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Questions and Answers
Define Wolff’s Law.
Bone grows or remodels in response to the demands placed upon it.
Which type of bone contains trabeculae?
Spongy bone
In which zone of the epiphysis do cells enlarge or get bigger?
Hypertrophic Zone
Which type of incomplete fracture is characterized by the bone flexing causing only one side of the shaft to fracture?
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During which stage of fracture repair do fibroblasts secrete collagen to span the break while osteoblasts lay down a soft bony matrix?
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Define Wolff’s Law.
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Which type of bone contains trabeculae?
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In which zone of the epiphysis do cells enlarge or get bigger?
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Which type of incomplete fracture is characterized by the bone flexing causing only one side of the shaft to fracture?
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During which stage of fracture repair do fibroblasts secrete collagen to span the break while osteoblasts lay down a soft bony matrix?
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What is commonly referred to as a Boxer’s or Barroom Fracture?
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Which feature of the femur serves as a site for muscle attachment?
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How many bones make up the human tarsal region of the foot?
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What distinguishes the true pelvis from the false pelvis?
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Which bone features a tuberosity that serves as an attachment point for the patellar tendon?
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Which of the following bones is non-weight bearing?
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Which gender tends to have a wider and rounder pelvis due to childbearing purposes?
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Which structure is not part of the appendicular skeleton?
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What is the primary function of the patella?
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Which of the following parts of the tibia is known to demarcate the medial border of the ankle joint?
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What is the primary function of the axial skeleton?
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Which of the following accurately describes the hyoid bone?
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How many total bones make up the adult human skull?
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What is the primary role of the paranasal sinuses?
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Which of the following bones is NOT part of the orbital bones?
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Which component does NOT form part of the vertebral column?
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What is the function of the ligaments in the skeletal system?
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Which of the following cranial bones houses the brain?
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What distinguishes infant skulls from adult skulls?
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Which part of the intervertebral disc helps to limit nuclear expansion under compression?
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What type of spinal curvature is characterized as being convex posteriorly?
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Which vertebra is known for having no body or spinous process?
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What is the primary function of the ribs and their cartilages in the thoracic cage?
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Which region of the vertebral column experiences the greatest amount of stress?
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What type of vertebrae articulate with the ribs?
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Which fused vertebrae form the sacrum?
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Which type of ribs are known as 'true ribs'?
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What structure allows for the passage of the spinal cord?
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What is the primary role of the cervical spine curvature?
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Which type of curvature is characterized as being concave posteriorly?
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What is the role of the anulus fibrosus in intervertebral discs?
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Which vertebra is distinguished by the presence of a knob-like projection known as the dens?
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How many thoracic vertebrae articulate with the ribs?
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Which structure of the vertebral anatomy acts as a passage for spinal nerves to exit?
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What is the primary function of the thoracic cage?
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Which type of spinal curvature is commonly associated with excessive outward curvature and is referred to as hyperkyphosis?
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What happens when the anulus fibrosus tears?
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Which feature of the lumbar vertebrae aids in bearing weight?
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What classification is given to the vertebrae that comprise the sacrum?
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What is the primary function of the axial skeleton?
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Which of the following pairs correctly match cranial bones with their features?
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What characteristic distinguishes infant skulls from adult skulls?
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Which cranial bone is also considered part of the facial structure?
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Which structure provides a passage for the spinal cord and protects it within the vertebral column?
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What role do paranasal sinuses play in relation to the skull?
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Which bone does NOT articulate directly with any other bone in the skull?
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What is the total number of cranial bones in the adult human skull?
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Which term describes the unique structure that separates the right and left parietal bones in the skull?
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What is a significant function of ligaments in the skeletal system?
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What function do the intervertebral discs serve in the spine?
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Which structure primarily distinguishes the pelvic girdle from the pectoral girdle?
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What role does the thoracic cage play in the chest region?
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Which part of the humerus is most frequently fractured during an accident?
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What is the main function of the shoulder joint's shallow socket?
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What is the significance of the acetabulum in the pelvic girdle?
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Which condition is caused by inflammation compressing the median nerve at the wrist?
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What distinguishes the radius from the ulna in the forearm?
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What kind of movement do the shapes of the radius and ulna allow?
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Which of the following does not contribute to the structure of the shoulder girdle?
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Which bone is primarily responsible for weight transmission from the femur to the foot?
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What characteristic distinguishes the female pelvis from the male pelvis?
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Which of the following is NOT a feature of the femur?
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What is the primary role of the patella?
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Which part of the pelvic girdle articulates with the sacrum?
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Which feature of the tibia is known to demarcate the medial border of the ankle joint?
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What term is used to refer to the 5 metacarpals in the hand?
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What is the risk associated with prolonged untreated shin splints?
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What is the arrangement of the digits in the hands regarding the number of phalanges?
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Which bone in the leg serves no weight-bearing function?
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Study Notes
Chemical Makeup of Bone
- Bone is made up of both organic and inorganic materials.
- Organic materials include osteoprogenitor cells, osteoblasts, osteocytes, osteoclasts, and osteoids.
