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Skeletal System

Skeletal System. Types of Animal Skeletons. Endoskeleton Internal skeleton Ex. Humans Exoskeleton External skeleton Ex. Insects, Clams Hydrostatic Internal fluids receive and redistribute applied forces Ex. Annelids. Bone Functions. Movement Protection Support Mineral Storage

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Skeletal System

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  1. Skeletal System

  2. Types of Animal Skeletons • Endoskeleton • Internal skeleton Ex. Humans • Exoskeleton • External skeleton Ex. Insects, Clams • Hydrostatic • Internal fluids receive and redistribute applied forces Ex. Annelids

  3. Bone Functions • Movement • Protection • Support • Mineral Storage (Ca++, P) • Energy Storage (Yellow Marrow – Fat) • Hematopoiesis - Produce Blood Cells (Red Marrow)

  4. Name Long Short -Sesamoid Flat Irregular Examples femur, humerus, other limb bones except wrist, ankles, and patella carpals, tarsals patella cranium, ribs, scapula vertebrae, mandible, hip bones Types of Bones Characteristics Longer than they are wide cube shaped Sesame seed shaped, formed in tendon flattened section more than 1 shape

  5. Classification of Bones (cont.) a = Long Bone b = Short Bone c = Flat Bone d = Irregular Bone e = Sesamoid Bone

  6. Anatomy of a Long Bone • Epiphyseal Plate: hyaline cartilage that grows during childhood to lengthen the bone • Epiphyseal Line: remnant of epiphyseal plate, found only in adults Diaphysis: long portion in middle Epiphysis: shorter section at end Epiphysis Periosteum: Bone covering, outer layer of dense irregular c.t.; inner layer of osteoblasts and osteoclasts, supplied with nerves and blood vessels Compact Bone: dense layer over medullary cavity; supports weight Articular Cartliage: Covers epiphysis at joints, reduces friction, absorbs shock Spongy Bone: lattice of trabecula filled with red marrow; nourished directly from circulating blood Medullary Cavity: Hollow center of diaphysis, contains yellow marrow

  7. Bone (Osseous) Tissue Osteocytes – widely spaced, surrounded by intercellular substances • Osteoid(organic): Osteoblasts: add salts Collagenous Fibers • Hydroxyapatite • (inorganic): Osteoclasts: remove salts Mineral Salts (calcium, phosphorus) - Provides strength and hardness to bone

  8. Osteon: structural unit of matrix and canals • Lamella (little plate): rings of calcified matrix, intercellular substance • Volkmann’s Canals: horizontal canals; allow blood vessels and nerves to connect • Haversian Canals: vertical canals; allow blood vessels and nerves to connect • Canaliculi: tiny canals that allow osteocytes to exchange nutrients and wastes • Lacunae: space for osteocytes

  9. Ossification (bone formation) • begins around 6th or 7th week post conception • ends by age 25 2 types

  10. Intramembranous Ossification • Bone forms within fibrous membranes (skull, clavicle) • Osteoblasts cluster in fibrous membranes: Center of Ossification • Calcification: intercellular substances and collagen are secreted into a network where calcium can be deposited • Trabecula Formation: complete when osteoblasts are completely surrounded by calcified matrix • Trabecula continue to fuse together = spongy bone • Red marrow fills in space

  11. Endochondral Ossification (most bones) • Cartilage is formed in embryonic stage • Covered by perichondrium (membrane) Primary Ossification: Begins at periosteal collar (around middle of diaphysis) - Blood vessel penetrates perichondrium - Stimulates osteoblast formation - Bone replaces cartilage: - Intercellular substances calcify - Nutrients are cut off by hardened matrix Secondary Ossification: - Periosteum thickens bones, especially at ends - Blood vessel penetrates ends, process repeats EXCEPT - 2 areas of cartilage will remain: - articulating cartilage - epiphyseal plates (allow lengthwise growth of bones)

  12. Bone Remodeling • Normal bone is always undergoing remodeling • Removes old bone tissue and replaces it with new bone tissue • Remodeling cycle continues throughout life to maintain healthy bone • About 20% of all bone tissue is replaced annually

  13. Bone Remodeling • Sites of remodeling • Where bone is experiencing growth • Mechanical stress • Microfractures • Breaks

