Skeletal

1. Skeletal

2. the skeletal system is strong, light, adapted for protection, and adapted for motion • axial – longitudinal axis • appendicular– limbs and girdles • also includes joints, cartilages, and ligaments

3. functions • support – internal framework, supports/anchors all soft organs • protection – protect by surrounding softer body organs • movement – skeletal muscle attach to bones via tendons and are used as levers to move • storage – fat is found in internal cavities, Ca and P in bone tissue • blood cell formation (hematopoiesis) – in marrow of some bones

4. types • compact bone – dense and smooth • spongy bone – small needle-like pieces with open spaces

6. classification • the shape of each bone determines its function • long bones – • longer than they are wide • shaft with a head at each end • mostly compact • all limb bones except metacarpals and metatarsals • short bones – • generally cube shaped • mostly spongy • metacarpals and metatarsals

8. flat bones – • thin, flat, and curved • 2 thin layers of compact bone with a layer of spongy bone in between • skull, ribs, sternum • irregular bones – • do not fit any other category • vertebrae and hips • bone markings are where muscles/tendons/ligaments attach and where blood vessels/nerves pass

10. structure of a long bone • diaphysis – • the shaft • mostly compact bone • covered with periosteum • epiphyses – • the ends of the long bones • thin layer of compact bone surrounding spongy bone • covered with cartilage to decrease friction • yellow marrow (medullary) cavity – • storage area of fat tissue in adults • contains red marrow in infants that make RBCs

12. microscopic anatomy • mature bone cells (osteocytes) are found in cavities (lacunae) and secrete a solid matrix • lacunae are arranged in a circle (lamella) around a central canals (osteonic canal) • several lamella (lamellae) surrounding a single central canal is an osteon • canals run lengthwise thru the bone to carry blood vessels and nerves from end to end • tiny canals (canaliculi) run horizontally to connect all lacunae • allows all osteocytes to be well supplied with nutrients even though the matrix is solid • larger canals (perforating) run horizontally between the osteons

13. bone formation, growth, and remodeling • the skeleton is formed from bone and cartilage • 2 of the strongest tissues in the body • babies have cartilage that is gradually replaced by bone (ossification) • cartilage contains osteoblasts which secretes bone matrix • bone matrix replaces cartilage matrix • osteocytes replace chondrocytes • cartilage becomes bone • process is continually repeated • result is bone growth to lengthen long bones • growth hormone starts the process and sex hormones continue growth during puberty • cartilage only remains in ears, nose, ends of ribs, and joints

14. bones are continually remodeled • to release Ca into the blood • Ca levels drop below homeostatic levels • parathyroid glands release hormone to activate bone-destroying cells (osteoclasts) • bone matrix is broken down to release Ca into the blood • to remove Ca from the blood • blood Ca levels that are too high cause hypercalcemia • Ca is removed from the blood and deposited into bone matrix • to retain normal proportions during growth • bones become thicker with age • bones form larger projections in response to bulkier muscles • osteoblastslay down new matrix, become trapped, and become osteocytes

15. Bone Fractures • in youth, most fractures/breaks occur from trauma that twists or smashes bones • in older adults, bones thin/weaken so fractures are more common • fractures are set by reduction and immobilization • closed reduction is by external manipulation • open reduction is by surgery and requires bone to be pinned/wired • hematoma forms where the bone breaks • cartilage callus is replaced by osteoblasts and osteocytes to form a spongy bony callus • bony callus continually remodeled and strengthened into a permanent patch

17. Explain how this picture makes you feel and describe it using vocabulary you have learned about bones, tissues and integument.

18. Axial Skeleton • forms the longitudinal axis (skull, vertebral column, bony thorax) • skull • cranium • encloses/protects brain • frontal bone – forehead/brows/superior orbit • parietal bones – superior and lateral cranium • temporal bones – inferior to parietal • external auditory meatus – ear canal • styloidprocess – needle-like projection for neck muscle attachments • zygomaticprocess – bridge that joins with zygomatic bone to form cheekbones • mastoid process – contains air cavities and provides attachment site for neck muscles • jugular foramen – allows for passage of jugular vein • carotid canal – allows for passage of carotid arteries

19. occipital bone – floor and back wall of skull • foramen magnum – passage of spinal cord to the brain • occipital condyles – rests the skull on the first vertebra • sphenoid – part of the floor of cranial cavity, part of the orbit • ethmoidbone – irregular and anterior to sphenoid, forms roof of nasal cavity and medial orbit

21. facial bones • holds the eyes in position • attached to each other with sutures (except mandible) • maxillae – fuse to form upper jaw, carry teeth in alveolar margin • palatine process – hard palate • zygomaticbones – lateral orbits, connect with temporal bones to form cheekbones • lacrimalbones – medial orbits, groove for tear ducts • nasal bones – bridge of the nose • vomerbone – median line in the nasal cavity that forms the septum • inferior conchae – thin curved bone projecting into the nasal cavity • mandible – strongest bone of the face, lower jaw

