Bone Markings and Structures Quiz

Bone Markings

• Erosity: Rounded projection
• Crest: Narrow, prominent ridge of bone
• Trochanter: Large, blunt, irregular surface
• Line: Narrow ridge of bone
• Tubercle: Small rounded projection
• Epicondyle: Raised area above a condyle
• Spine: Sharp, slender projection
• Process: Any bony prominence
• Head: Bony expansion carried on a narrow neck
• Facet: Smooth, nearly flat articular surface
• Condyle: Rounded articular projection
• Ramus: Armlike bar of bone
• Meatus: Canal-like passage
• Sinus: Cavity within bone
• Fossa: Shallow basin-like depression
• Groove: Furrow
• Fissure: Narrow, slit-like opening
• Foramen: Round or oval opening through bone

Bone Texture

• Compact bone: Dense outer layer
• Spongy bone: Honeycomb of trabeculae filled with yellow bone marrow

Structure of Long Bones

• Diaphysis: Tubular shaft that forms the axis of long bones
  • Composed of compact bone that surrounds the medullary cavity
  • Contains yellow bone marrow (fat)
• Epiphyses: Expanded ends of long bones
  • Exterior is compact bone, and the interior is spongy bone
  • Joint surface is covered with articular (hyaline) cartilage
  • Epiphyseal line separates the diaphysis from the epiphyses

Bone Membranes

• Periosteum: Double-layered protective membrane
  • Outer fibrous layer is dense regular connective tissue
  • Inner osteogenic layer is composed of osteoblasts and osteoclasts
  • Richly supplied with nerve fibers, blood, and lymphatic vessels
  • Secured to underlying bone by Sharpey's fibers
• Endosteum: Delicate membrane covering internal surfaces of bone

Structure of Short, Irregular, and Flat Bones

• Thin plates of periosteum-covered compact bones on the outside with endosteum-covered spongy bone (diploe) on the inside
• Have no diaphysis or epiphysis
• Contain bone marrow between the trabeculae

Hematopoietic Tissue (Red Marrow)

• Infants: Found in the medullary cavity and all areas of spongy bone
• Adults: Found in the diploe of flat bones, and the head of the femur and humerus

Bone Development

• Intramembranous Ossification: Bone develops directly from mesenchymal tissue
• Endochondral Ossification: Bone develops from hyaline cartilage
  • Formation of the bony collar
  • Cavitation of the cartilage
  • Invasion of the internal cavities by the periosteal bud, and spongy bone formation
  • Formation of the medullary cavity, appearance of secondary ossification centers in the epiphyses
  • Ossification of the epiphyses, with hyaline cartilage remaining only in the epiphyseal plates

Postnatal Bone Growth

• Growth in length of long bones:
  • Cartilage on the epiphyseal plate closest to the epiphysis is relatively inactive
  • Cartilage abutting the shaft of the bone organizes into a pattern that allows fast, efficient growth
  • Cells of the epiphyseal plate proximal to the resting cartilage form three functionally different zones: growth, transformation, and osteogenic

Functional Zones in Long Bone Growth

• Growth zone: Cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis
• Transformation zone: Older cells enlarge, the matrix becomes calcified, cartilage cells die, and the matrix begins to deteriorate
• Osteogenic zone: New bone formation occurs

Long Bone Growth and Remodeling

• Growth in length: Cartilage continually grows and is replaced by bone
• Remodeling: Bone is resorbed and added by appositional growth

Hormonal Regulation of Bone Growth During Youth

• Infancy and childhood: Epiphyseal plate activity is stimulated by growth hormone
• Puberty: Testosterone and estrogens
  • Initially promote adolescents growth spurts
  • Cause masculinization and feminization of specific parts of the skeleton
  • Later induce epiphyseal plate closure, ending longitudinal bone growth

Bone Remodeling

• Remodeling units: Adjacent osteoblasts and osteoclasts deposit and resorb bone at periosteal and endosteal surfaces

Bone Deposition

• Occurs where bone is injured or added strength is needed
• Requires a diet rich in protein, calcium, phosphorus, magnesium, and manganese
• Alkaline phosphatase is essential for mineralization
• Sites of new matrix deposition are revealed by the:
  • Osteoid seam: unmineralized band of bone matrix
  • Calcification front: abrupt transition zone between the osteoid seam and the older mineralized bone