- Inorganic materials consist mainly of mineral salts, specifically calcium phosphate, which account for 65% of bone mass.
- These mineral salts provide hardness and resistance to compression, making bone as strong as steel against tension and half as strong as steel against compression.
Function of Bones
- Bones provide support for the body and soft organs.
- Bones protect the central nervous system and vital organs.
- Muscles attach to bones, enabling movement through joint articulations and muscle origin/insertions.
- Bones store minerals, primarily calcium and phosphorus.
- Bones facilitate blood cell formation (both red and white) within bone marrow.
- Bones store triglycerides, which are used for energy.
Bone Classifications
- The human skeleton contains 206 named bones.
- Bones can be classified based on location:
- Axial Skeleton: includes bones along the "long axis" of the body, such as the skull, vertebral column, and rib cage.
- Appendicular Skeleton: includes bones of the upper and lower limbs, which are connected to the axial skeleton by girdles.
- Bones can also be classified based on shape:
- Long Bones: longer than they are wide, such as limb bones (femur and humerus).
- Short Bones: cube-shaped, such as bones of the wrist and ankle.
- Sesamoid bones, like the patella, form within tendons.
- Flat Bones: thin, flat, and slightly curved, such as the sternum, scapulae, ribs, and cranial bones.
- Irregular Bones: have complicated or "weird" shapes, such as the vertebrae.
Bone Structure
- Compact Bone:
- The dense, outer layer of all bones.
- Appears smooth and solid.
- Composed of osteons, which are elongated cylinders running parallel to the bone axis that serve as "weight-bearing pillars."
- Osteons are made of collagenous lamellae rings.
- Contains canals and canaliculi for vessels and nerves.
- The central (Haversian) canal is the core of the osteon.
- Perforating (Volkmann's) canals run perpendicular to the central canal.
- Spongy Bone:
- Has a "honeycomb" structure with flat pieces of bone (trabeculae).
- The spaces between trabeculae are filled with marrow.
- Acts like cables on a suspension bridge, resisting stress.
- Short, irregular, and flat bones:
- Have thin plates of spongy bone covered by compact bone.
- Compact bone is sandwiched between the periosteum (outer covering) and endosteum (inner covering).
- They do not have a defined marrow cavity.
- Long Bones:
- Have a diaphysis (shaft) along the axis of the bone.
- Compact bone surrounds a medullary cavity filled with marrow.
- Yellow marrow found here can convert to red marrow.
- Red marrow is found in infants and in the head of the femur and humerus in adults.
- Compact bone surrounds a medullary cavity filled with marrow.
- Have epiphyses (ends of long bones).
- Separated from the diaphysis by the epiphyseal line.
- Ossified epiphyseal plate (growth plate) allows for bone growth.
- Contain compact bone exterior, and spongy bone interior.
- Red marrow is found in infants and in trabecular cavities in the head of the femur and humerus in adults.
- Have articular cartilage at the ends, covering joint surfaces.
- Have a diaphysis (shaft) along the axis of the bone.
Bone Membranes
- Long bones have two membranes:
- Periosteum: double-layered membrane covering the external surface, which serves as an anchor for tendons and ligaments.
- Endosteum: delicate, internal membrane that covers trabeculae of spongy bone.
Bone Markings
- External surfaces of bones have features that serve as sites of muscle, ligament, and tendon attachment, areas involved in joint formation, or conduits for blood vessels and nerves.
- Three types of markings:
- Projections: outward bulges, often due to increased stress from muscle or joint modifications.
- Depressions: bowl-like cut-outs that act as passages for vessels and nerves, and may play a role in joint formation.
- Openings: holes or canals that serve as passages for vessels and nerves.
Bone Cells
- Osteogenic (Osteoprogenitor) Cells: mitotically active stem cells found in periosteum and endosteum.
- They differentiate into osteoblasts or bone-lining cells.
- Osteoblasts: bone-forming cells that secrete unmineralized bone matrix called osteoid.
- Osteoid is made of collagen (90%) and calcium-binding proteins, which contribute to bone's tensile strength.
- They are actively mitotic.
- Osteocytes: mature bone cells that no longer divide and maintain the bony matrix.
- They respond to mechanical stimuli (force/weight) and communicate information to osteoblasts and osteoclasts.
- Osteoclasts: bone resorption cells that break down bone.
- They secrete enzymes and protons (H+) to break down the matrix, converting calcium salts to soluble forms.
- They phagocytize demineralized matrix and dead osteocytes, transferring the products to the bloodstream.
Bone Development
- The skeleton starts out as cartilage.
- Ossification: process of bone tissue formation where cartilage is replaced by bone, except where flexibility is required.
- Endochondral Ossification: bone replaces hyaline cartilage.
- Begins at the primary ossification center (center of the shaft).
- Bone grows "outward."
- Forms all bones inferior to the skull (excluding the clavicle).
Long Bone Growth
- Long bones grow lengthwise through interstitial (longitudinal) growth of the epiphyseal plate.
- Bones increase thickness through appositional growth.
- Bone growth stops during adolescence (~18 years for females, ~21 years for males).
