Skeleton. The bones form skeleton of the body. In the adult the skeleton has over 200 bones. The human body is separable into the head, the trunk, the limbs.
The skeleton serves 4 major functions:
Support, movement, Blood cell production, protection: the skeleton protects many vital organs: The skull protects the brain, the eyes, and the middle and inner ears. The vertebrae protects the spinal cord. The thorax protects the lungs and heart.
The bones of the skull consists of cranial and facial parts. There are 26 bones in the skull. Skull has box-like structure.
The whole body is bilaterally symmetrical. The bones of the trunk are the spine and the chest. The spine consists of the cervical, thoracic, lumbar and sacral vertebrae and the coccyx. The chest consists of 12 thoracic vertebrae , the breastbone and 12 pairs ribs. In the chest there are the heart and the lungs.
The lower extremity consists of the thigh, leg and foot. It is connected with the trunk by the pelvis. Legs are used for standing, walking, jumping, running.
The upper extremity is formed by the upper arm, forearm and hand. It is connected with the trunk by the shoulder-girdle. The shoulder consists of 2 bones: the collar-bone and the shoulder-blade. In the wrist there are 8 small bones. Each of the fingers has 3 bones and the thumb has 2 ones. The bones are connected together by the joints or by the cartilages and ligaments. The bones consists of organic and inorganic substance.
The Muscles. Muscles are the active part of the motor apparatus; Functionally we divide all Muscles into 2 groups: voluntary and involuntary muscles. Voluntary muscles consists of striated muscle tissue and contract by the will of the man. This group includes all the muscles of the head, trunk and extremities. There are3 main types of muscular tissue that we identify and classify on the basis of structure and functions:1)smooth or visceral; 2)striated or skeletal; 3)cardiac. 1)A characteristic feature of cardiac muscle is that fibres have neither a beginning nor an end. Cardiac muscles have the strength and force of contraction of the skeletal muscle. 2)Striated muscle tissue consists of large fibres in the form of bundles. Striated muscles are most necessary for manipulation of the bones of the skeleton. Those are the muscles necessary for walking, running, turning, skeletal muscles are complex in structure. The skeletal muscles are the organ of the muscular system. Each skeletal muscle has an arterial, venous, and nervous supply. The fibres are usually parallel to each other and are united in bundles.
3) smooth muscles can contract slowly. They make up the walls of the internal organs such as those of the blood vessels and the digestive tract. Smooth muscles are not rich in blood vessels. These cells have an oval nucleus that encloses nucleoli.
Injury to the nerves which innervate muscles causes disturbances in voluntary movements.
Involuntary muscles is capable of spontaneous contraction. Smooth muscle and cardiac are voluntary muscle.
The digestive system.
The abdomen is the largest cavity of the body. It is bounded a bove by the thorax and below by 2 pelvic bones which meet in front. From the cavity of the thorax, it is separated by the great muscle of respiration the diaphragm. The organs of the abdominal cavity are the liver, the gall-bladder, the stomach, the intestines, the pancreas, the spleen, the kidneys and the bladder.
The digestive system consists of the digestive tract and digestive glands.
The digestive tract consists of : oral cavity, pharynx, esophagus , stomach, small intestine, large intestine. The wall of the greater part of the d.t. includes 3 coats: mucous, muscular, serous. The mucous coat is pink in color because it has many blood vessels. The mucous coat of the d.t. begins with the esophagus.
The muscular coat of the d.t. consists of 2 layers: an internal layer with circular muscle fibres and an external layer with longitudinal muscle fibres. Contractions of the m.c. move food along the d.t.
The serous coat that covers the digestive organs in the abdominal cavity is called the peritoneum.
It has 3 layers: visceral, parietal.
In the esophagus the serous layer is lacking. The digestive glands secrete digestive juices which take part in the chemical processes of digestion. The d.g. includes not only small glands, but large glands: the salivary glands, the liver, the pancreas. They communicate with it through ducts.
The digestive system is equipped with nerve fibres and their endings.
The liver is a large organ that weighs about 1,5 kg. It is lies under the right ribs and extends across to the left of the epigastrium. The liver secretes bile which participates in digestive process and has a defensive function.
