Bone Structure and Tissues

Periosteum

• Tough connective tissue sheath covering bone
• Contains blood vessels essential for bone nourishment and repair.
• Facilitates fracture healing.
• Serves as an attachment point for ligaments and tendons.

Medullary Cavity

• Hollow, cylindrical space within the diaphysis (shaft) of long bones.
• Filled with yellow bone marrow, primarily composed of fat, and blood vessels.

Endosteum

• Thin membrane lining the medullary cavity.
• Contains a single layer of bone-forming cells (osteoblasts) and a small amount of connective tissue.

Bone Structure

• The diaphysis is the long, cylindrical, main portion of the bone.
• The epiphyses are the proximal and distal ends of the bone.
• The metaphysis is the region between the diaphysis and the epiphyses.
• Articular cartilage is a thin layer of hyaline cartilage that covers the part of the epiphysis.
• Articular cartilage reduces friction in movable joints.

Short, Irregular, and Flat Bones

• Short, irregular, and flat bones share a simple design with a thin outer layer of compact bone covered by the periosteum.
• The interior of these bones is made of spongy bone covered by the endosteum.
• These bones lack a diaphysis and epiphyses.
• Flat bones have no medullary cavity.
• The spongy bone in flat bones is called the diploë.

Skull Structure

• The skull is the bony framework of the head.
• It rests on the top of the vertebral column (spine).
• The skull houses the brain in the cranial cavity.
• The skull provides attachment points for the muscles of the head and neck.

Cranial Bones

• The cranial bones form the cranial cavity.
• They shield and protect the brain.

Facial Bones

• Facial bones form the framework of the face.
• They hold cavities for the eyes, nose, and mouth.
• They create openings for the passage of air and food.
• Facial bones anchor the teeth and facial muscles.

Paired Cranial Bones

• Parietal bones: Form the superior and lateral aspects of the skull.
• Temporal bones: Form the inferolateral aspects of the skull and part of the cranial floor. The zygomatic process forms the prominence of the cheek.

Unpaired Cranial Bones

• Frontal bone: Forms the forehead, roofs of the orbits and part of the cranial floor.
• Supraorbital foramina: Allow the passage of arteries and nerves.

Paired Cranial Bones

• Parietal Bones: Form the superior and lateral aspects of the skull.
• Temporal Bones: Form the inferolateral aspects of the skull and part of the cranial floor.
  • Zygomatic Process: Forms the prominence of the cheek.

Unpaired Cranial Bones

• Frontal Bone: Forms the forehead, roofs of the orbits (eye sockets), and part of the cranial floor.
  • Supraorbital Foramina: Permit the passage of arteries and nerves.

Periosteum Function

• The periosteum's primary function is to provide nourishment and facilitate bone growth and repair.

Medullary Cavity Contents

• The medullary cavity houses bone marrow, responsible for red blood cell production and fat storage.

Endosteum Cell Type

• The endosteum primarily comprises osteoblasts and osteoclasts, cells crucial for bone formation and resorption.

Endosteum Description

• The endosteum is a thin membrane lining the inner surface of the bone, including the medullary cavity and the Haversian canals.

Periosteum Attachment

• The fibrous layer of the periosteum is essential for attaching muscles and ligaments to the bone.

Bone's Main Portion

• The diaphysis is the main shaft of a long bone, providing structural support and strength.

Proximal and Distal Ends

• The epiphyses are located at the proximal and distal ends of a long bone, facilitating articulation with other bones.

Articular Cartilage Function

• Articular cartilage, covering the ends of bones within joints, provides a smooth, low-friction surface for articulation, reducing wear and tear.

Metaphysis Location

• The metaphysis is the region located between the diaphysis and epiphysis, responsible for longitudinal bone growth.

Diaphysis Definition

• The diaphysis is the main shaft of a long bone, characterized by its compact bone structure.

Flat Bone Spongy Bone

• The spongy, porous bone found within a typical flat bone is called diploë.

Short and Flat Bone Structure

• Short and flat bones lack a clear diaphysis and epiphysis, instead, their structure is dominated by spongy bone with a thin layer of compact bone.

