Bones2 Flashcards
5 functions of bone
- Support
- Protection
- Movement
- Mineral and growth factor storage
- Blood cell formation
- fat storage
- hormone production
3 types of cartilage and their locations
- Hyaline cartilage: costal cartilages
- Elastic Cartilage: epiglottis
- Fibrocartilage: pubic symphysis
4 classifications of bone and examples of each
- Long bone: femur
- Irregular bone: vertebra
- Flat bone: sternum
- Short bone: talus
Compact Bone
Smooth looking outer layer, has osteons, lamellar, canaliculi, and central canal
Spongy bone
Internal to compact bone also called trabecular bone, honey comb like, little flat prices of bone called trabeculae (little beams) in living bones the open spaces are filled with yellow or red marrow
Structure of a long bone list all parts
- Diaphysis: shaft
- Medullary cavity: center of diaphysis
- Epiphyses: ends of bone
- Articular cartilage: cartilage covering the epiphysis
- Spongy bone: porus bone tissue found at epiphyses
- Epiphyseal plate/line: where growth cartilage is at bottom of epiphyses
- Endosteum: membrane that covers the inside of bones
- Periosteum: membrane covering outside of bones
- Perforating fibers: connects periosteum to bones
- Nutrient arteries: deliver nutrients to bones
- Yellow bone marrow: found in adult medullary cavity
- Red marrow: found in epiphyses of long bones (femur and humerus)
Microscopic structure of compact bone
- Central canal: big hole in osteon
- Osteon: lamella+central canal
- Circumferential lamellae: lamellae forming outer layer of bone
- Perforating canal: verticle canal next to central canals
- Nerve,vein and artery
- Canaliculi: cracks around lacuna
- Osteocytes: bone cells in lacuna
Chemical composition of bone
Organic: bone cells and osteoid
- ostegenic cells, osteocytes, osteoblasts, osteoclasts. Osteoid=Glycoproteins,proteoglycans and collagen fibers
Inorganic: mineral salts
Calcium phosphate crystals
Endochondral ossification
A bone developes by replacing hyaline cartilage. The resulting bone is called a cartilage or endochondral bone
Except for clavicle all bones inferior to base of skull are formed by endochondral ossification
Intramembranous ossification
A bone develops from a fibrous membrane and the bone is called a membrane bone.
Forms the cranial bones and (frontal, parietal, occipital, and temporal bones) as well as clavicles. Most bones formed by this process are flat bones
How does endochondral ossification happen
- Bone collar forms around diaphysis of the hyaline cartilage model. Primary ossification center in mid diaphysis
- Cartilage in middle of diaphysis calcifies and develops cavities
- The periosteal bud invades the internal cavities and spongy bone forms
- The diaphysis elongates and a medullary cavity forms. Secondary ossification centers appear in the epiphyses
- During childhood and adolescence epiphyses ossify and the only cartilage left is in the epiphyseal plates and articular cartilage
How does intramembranous ossification happen?
- Mesenchymal cells cluster together and turn into osteoblasts. Ossification centers appear in the fibrous connective tissue membrane, osteoblasts make the first trabeculae of spongy bone.
