THE SKELETAL SYSTEM List the five functions of the skeletal system. Identify the classification system for bones and name an example of each type of bone. Identify and label the bones that make up the axial skeleton. Identify and label the bones that make up the appendicular skeleton. Analyze the types of joints and identify what type of movement each joint provides for the body. Identify symptoms and treatments of a variety of conditions and injuries of the skeletal system. Identify the different types of fractures. List the steps of fracture repair. Fact or Myth Babies have more bones than adults. FACT – Babies are born with about 300 - 350 bones. Adults have 206 bones. Fact or Myth Your funny bone is a bone in your elbow. Myth – It’s a nerve that runs down the humerus to the inside part of your Fact or Myth Bones usually stop growing at puberty. Myth – Bones usually stop growing when you’re in your late 20’s. Fact or Myth Blood cells are produced in bone. Fact – red and white blood cells are produced in the bone marrow in the center Fact or Myth The collar bone gets broken the most often. Fact – The clavicle leads the list of breaks. Fact or Myth There are 5 bones in the body not connected to other bones. Myth – There is only one bone (hyoid) that is not connected to other bones. Fact or Myth Your big toe has fewer bones than your other toes. Fact – Most toe bones have three tiny bones, but your big toe has two. You also have three bones in each of your fingers, but only two in each of your thumbs. Fact or Myth The smallest bone in your body is located in your cheek. Myth – The smallest bone is located in your ear (bone behind your eardrum called the stirrup). Fact or Myth A giraffe has the same number of bones in the neck as humans do. Fact – Giraffes and humans have 7 cervical vertebrae (neck bones). Fact or Myth Bone is 5x harder than steel. FACT! Bone is often compared to the strength of steel and concrete. The Skeletal System What’s in a bone? • Bones, Muscles, and Joints Functions of the Skeletal System 1. 2. 3. 4. 5. Structure/Framework Protection Movement Mineral storage Blood cell production CLASSIFICATION OF BONES • Bone consists of bone tissue, cartilage, dense connective tissue, blood, and nervous tissue • Bones are classified by their shape and type of bone (compact or spongy bone) • Compact bone – dense bone tissue found on the outside of the bone • Spongy bone – found on the interior of the bone which is filled with marrow (in some bones) Long bones Bones are identified by: • • • • • • Long longitudinal axes Expanded ends Hard outer surface of compact bone Spongy inner bone containing bone marrow Arm and leg bones Hands, feet, and fingers Parts of a long bone: Diaphysis (shaft of bone): – Covered by periosteum (covering of dense connective tissue) Epiphysis (ends): – Articulate with other bones – Covered by Articular cartilage Metaphysis: – Location where diaphysis and epiphysis meet Flat Bones • Plate like, strong structures that provide protection • Compact bone and spongy bone • Varying amounts of bone marrow • Ribs, bones of the skull, scapulae Short Bones • • • • Cube like; equal lengths and widths Wrists and ankle bones Provide support with little movement Thin layer of compact bone, spongy bone and bone marrow on the inside Sesamoid Bones (Short) • Small bone embedded in a tendon • Patella, bones of the foot and hand Irregular Bones • • • Variety of shapes (non – uniform shape) Consist mostly of spongy bone Vertebrae, facial bones Check Point 1. Approximately how many bones are there in the human body? 2. What are the four bone classifications? 3. What are the five functions of the skeletal system? 4. What type of cartilage makes up the embryonic skeleton? BONE MARKINGS (Surface Features) • Each bone in the body has characteristic external and internal features. • Every bump, groove, and hole has a name on your bones. • Detailed examination can yield an abundance of anatomical information. Bone Markings • Two types of bone markings: – Projections (aka processes) that grow out from the bone – Depressions (cavities) that indent the bone The Axial Skeleton • Includes 80 bones • 40% of the bones in the human body Axial Skeleton • Three Regions: 1. Skull (8 cranial & 14 facial) ** bones associated with skull (6 auditory ossicles and hyoid) 2. Vertebral