EXCRETORY SYSTEM

Excretory system

The excretory system is a passive biological system that removes excess, unnecessary materials from an organism, so as to help maintain homeostasis within the organism and prevent damage to the body. It is responsible for the elimination of the waste products of metabolism as well as other liquid and gaseous wastes, as urine and as a component of sweat and exhalation.

Excretion is the name given to the removal from the body of ( 1) the  waste products of its chemical reactions, ( 2 ) the excess water and salts taken in with the diet and ( 3 ) spent hormone.

Excretion also includes the removal of drugs or other foreign substances taken into the alimentary canal and absorbed by the blood.

Excretory organs are lungs, kidneys, liver, and skin.

The Lungs supply the body with oxygen, but they’re also excretion organs because they get rid of the carbon dioxide. They also lose a great deal of water vapor, but this loss is unavoidable and is not a method of controlling the water content of the body.

The Kidneys remove urea and other nitrogenous waste from the blood. They also expel excess water, salt, hormones, and drugs.

There are vesica felea in the liver. The yellow/green bile pigment, bilirubin, is a breakdown product of hemoglobin. Bilirubin is excretion with the bile into the small intestine and expelled with the faeces. The pigment undergoes changes in the intestine and is largely responsible for the brown color of the faeces.

Sweat consists of water, with sodium chloride and traces of urea dissolved in it. When you  sweat, you will expel these substances from your body and so, in one sense, they are being excreted. However, sweating is a response to a rise in temperature and not to a change in the blood composition. I      n this sense, therefore, skin is not an excretory organs like the lungs and kidneys.

Excretory functions

The excretory system removes metabolic and liquid toxic wastes as well as excess water from the organism, in the form of urine.

The excretory system is a passive biological system that removes excess and unnecessary materials from an organism, so as to help maintain homeostasis within the organism and prevent damage to the body.

It is responsible for the elimination of the waste products of metabolism as well as other liquid and gaseous wastes. As most healthy functioning organs produce metabolic and other wastes, the entire organism depends on the function of the system; however, only the organs specifically for the excretion process are considered a part of the excretory system.

As your body performs the many functions that it needs in order to keep itself alive, it produces wastes. These wastes are chemicals that are toxic and that if left alone would seriously hurt or even kill you.

For example, as your cells break down amino acids, they produce a dangerous toxin known as ammonia. Your liver converts the ammonia to another substance, called urea. The urea is turned into urine in the kidneys and is then carried in the ureters to the bladder.

Component organs

Skin is an excretory organ. Although regulation of body temperature causes it to produce sweat which contain urea and other waste with salts too but the secretion of any type of waste for any purpose from the body is called excretion even if it is surplus water.

Lungs

Main article: Lungs

One of the main functions of the lungs is to diffuse gaseous wastes, such as carbon dioxide, from the bloodstream as a normal part of respiration.

Kidneys

Main article: Kidneys

The kidney's primary function is the elimination of waste from the bloodstream by production of urine. They perform several homeostatic functions such as:-

1. Maintain volume of extracellular fluid
2. Maintain ionic balance in extracellular fluid
3. Maintain pH and osmotic concentration of the extracellular fluid.
4. Excrete toxic metabolic by-products such as urea, ammonia, and uric acid.

The way the kidneys do this is with nephrons. There are over 1 million nephrons in each kidney, these nephrons act as filters inside the kidneys. The kidneys filter needed materials and waste, the needed materials go back into the bloodstream, and unneeded materials becomes urine and is gotten rid of.

In some cases, excess wastes crystallize as kidney stones. They grow and can become a painful irritant that may require surgery or ultrasound treatments. Some stones are small enough to be forced into the urethra.

Ureter

The ureters are muscular ducts that propel urine from the kidneys to the urinary bladder. In the human adult, the ureters are usually 25–30 cm (10–12 in) long. In humans, the ureters arise from the renal pelvis on the medial aspect of each kidney before descending towards the bladder on the front of the psoas major muscle. The ureters cross the pelvic brim near the bifurcation of the iliac arteries (which they run over). This "pelviureteric junction" is a common site for the impaction of kidney stones (the other being the uteterovesical valve). The ureters run posteriorly on the lateral walls of the pelvis. They then curve anteriormedially to enter the bladder through the back, at the vesicoureteric junction, running within the wall of the bladder for a few centimeters. The backflow of urine is prevented by valves known as ureterovesical valves. In the female, the ureters pass through the mesometrium on the way to the bladder.

Urinary bladder

The urinary bladder is the organ that collects urine excreted by the kidneys prior to disposal by urination. It is a hollow muscular, and distensible (or elastic) organ, and sits on the pelvic floor. Urine enters the bladder via the ureters and exits via the urethra.

Embryologically, the bladder is derived from the urogenital sinus, and it is initially continuous with the allantois. In human males, the base of the bladder lies between the rectum and the pubic symphysis. It is superior to the prostate, and separated from the rectum by the rectovesical excavation. In females, the bladder sits inferior to the uterus and anterior to the vagina. It is separated from the uterus by the vesicouterine excavation. In infants and young children, the urinary bladder is in the abdomen even when empty.

Urethra

In anatomy, the (from Greek - ourethra) is a tube which connects the urinary bladder to the outside of the body. In humans, the urethra has an excretory function in both genders to pass .

Urine formation

For the production of urine, the kidneys do not simply pick waste products out of the bloodstream and send them along for final disposal. The kidneys' 2 million or more nephrons (about a million in each kidney) form urine by three precisely regulated processes: filtration, reabsorption, and secretion.

Filtration

Figure 3. Urine formation takes place in the nephron.