The gall-bladder lies beneath the right lobe of the liver. The g-b serves as a bile reservoir. The stomach lies under the left ribs and extends across to the right. It serves as a container of food, which is partly digested in it. Its capacity is some 1-2 liters.
From the stomach the food passes in small intestine where it under goes further mechanical and chemical changes. As the contents of the small intestine can cot move back they may freely pass into the large intestine.
At the point where the small intestine leaves the stomach is only 1,5 to 2 inches in diameter. The large intestine is up to 2,5 inches wide.
The Urinary System. The Urinary System is system whole excretes the largest part of the waste products of the it includes 2kidneys, 2ureters, the bladder, urethra.
The kidneys are a pair bean-shaped gland, that lie in the abdomen and placed one on each site in the lumbar region of the spire. A kidney weighs about 150grams.The right kidney tends to be lower than the left one. The connective tissue membrane which adheres to the kidney is called the fibrous capsula. This casual is surrounded by perirenal fat and is called the adipose capsule. The kidney contain one million small tubes, which have to excrete products of metabolism and control the concentrations of body fluids. These tubes make up the parenchyma of the kidney. The inner margin of the kidney is known as the hilus. At the hilus the renal vein lies in front of the renal artery, the former joins the inferior vena cava. In kidney the outer light-coloured zone is the renal cortex, within this is a darker renal medulla and within this again is a space-the renal sinus which is normally occupied by fibrous sac, the renal pelvis. The cortex extends inwards in a series of the renal columns which divide the medulla into a number of renal pyramids. The function unit of the kidney is the nephron. A renal corpuscle with tubules and blood vessels.
The kidney is filtred through which the whole blood of the passes and which remove from the blood a urea, which together constitute the urine.
The ureter is a tube from each kidney which conveys the urine to the bladder. The wall of ureters is composed of 3 layers. The inner layer or mucous coat, the middle layer or muscular coat and the outer layer or fibrous coat is composed of connective tissue. It is muscular wall helps move the urine.
The bladder is a reservoir for urine. The bladder has 3 parts: apex, body, fundus. The wall of the bladder consists of 3 coatings-mucous, muscular, connective tissue.
The capacity of the bladder is about 350-500 ml.
The urethra is a tube that leads from the bladder, along which the urine is passed out of the body. It also contains numerous mucous glands.
The respirotory system. Respiration occurs in all living things, both plants and animals. The proper function of this system is perhaps the most important one in the sustaing of life. The term respiratoin means the exchange of gases between the living organism and the enviroment. An intral exchange must occur between the air in the lungs, from which the oxygen is being continualy pured, and the external air. This the process of external resperation. Incailed air contains about 20% o[ygen and four hundredths of one % carbon dioxide. Exhaled air consists of approximately 16 % oxygen and 4 % carbon dioxide. Nitrogen, which makes up about 79 % of the atmosphere, is not involved in the breathing process. Air is breathed through either the mouth or nose into the oral cavity, or pharynx. It then passes through the voice box, or larynx, into the windpipe, or trachea. The trachea ultimately divides into two smaller tubes, bronchi, one is going to each lung. 'The bronchi divide into tiny passage-ways that are named bronchioles, which lead directly to minute air sacs, or alveoli. The exchange of life-giving gases is effected through the walls of the alveoli. The movement of air into the lungs is brought about by an increase in the volume of the thoracic cavity with the action of the respiratory muscles. The lungs follow this movement passively. Some of the in-spiratory muscles have a fixed point on the ribs; when the ribs are being raised the muscles increase the anteroposterior and transverse diameters of the thoracic cavity (costal respiration). Another important muscle is the diaphragm, a thin dome-shaped «sheet», which closes the lower part of the thorax and separates it from the abdomen. The diaphragm contracts and flattens; it contributes in this way to the extension of the vertical diameter of the thoracic cavity and raises the ribs (abdominal respiration). At the time of expiration, the thorax returns to its initial position, and air is expelled through the same tracts that had been used by fresh air during inspiration. In an individual at rest the number of inspirations per minute is 10 to 15; the pulmonary ventilation, or the volume of air which passes through the respiratory system each minute, is about 6 litres per minute. During intense muscular activity the inspiration rate may rise to 50 and the ventilation to 150 litres or more per minute.