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Skeletal System

Explore the skeletal system composed of 206 bones, its functions, bone formation, growth, and the different types of bones. Discover the axial and appendicular skeleton, along with the joints present in the body.

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Skeletal System

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  1. Skeletal System

  2. Made up of bones • In an adult there are 206 bones

  3. Functions of the Bone 1.Framework: support body’s muscles, fat, and skin • 2. Protection a. surrounds vital organs to protect them • examples: skull surrounding brain; ribs to protect heart • 3. Levers: attach to muscles to help provide movement • 4. Production of blood cells: red and white blood cells and platelets

  4. Formation of bones • Initially collagen fibers secreted by fibroblasts then cartilage deposits between fibers • Skeleton fully formed by 2nd month of fetal development – all cartilage

  5. Formation continued… • 8th week of fetal development – ossification begins - which is mineral matter being deposited and cartilage is replaced

  6. Formation continued… • During childhood and adolescence, ossification exceeds bone loss • During adulthood and middle age, ossification equals bone loss • After age 35, bone loss exceeds ossification

  7. Bone Growth • Grows in lengthat the epiphyseal line • Grows in width by addition of bone to the surface

  8. Controlled by anterior pituitary gland (growth hormone)

  9. Four major types of bones • long • short • flat • irregular

  10. Two sections of skeleton • Axial – forms main trunk of body; composed of the skull, spinal column,ribs, and sternum

  11. Appendicular - forms extremities (arms and legs); composed of shoulder girdle, arm bones, pelvic girdle, and leg bones

  12. Axial skeleton • Skull • Composed of cranial and facial bones • Cranium • Surrounds and protects the brain • Made of eight bones • Frontal • Two parietal • Two temporal • Occipital • Ethmoid • Sphenoid

  13. At birth the cranium is not solid bone • Spaces called fontanels or “soft spots” allow for enlargement of skull as brain growth occurs • Fontanels are made of membrane and cartilage • Turn into solid bone by about 18 months of age

  14. Facial Bones • Fourteen facial bones 1). Main bones a). Mandible: lower jaw b). Maxilla: two bones forming upper jaw c). Zygomatic: two cheek bones d). Nasal: five bones in upper part of nose e). Lacrimal: two bones at inner aspect of eyes f). Palatine: two bones of hard palate or roof of mouth

  15. Sutures • areas where cranial bones have joined together

  16. Sinuses • a. Air spaces in the bones of the skull • b. Provide strength with less weight • c. Act as resonating chambers for the voice • d. Lined with mucous membranes

  17. Foramina • a. Openings in bones • b. Allow nerves and blood vessels to enter or leave bone

  18. Vertebrae • Spinal column made of 26 bones called vertebrae • Protect the spinal cord • Provide support for head and trunk

  19. Main sections: • Cervical: 7 neck vertebrae • Thoracic: 12 vertebrae in back of chest, attach to ribs • Lumbar: 5 vertebrae by waist • Sacrum: 5 fused bones, triangular in shape, forms dorsal part of pelvis • Coccyx: 3-4 fused bones, called tailbone, slightly moveable

  20. Intervertebral Disks • 1) Pads of cartilage tissue that separate vertebrae • 2) Act as shock absorbers • 3) Permit bending and twisting movements of vertebral column

  21. Ribs • 1) 12 pairs of long slender bones • 2) Attach to thoracic vertebrae on dorsal surface of body • a) True ribs: First 7 pairs of ribs; Attach directly to sternum on front of body • b) False ribs: Next 5 pairs of ribs; first 3 pairs attach to cartilage of rib above • c) Floating ribs: last two pairs of false ribs; no attachment on front of body

  22. Ribs continued…

  23. Sternum • Breastbone 1) Consists of three parts a) Manubrium: upper region b) Gladiolus: body or center area c) Xiphoid process: small piece of cartilage at bottom 2. Two clavicles attach to the manubrium by ligaments 3.Ribsattach to sternum with costal cartilages to form a cage that protects the heart and lungs