- Chondroblasts divide less often.
- The epiphyseal plate thins and is replaced by bone.
- Epiphyseal plate closure: epiphysis and diaphysis fuse.
- Some facial bones continue to grow throughout life.
Epiphyseal Zones
- Resting (Quiescent) Zone: inactive cells.
- Proliferation (Growth) Zone: rapidly dividing cells.
- Hypertrophic Zone: cells enlarge.
- Calcification Zone: cells die and calcify.
- Ossification (Osteogenic) Zone: osteoblasts lay down new bone.
Bone Remodeling
- A continuous process involving bone resorption and deposition.
- Resorption: breakdown of bone by osteoclasts.
- Osteoclasts secrete enzymes and protons (H+) to break down the matrix, converting calcium salts to soluble forms.
- They phagocytize demineralized matrix and dead osteocytes, transferring the products to the bloodstream.
- Deposition: laying down new bone by osteoblasts.
- Resorption: breakdown of bone by osteoclasts.
Wolff’s Law
- The trigger for remodeling is unknown but may be related to Wolff's Law.
- "Bone grows and remodels in response to the demands placed upon it.”
- Bone anatomy reflects the stresses it endures.
- Importance of weight-bearing exercises.
- Explains differences due to:
- Handedness: dominant side has thicker, stronger bone.
- Larger projections are found where heavy, active muscles attach.
- Example: compare humerus to femur, weightlifters vs non-weightlifters, fetal bones have no features due to lack of stress on bone.
Fractures
- Breaks in bone due to trauma or weakening in bone, classified based on:
- Position of bone ends after fracture:
- Nondisplaced: ends in normal positions.
- Displaced: ends out of normal alignment.
- Completeness of break:
- Complete: broken all the way through.
- Incomplete: not broken all the way through.
- Skin penetration:
- Open (compound): broken bone penetrates the skin.
- Closed (simple): broken bone does not penetrate the skin.
- Position of bone ends after fracture:
Fracture Repair
- A four-stage process:
- Hematoma (first few days): Torn blood vessels hemorrhage, forming a blood clot (hematoma).
- Site is swollen, painful, and inflamed.
- Fibrocartilaginous (Soft) Callus (2-3 weeks): Fibroblasts secrete collagen spanning the break, connecting broken ends.
- Bone reconstruction begins with cartilage matrix formation to repair the tissue.
- Osteoblasts form spongy bone within the matrix.
- Bony (Hard) Callus (4-16 weeks): Soft callus is converted to a hard callus of spongy bone.
- Continues ~2 months until a firm union forms.
- Bone Remodeling (6-12 months): Excess material in the diaphysis exterior and medullary cavity is removed.
- Compact bone is laid down to reconstruct the shaft walls.
- Hematoma (first few days): Torn blood vessels hemorrhage, forming a blood clot (hematoma).
Osteomalacia and Osteoporosis
- Osteomalacia: bone softening in adults.
- Rickets in children.
- Caused by vitamin D and/or calcium deficiency.
- Causes pain on weight bearing.
- Leads to bowed legs and other deformities in children.
- Osteoporosis: bone resorption outpaces bone deposition.
- Bone matrix is normal, but bone mass declines.
- Most common in vertebrae and femur.
- Postmenopausal women are at the greatest risk.
- Men are largely protected by the effects of testosterone.
Skeletal Tissue Summary
- Bones are essentially hardened cartilage that grows and hardens based on stress (Wolff’s Law).
- As we grow, osteogenic cells become osteoblasts, which lay down a matrix that grows and ossifies either interstitially or appositionally.
- Bones are classified by structure: long, short, flat, irregular.
- Compact bone exteriors with spongy bone middles filled with trabeculae.
- Bone remodeling involves osteoclasts resorbing damaged bone and stimulating osteoblasts to begin the process.
- Osteoporosis occurs when resorption exceeds deposition.
- Fractures occur when bone fails (breaks) due to excessive stress.
- Fractures are classified based on the type of damage.
- Fracture repair is a multi-stage process that can take up to 12 months to complete.
Chemical Makeup of Bone
- Bones are composed of organic and inorganic materials.
- Organic components include osteoprogenitors, osteoblasts, osteocytes, osteoclasts, and osteoids.
- Inorganic components are mainly mineral salts, primarily calcium phosphate, making up 65% of bone mass.
- Mineral salts provide hardness and resistance to compression, making bone stronger than steel in resisting compression and as strong as steel in resisting tension.
Function of Bones
- Provide support for the body and soft organs.
- Protect the central nervous system and vital organs.
- Facilitate movement through joint articulations and muscle attachments.
- Store minerals such as calcium and phosphorus.
- Produce blood cells (red and white) in the bone marrow.
- Store triglycerides for energy.
Bone Classifications
- The human skeleton consists of 206 named bones.
- Bones are divided into two groups based on location: axial and appendicular.
- Axial skeleton includes bones along the "long axis" of the body, such as the skull, vertebral column, and rib cage.
- Appendicular skeleton includes bones of the upper and lower limbs, connected to the axial skeleton by girdles.
