The Skeletal System Flashcards
what does the skeletal system include?
bone and cartilage
what’s the difference between bone and cartilage?
bone is a hard, dense connective tissue that forms the adult skeleton. whereas, cartilage is a semi-rigid connective tissue that provides flexibility and smooth surfaces for movement
what is the function of the skeletal system?
- support the body
- support movement
- protect internal organs
- store and produce minerals
how do bones facilitate movement?
they serve as points of attachment for muscles
how do bones protect organs?
they cover or surround them just like in the skull or the rib cage and vertebral column
how are bones a storage for minerals?
the bone matrix is a reservoir for calcium and phosphate, which are stored for when needed in physiological processes
why is calcium significant to the skeletal system?
because it is important for muscle contraction and the control of ion flow in nervous signal transport
what does the bone marrow constitute?
the bone marrow is divided into:
Yellow marrow: has adipocytes which store triglycerides as energy
Red marrow: responsible for the production of blood cells (haematopoiesis)
how many bones are there in an adult vs in a newborn?
adult = 206
newborn = 300
list all bone classifications
long bone: humerus, ulna, femur, tibia, fibula
short bone: carpals, tarsals
Flat bones: skull, scapulae, sternum
irregular bone: vertebrae, sinus bones
sesamoid: tendons, patella
compare the diaphysis with the epiphysis
Diaphysis: tubular shaft between proximal & distal ends of the bone
composed of compact bone
has medullary cavity, which houses the yellow marrow
–
Epiphysis: wider section at each end of the bone
composed of spongey bone
has red marrow which fills the spaces of spongey bone
define endosteum
A membrane lining the inner surface of the bony wall
what is the endosteum important for?
- bone growth
- bone repair
- bone remodeling
what is metaphysis?
region whereby epiphysis meets diaphysis. and contains, the epiphyseal plate, hyaline, and cartilage in growing bone
what happens to cartilage at age 18-20?
cartilage is replaced by osseus tissue, and the epiphyseal tissue becomes and epiphyseal line
what is outer surface of bone covered with?
periosteum, contains blood vessels, nerves, lymph vessels
what is the function of periosteum?
connects tendons and ligaments
what is an articular cartilage?
thin layer of cartilage that reduces friction and absorbs shocks
how do flat bones protect the brain?
flat cranial bones contain spongey tissue on both sides of the compact bone, these two layers protect the brain, in case of fracture the brain would still be protected
what are the 3 different bone markings?
- articulation (bone-bone connection)
- holes (entry of nerves and vessels to bone)
- projections (attachment points for tendons/ligaments)
what gives bones their hardness?
hydroxyapatite, it incorporates salts such as magnesium, fluoride, and sulfate as it crystallizes/calcifies on collagen fibers
what are the types of bone cells?
- osteoblasts
- osteocytes
- osteogenic cells
- osteoclasts
what is the function of each bone cell?
osteoblast: new bone formation & growth portions and maintain concentration of matrix
osteocyte: primary cell of mature bone (most common)
osteogenic: mitotic activity and differentiate into osteoblasts
osteoclast: responsible for resorption and breakdown of bone
which cells do osteoclasts originate from?
monocytes and macrophages
what is the function of canaliculi
aids in bone cell communication and receiving nutrients
what is the difference between compact bone and spongey bone
compact bone is dense, can withstand compression, it’s strong, located in periosteum and diaphysis. structural unit is an osteon (lamellae) and osteocytes are arranged in concentric circles
spongey bone has holes, can withstand shift in weight distribution, and the holes balance to compact bone, it is also located in the red marrow protected by trabeculae. osteocytes are arranged in a lattice network (trabeculae)
what is the nutrient foramen?
small openings in the diaphysis where arteries enter
what is the role of nerves in bones?
regulating blood supply and sense pain
how do blood vessels nourish osteocytes?
blood vessels penetrate the periosteum, blood circulates in marrows, it is then collected by veins and exit to the foramina
define ossification
process of bone formation
what are the 2 osteogenic pathways?
- intramembranous ossification
- endochondral ossification
what role does the cartilage serve in ossification?
it serves as a template for bone development
why is it that cartilages do not repair themselves readily?
because cartilage is avascular, meaning there is no blood vessels supplying nutrients and removing waste
in intramembranous ossification, compact and spongey bone develop from ……………..
mesenchymal connective tissue
what bones form from intramembranous ossification
clavicles
cranial bones
flat bones
in intramembranous ossification, mesenchymal cells differentiate into …………… & …………….
capillaries & osteogenic cells
what is ossification center?
