The Skeletal System. Divisions of the Skeletal System The human skeletal system is divided into two major divisions  Axial Skeleton  Appendicular skeleton

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The Skeletal System Slide 2 Divisions of the Skeletal System The human skeletal system is divided into two major divisions Axial Skeleton Appendicular skeleton Slide 3 Axial Skeleton The axial skeleton contains the bones of the head, neck, and torso (80 bones total) Slide 4 appendicular skeleton The appendicular skeleton contains the bones of the upper and lower extremities (126 bones total) Slide 5 Human Skeleton The human skeleton has a total of 206 bones in all Slide 6 Bones Functions: Support Protection Movement Storage Blood cell formation Slide 7 Bones Function- Support Form the internal framework that supports and anchors all soft organs Slide 8 Bones Function- Protection Bones protect soft body organs Ex. Skull protects brain Slide 9 Bones Function- Movement Skeletal Muscles attach to bones by tendons Bones are used as levers to move body Slide 10 Bones Functions-storage Fat is stored in internal cavities of bones Slide 11 Bones Functions-storage Store minerals Most importantCalcium and phosphorus Slide 12 Bones Functions-storage Calcium in its ion form (Ca 2+ ) must always be present in blood for nervous system to transmit messages For muscles to contract For blood to clot Bones are a storage place for Calcium Slide 13 Bones Functions-storage Blood cell formation Hematopoiesis (formation of blood cells) occurs in the cavities of bone marrow Slide 14 Bones Classification of bones 2 basic types of bone types Compact Bone Spongy Bone Slide 15 Bones Compact Bone Dense Looks smooth Slide 16 Bones Spongy Bone Small needle-like pieces of bone Lots of open space Slide 17 Slide 18 Shapes of Bones Long Bones Short Bones Irregular Bones Slide 19 Bones Long Bones Longer than they are wide Usually have a shaft with heads at both ends Mostly compact bones most bones of limbs Slide 20 Bones Short Bones Generally cube-shaped Mostly spongy bone Ex. Patella (knee cap), bones of wrist and ankle Slide 21 Flat Bones Thin, flattened, usually curved Two thick layers of compact bone sandwiching a layer of spongy bone Bones of skull, ribs, sternum Slide 22 Irregular Bones Dont fit other categories Ex. Vertebrate, hip bone Slide 23 Structure of a long bone Diaphysis- Shaft Makes up most of the bones length Composed of compact bone Covered and protected by periosteum Slide 24 Structure of a long bone Cavity of shaft In infants- this area forms blood cells Red marrow In adults primarily filled with yellow marrow (adipose) Called yellow marrow cavity or medullary cavity Red marrow is confined to spongy bone Slide 25 Structure of a long bone Epiphyses- the ends of the long bone Epiphyseal line Thin line spanning the epiphysis Slide 26 Structure of a long bone Epiphyseal plate Plate of hyaline cartilage Causes the lengthwise growth of a long bone By end of puberty the plate is completely replaced by bone Slide 27 Structure of Long Bone Surfaces of bones arent smooth Bumps, holes, and ridges Bone markings Reveal where muscles, tendons, and ligaments were attached Reveal where blood vessels and nerves passed Slide 28 Structure of Long Bone Bone markings Projections or processes- Grow out from the bone surface Depressions or cavities Indentations in the bone Slide 29 Structure of a long Microscopic anatomy Compact bone: To the naked eye looks very dense With microscope we see a much different picture! Slide 30 Structure of a long Microscopic anatomy Compact bone Passageways carrying nerves and blood vessels Provides living bone with nutrients and route for waste disposal Slide 31 Structure of Long Bone Osteocytes The mature bone cells Found in cavities of the bone matrix called lacunae ( a very tough matrix) Slide 32 Structure of Long Bone Osteocytes Lacunae arranged in concentric circles called lamellae Lacunae arranged around central (Haversian) canals Slide 33 Structure of Long Bone Perforating (Volkmanns) canals Run into the compact bone at right angles to the shaft Let the inside of bone communicate with outside Slide 34 Bone Formation, Growth, and Remodeling Embryos skeleton Primarily hyaline cartilage Young child Most of cartilage has been replaced by bone Remains in isolated areas Bridge of nose Parts of ribs joints Slide 35 Bone Formation, Growth, and Remodeling Most bones develop using hyaline cartilage structures as their models Ossification- the formation of bone Slide 36 Bone Formation, Growth, and Remodeling Ossification 2 major stages 1. hylane cartilage model is completely covered with bone by bone forming cells called osteoblasts Slide 37 Bone Formation, Growth, and Remodeling Ossification Step Two: Hyaline cartilage model is digested away Opens up a medullary cavity within newly formed bone Slide 38 Bone Formation, Growth, and Remodeling By birth Most hyaline cartilage models have been