How many bones does a mouse have? - briefly
A typical mouse possesses roughly 230–250 skeletal elements, including the skull, vertebral column, ribs, and limb bones. Variation among species may shift the total by a few dozen.
How many bones does a mouse have? - in detail
A typical adult laboratory mouse possesses roughly 230 to 250 bones, a figure that includes the vertebral column, ribs, limbs, skull and tail. The exact count varies slightly among strains and between sexes, but the range remains consistent across the species.
The skeletal system can be broken down into major regions with approximate bone counts:
- Skull and associated facial bones – about 30 bones.
- Cervical, thoracic and lumbar vertebrae – roughly 70 vertebrae, including 13 cervical, 13 thoracic and 6 lumbar elements.
- Sacrum and coccygeal vertebrae – 4 to 6 bones forming the pelvic connection and tail base.
- Ribs – 24 individual ribs attached to the thoracic vertebrae.
- Pectoral girdle (scapulae and clavicles) – 2 bones.
- Forelimb – 30 bones per side, comprising humerus, radius, ulna, carpals, metacarpals and phalanges.
- Pelvic girdle (ilium, ischium, pubis) – 3 bones per side, fused into a single pelvic bone in the adult.
- Hindlimb – 30 bones per side, including femur, tibia, fibula, tarsals, metatarsals and phalanges.
- Tail – 30 to 40 vertebrae, each forming a separate bone segment.
Developmental stage influences the total number. Newborn mice have a higher count of separate ossification centers, many of which fuse during growth, resulting in the adult range cited above. Genetic mutations affecting skeletal development can increase or decrease the count, a factor frequently monitored in biomedical research.
Comparative anatomy places the mouse within the rodent order, where bone numbers are similar to other small mammals but lower than in larger species. The compact skeletal structure supports rapid locomotion, agility and the ability to navigate confined spaces, traits essential for survival in natural habitats and for experimental handling.
Understanding the precise bone composition of this model organism aids in interpreting musculoskeletal studies, evaluating disease models such as osteogenesis imperfecta and assessing the impact of pharmaceutical agents on bone health.