heart is center of
cardiovascular system
arteries
carry blood away from heart, which is generally oxygen-rich (except for pulmonary arteries)
veins
carry blood towards the heart that is generally oxygen-poor (except for the pulmonary veins)
Great Vessels
arteries and veins entering and leaving the heart are called the great vessels
Structure of heart ensures
the unidirectional flow of blood through both the heart and the blood vessels
- backflow of blood is prevented by valves within the heart
- divided into 2 independent, coordinated pumps
*one directs blood to the lungs for gas exchange
*other directs blood
Blood Pressure
- blood pressure develops through alternate cycles of heart wall contraction and elevation
- minimum blood pressure is essential to push blood through blood vessels to the body tissues for nutrient and waste exchange
Heart Anatomy: size and position
- fist-sized, conical organ, weights ~250-350grams
- located left of the midline; posterior to sternum in mediastinum
- rotated such that its right side or border (right atrium and ventricle) is located more anteriorly, while its left side or border (left
Base
the base is the posterosuperior of the heart, formed primarily by the left atrium
- the pulmonary veins that enter the left atrium border this base
Apex
the apex is the inferior, conical end
- it projects slightly anteroinferiorly toward the left side of body
Pericardium
- fibrous pericardium: sac of fibrous C.T. that envelops the heart; attached to great vessels + diaphragm; prevents overfilling of heart and excessive movement
- serous pericardium: parietal and visceral
parietal: lines inside of fibrous pericardium
visce
Epicardium
composted of simple squamos epithelium and areolar C.T./fat
Myocardium
cardiac muscle, thickest layer of hear wall
Endocardium
endothelium (specialize simple squamos) and areolar C.T. that surrounds internal surfaces
Atria
(R & L) are thin-walled chambers that are located superiorly
- right atrium receives blood from the systemic circuit and from heart tissue itself
- left atrium receives blood from the pulmonary circuit
Auricle
anterior part of each atrium is a wrinkled, flaplike extension called an auricle
Ventricle
- blood that enters an atrium is passed to the ventricle of the same side
- ventricles are inferior chambers
2 Arteries Exit Heart at Basal Surface
1) Pulmonary trunk: carries blood from right ventricle into the pulmonary circuit
2) Aorta: conducts blood from left ventricle into systemic circuit
Interatrial Septa
atria are separated from each other by interatrial septa
Interventricular Space
ventricles are separated from each other by interventricular space
Fibrous Skeleton of Heart
-within septa is the fibrous skeleton of the heart
- separates the atria and ventricles
- anchors heart valves by forming supportive rings
- electrical insulation between atria and ventricles; ensures that muscle impulses are timed properly
- provides a r
Right Atrium
- receives venous blood from systemic circuit and drainage from the heart muscle itself
- three major vessels empty into right atrium:
1) Superior Vena Cava
2) Inferior Vena Cava
3) Coronary Sinus
Superior Vena Cava
drains blood from head, upper limbs, and superior regions of the trunk
Inferior Vena Cava
drains blood from lower limbs and trunk
Coronary Sinus
drains blood from the heart wall
Right A/V Valve
- aka Tricuspid Valve
- separates right atrium from right ventricle
- has three triangular flaps
- venous blood flows from the right atrium through the value into the right ventricle
- valve is forced closed when the right ventricle begins to contract, pr
Right Ventricle
- receives deoxygenated venous blood from right atrium
- internal surfaces of right and left ventricles have three papillary muscles
- papillary muscles anchor chordae tendineae
- chordae attach to the cusp of the right AV valve and prevent eversion durin
Papillary muscles
cone- shaped, muscular projections
Semilunar Valve and Pulmonary Trunk
-pulmonary semilunar valve located between conus arteriosus and pulmonary trunk
- composed of three thin, pocket-like cusps
- blood is pumped into the pulmonary trunk which forces the valves open
- when ventricular contraction ceases, blood cannot backflo
Left Atrium and Left A/V Valve
- aka Bicuspid Valve
- once gas exchange occurs in lungs, oxygenated blood travels through the pulmonary veins to left atrium
- smooth posterior wall of the left atrium contains openings for four pulmonary veins
- bicuspid valve also anchored via chordae
left ventricle
- largest of all four chambers with walls typically 3X thicker than in right ventricle
- thick walls required to generate pressure to force oxygenated blood into the aorta and through the entire systemic circuit
- two large papillary muscles attach to the
Pulmonary Circuit
- consists of right atrium, right ventricle, pulmonary arteries and veins
- blood travels to lungs via pulmonary arteries
-unloads co2 and replenishes o2 levels in blood before returning to the left atrium via pulmonary veins
-this o2 rich blood has now e
Systemic Circuit
-consists of left atrium and ventricle along with all other named blood vessels
- oxygenated blood from left venticle is pumped into the aorta, the largest systemic artery in the body, and then into smaller systemic arteries
- gas exchange in tissues occu
cardiac cycle
-period of time from start of one heartbeat to the initiation of the next
- all chambers within the heart experience alternate periods of contraction and relaxation
Systole
-contraction of a heart chamber
- forces blood into another chamber (from atrium to ventricle) or into a blood vessel (from a ventricle into the attached large artery)
Diastole
-relaxation phase of a heart chamber
- myocardium of each chamber relaxes between contraction phases, and the chamber fills with blood
Average heartbeat
60-90 times per minute
infants: 90-140 contractions per minute
Innervation
- heart is innervated by the ANS
- both sympathetic and parasympathetic components reach the heart through the coronary plexus
- this innervation by ANS centers in hindbrain doesn't initiate the heartbeat, but it can increase/decrease heartbeat
Sympathetic innervation
increases the rate and the force of the heart contractions
parasympathetic innervation
decreases heart rate, but tends to have no effect on force of contractions, except in special circumstances
Coronary Arteries
-left and right coronary arteries originate superior to the aortic semilunar valve
- travel in coronary sulcus (atrioventricular groove) of heart to supply the heart wall
- right coronary artery typically branches into the:
* marginal artery and posterior
Marginal Artery
supplies the right border of the heart
Posterior Interventricular Artery
supplies both the left and right ventricles
Anterior Interventricular Artery
(aka left anterior descending artery)
supplies the anterior surface of both ventricles and most of the interventricular septum
Circumflex Artery
supplies the left atrium and ventricle
often anastomosis between?
LAD (anterior interventricular artery or left anterior descending artery) and posterior interventricular artery
small, middle, and great cardiac veins
- venous return from cardiac muscle via small, middle, and great cardiac veins
- great cardiac vein becomes the coronary sinus prior to entering the right atrium
Coronary Sinus
all deoxygenated drain and converge here and are sent back for oxygen