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Purdue University Globle
NU551 Advanced Physiology and Pathophysiology Across the Lifespan
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The NU 551 final exam may cover major concepts related to the musculoskeletal system, including bone anatomy, connective tissue, bone remodeling, fractures, joint disorders, bone diseases, and pediatric musculoskeletal conditions. A strong understanding of how bones develop, repair themselves, and respond to disease can help nursing students recognize clinical manifestations and connect them with appropriate nursing concepts. This study guide reviews the most important musculoskeletal topics in a clear, exam-focused format.
Connective tissue supports, connects, and protects structures throughout the body. It is found in bones, cartilage, tendons, ligaments, blood vessels, and many other tissues. Its properties depend on cells, protein fibers, and the extracellular matrix.
Collagen is the most abundant structural protein in the human body. It gives connective tissues strength and helps tissues withstand stretching and mechanical stress. Different types of collagen are concentrated in different tissues.
| Collagen Type | Primary Location | Main Function |
|---|---|---|
| Type I | Bone, skin, tendons, ligaments | Provides tensile strength |
| Type II | Cartilage | Provides structural support and resistance to compression |
| Type III | Skin, blood vessels, reticular fibers | Supports soft tissues and organs |
Type I collagen is particularly important in bone. Defects involving Type I collagen can weaken bone structure, as seen in osteogenesis imperfecta.
Ground substance is the nonfibrous portion of the extracellular matrix surrounding connective tissue cells and fibers. It contains substances such as water, proteoglycans, and glycosaminoglycans. These components help support tissues and facilitate the movement of nutrients and waste products between cells and blood vessels.
Bone is living tissue that constantly undergoes remodeling. Bone formation and bone resorption must remain relatively balanced to maintain skeletal strength and regulate mineral stores.
Osteoblasts are bone-forming cells. They produce osteoid, the organic framework of new bone, and participate in the mineralization process.
Osteoclasts are responsible for bone resorption. They break down bone tissue and help release stored minerals, including calcium and phosphate, into the circulation.
Osteocytes are mature bone cells that develop from osteoblasts. They reside in spaces called lacunae and help maintain the bone matrix. Osteocytes also respond to mechanical stress and participate in signaling involved in bone remodeling.
Osteoid is the newly produced, unmineralized organic portion of the bone matrix. Osteoblasts secrete osteoid before minerals are deposited and the matrix becomes hardened.
Bone combines organic and inorganic materials to provide both flexibility and strength.
The organic portion of bone contains primarily Type I collagen along with other proteins and extracellular matrix components. Collagen provides tensile strength and allows bone to tolerate some degree of flexibility.
Important organic components include:
Type I collagen
Osteoid proteins
Osteocalcin
Proteoglycans
The inorganic component contains mineral salts, particularly calcium and phosphate. These minerals form hydroxyapatite crystals, which provide bone with hardness and resistance to compression.
Major inorganic components include:
Hydroxyapatite
Calcium phosphate
Calcium carbonate
Magnesium and other minerals
Osteocalcin is a protein produced primarily by osteoblasts. It is incorporated into the bone matrix and is associated with bone mineralization and regulation of mineral metabolism.
The skeleton contains two major types of osseous tissue: compact bone and spongy bone.
| Feature | Compact Bone | Spongy Bone |
|---|---|---|
| Structure | Dense and organized | Porous and composed of trabeculae |
| Common location | Shaft of long bones | Ends of long bones and interior of many flat bones |
| Major role | Provides strength and structural support | Supports bone while reducing weight and providing spaces for marrow |
Compact bone is particularly important for resisting mechanical stress. Spongy bone, also called cancellous or trabecular bone, is lighter and contains spaces that can accommodate bone marrow.
The adult human skeleton normally contains 206 bones. These bones are organized into the axial and appendicular skeletons.
The axial skeleton forms the central framework of the body and includes the:
Skull
Vertebral column
Ribs
Sternum
Its major functions include protecting the brain, spinal cord, heart, lungs, and other vital structures.
The appendicular skeleton includes the bones of the:
Upper limbs
Lower limbs
Shoulder girdle
Pelvic girdle
These structures are primarily involved in movement and locomotion.
