BIOL 2401 Unit #2 Exam (Essays and Bonus)

Describe the steps of fracture repair.

1. Fracture hematoma formation: immediately extensive bleeding occurs, large blood clot (fracture hematoma) closes off injured vessels & leaves a fibrous meshwork in damaged area, disruption of circulation kills local osteocytes 2. Callus formation: cells of the intact endosteum & periosteum undergo rapid cycles of cell division, daughter cells migrate into fracture zone & an internal callus forms as a network of spongy bone uniting the inner edges of the fracture, an external callus of cartilage & bone encircles/stabilizes outer edges of fracture 3. Spongy bone formation: osteoblasts replace the central cartilage of the external callus w/ spongy bone, uniting broken ends, any bone fragment are resorbed/replaced, ends of fracture are now held firmly in place/can withstand normal stresses f/ muscle contractions 4. Compact bone formation: (remodeling) swelling of initial location of fracture is overtime remodeled by osteoblasts & osteoclasts that remove excess bony material from surfaces, little evidence of fracture remains, bone may be slightly thicker/stronger than normal at fracture site

Would you expect to see changes in blood levels of the hormones calcitonin and PTH as a result of vitamin D3 deficiency? Explain.

A person deficient in vitamin D3 would not be able to absorb calcium effectively f/ the digestive tract, leading to a shortage of calcium in the blood. To maintain homeostasis, the decrease in blood calcium would trigger the release of PTH. The PTH, in turn, would stimulate osteoclasts to release enough calcium from the bones to maintain proper calcium levels in the blood. Levels of calcitonin would probably decrease bc this hormone decreases blood calcium levels in the blood & would aggravate the situation caused by the vitamin D3 deficiency.

During the growth of a long bone, how is the epiphysis forced farther from the shaft?

Due to endochondral ossification, the cartilage of the epiphyses (the expanded portion of the distal end of the long bone) continues to grow & the region where the cartilage is being replaced by bone lies at the metaphysis (central shaft), the junction between the diaphysis and an epiphysis. The metaphysis is a narrow cartilaginous region also called the epiphyseal plate (separates epiphysis & diaphysis) The diaphyseal (shaft) side of the metaphysis, osteoblasts migrate upward & continually invade the cartilage and replace it w/ bone, while on the epiphyseal side, new cartilage is still being produced at the same rate by chondrocytes continually growing/dividing.

In a condition known as sunstroke, the victim appears flushed, the skin is warm and dry, and the body temperature rises dramatically. Explain these observations based on what you know concerning the role of the skin in thermoregulation.

Sweat glands secrete sweat to cool the body when it becomes warm. If body is dehydrated, sweat is no longer being produced, causing skin to be dry. Flushed skin would be due to blood being pumped to surface & dilation of blood vessels in an attempt to release heat. Arterioles in the dermis dilate so that excess heat carried by the blood can dissipate through the skin. This accounts for the skin redness. Body temp rises because sweat is not evaporating and carrying away heat.

Many lipid-soluble medications can be delivered by diffusion across the skin. This process is called transdermal administration and is commonly done by applying patches that contain the medication to the surface of the skin. These patches can be attached anywhere on the skin except the palms of the hands and the soles of the feet. Why?

The palms and soles have the highest number of eccrine sweat glands & cause the patch to not stick to the skin as well. Skin there has a thicker superficial layer (stratum corneum) and includes an extra layer (stratum lucidum) & would make absorption more difficult

Why would a physician concerned about the growth patterns of a young child request an x-ray of the hand? Explain what an x-ray is and how it will provide the information the physician wishes to assess.

There are many bones in the hand, each has an epiphyseal cartilage (plate). Measuring the width of these plates will provide clues to the hormonal control of growth in the child. The timing of endochondral ossification can be monitored by comparing the width of the epiphyseal cartilages in successive x-rays. The presence of an epiphyseal line (former location of the epiphyseal cartilage) indicates epiphyseal growth has ended. X-rays are a form of high-energy radiation that penetrates living tissue, x-ray beam travels through the body before striking a photographic plate, the body absorbs or deflects some of the x-rays, areas impenetrable by x-rays appear white & are radiopaque.

The structural features and skeletal components of the sternum make it a part of the axial skeleton, which is important in a variety of clinical situations. If you were teaching this information to prospective health care professionals, what clinical applications would you cite?

While performing CPR, you are careful to position your hands correctly to avoid damage to the xiphoid process & cause broken ribs, so the xiphoid process is used as a landmark in CPR. Damage to the bones could also injure nearby organs.

Look at CLINICAL NOTE: DIAGNOSTIC IMAGING TECHNIQUES pg 16-17. We will refer to this diagnostic tools for use with various organ systems. You will need to become familiar with each of the diagnostic tools listed and discussed on these pages.

X-Rays X-rays are a form of high-energy radiation that penetrates living tissue, x-ray beam travels through the body before striking a photographic plate, the body absorbs or deflects some of the x-rays, areas impenetrable by x-rays appear white & are radiopaque. Barium-Contrast X-Ray A radiopaque substance is introduced CT scan (computed tomography) A single x-ray rotates around the body, striking a sensor monitored by a computer, completing a revolution around the body every few seconds, then moves a short distance & repeats the process, results display as a sectional view, & show a three-dimensional relationship w/ soft tissue structures more clearly than standard x-rays Spiral CT scan MRI scan (magnetic resonance imaging) Can show soft tissue structures in greater detail than CT, surrounds parts of the body w/ a magnetic field 3000 times as strong as that of the earth, causing particles within atoms throughout the body to line up in a uniform direction, energy f/ pulses of radio waves are absorbed & released by the different atoms, the released energy creates a detailed image of the soft tissue PET scan (position emission tomography) An imaging technique that assesses metabolic & physiological activity of a structure Ultrasound A small transmitter contacting the skin broadcasts a brief, narrow burst of high-frequency sounds and detects echoes, sound waves are reflected & a picture (echogram) is assembled from the pattern of echoes Digital subtraction angiography (DSA) X-rays are taken before & then after radiopque dye is administered, & a computer subtracts details common to both images, the result being a high-contrast image showing distribution of the dye

Pott's fracture

also called bimalleolar fracture, occurs at the ankle, affects both medial malleolus of the distal tibia and lateral malleolus of distal fibula

Transverse fracture

bone breaks across its long axis

Colles fracture

break in distal portion of the radius, typically after reaching out to cushion a fall

Compression fracture

occurs in vertebra being subjected to extreme stresses

Greenstick fracture

only one side of shaft is broken, the other is bent (radius)

Spiral fracture

produced by twisting stresses that spread along the length of the bone

Displaced fracture

produces new/abnormal bone arrangements

Nondisplaced fracture

retain normal alignment of the bone or fragments

Comminuted fracture

shatter bone into multitude of fragments

Epiphyseal fracture

tends to occur where the bone matrix is undergoing calcification & chondrocytes are dying, fractures between the epiphysis and epiphyseal cartilage can permanently stop growth at site