Maintenance of the Human Body Part 3: The Respiratory System Concepts: chapter 24

The respiratory system Body cells continually use O 2 & produce CO 2 as a waste product. Respiratory system moves these 2 gases. Consists of: Nose Pharynx Larynx Trachea Bronchi Lungs

The respiratory system—structures Nose fxns to filter & moisten air. Also receptors for smell. Pharynx is posterior to nasal & oral cavities. It’s a passageway for air, food, voice resonance, houses tonsils. Larynx connects pharynx with trachea. Walls are composed of cartilage.

The respiratory system —structures

Trachea is reinforced with C-shaped hyaline cartilage. Goes from larynx to level of 5 th thoracic vertebrae. Then it branches. Bronchi are the 2 tubes that enter the right & left lung.

The respiratory system —structures Trachea  primary bronchi  secondary bronchi  tertiary bronchi  bronchioles  terminal bronchioles

The respiratory system—structures Lungs are covered in double layer called pleural membrane. Consists of: Parietal pleura Visceral pleura Pleural cavity is in btwn These membranes help to reduce friction.

The respiratory system —structures Each lung has a hilum which is the region through which the bronchi, pulmonary blood vessels, lymphatic vessels & nerves enter and exit. Right lung is slightly larger. It has 3 lobes. Left has 2.

The respiratory system—structures At the end of each terminal bronchiole are clusters of alveoli. Alveoli have very thin, moist walls that are closely associated with capillaries. The walls also have “dust cells” which are phagocytic immune cells.

The respiratory system—ventilation Respiration = the process of gas exchange. There are 3 parts: 1. Pulmonary—inhalation & exhalation 2. External—exchange btwn alveoli & capillaries (O 2 in to blood, CO 2 out) 3. Internal—exchange btwn blood & tissue cells (O 2 into tissue cells, CO 2 out)

The respiratory system—ventilation Inhalation Diaphragm contracts & flattens. Intercostal myo’s contract & raise rib cage. (these first two actually occur at the same time) Volume of the thoracic cavity increases, so pressure inside decreases. Air moves in b/c pressure inside lungs is less than air pressure.

The respiratory system—ventilation

Diaphragm decends ~1cm during relaxed breathing & ~10 cm during strenuous breathing. Accessory myo’s can elevate sternum & upper ribs to increase thoracic volume even more.

The respiratory system—ventilation Exhalation Usually a passive process. There is elastic recoil of the thoracic structures—they tend to spring back after being stretched. Diaphragm relaxes & rises. Intercostal myo’s relax & rib cage lowers. Thoracic cavity space decreases, air is forced out.

Lung volumes

The respiratory system—gas exchange Gases diffuse in & out of alveoli & vessels based on pressure differences. If oxygen has higher partial pressure in alveoli than in capillaries, it will diffuse into capillaries. The opposite is also true.

The respiratory system—gas exchange Oxygen doesn’t dissolve well in water. It must be carried in red blood cells by the protein hemoglobin. The higher the partial pressure of O 2, the more saturated Hb is.

The respiratory system—gas exchange pH can also affect the affinity of Hb for oxygen. Exercising tissues produce several metabolic acids. What does that do to Hb’s ability to “let go” of the oxygen so it can diffuse into active tissues?

The respiratory system—gas exchange

CO 2 is transported differently. Some is dissolved in blood plasma (non cellular part of blood) A little more is transported on Hb Most is transported as bicarbonate ion.

The respiratory system—control Cortical influences Cerebral cortex has connections with the respiratory center in medulla oblongata. You can voluntarily change your breathing pattern. Limited by build up of CO 2 & H+.

The respiratory system—control Chemoreceptor regulation Chemoreceptors can sense changes in certain chemicals. An increase in CO 2 causes a decrease in pH. Chemoreceptors detect this. Respiratory center sends signals to myo of inhalation & exhalation. Breathing rate & depth is increased.

The respiratory system—control Other factors affect respiration: Emotional anxiety  ↑ rate Temperature ↑Temp  ↑ rate Sudden ↓temp  temporary apnea Pain—brief apnea, then rate ↑ Airway irritation  apnea followed by cough or sneeze.

The end…