skeletal system Flashcards
functions of bone/skeletal system
support, protect, assist in movement, mineral homeostasis, blood cell production, triglyceride storage
which minerals are bones a reservoir of?
calcium and phosphate
where specifically does blood cell production take place?
red bone marrow –> hemapoiesis
describe the medullary cavity in children vs adults
in kids, it has red bone marrow; in adults it has yellow bone marrow
Describe metaphysis
it is where the diaphysis meets the epiphysis
It contains the epiphyseal line/plate
Periosteum
- membrane that covers the outside of the bone
- outer layer = fibrous layer = dense irregular ct
- inner layer = osteogenic layer = osteoprogenitor cells (also osteoblasts + clasts)
- has perforating fibers
- super well supplied with nerves and blood vessels
endosteum
areolar connective tissue that covers the trabeculae
recipe for bone cell matrix
25% water
25% collagen fibers
50% crystalized mineral salts (mostly CaPO3)
describe the extracellular matrix of bones
- osteoid = organic part = collagen, proteoglycans (trap water), and glycoproteins
- mineral salts = inorganic = calcium phosphate and calcium carbonate
describe the calcification process
- initiated by osteoblasts
- mineral salts are layed down and crystalize on framework formed by collagen fibers
4 types of bone cells
- osteogenic = stem cells which undergo cell division to make cells that become osteoblasts
- osteoblasts = bone building cells that lay down collagen
- osteocytes = mature bone cells –> maintain bone tissue and exchange nutrients/waste with blood –> boxed in osteoblasts
- osteoclasts = release enzymes that digest the mineral component of bone matrix –> regulate blood calcium levels
what is the structural unit for compact bone? for spongy bone?
osteon and trabeculae
canaliculi
tiny canals that connect lacunae –> provide routes for nutrient and oxygen to reach osteocytes
what connects the central canals in osteons?
what are the layers of osteons called?
- perforating canals
- lamellae
3 types of lamellae
- concentric
- interstitial
- circumferential
where are trabeclui lined?
they orient themselves along stress lines
where is red bone marrow in kids? in adults?
kids: medullary cavity and all spongy bone areas
adults: spongy bone marrow of hip, ribs, sternum, skull, vertebrae, proximal epiphyses of humerus and femur
names of the 2 major blood vessels associated with bones
- periosteal arteries = supply blood to periosteum and compact bone
- epiphyseal veins = carry blood away from long bones
4 scenarios where ossification happens
- formation of bone in embryo
- growth of bones until adulthood
- remodeling of bone
- repair of fractures
2 types of bone formation during embryo development
1 intramembranous ossification
- flat bones of skull and mandible
- soft spots allow head to fit thru birth canal
- endochondral ossification
- replacement of hyaline cartilage with bone
- most bones are formed this way
Steps of intramembranous ossification
- development of ossification center
- calcification
- formation of tribeculae
- development of compact bone and periosteum
steps of endochondral ossification
- formation of bone collar around hyaline cartilage
- cavitation of hyaline within cartilage model
- invasion of internal cavities by periosteal bud and spongy bone formation
- formation of medullary cavity as ossification continues –> appearance of secondary ossification centers
- ossification of epiphysis from the secondary ossification centers
how do bones grow in length during childhood?
- growth of cartilage at epiphyseal plate
2. replacement of cartilage by bone tissue in epiphyseal plate
zones of cartilage in epiphyseal plate
Resting: attaches cartilage to bony epiphysis
Proliferating: chondrocytes divide and lay down more cartilage
Hypertrophic: chondrocytes swell and die (osteoblasts enter)
Calcified : transformation into bone
how do bones grow in thickness?
It happens on the outer surface
“appositional growth”
osteoblasts and osteocytes
Remodeling of bone
- what causes some issues with remodeling?
- ongoing –> constant replacement of old bone with new
- need balance bt osteoblasts and osteocytes
- too much osteoblast activity caused by growth hormone
- too much osteoclast activity leads to osteoporosis or rickets/osteomalasia (vit D deficiency)
3 factors affecting bone growth and remodeling
- Minerals
- Vitamins
- hormones
Minerals that affect bone growth
Lots of calcium and phosphorus
small amounts of magnesium, fluoride, and manganese
vitamins that affect bone growth
- vit A stimulates osteoblasts
- vit C is needed for collagen synthesis
- vit D increases Ca absorption from food
- vit K and B12 are needed for sythesis of bone proteins
Hormones that affect bone growth pre puberty
Kids:
Human Growth Hormone stimulates liver to produce growth factors (IGFs) for bone growth –> IGFs stimulate osteoblasts, promote cell division at epiphyseal plate, and enhance protein synthesis
Thyroid hormones stimulate osteoblasts
Insulin increases synthesis of bone proteins
Hormones that affect bone growth post puberty
Estrogen and Testosterone
- cause growth spurt at puberty
- cause changes in females (widening of pelvis)
- shuts down growth at epiphyseal plate
Parathyroid hormone, calcitriol, and calcitonin can affect bone modeling/ mineral control
Fracture types: 1. open 2. closed 3. comminuted 4. greenstick 5. impacted 6. Pott's 7 Colles' 8. Stress
- (compound) = broken ends of bone stick through skin
- (simple) = doesn’t break skin
- bone is splintered/crushed
- one side is broken and other one is bent
- one end of fractured bone is forcefully driven into other
- fracture of fibula with injury of tibial articulation
- fracture of radius where distal fragment is displaced
- series of microscopic fissures –> need bone scan
Steps of fracture repair
- Formation of fracture hematona
- blood leaks from torn ends of blood vessels and a clotted mass of blood forms around fracture - Fibrocartilage callus formation
- fibroblasts invade fracture site and make collagen fibers, bridging broken ends of bone - bony callus forms
- osteoblasts befin to produce spongy bone trabeculae joining portions of original bone fragments - bone remodeling
- compact bone replaces spongy bone
what is calcium used for in the body?
- nerve and muscle cells
- blood clotting
- enzymes need it as a cofactor
How to elevate blood calcium levels?
Parathyroid hormone (PTH) from parathyroid gland!
- PTH increases the number and activity of osteoclasts
- PTH makes kidneys decrease the loss of calcium in urine
- PTH increases the formation of calcitrol (a hormone that increases calcium absorption from food)
How to decrease blood calcium?
Calcitonin (CT) from the thyroid!
- CT decreases osteoclast activity
- not significant in humans, but effective against osteoporosis
Exercise effect on bones
- bones deposit more mineral salts and increase production of collagen fibers in response to stress
- unstressed bones lose minerals and collagen fibers
- weight training builds strong bones
2 major effects of aging on bones
- loss of bone mass
- loss of Ca in bone matrix (can lead to osteoporosis) - brittleness
- from decreased protein synthesis
bones after menopause
- sex hormones decrease which causes bone mass to decrease
- osteoclasts outdo osteoblasts
- female bones are smaller with less mass, so they’re more affected
kyphosis
curved spine from vertebrae collapsing on themselves