- Bones are classified based on their shape:
Bone Shapes
- Long Bones: Longer than they are wide, such as limb bones (femur and humerus).
- Short Bones: Cube-shaped, such as bones of the wrist and ankle.
- Flat Bones: Thin, flat, and slightly curved, such as the sternum, scapulae, ribs, and cranial bones.
- Irregular Bones: Complicated or "weird" shapes, such as vertebrae.
Bone Structure
- Compact Bone: Dense, outer layer of all bones, appearing smooth and solid. It consists of osteons, elongated cylinders aligned with the bone's axis acting as weight-bearing pillars.
- Spongy Bone: "Honeycomb" structure of flat pieces of bone (trabeculae) filled with marrow. Provides strength by acting as cables on a suspension bridge.
- Short, Irregular, and Flat Bones: Composed of thin plates of spongy bone covered by compact bone, with compact bone sandwiched between the periosteum and endosteum.
- Long Bones: Have a diaphysis (shaft) with a medullary cavity containing marrow (yellow in adults, red in infants), and epiphyses (ends) separated from the diaphysis by the epiphyseal line.
Bone Membranes
- Periosteum: Double-layered membrane covering the external surface of bones except for joint surfaces, anchoring tendons and ligaments.
- Endosteum: Delicate, internal membrane lining the trabeculae of spongy bone.
Bone Markings
- Indicate points of muscle, ligament, and tendon attachment, areas for joint formation, and passages for blood vessels and nerves.
- Three types:
- Projections: Outward bulges for muscle attachments or joint modifications.
- Depressions: Bowl-like cut-outs for vessel and nerve passage or joint formation.
- Openings: Holes or canals for vessel and nerve passage.
Bone Cells
- Osteogenic cells: Mitotically active stem cells that differentiate into osteoblasts or bone-lining cells found in periosteum and endosteum.
- Osteoblasts: Bone-forming cells that secrete unmineralized bone matrix called osteoid, contributing to bone's tensile strength.
- Osteocytes: Mature bone cells, no longer dividing, that maintain the bony matrix, communicate with other bone cells, and respond to mechanical stimuli.
- Osteoclasts: Bone-resorbing cells that break down bone tissue to release calcium and other minerals.
Bone Development
- Ossification is the process of bone tissue formation, replacing cartilage except where flexibility is needed.
- Endochondral Ossification: Bone replaces hyaline cartilage, starting at the primary ossification center in the shaft and expanding outwards. This process forms all bones inferior to the skull (except for the clavicle).
Long Bone Growth
- Interstitial Growth: Lengthwise growth occurs within the epiphyseal plate through cartilage cell division and subsequent ossification.
- Appositional Growth: Increase in bone thickness occurs through the deposition of new bone tissue on the external surface of the bone.
- Bone growth stops during adolescence, with the epiphyseal plate closure marking the fusion of epiphysis and diaphysis.
Epiphyseal Zones
- Resting Zone: Inactive cells.
- Proliferation Zone: Rapidly dividing cells.
- Hypertrophic Zone: Cells enlarge.
- Calcification Zone: Cells die and calcify.
- Ossification Zone: Osteoblasts lay down new bone.
Bone Remodeling
- Resorption: Breakdown of bone tissue by osteoclasts, which secrete enzymes and protons to dissolve the bone matrix.
- Deposition: Laying down new bone tissue by osteoblasts.
Wolff’s Law
- States that bones grow and remodel in response to the demands placed upon them.
- Bone anatomy reflects the stress it endures.
- Explains differences in bone density based on activity and weight-bearing exercises.
Fractures
- Breaks in bone caused by trauma or weakened bone.
- Position of Bone Ends: Nondisplaced (ends in normal positions) or displaced (ends out of alignment).
- Completeness of Break: Complete (broken all the way through) or incomplete (not fully broken).
- Skin Penetration: Open (compound, skin broken) or closed (simple, skin intact).
Fracture Repair
- Hematoma Formation: Torn blood vessels form a blood clot at the fracture site (hematoma).
- Fibrocartilaginous Callus: Fibroblasts secrete collagen and chondroblasts form cartilage matrix, bridging the broken ends.
- Bony Callus: The soft callus is replaced by a hard callus of spongy bone.
- Bone Remodeling: Excess bone material is removed, and compact bone is laid down to reconstruct the shaft walls.
Osteomalacia & Osteoporosis
- Osteomalacia: Softening of bones in adults (rickets in children) due to vitamin D and/or calcium deficiency.
- Osteoporosis: Bone resorption exceeds bone deposition, resulting in reduced bone mass. Most common in vertebrae and femur.
Skeletal Tissue Summary
- Bones are hardened cartilage, formed through the process of ossification.
- Ossification begins with osteogenic cells differentiating into osteoblasts, which lay down a bone matrix that grows interstitially and appositionally.
- Bones are classified by their structure and shape.
- Bone growth and remodeling are influenced by Wolff's Law.
- Osteoporosis occurs when resorption exceeds deposition.
- Fractures can be classified based on the degree of damage, and repair occurs in distinct stages.