22. hyoid bone • not a part of the skull be closely related to the mandible and temporal bone • only bone not articulated with another bone • suspended midneck above the larynx by attachments to the styloid process • serves as a movable base for the tongue and attachment site for neck muscles • fetal skull • regions of skull are not yet ossified and are connected by fibrous membranes (fontanels) • fontanels allow fetal brain to grow during late pregnancy and the skull to compress during birth

24. vertebral column (spine) • made of 26 irregular bones (reinforced by ligaments), the sacrum, and coccyx • separated and cushioned by flexible intervertebraldiscs • supports the skull and protects the spine • all have 6 common features: • body – weight-bearing part, anterior side • vertebral arch – formed from the joining of all extensions • vertebral foramen – spinal cord canal • transverse processes – 2 lateral projections • spinousprocess – posterior projection • superior articular processes – projections allowing vertebra to articulate (join) together

26. cervical vertebrae (C1-C7) • 7 vertebrae in the neck region • first is the atlas (supports the skull and allows anterior/posterior movements) • second is the axis (allows lateral movements) • remaining 5 are smallest and lightest • all have transverse foramen for vertebral arteries travelling to the brain

27. thoracic vertebrae(T1-T12) • next 12 vertebrae • from the most superior rib to the most inferior rib • designed to articulate with the head of the ribs • lumbar vertebrae (L1-L5) • lower back • massive bodies to withstand heavy stresses

28. sacrum • fusion of 5 vertebrae • articulates with L5 (superior), the coccyx (inferior), and the ilium (laterally) • coccyx (tailbone) • fusion of 3 to 5 small vertebrae • remnant of mammalian tails

30. bony thorax (thoracic cage) • thoracic vertebrae • 12 vertebrae that articulates with the ribs • sternum (breastbone) • fusion of 3 bones (manubrium, body, and xiphoid process) • contains hematopoietic tissue

31. ribs • 12 pairs that all articulate with the thoracic vertebrae • first 7 pairs are true ribs – articulate with the sternum by costal cartilage • next 5 pairs are false ribs – articulate indirectly to sternum or not at all • (last 2 pair lack articulation and are floating ribs)

33. appendicular skeleton • composed of 126 bones of the limbs • the pectoral and pelvic girdles (attach the limbs to the axial skeleton)

34. pectoral girdle consists of two bones (clavicle, scapula) • very light and allows upper limb to have exceptionally free movement • attaches to the axial skeleton at only one point (sternoclavicular joint) • clavicle is a slender, doubly curved bone • attaches to the manubrium of the sternum medially and to the scapula laterally • acts as a brace to hold the thorax • helps prevent shoulder dislocation

35. scapula is triangular • not directly attached to the axial skeleton • loosely held in place by trunk muscles • glenoidcavity is a shallow socket that receives the head of the arm bone • (poorly reinforced by ligaments) • loose attachment of the scapula allows it to slide back and forth against the thorax

37. bones of the upper limbs • arm is formed by a single bone (humerus) • forearm is formed by two bones (radius and the ulna) • (in anatomical position, the radius is lateral and the ulna is medial) • hand consists of the carpals, the metacarpals, and the phalanges • (carpals form the wrist, metacarpals form the palm, phalanges forms the fingers)

39. pelvic girdle is formed by two coxal bones (hip bones) • hip bones, sacrum, and coccyx form the bony pelvis • each hip bone is formed by the fusion of three bones (ilium, ischium, and pubis) • ilium- large, flaring bone, forms most of the hip bone • ischium- the most inferior part, receives body weight when sitting • pubis - the most anterior part • all fuse at a deep socket (acetabulum) that receives the head of the femur

41. bones of the lower limbs • carry total body weight when standing • bones are much thicker and stronger than the comparable bones of the upper limb • femur • only bone in the thigh • heaviest/strongest bone in the body • head articulates with the acetabulum • neck is a common fracture site • slants medially as it turns downward (bring knees in line with the body's center of gravity) • tibia is larger, medial, and the proximal end articulates with the distal femur to form the knee • fibula lies alongside the tibia, is thin, sticklike, and has no part in forming the knee

43. foot is composed of tarsals, metatarsals, and phalanges • tarsus (ankle) supports body weight – especially the calcaneus (heel) and talus • serves as a lever that propels the body forward when walking/running • bones are arranged to form three strong arches • two longitudinal (medial and lateral) and one transverse • ligaments/tendons hold bones firmly in the arched position but allow movement

45. joints (articulations) • with one exception (hyoid) every bone forms a joint with at least one other bone • two functions - hold the bones together securely / give the rigid skeleton mobility • classified in two ways - functionally and structurally

46. functional - focuses on the amount of movement • freely movable joints (limbs) • immovable / slightly movable joints (axial skeleton)

47. structural - fibrous, cartilaginous, and synovial joints • fibrous • immovable • cartilaginous • bone ends connected by cartilage • slightly movable (intevertebral joints) • synovial • surfaces enclosed by a capsule of tissue and ligaments • are freely movable • more flexibility than other joint types (flexibility varies slightly)