column (24 vertebrae, the sacrum & coccyx) 3. Thoracic cage (sternum & 24 ribs) The Skull • The bones of the skull protect the brain and guard the entrances to the digestive & respiratory systems • The skull (22 bones), the body’s most complex bony structure, is formed by the cranium (8 bones) and facial bones (14 bones) • 6 auditory ossicles (tiny bones) are situated within the temporal bones of the cranium (smallest bones in the body that are contained in the middle ear space; hammer, anvil, stirrup) • Hyoid bone (connected to the inferior surfaces of the temporal bones) The Skull • Cranium – protects the brain and is the site of attachment for head and neck muscles • Facial bones – Supply the framework of the face, the sense organs, and the teeth – Provide openings for the passage of air and food – Anchor the facial muscles of expression Anatomy of the Cranium Eight cranial bones: 1. 2. 3. 4. 5. 6. • • 2 parietal 2 temporal Frontal Occipital Sphenoid Ethmoid The cranial bones enclose the cranial cavity, a fluid-filled chamber that cushions and supports the brain Cranial bones are thin and remarkably strong for their weight Skull – Anterior View Figure 7.2a Frontal Bone • Forms the anterior portion of the cranium & the roof of the orbits (eye sockets) Parietal Bones • Forms most of the superior and lateral aspects of the skull Figure 7.3a Occipital Bone • Located at the back and lower part of the cranium Temporal Bones Form part of both the lateral walls of the cranium Figure 7.5 Parietal Bones & Major Associated Sutures • Four sutures mark the articulations of the parietal bones 1. Coronal suture – articulation between parietal bones and frontal bone anteriorly 2. Sagittal suture – where right and left parietal bones meet superiorly Parietal Bones & Major Associated Sutures 3. Lambdoid suture – where parietal bones meet the occipital bone (posterior) 4. Squamosal or squamous suture – where parietal and temporal bones meet Sphenoid Bone • Butterfly-shaped bone that forms part of the floor of the cranium, unites the cranial and facial bones, and acts as a cross brace that strengthens the sides of the skull • Forms the central wedge that articulates with all other cranial bones Ethmoid Bone • Most deep of the skull bones; lies between the sphenoid and nasal bones Figure 7.7 Facial Bones • Fourteen bones of which only the mandible and vomer are unpaired • The paired bones are the maxillae, zygomatics, nasals, lacrimals, palatines, and inferior conchae Mandible • The mandible (lower jawbone) is the strongest bone of the face Figure 7.8a Maxillary Bones • Medially fused bones that make up the upper jaw and the central portion of the facial skeleton (largest facial bones) Figure 7.8b Zygomatic Bones • Irregularly shaped bones (cheekbones) that form the prominences of the cheeks and the inferolateral margins of the orbits Other Facial Bones • Nasal bones – thin medially fused bones that form the bridge of the nose • Lacrimal bones – contribute to the medial walls of the orbit and contain a deep groove that house the tear ducts Facial Bones • Palatine bones – two bone plates that form portions of the hard palate and contribute to the floor of each orbit Other Facial Bones • Vomer – forms part of the nasal septum • Inferior nasal conchae – paired, curved bones in the nasal cavity that form part of the lateral walls of the nasal cavity Hyoid Bone • Lies just inferior to the mandible in the anterior neck • Only bone of the body that does not articulate directly with another bone • Attachment point for neck muscles that raise and lower the larynx during swallowing and speech Figure 7.12 Vertebral Column • 26 irregular bones (vertebrae) • Provide a column of support, bearing the weight of the head, neck, and trunk. • Transfers weight to the appendicular skeleton of the lower limbs • Protects spinal cord • Helps maintain an upright body position • Approx. length of an adult column is 71cm Vertebral Column Cervical vertebrae 7 bones of the neck Thoracic vertebrae 12 bones of the torso Lumbar vertebrae 5 bones of the lower back Sacrum - 5 fused vertebrae Coccyx – 4 fused vertebrae Figure 7.13 Disks are small shock absorbers between the vertebrae (gel-like interior) General Structure of Vertebrae: 1. Vertebral body (centrum) – disc-shaped, weight-bearing region 2. Vertebral arch – composed