first semester Flashcards
what’s the thick layer of fibrous tissue that covers all bone surfaces? explain the layer
Periosteum, it has abundant vascular supply and bunch of collagen fibers known as sharpey’s fibers extend from the periosteum into the underlying bone. The periosteum also receives rich nerve supply and is very sensitive to trauma
two forms of bone
compact and cancellous bone.
compact bone appear as solid mass while cancellous bone consist of a branching network of trabeculae.
purpose of trabeculae arrangement
trabeculae are arranged so as to provide resistance against mechanical stresses and strains
two main bone classification
Axial skeleton; consists of the elements forming central axis of the body
Appendicular skeleton; consists of bones forming the upper and lower limb girdles and extremities
general classification of bones
long bones, short bones, flat , sesamoid and irregular bones
briefly describe long bones
structure
inner structure and outer surface
what covers both articular surfaces
long bones usually have epiphyses at each end and a diaphyses, diaphyses is seperated by an epiphyseal cartilage and adjacent to diaphyses is the metaphyses. Outer part is composed of compact bone covered by periosteum and ends of long bone are composed of cancellous bone surrounded by a thin layer of compact bone. Articular surfaces of each ends are covered by hyaline cartilage. Mostly found in the limbs e.g humerous, femur, metacarpals, phelanges etc
describe short bones structure composed of what covers articular surfaces covers outer surface
they’re roughly cuboidal in shape and are composed of cancellous bone surrounded by a thin layer of compact bone. covered with periosteum and articular surfaces are covered by hyaline cartilage . mostly found in hand and foot e.g scaphoid,lunate, talus and calceneum.
describe flat bones
structure
are composed of thin inner and outer layers of compact bone, separated by a layer of cancellous bone, the diploë( sandwitch like bone). the scapular,, sternum etc
describe irregular bone
structure
composed of a thin shell of compact bone with an interior made up of cancellous bone e.g vetebrae, pelvic bone etc
sesamoid bones
structure
sesamoid bone is formed within a tendon where d tendon passes over a joint. e.g patella, tendon of flexor pollicis brevis in the thumb and flexor hallucis brevis in the big toe. functions is to reduce friction on the tendon, it can also alter the direction of pull of a tendon
bone marrow
occupies all the marrow cavity in long and short bones and the interstices of the cancellous bone in flat and irregular bone. marrow at birth is red and hemapoietic but gradually the blood forming activity lessens with age and red marrow is replaced with yellow.
bone development
two process membranous and enchondral.
membranous; bone develops directly from a connective tissue membrane. while in endochondral a cartilaginous model is first laid down and is later replaced by bone.
how clinically significant is bone development by membranous formation
the bones of the vault of the skull develop rapidly by membranous formation in the embryo, and this serves to protect the underlying developing brain. At birth, small areas of membrane persist btw bones. Its clinically important bcos it allows the bones a certain mobility, so the skull can undergo moulding during delivery
Endochondral formation
the long bonesof the limbs develops by endochondral ossification in a slow process that is not completed until age 18-20 or above. diaphyses is the center of bone formation found in the shaft and the centers at both ends are epiphyses. the cartilage is at each end(hyaline cartilage enables elongation of bone from each side) the plate that lies at each ends and diaphyses in a growing bone is the epiphyseal plate
what are responsible for the closure of the epiphyseal plate
sex hormones
in male; testosterone
in female; estrogen
Estrogen and testosterone release at puberty initiates closure of the epiphyseal plates. When bone growth is complete, the epiphyseal cartilage is replaced with bone, which joins it to the diaphyses.
periosteum and endosteum
Periosteum is the outer layer that covers the bone.
has superficial and deep layer : contain
osteoblasts, osteoclasts and osteocytes
Endosteum: is a thick layer of connective tissue that covers the spongy bone
Also contain dsame thing
whats the mechanism for increase in diameter of the bone.
The increase in diameter is called appositional growth. Osteoblasts in the periosteum form compact bone around the external bone surface. At the same time, osteoclasts in the endosteum break down bone on the internal bone surface, around the medullary cavity.
organic and inorganic components of the bones
organic comp; collagen fibre, provides toughness, elasticity and tensile strength
inorganic comp: calcium and phosphorus, provides hardness, rigidity and fragility
the organic comp is more in a childhood
Explain rickets
Rickets is a defective mineralization of the cartilage matrix in growing bones. this produce a condition in which cartilage cells continue to grow, resulting in excess cartilage and a widening of the epiphyseal plates. The poorly mineralized cartilaginous matrix and osteoid matrix are soft and they bend under the stress of bearing weight. the resulting deformity include enlarged costonchondral junction, bowing of the leg bones and bossing of the frontal bones. Deformities of the pelvis may also occur
epiphyseal plate disorder
epiphyseal plate disorders only present in children and adolescents, epiphyseal plate is a part of growing bone primarily concerned with the growth in length. Trauma, diet, infection, exercise or endocrine disorder can disturb the growth of hyaline cartilage plate, leading to deformity and loss of functions.
