Chapter 6 Flashcards
Skeletal system
- Bones of the skeleton
2.Cartilages, ligaments and other connective tissues that stabilize and connect - 99% of body’s calcium is in the skeleton
Functions of the skeleton system
- Support
- carry our tissues - Storage of minerals and lipids
- calcium, phosphate and fat (yellow bone marrow) - Blood cell production
- red bone marrow - Protection
- surrounds delicate organs - Leverage
- bones as levers muscles act on
bone shapes
- Long - long and slender (arms and legs)
- Flat - thin, curved with parallel surfaces (skull, sternum, and ribs)
- Short - small and boxy (wrist, ankle)
- Irregular - complex (vertebrae, pelvis, some skull)
- Sesamoid - patella (may be others)
- Sutural - fill in spaces between skull bones
Bone structure - three types of bones
- Compact bone (dense)
- very organized - Spongy bone (cancellous)
- many spaces like a sponge - Flat bone - spongy bone sandwiched between compact bone
Parts of the long bone
- Diaphysis - shaft
- Medullary cavity - part of diaphysis, filled with red or yellow marrow
- Epiphyses - ends (proximal & distal)
- Metaphysis - connects diaphysis to epiphysis
- Articular cartilage - covers articulating surface (joints)
Two types of Bone Marrow
- Red bone marrow
-site of blood cell production
-stem cells and immature cells
-children up to 7 all bones
-adults found some spongy bone (flat bones and some epiphyses
2.
- found in the marrow cavity of long bones
-stores fat
Osseus tissue
- Bone histology - study of bone tissue or osseous tissue
- Connective tissue with a solid matrix
-crystals of hydroxyapatite (calcium & salt ions
-collage fibers
Cells in bone
- Osteocytes = mature bone cells
- maintain matrix
- in lacunae
- connected by canaliculi - Osteoblasts = synthesize new matrix
-osteogenesis (ossification) - Osteoclasts = dissolves bone matrix
- giant cells, 50 or more nuclei
- Osteolysis - resorption of bone matrix
-must have a balance between osteoblasts and osteoclasts to maintain bone mass
Osteogenic cells
Stem cells responsible for bone repair & growth
- differentiate into osteoblasts
Structure of compact bone
- Osteon
- structural unit of compact bone - central canal with blood vessels
- lamellae - rings of bone matrix
- Lacunae - cavities holding bone cells (osteocytes)
- Canaliculi - little canals allowing for the movement of substances
- Perforating canals
- canal perpendicular to the central canal
- carries blood vessels and nerves
Characteristics of spongy bone
- contains trabeculae
- “little beams”
- no complete osteons
- contain red bone marrow
Bone stress locations
- Compact bone
- located where stresses are limited in direction - spongy bone
- located where stresses are weaker or multidirectional
-protects red bone marrow
Bone membrane: Periosteum
- double layered fibrous membrane
- covers bones
- outer layer
- tough fibrous connective tissue; tendons and ligaments attach - Inner layer
- contains osteoblasts, osteoclasts and osteoprogenitor cells; involved in bone growth, repair and remodeling
bone membrane: Endosteum
- lines cavities
- involved in growth repair & remodeling
Ossification
Converting other tissue to bone
Calcification
Depositing calcium salts within tissues
- occurs during ossification
Epiphyseal plates
Allow for growth of long bone during childhood
- new cartilage is continuously formed
- older cartilage becomes calcified; cells die
- calcified cartilage is eroded
- bone tissue forms
- ossification comes after cartilage formation
Endochondral ossification
- Cartilage model gradually replaced by bone
- Long bones of the embryonic skeleton
- Results in the diaphysis and epiphyses being separated by a plate of cartilage
- growth plate/epiphyseal plate
Longitudinal Bone Growth
- Grows in height
- Occurs at the growth plate
p Epiphyseal plate - Activity influenced by hormones
- growth hormones
- sex hormones (at puberty) - Closure: epiphyseal plate –> epiphyseal line
Intramembranous ossification
- Occurs in flat and irregular shaped bones of embryo
- Fibrous membrane –> bone
- dermal bones result (under dermal layer)
- include skull bones, mandible and clavicle - begins at ossification center
Fontanels
Soft spots of fetal skulls
Appositional growth
- growth in width
- occurs throughout life, very slow
- involves osteoblasts in periosteum and osteoclasts in endosteum
- Results in larger strong bones
Blood & nerve supply of bone
- Osseus tissue
- metabolically active
- highly vascular - nerve supply
- parallel blood vessels
Bone remodeling
- continually remodeling
- recycles and renews the organic and mineral components of the bone matrix - remodeling in response to stress and body’s needs
- exercise = mechanical stress
- causes bones to become stronger and thicker - mechanical stress (weight bearing activity) increases bone density
- nonuse = loss of bone mass
Nutritional needs of bone
- minerals: calcium, phosphate, magnesium
- Vitamin D: (calcitrol) for calcium absorption
- Vitamin C: for collagen formation
- Proper hormone levels
Hormones
- Growth hormones and thyroxine increase bone mass
- Sex hormones (estrogen & testosterone)
- Calcitonin and PTH control blood calcium levels, affect bones
Calcitonin
decreases blood calcium levels
- deposits Ca++ in bone matrix
-Maintains blood calcium levels
PTH
increases blood calcium levels
-withdraws Ca++ from bone matrix
- maintains blood calcium levels
Effects of aging on bone
- Osteopenia
- reduction of bone mass - osteoporosis
- reduction interferes with normal functions
