The Skeletal System
Skeletal System
• Bony tissues that form the body’s
framework comprise the Skeletal System.
• In domesticated animals, the skeletal system
is internal, called an endoskeleton, and are
basically alike in most species.
Skeletal System
• The number of bones in a horse’s neck are
the same as those in a rabbit’s, but the size
and length vary.
Skeletal System
• The outer layers of bones are composed of
hard mineral deposits. About 26% of total
bone mass is composed of mineral matter.
• The remainder of the composition of bones
includes 20% protein, 4% fat, and 50%
water.
Skeletal System
• About 85% of the mineral matter is calcium
phosphate.
• The remaining 15% is calcium carbonate.
Skeletal System
• The inner core of bones is soft tissue called
bone marrow.
• Some of the bone marrow consists of
yellow fat, called yellow marrow.
• The other portion is made of red tissue
called red marrow, that is responsible for
red blood cell formation.
Skeletal System
• As an animal grows, bones increase in size
and length in the region of cartilage
between the end and shaft of bones.
• As the animal matures, this cartilage
ossifies (becomes bony material).
Skeletal System
• In mature animals, bone is continually being
reabsorbed and replaced, but no new bone
growth occurs.
• Osteoporosis occurs when the bone that is
reabsorbed is not replaced.
Skeletal System
• As long bones grow in length, they also
increase in diameter.
• This is caused by the production of new
bony tissue in the periosteum that surrounds
the outside of the bone.
Skeletal System
• Bone growth is affected by hormones,
vitamins, and other nutrients.
• Therefore, bones can become fragile or
distorted due to nutritional deficiencies.
• Breaks in bones repair when the ends fill with
a fibrin clot, that becomes bony tissue.
Skeletal System
• The skeletal system provides body support
and leverage for muscle movement, which
is made possible by several types of joints.
Skeletal System
• Ball-and-socket joints can move in all
directions (shoulder).
• Hinge joints move in only two directions
(knee).
• Pivot joints allow for movement in several
directions (neck)
Skeletal System
• Gliding joints allow for flexibility to move
forward, backward, or sideways (vertebrae)
Skeletal System
• Joints are held together by ligaments and
are enclosed by a capsule which contains
synovial fluid to lubricate the joint and
allow friction-free movement.
Skeletal System
• The skeletal system of animals of the
phylum Chordata can be divided into three
parts:
– the axial (spine, ribs, sternum, skull)
– the pectoral limb (foreleg)
– the pelvic limb (pelvic girdle and hindlegs)
Skeletal System
Axial -
Pectoral -
Pelvic -
Skeletal System
• The vertebral column (spine) is divided into
five regions:
–
–
–
–
–
Cervical (7 vertebrae)
Thoracic (13 vertebrae)
Lumbar (6 vertebrae)
Sacral (5 vertebrae)
Coccygeal (18-20 vertebrae)
Skull
Cervical
Vertebrae
Skeletal System - Axial
Thoracic
Vertebrae
Lumbar
Vertebrae
Ribs
Sternum
Xyphoid
Sacral
Vertebrae
Coccygeal
Vertebrae
Skeletal System - Pectoral
Scapula
Humerus
Ulna
Radius
Metacarpal
Carpus
Bones
Phalanges
Skeletal System - Pelvic
Ilium
Pelvis
Ischium
Femur
Patella
Tibia and Fibula
Tarsus
Metatarus
Phalanges
Skeletal System
Clavicle
Scapula
Humerus
Lumbar Vertebrae
Pelvis
Maxillar
Mandible
Sternum
Ribs
Radius
Coccyx
Ulna
Carpus
Femur
Patella
Metacarpus
Phalanges
Tibia
Fibula
Tarsus
Metatarsals
Phalanges
Skeletal System
• Bones are divided into four classes based on
their shape and function:
– Long bones (support)
– Flat bones (muscle attachment and organ protection)
– Short bones (help in movement and change the
direction of tendons)
– Irregular bones (vertebrae)
Skeletal System
• Parts of the skeletal system protect vital
organs.
– Skull (protects the brain)
– Rib cage (protects the heart, lungs, and certain
abdominal organs)
– Vertebrae (protect the spinal column)