Respiratory System Overview Quiz

Respiratory System Overview

• The respiratory system is a system of tubes that filters incoming air and moves it into microscopic alveoli for gas exchange.
• The system has an upper and lower respiratory tract.
• The upper respiratory tract includes the nose, nasal cavity, and pharynx (throat).
• The lower respiratory tract includes the trachea, bronchi, and lungs. The lungs include the bronchioles, alveolar ducts, and alveoli.
• The diaphragm, ribs, and intercostal muscles play a critical role in breathing.

Respiration Definitions

• External respiration: Gas exchange between blood capillaries and the air sacs (alveoli) of the lungs.
• Internal respiration: Gas exchange between blood capillaries and body cells.
• Cellular respiration: Breakdown of organic molecules (usually glucose), in cells to release energy.

Respiratory System Structures

• Nose and Mouth: Supported by bone and cartilage. Lined with mucous membrane containing fine hairs that filter, warm, and moisten the air.
• Air Passages: Include the trachea, bronchi which split into smaller bronchioles leading to alveolar ducts which open into alveoli(tiny air sacs).
• Lungs: Spongy, cone-shaped organs protected by the thoracic cage and diaphragm. The visceral pleura lines each lung and the parietal pleura lines the thoracic cavity.
• Diaphragm, Ribs and Intercostal Muscles: The diaphragm contracts and pushes air into the lungs during inhalation. The external intercostals raise the ribs during inhalation. During exhalation the diaphragm relaxes, the intercostals relax and air is expelled.

Gas Exchange in Lungs

• The alveoli have thin walls with a rich capillary blood supply.
• Oxygen passes into the blood, combining with hemoglobin.
• Carbon dioxide diffuses out of the blood into the alveoli for removal.

Breathing Mechanics

• Inspiration: Diaphragm contracts, moving downward. External intercostal muscles contract, raising the ribs. Thoracic cavity expands, lungs enlarge, and alveolar pressure drops. Air moves into the lungs.
• Expiration: Diaphragm relaxes, moving upward. External intercostal muscles relax, ribs lower. Thoracic cavity shrinks, lungs recoil, and alveolar pressure increases. Air moves out of the lungs.

Breathing Rate and Control

• Breathing rate is primarily controlled by the brain and is mostly involuntary..
• Breathing rate increases during and after exercise to remove excess carbon dioxide from the blood.
• Skeletal muscles like the diaphragm and intercostals can have some voluntary control over breathing.
• Normal breathing rate varies with age. Adult breath ranges of about 12 to 16 breaths per minute. Infants have significantly higher breathing rates.

Control Mechanisms

• Neural pathways in the medulla control breathing.
• Chemical receptors monitor blood levels of oxygen and carbon dioxide, influencing breathing.
• Intra-pulmonary receptors such as stretch and C-fiber receptors respond to changes in lung volume and contribute to the control of breathing.

Gas Transport

• Oxygen transport primarily occurs by hemoglobin, with a small amount dissolved in the plasma and cells,
• Carbon dioxide transport occurs as dissolved carbon dioxide, bound to hemoglobin, and as bicarbonate ions in the blood.