of pedicles (walls) and flat layers called laminae (roof) ** forms the posterior margin of each vertebral foramen (together they form the vertebral canal which encloses the spinal cord) 3. Articular processes– projections on each vertebra Cervical Vertebrae • Most mammals have 7 cervical vertebrae (giraffes, whales, mice & humans) • Seven vertebrae (C1-C7) are the smallest, lightest vertebrae Cervical Vertebrae: The Atlas (C1) – Holds up the head – The superior surface articulates with the occipital condyles of the skull (permits you to nod) »Has no body and no spinous process Cervical Vertebrae: The Axis (C2) • The axis has a body, spine, and vertebral arches as do other cervical vertebrae • Articulates with the atlas to permit rotation Figure 7.16c Thoracic Vertebrae • There are twelve vertebrae (T1-T12) • Distinctive heart-shaped body (more massive than that of a cervical vertebra) • Each thoracic vertebra articulate with ribs Lumbar Vertebrae • The five lumbar vertebrae (L1-L5) are located in the small of the back and have an enhanced weight-bearing function • Largest vertebrae Tip: Mealtimes Breakfast: 7 a.m. (7 cervical) Lunch: 12 p.m. (12 thoracic) Dinner: 5 p.m. (5 lumbar) Table 7.2 Sacrum • The sacrum – Consists of five fused vertebrae (S1-S5), which shape the posterior wall of the pelvis – Begin fusing after puberty and are completely fused at age 25-30 – Protects reproductive, digestive, and urinary organs – It articulates with L5 superiorly, and with the auricular surfaces of the hip bones Coccyx • Coccyx (Tailbone) – The coccyx is made up of four (in some cases three to five) fused vertebrae that articulate superiorly with the sacrum – Generally begun fusing by age 26 Bony Thorax (Thoracic Cage) Functions: – Forms a protective cage around the heart, lungs, and great blood vessels – Supports the shoulder girdles and upper limbs – Provides attachment for many neck, back, chest, and shoulder muscles Sternum (Breastbone) • A dagger-shaped, flat bone that lies in the anterior midline of the thorax • Fusion is not complete until at least age 25 (until this age the sternal body consist of four separate bones) Ribs • There are twelve pair of ribs • All ribs attach posteriorly to the thoracic vertebrae • The superior 7 pair (true, or vertebrosternal ribs) attach directly to the sternum via costal cartilages • Ribs 8-10 (false, or vertebrocondral ribs) attach indirectly to the sternum via costal cartilage • Ribs 11-12 (floating, or vertebral ribs) have no anterior attachment Ribs Figure 7.19a Appendicular Skeleton • The appendicular skeleton is made up of the bones of the limbs and their supporting elements (girdles) that connect them to the trunk • Pectoral (shoulder) girdles attach the upper limbs to the body trunk • Pelvic girdle secures the lower limbs Clavicles (Collarbones) • S-shaped bones • Small, fragile • Smooth superior surface lies just beneath the skin Figure 7.22b, c Scapulae (Shoulder Blades) • The scapulae are triangular, flat bones lying on the dorsal surface of the rib cage, between the second and seventh ribs • Have three sides or borders (superior, medial, and lateral) and three angles (superior, inferior, and lateral) Scapulae (Shoulder Blades) Figure 7.22d, e The Upper Limb • Consists of the bones of the arms, forearms, wrists, and hands Arm (Brachium) • The humerus is the sole bone of the arm • It articulates with the scapula at the shoulder, and the radius and ulna at the elbow Arm Figure 7.23 a, b Ulna • In anatomical position, the ulna lies medial to the radius • Slightly longer than the radius • Forms the major portion of the elbow joint with the humerus Radius • Lateral bone (to the ulna) of the forearm • Thin at its proximal end, widened distally • The superior surface of the head articulates with the humerus Ulna & Radius Figure 7.24 a, b Carpus (Wrist) • Consists of eight carpal bones: – Scaphoid – Lunate – Triquetrum – Pisiform – Trapezium – Trapezoid – Capitate – Hamate “Sam Likes To Push The Toy Car Hard” Metacarpus (Palm) • Five numbered (1-5) metacarpal bones radiate from the wrist to form the palm – Their bases articulate with the carpals proximally, and with each other medially and laterally – Heads articulate with the phalanges Phalanges (Fingers) • Each hand contains 14 miniature long bones called phalanges • Fingers (digits) are numbered 1-5, beginning with the thumb (pollex) • Each finger (except the thumb) has three phalanges – distal, middle, and proximal • The thumb has no middle phalanx Wrist & Hand Pelvic Girdle (Hip) • The hip is formed by a pair of hip bones (coxal) • Together with the sacrum and the coccyx, these bones form the bony pelvis • The pelvis – Attaches the lower limbs to the axial skeleton with the strongest ligaments of the body – Transmits weight of the upper body to the lower limbs – Supports the visceral organs of the pelvis – Forms by the fusion of 3 bones: ilium, ischium, and pubis Pelvic Girdle (Hip) Figure 7.27a Illium Figure 7.27b Comparison of Male and Female Pelvic Structure • Female pelvis – Tilted forward, adapted for childbearing – True pelvis defines birth canal – Cavity of the true pelvis is broad, shallow, and has greater capacity • Male pelvis – Tilted less forward – Adapted for support of heavier male build and stronger muscles – Cavity of true pelvis is narrow and deep Comparison of Male and Female Pelvic Structure Table 7.4 Lower Limbs • Each lower limb consists of a femur (thigh), patella (knee cap), tibia & fibula (lower leg), tarsal bones (ankle), metatarsal (foot), and phalanges (toes) • They carry the weight of the erect body, and are subjected to exceptional forces when one jumps or runs • The sole bone of the thigh Femur (Thigh) • Longest and heaviest bone in the body • Articulates proximally with the hip and distally with the tibia and fibula Figure 7.28b Patella (Knee cap) • Large sesamoid bone Tibia (Shinbone) • Large medial bone of the leg • Receives the weight of the body from the femur and transmits it to the foot Fibula • Slender bone of the leg • Site for attachment of muscles that move the foot and toes Fibula • Sticklike bone with slightly expanded ends located laterally to the tibia • Major markings include the head and lateral malleolus Tibia & Fibula Figure 7.29a, b Tarsus (Ankle) • Composed of seven tarsal bones: 1.Talus 2.Calcaneus (heel bone) 3.Cuboid 4.Navicular 5.Medial Cuneiform 6.Intermediate Cuneiform 7.Lateral Cuneiform “Tom Can Control Not Much In Life” Tarsus Figure 7.31b, c Metatarsal Bones & Phalanges • Metatarsals – Five (I - V) long bones • Phalanges – The 14 bones of the toes – Each digit has three phalanges except the hallux, which has no middle phalanx Figure 7.31a Clinical Disorders and Diseases of the Skeletal System Cleft Lip/Palate • Facial and oral malformations that occur very early in pregnancy • Results when there is not enough tissue in the mouth or lip area, and the tissue that is available does not join together properly • Cleft lip – split or separation of the two sides of the upper lip • Cleft palate – split or opening in the roof of the mouth (hard or soft palate) • 1 in 700 babies; 4th most common birth defect in the US Cleft lip/palate cont. • The cause is unknown • May be linked to genetic and environmental factors (drugs, exposure to viruses or chemicals) • Eating, speech, and dental problems could result • Often requires multiple surgeries to treat Cleft Palate Vertebral Column: Curvatures Scoliosis: abnormal lateral curvature of the spine (occurs most often in the thoracic region) • Caused by a bone abnormality present at birth, abnormal muscles or nerves, trauma, or genetic • 2-3% of Americans at age 16 (girls are more prone to developing the condition) • Diagnosed by screening exams, bone exam, and X-ray • Treatments include braces or surgery (spinal fusion) Scoliosis Osteomalacia Softening of the bones due to a lack of Vitamin D or a problem with the body’s ability to break down and use Vitamin D Rickets - Children's form of osteomalacia Causes – not enough Vitamin D; not enough exposure to sunlight or malabsortption of Vitamin D by the intestines Symptoms - bone weakness, fractures that occur without real injury, and numbness Treatments – Vitamin D, calcium, and phosphorus supplements Osteoporosis • Bone loss outpaces bone regeneration • Bones weaken and lose mass • Bones become brittle and fractures occur more often • Found most often in women • Treatment may include; medication, diet changes, exercise Osteoarthritis • • • • Degenerative joint disease Most common type of arthritis (21 million) Breakdown of cartilage in joints Mostly occurs in the weight bearing joints, but it can occur