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Skeletal System (Bones in the body (Flat bones (frontal, nasal, maxilla,…
Skeletal System
Bones in the body
Flat bones
frontal, nasal, maxilla, parietal, temporal, zygomatic, mandible, clavicle, ribs, scapula, sternum
Short bones
carpals, patella, tarsal, calcaneus, talus
Long bones
-Humerus
-phalanges
-radius
-ulna
-femur
-fibula
-tibia
-metatarsal
-metacarpals
Irregular bones
cervical, thoracic, lumbar, sacrum, coxal, coccyx,
bone classifications characteristics
Short bones
cube shaped
-Sesamoid bones: special type of short bone that form in tendons
-alter pull directions, reduce friction, & modify pressure
Flat bones
-are thin, flattened, & usually curved
Long bones
has a shaft plus 2 ends, all limbs except patella, wrist, ankle bones
Irregular bones
-have a complex shape
bone disorders
Rickets
-analogous disease in children
-since bones are developing rickets is much more severe
-bowed legs and deformities occur in pelvis, skull, and rib cage
Osteoporosis
-group of diseases where bone resorption out paces bone deposit
-bones become very fragile
-occurs in postmenopausal women
-affects entire skeleton
-risk factors: bone stress, decreased sex horomones, genetics, and horomone-related condition
-preventing: have an adequate diet & make sure to have a lot of calcium & vitamin D in take
osteomalacia
-number of disorders where the bone is poorly mineralized
-bones are soft and weak ; symptoms are pain where weight is present
-osteiod is produced, but calcium salts are inadequately deposited
Paget's disease
-excessive and hazardous bone deposits & resorption
-osteoclasts stop slowly, osteoblasts continue to work
-unknown cause, but a virus may trigger it
Microscopic Anatomy
spongy bone
-trabeculae in spongy bone are along lines of stress
-has irregularly arranged lamellae & osteocytes interconnected by canaliculi
no osteons
-nutrients reach through by diffusing through canciculi from capillaries in endosteum
compact bone
-osteon: structural unit of compact bone
-core of osteon is central canal which has small blood vessels & nerve fiber
-pelforating canals: connect blood & nerve supply of medullary cavity in central canal
-Canaliculi: hair-like canals come from lacunae connecting to each central canal
-Bone tissue: osteoprogenitor cells, osteblasts, osteocytes, bone lining cells, & osteoclasts
-Osteoprogenitor cells: found in periosteum & endosteum; in gowing bones they are flattened/ squamous cells
-Osteoblasts: Bone forming cells
-play role in matrix calcification
-Osteocytes: mature bone cells that occupy lacunae
-monitor and maintain bone matrix
-Bone lining cells: flat cells found on bone surfaces, where bone remodeling is not happening
-Osteoclasts: large multinuclear cells located on sites of bone resorption
bone divisions
Appendicular skeleton: bones of upper & lower limbs & girdles (shoulder & hip bones) that attach to limbs
Axial skeleton: forms long axis of body 7 includes bones of skull, vertebrae column , &rib cage
chemical composition of bones
organic components
-include osteoprogenitor cells, osteoblasts, osteocytes, bone lining cells, osteoclasts & osteoid
-collagen fibers contribute to bone structure & flexibility
tensile strength allows bones to resist stretch & twisting
-absense of trauma = bone reformation
inorganic components
balance of bone tissue (65 % by mass) has inorganic hydroxyapatites, mineral salts, & calcium phosphate - allow bones to resist compression
-mineral salts allow bones to last long after death
skeletal cartilage
made of
Elastic cartilage
-contains a lot of stretchy elastic fiber
-only found on external ear & epiglottis
Fibrocartilage
-great tensile strength, parallel rows of chondrocytes, in knee & vertebrae
Hyaline cartilage
most abundant: provides flexibility & strength
-includes articular cartilage which covers end of most movable joints
-costal carilage:connects ribs to sternum
-respiratory cartilage: from skeleton larynx
-Nasal cartilage: supports the external nose