Urine formation begins with the process of filtration, which goes on continually in the renal corpuscles (Figure 3). As blood courses through the glomeruli, much of its fluid, containing both useful chemicals and dissolved waste materials, soaks out of the blood through the membranes (by osmosis and diffusion) where it is filtered and then flows into the Bowman's capsule. This process is called glomerular filtration. The water, waste products, salt, glucose, and other chemicals that have been filtered out of the blood are known collectively as glomerular filtrate. The glomerular filtrate consists primarily of water, excess salts (primarily Na⁺ and K⁺), glucose, and a waste product of the body called urea. Urea is formed in the body to eliminate the very toxic ammonia products that are formed in the liver from amino acids. Since humans cannot excrete ammonia, it is converted to the less dangerous urea and then filtered out of the blood. Urea is the most abundant of the waste products that must be excreted by the kidneys. The total rate of glomerular filtration (glomerular filtration rate or GFR) for the whole body (i.e., for all of the nephrons in both kidneys) is normally about 125 ml per minute. That is, about 125 ml of water and dissolved substances are filtered out of the blood per minute. The following calculations may help you visualize how enormous this volume is. The GFR per hour is:

125 ml/min X 60min/hr= 7500 ml/hr. The GFR per day is:
7500 ml/hr X 24 hr/day = 180,000 ml/day or 180 liters/day.

Now, see if you can calculate how many gallons of water we are talking about. Here are some conversion factors for you to consider: 1 quart = 960 ml, 1 liter = 1000 ml, 4 quarts. = 1 gallon. Remember to cancel units and you will have no problem. Now, what we have just calculated is the amount of water that is removed from the blood each day - about 180 liters per day. (Actually it also includes other chemicals, but the vast majority of this glomerular filtrate is water.) Imagine the size of a 2-liter bottle of soda pop. About 90 of those bottles equals 180 liters! Obviously no one ever excretes anywhere near 180 liters of urine per day! Why? Because almost all of the estimated 43 gallons of water (which is about the same as 180 liters - did you get the right answer?) that leaves the blood by glomerular filtration, the first process in urine formation, returns to the blood by the second process - reabsorption.

Reabsorption

Reabsorption, by definition, is the movement of substances out of the renal tubules back into the blood capillaries located around the tubules (called the peritubular copillaries). Substances reabsorbed are water, glucose and other nutrients, and sodium (Na⁺) and other ions. Reabsorption begins in the proximal convoluted tubules and continues in the loop of Henle, distal convoluted tubules, and collecting tubules (Figure 3). Let's discuss for a moment the three main substances that are reabsorbed back into the bloodstream. Large amounts of water - more than 178 liters per day - are reabsorbed back into the bloodstream from the proximal tubules because the physical forces acting on the water in these tubules actually push most of the water back into the blood capillaries. In other words, about 99% of the 180 liters of water that leave the blood each day by glomerular filtration returns to the blood from the proximal tubule through the process of passive reabsorption. The nutrient glucose (blood sugar) is entirely reabsorbed back into the blood from the proximal tubules. In fact, it is actively transported out of the tubules and into the peritubular capillary blood. None of this valuable nutrient is wasted by being lost in the urine. However, even when the kidneys are operating at peak efficiency, the nephrons can reabsorb only so much sugar and water. Their limitations are dramatically illustrated in cases of diabetes mellitus, a disease which causes the amount of sugar in the blood to rise far above normal. As already mentioned, in ordinary cases all the glucose that seeps out through the glomeruli into the tubules is reabsorbed into the blood. But if too much is present, the tubules reach the limit of their ability to pass the sugar back into the bloodstream, and the tubules retain some of it. It is then carried along in the urine, often providing a doctor with her first clue that a patient has diabetes mellitus. The value of urine as a diagnostic aid has been known to the world of medicine since as far back as the time of Hippocrates. Since then, examination of the urine has become a regular procedure for physicians as well as scientists. Sodium ions (Na⁺) and other ions are only partially reabsorbed from the renal tubules back into the blood. For the most part, however, sodium ions are actively transported back into blood from the tubular fluid. The amount of sodium reabsorbed varies from time to time; it depends largely on how much salt we take in from the foods that we eat. (As stated earlier, sodium is a major component of table salt, known chemically as sodium chloride.) As a person increases the amount of salt taken into the body, that person's kidneys decrease the amount of sodium reabsorption back into the blood. That is, more sodium is retained in the tubules. Therefore, the amount of salt excreted in the urine increases. The process works the other way as well. The less the salt intake, the greater the amount of sodium reabsorbed back into the blood, and the amount of salt excreted in the urine decreases.

Secretion

Now, let's describe the third important process in the formation of urine. Secretion is the process by which substances move into the distal and collecting tubules from blood in the capillaries around these tubules (Figure 3). In this respect, secretion is reabsorption in reverse. Whereas reabsorption moves substances out of the tubules and into the blood, secretion moves substances out of the blood and into the tubules where they mix with the water and other wastes and are converted into urine. These substances are secreted through either an active transport mechanism or as a result of diffusion across the membrane. Substances secreted are hydrogen ions (H+), potassium ions (K+), ammonia (NH3), and certain drugs. Kidney tubule secretion plays a crucial role in maintaining the body's acid-base balance, another example of an important body function that the kidney participates in.

Summary

In summary, three processes occurring in successive portions of the nephron accomplish the function of urine formation:

1. Filtration of water and dissolved substances out of the blood in the glomeruli and into Bowman's capsule;
2. Reabsorption of water and dissolved substances out of the kidney tubules back into the blood (note that this process prevents substances needed by the body from being lost in the urine);
3. Secretion (augmentation)of hydrogen ions (H⁺), potassium ions (K⁺), ammonia (NH₃), and certain drugs out of the blood and into the kidney tubules, where they are eventually eliminated in the urine.

http://en.wikipedia.org/wiki/Excretory_system
http://www.nsbri.org/HumanPhysSpace/focus4/ep-urine.html

RESPIRATORY SYSTEM

      All living cells need a constant supply of energy. Green plants change the sun's energy to chemical energy. In turn, the animal cells obtain nutrients from the plant's stored chemical energy. These cells then require oxygen to release the energy for their life processes. It is a chemical process takes place in the cell that use oxygen and gives out carbondıoxide is called cellular respiration.

