Lecture 16: Comparative Anatomy Of The Heart Flashcards
1
Q
Describe the main components of the vertebrate cardiovascular system
A
- Muscular pump:
- Heart
- Vessels carrying blood away from the heart:
- Arteries
- Note that whether they are carrying oxygenated or deoxygenated blood is immaterial.
- Vessels carrying blood toward the heart:
- Veins
- A series of connecting vessels associated with the pharyngeal arches:
- Aortic arches
2
Q
Describe the layers of the pericardial cavity
A
The heart is enclosed within a sac composed of serous membranes:
- Layers:
- Parietal pericardium:
- Outer layer of the sac
- Pericardial cavity:
- The potential space between the inner and outer layers of the sac
- Visceral pericardium:
- The inner layer of the sac
3
Q
Describe the heart
A
The heart is a subdivided, muscular tube made up of several layers:
- Layers:
- Epicardium: Thin, outer layer of the heart
- Myocardium: Thicker, middle layer composed of cardiac muscle tissue. Coronary arteries and veins supply the heart muscle directly with oxygenated blood.
- Endocardium: Thin, layer lining the cavities. Continuous with endothelium of blood vessels
4
Q
Describe the fish heart
A
- Single pass, unidirectional pump
- Four chambers:
- Sinus venosus with sinoatrial valve:
- Thin-walled sac
- Similar in structure to veins
- Receives deoxygenated blood from:
- Common cardinal veins (= ducts of Cuvier).
- Receive:
- -Anterior and posterior cardinal veins
- Hepatic veins
- Atrium with atrioventricular valve
- Thicker wall than sinus venosus
- Ventricle
- Thickest wall of any heart chamber
- Main muscular pump
- Conus arteriosus with semilunar valve(s)
- Extends cranially as ventral aorta
- In teleosts = bulbous arteriosus.
5
Q
The amphibian has a three chambered heart, (Atrium, Ventricle, and the conus truncus arteriosus). Describe the atrium.
A
- Completely divided in amphibians
- Partly divided in lungfishes
- Right atrium receives deoxygenated systemic blood.
- Left atrium receives oxygenated pulmonary blood via pulmonary vein.
- Walls of both atria contain trabecular folds.
6
Q
The amphibian has a three chambered heart, (Atrium, Ventricle, and the conus truncus arteriosus). Describe the ventricle.
A
- Single ventricle
- Thicker muscular wall than found in atria
- Receives deoxygenated blood from right atrium
- Receives oxygenated blood from left atrium
- Trabecular arrangement of ventricular wall mostly keeps the two blood supplies separated.
7
Q
The amphibian has a three chambered heart, (Atrium, Ventricle, and the conus truncus arteriosus). Describe the conus truncus arteriosus
A
- Partially subdivided by spiral valve
- Blood from right side of ventricle is preferentially sent to pulmonary arteries.
- Blood from left side of ventricle is preferentially sent to head and rest of body.
8
Q
Describe the reptilian heart
A
- Atria:
- Completely divided as in amphibian
- Ventricle:
- Incompletely divided in most reptiles
- Completely divided in crocodilians
9
Q
Describe the turtle heart
A
- Right atrium receives deoxygenated systemic blood.
- Left atrium receives oxygenated pulmonary blood.
- Single ventricle partly subdivided into left and right chambers:
- Left side = cavum arteriosum.
- Right side = cavum venosum.
- Two sides are connected by interventricular canal.
- Right side of ventricle is further subdivided by a muscular septum.
- This subdivision creates a ventral cavum pulmonale.
- Muscular septum serves as a one-way valve for the interventricular canal
10
Q
Describe the pathway of blood flow through the turtle heart
A
- Systemic deoxygenated blood from vena cava →
- Into right atrium →
- Through right atrioventricular valve →
- Into cavum venosum→
- Into cavum pulmonale→
- Through semilunar valve →
- Into pulmonary artery →
- To Lungs
- Oxygenated blood through pulmonary veins →
- Into left atrium →
- Through left atrioventricular valve →
- Into cavum arteriosum →
- Through interventricular canal →
- Into cavum venosum →
- Through semilunar valves →
- Into left and right aortae.
11
Q
What occurs in a turtle heart during atrial and a ventricular contraction?
A
- During atrial contraction:
- Atrioventricular valves open and occlude interventricular canal.
- Keeps oxygenated and deoxygenated blood separated.
- During ventricular contraction:
- Interventricular canal opens.
- Oxygenated blood flows into cavum venosum.
- Muscular flap closes off cavum pulmonale.
12
Q
Describe Blood Flow through a Crocodilian Heart
A
- Ventricles completely divided.
- Paired ventricles:
- Each with aorta:
- Right aorta from left ventricle.
- Left aorta from right ventricle.
- Pulmonary trunk also leaves from right ventricle.
- Crossing of aortae:
- Communicating hole = Foramen of Panizzae.
13
Q
What adaptions does a reptile events for “diving”
A
- Blood shunted from lungs:
- Action via vagus nerves.
- Constriction of pulmonary arteries.
- Slowing of heart rate.
- Blood from right atrium must by-pass lungs:
- Shunted to left ventricle in crocodilians:
- Through foramen of Panizzae.
- Sent to aortae from right ventricle in other reptiles.
14
Q
Describe the Early-Stage Development of the Mammalian Heart
A
- Arises from splanchnic mesoderm.
- Early stage:
- Paired double-walled tubes:
- Outer layer of epimyocardium.
- Inner layer of endocardium.
- Linear organization of cardiac tubes:
- Conus arteriosus (cranial).
- Ventricle.
- Atrium.
- Sinus venosus (caudal).
15
Q
Describe Further Development of the Mammalian Heart
A
- Fusion of cardiac tubes:
- Begins at cranial end of future heart
- Intrinsic pulsation of tube begins with fusion.
- Conus arteriosus:
- Begins to pulsate first.
- Has slowest intrinsic rate of pulsation.
- Fusion of cardiac tubes:
- Sinus venosus is last to fuse and to pulsate:
- Has fastest rate of pulsation
- Overrides pulsation rates of other parts of the cardiac tube
- Becomes adult pacemaker of the heart
- See Slide 24-29
