Chapter 9 Lung, Kidney, Bone and Skin

Figure 9.1 The spirometer measures lung capacities and lung volumes. Because the subject cannot make the lung volume equal to zero, the spirometer cannot measure RV and FRC. Residual Volume (RV) Functional Residual Capacity (FRC) Vital Capacity (VC) Inspiratory Capacity (IC) Tidal Volume (TV) Inspiratory Reserve Volume (IRV) Expiratory Reserve Volume (ERV)

Figure 9.2 In the water sealed spirometer, expired CO 2 is removed in the soda- lime cannister.

Figure 9.3 The total body plethysmograph measures lung volume with the shutter closed and the airway resistance via a pneumotachometer with the shutter open. Airway resistance: R AW =  P L /  Q

Figure 9.4 A model for two electrode impedance plethysmography for cylindrical vessels.

Figure 9.5 A pneumotachometer measures flow from a pressure drop  P across resistance elements such as (a) a fine mesh screen or (b) capillary tubes or channels.

Kidneys Ureter Bladder Urethra Figure 9.6 The kidneys excrete urine through the ureters to the bladder, where it is voided through the urethra.

Figure 9.7 Typical dialyser. (a) indicating the counter current flow of the blood and the dialysate (b) Cross sectional view of the dialyser.

Figure 9.8 Blood from an artery flows past a membrane in the hemodialysis machine, then returns to a vein.

Figure 9.9 A simple schematic of a peritoneal dialysis system.

Figure 9.10 Dialysate weight measuring circuit.

Figure 9.10a In a dual photon absorptiometer, an X-ray source is filtered to emit at two discrete energies.

original unstretched length the elongation of the cylinder Figure 9.11 Tensile stress  on a cylindrical bar causes tensile strain . (a) (b) force the cross-sectional area the elastic (Young’s) modulus

LL L F F W A = LW Figure 9.12 Shear stress , causes shear strain . the cross-sectional area force original unstretched length change in length

Figure 9.13 Four strain gage resistances R 1, R 2, R 3, and R 4 are connected as a Wheatstone bridge. v i is the applied voltage and v o is the output voltage, which must remain ungrounded and feeds a differential amplifier. Potentiometer R x balances the bridge.

Figure 9.14 In a linear variable differential transformer, displacement of the high permeability alloy changes the output voltage.

Figure 9.15 The uniaxial tension test measures force versus elongation.

Figure 9.16 Decay of oscillation amplitude in the pendulum device permits calculation of the coefficient of friction of a joint.

Figure 9.17 The flow hygrometer measures the increase in humidity of gas flowing over the skin. Transepidermal Water Loss: K = instrument constant V = increase in the sensor output R = gas flow rate A = the skin area isolated by the measuring chamber

Figure 9.18 The closed cup hygrometer: (a) configuration of measuring cup, (b) typical sensor output curve. (a) (b) K = instrument calibration constant l = distance between the detector and the skin surface v = detector voltage t = time

Figure 9.19 The open cup hygrometer: (a) configuration of measurement cylinder, (b) typical sensor output curve. (a)(b) V and V 0 are equilibrium and initial sensor voltages K = instrument constant D = diffusion coefficient of water in air l = distance between the sensor and the end of the cylindrical chamber open to the room air

Green Red Epidermis Dermis Superficial vascular plexus Deep vascular plexus Figure 9.20 The ratio of reflected red to green light is measured in the Dermaspectrometer and erythema meter. Subcutis

(a)(b) Figure 9.21 (a) The spectrum of object light is compared with the spectrum of the light source alone to allow for differences in lighting of the object (b) Illuminating light is diffuse whereas measured light is perpendicular to the object (d/0).