      In the cellular respiration nutrients are broken down and energy is released. The end products of aerobic cellular respiration are energy, carbon dioxide and water.

        Food + Oxygen                                          Carbon dioxide +Water+ Energy   

    All organisms that carry on aerobic cellular respiration have the problem of obtaining oxygen from the environment and getting rid of carbon dioxide. The process by which a living organism exchanges oxygen and carbon dioxide with its environment is called respiration.

     

    The exchange of oxygen and carbon dioxide between an organism and its environment involves the passage of these gases through a boundary surface. The surface through which gas exchange takes place is called the respiratory surface. A respiratory surface must have the following characteristics:

(1)   It must be thin-walled so that diffusion across it occurs rapidly

(2)   It must be moist because the oxygen and carbon dioxide must be in solution

(3)   It must be in contact with an environmental source of oxygen

(4)   In most multicellular organisms, it must be in close contact with the system that transport dissolved materials to and from the cell of the organism.

   Gas exchange through the respiratory surface takes place by diffusion. The direction of the gas exchange is determined by the concentration gradients of the gases on each side of the respiratory surface. As oxygen is used up inside the organism's tissues, more oxygen diffuses in. When the carbon dioxide concentration builds up within the tissues, this gas diffuses out. The larger the area of the respiratory surface, the greater the amount of gas exchange that can occur over a given period of time.

     In protists and very small multicellular animals, the diffu­sion of respiratory gases can take place directly between the cells and the environment. In larger animals however, most of the body cells are not in contact with the outside environment, and. therefore, direct diffusion cannot serve as the mechanism of gas exchange. In addition, larger animals often have an outer protective layer, such as scales, feathers, or skin, that prevents any significant gas exchange. Therefore, large multicellular animals have their respiratory surfaces in specialized organs or systems.

Human Respiratory system

     The exchange of gases between the atmosphere and the blood is external respiration. This process occurs in the lungs. The exchange of gases between the blood or tissue fluid and the cells themselves is internal respiration.

External Respiration

        The organs involved in external respiration can be divided into two groups. One group includes the organs involved in the mechanics of breathing. They are the ribs, rib muscles, diaphragm, and abdominal muscles. The other group includes the passages though which air travels to get to the bloodstream. These are the nostrils, nasal passages, phar­ynx, trachea, bronchi, bronchial tubes, and air sacs.

      

The Nose and Nasal Passages

      The air enters the nose in two streams through two nostrils. From the nostrils, air enters the nasal passages. These passages lie above the mouth cavity. Long hairs at the opening of the nostrils prevent the entrance of foreign particles. The wall of the nasal passages are lined with a mucous membrane. These cells secrete mucus, a sticky fluid that trap bacteria, dust, and other particles in the air. The mucus also moistens the air. Just below the mucus membrane is a rich supply of the capillaries. As air passes through the nose, it is warmed by the blood in these capillaries. Thus, the nasal passages serve to filter, moisten, and warm inhaled air before it reaches the lung. Both the fil­tering and warming advantages are lost when you breathe through your mouth.

     

 The Trachea

       From the nasal passages, air goes through the pharynx and down the windpipe, or trachea. The upper end of the trachea is protected by a flap of cartilage. This flap is called the epiglottis. When you swallow, the epiglottis closes over the trachea. This prevents food from getting into the lungs. The upper end of the trachea holds the voice box, or larynx. This forms a lump on the outside of the neck called the Adam's apple. Vocal cords are lo­cated inside the larynx. Our vocal cords are used to make sounds. Rings of cartilage support the trachea to keep it open for the passage of air.

The trachea and its branches are lined with tiny hairs called cilia. The cilia are constantly moving. They carry inhaled dirt and foreign particles upward toward the mouth. This dirt is removed when you cough, sneeze, or clear your throat.

The Bronchi and Air Sacs

  The trachea divides at its lower end. It forms two branches called bronchi. One bronchus extends to each lung. Each bronchus divides and forms many small bronchial tubes. These divide again into even smaller bronchioles. The bronchioles end in air sacs. Each air sac is made of clusters of tiny sacs called alveoli. The walls of the alveoli, which are only one cell thick, are the respiratory surface. They are thin and moist and are surrounded by a rich network of capillaries. It is through these walls that the exchange of oxygen and carbon dioxide between blood and air occurs. It has been estimated that the lungs contain about 300 million alveoli, with a total surface area of about 70 square meters. This would be 40 times the surface area of the skin.

       Besides irritating the trachea and bronchi, smoking inter­feres with the uptake of oxygen in the air sacs. When cigarette smoke is inhaled, about one-third of the particles remain in the alveoli. Phagocytic cells called macrophages can slowly remove many of the particles. However, an excess of particles from smoking or from other sources of air pollution breaks down the walls of the air sacs and causes the formation of inelastic, scar like tissue. This greatly reduces the functional area of the respiratory surface and may lead to a disease called emphysema.

Phases of Human Respiration

In humans, respiration can be divided into four distinct phases.

1.      Breathing is the movement of air into and out of the lungs.

2.      External respiration is the exchange of oxygen and carbon dioxide between the air and the blood in the lungs.

3.      Circulation is the carrying of dissolved gases by the blood to and from the body cells.

4.      Internal respiration is the exchange of oxygen and carbon dioxide between the blood and the body cells.

Note that these stages of respiration are physical processes. They should not lie confused with cellular respiration, the chemical processes within the" cells by which nutrients are broken down and energy is released.

