Bone Growth and Disorders Quiz

Skeletal System Components

• Four components are bone (spongy and compact), cartilage (hyaline, fibrocartilage, elastic), tendons (dense regular CT), and ligaments (dense regular CT).

Functions of the Skeletal System

• Protection: The skeleton protects vital organs like the brain.
• Mineral Storage & Acid-Base Homeostasis: Bones store minerals (calcium and phosphate) crucial for electrolyte and acid-base balance.
• Blood Cell Formation: Red bone marrow produces blood cells (red blood cells, white blood cells, and platelets).
• Fat Storage: Yellow bone marrow stores triglycerides.
• Movement: Skeletal muscles, attached to bones, produce movement via contractions.
• Support: The skeleton supports the weight of the body and provides structural framework. -Supports soft tissues.
• Provides attachment points for tendons of skeletal muscle.

Functions of Bone and Skeletal System

• Support: Structural framework of the body; supports body’s weight and soft tissues; provides tendon and skeletal muscle attachments.
• Protection: Protects internal organs (Cranium protects brain, Vertebrae protects spinal cord, Ribs protect lungs and heart).

Assistance in Movement

• Skeletal muscles attach to bones.
• Skeletal muscle contraction causes bone movement.

Mineral Homeostasis

• Bone tissue stores minerals.
• Acts as a reservoir of critical minerals like calcium (99% of body content) and phosphorus.

Blood Cell Production

• Red bone marrow produces red blood cells, white blood cells, and platelets (hemopoiesis).
• Yellow bone marrow stores triglycerides.
• Serves as a potential energy reserve.

Classification of Bones

• Long bones: Longer than wide (e.g., humerus).
• Short bones: About as long as wide (e.g., carpals).
• Flat bones: Broad, flat, and thin (e.g., sternum).
• Irregular bones: Shape doesn't fit other categories (e.g., vertebrae).
• Sesamoid bones: Round, flat bones within tendons (e.g., patella).

Structure of Long Bones

• Epiphysis: End of the bone; contains red marrow.
• Diaphysis: Shaft of the bone; contains yellow marrow and compact bone.
• Medullary cavity: Central cavity of the diaphysis containing marrow.
• Compact bone: Dense, solid outer layer.
• Spongy bone: Inner layer with a lattice-like structure.
• Periosteum: Tough, fibrous covering on the outer surface of the bone.
• Endosteum: A membrane lining the inner surface of bone.

Blood and Nerves Supply of Bone Tissue

• Blood supply comes from periosteal arteries accompanied by nerves.
• Epiphyseal veins carry blood away from long bones.
• Periosteum contains sensory nerves sensitive to tearing or tension.

Short, Irregular, and Flat Bone Structure

• Contain bone marrow but lack a marrow cavity.
• Consist of compact bone covering spongy bone (diploe).

Bone Marrow

• Red bone marrow: Forms hematopoietic cells.
• Decreases with age.
• Found in pelvis, proximal femur/humerus, vertebrae, ribs, sternum, and some skull bones.
• Yellow bone marrow: Stores triglycerides.
• Blood vessels and adipocytes.

Bone Marrow Transplantation

• Treatment for certain blood diseases (leukemia, sickle-cell anemia, aplastic anemia).
• Involves inserting a needle into the pelvic bone of a matching donor, withdrawing red marrow, destroying recipient's marrow, intravenously introducing donor marrow, cells traveling to marrow cavities, and new blood cell production in ~ 2-4 weeks if successful.
• Complications: Flu-like symptoms, infection, and transplant rejection.

Peripheral Blood Stem Cell Donation

• Alternative to bone marrow transplant.
• Donor receives an injection that stimulates the release of hematopoietic stem cells into blood.
• Blood is removed, hematopoietic cells are filtered, and blood is returned to the donor.
• Similar to plasma donation.

Inorganic Composition of Bone Tissue

• Makes up 65% of bone tissue.
• Primarily composed of hydroxyapatite (calcium phosphate salt).
• Stores significant amounts of calcium and phosphorus.
• Strong & resistant to compression.
• Allows bone to be both protective and supportive.

Organic Composition of Bone Tissue

• Composed of cells, collagenous fibers, proteoglycans, and glycoproteins.
• 35% of bone tissue.

Importance of Bone Matrix

• Organic matrix: Essential for flexibility/resistance to twisting and bending.
• Inorganic matrix: Essential for compression resistance.

Two Forms of Bone Tissue

• Compact bone (lamellar bone): Solid external layer, resists high stress, composed of osteons (Haversian systems), lamellae, lacunae, osteocytes, canaliculi, central (Haversian) canals, perforating canals.
• Spongy bone (trabecular bone): Internal to compact bone, resists stress from multiple directions, forms a protective framework around bone marrow. Contains spaces, like a honeycomb, filled with red or yellow marrow.

Osteon Structure

• Lamellae: Thin layers of bone matrix arranged concentrically around a central canal (Haversian canal).
• Central (Haversian) canal: Contains blood vessels and nerves.
• Lacunae: Small cavities containing osteocytes.
• Canaliculi: Tiny canals connecting lacunae, allowing osteocytes to communicate.

Ossification (Osteogenesis)

• Primary (woven) bone: Irregularly arranged collagen fibers, abundant osteocytes.
• Secondary (lamellar) bone: Stronger structure, organized collagen fibers, high proportion of inorganic matrix.
• Replacement occurs in most areas.

Intramembranous Ossification

• Development of flat bones of skull and clavicle.
• Mesenchymal cells differentiate into osteogenic cells and then osteoblasts which deposit organic matrix.
• Calcification occurs to form primary bone and some mesenchyme differentiates into periosteum.
• Osteoblasts in periosteum form compact bone.

