2. THE MECHANISM OF THE EXCRETORY SYSTEM
Excretory System
EXCRETION is the process of eliminating waste from our body which sometimes is called defecation waste. The organs related to the elimination of waste are lungs, skin, bladder and a large intestine.
2.1 LUNG
Lung is an indispensable organ in our body. We use it for breathing. The main function of the lung is to transfer oxygen from the air into the blood system and carbon dioxide from the blood system into the air. This is done by millions of small and thin cells which are forming a sack like shape resembling a balloon. Besides respiration the lung performs other functions as well.
Our lungs are located in sides, left and right, of the chest cavity. They are soft and the ribcage is covering and protecting them. Each lung is contained in a bag surrounding the lungs. These bags are called pleura. The pleura is like 2 thin bags put together and are called inner pleura and outer pleura. The inner pleura covers the lung and the outer pleura are attached to the chest wall. There is a cavity between the 2 thin bags called the pleura cavity. A liquid in the cavity lubricates the bags and is called pleural fluid. This liquid helps the pleura to slide smoothly without friction. The pleural fluid also ensures that the inner and outer pleura will not stick together and at the same time will be hard to separate. The left lung is smaller than the right lung because we need space for out heart on this side of the chest cavity.
Mechanism of the lung
The lung is used to transfer gas and to use oxygen. When we inhale, air will be sucked into the respiratory system. The lungs contain many airways and very small sacks called alveoli. At the wall of each alveolus are many small blood vessels attached. The alveoli have a gas exchange surface. Thus, the oxygen from the air we inhale will be diffused into the red blood cells. At the same time, carbon dioxide from the red blood cells will diffused through the membrane into the alveoli. The air we inhale contains about 20 percent of oxygen, but we use only 13 percent of it for this mechanism.
Waste Elimination from the Lung
Waste in the form of water and carbon dioxide is eliminated through the lungs. Water and carbon dioxide disseminated from cells gets into blood vessels and the blood carries them to the lungs and the air sacks. Water and carbon dioxide move through our thorax and are exhaled through our mouth and nose. This process is called ‚Respiration
2.2 SKIN
Our skin is an outer tissue which wraps around our body. The area of the skin in an adult is about 3,000 square inches and its thickness is about 2 to 3 millimeter depending on the place on our body. In areas of friction such as elbows and knees, the skin is thicker than at the arms and legs.
THE STRUCTURE OF THE SKIN
Our skin can be divided into 3 primary layers, the epidermis, the dermis, and the hypodermis.
1. The epidermis is the outermost layer of the skin and is very thin. It consists of cells stacked as layers. The inner cells of the epidermis are attached to the dermis, will split away and move to replace the outer cells when those are sloughed off. The epidermis contains cells called, Melanocytes. The number of melanocytes varies from people to people according their skin color. The epidermis contains no blood vessels, nerves or glands but only the passage pores for hair, sweat and oils.
2. The dermis is the lower skin next to the epidermis but much thicker. This kind of skin is composed of collagen, elastin, small blood vessels, nerves, muscles, oil glands, sweat glands, and hair follicles.
FUNCTIONS OF SKIN
1. Protecting and covering internal organs in the body.
2. Keeping harmful chemicals and pathogens out of the body.
3. Expelling waste from our body via the sweat glands.
4. Regulating the body temperature via the small blood vessel systems and by sweat evaporation.
5. Perceiving heat, cold, or pain.
6. Producing vitamin D by transforming fat under the skin to vitamin D with the help of sunlight.
7. Oiling the hair to make it shine and strong.
HOW TO TAKE CARE OF THE SKIN
Everybody prefers to have clean, beautiful and uncontaminated as well as wrinkleless skin. The best ways to take care of our skin is:
1. Cleaning our body by
1.1 Taking a bath at least twice a day, in the morning and in the evening, to wash away all dirty from the skin.
1.2 Using soft alkaline soap to clean the body.
1.3 Cleaning the whole body thoroughly especially under the armpits, groin, foldable joints, sexual organ, fingers, toes, under the chin and behind the ears.
1.4 Using fingers or palms to rub the body while bathing not only to clean it but also to increase blood circulation.
1.5 Drying the body after bathing with a clean towel before putting on clothes.
2. Wearing clean clothes suitable for the weather and the task; for example, if it is warm, thin clothes are suitable, so the body does not overheat etc.
3. Consuming good nutritious food, especially food containing vitamin A such as fish oil, liver, butter or cheese, milk, egg yolk, gizzard, tomato, papaya and green or yellow vegetables. Vitamin A helps to moisturize the skin, hardens finger and toe nails and prevents sloughing.
4. Drinking a lot of water to freshen the skin up.
5. Getting regular exercise for better blood circulation.
6. Getting the morning sunlight and avoiding staying under strong, bright sunlight which may burn the skin.
7. Using cosmetics with care because we may get allergic to it; inflammations may occur as well. It is advisable that use of any cosmetics producing adverse reaction should be discontinued.
