Overview Flashcards
- which are large, blunt and irregular processes found only on the femur.
- They serve as attachment sites of large, powerful muscles that move the thigh
trochanters
are rounded, rough projections such as the deltoid tuberosity seen on the humerus
Tuberosities
are smaller rounded projections such as the adductor tubercle shown on the distal end of the femur.
Tubercles
is a prominent narrow ridge of bone as exemplified by the iliac crest which is the structure we rest our hands on when we put them on our hips.
crest
a small, narrow ridge of bone, and a spine is a sharp, slender often pointed projection.
line
The ___ of a ____ is an expansion carried on a narrow neck;
the head of the bone
is a smooth, nearly flat articular surface
facet
a rounded protuberance at the end of a bone (articular projection).
condyle
is an armlike bar of bone that runs in a different direction from the main body of the bone. Examples are found on the mandible and the pubic bones.
ramus
is a canal-like passageway such as the external auditory ___
meatus
is a cavity within a bone filled with air and line with mucous membrane.
sinus
is a slit-like opening, and a foramen is a round or oval opening through a bone.
fissure
a shallow depression in which a structure like an organ or muscle may sit is called a __
fossa
- is dense and looks smooth;
- it is found on the outer part of all bones.
compact bone
- composed of small, needle-like pieces of bone (referred to as spicules) or thin, flat plates of bone called lamellae.
- also has space between the spicules.
spongy bone
- are longer than they are wide.
- They can range greatly in length.
- have three major parts, the diaphysis, epiphysis and metaphysis.
- For example, the femur is a __ ___ and has the distinction of being the largest bone in the body; but the phalanges of the fingers and toes are also __ ___.
long bones
- roughly cube-shaped meaning that their width and length are somewhat equal.
- They are made up mainly of spongy bone except on the surface.
- Examples include the eight carpal bones that make up the wrist.
short bones
- are thin and consist of two parallel plates of compact bone with spongy bone sandwiched in the middle.
- The main functions include protection.
- They also provide a large surface for attachment of muscles.
- Examples include the cranial bones, sternum and scapula.
flat bones
- have complex shapes and can’t be easily classified.
- They possess varying amounts of compact and spongy bone.
- Examples include the vertebrae and facial bones.
irregular bones
- makes up most of the bone’s length; it is covered and protected by periosteum (dense irregular CT).
- In addition, the diaphysis is made up mostly of compact bone surrounding a central marrow cavity.
- The contents of the cavity is referred to as yellow marrow because it is filled with adipose tissue which, in the fresh state, appears yellowish.
diaphysis
- are found making up both ends of the long bone.
- The part of the __ that is found in a joint is covered by a thin layer of hyaline cartilage called the articular cartilage.
- The spongy bone in the ___ contains red marrow and is the site of blood cell formation or hemopoiesis in adults.
epiphyses
connects the epiphysis to the diaphysis.
The metaphysis
- This is an anterior view of the humerus. The proximal half of the long bone was cut away longitudinally. Notice that there is a thin line of bony tissue in the epiphysis. This structure is called the ____
- It is the remnant of the epiphyseal plate, a flat piece of hyaline cartilage seen in young, growing bones. In addition, a small pie-shaped piece was removed from the proximal epiphysis and is magnified in figure b to show the structure of compact and spongy bone. The picture in the lower right is through the diaphysis. It shows mainly compact bone, yellow marrow, and the periosteum which brings blood vessels to the bone.
epiphyseal line
Some bones are not classified by shape, but instead are classified based on their location. For example, ___ or ____ ___ are found within the sutures of some cranial bones. There is a lot of individual variation in these bones. Some people don’t have any and others can have 1, 2 , 3 or more. There is no clinical significance to the number or presence or absence of sutural bones. Instead, it is related to how these bones develop.
sutural or Wormian bones
- are sesame seed-shaped bones that are found in a few tendons that pass over a joint. T
- hey are found in the hand especially metacarpophalangeal joint of the thumb, the foot at the first metatarsophalangeal joint of the great toe, and the knee.
- They protect the tendon by holding it farther away from the joint. This also modifies the mechanical effect of the muscle and reduces friction.
