14 heart anatomy and fetal changes

8/12/2019 14 Heart Anatomy and Fetal Changes

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The Heart

The Cardiovascular System

What are the components?

(See an anatomy bookand chapter 9 of G&H)


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Functions of

the Heart Blood vessels

Arteries- away from

heart Veins- toward heart

Pulmonary circuit-blood to lungs

Systemicblood toorgans of the body Includes heart and

lung wall tissues


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Location Base- inferior

border of secondrib

Apex- rests ondiaphragm and inbetween 5thand6thrib

Tilts to the leftand anteriorly


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Pericardial Membranes (3

total) and Heart wall

Fibrous skeleton- anchoring, structural support, and electrical insulation


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Atria Right:

Auricle Smooth wall

(posterior) Pectinate muscles Crista terminalis Fossa ovalis Coronary sinus, IVC,

SVC openings

Right AV valve Left:

Mostly smooth withpectinate muscle

Left AV valve

What vessels lead into each atria?Describe the blood these vessels are carrying


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ventricles

Trabeculae Carneae

Papillary muscles

Chordae tendineae Valves


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Valves


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Sulci and

Vessels Coronary sulcus

Interventricular

sulci (anterior andposterior)

Cardiac vessels

Arteries

veins


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Blood Flow

Pulmonary vs systemic circuit


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Lub-Dub Sounds


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Conductive System of theHeart-Myogenic (72bpm)

Muscle, not Nerves thatare autorhythmic!

Sinoatrial node-pacemaker

Internodal bundles

Atrioventricular node

Atrioventricularbundles (bundle ofHis)

Bundle branches

Purkinje fibers


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Innervation by AutonomicNervous System

Alter rate and Force only!

Visceral sensory

Parasympathetic- (Vagus)-slow down (20bpm or evenstop)- SA would normally beatat 100bpm- but vagal toneslows down.

Sympatheticspeed up(230bpm)

Hypothalamus and Amygdalaand Medulla Oblongata

Most dense at SA and AVnode


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Review of Heart Muscle

Cardiocytes

Branch

Intercalated discs-interdigitating folds,mechanical junctions(desmosomes) andelectrical junctions(gap junctions).


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Fetal Circulation

Foramen ovale- rightto left shunt. Most

of the blood goesthrough here.

Ductus arteriosus-right to left shunt.


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Blood Flow within the Fetal Heart

Right atrium Foramen ovale

Left ventricle

Left atrium

Systemic circuit

Aorta

Right ventricle

Pulmonary trunk Ductus arteriosus

Pulmonary

circuit

(Most of the blood)


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Birth

Prostaglandin levels drop

Baby breathes- lowerspressure in pulmonary circuit

Umbilical cord is clamped andcut and increases systemicpressure

Foramen ovale closes andbecomes fossa ovalis

Ductus arteriosus closes andbecomes ligamentumarteriosum (oxygen content issignal for vessel to close)


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Foramen OvaleFossa Ovalis


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L igamentum Ar ter iosum

Ductus Ar ter iosus


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PDA- patent ductus arteriosus

Left to right shunt

Blood flows back tolungs repeatedly- why?

Net CO decreases soblood vol. increase andCO goes back towardnormal

Left and rightventricular hypertrophy

Characteristic cyanosisof baby

Pulmonary

veins


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Tetralogy of Fallot

Blue Babies

Right to left shunt

Tetralogy of Fallotis made up of 4heart defects


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Physiologic considerations

Electrical features to know Cardiac muscle fibers: branched, with intercalated

disks. Gap junctions. Low resistance (1/400) pathwayfor electrical spread from cell to cell.

functional syncitium

Two types of fibers in the heart:specialized(orleading cells andcontractile(or following cells.)

Autorhythmicity; intrinsic to the specialized cells. AP isgenerated within these cells (membrane feature) notfrom nerves or hormones. intrinsic rhythm Nerves,hormones can modify rate or force.


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Mechanical (contraction) features to know:

4 chambers, septa, valves

Non-conductive connective tissue skeleton, wringing action. In

ventricles direction is propelling blood from apex toward base. Systole = period of contraction and emptying

Diastole = period of relaxation and filling

Specify which chamber, as atrial and ventricular events are not thesame. Show this!

Ohms law: Pressure difference = flow x resistance

Pressures generated in rt and left sides are different (more later.)

Valves: damage can lead to stenosis and/or regurgitation


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Physiologicconsiderations

Vasculature: Normal circuit is A,a,c,v,V Arteries: thick wall, narrower

lumen than veins of same outer

diameter. Muscular and elastic.Stretch and recoil, give backpotential for kinetic energy.

Arterioles: resistance vessels;precapillary sphincters.

Capillaries: exchange vessels,

thin wall, simple squamousendothelium, diffusion. Venules: thin walled, more elastic Veins: Capacitance vessels, hold

large volume of blood supply


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Right/left side differences: In series circuit, R to L and around again.

Same amt of blood pushed by each side, cardiacoutput. CO=6L/min at rest.

R side (pulmonary circuit) pushes blood to lungs; lowresistance circuit

L side (systemic circuit) pushes blood to all organs in

head, torso and limbs, ie. The system; high resistancecircuit.

In summary, same amt of blood, but with differentresistance, require different pressures.

MAP on L side = 100 mm Hg; MAP on R side =10 mm Hg


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Series Circuit

14 heart anatomy and fetal changes

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