Chapter 6: Bones and Skeletal Tissues Flashcards
Skeletal Cartilages
embryonic skeleton composed of membranes and cartilages (no bones), most of which will be ossified by age 25; all are avascular and surrounded by perichondrium
Perichondrium
dense irregular CT that contains blood vessels and all bones are surrounded by it
What are the types of skeletal cartilages?
hyaline, elastic, fibrocartilage
Hyaline Cartilage
most abundant type; fiber type: fine cartilage (invisible); includes articular cartilage, costal cartilages, respiratory cartilage, and nasal cartilages
Articular Cartilages
cover ends of most bones at moveable joints
Costal Cartilages
connect ribs to sternum
Respiratory Cartilages
association with respiratory tract
Nasal Cartilages
external nose
Elastic Cartilages
least amount of matrix between cells; fiber type: elastic; include external ear and epigolittis
Fibrocartilage
found where there is a lot of stress; a lot of fibers, fewer cells; include: knee meniscus, pubic symphysis, intervertebral discs
What are the two types of cartilage growth?
appositional growth and interstitial growth
Appositional Growth
widening from the outside; chondroblasts in perichondrium secrete new matrix on surface of existing cartilage
Interstitial Growth
chondrocytes within lacunae divide and secrete new matrix from within; widening from inside to outside
Cartilage Growth ends…
during adolescence; but some cartilages may calcify as we age
What are the functions of bones?
support, protection, skeletal muscle attachment sites, mineral storage (calcium and phosphate), hematopoiesis (red bone marrow), triglyceride (fat) storage (yellow bone marrow)
What are the bone classifications?
long bones, short bones, flat bones, irregular bones, sesamoid bones
Long Bones
longer than they are wide; all limb bones are long bones except patella, carpals, and tarsals
Short Bones
cube shaped/about as long as they as wide; carpals and tarsals
Sesamoid Bones
short bones embedded in a tendon; patella
Flat Bones
thin, flattened and usually curved; skull, ribs, sternum, scapulae, most cranial bones
Irregular Bones
complex shapes; vertebrae, hip bones, and most facial bones
Compact vs. Spongy Bone
compact: external layer, looks smooth and solid; Spongy: internal region, network of trabeculae
Structures of Long Bone
diaphysis, epiphysis, epiphyseal line, periosteum, endosteum, nutrient foramen
Diaphysis
shaft; encloses medullary cavity containing yellow marrow
Epiphysis
bone ends; capped with articulcar cartialge
Epiphyseal Line
epiphysis/disphysis junction
Periosteum
membrane attached to outerbone surface via perforating fibers; made of dense irregular CT; osteoblasts under
Endosteum
membrane covering inner bone surface, trabaculae, and canals of compact bone; osteoclasts under
Nutrient Foramen
hole in diaphysis thru which an artery, vein, and nerves enter
Structure of Short, Irregular, and Flat Bones
no diaphysis, epiphysis or medullary cavity; thin plates of spongy bone (diploe) covered with compact bone; have periosteum and endosteum
Red Bone Marrow vs. Yellow Bone Marrow
infants (<1 yr old): red bone marrow found in medullary cavity of disphysis and all spongy bone; Adults: red replaced by yellow marrow except in the spongy bone of skull, sternum, ribs, clavicle, scapula, hip bones, vertebrae, head of femur, and head of humerus (all of these still have red bone marrow)
ADDDDD BONE MARKINGS !
Osteogenic cell
stem cell; from bone cell lineage
Osteoblast
matrix syntehsizing cell; responsible for bone growth; from bone cell lineage
Osteocyte
mature bone cell; monitors and maintains the mineralized bone matrix; from bone cell lineage
Osteoclast
multinucleate; bone reabsorbing cell; large; breaks down with acid and lysosomes; from white blood cell lineage
Microscopic Structure of Compact Bone
osteon, central canal, concentric lamellae, canaliculi, performing canals, interstitial lamellae, circumferential lamellae; osteocytes within lacuna
Osteon
structured unit of compact bone; runs parallel to long axis
Central Canal
contains artery, vein and nerve
Concentric Lamellae
rings of matrix
Canaliculi
hair like canals
Performing Canals
run at 90 degree (right) angles to central canals
Circumferential Lamellae
run around entire bone deep to the periosteum
Structure of Spongy Bone
aka trabecular bone; no osteons, trabeculae have irregular arranged lamellae; osteocytes interconnected by canaliculi
Chemical Composition of Bone
organic components (35%); bone cells; osteoid; inorganic components
Organic Components of Bone
35%; allow bone to resist tension (stretching and twisting)
Osteoid
ground substance and collagen fibers secreted by osteoblasts
Inorganic Components
65%; allow bone to resist compression; hydroxypatites (mineral salts like calcium phosphate
What are the two types of bone formation (or ossification)?