- can alter the direction of a muscle pull across the joint.
Sesamoid bones
- Like all connective tissues, osseous tissue consists of cells, fibers and ground substance. Together the ground substance and fibers are called the___
- Cells account for only 2% of the mass of bone. Collagen fibers give bone its strength and account for about 33% of bone mass.
matrix
- ___ (bone cell) are mature bone cells.
- They cannot divide or secrete bone matrix.
- They sit in spaces called lacunae and form connections with other ____ via small channels in the bone called canaliculi.
- The ___ in an osteon are connected to each other through gap junctions which permit the passage of materials between the bloodstream and the cells.
- Diffusion doesn’t work in a mineralized matrix.
- The function is to maintain the integrity of the protein and minerals of bone.
Osteocytes
- The second type of cell is called an ___
- These are immature bone cells that cannot divide, but they secrete unossified bone matrix called osteoid.
- Once they are surrounded by ossified bone matrix, they become mature bone cells or osteocytes.
- are found in the inner layers of periosteum and endosteum.
osteoblast
- are bone stem cells that give rise to osteoblasts when new bone is needed.
- They have the ability to divide and are important in repairing fractures.
Osteoprogenitors
- (bone break) are large cells containng over 50 nuclei. T
- hey were formed by the fusion of blood monocytes and tissue macrophages.
- Their job is to “dissolve” bone matrix.
- They play an important role in bone remodeling and turnover.
Osteoclasts
- the ground substance is made up of chondroitin sulfate and has been hardened by the infiltration of calcium salts collectively referred to as ___
- The mineralized ground substance accounts for 2/3 or 66% of the bone mass. It makes bone hard so it can carry out its function of supporting the body, but mineralization also makes bone inflexible and brittle.
hydroxyapatite
- The anatomical and functional unit of compact bone is the__ or the __ __
- Each ___ is comprised of concentric rings or lamellae of bone surrounding a central canal.
osteon or Haversian system
- Each osteon is comprised of concentric rings or lamellae of bone surrounding a __ ___
- containing the blood supply and nerves, run parallel to the surface of the bone.
central canal
- run perpendicular to the surface, penetrate the compact bone and supply blood to deeper osteons.
- Bone is highly vascularized because its mineralized matrix prevents diffusion.
Perforating canals
- As previously stated, osseous tissue must be highly ___ because the calcified bone matrix makes diffusion impossible. This is particularly true for compact bone. The diagram of the long bone above shows how blood vessels enter and leave a bone. The periosteal vessels gain entrance to superficial osteons. The nutrient artery and vein bring blood into the inner regions and the marrow cavity. From these sources, small vessels as well as nerves enter the central canals of the osteons of compact bone. Arteries bring oxygenated nutrient rich blood to the osteons and these materials are conveyed via the gap junctions that connect the osteocytes of an osteon. Carbon dioxide and other metabolic wastes generated by cellular metabolism flow in the opposite direction in the osteon, that is from the outer lamellae toward the vein in the central canal.
vascularized
All osseous tissue is dynamic and ever changing in response to many stimuli. Compact bone, in particular, thickens along lines of stress. Weight bearing exercise, pulling of muscle on bone, results in thickening of the bone in the regions of tendon attachment. In addition, long bones like the femur are subjected to bending stress from supporting the weight of the body. Body weight transmitted to the head of the femur threatens to bend the bone along the arc shown by the dashed line in the picture above. The bending compresses the bone on one side (indicated by the two red converging arrows), and stretches it on the other side (shown as blue diverging arrows). Because these two forces cancel each other internally, much less bone material is need internally than superficially. Thus, the shaft of the femur can withstand 10-15 times the body’s weight. Osteons run parallel to the long axis of the shaft. Bones are broken from a lateral impact to the shaft (perpendicular to the osteons).
…
- The terms spongy bone, trabecular and cancellous bone all refer to the same type of osseous tissue.
- The lamellae of spongy bone are not arranged in osteons. Instead they are arranged in bony spicules called
- These branch forming an open network.
- There is no need for blood vessels or capillaries to run through __ because of the numerous blood vessels running in between them.