The Mechanics of Breathing

Do you remember the last time you ran to catch a bus or train? By the time you took your seat you probably were breathing heavily. Breathing is the movement of the air into and out of the lungs.

The lungs are spongy, air-filled sacs in the chest cavity. Breathing is caused by muscle action. The muscles are those between the ribs, and in the diaphragm and abdo­men.

The Movements of Breathing

      The lungs fill much of the body cavity from under the shoulders down to the diaphragm. This cavity is called the thoracic cavity. The lungs are covered by a double mem­brane called the pleural membrane. One membrane is attached to the surface of the lungs. The other covers the inside of the thoracic cavity. These membranes secrete a lubricating mucus. This lets the lungs slide freely in the chest during breathing.

Place your hands on the sides of your chest and take in a deep breath. This is called inspiration. Can you feel your chest cavity expand? During inspiration, three things hap­pen to expand your chest cavity:

1.      The rib muscles contract, pulling the ribs up and out.

2.      The muscles of the dome-shaped diaphragm contract. This straightens and lowers the diaphragm. This action enlarges the chest cavity from below.

3.      The abdominal muscles relax. This allows compression of the abdominal contents when the diaphragm lowers.

When the chest cavity is expanded, air pressure inside the thorax decreases. Air rushes into the lungs to equalize the pressure.

     Place your hands on your chest again and observe the changes when you force the air from your lungs. This is called expiration. During expiration four things happen to reduce the size of your chest cavity.

1.      The rib muscles relax. This allows the ribs to spring back.

2.      The diaphragm relaxes, rising to its original position.

3.      The abdominal muscles contact. This pushes the ab­dominal organs up against the diaphragm.

4.      Elastic fibers in your lungs shrink and help to force air out of the lungs.

At expiration, the decrease in size of the chest cavity increases the air pressure inside the cavity. Air rushes out of the lungs to equalize the pressure.

Control Of Breathing

    Looking at another person, count the number of inspirations for one minute. This is the res­piration rate. In humans, inspiration and expiration (the cycle) occur from 16 to 24 times a minute. The exact rate depends on physical activity, position, mood, and age. Nerves and chemicals control your breathing and the res­piration rate.

 Nerves from the lungs, diaphragm, and rib muscles lead to a respiratory control center. This center is located at the base of the brain. There are also specials structures in the aorta and several other large arteries that are sensitive to the concentrations of oxygen and carbon dioxide in the blood. These chemoreceptors send messages to the respiratory center. It controls the regular rhythm of breath­ing. The amount of carbon dioxide in the blood is detected directly by the breathing control center. If the carbon diox­ide concentration is high, the brain signals the diaphragm and rib muscles. They increase the breathing rate. This increased rate forces more carbon dioxide out through the lungs and breathing settles back to a normal rate.

        During heavy muscular exertion, lactic acid is produced as well as carbon dioxide. This increases the acidity of the blood. The increased acidity also stimulates the respiratory center of the brain and increases the rate of breathing.

      External respiration is the exchange of oxygen and carbon dioxide between the air and the blood in the lungs. After inhalation, the concentration of oxygen in the alveoli is higher than the con­centration of oxygen in the blood. Oxygen dissolves into the moist lining of the alveoli and diffuses from the region of higher concentration (the alveoli) to the region of lower con­centration (the blood). Independently, carbon dioxide diffuses in the opposite direction—out of the blood and into the al­veoli.

As the blood is pumped through the vessels of the body by the beating of the heart, oxygen-rich blood from the lungs is carried to the body tissues and oxygen-poor blood from the tissues is returned to the lungs.

Air Capacity of the Lungs

    Each time you inhale and exhale, only about 500 milliliters of air are exchanged. The maximum amount of air that you can move through your lungs is called the vital capacity. This is the total amount of air that moves through your lungs when you inhale and exhale as hard as you can. The vital capacity of the normal person is about 4,500 milliliters. A well-trained athlete may have a vital capacity of 6,500 mil­liliters.

Internal respiration

Internal respiration is the exchange of oxygen and carbon dioxide between the blood and the body cells. In the capil­laries of the body tissues, oxygen diffuses from the blood through the intercellular fluid to the body cells; carbon dioxide diffuses from the cells through the intercellular fluid into the blood. Each gas diffuses down a concentration gradi­ent, i.e., from a region of higher concentration to a region of lower concentration.

Gases can also dissolve in liquids.

This is why oxygen and carbon dioxide can be transported by the blood. The solubility of oxygen, carbon dioxide, and nitrogen varies. Temperature changes will also affect the amount of gas that can be dissolved in a liquid. Warm water will hold less dissolved gas than will cold water.

Gas Exchange In the Lungs

The pulmonary artery carries deoxygenated, dark red blood to the lungs. There it branches into an extensive network of small capillaries. These capillaries completely surround each alveolus. The air in the alveoli and the blood in the capillaries contain gases in different concentrations. Therefore, diffusion oc­curs through the thin, moist membranes of both the alveoli and capillaries. Oxygen diffuses from the air into the blood, and carbon dioxide diffuses from the blood into the air.

The Transport of Oxygen

        Oxygen is not very soluble in the plasma of blood. It is even less soluble at our body tem­perature of 37°C. Oxygen would be more soluble at lower temperatures. Remember, the erythrocytes contain a substance called hemoglobin. Most oxygen is transported from the lungs to the body tissues by the hemoglobin. Hemoglobin is a unique iron-containing protein. Its most important charac­teristic is that it combines readily with oxygen. This reaction is reversible, depend­ing on the oxygen concentration. In the lungs, where the oxy­gen concentration is high, hemoglobin (Hb) combines with oxygen (O₂) to form oxyhemoglobin (HbO₂). When the blood reaches the capillaries of the body tissues, where the oxygen concentration of the surrounding tissues is low, the oxyhemoglobin breaks down into oxygen and hemoglobin. The oxygen diffuses from the blood into the body cells, where it is used in cellular respiration.