The Appendicular Skeleton
- Refers to bones of the limbs or extremities
- Begins at the shoulder and pelvic girdles
- Extends down to hands and feet
- The study of these bones is important for understanding:
- Fracture locations
- Muscle actions
- How body weight and impact forces are dealt with
- Joint formations
Spinal Curvatures
- The spine has multiple curves that are not just for looks
- There are two types of curvatures:
- Lordotic:
- Concave posteriorly
- Example: Cervical & Lumbar spines
- Hyperlordosis (swayback) = Accentuation of the lumbar curve
- Kyphotic:
- Convex posteriorly
- Example: Thoracic & Sacral spine
- Hyperkyphosis (hunchback) = Accentuation of the thoracic curve
- Lordotic:
- Curves help the spine deal with head and body loads
- Scoliosis is an abnormal lateral rotation in the spine
Intervertebral Discs
- Cushion-like disks between each vertebra serve as:
- Shock absorbers
- Provide free movement
- The disk has two parts:
- Nucleus pulposus:
- Inner gelatinous nucleus
- Provides elasticity and compressibility
- Anulus fibrosis:
- Outer ring of collagen and fibrocartilage
- Limits nuclear expansion under compression
- If this ring tears, the nucleus can protrude out leading to a herniated/prolapsed disk
- This can compress nerves causing pain, numbness, and weakness
- Typically caused by actions involving simultaneous compression and rotation
- Nucleus pulposus:
Vertebral Structure
- The structure of a vertebrae is similar across cervical, thoracic, and lumbar regions
- All vertebrae share the following features:
- Body:
- Anterior, weight-bearing portion
- Where the intervertebral disc sits
- Vertebral arch:
- Posterior portion that projects many processes
- Pedicles: Short pillars forming the sides of the arch
- Laminae: Fused, flat plates making the posterior arch
- Vertebral foramen: Opening that allows the spinal cord to pass through
- Intervertebral foramina: Lateral openings between the vertebrae that allow spinal nerves to exit
- Processes: Project off the arch
- Spinous process: Projects posteriorly (can be palpated)
- Transverse processes: Project laterally
- Superior articular processes: Protrude superiorly
- Inferior articular processes: Protrude inferiorly
- Body:
Cervical Vertebrae
- C1-C7: Smallest and lightest vertebrae
- Oval-shaped bodies
- Large vertebral foramen
- C1 (atlas) and C2 (axis) are unique:
- Atlas has no body or spinous process, but has an anterior and posterior arch
- Axis: Has a knob-like dens (tooth-like projection) that extends posteriorly into the anterior arch of the atlas.
- The atlas and axis together allow for head movement
- C7/T1 Processes can be felt through the skin and are used as landmarks
- Vertebra prominens
- C3 fracture is referred to as a "hangman's fracture"
- This type of fracture was thought to be caused by the force of a noose and drop
- It can cut off communication to the diaphragm, stopping breathing
Thoracic Vertebrae
- T1 – T12 vertebrae progressively increase in size
- Articulate with ribs
- Via transverse costal facets on the transverse processes
- Have long, sharp spinous processes that point inferiorly
- Have heart-shaped bodies
- Have circular vertebral foramens
Lumbar Vertebrae
- L1 - L5 are the largest vertebrae
- Receive the greatest amount of stress
- "Small of the back"
- Have flat, spatulated spinous processes
- Triangular vertebral foramen
- Short, thick pedicles and laminae
Sacrum & Coccyx
- Sacrum: Triangular bone shaping the posterior wall of the pelvis
- Composed of five fused vertebrae
- Articulates with L5 superiorly, and the coccyx inferiorly
- Lateral articulations with the pelvic ileum bones form the sacroiliac (SI) joints
- Coccyx: 3 - 5 fused vertebrae
- Also known as the "tailbone"
- Has very little function
- Often fractured due to falls
Thoracic Cage
- Composed of T1 - T12 Vertebrae (posteriorly), sternum & costal cartilages (anteriorly) & 12 rib pairs (laterally)
- Sternum: Articulates inferiorly with the xiphoid process
- A blow to the sternum can push the xiphoid process into the liver or heart, causing massive hemorrhaging
- Sternal manubrium has jugular notches
- CPR is performed by compressing at the mid-sternum
- Costal cartilages allow rib articulation with the sternum:
- Ribs 1-7: True ribs that directly attach to the sternum
- Ribs 8-10: False ribs that attach to the sternum via costal cartilage
- Ribs 11 & 12: Floating ribs, do not attach to the sternum
Axial Skeleton Summary
- Comprised of the skull, spine, rib cage, and sternum
- The primary function is to protect the central nervous system and thoracic organs
- The bones of the skull are structured to house the brain, eyes, sinuses, etc.