Endochondral Ossification

• Development of most bones (except flat bones).
• Hyaline cartilage model forms.
• Cartilage ECM is broken down and replaced by bone.
• Primary ossification centers develop, calcified cartilage is replaced by bone, secondary ossification centers develop, epiphyses finish ossifying, allowing bone growth in length.
• Chondroblasts in perichondrium become osteoblasts and build bone collar externally.

Growth of Bone in Length and Width

• Interstitial growth: Lengthens long bones, occurs at epiphyseal plate where chondrocytes divide, secrete matrix, then enlarge, and die as matrix calcifies.
• Appositional growth: Increases bone width, chondroblasts in surrounding perichondrium produce new cartilage, epiphyseal line forms as a remnant of the epiphyseal plate.

Growth of Long Bone at Epiphyseal Plate

• Zones of reserve cartilage, proliferation, hypertrophy and maturation, calcification, and ossification.
• Key features are present in each zone, that lead to bone growth in length.

Factors Affecting Bone Growth

• Genetics: Determine bone shape and size.
• Hormones: Growth factors (IGFs) stimulate osteoblasts; thyroid hormones, insulin, and sex hormones (estrogen & testosterone) promote bone growth & affect development stages.
• Nutrition: Essential minerals (calcium, phosphorus, manganese, magnesium, and fluoride) and vitamins (Vitamins A, C, D, K, and B12) are necessary for bone growth and remodeling.

Hormones Affecting Bone Growth

• Growth factors (IGFs): Stimulate osteoblast activity (produced by the liver).
• Thyroid hormones: Required for normal growth of all tissues.
• Insulin: Promotes bone growth by stimulating osteoblasts.
• Sex hormones (estrogen/testosterone): Trigger growth spurts during teenage years, promote bone growth.

Effects of Growth Hormone on Body Tissues

• Short-term effects: Influence on skeletal muscle, liver, glucose & fatty acid levels.
• Long-term effects: Stimulate cell division & protein synthesis, leading to increased growth of bones and other tissues.

Excess Growth Hormone (Gigantism/Acromegaly)

• Childhood (Gigantism): Excessive GH before epiphyseal plate closure, extreme height, early death risk.
• Adulthood (Acromegaly): Excess GH after epiphyseal plate closure, bone, cartilage, and soft tissue enlargement.

Pituitary Dwarfism

• Insufficient GH secretion prior to epiphyseal plate closure, short stature with proportional limbs and trunk.

Achondroplasia

• Genetic disorder affecting cartilage growth.
• Results in short stature (~4 feet).

Bone Remodeling

• Continuous process of bone formation and loss after growth finishes, bone is continuously reformed.
• New bone is formed via bone deposition, old bone is removed by bone resorption. •
• Reasons: Maintenance of calcium homeostasis, repair of primary bone with secondary bone, replacement of old brittle bone with newer bone, and adaptation to tension and stress.

Factors Affecting Bone Growth - Nutrition

• Minerals: Large amounts of calcium and phosphorus, smaller amounts of manganese, magnesium, and fluoride are needed.
• Vitamins: Vitamin D helps absorb calcium, Vitamin A stimulates osteoblast activity, Vitamin C is needed for collagen synthesis. Vitamins K, and B12 assist synthesis of bone proteins.

Role of Calcium in the Body

• Nerve impulse transmission, muscle contraction, blood coagulation, cell division and gland/nerve cell secretion.

Hormonal Control

• Parathyroid hormone (PTH): Released when blood calcium decreases, stimulating osteoclasts to release calcium from bone into blood.
• Calcitonin: Produced by thyroid gland, temporarily lowers blood calcium if given in high doses.

Homeostasis: Response to Low Blood Calcium

• Parathyroid glands detect low blood calcium, increase PTH release.
• PTH stimulates osteoclasts to resorb bone.
• Kidneys retain calcium, intestines absorb more calcium.
• The calcium levels return to the normal range, the release of PTH decreases.

How Does Bone Adjust to Mechanical Stress?

• Increase bone mass: Weight-bearing activities (walking, running, lifting weights) increase osteoblast activity, leading to denser bones.
• Decrease bone mass: Removing mechanical stress reduces collagen formation and Ca2+ levels, decreasing osteoblast activity, leading to less dense bones.

Effects of Aging on Bone Tissue

• Reduced sex hormone levels during middle age, especially in women after menopause, lead to decreased bone mass.
• Bone resorption (osteoclasts) outpaces bone deposition (osteoblasts).
• Females tend to be have smaller, less massive bones than males.

Disorders of Bones

• Osteoporosis: Low bone mass, bone reabsorption outpaces deposition, more common in post-menopausal women.
• Osteomalacia: Inability to absorb fats, particularly Vitamin D, causing bones to be inadequately mineralized.
• Rickets: Childhood form of osteomalacia.
• Paget's disease: Excessive rate of bone deposition; characterized by excessive rate of bone deposition.
• Osteosarcoma: Malignant bone cancer.

Fracture and Repair of Bone

• Fracture types: Open (compound), closed (simple), comminuted, greenstick, impacted, Pott's, Colles', stress, avulsion.
• Healing process: Hematoma formation, soft callus formation (fibroblasts, chondroblasts leading to hyaline cartilage and collagenous connective tissue), hard callus formation (osteoblasts deposit bone matrix), remodeling of bone callus replacing primary bone with secondary bone.

Test your knowledge on the various types of bone growth, fractures, and disorders. This quiz covers topics such as chondrocytes, osteoporosis, and the structural components of bone. Perfect for anatomy or biology students looking to reinforce their understanding of the skeletal system.