Medical Physics Lecture 2: Forces on and in the Body

Gravitational force, Electrical force, Nuclear force (strong and weak)

F = m * g

Gravitational force causes the venous blood to travel against the force of gravity on its way to the heart, leading to the formation of varicose veins.

<p>Formation of varicose veins in the legs</p> Signup and view all the answers

<p>Leg muscles pump the veins to return blood to the heart, against the effects of gravity.</p> Signup and view all the answers

<p>To prevent blood from flowing backwards</p> Signup and view all the answers

<p>When veins become varicose, the leaflets of the valves no longer meet properly, and the valves do not work, allowing blood to flow backwards and enlarge even more.</p> Signup and view all the answers

<p>The two types of nuclear forces are the strong nuclear force and the weak nuclear force.</p> Signup and view all the answers

<p>The two types of problems involving forces on the body are statics (equilibrium) and dynamics (accelerated).</p> Signup and view all the answers

<p>Translational equilibrium occurs when the sum of forces in any direction is zero (ΣF = 0).</p> Signup and view all the answers

<p>Rotational equilibrium occurs when the sum of the torque about any axis is zero (Στ = 0).</p> Signup and view all the answers

<p>The three classes of levers are first class, second class, and third class levers.</p> Signup and view all the answers

<p>In a first class lever, the weight and force are on opposite sides of the fulcrum.</p> Signup and view all the answers

<p>In a second class lever, the load is between the fulcrum and the force.</p> Signup and view all the answers

<p>In a third-class lever, the force is between the fulcrum and the load.</p> Signup and view all the answers

<p>When veins become varicose, the leaflets of the valves no longer meet properly, and the valves do not work. This allows blood to flow backwards and they enlarge even more.</p> Signup and view all the answers

<p>The types of nuclear forces are the strong nuclear force and the weak nuclear force. The strong nuclear force holds the nucleus together against the repulsive forces, while the weak nuclear force is associated with electron decay from the nucleus.</p> Signup and view all the answers

<p>The two types of problems involving forces on the body are statics (equilibrium) and dynamics (accelerated).</p> Signup and view all the answers

<p>Dentistry, orthopedic surgery, rheumatology</p> Signup and view all the answers

<p>Bone has at least six functions. Two of these functions are support and locomotion.</p> Signup and view all the answers

<p>The body's muscles are attached to the bones through tendons, and the system of bones plus muscles supports the human body. This function is most obvious in the legs.</p> Signup and view all the answers

<p>Radiologists</p> Signup and view all the answers

<p>Dentistry and orthopedic surgery</p> Signup and view all the answers

<p>Problems of rheumatism/arthritis and problems diagnosed through x-ray images</p> Signup and view all the answers

<p>Collagen and Bone Mineral; Collagen: 40% weight, 60% volume; Bone Mineral: 60% weight, 40% volume</p> Signup and view all the answers

<p>Osteocytes maintain bone health; If they have a poor blood supply, they die, leading to bone death and loss of strength</p> Signup and view all the answers

<p>Radiographic Absorptiometry and Dual Energy Absorptiometry; 2-4%</p> Signup and view all the answers

<p>Osteoporosis; 1-2% per year</p> Signup and view all the answers

<p>Osteoclasts destroy about 0.5g of calcium each day; Osteoblasts build about 0.5g of calcium each day</p> Signup and view all the answers

<p>The smallest bones in the body act as levers for sound transmission; They reach full adult size before birth</p> Signup and view all the answers

<p>The primary function of the teeth is to provide nourishment; Incisors cut food, canines tear it, and molars grind it</p> Signup and view all the answers

<p>The primary function of the ribs is to form a protective cage for the heart and lungs</p> Signup and view all the answers

<p>The spinal column provides a flexible shield for the spinal cord; It protects the spinal cord</p> Signup and view all the answers

<p>The bones act as a chemical 'bank' for storing elements; The body can withdraw these chemicals as needed, such as in the case of maintaining calcium levels</p> Signup and view all the answers

<p>The skull is an extremely strong container that protects the brain, eyes, and ears</p> Signup and view all the answers

<p>Articulations are important for walking and many other body motions</p> Signup and view all the answers

<p>Compact or cortical bone and spongy or trabecular bone</p> Signup and view all the answers

<p>It cannot withstand the bending stresses that occur mostly in the central portions of long bones.</p> Signup and view all the answers

<p>The density of bone is about 1.9 g/cm3 and stays constant through life. In old age, the bone reduces in strength because it is thinner, not because it is less dense.</p> Signup and view all the answers

<p>The length of the bone changes and the strain increases linearly at first, indicating that it is proportional to the stress.</p> Signup and view all the answers

<p>Young’s modulus (Y) is the ratio of stress to strain in the initial linear portion and is calculated as Y = L * F / A * ∆L, where Y= Young’s modulus, L= Original length, F= Force, A= area, and ∆L= change in length.</p> Signup and view all the answers

<p>Viscoelasticity is the property of bone to withstand a large force for a short period of time without breaking, while the same force over a long period may fracture it.</p> Signup and view all the answers

<p>Piezoelectricity is the property of bone to generate electrical charge on its surface when it is bent, and it has been suggested that this phenomenon may be the physical stimulus for bone growth and repair.</p> Signup and view all the answers