8. If something is wrong with the skin, we should consult a physician.
2.3 URINARY SYSTEM
URINARY ORGANS ARE:
1. Kidneys. The 2 kidneys are at the back of the abdominal hip. There are shaped like red bean seeds. The right kidney is located a little lower than the left one. They contain about 1 million kidney tubes to filter urine from blood. The kidneys are one of the important organs of the urinary system. They filter water soluble waste such as urea, minerals and water out of the blood and transform it into urine. The urine then flows through the renal pelvis, ureter, and is stored in the urinary bladders.
2. Renal Pelvis. This is a small pipe, shaped like a cone, in the proximal part of the ureter in the kidney. The lower end of the cone funnels into the
3. Ureter. These are 2 small tubes connecting each kidney and to the urinary bladders. The length of these small tubes is about 25 to 30 cm. Urine will descend through these tubes from the kidneys to the urinary bladder
4. Urinary Bladder. Urine from the kidneys will accumulate here after descending through the ureter. The urinary bladder is very elastic and can hold up to 1-liter urine. However, if it contains more than 700 cm3, it may become dangerous. When enough urine has filled the urinary bladder, we feel an urge to urinate.
5. Urethra. This is a small tube connecting the urinary bladder with the genitals. In males, the urethra travels through the penis. In females, the urethra ends just above the vagina. The urethra provides an exit for urine from the body. In human males the urethra is about 20 cm long and in human females about 4 cm.
THE PROCESS OF THE URINATION
Any process within our body produces some kinds of waste in the cells, such as urea, ammonia, uric acid, etc. The blood will circulate this waste matter to the kidneys. Most blood circulates to the small blood tubes in the kidneys in a single day. The kidneys perform as a filter separating water and waste matter from blood and excrete it into the ureter. This water and waste mixture is called urine. Whenever the urine moves into the ureter, it will frequently be squeezed to move the urine into the bladder. When there is about 200-250 cm3 of urine in the urinary bladder, it will contract and urge us to urinate. The more urine flows into the bladder, the more urging is the feeling to urinate. The urine will flow through the urethra and exit our body at the end of the urethra. About 1 – 1.5 liters of urine is excreted from our blood every day, but this varies with the quantity of water we consume. The more water we have in our body, the more frequent we urinate. On the other hand, if the water in our body is lessened, caused by excess sweating, urine excretion will be lessened as well.
HOW TO STRENGTHEN AND MAINTAIN THE EFFICIENCY OF THE URINARY SYSTEM
1. Drink at least 6 – 8 glasses of clean water a day. This will help the urinary system.
2. Avoid consuming vegetables with high content of oxalate such as, bamboo shoots, piper samentosum, Praew vegetable, Kradone vegetable etc. All these vegetables cause accumulation of calcium oxalate in the kidneys and the urinary bladder and might develop kidney or bladder stones. We should consume beef, milk, eggs and beans because of their high content of phosphate that reduces the potential of stone development in the urinary tract especially in the kidneys, the ureter, and in the urinary bladder.
3. Avoid suppressing the urge to urinate for a long time because it might cause infections within the urinary tract.
4. Consult a urologist if unusual sensations in the urinary tract occur.
Our body functions like an engine. We burn nutrients to produce energy and waste in our body. Our body needs to get rid of two kinds of the waste matter which are:
1) Toxic substances
2) Excessive and unnecessary matter
The excretory system is responsible for the expulsion of waste from our body. The waste matters may be gaseous (breath), liquid (sweat and urine) or solid (stool).
- The organ related to the excretion of solids is the large intestine (see digestive system)
- The organ related to the excretion of gases is the lung (see respiratory system)
- The organs related to the excretion of liquids are kidneys and skin.
- The organs for the excretion of urine are kidneys, ureter, urinary bladder and urethra.
- The organ for the excretion of sweat is skin which has sweat glands producing sweat and excreting waste matters.
2.4 EXCRETION FROM THE LARGE INTESTINE
Digestion ends at the point where the small intestine meets the large intestine. The large intestine is about 1.5-meter-long with a radius of about 6 centimeters. Food digested in the small intestine will be in liquid form. The function of the first part of the large intestine is to absorb water, minerals and glucose still in the food. The last part of the large intestine stores the food waste, a semi solid. The large intestine uses mucilage to lubricate the stool so it passes more easily through the large intestine. As the large intestine absorbs more and more water from the stool, the stool will harden and might become too hard to defecate, we call this obstipation or constipation. In one day about 300 – 500 cm3 of food waste will go through the large intestine and produce about 100 grams of stool.
Causes of Constipation
1. Consumption of food with insufficient fiber content
2. Consumption of strong flavored food
3. Delayed defecation
4. Consumption of large volumes of tea or coffee.
5. Smoking.
6. Stress and nervousness