The HeartCardiovascular System - 3

for student copy

Position of the Heart• human heart is about the size of a

fist• lies in the thoracic cavity w/in the

mediastinum (area from sternum to vertebrae, between the lungs)

• tilted @ angle so its inferior surface lies against the diaphragm

Parts of the Heart• Base of the heart is

its superior border• Apex of the heart is

lowest point

Major Heart Structures:the Pericardium

• Outer Layer: Fibrous Pericardium– tough, attaches to diaphragm

• Inner Layer: Serous Pericardium– dbl membrane: • outer parietal: attaches to fibrous

pericardium • inner visceral layer: covers cardiac muscle

– between the 2: pericardial cavity filled with serous fluid

Wall of the Heart• 3 layers1. outer epicardium– same as visceral pericardium

2. middle myocardium– cardiac muscle

3. inner endocardium– thin layer of endothelium that lines

inside chambers of the heart & valves

Surface Features of the Heart• 4 chambers of heart:– 2 atria form the base

• Auricles (ear-like) pouch-like extensions – tip of left ventricle forms the apex– Sulci: grooves where coronary blood

vessels & adipose tissue that externally mark the boundaries between the 4 heart chambers• coronary sulcus: separates atria from

ventricles• anterior & posterior interventricular sulcus:

separate 2 ventricles

Right Atrium• Receives

deoxygenated blood from SVC & IVC

Right Atrium• inside surface has honeycombed

appearance & ridges called pectinate muscles

• wall separating rt & lt atrium= interatrial septum: in fetus hole called foramen ovale (blood shunts from rt atrium lt atrium avoiding pulmonary circulation); when scarred over called fossa ovalis

Right Ventricle• receives blood

from right atrium • sends blood to

pulmonary trunk lungs to be oxygenated

Right Ventricle• inside has ridges of

muscles called trabeculae carnae: largest ones called papillary muscles: have string-like cords called cordae tendinae

Right Ventricle• separated from left ventricle by:

interventricular septum

Left Atrium• receives

oxygenated blood thru 4 pulmonary veins

• delivers blood to left ventricle

• seen on posterior surface of heart

Left Atrium• thin-walled• identifiable characteristic: 4

pulmonary veins entering it

Left Ventricle• receives oxygenated blood from left

atrium• sends blood to systemic circulation

thru Aorta• has thickest muscle (pumps blood

the farthest)

4 Heart Valves• control 1-way flow of blood • 2 AV valves– between atria & ventricles– Tricuspid : rt AV valve–Mitral : lt AV valve, aka bicuspid

• 2 semilunar valves– blood exits rt ventricle thru

Pulmonary (semilunar) valve– blood exits lt ventricle thru Aortic

(semilunar) valve

AV Valves• Tricuspid valve • Mitral Valve

Semilunar Valves• Pulmonary Valve • Aortic Valve

Blood Flow thru the Heart• thinner walled atria receive blood

returning to heart from veins• pressure of blood in filled atria opens

the AV valves & most of the blood flows into ventricles

• both atria contract simultaneously to pump remaining blood into ventricles

Blood Flow thru the Heart• when atria have stopped contracting

AV valves close• Ventricles contract together forcing

semilunar valves open• walls of left ventricle thicker

providing more force to pump blood thru systemic circulation

Blood Flow thru the Heart• Ventricular Systole: – when both ventricles are contracting– AV valves close– Semilunar valves open

• Ventricular Diastole: – when both ventricles relaxed– Semilunar valves close– AV valves open

Cardiac Cycle

Systemic & Pulmonary Circulation

Heart Sounds• Auscultation: listening to body

sounds• 1 heartbeat produces 2 heart sounds:

lub-dub• heart murmurs: abnl heart sounds

usually due to valve abnl

• http://www.blaufuss.org/tutorial/index1.html

Pulse• when ventricles contract a blood

pressure wave is produced that travels in the arteries and can be felt as your pulse

• radial pulse: check over radial artery• carotid artery pulse: check over

carotid artery

Calculate Pulse• Count the # of beats in 15 s and

multiply x 4• If the math is too difficult count for

30 s and multiple x 2

Blood Pressure• pressure exerted by blood against

blood vessel walls • highest in the aorta & large elastic

arteries & decreases as arteries get smaller & further from heart

Systolic Blood Pressure• top # on a BP• pressure generated by ventricular

systole• normal adult: ~120

Diastolic BP• bottom # on BP• pressure exerted during ventricular

diastole• normal adult: 60- 80

Arterial Blood Pressure• normal adult ~ 120/80

• normal venous BP: ~16 mm Hg

BP• pump used to inflate cuff to a

pressure > the systolic pressure:– puts pressure on the artery, flattens it, &

stops blood flow in the artery– pressure slowly released from cuff as

stethoscope used to auscultate over brachial artery

BP• reported in mm Hg• as pressure in cuff becomes <

pressure in artery…examiner will hear a sound can be heard, caused by the turbulent flow of blood as artery goes from flattened normal