Bone Resorption

• Accomplished by osteoclasts
• Resorption bays: grooves by osteoclasts as they break down bone matrix
• Resorption involves osteoclast secretion of:
  • Lysosomal enzymes that digest organic matrix
  • Acids that convert calcium salts into soluble forms
• Dissolved matrix is transcytosed across the osteoclast's cell where it is secreted into the interstitial fluid and then into the blood

Importance of Ionic Calcium in the Body

• Calcium is necessary for:
  • Transmission of nerve impulses
  • Muscle contraction
  • Blood coagulation
  • Secretion by glands and nerve cells
  • Cell division

Carpopedal Spasm

• Hypocalcemia causing overexcitability of the nervous system and muscle spasm of hands and feet

Control of Remodeling

• Two control loops regulate bone remodeling:
  • Hormonal mechanism maintains calcium homeostasis in the blood
  • Mechanical and gravitational forces acting on the skeleton

Hormonal Mechanism

• Rising blood Ca2+ levels trigger the thyroid to release calcitonin
• Calcitonin stimulates calcium salt deposit in bone
• Falling blood Ca2+ levels signal the parathyroid glands to release PTH
• PTH signals osteoclasts to degrade bone matrix and release Ca2+ into the blood

Calcitriol Synthesis & Action

• Calcitriol (active form of vitamin D) increases blood Ca2+ levels:
  • Stimulates intestinal Ca2+ absorption
  • Enhances osteoclast activity
  • Promotes reabsorption of Ca2+ by the kidneys

Response to Mechanical Stress

• Wolff's law: A bone grows or remodels in response to the forces or demands placed upon it
• Observations supporting Wolff's law include:
  • Long bones are thickest midway along the shaft (where bending stress is greatest)
  • Curved bones are thickest where they are most likely to buckle
• Trabeculae form along lines of stress
• Large, bony projections occur when heavy, active muscles attach

Bone Fractures (Breaks)

• Classified by:
  • Position of the bone ends after fracture
  • Completeness of the break
  • Orientation of the bone to the long axis
  • Whether or not the bone ends penetrate the skin

Types of Bone Fractures

• Nondisplaced: Bone ends retain their normal position
• Displaced: Bone ends are out of normal alignment
• Complete: Bone is broken all the way through
• Incomplete: Bone is not broken all the way through
• Linear: The fracture is parallel to the long axis of the bone
• Transverse: The fracture is perpendicular to the long axis of the bone
• Compound (open): Bone ends penetrate the skin
• Simple (closed): Bone ends do not penetrate the skin

Common Types of Fractures

• Comminuted: Bone fragments into three or more pieces; common in the elderly
• Spiral: Ragged break when bone is excessively twisted; common sports injury
• Depressed: Broken bone portion pressed inward; typical skull fracture
• Compression: Bone is crushed; common in porous bones
• Epiphyseal: Epiphysis separates from diaphysis along epiphyseal lines; occurs where cartilage cells are dying
• Greenstick: Incomplete fracture where one side of the bone breaks and the other side bends; common in children

Stages in the Healing of a Bone Fracture

• Hematoma formation:
  • Torn blood vessels hemorrhage
  • A mass of clotted blood (hematoma) forms at the fracture site
  • Site becomes swollen, painful, and inflamed
• Fibrocartilaginous callus formation:
  • Granulation tissue (soft callus) forms a few days after the fracture
  • Capillaries grow into the tissue and phagocytic cells begin cleaning debris
  • Osteoblasts and fibroblasts migrate to the fracture and begin reconstructing the bone
  • Fibroblasts secrete collagen fibers that connect broken bone ends
  • Osteoblasts begin forming spongy bone
  • Osteoblasts furthest from capillaries secrete an externally bulging cartilaginous matrix that later calcifies
• Bony callus formation:
  • New bone trabeculae appear in the fibrocartilaginous callus
  • Fibrocartilaginous callus converts into a bony (hard) callus
  • Bone callus begins 3-4 weeks after injury, and continues until firm union is formed 2-3 months later
• Bone remodeling:
  • Excess material on the bone shaft exterior and in the medullary canal is removed
  • Compact bone is laid down to reconstruct shaft walls

