Bone Physiology Flashcards
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What is bone?
Second hardest substance within an animals body (1st being the enamel layer of teeth) It is composed of cells embedded in a matrix (background)
whats Matrix?
Is made up of collagen fibers embedded in a protein and polysacharides
-Hardens when deposits of calcium and phosphates are laid down.
ossification
refers to the process by which new bone tissue is formed during skeletal development or bone healing. This process involves the deposition of minerals, primarily calcium and phosphate, into a matrix of collagen fibers, resulting in the hardening and strengthening of bone.
Intramembranous bone formation
This type of ossification occurs within a connective tissue membrane. It is responsible for the formation of flat bones, such as those in the skull and certain parts of the face. During intramembranous ossification, mesenchymal cells differentiate into osteoblasts, which then secrete osteoid tissue that mineralizes to form bone.
occurs in certain skull bones, bone forms in the fibrous tissue membranes that cover the brain in the developing fetus.
⦿ Intramembranous ossification: The flat bones of the skull are formed. the osteoblasts lay down bone between two layers of fibrous connective tissue. there is no cartilage template.
Osteoblasts: Osteoblasts are the cells that form new bones and grow and heal existing bones.
Endochondral Bone Formation
Endochondral ossification involves the replacement of cartilage with bone tissue. This process is responsible for the formation of most long bones in the body, as well as some irregular bones. During endochondral ossification, a cartilage model of the bone is first formed, which is gradually replaced by bone tissue as osteoblasts deposit minerals into the cartilage matrix.⦿ Primary growth center: bones develop in the diaphyses - cartilage rod -
⦿ Cartilage is removed as bone is created. Secondary growth centers: develop in the epithyses of bones.
⦿ Epiphyseal plates: cartilage is located between the diaphysis and the epiphysis of long bones, sites where new bone develops to allow long bones to lengthen.
⦿ Osteoblasts replace cartilage with bone on the diaphyseal surface of the plate, when the bone has reached its full size, the epiphyseal plates completely ossify.
Osteoblasts
Osteoblasts are essential cells involved in bone formation and remodeling processes in the body. They originate from mesenchymal stem cells and are primarily found in the outer layer of bone tissue, known as the periosteum, as well as in the endosteum, which lines the inner surfaces of bones.
When bone formation is required, osteoblasts become activated and begin synthesizing and secreting osteoid, which is a matrix rich in collagen fibers. This osteoid serves as the framework or scaffold for new bone tissue formation. Over time, minerals such as calcium and phosphate are deposited onto the collagen fibers within the osteoid matrix, a process known as mineralization or calcification. This results in the hardening of the osteoid into mature bone tissue.
In addition to producing osteoid, osteoblasts also play a role in regulating the mineralization process by secreting proteins and enzymes that control the deposition of minerals. These cells are also involved in the synthesis and release of various growth factors and signaling molecules that influence the activity of other bone cells, such as osteoclasts (cells responsible for bone resorption) and osteocytes (mature bone cells embedded within the bone matrix).
As bone formation progresses, some osteoblasts become entrapped within the mineralized bone matrix and differentiate into osteocytes. These osteocytes maintain communication with neighboring cells and play a role in regulating bone metabolism and responding to mechanical stress.
Fracture Types
Complete Fracture, Incomplete Fracture, Open Fracture (Compound Fracture), Closed Fracture, Transverse Fracture, Oblique Fracture, Spiral Fracture, Greenstick Fracture, Comminuted Fracture, Avulsion Fracture, Pathological Fracture, Impacted Fracture, Linear Fracture, Compression Fracture, Segmental Fracture, Hairline Fracture, Stress Fracture, Depressed Fracture, Displaced Fracture, Non-displaced Fracture, Fatigue Fracture, Tension Fracture, Shear Fracture, Torus Fracture (Buckle Fracture).
Complete Fracture
- Cause: Typically caused by direct trauma, excessive force, or stress applied to the bone.
- Occurrence: Can happen in any bone of the body.
- Appearance: The bone is completely broken into two or more separate pieces.
- Healing Approach: Generally treated with immobilization, alignment, and stabilization through methods such as casting, splinting, or surgical fixation.
Incomplete Fracture
- Cause: Similar to complete fractures, but the bone is partially broken.
- Occurrence: Any bone can experience an incomplete fracture.
- Appearance: The bone is partially broken, with some degree of continuity remaining.
- Healing Approach: Treatment involves immobilization and protection of the affected area to allow for bone remodeling and healing.
