degree of movement that they allow and their tissue structure

  20. JOINTS • SYNARTHROSES (Fibrous joints) • no movement • Ex: Skull • AMPHIARTHROSES (Cartilaginous joints) • slight movement • Ex: Pelvis at pubic symphysis, vertebral column • DIARTHROSES (Synovial joints) • freely movable, but not all in the same manner • Most numerous in the body • Ex: Hip joint, shoulder joint

  21. JOINTS – terms on page 92

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