Healing of Fractures

• Normally healing takes 8-12 weeks (longer in the elderly)
• Stages of healing:
  • Fracture hematoma
  • Granulation tissue
  • Callus formation
  • Remodeling

Homeostatic Imbalances

• Osteomalacia: Bones are inadequately mineralized causing softened, weakened bones
  • Main symptom is pain when weight is put on the affected bone
  • Caused by insufficient calcium in the diet, or by vitamin D deficiency
• Rickets (in Children): Bones of children are inadequately mineralized causing softened, weakened bones
  • Bowed legs and deformities of the pelvis, skull, and rib cage are common
  • Caused by insufficient calcium in the diet, or by vitamin D deficiency
• Osteoporosis: Group of diseases in which bone reabsorption outpaces bone deposition
  • Spongy bone of the spine is most vulnerable
  • Occurs most often in postmenopausal women
  • Bones become so fragile that sneezing or stepping off a curb can cause fractures
  • Treatment:
    • Calcium and vitamin D supplements
    • Increased weight-bearing exercise
    • Hormone (estrogen) replacement therapy (HRT)
    • Natural progesterone cream
    • Statins

Isolated Cases of Rickets

• Rickets have been essentially eliminated in the US
• Only isolated cases appear
• Example: Infants of breastfeeding mothers deficient in vitamin D will also be Vitamin D deficient and develop rickets

Paget's Disease

• Characterized by excessive bone formation and breakdown
• Pagetic bone with an excessively high ratio of woven (spongy) to compact bone is formed
• Pagetic bone, along with reduced mineralization, causes spotty weakening of bone
• Osteoclast activity wanes, but osteoblast activity continues to work
• Usually localized in the spine, pelvis, femur, and skull
• Unknown cause (possibly viral)
• Treatment includes the drugs Didronate and Fosamax (also calcitonin by inhalation)

Development Aspects of Bones

• Mesoderm gives rise to embryonic mesenchymal cells, which produce membranes and cartilages that form the embryonic skeleton
• The embryonic skeleton ossifies in a predictable timetable that allows fetal age to be determined

Skeletal Cartilage

• Contains no blood vessels or nerves
• Surrounded by the perichondrium, a dense irregular connective tissue that restricts outward expansion
• Three types of cartilage: hyaline, elastic, and fibrocartilage

Hyaline Cartilage

• Provides support, flexibility, and resilience
• Most abundant skeletal cartilage
• Found in:
  • Articular cartilage: covers the ends of long bones
  • Costal cartilage: connects ribs to the sternum
  • Respiratory cartilage: makes up the larynx and reinforces air passages
  • Nasal cartilage: supports the nose

Elastic Cartilage

• Similar to hyaline cartilage but contains elastic fibers
• Found in the external ear and epiglottis

Fibrocartilage

• Highly compressed with great tensile strength
• Contains collagen fibers
• Found in the menisci of the knee and intervertebral discs

Growth of Cartilage

• Appositional growth: cells in the perichondrium secrete matrix against the external face of existing cartilage
• Interstitial growth: lacunae-bound chondrocytes inside the cartilage divide and secrete new matrix, expanding the cartilage from within
• Calcification of cartilage occurs during normal bone growth and during old age

Classification of Bones

• Axial skeleton: bones of the skull, vertebral column, and rib cage
• Appendicular skeleton: bones of the upper and lower limbs, shoulder, and hip
• Long bones: longer than they are wide (e.g., humerus)
• Short bones: cube-shaped bones of the wrist and ankle, bones that form within tendons (e.g., patella)
• Flat bones: thin, flattened, and slightly curved (e.g., sternum, most skull bones)
• Irregular bones: complicated shapes (e.g., vertebrae, hip bones)

Function of Bones

• Support: forms the framework that supports the body and cradles soft organs
• Protection: provides protective cases for the brain, spinal cord, and vital organs
• Movement: provides levers for muscles
• Mineral storage: reservoir for minerals, especially calcium and phosphorus
• Blood cell formation (hematopoiesis): occurs within the marrow cavities of bones

Bone Markings

• Bulges, depressions, and holes serve as:
  • Sites of attachment for muscles, ligaments, and tendons
  • Joint surfaces
  • Conduits for blood vessels and nerves