anywhere • Causes cartilage to become stiff and lose its elasticity • As cartilage deteriorates, tendons and ligaments stretch, causing pain Osteoarthritis Symptoms: •Joint aching and soreness •Pain after overuse or long periods of inactivity •Joint swelling •Fluid accumulation Treatment: medication, physical therapy, surgery Knee Replacement surgery • Generally reserved for people over the age of 50 with severe osteoarthritis • Helps relieve pain & restore function in severely diseased knee joints • During surgery; a surgeon cuts away damaged bone and cartilage from your femur, patella, and tibia and replaces it with an artificial joint made of metal alloys, high-grade plastics, and polymers Fractures • A crack or break in a bone • Despite its mineral strength, bone can crack or even break if subjected to extreme loads, sudden impacts, or stresses from unusual directions Types of Fractures • Named according to their external appearance, their location, and the nature of the crack or break in the bone. • Two general categories: 1. Closed (simple) – fracture is internal 2. Open (compound) – fracture projects through the skin Common fracture types (cont’d) Common fracture types • Comminuted fractures • Spiral fractures Figure 6–16 (4 of 9) • Greenstick fracture Figure 6–16 (7 of 9) • Compression fractures Figure 6–16 (9 of 9) Depression fracture of the skull Treatment of a Fracture • Initial treatment for fractures of arms, legs, hands, and feet include splinting the extremity in the position it is found, elevation, and ice. • Edema (or swelling) What does this have to do with splinting and casting? • Closed Reduction – manual realignment • Open Reduction – surgically realignment Steps in the Repair of a Fracture Step 1 – • Immediately after the fracture, extensive bleeding occurs (blood vessels are broken). • A large blood clot, or fracture hematoma, soon closes off the injured vessels and leaves a fibrous meshwork in the damaged area. • The disruption of the circulation kills osteocytes (mature bone cells) around the fracture. • Dead bone soon extends along the shaft. Steps in the Repair of a Fracture Step 2 – • The cells of the endosteum (cellular layer) and periosteum undergo cell division and the daughter cells migrate into the fracture zone. • An external callus (hard skin) forms and encircles fracture • An internal callus organizes within the cavity and between the broken ends of the shaft • The broken ends have been temporarily stabilized Steps in the Repair of a Fracture Step 3 – • Osteoblasts (bone building cells) replace the central cartilage of the external callus with spongy bone • Calluses form a brace at the fracture site • Spongy bone now unites the broken ends • Fragments of dead bone are removed and replaced • If the fracture required a cast, it can be removed at this stage Steps in the Repair of a Fracture Step 4 – • Osteoclasts (remove and recycle bone matrix) and osteoblasts continue to remodel the region of the fracture (4 months to 1 year) • When remodeling is complete, the bone of the calluses is gone and only living compact bone remains. • The bone could be slightly thicker and stronger than normal at the fracture site Fracture repair Fracture repair (cont’d) Casts • Holds a broken bone in place as it heals • Help to prevent or decrease muscle contractions • Provide immobilization (the joints above and below the area) • Casts are made of plaster and fiberglass • Typically worn for 6-8 weeks Dislocation • Separation of two bones where they meet at a joint (no longer in normal position) • Caused by a sudden impact to the joint • May be hard to tell a dislocated bone from a broken bone • Generally take 3-6 weeks to heal • Possible ligament damage can occur Joints (Articulations) Joint (articulation) - Where two bones interconnect • Functions – Bind parts of the skeletal system – Enable the body to move in response to skeletal muscle contractions Classification of Joints: The three structural (by the type of tissue that binds the bones at each junction) classifications are: 1. Fibrous joints 2. Cartilaginous joints 3. Synovial joints Joints can also be grouped functionally according to the degree of movement possible at the bony junction: 1. Immovable joints 2. Slightly movable joints 3. Freely movable joints Fibrous Joints • The bones are close together