In both human lungs cover

an area of 90 m² – almost

a size of a tennis court.

Essential Vocabulary

Alveolus (pl –i) to attach anterior

breathlessness to branch bronchial

bronchiole to breath carotid

capacity to contract costal

cartilage to cough coronary

chest to exchange dorsal

cilium (pl- a) to expand gaseous

diaphragm to expand persistent

larynx to irritate responsible

ligament to lead tidal

lumen to narrow thoracic

lung to relax

pleura

rate

1. Укажите существительные, соответствующие глаголам в Essential Vocabulary.

2. Образуйте прилагательные от следующих существительных (воспользуйтесь словарем, если необходимо):

Alveolus, breathlessness, bronchiole, cartilage, chest, larynx, lung, pleura, respiration, rib, sternum, thorax, trachea.

Аналитическое чтение

Gaseous exchange in mammals

Lungs are the site of gaseous exchange in mammals. They are found deep inside the thorax of the body and so their efficient ventilation is essential. The lungs are delicate structures and, together with the heart, are enclosed in a protective bony case, the rib cage. There are twelve pairs of ribs in humans, all attached dorsally to the thoracic vertebrae. The anterior ten pairs are attached ventrally to the sternum. The remaining ribs are said to be 'floating'. The ribs may be moved by a series of intercostal muscles. The thorax is separated from the abdomen by a muscular sheet, the diaphragm.

Air flow in mammals is tidal, air entering and leaving along the same route. It enters the nostrils and mouth and passes down the trachea. It enters the lungs via two bronchi which divide into smaller bronchioles and end in air-sacs called alveoli.

Regions of the respiratory system. (Figure) Air passes through the pharynx and past the epiglottis, a flap of cartilage which prevents food entering the trachea. The larynx (voice box) at the anterior end of the trachea is a box-like, cartilaginous

structure with a number of ligaments, the vocal cords, stretched across it. Vibration of these cords when air is expired produces sound waves.

The trachea divides into two bronchi, one entering each lung. The bronchi are also supported by cartilages. The bronchioles branch throughout the lung. These eventually end in alveoli. Each lung is surrounded by an air-tight cavity called the pleural cavity. This is bounded by two membranes, or pleura, which secrete pleural fluid into the cavity. The fluid is a lubricant, preventing friction when the lungs expand at inspiration. Pressure in the pleural cavity is always lower than in the lungs and this allows them to expand and fill the thorax.

Breathing in (inspiration) in humans

In order for air to enter the lungs from the exterior, the pressure inside the lungs must be lower than that of the atmosphere. When the external intercostal muscles contract and the internal intercostal muscles relax, the ribs move upwards and outwards. The diaphragm muscle contracts and flattens. These two movements cause the volume of the thorax to increase and therefore the pressure inside it falls. The elastic lungs expand to fill the available space and so their volume increases and the pressure within them falls. This causes air to rush into the lungs from the exterior.

Breathing out (expiration) in humans

Breathing in is an active process but breathing out is largely passive. The volume of the thorax is decreased as the diaphragm muscle relaxes and resumes its dome-shape. The external intercostal muscles also relax, allowing the ribs to move downwards (posteriorly) and inwards (dorsally). They may be assisted by contraction of the internal intercostal muscles. As the volume of the thorax decreases, the pressure inside it increases and air is forced out of the lungs as their elastic walls recoil.

Grammar 1. Повторение форм страдательного залога времен