Blood low in oxygen is a dark red or dull purple color be­cause of the hemoglobin. Blood rich in oxygen is a bright red color because of the oxyhemoglobin.

Hemoglobin has another important characteristic. The attraction of hemoglobin for oxygen decreases with an increase in acidity. During exercise, lactic acid is produced by the active muscle cells. This causes the hemoglobin to release more of its oxygen than it would normally.

The Transport of Carbon Dioxide

     Cellular respiration produces carbon dioxide. Thus the concentration of carbon dioxide is greater in the body cells than in the capillary blood. There­fore, the carbon dioxide diffuses out of the cells and into the blood. Carbon dioxide is transported by the blood to the lungs in several ways.

When carbon dioxide diffuses into the blood, it combines with water, forming carbonic acid.

                          CO₂+ H₂O——> H₂CO₃

The H₂CO₃ quickly breaks down (ionizes), forming hydrogen ions and bicarbonate ions,

                          H₂CO₃     —>      H⁺ + HCO₃^-

These reactions are speeded up by the presence of an enzyme in the red blood cells. Most of the carbon dioxide (about 70 percent) is carried in the plasma in the form of bicarbonate ions.

Some of the carbon dioxide (about 20 percent) is carried in the red blood cells as carboxy-hemoglobin.

                          CO₂ + Hb——> HbCO₂

A small amount of carbon dioxide (about 10 percent) is car­ried in solution in the plasma,

All these reactions are reversible, and in the lungs carbon dioxide is released.

Oxygen Debt

During times of great muscular activity, the cells need more oxygen than the body can supply. The lungs cannot take in oxygen fast enough, nor can the blood deliver it fast enough. When this happens, the cells switch to anaerobic respiration. This means that oxygen is not used. Instead, pyruvic acid becomes the hydrogen acceptor in the process of energy exchange. For a short period, the cells have enough energy to function and survive. The anaerobic process produces lactic acid. This collects in the tissues, causing a feeling of fatigue. A buildup of lactic acid signals the brain's respiratory center to increase the breathing rate and supply the tissues with more oxygen.

If the heavy exercise continues, lactic acid keeps build­ing up. This is called a state of oxygen debt. It continues until the heavy exercise ends. Then during a half-hour rest, some lactic acid is oxidized. Some is converted to glycogen. Carbon dioxide and excess water are excreted. The oxygen debt is paid. The body is ready for more exercise.

Environmental Effects on Breathing and Respiration

The air's temperature, moisture, oxygen, and carbon diox­ide content all influence the rate of breathing and respira­tion. Certain of these factors involve ventilation. If the air in a room is stuffy, it is likely to be too warm and moist. Very rarely is it caused by a build-up of carbon dioxide and lack of oxygen.

Carbon Monoxide

    Far too often you read of people who have died in a closed garage where an automobile engine was running. The cause of death is given as carbon monoxide poisoning. Actually, the death is not caused by poison­ing but by tissue suffocation. Carbon monoxide will not support life. Yet it combines with the hemoglobin of the blood 250 times more readily than does oxygen. As a result, the blood becomes loaded with carbon monoxide. Its oxy­gen-combining power decreases. The tissues suffer from oxygen starvation. The victim becomes light-headed. Soon paralysis sets in. Death follows from tissue suffocation.

High Altitudes

    You live at the bottom of a large ocean of air. If you were to climb a high mountain, the air pressure would become less. At this height, the molecules of nitro­gen, oxygen, and carbon dioxide are spread farther apart. You may have experienced your ears "popping" during an altitude change. Your middle ear must equalize the pres­sure,

Air and Space Travel

     When an airplane approaches an altitude of 6,000 meters , the pressure becomes so low that a pilot has difficulties in seeing and hearing. This condition is called hypoxia. It is the result of oxygen starvation of the cells. Passengers in modern airliners fly at high altitudes in pressurized cabins.

Diving

SCUBA (underwater breathing device) divers are well aware of the problems of pressure and respiration. The weight of water causes an increase in pressure as a diver descends. The air that passes into the lungs must be under a greater pressure than that of the water. This pressure means that the molecules of nitro­gen, oxygen, and carbon dioxide are closer together. The blood and tissues of a diver, then, dissolve more molecules of these gases than you have in your body now. If a diver returns too quickly to the surface, gas bubbles (mostly nitrogen) form in the tissues. These can cause pain and even death. This condition is commonly called the bends.

Diseases of the Respiratory System

The following list includes some of the common disorders of the respiratory system.

1.        Asthma: is a severe allergic reaction in which contraction of the bronchioles makes breathing difficult.

2.        Bronchitis is an inflammation of the linings of the bron­chial tubes. The passageways to the alveoli become swollen and clogged with mucus. The condition is generally marked by severe coughing and by difficulty in breathing.

3.        Emphysema is a condition in which the lungs lose their elasticity. The walls of the air sacs break down, reducing the respiratory surface. Emphysema is marked by shortness of breath.

4.        Pneumonia is a condition in which the alveoli become filled with fluid, preventing the exchange of gases in the lungs.

5.        Lung cancer is a disease in which tumors (masses of tis­sue) form in the lungs as a result of irregular and uncontrolled cell growth. Numerous studies have demonstrated a definite relationship between lung cancer and smoking.

Smokers also run a greater risk of developing bronchitis and emphysema than nonsmokers.

UAS BIOLOGI KLS XII-IPA

Uas-Gasal-Biologi-Kls-xii-ipa

DIGESTIVE SYSTEM

Digestion

DIGESTION :

For a nutrient to be used by the cells of an organism, it must pass through the cell membranes. In general, the nutrient molecules in food are too large to pass through cell mem­branes. Thus, to be used by the cells, most food molecules must be broken down into smaller, simpler forms. The process by which food molecules are broken down is called digestion.

