The final products of metabolism, excreted by the body, are called excreta, and the organs performing excretory functions are excretory. The excretory organs include the lungs, gastrointestinal tract, skin, kidneys.

Lungs - contribute to release into the environment of carbon dioxide and water in the form of vapors (about 400 ml per day).

The gastrointestinal tract secretes a small amount of water, bile acids, pigments, cholesterol, certain medicinal substances (when they enter the body), salts of heavy metals (iron, cadmium, manganese) and undigested remains of food in the form of feces.

The skin performs excretory function due to the presence of sweat and sebaceous glands. Sweat glands secrete sweat, which includes water, salts, urea, uric acid, creatinine and some other compounds.

The main organ of excretion is the kidneys, which excrete with the urine most of the final products of metabolism, mainly containing nitrogen (urea, ammonia, creatinine, etc.). The process of formation and excretion of urine from the body is called diuresis.

 

The purpose of the lesson: to study the features of the location and functioning of sweat glands.

The following is necessary for work: crystalline iodine, castor oil, absolute alcohol, starch, hot water (40-43 ° C), cotton wool.

 

Work progress: It is necessary to wipe dry your palm and moisten it with a next solution: crystalline iodine - 10,0; Absolute alcohol - to bring to 100,0. After evaporation of alcohol, align unevenly colored places with clean dry cotton wool. Powder the lubricated area with starch. The other hand should be lowered into hot water (40-43 ° C) and monitor the change in the color of the starch.

 

Work 1. Measuring body temperature

Thermoregulation is the process of maintaining the temperature (Т^о) of a person's body at a relatively constant level, regardless of fluctuations in ambient temperature (isothermy). Depending on the ability to regulate body temperature, all animals are divided into 3 groups: homeothermal, poikilothermal and heterotermic. Daily temperature fluctuations in body are 0.5-0.9 ° C, its maximum values are observed in 16-18 hours, the minimum - at 3-4 in the morning.

The constancy of body temperature persists in the dynamic equilibrium of chemical thermoregulation (heat formation in muscles is 60-70%, in the liver, gastrointestinal organs - 20-30%, in other organs - 10-20%) and physical processes (thermal conductivity, convection, heat radiation, evaporation). Regulation of isothermy is carried out by nervous and humoral mechanisms

The purpose of the lesson: to familiarize students with the notion of "temperature map of the human body." Experimentally prove that the temperature of the surface of the body depends on the intensity of metabolism, blood circulation and the intensity of heat transfer processes.

The following is necessary for work: testee, mercury medical thermometers, electrothermometer, alcohol, cotton wool, stopwatch.

Work progress:

1) Shake the medical thermometer and place it under the armpit for 30 seconds. Record his testimony and shake it again. Continue recording the temperature after 1; 1.5; 2; 2.5 min. etc. until the thermometer readings will be constant.

2) Having determined the temperature in the armpit, disinfect the thermometer and measure the temperature in the oral cavity.

3) In the presence of an electric thermometer, measure the temperature at various parts of the body surface: face, neck, skin of hands, in the armpit.

 

Work 2. The role of blood circulation in maintaining the temperature

The purpose of the lesson: verify the importance of blood circulation in maintaining a constant temperature.

The following is necessary for work: testee, An electrothermometer, a sphygmomanometer, or a rubber strap, a stopwatch.

Work progress:

1) The subject put his hand on the table and keeps it in a calm state, without straining the muscles. Attach on the fingertip the electrothermometer sensor and measure the initial temperature;

2) Apply a cuff from the sphygmomanometer on the testee's shoulder and inject air until the pressure reaches 180-200 mm. Hg. At this pressure in the cuff, the blood vessels of the shoulder are squeezed and blood circulation in the region of the forearm and hand is set out;

3) Within 10 min. with an interval of 1 min, register the temperature of the fingertips;

4) Release the air from the cuff (remove the strap); the blood circulation at this moment will be restored. Continue to record the temperature of the fingertips and note the time of restoring its original temperature.

  

Control questions

 

1. Ways to remove metabolic products from the body.
2. Isolation as a component of various functional systems of the body. Excretion organs. Homeostatic functions of the kidneys.
3. Nephron and glomerular filtration.
4. The mechanism of secondary urine formation.
5. Nervous and humoral regulation of kidneys.
6. The mechanism of urination. Regulation of urination.
7. Sweating.
8. Skin functions.
9. Body temperature and isothermia. Functional isotherm maintenance system.
10. Factors affecting heat generation and heat transfer.