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

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