<p>The main components are the synovial membrane, which encases the joint and retains the lubricating synovial fluid, and the articular cartilage, a smooth rubbery material that is attached to the solid bone. The roughness of the articular cartilage plays a useful role in joint lubrication by trapping some of the synovial fluid.</p> Signup and view all the answers

<p>The formula to calculate the amount of shortening when all the body weight is supported on a leg is ∆𝐿 = 𝐿 * 𝐹 / 𝐴 * 𝑌, where ∆𝐿 is the change in length, 𝐿 is the original length, 𝐹 is the force, 𝐴 is the cross-sectional area, and 𝑌 is the Young’s modulus.</p> Signup and view all the answers

<p>The shear modulus for the affected cells in the cardiovascular system is calculated as 𝑌= 𝜏 / 𝛾, where 𝑌 is the shear modulus, 𝜏 is the shear stress, and 𝛾 is the shear strain.</p> Signup and view all the answers

<p>The amount of shortening is 1.17mm.</p> Signup and view all the answers

<p>The advantages are that during compressive forces, trabecular bone provides the necessary strength with less material than compact bone, and it can absorb more energy when large forces are involved, such as in walking, running, and jumping.</p> Signup and view all the answers

<p>Absolute zero (-273.5°C)</p> Signup and view all the answers

<p>$T_F = \frac{9}{5}T_C + 32$</p> Signup and view all the answers

<p>212°F</p> Signup and view all the answers

<p>Increasing the average kinetic energy of its molecules</p> Signup and view all the answers

<p>Heat</p> Signup and view all the answers

<p>Centigrade scale</p> Signup and view all the answers

<p>Long-term preservation of blood, sperm, bone marrow, and tissues.</p> Signup and view all the answers

<p>Blood can be stored for a much longer time.</p> Signup and view all the answers

<p>There is little bleeding in the destroyed area.</p> Signup and view all the answers

<p>The destroyed tissue volume is controlled by the temperature of the cryosurgical probe.</p> Signup and view all the answers

<p>Parkinson's disease, tumors, and warts.</p> Signup and view all the answers

<p>-196°C</p> Signup and view all the answers

<p>The survival of cells after freezing is more dependent upon the cooling rate during the freezing cycle.</p> Signup and view all the answers

<p>373.15 K</p> Signup and view all the answers

<p>To help the survival of some cells.</p> Signup and view all the answers

<p>Slow cooling technique and rapid cooling technique.</p> Signup and view all the answers

<p>126°F</p> Signup and view all the answers

<p>Volume expansion of mercury or alcohol with temperature increase</p> Signup and view all the answers

<p>There is little pain sensation because low temperatures desensitize the nerves.</p> Signup and view all the answers

<p>High sensitivity and ability to measure small temperature changes</p> Signup and view all the answers

<p>-190 to 300°C</p> Signup and view all the answers

<p>By sensing the infrared energy emitted by a body</p> Signup and view all the answers

<p>To monitor the breathing rate by detecting temperature changes between inspired cool air and expired warm air</p> Signup and view all the answers

<p>Volume expansion, electrical resistance change, voltage produced by temperature difference</p> Signup and view all the answers

<p>Ability to measure temperature from a distance without contact</p> Signup and view all the answers

<p>T(K) = T(°C) + 273.15</p> Signup and view all the answers

<p>To increase the visibility of the capillary</p> Signup and view all the answers

<p>Ability to measure the temperature of individual cells</p> Signup and view all the answers

<p>The basic equation describing the radiation emitted by a body is given by the Stefan-Boltzman law, which states that W = eσT^4.</p> Signup and view all the answers

<p>The primary therapeutic effect in a heated area is an increase in metabolism resulting in vasodilation.</p> Signup and view all the answers

<p>The two methods for transferring the electromagnetic energy into the body in radio wave heating (Diathermy) are through a) placing the part of the body to be treated between two metal plate-like electrodes energized by high-frequency voltage, and b) using magnetic induction with a coil placed around the body region to be treated.</p> Signup and view all the answers

<p>The wavelength range used in Infrared (IR) radiant heating is 800-4000 nm.</p> Signup and view all the answers

<p>The primary conditions treated using conductive heating are arthritis, neuritis, sprains, strains, contusions, sinusitis, and back pain.</p> Signup and view all the answers

<p>The primary function of thermography in medical diagnosis is to detect pathologic conditions by accurately measuring the surface temperature of the body and relating it to those conditions.</p> Signup and view all the answers

<p>The net power is 140 watt when the radioactive power received from the surrounding walls (background) is 735 watt and the power radiated from a nude body is 875 watt.</p> Signup and view all the answers

<p>The total radiative power per surface area from skin at a temperature of 33°C is 0.05W cm^2.</p> Signup and view all the answers

<p>One very appealing method of obtaining a thermogram is to measure the radiation emitted from the body.</p> Signup and view all the answers

<p>The typical temperature difference that a commercial instrument used in clinical thermography can measure and record a thermogram in is 0.2°C in 2 seconds.</p> Signup and view all the answers

<p>The primary method of obtaining a thermogram in thermography is to measure the radiation emitted from the body in the infrared (IR) region and use the Stefan-Boltzman law for total radiative power per surface area.</p> Signup and view all the answers

<p>The wavelength range used in Microwave Diathermy is in the radar range, with a wavelength of 12cm.</p> Signup and view all the answers