- Osteoblasts secrete osteoid which calcifies in a few days. Osteoblasts become trapped and become osteocytes
- Bone forms in a woven manner instead of lamellae. Vascularized mesenchyme condenses on the outside of woven bone and becomes the periosteum
- Lamellar bone replaces woven bone just deep to the periosteum. The spongy bone’s vascular tissue becomes red marrow
Osteoblasts
Build bone
Osteocytes
Bone cells located in lacuna of compact bone. Maintains bone tissue
Osteoclasts
Break down bone. Look like snails
Bone growth
During infancy and youth bones lengthen by interstitial growth by growth of the cartilage of the epiphyseal plate until bone growth ends during or after puberty and the epiphyseal plate becomes the epiphyseal line
When and how does bone growth stops
At the end of adolescence chondrocytes in epiphyseal plate divided less often. The plates become thinner and thinner until they are entirely replaced by bone tissue. Longitunal bone growth ends when epiphysis and diaphysis fuse (called epiphyseal closure) only articular cartilage
When does epiphyseal closure happen
18 yrs in females, 21 in males
Bone remodeling
Also called Appositional growth. Is regulated by hormones and stress on the bone. Osteocytes detect stress osteoblasts secrete osteoid on one side of the bone which becomes calcified while on the other side osteoclasts reabsorb bone. Remodeling goes on through out life
Types of fractures
- Comminuted
- Compression
- Spiral
- Epiphyseal
- Depressed
- Greenstick
Comminuted fracture
- bone fragments into 3-4 pieces. Common in aged and brittle boned people
Compression fracture
- Bone is crushed
- Common in porous bones subjected to extreme trauma, such as a fall
Spiral Fracture
- ragged break occurs when excessive twisting forces are applied to a bone
- common sports fracture
Epiphyseal fracture
- Epiphysis and diaphysis separate at epiphyseal plate
- occurs where cartilage cells are dying and matrix is calcifying
Depressed fracture
- Broken bone portion is pushed inward
- typical of skull fracture
Greenstick fracture
- Bone breaks only part way like a green twig. Other side bends
- common in children whose bones are more flexible and contain organic matrix
Repair of fractures
- A hematoma forms
- Fibrocartilage callus forms
- Bony callus forms
- Bone remodeling occurs
Fracture classification
- position of the bone ends after fracture (non displaced and displaced fractures)
- completeness of break. If broke is broken through (complete fracture) if not (incomplete fracture)
- wether bone ends penetrate skin if fracture does it is a compound/ open fracture if not it is a simple/ closed fracture
Treatment of a fracture
- Reduction: put back in place
- in closed reduction bone is popped back in place
- in open reduction the bone is surgically put together with pins or wires.
- After a broken bone is reduced it is immobilized by a cast or traction to allow healing
Osteomalacia
Means soft bones. Includes a number of disorders in which bones are poorly mineralized. Osteoid is produced but mineral salts are not adequately deposited resulting in soft weak bones. It is called rickets in children. Causes pain on weight bearing bones. Results in bowed legs and other deformities in children. Caused by insufficient calcium or vitamin D in diet
Osteoporosis
Occurs most often in post menopausal women. Caucasian and Asians are affected more. Sex hormones keep osteoporosis at bay.
Risk factor for osteoporosis:
- petite frame
- not enough weight bearing exercise
- a diet poor in calcium and protein
- abnormal vitamin D receptors
- smoking
- hormone related conditions
Osteoporosis can occur at any age due to mobility, men can get osteoporosis when they have prostate cancer
Treatment of osteoporosis
- calcium and vitamin D supplements
- weight bearing exercise
- hormone replacement therapy ( can cause cancer, soy products)
- new drugs
Preventing osteoporosis
- get enough calcium while bones are increasing density
- carbonated and alcohol leaches minerals from bones, avoid said products
- plenty of weight bearing exercise throughout life
Osteogenesis imperfecta
A genetic condition present at birth. Body can’t make normal collagen. Leading to brittle bones, victims have frequent fractures and are usually short in stature
Hormonal regulation of bone growth
Epiphyseal plate growth is influenced by growth hormone released by the pituitary gland and moderated by thyroid hormones (proper proportions) At puberty sex hormones take over, spur growth then cause epiphyseal closure. Excess or deficits of hormone can cause abnormal growth
Achondroplasia
A congenital condition in which cartilage and endochondral bone growth are defective. The cartilaginous bones are short and membrane bones are normal size. A type of dwarfism
Bony spur
Abnormal projection from a bone due to bony overgrowth; common in aging bones.
Osteoaliga
Pain in bones
Osteitis
Inflammation of bony tissue