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Egan's Chapter 9 - CV Part 1

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The ultimate function of the cardiovascular system
To ensure that all tissues are adequately perfused
Potential events if inadequate perfusion of tissue occurs
- Less than peak performance
- Inability to heal
- If stressed long enough, it will die
The leading cause of death in the US
Cardiovascular Disease (2600 people die each day, 2x more than cancer)
The most common CVD
Coronary Artery Disease
Risk factors for CVD
- Genetics (#1)
- Hypertension (HTN)
- Elevated cholesterol
- Diabetes (esp. Type II)
- Obesity
- Smoking
- Inactivity
- Gender (women are catching up to men)
When is a fetus potentially viable?
24-26 weeks
When does surfactant secretion begin?
24 weeks
When does a fetus secrete sufficient surfactant?
25-28 weeks
What is the first functional organ?
The heart (day 22)
When do the lungs begin to develop?
6 weeks
When do the lungs begin to function?
At birth
Why does a fetus need a different CV system than before birth?
Because the lungs do not function.
Describe fetal CV circulation
Umbilical vein from placenta to liver, Ductus venosus to IVC, right atrium, Foramen Ovale(bypass) connects right atrium to left atrium, Ductus arteriosus, Umbilical arteries (2)
Long term volume maintenance is based primarily on what?
Low pressure baroreceptors in atria and large thoracic veins
Describe post-natal CV circulation
Occlusion of placental flow causes pressure drop in IVC and right atrium, Aeration of lungs results in increased pulmonary flow, increased flow raises pressure in left atrium, also closure of umbilical arteries increases systemic pressure, Pressure gradient closes foramen ovale
List the mechanisms responsible for the changes that occur in the transition from fetal to postnatal circulation
Pressure and chemical changes due to increased alveolar pressure lead to anatomical and physiological changes in the circulatory system
Anatomical structures that make up the fetal circulation
Umbilical vein from placenta to liver, Ductus venous to IVC, Right atrium, Foramen Ovale connect right atrium to left atrium, Ductus arteriosus, Umbilical arteries
Describe the average person's heart
Cone shaped muscle; fist size
What borders the heart in the mediastinum?
Lungs, vertebrae, and sternum
Where is the base of the heart?
At the 2nd rib
Where is the apex of the heart?
At the 5th intercostal space
Three layers of the pericardium
- Fibrous
- Perietal
- Visceral
Describe the fibrous pericardium
- Attached to the great vessels and the diaphragm
- It is a tough, inelastic connective tissue
Describe the serous pericardium
- A delicate double layer of serous membrane
- Parietal pericardium lines the inside of the fibrous pericardium
- Visceral pericardium - covers the surface of the heart
- Pericardial cavity is the space between the parietal and
visceral pericardium
Three walls of the heart
- Epicardium
- Myocardium
- Endocardium
Epicardium
The outer covering of the heart (AKA visceral pericardium)
Mycardium
Middle layer - cardiac muscle tissue
Endocardium
Inner layer of epithelium and connective tissue
What is the purpose of the fluid in the percardial cavity?
Lubricate and reduce energy demands
What is the difference between the visceral pericardium and the epicardium?
Location
Four chambers of the heart
- L atrium
- L ventricle
- R atrium
- R ventricle
Which are the receiving chambers?
The atria
Which are the pumping chambers?
The ventricle
Describe the two atria
- Right atrium receives deoxygenated blood from body tissues
- Left atrium receives oxygenated blood from lungs
What separates the two atria?
The interatrial septum
Fossa ovalis
A depression in the interatrial septum that is the residual of the foramen ovale of the fetal circulation
Describe the two ventricle
- Right ventricle pumps blood to the lungs
- Left ventricle pumps blood to the body tissues
What separates the two ventricle?
The interventricular septum
Cardiac skeleton
- ring of connective tissue that encircles the valves.
- electrically isolates the atria from the ventricles
The two septum found in the postnatal heart
...
The four valves found in the heart
- Bicuspid/mitral (AV)
- Tricuspid (AV)
- Aortic (semilunar)
- Pulmonary (semilunar)
The two atrioventricular valves
- Bicuspid (or mitral) L
- Tricuspid R
The two semilunar valves
- Aortic L
- Pulmonary R
The purpose of the AV valves
To assure that blood flows in one direction from the atrium to the ventricle
The purpose of semilunar valves
To assure that blood flows in one direction from the ventricles to the large arteries they connect to
Bicuspid/mitral valve location
Between LEFT atrium and LEFT ventricle
Tricuspid valve location
Between RIGHT atrium and RIGHT ventricle
Aortic valve location
Between LEFT ventricle and aorta
Pulmonary valve location
Between RIGHT ventricle and pulmonary trunk
The functions of all valves in the heart
- To keep blood flowing in one direction
- To make the heart more efficient and use less energy
Chordae tendonae
Strong fibrous strings that attach cusps of AV valves to heart wall
Stenosis
Narrowing of aperture (partial obstruction)
Regurgitation
Valve fails to close completely and allows backflow
Describe the physiological processes that can result from mitral stenosis
- Left atrium works harder than left ventricle
- Blood begins to back up
- More energy is expended with less positive results
- Heart murmurs
Describe the physiological processes that can result from mitral regurgitation
- Left ventricle works harder than left atrium
- Heart murmurs
13 steps of blood flow through the heart
1. R atrium
2. Tricuspid
3. R ventricle
4. Pulmonary valve
5. Pulmonary trunk
6. Pulmonary arteries
7. Lungs
8. Pulmonary veins
9. L atrium
10. Bicuspid/Mitral valve
11. L ventricle
12. Aortic valve
13. Aorta