Respi Anaphysio

Anatomy and Physiology ANATOMY-the branch of science that studies the physical structure of animals, plants, and other organisms PHYSIOLOGY-the branch of biology that deals with the internal workings of living things, including functions such as metabolism, respiration, and reproduction, rather than with their shape or structure

Parts of the Respiratory System Structurally, the respiratory system consists of two parts: 1. Upper Respiratory Tract 2. Lower Respiratory Tract Functionally, the respiratory system consists of two parts: 1. The conducting portion 2. The respiratory portion Respiratory Tract The respiratory tract is the path of air from the nose to the lungs. It is divided into two sections: Upper Respiratory Tract Lower Respiratory Tract. Lower respiratory tract 1. Nose 2. Pharynx (throat) 3. Associated structures Upper Respiratory Tract 1. Larynx (voice box) 2. Trachea (windpipe) 3. Bronchi 4. Lungs

The conducting portion is composed of: -nose -nasopharynx -larynx -trachea -bronchi -bronchioles(terminal and respiratory) Respiratory portion -this is specialized for the rapid exchange of gases between blood and air. Function: Further cleaning of inspired air composed of: 1.respiratory bronchioles 2.alveolar ducts 3. alveoli Air moves through the body in the following order: Nostrils A nostril (or naris) is one of the two channels of the nose, from the point where they bifurcate to the external opening. Nasal cavity The nasal cavity (or nasal fossa) is a large air-filled space above and behind the nose in the middle of the face. It conditions the air to be received by the areas of the respiratory tract. Owing to the large surface area provided by the conchae, the air passing through the nasal cavity is warmed or cooled to within 1 degree of body temperature. In addition, the air is humidified. And finally dust and other particulate matter are removed by the fine hairs present in the nostril. Pharynx

The pharynx is the part of the neck and throat situated immediately posterior to the mouth

and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea.

Because both food and air pass through the pharynx, a flap of connective tissue called the epiglottis

closes over the trachea when food is swallowed to prevent choking or

aspiration.

In humans the pharynx is important in vocalization.

Larynx

(voice box)

The larynx colloquially known as the voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production. The larynx houses the vocal folds,

and is situated just below where the tract of the pharynx splits into the trachea and

the esophagus. Sound is generated in the larynx, and that is where pitch and volume are manipulated.

Trachea

(wind pipe)

The trachea, or windpipe, is a tube that has an inner diameter of about 20-25 mm and a length of about 10-16cm. It extends from the larynx to the primary (main) bronchi in mammals allowing the passage of air to the lungs. It is lined with pseudostratified ciliated columnar epithelium cells with mucosae goblet cells which produce mucus. The esophagus lies posteriorly to the trachea. The cartilaginous rings are incomplete because this allows the trachea to collapse slightly to allow food to pass down the esophagus. The epiglottis is the flap that closes the trachea during swallowing to prevent swallowed matter from entering the trachea. Thoracic cavity (chest) The thorax is the region of the body formed by the sternum, the thoracic vertebrae and the ribs. It extends from the neck to the diaphragm, not including the upper limbs. The heart and the lungs reside in the thoracic cavity, as well as many blood vessels. Bronchi (right and left) A bronchus is a caliber of airway in the respiratory tract that conducts air into the lungs. No gas exchange takes place in this part of the lungs. The trachea (windpipe) divides into two main bronchi (also mainstem bronchi), the left and the right, at the level of the sternal angle. The right main bronchus is wider, shorter, and more vertical than the left main bronchus. The right main bronchus subdivides into three segmental bronchi while the left main bronchus divides into two. Alveoli (site of gas exchange) An alveolus (plural: alveoli, from Latin alveus, "little cavity"), is an anatomical structure that has the form of a hollow cavity. In the lung, the pulmonary alveoli are spherical outcroppings of the respiratory bronchioles and are the primary sites of gas exchange with the blood. The lungs contain about 300 million alveoli, representing a total surface area of 70-90 square metres, each wrapped in a fine mesh of capillaries. It has a radii of about 0.1 mm and wall thicknesses of about 0.2 µm. It consists of an epithelial layer and extracellular matrix surrounded by capillaries. In some alveolar walls there are pores between alveoli. There are three major alveolar cell types in the alveolar wall (pneumocytes): Type I cells that form the structure of an alveolar wall. Type II cells that secrete surfactant to lower the surface tension of water and allows the membrane to separate thereby increasing the capability to exchange gases. Type III cells that destroy foreign material, such as bacteria. The alveoli have an innate tendency to collapse (atelectasis) because of their spherical shape, small size, and surface tension due to water vapor. Phospholipids, which are called surfactants, and pores help to equalize pressures and prevent collapse. Regulation The flow of air in and out of the lungs is controlled by the nervous system, which ensures that humans breathe in a regular pattern and at a regular rate. Breathing is

carried out day and night by an unconscious process. It begins with a cluster of nerve cells in the brain stem called the respiratory center. These cells send simultaneous signals to the diaphragm and rib muscles, the muscles involved in inhalation. The diaphragm is a large, dome-shaped muscle that lies just under the lungs. When the diaphragm is stimulated by a nervous impulse, it flattens. The downward movement of the diaphragm expands the volume of the cavity that contains the lungs, the thoracic cavity. When the rib muscles are stimulated, they also contract, pulling the rib cage up and out like the handle of a pail. This movement also expands the thoracic cavity. The increased volume of the thoracic cavity causes air to rush into the lungs. The nervous stimulation is brief, and when it ceases, the diaphragm and rib muscles relax and exhalation occurs Pulmonary gas exchange Pulmonary gas exchange is driven by passive diffusion and thus does not require energy for exchange. Substances move down a concentration gradient. Oxygen moves from the alveoli (high oxygen concentration) to the blood (lower oxygen concentration, due to the continuous consumption of oxygen in the body). Conversely,

carbon

dioxide

is

produced

by

metabolism

and

has

a

higher

concentration in the blood than in the air. Oxygen in the lungs first diffuses through the alveolar wall and dissolves in the fluid phase of blood. The amount of oxygen dissolved in the fluid phase is governed by Henry's Law. Oxygen dissolved in the blood may diffuse into red blood cells and bind to hemoglobin. Binding of oxygen to hemoglobin allows a greater amount of oxygen to be transported in the blood. Although carbon dioxide and oxygen are the most important molecules exchanged, other gases are also transported between the alveoli and blood. The amount of a gas that is exchanged depends on the water solubility of the gas the affinity of the gas for hemoglobin. Water vapor is also excreted through the lungs, due to humidification of inspired air by the lung tissues. Red blood cells transit the alveolar capillaries in about 3/4 of a second. Most gases (including carbon dioxide and nitrous oxide) reach equilibrium with the blood before the red blood cells leave the alveolar capillaries. Gases that reach equilibrium before the blood leaves the alveolar capillaries are perfusion limited, since the amount of the gas exchanged depends solely on the volumetric flow rate of blood past the alveoli.

However, carbon monoxide is stored in such high concentrations in the

blood, due to its strong binding to hemoglobin, that equilibrium is not reached before the blood leaves the alveolar capillary. Thus, the concentration of carbon monoxide in the arterial system can be used to assess the resistance of the alveolar walls to gas diffusion. Transport of carbon monoxide is thus termed diffusion limited. Oxygen is normally perfusion limited, but in disease conditions it can be diffusion limited.