Long bones are organized into several important regions.
| Region | Description |
|---|---|
| Diaphysis | The long central shaft of a long bone, composed primarily of compact bone |
| Metaphysis | Region between the diaphysis and epiphysis; in growing children it is adjacent to the growth plate |
| Epiphysis | Enlarged end of a long bone that contributes to joint formation |
During childhood and adolescence, longitudinal bone growth occurs at the epiphyseal growth plate. Once skeletal maturity is reached, the growth plates close and become epiphyseal lines.
Compact bone contains microscopic structures that provide strength while allowing nutrients and blood vessels to reach bone cells.
An osteon, or Haversian system, is the basic structural unit of compact bone. It contains a central canal surrounded by layers of bone matrix.
Important osteon structures include:
Central Haversian canal
Concentric lamellae
Lacunae
Osteocytes
Canaliculi
Volkmann canals, also called perforating canals, connect the vascular and nervous structures of compact bone with the central canals of osteons. They generally run perpendicular to the Haversian canals.
Lamellae are layers of mineralized bone matrix. Lacunae are small spaces within the bone matrix that contain osteocytes.
Tiny channels called canaliculi connect lacunae and allow communication and exchange between osteocytes.
Bone development occurs through processes called ossification. Long bones primarily develop through endochondral ossification, in which a cartilage model is gradually replaced by bone.
Important structures include the cartilage model, developing bone collar, and epiphyseal growth plate.
The growth plate is a region of cartilage responsible for longitudinal growth of long bones during childhood and adolescence. Damage to a growth plate can potentially interfere with normal bone growth.
Joints can be classified according to the tissues connecting the bones and the degree of movement permitted.
A syndesmosis is a fibrous joint in which bones are connected by ligaments or an interosseous membrane. The distal tibiofibular joint is an example.
A synchondrosis is a cartilaginous joint in which bones are connected by hyaline cartilage. The epiphyseal growth plate is an important example during skeletal development.
A fracture is a break or disruption in the continuity of a bone. Fractures can be classified according to their pattern, location, severity, and whether the skin has been disrupted.
Common fracture patterns include:
Transverse: Fracture line runs approximately perpendicular to the long axis of the bone.
Oblique: Fracture line runs diagonally.
Spiral: Fracture winds around the bone and is commonly associated with twisting forces.
Comminuted: Bone breaks into multiple fragments.
Greenstick: Incomplete fracture in which one side of the bone bends while the other side breaks.
Greenstick fractures are particularly common in children because growing bones are generally more flexible than mature adult bones.
Fracture healing is a coordinated process involving inflammation, tissue repair, new bone formation, and remodeling.
Immediately after a fracture, blood vessels are damaged and bleeding occurs at the injury site. The resulting blood collection forms a fracture hematoma and initiates the inflammatory response.
Fibroblasts and other repair cells begin producing connective tissue and cartilage. This soft callus helps stabilize the fracture while new tissue develops.
Osteoblast activity increases as the soft callus is gradually replaced by new bone. The resulting hard or bony callus provides greater stability.
Over time, immature woven bone is remodeled into stronger, more organized lamellar bone. Remodeling can continue for an extended period as the bone gradually adapts to mechanical demands.
Several factors can interfere with normal bone repair. Smoking, inadequate nutrition, poor blood supply, infection, diabetes, certain medications, and inadequate stabilization can increase the risk of delayed healing.
Three important complications are:
| Complication | Meaning |
|---|---|
| Delayed union | The fracture takes longer than expected to heal |
| Malunion | The fracture heals but in an abnormal alignment |
| Nonunion | The fracture fails to achieve normal healing |
Musculoskeletal injuries can involve joints, ligaments, tendons, or muscles.
A subluxation is a partial displacement of a joint. A dislocation occurs when the joint surfaces become completely displaced from their normal relationship.
Both conditions may cause pain, swelling, reduced range of motion, and functional impairment.
A strain affects a muscle or tendon, whereas a sprain involves injury to a ligament.
This distinction is commonly tested in nursing examinations.