        Digestion may occur with in the cell – intracellular digestion, as in protozoa; or outside the cell, in especial cavity, or tube such as stomach, as in most animals- extracellular digestion, after which the soluble molecules are absorbed into the cell.  The term digestion usually refers to the chemical break­down of food substances into simpler compounds. In many organisms, pieces of food are first cut, crushed, or broken into smaller particles without being changed chemically. This treatment results in the mechanical breakdown of the food. Mechanical breakdown increases the surface area of the food particles.

Chemical digestion is carried out by digestive en­zymes, which act only on the surface of food particles. Thus, mechanical breakdown prepares the food for more rapid chemical digestion by exposing more food surface to the ac­tion of the digestive enzymes. Chemical digestion, like mechanical breakdown, takes place in stages. Large molecules are broken down into smaller molecules, and these in turn are broken down into still simpler forms. The usable, simplest products of digestion are the end products of diges­tion.

Parts of digestive system:

The digestive system is made up of two groups of organs. One group of organs form the digestive tract, a long tube that carries food through your body. As food passes through the digestive tract, it is broken down. Organs of the include: the mouth, esophagus, stomach, small intestine, and large intestine. Your digestive tract is about nine meters long!

Another group of organs are accessory organs, called digestive glands, produces digestive liquids that break down the food you eat. A small tube, or duct, leads from each digestive gland into the diges­tive tract. Food is never found within the digestive glands, only within the alimentary canal-digestive tract, itself. The digestive liquids pass through the ducts into the digestive tract. Once inside, they mix with the food and help break it down. Draw the figure shows the location of several digestive glands. These include the salivary glands, pancreas, and liver. What small organ is located underneath the liver?

Cells in the lining of the walls of the alimentary canal also secrete slimy mucus, which acts as lubricant for the food mass. It also provides a coating that protects the deli­cate cells of the digestive tube from the action of acid, diges­tive enzymes, and abrasive substances in the food.

The Process in the Digestive System

The organs of the digestive system carry out several im­portant functions that enable your body to use the nutrients in food.

First, mechanical digestion is a process that breaks down food into small pieces. Where does mechanical diges­tion begin?

Second, chemical digestion is a process that chemically changes food into simpler compounds. The change is brought about by digestive enzymes. A digestive enzyme is a special protein that breaks down complex food nutrients into simpler food nutrients. For example, digestive enzymes break down proteins into amino acids.

Third, food is pushed through the digestive tract by muscular movements called peristalsis. Peristalsis occurs when muscles along the digestive tract contract and relax in a wavelike motion. Food is pushed forward ahead of the waves. Throughout its jour­ney, the food is mixed with mucus. The mucus helps the food move along smoothly.

Fourth, after food is broken down into simple nutrients, the nutrients are absorbed into the blood. Most absorption occurs in the small intestine. The blood carries the simple nutrients to all parts of the body.

Finally, undigested waste products are eliminated from the body through the anus. As you can see in Figure the anus is located at the end of the large intestine.

 

Structure and Functions of Digestive OrgansThe Mouth and Pharynx

Food enters the body through the mouth, where both mechanical breakdown and chemical digestion occur. Chunks of food are bitten off with the teeth and ground into pieces small enough to swallow. The tongue moves and shapes the foodmass in the mouth.

As food is chewed, it is mixed with saliva, which is secreted into the mouth by three pairs of salivary glands. There are actually two types of saliva produced. One is a thin, watery secretion that wets the food. The other is a thicker, mucus secretion that acts as a lubricant and causes the food particles to stick together to form a food mass, or bolus. Saliva also contains a digestive enzyme called ptyalin, or salivary amylase. This enzyme breaks down starch, which is a polysaccharide, into maltose, which is a disaccharide.

When the food has been chewed sufficiently, it is pushed by the tongue to the back of the throat, or pharynx. This initiates the automatic swallowing reflex, which forces food into the esophagus, the tube leading to the stomach. However, air as well as food passes through the pharynx. The air must pass through the voice box, or larynx, and down the trachea to the lungs. To prevent food and liquids from entering the larynx, it is au­tomatically closed off during swallowing by a flap of tissuecalled the epiglottis. At the same time, breath­ing stops momentarily, and the passageways to the nose, ears, and mouth are blocked. When a person "swallows the wrong way" and food enters the trachea, it is brought back up into the throat by violent coughing.

The Structure Of Teeth

The permanent teeth are arranged in the same way in upper and lower jaws. The two flat front teeth are called incisors. They have sharp edges for cutting food. Next to the incisors, at the corner of your lips on either side, is a large cone-shaped tooth. This tooth is called the canine. Behind the canine tooth are the premolars. There are two on either side. Next are the molars. You have three molars on either side if you have cut your wisdom teeth; if not, you have two. Premolars and molars have flat surfaces which are good for grinding and crushing. A tooth has three general areas. The part above the gum is called the crown. A narrow part at the gum line is called the neck. The rootis the part beneath the surface. The root is held in a socket in the jawbone. A fibrous periodontal membrane anchors it firmly in the jaw socket. Different kinds of teeth have differently shaped roots. Some are long and single. Some have two, three, or four projections.

The covering of the root is called cementum. It holds the tooth firmly together. The crown has a hard white covering called enamel.

If a tooth is cut lengthwise, you can see the dentine beneath the enamel and cementum. Dentine is very hard, but somewhat softer than the enamel and cementum. It forms the bulk of the tooth. The pulp cavity is in the center of the tooth. The pulp cavity contains blood vessels and nerve fibers.

Taste Buds on the Tongue

The tongue lies along the floor of the mouth, but it begins in the throat. This muscu­lar organ has several important functions.