Open Fracture (Compound Fracture)
- Cause: Trauma that causes the bone to penetrate through the skin, exposing it to the external environment.
- Occurrence: Can occur in any bone but is more common in long bones like the femur or humerus.
- Appearance: The broken bone protrudes through the skin, often accompanied by bleeding and potential contamination.
- Healing Approach: Immediate medical attention is required to clean and stabilize the wound, followed by fracture management and wound care to prevent infection.
Closed Fracture
- Cause: Trauma without an open wound, where the bone breaks but does not penetrate the skin.
- Occurrence: Can happen in any bone.
- Appearance: The broken bone does not pierce through the skin.
- Healing Approach: Treatment involves immobilization and alignment of the bone to promote healing without the risk of infection.
Transverse Fracture
- Cause: Direct force applied perpendicular to the long axis of the bone.
- Occurrence: Commonly seen in long bones like the femur, tibia, and humerus.
- Appearance: The fracture line runs straight across the bone.
- Healing Approach: Treatment typically involves realignment and stabilization with casts, splints, or surgical fixation if necessary.
Oblique Fracture
- Cause: Force applied at an angle to the long axis of the bone.
- Occurrence: Can occur in any bone.
- Appearance: The fracture line runs diagonally across the bone.
- Healing Approach: Similar to transverse fractures, treatment involves realignment and stabilization.
Spiral Fracture
- Cause: Twisting force applied to the bone.
- Occurrence: Often seen in long bones like the femur and tibia.
- Appearance: The fracture line spirals around the bone.
- Healing Approach: Requires careful realignment and stabilization to ensure proper healing and alignment.
Greenstick Fracture
- Cause: Typically occurs in young animals with more flexible bones, resulting from bending rather than breaking.
- Occurrence: Common in long bones of young animals.
- Appearance: The bone is bent and partially broken, with one side intact and the other side fractured.
- Healing Approach: Often managed with immobilization and protection, allowing the bone to remodel and heal.
Comminuted Fracture
- Cause: Severe force leading to the bone breaking into multiple fragments.
- Occurrence: Can occur in any bone.
- Appearance: Multiple bone fragments at the fracture site.
- Healing Approach: Surgical intervention may be necessary to align and stabilize the fragments, promoting proper healing.
Avulsion Fracture
- Cause: Tendon or ligament pulls a small piece of bone away.
- Occurrence: Common in areas where tendons or ligaments attach to bones.
- Appearance: A small fragment of bone is separated at the attachment site.
- Healing Approach: Treatment involves immobilization and may require surgical intervention for reattachment.
Pathological Fracture
- Cause: Fracture occurs in a bone weakened by an underlying disease or condition, such as bone cancer or osteoporosis.
- Occurrence: Can occur in any bone affected by the underlying pathology.
- Appearance: Fracture in a bone with pre-existing damage or weakness.
- Healing Approach: Management involves addressing the underlying condition and stabilizing the fracture.
Impacted Fracture
- Cause: One fragment of bone is driven into another due to compression forces.
- Occurrence: Common in long bones.
- Appearance: The fractured ends are impacted into each other.
- Healing Approach: Stabilization and immobilization to allow the impacted fragments to unite.
Linear Fracture
- Cause: Force applied parallel to the long axis of the bone.
- Occurrence: Can occur in any bone.
- Appearance: The fracture line runs parallel to the long axis of the bone.
- Healing Approach: Treatment involves realignment and stabilization.
Compression Fracture
- Cause: Bone is crushed or compressed.
- Occurrence: Common in vertebrae.
- Appearance: The bone is compressed, often resulting in a wedge shape.
- Healing Approach: Immobilization and support to allow for vertebral healing and stabilization.
- Torus Fracture (Buckle Fracture):
- Cause: Compression force applied to the bone, causing it to buckle but not break completely.
- Occurrence: Commonly seen in the metaphyseal region of long bones, especially in children and young animals.
- Appearance: The bone buckles but remains intact.
- Healing Approach: Often heals spontaneously with immobilization and protection of the affected limb.
Segmental Fracture
- Cause: High-energy trauma or direct force causing a bone to break into two distinct segments with an intermediate fragment.
- Occurrence: Can occur in any bone but often seen in long bones.
- Appearance: The bone breaks into two separate segments with an intermediate fragment.
- Healing Approach: Requires careful realignment and stabilization to ensure proper healing and alignment of all segments.