Repeated mechanical stress can produce soft-tissue disorders such as:
Carpal tunnel syndrome
Tendinitis
Bursitis
Symptoms commonly include localized pain, inflammation, stiffness, weakness, or reduced function depending on the affected structure.
Several diseases affect bone mineralization, density, blood supply, or remodeling.
Osteomalacia is characterized by inadequate mineralization of mature bone. Vitamin D deficiency is an important cause because vitamin D is necessary for normal calcium and phosphate metabolism.
Common manifestations include bone pain, muscle weakness, and an increased risk of fractures.
Osteoporosis is a skeletal disorder characterized by decreased bone strength and increased susceptibility to fractures. Bone mass and microarchitecture are compromised, making bones more fragile.
Risk factors include:
Older age
Postmenopausal status
Low physical activity
Smoking
Low calcium or vitamin D intake
Family history
Long-term glucocorticoid use
Medications associated with increased osteoporosis risk can include long-term glucocorticoids, some anticonvulsants, aromatase inhibitors, and other therapies depending on duration and patient factors.
Common osteoporotic fractures involve the hip, vertebrae, and wrist.
Osteomyelitis is an infection involving bone. It may occur through direct contamination, such as an open fracture or surgical procedure, or through spread from another site through the bloodstream.
Staphylococcus aureus is the most common bacterial cause of osteomyelitis.
Clinical manifestations can include localized bone pain, swelling, warmth, fever, and impaired function. Treatment depends on the causative organism and may include antimicrobial therapy and, in some cases, surgical intervention.
Paget disease is a chronic disorder of bone remodeling characterized by excessive and disorganized bone turnover. The affected bone may become enlarged and structurally abnormal.
Possible manifestations include:
Bone pain
Bone deformities
Pathologic fractures
Increased skull size
Hearing impairment when the skull is affected
Osteosarcoma is a malignant bone tumor that occurs most frequently in children, adolescents, and young adults. It commonly develops near the metaphysis of long bones, particularly around the knee.
Imaging may show aggressive bone formation and a characteristic sunburst pattern in some cases.
Giant cell tumor of bone is generally a locally aggressive tumor that most commonly affects adults between approximately 20 and 40 years of age. It often develops near the end of a long bone, particularly around the knee.
Gout is an inflammatory arthritis caused by deposition of monosodium urate crystals in joints and other tissues.
A typical acute gout attack may involve:
Sudden severe joint pain
Swelling
Redness
Warmth
Significant tenderness
The first metatarsophalangeal joint, commonly known as the big toe joint, is a classic site of acute gout.
Ankylosing spondylitis is a chronic inflammatory condition that primarily affects the axial skeleton, particularly the sacroiliac joints and spine.
Typical manifestations include chronic inflammatory low back pain, morning stiffness, and reduced spinal mobility. Symptoms often improve with physical activity rather than prolonged rest.
Rheumatoid arthritis and osteoarthritis both cause joint symptoms but have different underlying mechanisms.
| Feature | Rheumatoid Arthritis | Osteoarthritis |
|---|---|---|
| Primary mechanism | Autoimmune inflammatory disease | Degenerative joint disease |
| Joint pattern | Often symmetrical | Frequently affects joints according to mechanical stress and may be asymmetric |
| Morning stiffness | Often prolonged, commonly more than 30–60 minutes | Usually brief, often less than 30 minutes |
| Systemic manifestations | May occur | Generally absent |
| Inflammation | Prominent | Usually less systemic inflammatory activity |
Rheumatoid arthritis can produce prolonged morning stiffness, joint swelling, fatigue, and systemic manifestations. Osteoarthritis is commonly associated with activity-related pain, stiffness after inactivity, and progressive cartilage and joint changes.
Rhabdomyolysis occurs when skeletal muscle fibers break down and release intracellular contents, including myoglobin, into the bloodstream. Severe cases can cause acute kidney injury and electrolyte abnormalities.
Common findings include:
Muscle pain
Muscle weakness
Swelling
Dark or tea-colored urine
Markedly elevated creatine kinase
Prompt recognition and treatment are important because complications can become life-threatening.