The Skeleton
- Composed of bones, cartilages, joints, and ligaments
- Mostly bone
- Cartilage in isolated areas (usually joint articulations)
- Ligaments connect bones & reinforce joints
- 20% of total body mass
- 2 Major Divisions: Axial Skeleton & Appendicular Skeleton
Axial Skeleton
- 80 Bones, 3 Regions (skull, vertebral column, thoracic cage)
- 3 Functions
- Forms longitudinal axis of body to which appendages attach
- Supports head, neck, and trunk
- Protection of:
- Brain
- Spinal cord
- Thoracic organs (heart, lungs)
The Skull
- Most complex bony structure in body
- Composed of cranial and facial bones
- Cranial bones (cranium)
- Hold brain in cranial cavity
- Attachment site for head and neck muscles
- Facial Bones
- Facial framework
- Cavities for sensory organs of taste, sight, smell
- Anchor facial muscles used for speech and expression
- Cranial bones (cranium)
- Infant skulls have more bones than adults because some are still unfused
- Infant skull bones are connected by fontanelles instead of sutures
- Eases birthing process & allows brain growth
- Anterior Fontanelle = “soft spot”
- Infant skull bones are connected by fontanelles instead of sutures
Cranial & Facial Bones
- 8 Cranial bones:
- Frontal
- Parietal (R & L)
- Occipital
- Temporal (R & L)
- Sphenoid
- Ethmoid
- 14 Facial bones:
- Mandible (lower jaw)
- Maxilla (upper jaw)
- Zygomatic (R & L; cheekbones)
- Nasal (nasal bridge; R&L)
- Lacrimal (R & L; near tear ducts)
- Palatine
- Vomer (nasal septum)
- Inferior nasal conchae (R & L)
Hyoid Bone
- Not a bone of the skull
- Base for tongue & attachment point for muscles involved with speech & swallowing
- Only bone that does not directly articulate with another bone
- Anchored by ligaments to neck, inferior to mandible
Orbital Bones
- “Eye Socket”
- Fusion of 7 Craniofacial Bones:
- Frontal
- Sphenoid
- Zygomatic
- Maxilla
- Palatine
- Lacrimal
- Ethmoid
Paranasal Sinuses
- Mucus-lined, air-filled space
- Warm & humidify air
- Lighten skull
- Enhance vocal resonance
- Formed from 5 craniofacial bones:
- Frontal
- Sphenoid
- Ethmoid
- Maxillae
Vertebral Column
- AKA “spine” or “spinal column”
- Functions:
- Direct weight of truck to lower limbs
- Surrounds & protects spinal cord
- Attachment point for ribs & abdominothoracic musculature
- Made up from 26 vertebrae running from skull to pelvis
- 5 Regions (superior to inferior):
- Cervical (7 vertebrae)
- Thoracic (12 vertebrae)
- Lumbar (5 vertebrae)
- Sacral ( 5 fused vertebrae)
- Coccygeal (4 fused vertebrae)
- 5 Regions (superior to inferior):
Spinal Curvatures
- Spine has curves
- 2 Types:
- “Concave” posteriorly = Lordotic
- Secondary curvature
- Cervical & Lumbar spines
- Accentuated lumbar curve = hyperlordosis (swayback)
- “Convex” posteriorly = Kyphotic
- Primary curvature
- Thoracic and Sacral spine
- Accentuated thoracic curve = hyperkyphosis (hunchback)
- “Concave” posteriorly = Lordotic
- Help to effectively deal with loads of head and body
- Scoliosis: abnormal lateral rotation (or curve) in spine
Intervertebral Discs
- Between each vertebra are discs
- Cushion-like shock absorbing pads
- Also provides some freedom for movement
- Cushion-like shock absorbing pads
- 2 Parts:
- Nucleus pulposus
- Inner gelatinous nucleus
- Elasticity & compressibility
- Anulus fibrosus
- Outer ring of collagen & fibrocartilage
- Limits nuclear expansion under compression
- If these tear, nucleus will protrude out
- Herniated (prolapsed) disc
- Compress nerves causing pain, numbness, weakness
- Usually caused by actions involving simultaneous compression & rotation
- Nucleus pulposus
Vertebral Structure
- C-, T-, & L-vertebra are similar but share a common structural pattern
- Body: anterior, weight-bearing portion
- Intervertebral discs sit here between vertebrae
- Vertebral Arch: posterior portion from which processes protrude
- Pedicles: short pillars forming arch sides
- Laminae: fused, flat plates making posterior arch
- Vertebral Foramen: opening allowing spinal cord passage
- Intervertebral Foramina: lateral openings between vertebrae allowing spinal nerves to exit
- Processes: protrude off arch
- Spinous process: projects posteriorly
- Can palpate on someone
- Transverse processes: project laterally
- Superior articular processes: protrude superiorly
- Inferior articular processes: protrude inferiorly
- Spinous process: projects posteriorly
- Body: anterior, weight-bearing portion
Cervical Vertebrae
- C1 – C7 lightest, smallest vertebrae
- Oval-shaped bodies; Large vertebral foramens
- C1 (Atlas) & C2 (Axis) are unique
- Atlas has no body or spinous process but anterior & posterior arches with two lateral masses
- Axis has a knob-liked dens projecting posteriorly into anterior arch of Atlas
- “Pivot point” for rotation
- Together allow for head movement
