Dog Bones

• Anatomy is the study of the structure of living organisms, including the forms, disposition, and structure of tissues and organs
• Veterinary Anatomy specifically focuses on the anatomy of principal domesticated animals
• Different types of anatomy include:

  • Macroscopic or Gross Anatomy: study of structures that can be dissected and observed with an unaided eye or hand lens
  • Microscopic Anatomy or Histology: study of structures too small to be seen without a light microscope, including Ultrastructural Anatomy using electron microscopes (Scanning and Transmission)
  • Pathological Anatomy: study of deviations from the normal in cases where animals become diseased or organs function improperly
  • Embryology: study of an individual's development from fertilization to birth
  • Developmental Anatomy: study of development from zygote to adult
  • Teratology: study of abnormal development
• Chief methods of studying anatomy include:

  • Topographical Anatomy: study of structures in relation to other parts of the body
  • Systematic Anatomy: study of organ systems closely related or of similar origin, constituting body systems with a common function
  • Applied Anatomy: practical application of knowledge in diagnosis and treatment
• Divisions of Systematic Anatomy:

  • Osteology: study of bones and cartilages
  • Syndesmology: study of joints and ligaments
  • Myology: study of muscles and accessory structures
  • Splanchnology: study of viscera (digestive, respiratory, urogenital, peritoneum, and ductless glands)
  • Angiology: study of organs of circulation (heart, arteries, veins, lymphatics, and spleen)
  • Neurology: study of the nervous system
  • Sense Organ: study of organs relating the individual to the environment
  • Common Integument: study of the protective envelope of the body (skin) and related structures (mammary gland, hooves, claws, comb, and wattles)
• Directional terms in veterinary anatomy:

  • Dorsal: toward the back
  • Ventral: toward the belly
  • Cranial: toward the head
  • Caudal: toward the tail
  • Medial: toward the median plane
  • Lateral: toward the side
  • Rostral: toward the muzzle
  • Proximal: toward the junction with the body
  • Distal: at a greater distance
  • Abaxial: positions away from the reference axis
• Functions of the skeleton include:

  • Structural support
  • Protection of soft tissues
  • Muscle attachment for lever action
  • Storage of minerals (calcium and phosphorus)
  • Storage of fat
  • Hematopoietic organ for blood cell formation (RBC, Hb, WBC, Platelets)
• The skeleton is composed of changing, actively metabolizing tissue that may be altered in shape, size, and position by mechanical or biochemical demands
• Compact/Dense Bone:

  • Forms the outer shell of skeletal parts
  • Composed of largely calcified interstitial substance called bone matrix deposited in layers called lamellae
• Cancellous/Spongy Bone:

  • Elaborated in extremities of long bones
  • Consists of bony plates and spicules running in various directions
  • Forms the bulk of short bones and in variable distance along the shaft of long bones
• Periosteum:

  • Connective tissue covering the non-articular outer surface of the bone
• Endosteum:

  • Similar to periosteum but thinner
  • Lines the medullary cavity and nutrient canals of the bone
• Under emergency conditions like fractures, the periosteum and endosteum provide osteoblasts to aid in the repair of the injury
• In emergency conditions like fractures, the periosteum and endosteum provide osteoblasts to aid in the repair of the injury
• Mucoperiosteum:

  • Lining of paranasal sinuses containing mucous cells
  • Covers bones forming boundaries of the respiratory or digestive system
• Osteology:

  • Bone structures
  • Exostoses: osseous bulge in the site of injury
• Bone-forming cells (Osteoblasts):

  • Synthesize building blocks of bone matrix
  • Respond to circulating hormones
  • Produce growth factors that mobilize osteoclast precursor cells
• Blood vessels and nerves in bones:

  • Living tissues with arterial and nervous supplies
  • Nerves are mainly sensory and accompany blood vessels
• Nutrient artery:

  • Enters the nutrient foramen
• Medullary arteries and veins:

  • Pass through the compact substance supplying marrow and spongy bone
• Periosteal arteries and veins:

  • Supply periosteum and compact substance
  • Reach Haversian or nutrient canal of compact bones through Volkmann’s canal
• Long bones:

