Topic 2 Flashcards
Outline the functions of the conducting airways
Low resistance pathway for airflow
Defense against chemicals and other harmful substances that are inhaled
Warming and moistening the air
Nose: Humidifies the air entering and filters particles (thanks to the Vibrissae).
Pharynx: Air then passes through the 3 parts of the pharynx which offers a low resistance path for airflow into the larynx and then finally into the trachea.
Larynx: In addition to its function as the ‘voice box’ it also protects the trachea from invasion of foods and fluids.
Pulmonary ventilation
inflow and outflow of air between the atmosphere and the lungs
Total lung capacity
volume of air in the lungs after a maximum inhalation. The sum of the Vital capacity and residual volume.
Tidal volume
Volume of air breathed in and out in any one breath
Expiratory reserve volume
volume of air in excess of tidal volume that can be exhaled forcefully
Inspiratory reserve volume
additional inspired air over and above tidal volume
Residual volume
volume of air still contained in the lungs after a maximal exhalation
Vital capacity
Maximum volume of air that can be exhaled after a maximum inhalation
Mechanics of ventilation
Air flows because of pressure differences between the atmosphere and gases inside the lungs.
During inhalation the intercostal muscles (between the ribs) and diaphragm contract to expand the chest cavity.
The diaphragm flattens and moves downwards and the intercostal muscles move the rib cage upwards and out. - This increases the space for the lungs.
This increase in size decreases the internal air pressure and so air from the outside (at a now higher pressure than inside the thorax) rushes into the lungs to equalize the pressures.When we exhale the diaphragm and intercostal muscles relax and return to their resting positions. This reduces the size of the thoracic cavity, thereby increasing the pressure and forcing air out of the lungs.
Why do ventilation rates increase
breathing rate increases during exercise as the expiratory centre sends impulses to the expiratory muscles (internal intercostals) which speeds up the expiratory process;
increase CO2 causes the acidity of the blood to increase (decrease blood pH)/a change in acidity of the blood is detected by chemoreceptors which send nerve impulses to the respiratory muscles which increase the rate of ventilation (faster/deeper);
Outline the role of haemoglobin in oxygen transport
98.5% of oxygen in the blood is transported by hemoglobin as oxyhemoglobin within the red blood cells
Hemoglobin is the protein that allows oxygen to bind to a red blood cell. Hemoglobin contains a central Iron ion which can hold up to 4 oxygen atoms per heme. These oxygen atoms are then diffused into the tissues once they reach their target. While they are diffusing they are also picking back up CO2 & returning it back to lungs so you can exhale it into the atmosphere.
Explain the process of gaseous exchange at the alveoli
Gas exchange is carried out by a complex of structures at the end of each bronchioles.
The oxygen exchange in the lungs takes place across the membranes of small balloon-like structures called alveoli attached to the branches of the bronchial passages.
These alveoli inflate and deflate with inhalation and exhalation. The elasticrecoil of these helps in the exhalation. Gases move by diffusion from where they have a high concentration to where they have a low concentration:
The alveoli create a pressure gradient.
Once the alveoli fill up with air during inhalation the oxygen diffuses from the air in the alveoli and into the blood.
The carbon dioxide diffuses from the arriving venous blood and into the air which exits the body during exhalation.
State the composition of blood
Blood is composed of cells (erythrocytes, leucocytes and platelets) and plasma. Blood is the transport vehicle for electrolytes, proteins, gases, nutrients, waste products and hormones.
- Transports nutrients, oxygen, carbon dioxide, waste products and hormones to cells and organs around the body.
- Protects us from bleeding to death, via clotting, and from disease, by destroying invasive micro-organisms and toxic substances.
- Acts as a regulator of temperature, the water content in cells, and body pH.
erythrocytes
Make up 40-45% of the blood volume known as hematocrit. Contain an oxygen-carrying pigment called haemoglobin, which gives blood its red color.
Leucocytes
White blood cells <1% of blood volume, primarily involved in immune fuction and protecting body from infection. They do this by ingesting foreign microbes in a process called phagocytosis.