growth of cartilage
-Appositional growth: Cartilage that surrounds perichondrium, secretes new matrix against "external force"
-Interstitial growth: lacunae-bound chondrocytes divide &secrete new matrix
*cartilage can become calcified
important functions of bones
-support: bones provide framework
-protection:skull protects brain, vertebrae surrounds spinal cord, ribs protect organs
-anchorage: bones are levers to move body - skeletal muscles attach to bones by tendons
-Mineral storage: stores minerals(calcium & phosphate)
-Blood cell formation: happens in re marrow of certain bones
-Triglyceride( fat) storage: fat, source of energy, is stored in yellow marrow in cavities of long bones
-Hormone production: Bones make osteocalcin & hormone that regulates insulin secretion, glucose homeostasis & energy
Gross Anatomy
-external bone layer is compact; internal bone is spongy bone
-spaces between trabeculare are filled with red or yellow bone marrow
structure of short, irregular, and flat bones
-shaft, ends, & membranes
-diaphysis: shaft,forms long axis;made by compact bone which covers medullary cavity (no bone tissue) & has yellow marrow
-epiphyses: bone ends; thin layer of articular cartilage covers joint surface
-membrane: periostem covers external surface of entire bone except joint surfaces
-bones are well vascularized
-Hematopoietic tissue (red marrow): all spongy bones contain red marrow
in adults red marrow has been replaced with yellow marrow in long bones
Bone marking
-distinct bone markings provide info about how bones are attached to muscles & how ligaments work together
-3 categories:
(1)projections- sites of muscles & ligaments
(2) Surfaces- form joints
(3) Depressions & opening for blood vessels & nerves
Formation of Skeleton
-endochondral ossification: bone develops by replacing hyaline cartilage produces endochondral bone
-inrtamembranous ossification: bone develops from fibrous membrane; produces membrane bone
-forms cranial bones of skull
-intramembranous ossification: form bones below the skull; more complex than intamembranous because the hyaline cartilage must be broken down first
-most bones are formed by this process are flat bone
Posthatal bone growth
Growth in length of long bones
1) Proliferation zone: cells at top compromise & divide quickly
2) Hypertonic zone: older chondrocytes become large; lacunae erode & enlarge leaving a large soace
3) Calification zone: condrocytes die, matrix detriorates, blood vessels invade
-epiphyseal plate closure: happens at 18 years old for female and 21 years old for males
-excesses or deficits of hormones result in abnormal skeleton growth
bone sutures
-coronal suture
-squamous suture
-lambdoid suture
-sagittal suture
bone sinus
-frontal sinus, ethomoidal sinus, maxillary sinus, sphenoidal sinus
Bone Remolding
-important because bones become brittle over time
-Bone resorption: osteoclasts accomplish bone resorption
-attach to bone & break down the bone
-Bone deposition: osteoblasts deposit new bone matrix
-begins at osteoid seam
-remodeling happens continuously:
-maintaining CA2+ homeostasis: hormonal negative feedback involving parathyroid horomone
-keeping bone strong: mechanical & gravitational force acting on bone to remodel; required to strengthen that bone
Hormonal controls
-without normal levels of blood calcium nerves cannot fire as needed & muscles are unable to contract
--hypocalcermia: hyperflexibility ; hypercalcermia:unable to function
-hormonal controls involve parathyroid hormone (PTH) made by parathyroid glands
-control by PTH acts to preserve blood calcium homeostasis
-calcitonin: produced by parafollicular cells of thyroid gland
fractures
treatment & repair
(1) A hematoma forms
-(2)Fibrocartilaginous callus forms
-connections broken between bone ends
-(3)Callus forms
-(4) bone remodeling occurs
Response to Mechanical Stress
-Wolf's law: bone grows/remodels in response to demand
-bony projections occur where heavy muscles are attached
structure of typical long bone
synovial joints
joint injuries