- C7/T1 processes can be felt through the skin and are used as landmarks
- Vertebra prominens
- C3 fracture also referred to as “hangman’s fracture”
- Cut off communication to diaphragm…stop breathing
Thoracic Vertebrae
- T1 – T12 progressively increase in size
- Articulate with the ribs
- Via transverse costal facets on transverse processes
- Long, sharp spinous processes point inferiorly
- Heart-shaped bodies
- Circular vertebral foramens
Lumbar Vertebrae
- L1 – L5 largest vertebrae
- Receives greatest amount of stress
- “Small of the back”
- Flat, spatulated spinous process
- Triangular vertebral foramen
- Short, thick pedicles & laminae
Sacrum & Coccyx
- Sacrum: triangular bone shaping posterior wall of pelvis
- 5 fused vertebrae
- Articulates superiorly with L5, inferiorly with coccyx
- Lateral articulations with pelvic ileum bones making sacroiliac (SI) joints
- Coccyx: 3 – 5 fused vertebrae
- aka “tailbone”
- Little function
- Often fractured through falls
Thoracic Cage
- T1 – T12 (posteriorly)
- Sternum & costal cartilages (anteriorly)
- Sternal body articulates with xiphoid process inferiorly
- Blow to chest can push xiphoid process into liver or heart = massive hemorrhaging
- Sternal manubrium has jugular notches
- CPR performed by compressing at mid-sternum
- Costal cartilages allow rib articulation with sternum
- Sternal body articulates with xiphoid process inferiorly
- 12 Rib pairs (laterally)
- 1st ten ribs articulate with sternum
- Rib pairs 1 – 7 = true ribs attaching to sternum directly
- Rib pairs 8 – 10 = false ribs attaching to sternum via costal cartilage
- Rib pairs 11 & 12 = floating ribs; no sternal attachment
- 1st ten ribs articulate with sternum
Axial Skeleton Summary
- Comprised of skull, spine, rib cage, and sternum
- Major Job is to protect the central nervous system & thoracic organs
- Bones of skull are structured to house brain, eyes, sinuses, etc. Fused together by sutures.
- Spinal column has 5 segments:
- 7 cervical vertebrae
- 12 thoracic vertebrae
- 5 lumbar vertebrae
- 5 (fused) sacral vertebrae
- 3 – 5 (fused) coccygeal vertebrae
- Spine has discs between vertebrae to provide cushion & support for weight bearing and freedom of movement.
- Spine’s curvature (kyphotic & lordotic) also aid weight bearing.
- Rib cage and sternum encase lateral and anterior aspects of thoracic cavity.
Appendicular Skeleton
- Bones of the limbs and their girdles
- Pectoral Girdle: attaches upper limbs to trunk
- Aka shoulder girdle
- Clavicles (anteriorly) ; scapulae (posteriorly)
- Attachment site for muscles moving upper limbs
- High degree of mobility
- Scapulae not attached to axial skeleton
- Shoulder joint socket is shallow = ↑ movement freedom
- Pelvic Girdle: attaches lower limbs to trunk
- Aka hip girdle
- 2 hip or coxal bones and sacrum
- 1 Coxal bone = fused ilium, ischium, pubis
- Transmit weight of upper body onto lower limbs, supports pelvic organs
- Attachment point for muscles moving lower limbs & stabilization
- Less mobile but more stable than shoulder girdle
- Pectoral Girdle: attaches upper limbs to trunk
Bones of the Pectoral Girdle
- Clavicles aka “collarbones”
- Sternal ends articulate medially with clavicular notches on manubrium of sternum
- Acromial ends articulate laterally acromion processes of scapular spines
- Articulation makes the acromioclavicular (A-C) joint
- Blunt trauma can damage joint creating a “separated shoulder”
- Articulation makes the acromioclavicular (A-C) joint
- Scapulae
- Located on dorsal surface of rib cage
- 3 borders (superior, medial, lateral)
- 3 major features
- Spine: prominent, posterior ridge
- Acromion: lateral projection stemming off spine & articulating with lateral clavicle
- Coracoid process: anterior projection which anchors biceps muscle
Humerus (Upper Arm)
- Articulates with glenoid cavity of scapula (proximally) & radius and ulna (distally)
- 5 Major Features:
- Head: proximal end articulating with glenoid cavity
- Tubercles: greater and lesser; attachment sites for rotator cuff muscles
- Intertubercular (bicipital) sulcus runs between guiding biceps tendon
- Surgical Neck: most frequently fractured
- Deltoid Tuberosity: site of deltoid muscle insertion
- Midway down shaft
- Demarcates the distal “point” of the “deltoid diamond shape”
- Medial and Lateral Epicondyles: distally located protrusions
- Attachment points for forearm muscles
Forearm
- Radius: lateral bone of forearm (thumb-side)
- Head articulates with capitulum of humerus & radial arch of ulna (proximally)
- Shape and interaction with ulna allow for pronation & supination movements
- Ulnar notch articulates with ulna (distally)
- Radial styloid process anchors ligaments of “wrist”
- Colles’ Fracture: break in distal end of radius
- Common from falls with outstretched hands