  14. Bone Remodeling Five Phases • Activation • Resorption • Reversal • Formation • Quiescence

  15. Bone Remodeling • Activation • Pre-osteoclasts are attracted to the remodeling sites • Pre-osteoclasts fuse to form multinucleated osteoclasts • Resporption • Osteoclasts dig out a cavity, called a resorption pit, in spongy bone or burrow a tunnel in compact bone

  16. Bone Remodeling • Calcium can be released into the blood for use in various body functions • Osteoclasts disappear • Reversal • Mesenchymal stem cells, pre-cursors to osteoblasts, appear along the burrow or pit where they… • …proliferate (increase in number) and differentiate into preosteoblasts

  17. Bone Remodeling • Formation • Pre-osteoblasts mature into osteoblasts at the surface of the burrow or pit • Osteoblasts release osteoid at the site, forming a new soft matrix • The new matrix is mineralized with calcium and phosphorous • Quiescence • Site remains dormant until the next cycle

  18. Axial Backbone Skull Ribs Sternum Appendicular Everything Else System Divisions

  19. Axial Skeleton

  20. Axial Skeleton • Skull • All bones immovable except mandible • Cranium • Paranasal Sinuses • Cavities within bones of skull • Lined by mucous membranes • Fontanels • Fetal/Child • Soft spots • Incomplete Ossification • Facial Bones Fontanels of fetal skull

  21. Axial Skeleton • Hyoid Bone • No articulation

  22. Axial Skeleton • Vertebral Column • Protects spinal cord • Shock absorbers • Vertebrae separated by intervertebral disks • Fibrocartilage

  23. Axial Skeleton • 7 Cervical Vertebrae • Atlas (C1) and Axis (C2) • Allow rotation of the head • 12 Thoracic Vertebrae • 5 Lumbar Vertebrae • Remember the common mealtimes to help you remember the number of vertebrae • Breakfast = 7, Lunch = 12, Dinner = 5

  24. Axial Skeleton • Sacrum • Five fused vertebrae • Coccyx • Tailbone • Bony Thorax • Sternum • Manubrium, Body, Xiphoid process • 12 pairs of ribs

  25. Axial Skeleton • Ribs • True ribs • Attached to sternum • 7 pair • False ribs • Attached to costalcartilage of 7th rib • 3 pair • Floating ribs • No anterior attachment • 2 pair

  26. Appendicular Skeleton

  27. Appendicular Skeleton • Pectoral (shoulder) girdle • Scapula and clavicle (collar bone) • Upper limbs • Humerus (arm) • Radius and ulna (forearm) • Carpals (wrist) • Metacarpals (palm) • Phalanges (fingers and thumb)

  28. Appendicular Skeleton • Pelvic (hip) Girdle • Coxal (hip) bones Female vs. Male FemaleMale Pubic arch = 90˚ Pubic arch = 60˚ Distance between iliac Bones are heavier crest wider Bone markings more prominent

  29. Appendicular Skeleton • Coxal Bones have 3 parts • Ilium (superior) • Ischium (posterior) • Pubis (anterior)

  30. Appendicular Skeleton • Lower Limbs • Femur (thigh) • Longest bone in body • Tibia and Fibula (leg) • Tibia = medial, Fibula = lateral • Patella (knee cap) • Tarsals • Ankle • Metatarsals • Instep • Phalanges • toes

  31. Joints • Points of contact between bones • Functions • Hold skeleton together • Mobility

  32. Joints (based on functional differences) (Articulations) Synarthroses (axial) Amphiarthroses (axial) Diarthroses (appendicular)

  33. Synarthroses (Fibrous Joints) • No Movement Joining bones connected by fibrous connective tissue Example: sutures in skull, teeth

  34. Amphiarthroses (Cartilaginous joints) • Slight Movement Joining bones connected by cartilage Example: vertebral joints

  35. Diarthroses (Synovial) • Free Movement • Surrounded by synovial cavity: • lined with synovial membrane • - lubricates bones/cartilage • - structured like a sleeve • bursa often found between the bones • ligaments secure bone together • - grow out of periosteum

  36. Types of Diarthrotic Joints Ball and Socket Head of one bone fits in concave socket of another bone Allows widest range of motion Hinge Head of one bone fits against concave socket of another Allows only flexion and extension Pivot Small pin of one bone fits in arch of another Allows rotation Saddle Only found where thumb fits wrist Allows movement in many directions Gliding Flat surfaces of bones fit against each other Allows little directional movement, only gliding Condyloid/Ellipsoid Oval projection fits into an elliptical socket Allows most movement, no rotation

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