flat bones

Examples of flat bones in the following topics:

• Gross Anatomy

  • All the bones in the body can be described as long bones or flat bones.
  • Flat bones are broad bones that provide protection or muscle attachment.
  • These bones are expanded into broad, flat plates, as in the cranium (skull), ilium (pelvis), sternum, rib cage, sacrum, and scapula.
  • The flat bones are named:
  • These are flat bone, sutural bone, short bone, irregular, sesamoid bone, and long bone.

• Bone Development

  • Intramembranous ossification stems from fibrous membranes in flat bones, while endochondral ossification stems from long bone cartilage.
  • It is involved in the formation of the flat bones of the skull, the mandible, and the clavicles.
  • The non-mineralized portion of the bone or osteoid continues to form around blood vessels, forming spongy bone.
  • The spongy bone is remodeled into a thin layer of compact bone on the surface of the spongy bone.
  • All of the bones of the body, except for the flat bones of the skull, mandible, and clavicles, are formed through endochondral ossification .

• Stages of Bone Development

  • Intramembranous ossification mainly occurs during the formation of the flat bones of the skull, as well as the mandible, maxilla, and clavicles.
  • These cartilage poitns are responsible for the formation of the diaphyses of long bones, short bones, and certain parts of irregular bones.
  • Secondary ossification occurs after birth and forms the epiphyses of long bones and the extremities of irregular and flat bones.
  • The bone remodeling period refers to the average total duration of a single cycle of bone remodeling at any point on a bone surface.
  • Bone tissue is removed by osteoclasts, and then new bone tissue is formed by osteoblasts.

• Divisions of the Skeletal System: Axial and Appendicular

  • Humans are born with between 300 and 350 bones.
  • However, many bones fuse together between birth and maturity.
  • While some consider certain structures to be a single bone with multiple parts, others may see it as a single part with multiple bones.
  • There are five general classifications of bones.
  • These are long bones, short bones, flat bones, irregular bones, and sesamoid bones.

• Pubis

  • The pubis is the lowest and most anterior portion of the hip bones of the pelvis.
  • The pubic bone articulates with the ilium and the ischium on each hip.
  • The body of the pubis is a wide, strong, medial, and flat portion of the pubic bone that unites with the pubic symphisis.
  • The superior pubic ramus is one third of the pubic bone.
  • The inferior pubic ramus is a thin and flat bone that makes up one third of the pubis.

• Postnatal Bone Growth

  • It forms the epiphyses of long bones and the extremities of irregular and flat bones.
  • Osteoblasts are mononucleate cells that are responsible for bone formation.
  • During postnatal bone formation, endochondral ossification initiates bone deposition by first generating a structural framework at the ends of long bones, within which the osteoblasts can synthesize a new bone matrix.
  • The growth in the diameter of bones around the diaphysis occurs through the deposition of bone beneath the periosteum.
  • The epiphysis is the rounded end of a long bone located at its joint with adjacent bone(s).

• Human Axial Skeleton

  • The skull consists of 22 bones, which are divided into two categories: cranial bones and facial bones.
  • The eight cranial bones include the frontal bone, two parietal bones, two temporal bones, the occipital bone, the sphenoid bone, and the ethmoid bone.
  • The 14 facial bones are the nasal bones, maxillary bones, zygomatic bones, palatine, vomer, lacrimal bones, inferior nasal conchae, and mandible.
  • The auditory ossicles consist of six bones: two malleus bones, two incus bones, and two stapes, one of each on each side.
  • The sternum, or breastbone, is a long, flat bone located at the anterior of the chest.

• Human Appendicular Skeleton

  • The scapulae are flat, triangular bones that are located at the back of the pectoral girdle.
  • The humerus is the largest and longest bone of the upper limb and the only bone of the arm.
  • The hand includes the eight bones of the carpus (wrist), the five bones of the metacarpus (palm), and the 14 bones of the phalanges (digits).
  • The bones of the lower limb are the femur (thigh bone), patella (kneecap), tibia and fibula (bones of the leg), tarsals (bones of the ankle), and metatarsals and phalanges (bones of the foot) .
  • The metatarsals are the five bones of the foot, while the phalanges are the 14 bones of the toes .

• Cranial Bones

  • The neurocranium is comprised of eight bones: occipital, two temporal bones, two parietal bones, sphenoid, ethmoid, and the frontal bone.
  • The neurocranium consists of the occipital bone, two temporal bones, two parietal bones, the sphenoid, ethmoid, and frontal bones—all are joined together with sutures.
  • The squamosal suture separates the parietal bone and squama portion of temporal bone.
  • Squamous: This part is large and flat and forms the main region of the forehead.
  • The frontal bone borders two other neurocranial bones—the parietal bones through the coronal sutures and the sphenoid bone through the sphenofrontal suture.

• Bone

  • Bones are made of a combination of compact bone tissue for strength and spongy bone tissue for compression in response to stresses.
  • Compact bone (or cortical bone), forming the hard external layer of all bones, surrounds the medullary cavity (innermost part or bone marrow).
  • Compact bone tissue forms the outer layer of all bones while spongy or cancellous bone forms the inner layer of all bones.
  • Spongy bone reduces the density of bone, allowing the ends of long bones to compress as the result of stresses applied to the bone.
  • Imagine laying a heavy-framed picture flat on the floor.