- Head articulates with capitulum of humerus & radial arch of ulna (proximally)
- Ulna: medial bone of forearm (pinky-side)
- Forms major portion of elbow joint with humerus
- Olecranon & coronoid processes “hook” onto trochlea of humerus creating hinge joint
- Radial notch: articulates with head of radius (proximally)
- Ulnar head: knob-like distal portion, articulates with carpal bones
- Ulnar styloid process: anchors ligaments of “wrist”
- Nursemaid’s Elbow (Pulled Elbow): radial head subluxation (not quite dislocates)
Hand
- Carpals:
- 8 bones, 2 rows
- Proximal Row (Lateral to Medial): only ones that make “wrist” joint
- Scaphoid, Lunate, Triquetrum, Pisiform
- “Sally Left the Party…”
- Distal Row (Lateral to Medial):
- Trapezium, Trapezoid, Capitate, Hamate
- “…to Take Cindy Home”
- Proximal Row (Lateral to Medial): only ones that make “wrist” joint
- Carpal Tunnel Syndrome: median nerve gets impinged in “carpal tunnel” travelling over wrist
- Caused by overuse, inflammation compressing on nerve
- Tingling & numbness felt (esp.in digits I – IV)
- 8 bones, 2 rows
- Metacarpals:
- 5 metacarpals; labelled I to V from lateral (thumb) to medial (pinky)
- Most commonly fractured in fights/punching
- Fracture of 5th metacarpal = Boxer’s/Barroom Fracture
- Phalanges:
- Fingers (digits) labelled I to V similarly to metacarpals
- 1st digit (pollex) has two bones
- All other digits have three bones – proximal, middle, distal phalanx
- Fingers (digits) labelled I to V similarly to metacarpals
Bones of the Pelvic Girdle
- Ilium
- Superior region of coxal bone
- Auricular surface articulates with sacrum (SI joint)
- Ischium
- Posteroinferior part coxal bone
- What you sit upon
- Posteroinferior part coxal bone
- Pubis
- Anterior portion of coxal bone
- L & R pubis join at pubic symphysis
- 3 bones make up the false pelvis
- True pelvis denoted by pelvic brim (inlet)
- Female (or AFAB) pelvis tends to be wider, shallower, and rounder than Male (or AMAB) due to necessities for childbearing
Femur and Patella (Thigh)
- Femur:
- Largest & strongest bone in body
- Makes up 25% of total body height
- Articulates with acetabulum of hip (coxal) bone (proximally) & tibia and patella (distally)
- Largest & strongest bone in body
- 3 Major Features:
- Trochanters: greater and lesser
- Proximally located near femoral neck
- Muscle attachments sites
- Condyles: lateral & medial
- Distal aspects articulate with tibial plateau
- Superior half of knee joint
- Epicondyles: lateral & medial
- Protrude off lateral and medial condyles
- Muscle attachment sites
- Trochanters: greater and lesser
- Patella:
- Sesamoid bone in quadriceps tendon
- Protects knee joint
Tibia & Fibula (Leg/Shank)
- Tibia:
- Medial leg bone receiving weight from femur & transmits to foot
- Also receives impact forces from foot and transfers to femur
- Major Features:
- Condyles: medial & lateral
- Attachment point for muscles, tendons & ligaments
- Tibial tuberosity:
- Attachment point for patellar tendon anchoring patella & quadriceps muscle
- Inflammation can lead to Osgood-Schlatter’s Disease (Jumper’s Knee)
- Medial Malleolus:
- Demarcates medial border to ankle joint
- Condyles: medial & lateral
- Prolonged, untreated shin splints can cause stress fractures in the tibial shaft
- Medial leg bone receiving weight from femur & transmits to foot
- Fibula:
- Non-weight bearing
- Articulates with tibia @ proximal & distal ends
- Major Features:
- Head
- Lateral Malleolus:
- Demarcates lateral border to ankle joint
- Commonly fractured
Foot
- Tarsals:
- 7 Tarsal Bones
- Body weight & impacts predominantly carried/absorbed by talus and calcaneus (heel)
- Also include: cuboid, navicular, and medial, intermediate & lateral cuneiforms
- 7 Tarsal Bones
- Metatarsals:
- “Balls of feet”
- Labelled I to V from hallux to little toe
- Phalanges:
- Toes
- Labelled I (hallux, big toe) to V (little toe)
- Digit I (hallux) has 2 bones, like hand
- Digits II – V have 3 bones, like hand
Appendicular Skeleton Summary
- Refers to the bones of the limbs/extremities
- Beginning at the Shoulder and Pelvic girdle
- Extend down to hands and feet
- Accurate identification of these bones and their landmarks is important for:
- Identification of fracture locations
- Understanding muscle actions
- Understanding how body weight and impact forces are dealt with
- Understanding of joint formations (coming up next)
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Description
Explore the fascinating chemical structure and functions of bones in the human body. Learn about the organic and inorganic materials that contribute to bone strength and their vital roles in movement, protection, and storage. This quiz covers essential classifications and the significance of bones in anatomy.
