Tetrapods Flashcards
Terrestrial vertebrates respiration
Respiratory airways conducts air between the atmosphere and the gas exchange surfaces.
Ventilation moves air through the airways into and out of the lungs. Amphibians and some reptiles have air forced into the lungs whilst reptiles, birds and mammals have air flowing in because of a negative pressure caused by the expansion of the rib cage and muscular contraction.
Respiratory system of tetrapods include
The respiratory airways, lungs and thoracic structures involved in ventilation.
Ventilation: Amphibians
The air enters the pocket of the buccal cavity. The Glottis opens and there is an elastic recoil of lungs and compression of the chest wall which reduces the lungs volume. Air is this forced out of the lungs and nares. The nares close and the floor of the buccal cavity rises and air is pushed into the lungs. The glottis then closes and gas exchange occurs in the lungs.
Ventilation: Mammals and reptiles
Breathing is an alternation between inhalation and exhalation. It is the mixing of pre- and post-exchange air.
Inhalation is active and involves the expansion of the thoracic cavity where the lungs become inflated by negative pressure. It involves the contraction of the intercostal muscles in most reptiles and the intercostal muscles and diaphragm of mammals and some reptiles.
Exhalation is usually passive and involves the contraction of the thoracic cavity where air is pushed out by positive pressure. It involves the relaxation of muscles.
Muscles involved in inhalation
Sternocleidomastoid muscle Scalene muscles Pectoralis minor muscle Serrated anterior muscle External intercostal muscles Diaphragm
Muscles involved in exhalation
Transversus thoracic muscle
Internal intercostal muscles
Rectus abdominis and other abdominal muscles.
Geometric arrangements of the structural components
Cross current gas exchange
Countercurrent gas exchange
Uniform pool gas exchange
Models for respiratory gas exchange:
OPEN EXCHANGE
Cutaneous exchange.
Oxygen goes to the capillaries and CO2 is produced which is placed back in the air.
It a constant exchange.
Models for respiratory gas exchange:
UNIFORM POOL EXCHANGE
Mammalian lung.
Ventilation through tidal flow.
Gas exchange occurs at each breath. Osmotic pressure of oxygen is uniform in the exchanger (lungs).
Models for respiratory gas exchange:
CROSSCURRENT EXCHANGE
Avian lung.
The alveoli are arranged radially, with tidal flow ventilation in the air sacs.
Airflow is unidirectional, with the assistance of parabronchi.
Gas exchange occurs at each breath.
Air enters the parabronchus at a high oxygen osmotic pressure which then decreases.
Bronchi
An airway in the respiratory tract that conducts air into the lungs.
Metazoans Circulatory System
In order to overcome the limits of diffusion.
The movement of the medium (blood) is does the bulk of the transport.
It moves the nutrients, gases, wastes, hormones, immune defenses and heat.
It’s functions are transportation, regulation and protection.
Circulatory system is made up of
A fluid (blood/hemolymph) which carries the molecules of interest. A pump (heart) which moves the fluid. And vessels that carry the fluid between the pump and the tissues. Although enclosed vessels are absent in many animals.
Open Circulatory system
Hemolymph bathes tissues directly.
The heart pumps the hemolymph through a network of open-ended channels.
This is present in most mollusks, and in all arthropods.
Closed Circulatory system
The circulating fluid, blood, is not the same as the extracellular fluid. The blood is kept in vessels. The heart is necessary.
This method is more efficient than the open circulatory system.
Present in cephalopods, annelids and vertebrates.
Living in water
In water, blood is approximately weightless thus there is only fluid resistance to overcome.
A two-chambered heart is present.
The blood flow is unidirectional, and goes from the ventricle to the gills, the the rest of the body and finally the atrium. This is a single circulation mechanism.
The gradient of oxygen rich to oxygen poor blood limits the amount of oxygen that can reach some organs/tissues.
Living on land
Double circulation mechanism is used.
There are two loops, one for the oxygenation of the blood and the other to take oxygen to the rest of the body.
The high pressure in the vessels pushes the bloods to the lungs and the body.
Vertebrate Circulatory system
Blood goes from the heart to the arteries, then the arterioles. From there it goes to the capillaries where the exchanging of nutrients of nutrients, gases and wastes occur. It then goes to the venules, to the veins and finally back to the heart.
Pulmonary vein
Oxygen rich, and travels to the heart.
Pulmonary artery
Oxygen poor and travels away from the heart.
Circulatory system: Amphibians
Three chambered heart, which includes two atria and one ventricle, where the mixing of oxygenated and deoxygenated blood occurs in the ventricle.
Double circulation occurs where one loop has oxygen rich blood and the other has oxygen poor blood. The spiral valve directs the oxygenated blood from the ventricle to the left atrium.
Two circulatory routes in amphibians
The pulmocutaneous circuit, where the blood travels from the ventricle to the lungs and skin and finally to the left atrium.
The other route is the systemic circuit, where the blood travels from the ventricle to the rest of the body and finally to the atrium.
Circulatory system: Reptiles (Turtles, snakes, lizards)
Three chambered heart with two atria and one ventricle. The ventricle has three cavities and a partial septa. The mixing of oxygenated and deoxygenated blood also occurs in the ventricle but less than that of amphibians.
There are two systemic aortas present.
Aorta
The main artery of the body supplying oxygenated blood to the circulatory system.
Intracardiac shunting in Reptiles
Intracardiac shunting occurs during a dive where there is a pulmonary bypass and most of the is transported through the systemic circuit.
Two circulatory routes in reptiles
In the Pulmonary circuit, the blood is transported from the ventricle to the lungs and finally to the left atrium.
In the systemic circuit the blood travels from the ventricle to the rest of the body and finally to the right atrium.
Circulatory system: Crocodilians
Four chambered heart present with some mixing of the oxygenated and deoxygenated blood, although very minimal. The ventricles are completely divided with the lungs and the systemic systemic being completely separated meaning an increase in the delivery of oxygen.
Cog tooth valve in crocodiles
Diverts blood away from the crocodiles lungs to their body and is controlled by the amount of adrenalin in the bloodstream.
Might allow crocodiles to dive for serial hours without needing to resurface to breathe.
Right to left shunt in crocodiles.
There is a cog tooth valve in the pulmonary artery.
When the right ventricle is closed, the foramen of panizza allows the left ventricle to pump to both aortas.
Circulatory System: Mammals and birds
Four chambered heart present, with two atria and two ventricles. Double circulation mechanism, with no mixing of oxygenated and deoxygenated blood. The oxygenated blood travels from the left heart to the system whilst deoxygenated blood goes from the right lung to the lungs.
It is the most efficient transport of oxygen.
Parabronchi
Tertiary bronchi in the avian lung.
Ventilation: birds
Inhalation causes the air sacs to fill. Air form the previous inhalation is pushed out of the parabronchi which fills the anterior sacs. The posterior sacs are then filled from the new inhalation and some air enters the parabronchi.
Exhalation is where the old air is exhaled and the air in the lungs are renewed. The air from the posterior sacs are pushed into the parabronchi and the air from the anterior sacs are exhaled via the trachea.