and may interlock; between bones in close contact • Extremely strong joints • There is no/limited joint movement Examples: 1. Between tibia and fibula (bound by a sheet) 2. Suture – between flat bones of the skull 3. Binds the teeth to bony sockets in jaw Figure 8.1a Cartilaginous Joints • Hyaline and fibrocartilage connects the bones of this type of joint • Limited movement Examples: 1. Joints that are temporary structures that disappear during growth (immature long bone) 2. Sternum and first rib 3. Pubic symphysis in the pelvis 4. The joint formed by the bodies of two adjacent vertebrae Figure 8.2a Synovial (Freely Movable) Joints • Most joints of the skeletal system are synovial • Allow free movement • More complex structure • Consist of articular cartilage; joint capsule; synovial membrane (synovial fluid) Synovial Joints: General Structure 1. Articular cartilage (hyaline cartilage) – resists wear and tear/minimizes friction 2. Joint capsule – holds together the bones 3. Ligaments – reinforce the joint capsule/bind the ends of the bones/prevents excess movement Figure 8.3a Synovial Joints: General Structure 4. Synovial membrane – inner layer of the joint/cover all surfaces within the joint capsule a. Synovial cavity – sac within the membrane b. Synovial fluid – moistens and lubricates the smooth cartilaginous surfaces of the joint Synovial Joints: General Structure 5. Menisci – some synovial joints are divided into two compartments by discs of fibrocartilage 6. Bursae – fluid-filled sacs found in some synovial joints/cushion and aid the movement of tendons that glide over bony parts or other tendons (knee and elbow for example) 7. Tendons – connect bones to muscles/limit ROM 8. Fat pads – protection/packing material Types of Synovial Joints • Based on the shapes of the articular surfaces • Each type of joint permits a different type and range of motion Types: • Gliding/Plane • Hinge • Pivot • Condylar/Ellipsoidal • Saddle/Sellar • Ball and socket Types of Synovial Joints Ball and Socket Joints - Consists of a bone with a slightly egg-shaped head that articulates with the cup-shaped cavity of another bone - Allows a wider range of motion; movements in all planes as well as rotational movement - Examples – hips and shoulder joints Types of Synovial Joints Hinge joints - Convex surface of one bone fits in the concave surface of another bone - Examples – elbow, joints of the phalanges, knee, jaw Types of Synovial Joints Condylar (Ellipsoidal) Joints - The ovoid condyle of one bone fits into the elliptical cavity of another bone - Permits a variety of movements in different planes (rotational movement is not possible) - Examples – joints between the metacarpals and phalanges Types of Synovial Joints Gliding (Plane) joints – Articular surfaces (the part of the bone that connects with the other bone) are essentially flat or slightly curved – Allows sliding or back and forth motion and twisting movements – Examples: wrist and ankles; between the articular processes of the vertebrae; sacroiliac joints; joints formed by ribs 2 – 7 connecting with the sternum Gliding (Plane) Joint Types of Synovial Joints Saddle Joints - Forms between bones whose articulating surfaces have both concave and convex regions - The surface of one bone fits the complementary surface of the other - Permits a variety of movements, mainly in two planes - Example – joint between the carpal and metacarpal of the thumb Types of Synovial Joints Pivot Joints - The cylindrical surface of one bone rotates in a ring formed of bone and a ligament - Movement is limited to rotation around a central axis - Examples – joint between the proximal ends of the radius and ulna; the arch of the atlas rotates around the dens of the axis (neck) Injuries/Conditions Review Match the condition with the pictures 1. 2. A. Osteoarthritis B. Osteoporosis C. Osteomalacia D. Scoliosis 3. 4. Fractures Match the fracture with the pictures A. Depressed B. Greenstick C. Compression D. Spiral 3. 1. 2. 4. Fractures Match the fracture with the pictures 1. A. Compound B. Simple C. Comminuted D. Transverse 2. 3. 4. Bone Bingo Frontal Lacrimal Clavicle Sternum Humerus Phalanges Patella Metatarsals Coccyx Zygomatic Mandible Scapula Vertebrae Radius Femur Fibula Metacarpals Occipital Nasal Maxilla Ribs Ulna Carpals Tibia Tarsals Sacrum Parietal