Chapter 7 Skeletal System

Fracture Repair

-A bone breaks -Fracture hematoma -Fibrocartilaginous callus -Bony callus -Bone remodeling

What organs are the targets of PTH and calcitriol? [mark all correct answers] a. Kidneys b. Liver c. Small intestine d. Stomach e. Bones

A. Kidneys, C. Small Intestine, E. Bones

Long bone

Appendicular skeleton: clavicles, and bones of arm, forearm, hand, digits, thigh, leg, and foot.

Short bone

Articulate side-to-side as well as -end-to-end Found only in wrist (carpus) and ankel (tarsus)

Contained within the spongy sections of bones, marrow is responsible for blood formation.

Blood Formation

In appositional bone growth, new bone is deposited around a Central core of existing bone Small nerve Blood vessel Collection of osteoblasts

Blood vessel

Adult

Bone maintenance, no real growth in most bones Continual overturn of bone cells and bone matrix; old cells die, old matrix removed and replaced by new cells and matrix

Match the items.The task is to match the lettered items with the correct numbered items. Appearing below is a list of lettered items. Following that is a list of numbered items. Each numbered item is followed by a drop-down. Select the letter in the drop down that best matches the numbered item with the lettered alternatives. a. Thryoxine b. Sex hormones c. Glucocorticoids d. Growth hormone 1. Hormone hyposecreted in pituitary dwarfism 2. Hormone whose deficiency is responsible for stunted skeletal growth and retarded mental development 3. Hormones that cause growth spurt 4. Hormone used to treat inflammation; chronic use can cause bone loss

D A B C

Tunnels formed by new bone deposition are lined by Periosteum Osteoblasts Endosteum Bone marrow

Endosteum

Puberty

Extremely rapid growth followed by end of growth in length of long bones - final adult height reached; shoulders broaden Growth spurt at epiphyseal plates due to rising levels of sex hormones; ends when epiphyseal plates ossify into epiphyseal lines

Osteoblast

Forms new bone matrix Produces osteoid, which is followed by calcification

Appositional bone growth is a process that Replaces older bone with new bone Eliminates blood vessels from bone Forms new bone on the surface of older bone Reduces the number of osteons

Forms new bone on the surface of older bone

Mesenchymal cell

Forms original embryonic fibrous connective tissue, mesenchymal tissue Can differentiate into any type of connective tissue; cells star-shaped and connected to each other

Embryo

Initial bone formation: ossification or osteogenesis Intramembranous ossification begins at 6 weeks in cranium, mandible, clavicle; Endochondral ossification begins slightly later, in the rest of the skeleton, including the ends of the mandible and clavicles

During appositional bone growth, concentric layers of new bone that fill in the tunnel form Blood vessels Osteons Bone marrow Osteoblast

Osteons

The storage or release of buffering compounds works to aid the body in _____________.

acid-base balance

Choose all of the following that are correct regarding bone matrix. [mark all correct answers] a. Calcium salts make bone resilient. b. Collegen is the primary component of osteoid. c. Calcium and phosphate are the major minerals in bone.

b and c

Parathyroid hormone increases the renal conversion of _________________________, which secondarily works to increase calcium levels in the blood.

calcidiol to calcitriol

Transported via the blood to the liver,______________ is converted to calcidiol.

cholecalciferol

The decline in bone breakdown and increased mineralization causes blood calcium to_________ back to normal levels.

decrease

Minerals can be stored in the skeleton which acts as a reservoir, storing or releasing minerals as needed to maintain ___________________ throughout the body

electrolyte balance

Elongation of bones through endochondral ossification requires the zone of reserve cartilage where normal _________________ cartilage persists in the metaphysis.

hyaline

As a result of direct actions on the target cells of the bone and kidneys along with an indirect action on the small intestine (calcitriol), parathyroid hormone works to ___________________ blood calcium levels.

increase

When levels of blood calcium__________________, calcitonin is released from the C cells of the thyroid gland.

increase in children

This circulating calcitonin ______________________________ within minutes.

inhibits osteoclasts and stimulates osteoblasts

Inhibition of _________________ by parathyroid hormone occurs as a result of a decreased production of organic matrix.

osteoblasts

Parathyroid hormone causes an increase in the number of ________________ and greater rates of bone resorption

osteoclasts

Which of these is most important during embryonic development? a. osteogenesis b. remodeling

osteogenesis

Sunlight contacting the epidermis converts___________________ to vitamin D₃, otherwise known as cholecalciferol

