Тhe skeleton. The Heart and the Vascular System. The Lungs. The Alimentary tract

Тhe skeleton

The skeleton is composed of bones. In the adult the skeleton has over 200 bones.
The bones of the skull consist of cranial and facial parts. There are 26 bones in the skull. The spine consist of the cervical thoracic, lumbar, and sacral vertebra and the coccyx. There are 32 or 34 vertebrae in the spinel of the adult. The chest (Thorax) is composed of 12 Thoracic vertebrae, the breastbone and 12 pairs (har) of ribs. The breastbone is a long bone in the middle of the chest. Тhe basic part of the chest is formed by the ribs. Each rib is composed of a head, nech and body.

The lower extremity consist of the high leg and foot. The upper extremity is formed by the arm, forearm and hand.

The Heart and the Vascular System

The Lungs

The Alimentary tract

Tract The alimentary tract is a musculomembraneous canal. It extends from the oral cavity to the anus. It consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The first division of the alimentary tract is formed by the mouth. Important structures of the mouth are the teeth and the tongue. The stomach is a dilated portion of the alimentary canal. It measures about 21 -25 cm in length, 8-9 cm in its greatest diameter. It has a capacity of from 2. 14 to 4. 28 1 (litres). The small intestine is a thin-walled muscular tube. is composed of the duodenum, jejunum and ileum. It is divided into caecum, colon and rectum. The liver is the largest gland in the human body.

Work of the Human Heart
The human heart contracts from the first moment of life. Тhe heart pump the blood through the arteries to all the parts of the body. Тhe total weight of the blood pumped by the heart daily is about ten tons. In the adult the heart makes from 60 to 72 beats per minute. In children the rate of heartbeat is much higher. The rate of heartbeat increases depending on different emotions. Each cardiac cycle consists of three phases: the atrial systole, the ventricular systole, the diastole. The left ventricle discharges out the blood through the aorta to the systemic circulation. Ventricle to the lungs through the pulmonary arteries. The atria act as receiving chambers.

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