Exam 2 (Lecture 3) - Heart and Vessels Flashcards
Describe the hilus of the lung. Discuss structures that pass through it, as well as the function of these structures.
1) The hilus of the lung is relatively the same across domestic species.
2) Structures:
- Principal bronchus
- Nutritional blood supply (bronchiole artery and vein)
- Functional blood supply (pulmonary artery and vein)
- Lymphatics
- Nerves
What are impressions and which do you see on the lung in a fixed specimen?
Impressions are made when an animal is embalmed with the organs still in place (in this case, the lung).
- on the lung specimens, you will see the aortic impression (most dorsal) and the esophageal impression
(ventral to the aortic impression)
Discuss the cardiac notch in the lungs.
1) Where the cardiac notch is located, the heart is going to be contacting the thoracic wall directly (i.e. there is no lung tissue between the heart and the thoracic wall).
- This is important to know for sampling the cardiac cavity and for ultrasounds
2) There ARE cardiac notches on both sides of the animal, but the L cardiac notch is the largest. (In the carnivore, the R cardiac notch is larger “right on Rover”).
What is different about the trachealis muscle in the carnivore vs. the horse and ruminant?
1) In carnivores, the trachealis muscle lies external to the cartilage.
2) In horses, it’s internal to the cartilage
3) In cattle, the free edges of the cartilage project dorsally and give it a pyramidal appearance.
What are the muscles of inspiration? Which is most significant?
1) Muscles of inspiration:
- Diaphragm (most significant; accounts for 70% of inspiratory effort at rest)
- External intercostals
- Levator costae
- Scalenus
- Serratus ventralis thoracis
- Rectus thoracis
- Serratus dorsalis cranialis
- In general, muscles with a caudoventral fiber direction are inspiratory.
What are the muscles of expiration? What is their primary function at rest? Which muscle is the biggest factor at rest?
1) Muscles of expiration: mostly passive at rest
- Internal intercostals (biggest factor at rest; the other muscles play a larger role during exercise and disease processes)
- Retractor costae
- Transversus thoracis
- Interchondralis costae
- Serratus dorsalis caudalis
- Iliocostalis lumborum
- In general, muscles with a cranioventral fiber direction are expiratory.
Which muscles are both inspiratory and expiratory?
Muscles of the abdominal press
- External abdominal oblique
- Internal abdominal oblique
- Transverse abdominis
- Rectus abdominis
- These muscles have to relax on inspiration to allow the abdominal viscera to move caudally; and have to contract with expiration (expiration with force; such as when you have a cough).
When a horse has heaves, which muscle becomes prominent? Why?
The external abdominal oblique (AKA heave line)
This prominence is due to hypertrophy of the muscle due to the increased workload.
What are the layers of the pericardium?
From outer-most to inner-most:
- Mediastinal pleura
- Fibrous layer of the pericardium (continuous with the adventitia of the great vessels in the pericardial cavity)
- Parietal pericardium (continuous with the visceral pericardium)
- Pericardial cavity (potential space; in a healthy animal there is just a little bit of fluid in there)
- Visceral pericardium (epicardium; closely associated with the myocardium)
Discuss the location and orientation of the heart. Also discuss the relative size of the heart to the animal’s body size.
1) The heart is more vertical in large animals than in the carnivore
- due to this orientation, we have the sternopericardial ligament
- in the carnivores, it is the phrenicopericardial ligament
2) Located from the 3rd to 6th ribs
- olecranon process corresponds to the 5th rib/5th intercostal space so majority of the heart is under the
thoracic limb
3) Relative size:
- Horse and dog = 1% of body weight; so a 1200 lb horse would have a 12 lb heart
- Ruminant = 0.5% of body weight
- Pig = 0.3% o body weight
Discuss the auricular surface of the heart. Include structures that can be seen from this side.
1) Auricular surface of the heart = projects to the left side of the body wall (has the greatest contact with the body wall).
2) Structures:
- Can see both R and L auricles from this view
- Coronary groove (base of heart); between the atria and ventricles
- Paraconal interventricular groove (PIG) = one of the vessels that runs in it is the paraconal interventricular
branch (that comes from the left coronary in ALL species); PIG gets its name because of its close association with the conus arteriosus (part of the RV)
- The arteries, veins, and grooves are typically covered with fat. The fat reserves around the heart are the last fat reserves to be used (extreme cases of starvation/disease (cancer).
Discuss the atrial surface of the heart. Include structures that can be seen from this side.
1) Atrial surface of the heart = projecting to the right side of the body wall (has minimal contact with body wall)
2) Structures:
- Can see coronary groove (base of heart)
- Subsinusoidal interventricular groove (SIG); major vessel is the subsinusoidal interventricular branch (is a branch from the left coronary in dog and ruminant; in horse and pig it is part of the terminal part of the circumflex branch of the right coronary artery)
What are some internal structures that you can see on right atrial aspect of the heart?
1) Caudal vena cava
2) Cranial vena cava
3) Intervenous tubercle ( in adult circulation, it helps to force blood down into the RV; in fetal circulation, it helps direct blood through the foramen ovale)
4) Fossa ovalis
5) Coronary sinus (returning the blood that the heart used for its energy (there are species variations)
On the sagittal section of the right side of the heart, what are the internal structures that are seen?
1) Right and Left atria
2) Pectinate muscles (more pronounced in the right auricle)
3) Papillary muscles (anchor chordae tendinae)
4) Chordae tenindae
5) Trabeculae septomarginalis (part of the conduction system; allows the impulse to jump across the marginal part of the ventricle; found in both R and L = R is typically one very large one and L has a lot of smaller ones); ANYTHING spanning the lumen of the ventricle is going to be TS
6) Trabeculae carneae (in place to help decrease turbulence; found on inflow side (R) of heart)
What is the cardiac skeleton?
Connective tissue, cartilage, and bone situated around the aortic orifice and between the aria and ventricles.
- It’s only bone in some species like older cattle, where it is called the os cordis
The valvular plane is a high pressure area; so the skeleton is in place to prevent a blow-out from this pressure; also in place to give the atria something to contract down against the the ventricles something to contract up against.
Provides electrical separation between atria and ventricles.