Musculoskeletal disorders in children can be congenital, developmental, inflammatory, metabolic, or related to growth and overuse.
Rickets occurs when growing bones fail to mineralize properly during childhood. Vitamin D deficiency is a major cause.
Possible manifestations include:
Bowed legs
Delayed growth
Bone pain
Muscle weakness
Skeletal deformities
Adequate vitamin D, calcium, and appropriate treatment of the underlying cause are important for preventing complications.
Genu varum produces a bow-legged appearance, while genu valgum produces a knock-kneed appearance.
Some degree of angular alignment can be normal at different stages of childhood development. Persistent, severe, asymmetric, or symptomatic deformity requires clinical evaluation.
Syndactyly is the congenital fusion or webbing of adjacent fingers or toes.
Polydactyly refers to the presence of extra fingers or toes.
The severity and treatment depend on the anatomy involved and whether function is affected.
Talipes equinovarus, commonly called clubfoot, is a congenital foot deformity. The foot is typically positioned in a combination of inward rotation, plantar flexion, and other structural abnormalities.
Treatment often begins early and may include serial casting followed by bracing. Surgery may be considered in selected cases.
Pes planus, commonly called flatfoot, occurs when the medial longitudinal arch of the foot is reduced or appears flattened.
Flexible flat feet can be a normal developmental finding in children and do not always require treatment. Persistent pain or functional problems may warrant further assessment.
Scoliosis is an abnormal lateral curvature of the spine.
Structural scoliosis involves a fixed curvature associated with structural changes in the vertebrae or spine.
Functional scoliosis is caused by another condition, such as leg-length discrepancy or muscle spasm, and the curvature may improve when the underlying cause is corrected.
Screening and follow-up depend on the child’s age, degree of curvature, symptoms, and risk of progression.
Juvenile idiopathic arthritis is a group of inflammatory arthritic conditions beginning during childhood. It can cause persistent joint swelling, pain, stiffness, and limitations in movement.
Commonly affected joints include the knees, ankles, and wrists, although patterns vary between disease subtypes.
Early recognition and treatment can help reduce inflammation and protect joint function.
Osgood-Schlatter disease is an overuse condition commonly seen in physically active children and adolescents during periods of rapid growth.
Repeated traction from the patellar tendon at the tibial tubercle can produce localized pain and swelling below the knee. Symptoms often worsen with activities such as running, jumping, or climbing stairs.
Legg-Calvé-Perthes disease involves temporary disruption of the blood supply to the femoral head, resulting in avascular necrosis.
Possible manifestations include:
Hip or groin pain
Limping
Limited hip range of motion
Referred pain to the thigh or knee
Early diagnosis and appropriate orthopedic management are important for preserving hip function.
Muscular dystrophies are inherited disorders characterized by progressive muscle weakness and degeneration.
Important types include:
Duchenne muscular dystrophy
Becker muscular dystrophy
Myotonic dystrophy
Limb-girdle muscular dystrophy
Becker muscular dystrophy generally has a later onset and slower progression than Duchenne muscular dystrophy, although disease severity can vary considerably.
Osteogenesis imperfecta is an inherited connective tissue disorder most commonly associated with abnormalities involving Type I collagen.
The condition causes increased bone fragility and recurrent fractures. Other manifestations can include short stature, hearing abnormalities, dental problems, and blue or gray sclerae, depending on the type.
Developmental dysplasia of the hip involves abnormal development or instability of the hip joint. It ranges from mild instability to complete dislocation.
Risk factors can include:
Breech presentation
Female sex
Family history
Firstborn status
Early detection is important because untreated hip dysplasia can lead to abnormal gait, pain, and degenerative changes later in life.
For final-exam preparation, several distinctions are especially important. Osteoblasts build bone, osteoclasts resorb bone, and osteocytes maintain mature bone. Type I collagen provides the primary organic framework of bone, while hydroxyapatite contributes hardness and resistance to compression.
Students should also be able to distinguish common musculoskeletal injuries and disorders. A sprain affects a ligament, while a strain affects a muscle or tendon. A subluxation is a partial joint displacement, whereas a dislocation is complete displacement. Osteoporosis involves reduced bone strength, osteomalacia involves inadequate mineralization, and osteomyelitis involves infection of bone.
