Human Respiratory System

Hanes Magnet School7th Grade Science

Mr. Bombick

Human Respiratory Tract Outline

• Anatomy of the Respiratory Tract (both Upper and Lower Tracts)

• Control of Breathing• Physiology of Breathing• Measurements of Human

Breathing• Homeostatic Mechanisms of the

Respiratory System• Diseases of the Respiratory Tract

Respiratory Tract-Anatomy

• The respiratory tract can be divided into two major parts, the upper and lower respiratory tract

• The upper respiratory tract consists of the nose and the pharynx

• The lower respiratory tract consists of the trachea and the lungs

Events in the Upper Respiratory Tract

The nose and pharynx make up the upper respiratory tract. The upper respiratory tract has several important functions which include the filtering of air, the warming of the air, and humidifying the air before the air reaches the lower respiratory tract.

Nose hairs help filter out particulates from the air to prevent them from getting into the lower airways. Tissues lining the nasal cavity contain many small blood vessels which help to warm the air. These tissues also secrete mucous which further helps filter the air. Many of the cells that line the nasal cavity also contain cilia which can transport the mucous containing the dust and particulates to the back of the nasal cavity to be coughed out or swallowed and digested in the stomach.

The air finally flows into the region of the larynx.

Upper Respiratory Tract-Anatomy

Lower Respiratory Tract-LarynxThe larynx contains two major parts; the vocal cords and the epiglottis. The epiglottis is a flap of cartilage that helps prevent food from going into the lower respiratory tract. Stimulation of the larynx by ingested food also initiates a type of coughing or gag reflex to help prevent food from getting into the lower respiratory tract. A person can choke on food if the epiglottis fails to close the opening of the trachea.

The vocal cords consists of two folds of connective tissue that becomes stretched and vibrated when air passes through. The length of the vocal cords determines the pitch of the sound and the volume of sound is dependent on the intensity of expiration. Sound is only produced when air is passing through the cords. The production of sound can definitely be under voluntary control.

Lower Respiratory Tract-Continued

• The trachea is the major airway from the larynx to the two bronchi

• The trachea is surrounded by cartilaginous rings that help maintain the tubular shape

• Two bronchi branch off of the trachea• The bronchi go into the lungs and

start to branch into smaller tubes called bronchioles

• The terminal parts of the smallest bronchioles create the alveolar sacs where gas exchange occurs

Lower Respiratory Tract-Anatomy

Control of Breathing

Breathing is an automatic and rhythmic action produced by bundles of neurons in the pons and medulla of the hind brain. These bundles of neurons direct muscles that form the walls of the thorax and abdomen and produce differences in pressure that move air into and out of the lungs. The respiratory rhythm and the length of each phase of respiration are set by alternating stimulatory and inhibitory actions of the neurons in the brain stem.

Respiratory Physiology

As the diaphragm moves down and the rib cage moves up and out, the lungs expand. During inspiration, the expansion of the lungs causes the pressure in the lungs (and alveoli) to become slightly negative relative to atmospheric pressure (creation of a vacuum). As a result, air moves from an area of higher pressure (the air) to an area of lower pressure (our lungs & alveoli). During expiration, the respiration muscles relax & lung volume decreases. This causes pressure in the lungs (and alveoli) to become slight positive relative to atmospheric pressure. As a result, air leaves the lungs.

Respiratory Physiology (cont.)

Respiratory Physiology (cont.)

The Respiratory System The exchange of gases (O2 & CO2) between the alveoli & the blood occurs by simple diffusion: O2 diffusing from the alveoli into the blood & CO2 from the blood into the alveoli. Diffusion requires a concentration gradient. So, the concentration (or pressure) of O2 in the alveoli must be kept at a higher level than in the blood & the concentration (or pressure) of CO2 in the alveoli must be kept at a lower lever than in the blood. We do this, of course, by breathing - continuously bringing fresh air (with lots of O2 & little CO2) into the lungs & the alveoli.

Show Two Video Clips

Breathing Measurements

Breathing measurements are obtained using a plethysmograph

Breathing Measurements (cont.)

• VC = vital capacity—The amount of air that can be forced out of the lungs after a maximal inspiration (4.6/3.6 liters)

• VT = Tidal volume—The amount of air breathed in or out during normal respiration (0.5/0.39 liters)

• TLC = Total lung capacity—The volume of air contained in the lung at the end of maximal inspiration; The total volume of the lung (6.0/4.7 liters)

• RV = Residual volume—The amount of air that stays in the lungs after maximal expiration (1.2/0.93 liters)

Homeostasis of Respiration

• Central chemoreceptors of the central nervous system are sensitive to pH in the blood (increased CO2 in the blood means more acidic conditions and therefore, lower pH) and adjust breathing rate accordingly

• Peripheral chemoreceptors detect variations of the oxygen in the arterial blood, in addition to detecting arterial CO2 and pH (decrease in pH increases breathing rate)

Homeostasis of Respiration (cont.)

• Mechanoreceptors are located in the airways and lung lining to control reflex reactions that prevent over inflation of the lungs. Other upper airway mechanoreceptors control responses as coughing, sneezing, closure of the glottis, and hiccups. A spinal cord reflex is responsible for activation of respiratory muscles for a gasping response, hypoventilation, and increases in breathing frequency and volume.

• In addition, respiration can be affected by conditions such as emotional state (limbic system) or temperature (hypothalamus).

• Voluntary control of respiration originates from the cerebral cortex although chemoreceptors are capable of overriding conscious control.

Respiratory Pathologies

• Cancers of the Respiratory System (include all structures of the respiratory system)

• COPD (Chronic Obstructive Pulmonary Disease) includes chronic bronchitis and emphysema

• Cystic Fibrosis• Variety of infections (viral, bacterial,

protists, helminthes, nematodes, fungi, etc.)

• Asthma

Emphysema

Normal Lung Emphysema

Lung Cancer

Cystic Fibrosis