converted to bone Excepts two reasons Articular cartilages cover bone ends Epiphyseal plates Slide 39 Bone Formation, Growth, and Remodeling Articular cartilages Persist for life Reduce friction at the joint surfaces Slide 40 Bone Formation, Growth, and Remodeling How is the articular cartilage injured? Trauma- twisting, sport injury Certain diseases Gradually over time Slide 41 Bone Formation, Growth, and Remodeling When there is significant loss of the articular cartilage, the knee is considered to have arthritis. Slide 42 Bone Formation, Growth, and Remodeling Epiphyseal plates Provide for longitudinal growth of long bones during childhood New cartilage is formed on external surface Old cartilage is broken down and replaced by bony matrix Slide 43 Bone Formation, Growth, and Remodeling Epiphyseal plates Growth controlled by hormones Ends during adolescence, when the epiphyseal plates are completely converted to bone Slide 44 Bone Formation, Growth, and Remodeling How do bones widen? called Appositional Growth Osteoblasts in the periosteum add bone to the external face Osteoclasts in the endosteum remove bone from inner wall Slide 45 What happens when long bone growth ends? Slide 46 Bone Formation, Growth, and Remodeling Bone Remodeling Bones continually remodeled in response to 2 factors: 1. calcium levels in the blood 2. the pull of gravity and muscles on the skeleton Slide 47 Bone Formation, Growth, and Remodeling Bone Remodeling When blood calcium levels are low Parathyroid hormone (PTH) is released into blood PTH activates osteoclasts (bone destroying cells) to break down bone matrix and release calcium Slide 48 Bone Formation, Growth, and Remodeling Bone Remodeling When blood calcium levels are too high (hypercalcemia) Calcium is deposited in bone matrix as hard calcium salts Slide 49 Bone Formation, Growth, and Remodeling Bone Remodeling Essential for bones to: retain normal proportions Strengthen as body increases size and weight Slide 50 Bone Formation, Growth, and Remodeling Bone Remodeling Bedridden or physically inactive people tend to lose bone mass and atrophy Because they arent subjected to stress Slide 51 Bone Formation, Growth, and Remodeling Rickets Disease of children in which bones fail to calcify Bones soften and definite bowing of weight-bearing bones of legs occurs Slide 52 Bone Formation, Growth, and Remodeling Rickets Called osteomalacia in adults Causes Usually due to lack of calcium in diet Or lack of vitamin D Is needed to absorb calcium Slide 53 Divisions of the Skeletal System Axial Slide 54 Bones of the Axial Skeleton Bones of the axial skeleton are divided into four major groups 1) Bones of the Skull 2) Hyoid Bone 3) Bones of the Spinal Column 4) Sternum and Ribs Slide 55 Bones of the Axial Skeleton Bones of the Skull (28 total) Cranial Bones (8 total) form the cranium which surrounds the brain Slide 56 Bones of the Axial Skeleton Bones of the Skull (28 total) Cranial Bones 1) Frontal Bone (1 bone) Anterior Portion of Cranium (Forehead) Forms Anterior Cranial Floor Forms the Roofs of Orbits (Eye Sockets) Slide 57 Bones of the Axial Skeleton Bones of the Skull (28 total) Cranial Bones 2) Parietal Bone (2 bones) Forms Superior Portion of Cranium Slide 58 Bones of the Axial Skeleton Bones of the Skull (28 total) Cranial Bones 3) Temporal Bone (2 bones) Forms Lateral Portion of Cranium & Lateral Cranial Floor Slide 59 Bones of the Axial Skeleton Bones of the Skull (28 total) Cranial Bones 4) Occipital Bone (1 bone) Forms Posterior Portion of Cranium & Posterior Cranial Floor Slide 60 Bones of the Axial Skeleton Bones of the Skull (28 total) Cranial Bones 5) Sphenoid Bone (1 bone) Forms central portion of cranial floor Known as the keystone of the cranium because the sphenoid bone anchors all the other cranial bones Slide 61 Bones of the Axial Skeleton Bones of the Skull (28 total) Cranial Bones 6) Ethmoid Bone (1 bone) Complex, irregularly shaped bone found between the nasal and the sphenoid bones Slide 62 Bones of the Axial Skeleton Bones of the Skull (28 total) Facial Bones 1) Nasal Bone (2 bones) Forms the bridge of the nose Slide 63 Bones of the Axial Skeleton Bones of the Skull (28 total) Facial Bones 2) Maxillary bone (2 Bones) Upper jawbone that forms the central portion of the face Forms the floor of the orbits and the anterior portion of the hard palate Slide 64 Bones of the Axial Skeleton Bones of the Skull (28 total) Facial Bones 3) Zygomatic Bone (2 Bones) Forms the cheekbones and the lateral walls of the orbits Slide 65 Bones of the Axial Skeleton Bones of the Skull (28 total) Facial Bones 4) Mandible Bone (1 Bone) Lower jawbone Largest and strongest bone of the face Slide 66 Bones of the Axial Skeleton Bones of the Skull (28 total) Facial Bones 5) Lacrimal Bone (2 Bones) Forms the medial walls of the orbits Bones are paper thin Slide 67 Bones of the Axial Skeleton Bones of the Skull (28 total) Facial Bones 6) Palatine Bone (2 Bones) Forms posterior