Muscle and Ligament Attachment

• Tuberosity: rounded projection
• Crest: narrow, prominent ridge of bone
• Trochanter: large, blunt, irregular surface
• Line: narrow ridge of bone
• Tubercle: small rounded projection
• Epicondyle: raised area above a condyle
• Spine: sharp, slender projection
• Process: any bony prominence
• Head: bony expansion carried on a narrow neck
• Facet: smooth, nearly flat articular surface
• Condyle: rounded articular projection
• Ramus: armlike bar of bone

Passages and Cavities

• Meatus: canal-like passageway
• Sinus: cavity within bone
• Fossa: shallow basin-like depression
• Groove: furrow
• Fissure: narrow, slit-like opening
• Foramen: round or oval opening through bone

Bone Texture

• Compact bone: dense outer layer
• Spongy bone: honeycomb of trabeculae filled with yellow bone marrow

Structure of Long Bones

• Long bones consist of a diaphysis and epiphysis
• Diaphysis:
  • Tubular shaft that forms the axis of long bones
  • Composed of compact bone that surrounds the medullary cavity
  • Yellow bone marrow (fat) is contained in the medullary cavity
• Epiphyses:
  • Expanded ends of long bones
  • Exterior is compact bone, and the interior is spongy bone
  • Joint surface is covered with articular (hyaline) cartilage
  • Epiphyseal line separates the diaphysis from the epiphyses

Bone Membranes

• Periosteum: double-layered protective membrane
  • Outer fibrous layer is dense regular connective tissue
  • Inner osteogenic layer is composed of osteoblasts and osteoclasts
  • Richly supplied with nerve fibers, blood, and lymphatic vessels, which enter the bone via nutrient foramina
  • Secured to underlying bone by Sharpey's fibers
• Endosteum: delicate membrane covering internal surfaces of bone

Structure of Short, Irregular, and Flat Bones

• Thin plates of periosteum-covered compact bones on the outside with endosteum-covered spongy bone (diploe) on the inside
• Have no diaphysis or epiphysis
• Contain bone marrow between the trabeculae

Hematopoietic Tissue (Red Marrow)

• In infants: found in the medullary cavity and all areas of spongy bone
• In adults: found in the diploe of flat bones, and the head of the femur and humerus

Compact Bone

• Haversian system (osteon): the structural unit of compact bone
  • Lamellae: weight-bearing, column-like matrix tubes composed mainly of collagen
  • Haversian (central) canal: central channel containing blood vessels and nerves
  • Volkmann's canals: channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal
• Osteocytes: mature bone cells
• Lacunae: small cavities in bone that contain osteocytes
• Canaliculi: hairlike canals that connect lacunae to each other and the central canal

Chemical Composition of Bone: Organic

• Osteoblasts: bone-forming cells
• Osteocytes: mature bone cells
• Osteoclasts: larger cells that resorb or break down bone matrix
• Osteoid: unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

Chemical Composition of Bone: Inorganic

• Hydroxyapatites (mineral salts): 65% of bone by mass, mainly calcium phosphates, responsible for bone hardness and resistance to compression

Bone Development

• Osteogenesis (ossification): process of bone tissue formation, leading to:
  • Formation of the bony skeleton in embryos
  • Bone growth until early adulthood
  • Bone thickness, remodeling, and repair

Formation of the Bony Skeleton

• Begins at week 8 of embryo development
• Intramembranous ossification: bone develops from a fibrous membrane
• Endochondral ossification: bone forms by replacing hyaline cartilage

Intramembranous Ossification

• Formation of most flat bones of the skull and clavicles
• Fibrous connective tissue membranes are formed by mesenchymal cells

Stages of Intramembranous Ossification

• An ossification center appears in the fibrous connective tissue membrane
• Bone matrix is secreted within the fibrous membrane
• Woven bone and periosteum form
• Bone collar of compact bone forms and red marrow appears

Endochondral Ossification

• Begins in the second month of development
• Uses hyaline cartilage "bones" as models for bone construction
• Requires breakdown of hyaline cartilage prior to ossification