In pediatric nursing, recognizing developmental and growth-related disorders is equally important. Rickets is associated with impaired mineralization, clubfoot is a congenital foot deformity, Osgood-Schlatter disease is related to repetitive traction during growth, and Legg-Calvé-Perthes disease involves avascular necrosis of the femoral head.
Type I collagen forms the major organic framework of bone and provides tensile strength. Mineral crystals are deposited within this matrix, contributing to the bone’s overall hardness and strength.
Osteoblasts form new bone, osteoclasts resorb bone, and osteocytes maintain mature bone and participate in bone remodeling.
Compact bone is dense and provides substantial structural strength. Spongy bone contains trabeculae and spaces that reduce skeletal weight and accommodate bone marrow.
The major stages are hematoma formation, fibrocartilaginous callus formation, bony callus formation, and bone remodeling.
A sprain is an injury to a ligament, whereas a strain involves a muscle or tendon.
Staphylococcus aureus is the most common bacterial pathogen associated with osteomyelitis.
Osteoporosis involves reduced bone mass and compromised bone strength, increasing fracture risk. Osteomalacia involves inadequate mineralization of bone, commonly associated with vitamin D deficiency in adults.
Acute gout typically causes sudden, severe pain with swelling, redness, warmth, and tenderness in an affected joint. The first metatarsophalangeal joint is a classic location.
Rheumatoid arthritis is an autoimmune inflammatory disease that often causes symmetrical joint involvement and prolonged morning stiffness. Osteoarthritis is primarily a degenerative joint disorder associated with cartilage and structural changes and commonly produces activity-related pain.
Osteogenesis imperfecta is associated with abnormalities in Type I collagen and causes fragile bones and recurrent fractures.
The musculoskeletal system depends on the coordinated function of bone cells, collagen, minerals, joints, muscles, tendons, and ligaments. Understanding the normal structure and physiology of these tissues makes it easier to recognize disease-related changes.
For exam preparation, focus especially on the following high-yield relationships:
Osteoblasts → bone formation
Osteoclasts → bone resorption
Osteocytes → bone maintenance and remodeling signaling
Type I collagen → tensile strength
Hydroxyapatite → bone hardness
Sprain → ligament injury
Strain → muscle or tendon injury
Subluxation → partial joint displacement
Dislocation → complete joint displacement
Osteoporosis → reduced bone strength and increased fracture risk
Osteomalacia → impaired bone mineralization
Osteomyelitis → bone infection
Gout → monosodium urate crystal deposition
Rickets → impaired mineralization of growing bone
Osteogenesis imperfecta → Type I collagen disorder
Osgood-Schlatter disease → traction-related tibial tubercle pain during growth
Legg-Calvé-Perthes disease → avascular necrosis of the femoral head
A strong NU 551 study strategy is to learn these concepts by connecting normal anatomy → pathophysiology → clinical manifestations → distinguishing features. This approach makes it easier to answer application-based nursing questions rather than relying only on memorization.
American Academy of Orthopaedic Surgeons. (n.d.). Bone health basics. OrthoInfo. https://orthoinfo.aaos.org/en/staying-healthy/bone-health-basics/
American Academy of Orthopaedic Surgeons. (n.d.). Fractures. OrthoInfo. https://orthoinfo.aaos.org/en/diseases–conditions/fractures/
National Institute of Arthritis and Musculoskeletal and Skin Diseases. (n.d.). Bone health and osteoporosis. National Institutes of Health. https://www.niams.nih.gov/health-topics/osteoporosis
National Institute of Arthritis and Musculoskeletal and Skin Diseases. (n.d.). Osteoarthritis. National Institutes of Health. https://www.niams.nih.gov/health-topics/osteoarthritis
National Institute of Arthritis and Musculoskeletal and Skin Diseases. (n.d.). Rheumatoid arthritis. National Institutes of Health. https://www.niams.nih.gov/health-topics/rheumatoid-arthritis
National Institutes of Health, Office of Dietary Supplements. (2024). Vitamin D: Fact sheet for health professionals. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
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