Gaseous Exchange in Humans

Comprehensive practice flashcards covering structures, mechanics, gaseous exchange processes, lung capacities, and homeostatic control of breathing based on lecture notes.

What is the difference between breathing, cellular respiration, and gaseous exchange?

Breathing is a mechanical process of moving air in and out of the lungs. Cellular respiration is a chemical process within cells that breaks down organic compounds to release energy (ATP). Gaseous exchange is a physical process involving the diffusion of gases ($O_2$ and $CO_2$) across respiratory surfaces.

What are the six essential requirements for an efficient gaseous exchange organ?

1. Large surface area to volume ratio; 2. Thin and permeable surface; 3. Moist surface; 4. Well-ventilated; 5. Protected from mechanical injury and desiccation; 6. Vascular transport system.

How are the nasal cavities adapted to facilitate gaseous exchange?

They are lined with epithelial and goblet cells producing mucus, which together with cilia trap dirt and sweep it out, keeping the cavity moist, while blood capillaries warm incoming air.

What is the structure and function of the trachea?

The trachea (windpipe) is situated in front of the oesophagus and is held open by C-shaped cartilage rings that protect it and keep it open for easy movement of air.

How do the bronchi and bronchioli differ in structure?

The trachea branches into left and right bronchi held open by O-shaped cartilage rings and lined with mucous membranes. Bronchi divide into smaller bronchioli, which do not have cartilage for reinforcement.

What structural adaptations of the alveoli maximize gas exchange efficiency?

Alveoli have single-cell thick walls of squamous epithelial cells for easy diffusion, tissue fluid keeping walls moist, a large blood capillary network surrounding them, and a large total surface area.

What is the function of the epiglottis?

It is a cartilage structure on top of the larynx (voice box) that closes when food is swallowed to prevent food from entering the trachea.

What is the role of the double pleural membrane and pleural fluid?

Each lung is surrounded by a double pleural membrane containing pleural fluid, which acts as a lubricant to prevent friction during inhalation and exhalation.

What physical changes occur during the process of inhalation?

The diaphragm muscle contracts and flattens downwards, external intercostal muscles contract lifting the ribcage upwards and outwards, chest volume increases, lung air pressure decreases below atmospheric pressure, and air flows in as an active process.

What physical changes occur during the process of exhalation?

The diaphragm relaxes and moves upwards, external intercostal muscles relax allowing the ribcage to move down and inward, chest volume decreases, air pressure in lungs increases relative to outside pressure, forcing air out as a passive process.

How does the composition of exhaled air differ between rest and exercise?

Inhaled air contains $78\%$ nitrogen, $21\%$ oxygen, and $0,04\%$ carbon dioxide. Exhaled air from a sleeping person contains $16\%$ oxygen and $4\%$ carbon dioxide. Exhaled air from an exercising person contains $12\%$ oxygen and $9\%$ carbon dioxide.

In the bell jar model of breathing, what do each of the components represent?

The glass tube represents the trachea, the balloon represents the lung, the bell jar represents the chest or thoracic cavity, and the rubber sheet represents the diaphragm.

What are two main limitations of using the bell jar apparatus as a human breathing model?

1. The bell jar is rigid and cannot move, whereas the human ribcage expands and contracts; 2. The model demonstrates only one balloon/lung, whereas humans have two lungs.

How are Tidal volume, Vital capacity, and Residual volume defined on a spirometer trace?

Tidal volume is the amount of air inhaled or exhaled during a normal breath. Vital capacity is the maximum amount of air that a person can exhale after taking the deepest possible breath. Residual volume is the amount of air remaining in the lungs after a maximal forced exhalation.

How does gaseous exchange occur across the alveolus wall?

Inhaled air in the alveoli has a higher $O_2$ concentration and lower $CO_2$ concentration than deoxygenated blood in surrounding capillaries; $O_2$ diffuses into blood and $CO_2$ diffuses into alveoli to be exhaled.

How does gaseous exchange occur at the tissue level?

Oxygenated blood in tissue capillaries has a higher $O_2$ concentration than body cells, so $O_2$ diffuses into cells. Cells have a higher $CO_2$ concentration due to respiration, so $CO_2$ diffuses into blood.

In what forms are oxygen and carbon dioxide transported in human blood?

Most oxygen combines with haemoglobin in red blood cells (erythrocytes) to form oxyhaemoglobin. Most carbon dioxide is transported in blood plasma as bicarbonate ions.

What sequence of events restores normal blood carbon dioxide levels during homeostatic control?

1. Receptor cells in carotid artery in neck are stimulated by elevated $CO_2$; 2. Impulses are sent to medulla oblongata in brain; 3. Medulla oblongata stimulates breathing muscles and heart; 4. Breathing muscles contract more actively, increasing breathing rate/depth and heart rate; 5. More $CO_2$ is exhaled, returning blood levels to normal.

How does high altitude affect gaseous exchange and how does the body compensate?

At high altitude, less oxygen is absorbed by red blood cells due to lower pressure. The body compensates by producing more red blood cells (erythrocytes) to carry sufficient oxygen.

Based on the anatomical diagram, what are the primary components of the human gas exchange system?

The system includes the nasal cavity, trachea, pleural cavity (filled with fluid), lungs, bronchus, bronchiole, alveoli, intercostal muscles, ribs, and diaphragm.

Based on the diagram of inhalation mechanics, what muscular actions cause the chest to expand?

The intercostal muscles contract to lift the ribcage upwards and outwards, while the diaphragm muscle contracts and flattens downwards, increasing thoracic cavity volume.

How are catabolism, aerobic respiration, and anaerobic respiration defined?

Catabolism is the breaking down of complex molecules into simple molecules to release energy. Aerobic respiration occurs in the presence of oxygen, whereas anaerobic respiration occurs in the absence of oxygen.

What is haemoglobin and what role does iron (Fe) play in its function?

Haemoglobin is an oxygen-carrying protein pigment found in red blood cells (erythrocytes). Iron ($Fe$) is the element in the haemoglobin molecule to which oxygen atoms bind.