Skeletal System

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

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

11. 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

12. 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)

13. 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

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

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

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

17. 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

18. 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

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

22. Axial Skeleton

23. 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

24. Axial Skeleton • Hyoid Bone • No articulation

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

26. 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

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

28. 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

29. Appendicular Skeleton

30. 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)

31. 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

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

35. 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

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

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

38. Synarthroses (Fibrous Joints) • No Movement Joining bones connected by fibrous connective tissue Example: sutures in skull, gomphosis at teeth, costal cartilage

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

40. 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

41. Types of Diarthrotic Joints Ball and Socket Ball-like 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 rounded or pointed pin of one bone fits in arch or ring of another Allows rotation Saddle Only found where thumb fits wrist, saddle and rider shape Allows side-side and back and forth movement Gliding Flat surfaces of bones fit against each other Allows gliding in 2 planes, side – side or front-back Condyloid/Ellipsoid Oval projection fits into an elliptical socket Allows side-side and back and forth movement

43. Movement of Synovial Joints Insertion: location at which a muscle attaches to a moving bone Origin: location at which a muscle attaches to a stationary bone

44. Movement of Synovial Joints • Actions: Flexion: Decreasing the angle between bones Dorsiflexion: Moving the top of the foot toward the ankle

45. Movement of Synovial Joints • Actions: Extension: Increasing the angle between bones Plantar Flexion: Standing on toes

46. Movement of Synovial Joints • Actions: Hyperextension: Increasing the angle beyond normal positions

47. Movement of Synovial Joints • Actions: Abduction: Moving away from the vertical midline of the body Adduction: Moving toward the vertical midline

48. Movement of Synovial Joints Circumduction: Moving a limb so that the distal end forms a circular pattern Rotation: Moving around a central axis

49. Movement of Synovial Joints Pronation: Turning the hand to point the palm downward or posterior Supination: Turning the hand to point the palm upward or anteriorly

50. Movement of Synovial Joints Eversion: Turning the foot to point the sole more outward or laterally Inversion: Turning the foot to point the sole inward or medially