Skeletal System Skeletal Anatom y

1 Human Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, Systembones, cartilage and ligaments are tightly joined toform a strong, flexible frameworkbone is active tissue:!5-7% bone mass/weekFunctions of Skeletal System :1. Supportstrong and relatively light; 20% body weight2. Movementframework on which muscles actact as levers and pivots3. Protectionbrain, lungs, heart, reproductive system4. Mineral storage (electrolyte balance99% of body s calcium is in bone tissue(1200-1400g vs < in blood, rest in cells)also stores phosphate5. Hemopoiesisblood cell formation6.)

2 Detoxificationbone tissue removes heavy metals and other foreign materialsfrom bloodcan later release these materials more slowly for excretionbut this can also have bad consequencesHuman Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, Anatomyeach individual bone is a separate organ of theskeletal System ~270 bones (organs) of the Skeletal Systemwith age the number decreases as bones fuseby adulthood the number is 206 (typical)even this number varies due to varying numbersof minor bones:sesamoid bones small rounded bones that form withintendons in response to stresseg.

3 Kneecap (patella), in knuckleswormian bones bones that form within the sutures of skulleach Skeletal organ is composed of many kinds oftissues:bone (=osseous tissue)cartilagefibrous connective tissuesblood (in blood vessels)nervous tissueGeneral Shapes of BonesHuman Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, can be categorized according to their generalshape:1. long: cylindrical, longer than widerigid levers for muscle actions eg crowbarseg. arms, legs, fingers, toes2. short: length nearly equal widthlimited motion, gliding if anyeg. carpals, tarsals, patella3.

4 Flat: thin sheets of bone tissueenclose and protect organsbroad surfaces for muscle attachmentseg. sternum, ribs, most skull bones, scapula, os coxa4. irregular: elaborate shapes different from aboveeg. vertebrae, sphenoid, ethmoidBone Structurebones have outer shell of compact boneusually encloses more loosely organized bone tissue= spongy (=cancellous) boneHuman Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, general structure of a typical longbone:articular cartilageepiphysisperiosteummedullary cavitydiaphysisendosteumepiphysisepiphys eslarge surface area for muscle attachment and pivotspongy bone with trabeculae;contains red marrow (=hemopoietic tissues)!

5 Produces blood cells in delicate mesh of reticular tissuesin adults red marrow is limited to vertebrae, sternum, ribs, pectoral and pelvic girdles, proximal heads of humerus and femurwith age, red marrow is replaced by yellow marrowarticular cartilageon surface of epiphysesHuman Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, cushion of hyaline cartilagediaphysisthick compact bone but light; hollow ! medullary cavitymedullary cavityyellow marrow fat (adipose) storage fat at the center of a ham bone in event of severe anemia, yellow marrow cantransform back into red marrow to make blood cellsperiosteumwhite fibrous connective tissue continuous with tendonspenetrates bone welds blood vessels to boneendosteumfibrous CT that lines medullary cavityMicroscopic Structure (Histology)A.

6 Bone:connective tissue; contains cells and matrixbone cells = osteocytesmatrix predominates; ~ 1/3rd organic and 2/3rd s inorganicmatrix contains lots of collagen fibersHuman Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, organized arrangement of matrix andcellslacunae w osteocyte& canaliculilamellaehaversian canalperforating canals (Volkmann canals)interconnect the haversian canalsperiosteum provides life support System forbone cellsblood vessels penetrate bone and connect with those in haversian canalsB. cartilageresembles bone:large amount of matrixlots of collagen fibersdiffers:firm flexible gel is not calcified (hardened)no haversian canal systemno direct blood supply!

7 Nutrients and O2 by diffusionall bone starts out as cartilageHuman Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, bone the matrix is hardened (= ossified) bycalcification (or mineralization)microscopic structure of cartilage:chondrocytes in lacunaekinds of cartilage:(all similar matrix with lots of collagenfibers; differ in other fibers)1. hyalinemost commoneg. covers articular surfaces of joints, costal cartilageof ribs, rings of tracheae, nose2. fibrousmostly collagen fiberseg. discs between vertebrae, pubic symphysis3. elasticalso has elastic fiberseg.

8 External ear, eustacean tubeHuman Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, Anatomy of Skeletal SystemBone Markings: any bump, hole, ridge, etc on each bone; eg.:Foramen: opening in bone passageway for nerves and bloodvesselsFossa: shallow depression eg a socket into which another bonearticulatesSinus: internal cavity in a boneCondyle: rounded bump that articulates with another boneTuberosity: large rough bump point of attachment for muscleSpine: sharp slender processtwo main subdivisions of Skeletal System :axial : skull, vertebral column, rib cageappendicular: arms and legs and girdlesThe Axial SkeletonA.

9 Skullmost complex part of the skeletonconsists of facial and cranial bonesmost bones are paired, not allHuman Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, joined at sutures1. Fontanelsossification of skull begins in about 3rd month of fetal developmentnot completed at birth!bones have not yet fusedgaps = fontanelsfrontal (anterior)occipital (posterior)2 sphenoid2 mastoidat this stage skull is covered by tough membrane for protectionnormally, bones grow together and fuse to form solid case around brain3. Skull Cavitiesinside of skull contains several significant cavities:cranial cavity largest (adult 1,300 ml); part of dorsal body cavityorbits eye socketsnasal cavitybuccal cavitymiddle and inner ear cavities4.

10 Paranasal SinusesHuman Anatomy & Physiology: Skeletal System ; Ziser, Lecture Notes, 4 of the bones making up the facein life lined with mucous membrane to form sinuseslighten bone, warm and moisten air6 sinuses:frontal -2maxillary -2ethmoid -1sphenoid -1 Examples of Paired Skull Bones:5. Maxillacheek bones, upper teeth cemented to these boneshard palate: palatine process and palatine bonescleft palate ! when bones of palatine process of maxilla bones do not fuse properlynot only cosmetic effectcan lead to serious respiratory and feeding problems inbabies and small childrentoday, fairly easily corrected6.