• It helps you chew

• Your tongue helps you swallow

• The tongue is essential to speech

• Your tongue keeps the inner surface of your teeth clean

• It acts as an organ of taste.

Notice that the surface of your tongue is covered with tiny bumps. These bumps hold taste buds, which have nerve endings at their bases. When you eat, the food in your mouth touches these bumps. This stimulates the nerve endings to send "taste" messages to your brain.

There are four typesof taste buds. Each reacts to a different group of chemicals in food to produce a taste. The four tastes are sweet, sour, bitter,and salty. But the flavor of food does not come fromtaste alone. Flavor is a mixture of taste, texture,and odor

The Esophagus

The esophagus is a tube through which food passes from the pharynx to the stomach. A small mass of it (bolus) is pushed into the throat (pharynx), where it is swallowed. The epiglottis closes over the adjacent windpipe and prevents the food from going into the wrong tube. No digestion occurs in the esophagus

The movement of food downs the digestive tube by peristalsis.

the esophagus opens into the stomach, there is a ring of muscle called a sphincter. The sphincter controls the passage of food from the esophagus into the stomach. The sphincter between the esophagus and the stomach is called the cardiac sphincter. During vomiting, a wave of peristalsis passes upward—reverse peristalsis— causing the cardiac sphincter to open, and the contents of the stomach to be "thrown up."

 The Stomach

The stomach is a thick-walled, muscular sac that can expand to hold more than 2 liters of food or liquid. Food is stored temporarily in the stomach, and mechanical breakdown and chemical digestion occur there.

human  liver

The lining of the stomach contains two types of glands. Pyloric glands secrete mucus, which covers the stomach lining and protects it from being digested. Gastric glands secrete very acidic gastric juice, which has a pH of 1.5 to 2.5. This juice contains hydrochloric acid (HCl), water, and the digestive enzyme pepsin and rennin.

 Pepsin is secreted in an inactive form called pepsinogen, which is activated after it is mixed with the hydrochloric acid. Pepsin breaks down large protein molecules into shorter chains of amino acids, proteoses and peptones, called polypeptides. Complete digestion of protein will takes place in the small intestine. Pepsin is active only in acidic medium. Hydrochloric acid is useful in killing bacteria that may have been swallowed.

Rennin curdles the protein of milk, casein, and prepares it for digestion by pepsin.

The breakdown of starch by ptyalin, which begins inthe mouth, continues for some time after the food mass reaches the stomach. The acid in the stomach inactivates this enzyme, and starch breakdown stops.

When no food is in the stomach, only small amounts of gas­tric juice are present. When food is taken in, the flow of gastric juice increases. There are three mechanisms involved in stimulating the flow of gastric juice.

1. The thought, sight, smell, or taste of food stimulates the brain to send messages to the gastric glands, causing them to secrete moderate amounts of gastric juice.

2. Food touching the lining of the stomach stimulates the secretion of moderate amounts of gastric juice.

3. When a food mass enters the stomach, it stretches the stomach walls. This stretching, as well as the presence of pro­teins, caffeine, alcohol, and certain other substances, stimu­lates the lining of the stomach to secrete a hormone called gastrindirectly into the blood. Gastrin stimulates the gastric glands to produce large amounts of gas­tric juice.

Liquids pass through the stomach in 20 minutes or less. Solids must first be reduced to a thin, soupy liquid called chyme. The chyme passes in small amounts at a time through the pyloric sphincter, the muscle that controls the passage of food from the stomach into the small intestine. The stomach empties from 2 to 6 hours after a meal. Hunger is felt when an empty stomach is churning.

If the thick mucus layer that protects the stomachwallbreaks down, a part of the stomach wall may be digested, and a painful ulcer develops. It is thought that some ulcers are caused by the over secretionof gastric juice brought on bynervousness or stress. Ulcers are treated bydiet, medication, or, in severe cases, by surgery.

The Small Intestine

     The small intestine is a coiled tube about 6.5 meters long and about 2.5 centimeters in diameter. The first 30 centimeters of the small in­testine are called the duodenum. Pancreatic juice and bile from liver and pancreas mix with the food in the duodenum. Most chemical digestion and almost all absorption occur In the small intestine. Unlike the stomach with its acid secretions, fluids inthe small intestine are generally alkaline.

 In the small intestine, chyme is mixed with bile from the liver, pancreatic juice from the pancreas, and intestinal juice from glands in the wall of the intestine. These three secretions contain the enzymes and other substances necessary to complete digestion

Intestinal juice.

The walls of the small intestine contain mil­lions of intestinal glands, which secrete intestinal juice. Intes­tinal juice contains enzymes that complete the digestion of carbohydrates, fats, and proteins.

In the small intestine, molecules of proteins, carbohydrates, and fats are broken down into the end products of digestion.

Proteins are broken down into amino acids,

Carbohydrates are broken down into simple sugars,

Fats are broken down into fatty acids and glycerol.

A sum­mary of the secretions of the human digestive system and their functions is given in Table.

Intestinal juice contains the following enzymes:

Erepsin—digests proteins into amino acids.

Maltase—digests maltose into glucose,

Lactase—digests lactose (milk sugar) into glucose and galactose.

Sucrase—digests sucrose (cane sugar) into glucose and fructose.

Lipase (Small quantities) —digest fats into fatty acids and glycerol.

Pancreas

The pancreas is a soft, triangular organ located between the stomach and the small intestine. The pancreas produces a substance called pancreatic juice, which is a mixture of several enzymes.

The pancreas also produces substances called insulin and glucagon, which are important in controlling the level of blood sugar.