  • Found in limbs
  • Typically cylindrical with a hollow medullary cavity
  • Possess great tensile strength
  • Ends are freely movable joints
  • Consist of shaft (diaphysis) and epiphysis with growing cartilage (epiphyseal growth plate)
• Short bones:

  • Confined to carpal and tarsal bones
  • Typically cuboidal with at least one non-articular surface for tendon attachment or passage of blood vessels and nerves
• Classification of bones:

  • Sesamoid bones: near moving joints, formed in tendons, protect tendons from friction
  • Flat bones: limbs or girdles, serve as muscle attachments, some contain paranasal sinuses
  • Irregular bones: vertebral column, parts of the hip bone, protect spinal cord and provide rigidity to organs
• Parts or division of skeleton:

  • Axial: skull, spinal/vertebral column, ribs, sternum
  • Appendicular: limbs
  • Heterotopic/splanchnic: bones developed in soft tissues or visceral organs
• Bones of the hyoid apparatus:

  • Acts as a suspensory mechanism for the tongue and larynx
  • Components united by synchondroses (hyaline cartilage)
  • Consists of basihyoid, thyrohyoid, ceratohyoid, epihyoid, stylohyoid bones, and tympanohyoid cartilages
• Parts of a typical vertebra:

  • Body, arch, processes (spinous, transverse, mamillary, articular, accessory, hemal)
  • Vertebral foramen
  • Arch made up of pedicle and lamina
• Vertebral column:

  • Intervertebral foramina bounded by cranial and caudal vertebral notches
  • Transverse processes contain foveae for rib articulation
  • Mamillary processes start at second or third thoracic vertebra
  • Accessory processes appear first in midthoracic region
  • Articular processes located at junctions of pedicles and laminae
• Cervical vertebrae:

  • First two differ greatly from others
• Cervical Vertebrae:

  • The first two vertebrae differ greatly from each other and from all the other vertebrae
  • The third, fourth, and fifth cervical vertebrae differ only slightly and are difficult to differentiate
  • The sixth and seventh cervical vertebrae have distinct differences that make their identification possible
• Atlas - 1st cervical vertebra:

  • Articulates with the skull at the cranial end and with the axis at the caudal end
  • Chief peculiarities include a specially modified articular process, wing-like lateral expansion, and lacks a spinous process
  • The alar notch is located at the attachment of the wing of the atlas to the lateral mass and is occupied by the ventral branch of the first cervical nerve
• Axis - 2nd cervical vertebra:

  • The longest cervical vertebra
  • Has a blade-like spinous process that extends caudally
  • Features a dens or odontoid process, which is a cranioventral eminence
• Other Cervical Vertebrae:

  • The 3rd to 5th vertebrae differ slightly from each other
  • The 6th vertebra has expanded sagittal plate-like transverse processes
  • The 7th vertebra lacks a transverse foramen
• Thoracic Vertebrae:

  • There are 13 thoracic vertebrae
  • The first nine are similar, while the last four present minor differences
  • Each thoracic vertebra has cranial and caudal articular costal fovea for the articulation of the head of the ribs
• Lumbar Vertebrae:

  • There are 7 lumbar segments
  • Flattened dorsoventrally with longer bodies than thoracic vertebrae
  • The width increases from the first to the last lumbar vertebra
• Sacral Vertebrae:

  • Consist of 3 fused segments forming the sacrum
  • The median sacral crest is formed by the fused spinous process
  • The wing of the sacrum articulates with the ilium
• Caudal or Coccygeal Vertebrae:

  • Variable in number (20-23 segments)
  • Tapering in size, with the first cranial members having parts of a typical vertebra
  • Hemal arches (chevron bones) are located in the ventral surface of the 4th to 6th caudal vertebrae
• Ribs / Costa:

  • There are 13 pairs of ribs
  • Consist of dorsal bony parts that articulate with thoracic vertebrae and ventral cartilaginous parts that articulate with the sternum
  • The 9th rib is the longest, and the 13th rib is a free or floating rib
• Sternum:

  • Segmented and unpaired, with 8 segments joined by intersternebral cartilages
  • Consists of the manubrium as the 1st segment and the xiphoid process as the last segment
• Thoracic Limb:

  • Consists of 4 chief segments: pectoral girdle, arm (humerus), forearm (radius and ulna), and manus (carpus, metacarpus, digits, sesamoids)