Question

We talked about a diversity of respiratory strategies used by animals in class. One of the main differences between fish & frogs compared to reptiles, and mammals was that fish and frogs use buccal pumps and reptiles and mammals use suction pumps. How do buccal and suction pumps differ (please refer to where volume and pressure is changed and how it moves the respiratory medium through the respiratory system)? Explain how frogs use buccal pumps and mammals use suction pumps to ventilate their lungs. Birds use a modified pump system - how is this pump system of the bird different from mammals?

Answer 1

Difference between buccal pumbing and suction pumbing

In mammals while breathing, the diaphragm and muscles around the rib cage cause a change of volume in the lungs. The increased volume of the chest cavity decreases the pressure inside, creating an imbalance with the ambient air pressure, resulting in suction.

In frog, buccal pumping is used to force water into the “stomach,” which will increase 50–100-fold in volume.

Frogs do not have ribs nor a diaphragm, which in humans helps serve in expand the chest and thereby decreasing the pressure in thelungs allowing outside air to flow in. In order to draw air into its mouth the frog lowers the floor of its mouth, which causes the throat toexpand.

Buccal pumbing

• It is "breathing with one's cheeks":
• Method of ventilation used in respiration in which the animal moves the floor of its mouth in a rhythmic manner that is externally apparent.
• It is the sole means of inflating the lungs in amphibians.

There are two methods of buccal pumping, defined by the number of movements of the floor of the mouth needed to complete both inspiration and expiration.

Four stroke

• Four-stroke buccal pumping is used by some basal ray-finned fish and aquatic amphibians.
• This method has several stages.
• First, the glottis (opening to the lungs) is closed, and the nostrils are opened. The floor of the mouth is then depressed (lowered), drawing air in. The nostrils are then closed, the glottis opened, and the floor of mouth raised, forcing the air into the lungs for gas exchange.
• To deflate the lungs, the process is reversed.

Two stroke

Two-stroke buccal pumping completes the process more quickly which seen in most extant amphibians.

• In this method, the floor of the mouth is lowered, drawing air from both the outside and lungs into the buccal cavity.
• When the floor of the mouth is raised, the air is pushed out and into the lungs
• The amount of mixing is generally small, about 20 percentage.

Mammal's ventilation

In mammals, pulmonary ventilation occurs via inhalation .

• During inhalation, air enters the body through the nasal cavity located just inside the nose  
• As air passes through the nasal cavity, the air is warmed to body temperature and humidified.
• Particulate matter that is floating in the air is removed in the nasal passages via mucus and cilia.
• The processes of warming, humidifying, and removing particles are important protective mechanisms that prevent damage to the trachea and lungs.
• Thus, inhalation serves several purposes in addition to bringing oxygen into the respiratory system.
• From the nasal cavity, air passes through the pharynx and the larynx, as it makes its way to the trachea .
• The main function of the trachea is to funnel the inhaled air to the lungs and the exhaled air back out of the body.
• The human trachea sits in front of the esophagus and extends from the larynx into the chest cavity where it divides into the two primary bronchi at the midthorax.
• It is made of incomplete rings of hyaline cartilage and smooth muscle
• The trachea is lined with mucus-producing goblet cells and ciliated epithelia.
• The cilia propel foreign particles trapped in the mucus toward the pharynx.
• The cartilage provides strength and support to the trachea to keep the passage open.
• The smooth muscle can contract, decreasing the trachea’s diameter, which causes expired air to rush upwards from the lungs at a great force.
• The forced exhalation helps expel mucus when we cough.
• The end of the trachea bifurcates (divides) to the right and left lungs.
• The right lung is larger and contains three lobes, whereas the smaller left lung contains two lobes .
• The muscular diaphragm, which facilitates breathing, is inferior to the lungs and marks the end of the thoracic cavity
• In the lungs, air is diverted into smaller and smaller passages, or bronchi.
• Air enters the lungs through the two primary bronchi.
• Each bronchus divides into secondary bronchi, then into tertiary bronchi, which in turn divide, creating smaller and smaller diameter bronchioles as they split and spread through the lung.
• In humans, bronchioles with a diameter smaller than 0.5 mm are the respiratory bronchioles.
• They lack cartilage and therefore rely on inhaled air to support their shape.
• The terminal bronchioles subdivide into microscopic branches called respiratory bronchioles.
• The respiratory bronchioles subdivide into several alveolar ducts.
• Numerous alveoli and alveolar sacs surround the alveolar ducts.
• Terminal bronchioles are connected by respiratory bronchioles to alveolar ducts and alveolar sacs.
• Each alveolar sac contains 20 to 30 spherical alveoli.
• Air flows into the atrium of the alveolar sac, then circulates into alveoli where gas exchange occurs with the capillaries.
• Mucous glands secrete mucous into the airways, keeping them moist and flexible.
• In the acinar region, the alveolar ducts are attached to the end of each bronchiole.
• At the end of each duct are approximately 100 alveolar sacs, each containing 20 to 30 alveoli that are 200 to 300 microns in diameter.
• Gas exchange occurs only in alveoli. Alveoli are made of thin-walled parenchymal cells, typically one-cell thick, that look like tiny bubbles within the sacs.
• Alveoli are in direct contact with capillaries (one-cell thick) of the circulatory system.
• Such intimate contact ensures that oxygen will diffuse from alveoli into the blood and be distributed to the cells of the body. In addition, the carbon dioxide that was produced by cells as a waste product will diffuse from the blood into alveoli to be exhaled.
• The anatomical arrangement of capillaries and alveoli emphasizes the structural and functional relationship of the respiratory and circulatory systems.
• Because there are so many alveoli within each alveolar sac and so many sacs at the end of each alveolar duct, the lungs have a sponge-like consistency.
• This organization produces a very large surface area that is available for gas exchange.
• This large surface area, combined with the thin-walled nature of the alveolar parenchymal cells, allows gases to easily diffuse across the cells.