endrochondral ossification and intramembranous ossification
Before week 8 bones are…
embryonic skeleton compose of hyaline cartilage and fibrous membranes
Endochondral Ossification
endochondral bone replaces hyaline cartilage; occurs in all bones below the base of the skull except clavicles (skull and clavicles not formed by endochondral ossification) ;begins in week 8; when secondary ossification is complete only hyaline cartilage found as articular cartilages and epiphyseal plate
Intramembranous Ossification
membranous bone replaces fibrous membrane; forms cranial bones and clavicals (all other bones are from cartilage and done by endochondral ossification); begins in week 8
Steps of Intramembranous Ossification
1) ossification centers develop in the fibrous connective tissue; 2) osteoid is secreted and calcified; 3) immature spongy bone and periosteum form; 4) impact bone replaces immature spongy bone
Postnatal Bone Growth
after birth; occurs during infancy and youth; involves interstitial growth and appositional growth
Interstitial Growth
increases bone length; occurs at epiphyseal plate- when the plate seals the child stops growing and the epiphysial line forms
Appositional Growth
increases bone diameter and thickness; osteoblasts add bone on external bone surface; osteoclasts remove bone on endosteal surface
Growth Hormone (GH)
stimulates epiphylial plate activity during infancy and childhood (produced by pituitary gland)
Thyroid Hormone (TH)
ensures skeleton has proper proportions during growth (produced by follicular cells of thyroid gland)
Estrogen
comes into play at puberty in both males and females; in males some testosterone is converted to estrogen; low estrogen stimulates growth spurt; high estrogen induces epiphyseal plate closure in females at ~18 yrs old and in males ~21 yrs old
Bone Remodeling
1) bone resorption, 2) bone deposition, 3) control of remodeling; includes bone resorption and deposition; occurs during interstitial and appositional growth; maintains blood calcium levels and keeps bones strong
Bone Resorption
carried out by osteoplasts
Bone Despostion
carried out by osteoblasts
Control of Remodeling
hormonal controls; determines WHEN remodeling occurs
Hormones involved with controlling remodeling
parathyroid hormone (PTH); calcitonin
Parathyroid Hormone (PTH)
produced by parathyroid glands; stimulates osteoclasts activity; when calcium is low in the blood
Calcitonin
produced by parafollicular cells of thyroid cells; has no effect on physologicla levels; no affect on blood calcium levels, unless someone is given high dose of calcitonin; at pharmacological doasges it inhibits osteoclast acitivty
Response to Mechanical Stress
muscle pull and gravity; determines WHERE remodeling occurs; bones remodel in response to demands placed on them (Wolffs Law); weight lifters have thickening at attachment sites of the most used muscle
Bone Repair and Steps of Repair
fractures are treated by reduction (realignment) and immobilization (cast or traction); Steps: 1) hematoma forms; 2) fibrocartilaginous callus forms (soft callus); 3) bony callus forms, 4) bone remodeling occurs
Inadequate Mineralization
bones soft and weak; calcium salts not adequately deposited; caused by insufficient calcium in diet or vitamin D deficiency (vit D needed to absorb calcium)
Osteomalacia
soft bones in adults; main symptoms is pain in weight bearing bones
Rickets
soft bones in children; bowed legs and deformities of pelvis, skull, and ribcage; epiphyseal plates can not calcify and continue to widen
Osteogenesis Imperfecta
brittle bone disease; genetic; abnormal collage or too little collagen produced; they can stand wrong and break a bone
Osteoporosis
bone reabsorption outpaces bone deposition; most common in postmenopausal women (lack of estrogen increases osteoclast actibity)
Risk Factors for Osteoporosis
decreased sex hormones; insufficient bone stress (weights, stress bones to make them build up); poor calcium diet, vit D or protein; smoking (lowers estrogen and calcium absorption); genetics; hormone related conditions (hyperthyroidism, diabetes); consumption of alcohol; certain medications (steroids and some cancer drugs)
Treatment for Osteoporosis
calcium and vit D supplements; load bearing exercises; HRT (hormone replacement therapy); medications such as bisphosphonates like Fosamax (inhibit osteoclasts)
Paget’s Disease
excessive and haphazard bone depostion and reapsorption; abnormally high ratio of spongy to compact bone; usually appears after age 40
Achondroplasia
congenital (from birth) and genetic; defective cartilage and endochondrum bone growth; head and trunk normal sized; arms and legs short; type of dwarfism; external fixators can be applied to lengthen femur and tibia bones
Endochondral Ossification
bone develops by replacing hyaline cartilage; takes place in all bones below the skull except for clavicles
Intramembranous Ossification
bone develops from a fibrous membrane; occurs in skull and clavicles