Short and Flat Bone Distinguishing Feature

• Short and flat bones lack a diaphysis and epiphysis, which are present in long bones.

Inner Spongy Bone Layer

• The endosteum covers the inner spongy bone of short and flat bones, similar to its role in long bones.

Short and Irregular Bone Components

• Short and irregular bones consist of cancellous (spongy) bone enveloped by a thin layer of compact bone, followed by periosteum.

Cranial Bone Role

• Cranial bones primarily serve to protect the brain and its delicate structures from injury.

Facial Bone Function

• The primary function of facial bones is to provide support for the face, shaping facial features and facilitating various muscle attachments.

Skull Function in Respiration and Digestion

• Contributing to the formation of the nasal cavity, the skull plays a role in respiration by aiding air passage and in digestion through supporting the tongue and upper pharynx.

Cranial and Facial Bone Function Difference

• Cranial bones primarily focus on protecting the brain, while facial bones contribute to facial structure, support, and muscle attachment points.

Cranial Bone Roles Beyond Protection

• Besides protection, cranial bones also serve as attachment points for facial muscles and contribute to the formation of cavities for sensory organs.

Temporal Bone Formation

• The temporal bones contribute to the formation of sides and base of the skull, including the temporal fossa, external acoustic meatus, and mastoid process.

Unpaired Cranial Bone

• The sphenoid bone is an unpaired cranial bone, located at the base of the skull, contributing to the formation of the floor of the cranial cavity, orbits, and nasal cavity.

Supraorbital Foramina Function

• The supraorbital foramina present in the frontal bone allow passage for blood vessels and nerves, serving a vital role in facial sensory and motor functions.

Parietal Bone Truths

• Each parietal bone forms the upper lateral sides of the skull, contributing to the roof and sides of the cranial cavity.

Zygomatic Process Association

• The zygomatic process, part of the temporal bone, forms the anterior portion of the zygomatic arch, contributing to the cheek prominence.

Parietal Bone Formation

• The parietal bones primarily form the roof and sides of the cranial cavity, providing significant protection for the brain.

Cheek Prominence Bone

• The zygomatic bone contributes significantly to the formation of the cheek prominence and articulates with the frontal, temporal, and sphenoid bones.

Supraorbital Foramina Usage

• The supraorbital foramina present in the frontal bone allow passage for the supraorbital artery, vein, and nerve, facilitating sensory functions and blood supply to the forehead and upper eyelid.

Temporal Bone Location

• The temporal bones are located on the sides and base of the skull, forming part of the cranial cavity and contributing to the creation of the temporal fossa and external acoustic meatus.

Frontal Bone Truth

• The frontal bone forms the forehead, contributes to the roof of the cranial cavity, and forms the anterior portion of the nasal cavity and roof of the orbits.

Occipital Bone Location

• The occipital bone is located at the posterior base of the skull, forming part of the cranial cavity and contributes to the formation of the foramen magnum.

Foramen Magnum Function

• The foramen magnum, situated in the occipital bone, allows passage for the spinal cord, as well as blood vessels and nerves, connecting the brain to the rest of the body.

Occipital Bone Truth

• The occipital bone forms the posterior portion of the skull, including the back and base, and contributes to the formation of the foramen magnum.

Occipital Bone Feature

• The occipital condyles, located on the occipital bone, articulate with the first vertebra (atlas), facilitating head movement.

Occipital Bone Location Relative to Other Bones

• The occipital bone is located at the posterior base of the skull, articulating with the parietal, temporal, and sphenoid bones.

Sphenoid Bone

• Forms the posterior aspect and base of the skull.
• Known as the keystone of the cranial floor due to its articulation with all other cranial bones, providing structural support.
• Contributes to the middle cranial fossa and orbits.

Ethmoid Bone

• A delicate bone, forms the anterior aspect and base of the skull.
• Serves as the major superior supporting structure of the nasal cavity.
• Contributes significantly to the nasal cavity's surface area.
• Helps to form the anterior cranial fossa.