Birds respiratory system

• Birds have a larynx. An organ termed the "syrinx" serves as the "voice box."
• Birds have lungs, but they also have air sacs.
• Depending upon the species, the bird has seven or nine air sacs. Air sacs do not play a direct role in oxygen and carbon dioxode exchange, however they do keep oxygen rich air moving, in one direction, through the avian respiratory system.
• The air sacs of birds extend into the humerus the femur, the vertebrae and even the skull.
• Birds do not have a diaphragm; instead, air is moved in and out of the respiratory system through pressure changes in the air sacs.
• Muscles in the chest cause the sternum to be pushed outward.
• This creates a negative pressure in the air sacs, causing air to enter the respiratory system.
• Expiration is not passive, but requires certain muscles to contract to increase the pressure on the air sacs and push the air out.
• Because the sternum must move during respiration, it is essential that it is allowed to move freely when a bird is being restrained.
• Bird lungs do not expand or contract like the lungs of mammals.
• In mammalian lungs, the exchange of gases occur in 'alveoli.'. In the avian lung, the gas exchange occurs in the walls of microscopic tubules, called 'air capillaries.'

The respiratory system of birds is more efficient than that of mammals, transferring more oxygen with each breath.

Birds have a slower respiratory rate than mammals.

Respiration in birds requires two respiratory cycles to move the air through the entire respiratory system. In mammals, only one respiratory cycle is necessary.

Respiratory cycle

• During the first inspiration, the air travels through the nostrils, also called nares, of a bird, which are located at the junction between the top of the upper beak and the head.
• Air moves through the trachea to the syrinx, which is located at the point just before the trachea divides in two.
• It passes through the syrinx and then the air stream is divided in two as the trachea divides.
• The air does not go directly to the lung, but instead travels to the caudal (posterior) air sacs.
• A small amount of air will pass through the caudal air sacs to the lung
• During the first expiration, the air is moved from the posterior air sacs through the ventrobronchi and dorsobronchi into the lungs.
• The bronchi continue to divide into smaller diameter air capillaries.
• Blood capillaries flow through the air capillaries and this is where the oxygen and carbon dioxide are exchanged
• When the bird inspires the second time, the air moves to the cranial air sacs
• On the second expiration, the air moves out of the cranial air sacs, through the syrinx into the trachea, through the larynx, and finally through the nasal cavity and out of the nostrils.