- Osteocytes are still connected to one another via gap junctions, and canaliculi are still present. The presence of spongy bone reduces weight of the skeleton.
- Red marrow is found between ___ in the epiphyses of long bones, and is the site of hemopoiesis (blood cell formation).
- Yellow marrow (adipose tissue) is found between the___ in the marrow cavity of the diaphysis.
trabeculae
- The process of bone formation is called__
- occurs in two ways; endochondral (in cartilage) and intramembranous (within membranes).
- the skeleton begins to form 6 weeks following fertilization. The skeleton of embryos is made largely of hyaline cartilage except for flat bones which develop in fibrous membranes.
- In endochondral ___ a cartilage model is made first, but by the time of birth it has been largely replaced by bone. In the picture of the chick embryo above, the parts of the skeleton that stain blue are still cartilage, where as the parts that have already ossified stain red.
ossification
- The diagram above depicts the steps occurring during __ ___ . In the first step, a bony collar forms around the hyaline cartilage model of a bone. Shortly afterward, the cartilage matrix in the center of the shaft begins to die and deteriorate. Next, blood vessels from the periosteum invade the cavities created within the bone. As ossification continues, the medullary cavity enlarges and secondary ossification centers are formed in the epiphyses. At birth, only two pieces of the original hyaline cartilage model remains; the articular cartilage which is permanent and persists throughout our lifespan, and a small band of cartilage forming the epiphyseal plates at either end of the long bone. It is the epiphyseal cartilage that facilitates growth in length of bones. This is how a 19’ long infant can grow into a 6’ 5’’ man.
endochondral ossification
- Bones grow in length because certain hormones.
- ___ __ , secreted by the pituitary gland, keeps the chondrocytes healthy, happy and dividing on the epiphyseal side of the growth cartilage, where as just a millimeter away on the diaphyseal side, the cartilage cells are swelling up and dying. The calcified cartilage matrix is ultimately eplaced by bone.
Growth hormone
This slide illustrates how bones grow in length via the ___ ___ __
Cartilage cells are dividing on the epiphyseal side and dying and being replaced by bone on the diaphyseal surface.
the epiphyseal growth cartilage
- If growth via epiphyseal cartilages was the only way bones grew, then we would have long but very skinny bones that could not support our weight. This doesn’t happen because bones also grow in width which matches their growth in length. Growth in bone width occurs by __ ___ __, or growth on the bone’s surface.
- To have this happen so that the correct proportions of the bone are maintained as it grows in both length and width requires the cooperative activities of osteoblasts which synthesize bone matrix, and osteoclasts which dissolve it. Osteoblasts in the periosteum add bone tissue to the external face of the diaphysis as osteoclasts in the endosteum remove bone from the inner face of the diaphysis wall.
appositional bone formation
- __ __ is how most flat bones are formed.
- In this type of ossification, there is NO model of cartilage. Instead ossification centers appear in fibrous connective tissue membranes. Recall that mesenchymal cells are embryonic cells that can become other types of CT cells even in the adult.
- mesenchymal cells differentiate into osteoblasts (shown in yellow above) and begin secreting osteoid. The osteoid mineralizes in a few days and the osteoblasts become entrapped in it. At this point they become mature bone cells or osteocytes. New osteoblasts begin adding to the surface of the ossified bony spicule, and the spicule gets bigger and bigger entrapping more cells.
- Next, the membrane condenses forming the periosteum, the accumulating osteoid is laid down between embryonic blood vessels, and compact bone forms on the surface of the trabeculae.
Intramembranous ossification
- The growth of the skull bones is perfectly adjusted to the growth of the brain. This is because the mechanical forces caused by the pressure generated by the expanding brain influence the activity of the osteoblasts. As brain growth slows, so does ossification.
- Babies are born with “soft spots” called ___ .
- These are spaces between the bones of the skull containing fibrous CT membranes.
- The__ allow for the brain to keep growing after birth, and are supposed to make parturition (vaginal birth) easier. Notice the raised, cone shaped areas on the skull shown by the green arrows. These are the original sites of intramembranous ossification; they are primary ossification centers.
fontanels