The site where bone begins to form in a specific bone or part of bone as a result of the accumulation of osteoblasts in the connective tissue
which bone cells secrete osteoids?
osteoblasts
what is osteoid?
an unmineralized organic tissue that eventually undergoes calcification and is deposited as lamellae or layers in the bone matrix
in the final stage of intramembranous ossification, osteoblasts become the ……..
periosteum, creating a protective layer of compact and spongey bone
what happens in endochondral ossification?
bone develops by replacing hyaline cartilage which serves as a template for bone development
what bones are formed in endochondral ossification?
base of skull
long bones
in endochondral ossification, mesenchymal cells differentiate into ………..
chondrocytes, cells responsible for cartilage formation
what is perichondrium?
a dense layer of fibrous connective tissue that covers the surface of most of the cartilage in the body
what is the sequence of endochondral ossification?
chondrocytes → perichondrium → periosteum → primary ossification centre → (same cycle repeats) → secondary ossification center
what is the area of growth in long bone?
epiphyseal plate
epiphyseal side, cartilage forms
diaphyseal side, cartilage ossifies
read it again
what are the zones of the epiphyseal plate?
- reserve zone: small chondrocytes, secure osseous plate to osseous tissue
- proliferation zone: slightly larger chondrocytes, makes new chondrocytes
- maturation zone/hypertrophy: larger chondrocytes, cellular division & cell maturation
- calcified matrix zone: dead due to calcification, penetrated by capillaries and osteoblasts, adds tissue to diaphysis
the rate of bone growth is controlled by _____
hormones
define appositional growth
growth of diameter of bone, which continues after length growth stops
what is bone modeling?
increasing the diameter of the medullary cavity
what is remodelling of bone?
resorption of old or damaged bone the same surface where osteoblasts lay new bone
what triggers bone remodelling?
exercise
injury
naturally occurs annually
why is it that people who exercise have thicker bones than those who are sedentary?
because lack of mechanical stress causes bone to lose mineral salts and collagen fibers, thus strength. since mechanical stress stimulates deposit of mineral salts and collagen fiber → increased density and strength
what are the most important forms of calcium
calcium phosphate & calcium carbonate
true or false
the body can’t absorb calcium without vitamin d
true
what are the dietary sources of calcium
milk, salmon, broccoli, fibrous vegetables
briefly, how is vitamin d obtained?
after exposure to uv rays from the sun, skin starts producing vitamin d
what is the significance of potassium to bone?
bone mineralization
what is the significance of magnesium to bone?
bone health and structure
what is the significance fluoride to bone?
replace functional groups in hydroxyapatite, increases density
what is the significance of omega 3 to bone?
reduce inflammation which interferes with osteoblast function
what is the role of the pituitary gland in the skeletal system?
it produces growth hormone which triggers chondrocyte proliferation in epiphyseal plate, resulting in increased length of bone
what effects does the growth hormone have on calcium?
- enhances mineralization
- stimulates osteoblastic activity
- improves density
what role does the thyroid gland have in the skeletal system?
it produces thyroxine, which promotes osteoblastic activity and bone matrix synthesis
what do the sex hormones (estrogen/testosterone) have in the skeletal system?
promote the conversion of the epiphyseal plate to epiphyseal line, thus ending longitudinal growth
which hormones affect osteoclasts?
- calcitonin
- parathyroid
describe the roles of parathyroid hormone and calcitonin in osteoclast activity
- parathyroid hormone: stimulates osteoclast proliferation, releasing calcium from bone to circulation
- calcitonin: inhibits osteoclast activity, stimulate calcium uptake by bone
what are the benefits of calcium?
- tooth health
- heart rate regulation
- contraction strength
- blood coagulation
- muscle contraction
- conduction of nerve impulses
what is the normal concentration of calcium?
10mg/dl
what is hypocalcaemia and hypercalcaemia?
- hypocalcaemia: low levels of calcium, characterized by difficulty coagulating, heart skips beat, difficulty contracting, non functional nerves, brittle bone
- hypercalcaemia: high levels of calcium characterized by underactive nervous system, lethargy, constipation, loss of apetite, coma, confusion
explain how calcium homeostasis is maintain
Cells of the parathyroid gland have plasma membrane receptors for calcium. When calcium is not binding to these receptors, the cells release PTH, which stimulates osteoclast proliferation and resorption of bone by osteoclasts. This demineralization process releases calcium into the blood. PTH promotes reabsorption of calcium from the urine by the kidneys, so that the calcium returns to the blood. Finally, PTH stimulates the synthesis of vitamin D, which in turn, stimulates calcium absorption from any digested food in the small intestine.