Stages of Endochondral Ossification

• Formation of a bone collar
• Cavitation of the hyaline cartilage
• Invasion of internal cavities by the periosteal bud, and spongy bone formation
• Formation of the medullary cavity, appearance of secondary ossification centers in the epiphyses
• Ossification of the epiphyses, with hyaline cartilage remaining only in the epiphyseal plates

Postnatal Bone Growth

• Growth in length of long bones:
  • Cartilage on the epiphyseal plate closest to the epiphysis is relatively inactive
  • Cartilage abutting the shaft of the bone organizes into a pattern that allows fast, efficient growth
  • Cells of the epiphyseal plate proximal to the resting cartilage form three functionally different zones: growth, transformation, and osteogenic

Functional Zones in Long Bone Growth

• Growth zone: cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis
• Transformation zone: older cells enlarge, the matrix becomes calcified, cartilage cells die, and the matrix begins to deteriorate
• Osteogenic zone: new bone formation occurs

Long Bone Growth and Remodeling

• Growth in length: cartilage continually grows and is replaced by bone
• Remodeling: bone is resorbed and added by appositional growth

Hormonal Regulation of Bone Growth during Youth

• During infancy and childhood: epiphyseal plate activity is stimulated by growth hormone
• During puberty: testosterone and estrogens:
  • Initially promote adolescent growth spurts
  • Cause masculinization and feminization of specific parts of the skeleton
  • Later induce epiphyseal plate closure, ending longitudinal bone growth

Bone Remodeling

• Remodeling units: adjacent osteoblasts and osteoclasts deposit and resorb bone at periosteal and endosteal surfaces

Bone Deposition

• Occurs where bone is injured or added strength is needed
• Requires a diet rich in protein, vitamins C, A, and D, and calcium, phosphorus, magnesium, and manganese
• Alkaline phosphatase is essential for mineralization
• Sites of new matrix deposition are revealed by the:
  • Osteoid seam: unmineralized band of bone matrix
  • Calcification front: abrupt transition zone between the osteoid seam and the older mineralized bone

Bone Resorption

• Accomplished by osteoclasts
• Resorption bays: grooves made by osteoclasts as they resorb bone

Homeostatic Imbalances

• Osteomalacia:
  • Bones are inadequately mineralized, causing softened, weakened bones (osteoid without minerals)
  • Main symptom is pain when weight is put on the affected bone
  • Caused by insufficient calcium in the diet or vitamin D deficiency
• Rickets (in children):
  • Bones of children are inadequately mineralized, causing softened, weakened bones
  • Bowed legs and deformities of the pelvis, skull, and rib cage are common
  • Caused by insufficient calcium in the diet or vitamin D deficiency
• Osteoporosis:
  • Group of diseases in which bone resorption outpaces bone deposition
  • Spongy bone of the spine is most vulnerable
  • Occurs most often in postmenopausal women
  • Bones become so fragile that sneezing or stepping off a curb can cause fractures
    • Treatment:
      • Calcium and vitamin D supplements
      • Increased weight-bearing exercise
      • Hormone (estrogen) replacement therapy (HRT) slows bone loss
      • Natural progesterone cream prompts new bone growth
      • Statins increase bone mineral density

Isolated Cases of Rickets

• Rickets have been essentially eliminated in the US
• Only isolated cases appear (e.g., infants of breastfeeding mothers deficient in vitamin D)

Paget's Disease

• Characterized by excessive bone formation and breakdown
• Pagetic bone with an excessively high ratio of woven (spongy) to compact bone is formed
• Pagetic bone, along with reduced mineralization, causes spotty weakening of bone
• Osteoclast activity wanes, but osteoblast activity continues to work (can get irregular bone thickenings)
• Usually localized in the spine, pelvis, femur, and skull
• Unknown cause (possibly viral)
• Treatment includes drugs Didronate and Fosamax (also calcitonin by inhalation)

Development Aspects of Bones

• Mesoderm gives rise to embryonic mesenchymal cells, which produce membranes and cartilages that form the embryonic skeleton
• The embryonic skeleton ossifies in a predictable timetable that allows fetal age to be estimated

Test your knowledge on various bone markings, textures, and the structure of long bones. This quiz covers terms like erosity, crest, trochanter, and distinguishes between compact and spongy bone. Perfect for anatomy students and enthusiasts.