7-dehydrocholesterol

Irregular bones

Any bone that doesn't fit in another category; typically has complex shape Vertebrae; hip bones, ethmoid and sphenoid of cranium, and some facial bones such as maxillary

Mechanical Functions of Skeleton

Protection: encase soft organs to protect them from trauma Support: provide rigid support for the torso and limbs Movement: bones are the levers against which muscles pull to move body parts

Fetus

Rapid growth of membrane and cartilage, followed by lengthening and thickening of bone, along with reshaping of the bone Shafts of long bones are ossified by birth, but not all short bones and epiphyses

Functions of the Marrow

Red marrow: blood cell formation Yellow marrow: fill the hollow spaces of large long bones to make them ligher

Geriatric

Reduced height as vertebrae compress; reduced bone density; osteopenia, basically an atrophy of bone results Bone-forming cells slow down, but bone-breaking cells don't

Osteoclast

Removes old matrix Digests matrix and recycles the nutrients; active when blood calcium is too low

When levels of blood calcium _________________, parathyroid hormone is released from the four nodular parathyroid glands located on the posterior thyroid

decrease

Infancy - childhood

Continuation of growth and ossification Starting closest to the torso, the proximal and then the distal epiphyses

Match the items.The task is to match the lettered items with the correct numbered items. Appearing below is a list of lettered items. Following that is a list of numbered items. a. costal cartilage b. meniscus (articular disc) c. articular capsule d. ligament e. articular cartilage 1. Attach bone to bone 2. Hyaline cartilage at a joint 3. cartilage of the rib cage 4. fibrocartilage in joints 5. connective tissue around a joint cavity

D E A B C

a. Ankle fracture b. Partial fracture; seen in children, bone bends c. Broken in two or more separate pieces d. wrist fracture e. Splintered f. Severing of toe or finger g. Broken bone out of alignment h. Break in the skin 1. Avulsion 2. Colles 3. Comminuted 4. Complete 5. Compound 6. Displaced 7. Greenstick 8. Pott

F D E C H G B A

Flat bones

Flat in cross section; contain spongy bone Certain bones of the skull, most notably the 'cranial vault' bones: frontal, parietal, temporal, and occipital, along with some of the small facial bones; ribs and sternum; scaplula is considered flat bone by some anatomists

Osteocyte

Maintains healthy bone matrix; senses stress on bones Matures from osteoblast; maintains the cell-to-cell connection seen in mesenchymal cells; these connections run through the canaliculi

Physiological Functions of Skeleton

Mineral storage: provide calcium when needed for other organs (particularly brain and heart) Acid-base balance: provide bases when the body is in acidosis, sequester (store) bases when the body is in alkalosis

New bone is deposited by cells known as Endosteum Tunnel cells Periosteum Osteoblasts

Osteoblast

Osteoprogenitor cell

Stem cell for bone; divides by mitosis to replenish cell population and supply new osteoblasts Scattered throughout mature bone tissue

Calcidiol returns to the blood once again where transport to the kidneys then allows the final conversion to ________________.

calcitriol

Now in the most active form, calcitriol acts to _______________ blood calcium by acting on three target organs: 1) small intestines 2) skeleton, and 3) kidneys.

increase

The effects on osteoclasts cause a decrease in bone resorption and a concurrent _______________ in bone deposition due to osteoblasts.

increase

The _______________ of the entire skeleton or skeletal elements utilizes the anchoring of muscles to attachment sites on the bones which then serve as levers.

movement

The skull, pelvis, ribs, vertebral column, and sternum provide _________________ to many delicate organs of the body by encasing them in hardened shell-like or caged structures.

protection

At the level of the kidney, parathyroid hormone will decrease the amount of calcium excreted by increasing_______________ from the kidney tubules.

reabsorption

The bones of the skeleton provide structure to the body and serve as a __________ to hold up the body and maintain proper positioning of some organs.

support

Mineralization of the cartilaginous walls between lacunae provides a temporary framework in the ______________________________ by which the final stages of ossification will take place.

zone of calcification

Nearer to the medullary cavity, the ______________________ is marked by an expansive production of chondrocytes that align in rows in order to replenish those undergoing calcification.

zone of cell proliferation

The _________________________ demonstrates the area where the chondrocytes die and are replaced by blood vessels and osteoblasts, which then form the final trabeculae and osteoclasts that refine the distal contours of the medullary chamber.

zone of deposition

The next layer is the ___________________________ where the existing, columnar chondrocytes enlarge and thus force the separations between lacunae to become very thin.

zone of hypertrophy