  24. Appendicular Skeleton

  25. Shoulder Girdle (aka Pectoral Girdle) • Two clavicles • Two scapula's (scapulae)

  26. Upper Extremities • Humorous: upper arm • Radius: thumb side of forearm • Ulna: Little finger side of forearm • Carpals (8): wrist bones • Metacarpals (5): hand bones • Phalanges (14): finger bones

  27. Pelvic Girdle • Two os coxae: contains the acetabulum (hip socket) • Join with sacrum on dorsal part of body • Join together at a joint called the pubic symphysis on ventral part of body

  28. Each os coxae made of three bones that are fused or joined • Ilium • Ischium • Pubis

  29. Obturator foramen • 1) Opening between the ischium and pubis • 2) Allows for passage of nerves and blood vessels to and from the legs

  30. Lower Extremities • Femur: thigh bone • Patella: kneecap • Tibia: medial bone in lower leg, shin bone • Fibula: Lateral bone of lower leg, small than tibia • Tarsals (7): ankle bones (calcaneous is heel bone) • Metatarsals (5): bones forming instep of foot • Phalanges (14): toe bones

  31. Joints (a.k.a. Articulations) • Synarthrotic • Immovable • Cranium • Amphiarthrotic • 1)Limited movement • 2)pubic symphysis, vertebral joints, sacroiliac joint • Diarthrotic • Freely movable • Gliding: wrist • Pivot: between radius and ulna • Ball and socket: hip, shoulder • Hinge: elbow

  32. Bone Composition, Shape & Bone Marrow Types of Bone Based on Composition 1. Compact Bone • Very dense • Stress bearing • Femur, tibia, humorous

  33. 2. Cancellous Bone • Light, spongy. • Low stress areas where weight of bone would be a problem. • Found at ends of long bones, ribs, sternum, hips, vertebrae, cranium.

  34. Classification of Bones According to Shape Long Bones (extremities): levers 1. Parts of long bones: • Epiphysis: at ends, cancellous bone • Diaphysis: shaft, compact bone • Medullary Canal: • Cavity in diaphysis • Filled with yellow marrow

  35. 4. Endosteum: • Membrane that lines medullary canal • Keeps yellow marrow intact • Produces some bone growth

  36. 5. Periosteum: • Tough membrane covering outside of bones • Contains blood and lymph vessels • Contains osteoblasts: special cells that form new bone tissue • Necessary for bone growth, repair, and nutrition

  37. 6. Articular cartilage: • Thin layer covers the epiphysis • Acts as a shock absorber when two bones meet to form a joint

  38. 7. Long bones include: Tibia Femur Fibula Humorous Clavicle Ulna Radius

  39. Short Bones • Cubed shaped • Allow flexible movement • Cancellous bone covered by compact bone

  40. Short Bones include:

  41. Flat Bones • Flat plates • Protect vital organs • Provide broad surface area for muscle attachment

  42. Flat bones include: Facial Bones Scapula Cranial Bones Sternum

  43. Irregular Bones • Peculiarly shaped to provide support & protection • Allows flexibility Ribs Vertebra Hip bones Ear bones Hyoid bone

  44. Sesamoid Bone • Extra bones found in certain tendons. Patella

  45. Bone Growth • Grow in length at epiphyseal line • Grow in width by addition of bone to surface • Controlled by anterior pituitary (growth hormone)

  46. Growth Hormone Dysfunction • Dwarfism: hypofunction • Giantism: hyperfunction • Acromegaly: hyperfunction after puberty; enlarges bones of hands, feet, and face.

  47. Bone Marrow • Yellow Marrow • Inside medullary canal • Mainly fat cells

  48. Bone Marrow continued… • Red Marrow 1. Found in certain bones such as: • Vertebrae • Ribs • Sternum • Cranium • Proximal ends of humorous & femur 2. Produces RBC, platelets & some WBC 3. Important in the manufacture of blood & is involved with the body’s immune response 4. Used in diagnosing blood diseases 5. Given as transplants to people with defective immune systems

  49. Diseases & Disorders of the Skeletal System

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