 Pancreatic juice:

When the acid chyme from the stomach enters the small intestine, it stimulates cells in the intestinal lining to secrete two hormones into the blood, Secretin and Cholecystokinin. These hormones stimulate the pancreas to secrete pancreatic juice and pancreatic enzymes, which pass through the pancreatic duct into the upper part of the small intestine. Pancreatic juice contains sodium bicarbonate, which neutralizes the acid in the chyme and makes the pH of the contents of the small intestine slightly alkaline (pH 8). The enzymes secreted by the pancreas act on every major compo­nent of food—proteins, carbohydrates, fats, and nucleic acids,

 Pancreatic juice:  Contains three enzymes

Proteases (Trypsin and chemotropism): digests peptones into amino acids.

Amylase (Amylopsin): changes starch into maltose.

Lipase:  changes fats into fatty acids and glycerol.

Bile.

The cells of the liver produce bile, which passes through ducts into the gallbladder, where it is stored. Bile passes from the gallbladder to the upper part of the small intestine through the bile duct. The release of bile from the gallbladder is stimulated by the hormone Cholecystokinin. Bile contains no enzymes, but it aids in the digestion of fats and oils by breaking them up into tiny droplets. This process, called emulsification, increases the surface area for enzyme action. Since bile is alkaline, it aids in neutralizing the acid chyme from the stomach,

 Liver

The liver is the largest organ in the body. Besides form­ing bile, it also has a number of other functions.

It changes excess glucose to glycogen and stores it;

It destroys old, worn-out red blood cells;

It converts amino acids into glucose and a nitrogenous waste called urea, which is removed from the blood in the kidneys;

    Itproduces prothrombin, one of the substances needed in the clotting of blood,

It prepares fat for use by the body;

It serves as a reservoir for storing blood.

Absorption:

The small intestine is the site of absorption. Simple sugars, amino acids, vitamins, minerals, and other sub­stances are absorbed through the wall of the small intestine into the blood vessels of the circulatory system. Fatty acids and glycerol are absorbed into tiny vessels of the lymphatic system called lacteals, lymph vessels.

The small intestine has a number of structural features that increase its surface area and make it ideally suited for absorp­tion.

(1)    The small intestine is very long.

(2)    Its lining has many folds.

(3)    The lining is covered with mil­lions of fingerlike projections called villi.

(4)    The epithelial cells have tiny projections called microvillus that further increase the surface area.

  Within each villus there is a network of blood capillaries, and in the center is a lacteal. During absorption, digested nutrients pass through the epithelial cells and enter either the capillaries or the lacteal. Absorption involves both diffusion and active transport,

The Large Intestine

    Undigested and unabsorbed materials pass from the small intestine into the large intestine. The large intestine is about 1.5 meters long and 6 centimeters in diameter. No digestion occurs in this portion of the digestive system.

On the lower right side of the abdomen, where the small intestine joins the large intestine, is a small sac, the appen­dix. The appendix plays no part in the function­ing of the human digestive system. Occasionally, however, the appendix becomes infected, a condition known as appen­dicitis.

One of the principal functions of the large intestine is the reabsorption of water from the food mass. If too little water is absorbed, diarrhea results; if too much water is ab­sorbed, constipation results.

A second function of the large intestine is the absorption of vitamins produced by bacteria. Intestinal bacteria live on undigested food material. They produce vita­min K, which is essential for blood clotting, and some of the B vitamins. When large doses of antibiotics destroy the intes­tinal bacteria, a vitamin K deficiency may result.

The third function of the large intestine is the elimination of undigested and indigestible material from the digestive tract. This material consists of cellulose from plant cell walls, large quantities of bacteria, bile, and mucus, and worn-out cells from the digestive tract. As this material travels through the large intestine, it becomes feces. Fecal matter is stored in the last part of the large intestine, the rectum, and periodically eliminated, or defecated, through the anus.

Digestive system in Ruminansia

Ruminant animal ( ruminansia) have different tooth formation with human being. Molar tooth used to digest food ,and incisor used to nip and cut food in the form of grass. Kramer ( 1995:130) explaining that stomach of ruminansia , like sheep, ox and buffalo consist of rumen ( abdomen), retikulum ( stomach of fish-net), omasum(book stomach), abomasum ( acid stomach). Grass that eaten  still harsh and come into rumen and  reticulum to be digested mechanicly by thick wall movement, chemically by ferment bacterium.

Abomasum similar to human being stomach. In abomasum, food digested mechanicly by wall of abomasum and chemically digestion of by yielded enzyme. Food of abomasum come into small intestine to be digested furthermore.  At ruminansia , there are functioning cellulose enzyme digest cellulose, where do not there are at human being.

Mechanism of animal digestion of ruminansia the following:  mouth - throat - rumen - reticulum - trap - throat - omasum - abomasum - small intestine - large intestine - anus.

DIGESTIVE PROCESS

 Diparity /Desease on Digestive system

Disparity in digestive System its immeasurable.  The cause factor : among others unfavourable food, malnutrition, health and hygiene, balance of nutrition, pattern eat less precise, existence of disparity and infection  at  digestive organ.

1. Diarrhea, condition where  flow of feces from stomach to intestine is too fast so defecation becomes more often with feces much contains water. Diarrhea can be caused by stress, bad diet, and food that can cause irritation in intestine wall
2. Constipation, it happens if chime to the intestine very slowly so water is much absorbed by intestine. This caused feces becomes hard and dry. Constipation can be caused by lack in consuming fibrous food or too much consuming meat.
3. Peritonitis ( the inflammation of abdominal cavity membrane ), that is infection in abdominal cavity membrane ( peritoneum )
4. Appendixitis ; that is inflammation in appendix
5. Cholic, the appearance of pain in stomach because of wrong digesting for example  because of eating too much or the influence of alcohol  and chili
6. Ulcus, inflammation in stomach wall that is caused by the production of gastric juice (particulary HCl) is high, while the amount of food entering is a little amount
7. Parotitis, infection in parotis gland, its often called goiter disease
8. Xerostamia, that is a condition where the amount of saliva produced is very small in amount