Hairline Fracture
- Cause: Minor trauma or repetitive stress causing a small crack in the bone.
- Occurrence: Can occur in any bone.
- Appearance: A small, fine crack in the bone without significant displacement.
- Healing Approach: Often heals with rest and reduced activity, although sometimes requires immobilization or protection to prevent further damage.
Stress Fracture
- Cause: Overuse or repetitive stress on the bone, leading to microscopic cracks.
- Occurrence: Commonly seen in athletes and working animals.
- Appearance: Small, hairline cracks in the bone due to repetitive stress.
- Healing Approach: Requires rest and modification of activities to allow for bone remodeling and healing.
Depressed Fracture
- Cause: Direct trauma causing the bone to be pushed inward, creating a depression.
- Occurrence: Often seen in flat bones like the skull.
- Appearance: The bone is depressed or indented.
- Healing Approach: Treatment involves careful evaluation for associated injuries and may require surgical intervention to elevate the depressed bone fragment.
Displaced Fracture
- Cause: Trauma causing the bone fragments to move out of alignment.
- Occurrence: Can occur in any bone.
- Appearance: Bone fragments are not in their normal alignment.
- Healing Approach: Requires reduction (realignment) of the fractured bone followed by stabilization to promote proper healing.
Non-displaced Fracture
- Cause: Trauma causing a fracture without significant displacement of bone fragments.
- Occurrence: Can occur in any bone.
- Appearance: Bone fragments remain in their normal alignment.
- Healing Approach: Treatment usually involves immobilization and protection to allow for bone healing without the need for reduction.
Fatigue Fracture
- Cause: Result of repetitive stress or loading on a bone over time, often seen in athletes or animals subjected to intense physical activity.
- Occurrence: Can occur in any bone.
- Appearance: Fracture caused by fatigue or weakening of bone due to repetitive stress.
- Healing Approach: Requires rest and modification of activities to allow for bone remodeling and healing.
Tension Fracture
- Cause: Tensile forces applied to the bone, causing it to break apart.
- Occurrence: Can occur in any bone.
- Appearance: Bone breaks apart due to tensile forces.
- Healing Approach: Treatment involves realignment and stabilization to promote proper healing and alignment.
Shear Fracture
- Cause: Occurs when forces are applied parallel to the surface of the bone, causing it to break along the plane of the force.
- Occurrence: Can occur in any bone.
- Appearance: Fracture occurs along a plane parallel to the surface of the bone.
- Healing Approach: Treatment involves realignment and stabilization to promote proper healing and alignment.
Torus Fracture (Buckle Fracture)
- Cause: Compression force applied to the bone, causing it to buckle but not break completely.
- Occurrence: Commonly seen in the metaphyseal region of long bones, especially in children and young animals.
- Appearance: The bone buckles but remains intact.
- Healing Approach: Often heals spontaneously with immobilization and protection of the affected limb.
Cancellous Bone:(Spongey bone)
Cancellous bone, also known as spongy bone or trabecular bone, is one of the two main types of bone tissue found in the human and animal skeletal systems, with the other being compact bone. Cancellous bone is characterized by its porous, honeycomb-like structure, which gives it a sponge-like appearance. This structure is composed of interconnected trabeculae or spicules, which form a network of thin bony plates and rods, creating spaces filled with bone marrow.
The trabeculae of cancellous bone are arranged along lines of stress within the bone, providing strength and support while minimizing weight. Despite its porous nature, cancellous bone is remarkably strong and resilient, capable of withstanding compressive forces and providing structural support to the skeleton.
Cancellous bone is found in the interior regions of bones, particularly in the epiphyses (ends) of long bones, as well as in the interior of flat bones such as the ribs, sternum, and vertebrae. It is also present in the interior of irregular bones and within the diploe of flat bones in the skull.
The spaces within cancellous bone are filled with bone marrow, a soft, gelatinous tissue that contains blood vessels, nerves, and hematopoietic stem cells responsible for the production of blood cells. Red bone marrow, which is involved in hematopoiesis (blood cell formation), is predominantly found within the spaces of cancellous bone in certain bones, such as the pelvis, ribs, vertebrae, and ends of long bones.
Cancellous bone plays several important roles in the skeletal system. It provides structural support and strength to bones while reducing their overall weight, which is particularly important for facilitating movement and agility in animals. Additionally, the presence of red bone marrow within cancellous bone supports the production of red and white blood cells and platelets, contributing to the body’s immune function and oxygen transport.
